This Page provides Nervous System Veterinary Physiology multiple-choice questions (MCQs). These MCQs are designed to help veterinary students master the fundamental principles of nervous system physiology by testing their understanding of how neurons and synapses function. You can use these questions and answers to solidify your knowledge, prepare for exams, and build confidence in applying nervous system physiology concepts to veterinary practice as well as it comes with great explanation below each question.
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Introduction to the Nervous System MCQs
1 What is the major functional unit of the nervous system?
A) Glial cell ✖
B) Dendrite ✖
C) Neuron ✔
D) Axon ✖
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The neuron is the primary functional unit of the nervous system, responsible for receiving, processing, and transmitting information through electrical and chemical signals. It consists of dendrites (which receive information), a cell body (soma), an axon (which transmits information), and presynaptic terminals (which communicate with other neurons or target cells).
2 The mammalian nervous system is divided into which two main subdivisions?
A) Somatic Nervous System and Autonomic Nervous System ✖
B) Central Nervous System and Peripheral Nervous System ✔
C) Sympathetic Nervous System and Parasympathetic Nervous System ✖
D) Brain and Spinal Cord ✖
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The nervous system is divided into the Central Nervous System (CNS), comprising the brain and spinal cord, and the Peripheral Nervous System (PNS), which includes all the nerves outside the CNS. The CNS processes and integrates information, while the PNS connects the CNS to the rest of the body, facilitating sensory and motor functions.
3 Which of the following structures are part of the Central Nervous System (CNS)?
A) Spinal nerves and cranial nerves ✖
B) Brain and spinal cord ✔
C) Muscles and glands ✖
D) Sensory receptors and effectors ✖
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The Central Nervous System (CNS) consists solely of the brain and spinal cord. These structures are responsible for processing and integrating information, as well as coordinating and influencing the activity of all parts of the body.
The CNS is protected by three layers of membranes known as meninges: the pia mater (innermost layer directly covering the brain and spinal cord), the arachnoid mater (middle layer with a spider web-like appearance), and the dura mater (outermost, tough layer). These layers provide structural support and protect the CNS from physical damage.
5 What fluid cushions the brain and spinal cord within the vertebral canal?
A) Cerebrospinal fluid ✔
B) Blood plasma ✖
C) Interstitial fluid ✖
D) Synovial fluid ✖
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Cerebrospinal fluid (CSF) is a clear, colorless fluid that surrounds the brain and spinal cord, providing cushioning against mechanical shocks. It also plays a role in nutrient transport, waste removal, and maintaining the chemical environment necessary for neuronal function.
6 Which subdivision of the Peripheral Nervous System is responsible for involuntary functions such as heart rate and digestion?
A) Somatic Nervous System ✖
B) Autonomic Nervous System ✔
C) Sensory Nervous System ✖
D) Motor Nervous System ✖
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The Autonomic Nervous System (ANS) controls involuntary bodily functions, including heart rate, digestion, respiratory rate, and glandular activity. It operates automatically without conscious control and is further divided into the sympathetic and parasympathetic systems, which work together to maintain homeostasis.
7 How many major anatomical regions can the Central Nervous System be divided into?
A) Four ✖
B) Five ✖
C) Six ✔
D) Seven ✖
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The Central Nervous System is divided into six major anatomical regions: the spinal cord, medulla, pons, midbrain, diencephalon, and telencephalon (cerebral hemispheres). Each region has distinct structures and functions, contributing to the overall operation of the nervous system.
8 Which part of the brain is primarily involved in regulating physiological and behavioral aspects of homeostasis?
A) Thalamus ✖
B) Hypothalamus ✔
C) Hippocampus ✖
D) Cerebellum ✖
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The hypothalamus plays a crucial role in maintaining homeostasis by regulating the autonomic nervous system and endocrine system. It controls body temperature, hunger, thirst, fatigue, sleep, and circadian rhythms, as well as hormone secretion from the pituitary gland.
9 What is the primary function of the thalamus within the Central Nervous System?
A) Regulating heart rate and blood pressure ✖
B) Coordinating voluntary motor movements ✖
C) Acting as a relay station for sensory information ✔
D) Controlling memory and spatial learning ✖
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The thalamus serves as the main relay center for sensory information traveling to the cerebral cortex. It processes and transmits sensory signals (except for olfaction) from the body and the external environment to the appropriate cortical areas for further interpretation and response.
10 Which type of neurons carry action potentials away from the Central Nervous System to muscles and glands?
A) Afferent neurons ✖
B) Efferent neurons ✔
C) Interneurons ✖
D) Sensory neurons ✖
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Efferent neurons, also known as motor neurons, carry action potentials away from the CNS to muscles and glands, facilitating motor responses and glandular secretions. They are responsible for executing the commands formulated by the CNS.
11 What distinguishes afferent neurons from efferent neurons in the Peripheral Nervous System?
A) Afferent neurons carry signals away from the CNS, while efferent neurons carry signals toward the CNS. ✖
B) Afferent neurons carry sensory signals toward the CNS, while efferent neurons carry motor signals away from the CNS. ✔
C) Afferent neurons are only found in the spinal cord, while efferent neurons are found in the brain. ✖
D) Afferent neurons produce myelin, while efferent neurons do not. ✖
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Afferent neurons (sensory neurons) transmit sensory information from peripheral receptors to the CNS for processing. Efferent neurons (motor neurons) carry motor commands from the CNS to effector organs such as muscles and glands, facilitating appropriate responses.
12 Which of the following best describes the function of glial cells in the nervous system?
A) Transmitting electrical impulses between neurons ✖
B) Supporting and insulating neurons ✔
C) Generating action potentials ✖
D) Releasing neurotransmitters ✖
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Glial cells provide structural and functional support to neurons. They maintain the extracellular environment, form myelin sheaths around axons to insulate them and speed up signal transmission, assist in nutrient transport, and play roles in immune responses within the CNS. Unlike neurons, glial cells do not transmit electrical impulses.
13 What is the primary difference between oligodendrocytes and Schwann cells?
A) Oligodendrocytes myelinate axons in the CNS, while Schwann cells myelinate axons in the PNS. ✔
B) Oligodendrocytes produce neurotransmitters, while Schwann cells do not. ✖
C) Oligodendrocytes are found in the PNS, while Schwann cells are found in the CNS. ✖
D) There is no difference; they are two names for the same cells. ✖
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Oligodendrocytes are glial cells in the Central Nervous System that form myelin sheaths around multiple axons. Schwann cells, on the other hand, are glial cells in the Peripheral Nervous System that myelinate individual axons. This distinction is crucial for understanding how myelination differs between the CNS and PNS.
14 Which anatomical region of the CNS is responsible for coordinating voluntary movements and maintaining balance?
A) Telencephalon ✖
B) Cerebellum ✔
C) Diencephalon ✖
D) Medulla ✖
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The cerebellum is essential for coordinating voluntary movements, maintaining balance, and ensuring smooth and precise motor activities. It receives input from sensory systems and other parts of the brain to fine-tune motor commands, making it critical for activities requiring coordination and timing.
15 What is the role of the spinal cord within the Central Nervous System?
A) Processing higher cognitive functions ✖
B) Coordinating reflexes and transmitting signals between the brain and the body ✔
C) Regulating hormone secretion ✖
D) Storing long-term memories ✖
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The spinal cord acts as a conduit for transmitting sensory information from the body to the brain and motor commands from the brain to the muscles and glands. It also coordinates simple reflexes independently of the brain, allowing for rapid responses to certain stimuli without conscious thought.
16 Which layer of the meninges is directly attached to the surface of the brain and spinal cord?
A) Dura mater ✖
B) Arachnoid mater ✖
C) Pia mater ✔
D) Periosteum ✖
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The pia mater is the innermost layer of the meninges, directly adhering to the surface of the brain and spinal cord. It is a thin, delicate membrane that follows the contours of the CNS, providing a protective barrier and assisting in the circulation of cerebrospinal fluid.
17 How does the Peripheral Nervous System differ from the Central Nervous System in terms of regenerative ability?
A) Both CNS and PNS axons regenerate equally well after injury ✖
B) CNS axons regenerate easily, while PNS axons do not ✖
C) PNS axons can regenerate and reconnect to their targets, whereas CNS axons do not regenerate effectively ✔
D) Neither CNS nor PNS axons have the ability to regenerate after injury ✖
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Peripheral Nervous System (PNS) axons have the capacity to regenerate and reconnect with their target tissues after injury, largely due to the supportive environment provided by Schwann cells. In contrast, Central Nervous System (CNS) axons do not regenerate effectively due to inhibitory factors, including glial scarring and molecules released by oligodendrocytes.
18 What are neural circuits or pathways, and how are they organized within the nervous system?
A) Isolated neurons functioning independently ✖
B) Groups of interconnected neurons performing specific functions ✔
C) Chains of muscle cells controlled by single neurons ✖
D) Layers of glial cells supporting neuron structure ✖
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Neural circuits or pathways consist of groups of interconnected neurons that work together to perform specific functions, such as reflex actions, sensory processing, or motor control. These circuits integrate and process information, enabling coordinated responses and complex behaviors.
19 Which of the following best describes the function of the reticular formation in the brainstem?
A) Processing visual information ✖
B) Coordinating voluntary muscle movements ✖
C) Modulating consciousness, arousal, and pain perception ✔
D) Regulating hormone secretion ✖
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The reticular formation is a network of interconnected nuclei located within the brainstem. It plays a key role in regulating consciousness, arousal, sleep-wake cycles, pain perception, and certain reflexes. This system integrates sensory and motor information, helping maintain alertness and attention.
20 What is the primary role of the blood-brain barrier in maintaining CNS homeostasis?
A) Facilitating the free exchange of substances between blood and brain ✖
B) Preventing the entry of most pathogens and toxins into the brain ✔
C) Allowing all nutrients to pass freely into the brain ✖
D) Regulating cerebrospinal fluid production ✖
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The blood-brain barrier is a selective permeability barrier formed by tight junctions between endothelial cells in CNS blood vessels. Its primary role is to protect the brain by preventing most pathogens, toxins, and large or hydrophilic molecules from entering the CNS, while still allowing essential nutrients like glucose and amino acids to pass through.
21 Which of the following statements accurately describes the difference between neural systems and neural circuits?
A) Neural circuits are larger networks, while neural systems are individual pathways ✖
B) Neural circuits refer to interconnected neurons for specific functions, while neural systems are collections of related circuits ✔
C) Neural systems operate within the CNS, while neural circuits operate within the PNS ✖
D) There is no difference; they are interchangeable terms ✖
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Neural circuits are specific pathways of interconnected neurons that carry out particular functions, such as the retinotectal pathway for visual reflexes. Neural systems are broader collections of related neural circuits that work together to perform complex tasks, such as the entire visual system encompassing multiple neural circuits involved in processing visual information.
22 What clinical condition in horses is associated with diffuse neuronal degeneration of the white matter in the medulla and spinal cord?
A) Equine degenerative myeloencephalopathy ✔
B) Coonhound paralysis ✖
C) Degenerative myelopathy ✖
D) Salt toxicity ✖
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Equine degenerative myeloencephalopathy is characterized by diffuse neuronal degeneration in the white matter of the medulla and spinal cord, along with astrocytosis and demyelination. It is associated with factors such as low dietary vitamin E, exposure to insecticides, and other environmental toxins. Clinically, affected horses exhibit abnormal movement, weakness, and incoordination.
23 Which of the following brain regions is involved in processing and relaying visual and auditory information?
A) Medulla ✖
B) Midbrain ✔
C) Pons ✖
D) Diencephalon ✖
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The midbrain, or mesencephalon, contains structures like the superior and inferior colliculi, which are responsible for processing and relaying visual and auditory information, respectively. It also houses cranial nerve nuclei involved in eye movements and pupillary responses.
24 What is the significance of the nodes of Ranvier in myelinated axons?
A) They produce neurotransmitters for synaptic transmission ✖
B) They are the sites where action potentials are generated in myelinated axons ✔
C) They store calcium ions for neurotransmitter release ✖
D) They facilitate the production of cerebrospinal fluid ✖
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Nodes of Ranvier are gaps in the myelin sheath along myelinated axons. These nodes contain a high density of voltage-gated sodium channels, which are crucial for the generation of action potentials. In myelinated axons, action potentials jump from node to node (saltatory conduction), significantly increasing the speed of signal transmission compared to unmyelinated axons.
25 Which clinical sign is NOT typically associated with equine degenerative myeloencephalopathy?
A) Weakness in limbs ✖
B) Ataxia ✖
C) Blindness ✔
D) Seizures ✖
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Equine degenerative myeloencephalopathy primarily affects motor functions, leading to weakness, ataxia (incoordination), and abnormal movements such as stumbling or falling. While seizures can occur, blindness is not a typical clinical sign associated with this condition. Blindness may be associated with other neurological disorders affecting the visual pathways.
26 What role do astrocytes play in the Central Nervous System?
A) They conduct electrical impulses between neurons ✖
B) They form myelin sheaths around axons ✖
C) They maintain the extracellular ion balance and support the blood-brain barrier ✔
D) They release neurotransmitters into the synaptic cleft ✖
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Astrocytes are a type of glial cell in the CNS that perform several vital functions, including maintaining the extracellular ion balance, regulating neurotransmitter levels, supporting the blood-brain barrier, and providing metabolic support to neurons. They do not conduct electrical impulses or form myelin sheaths; these roles are fulfilled by neurons and oligodendrocytes, respectively.
27 How does the autonomic nervous system influence pharmacology?
A) It is unrelated to pharmacological processes ✖
B) Understanding the ANS is essential for developing drugs that affect involuntary functions ✔
C) The ANS only affects muscle contractions, not pharmacological actions ✖
D) Pharmacology only targets the Central Nervous System, not the ANS ✖
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The autonomic nervous system (ANS) regulates involuntary bodily functions such as heart rate, digestion, and respiratory rate. Many pharmacological agents target the ANS to modify these functions, either by stimulating or inhibiting specific receptors within the sympathetic or parasympathetic branches. A thorough understanding of the ANS is crucial for developing effective and safe drugs that influence these involuntary processes.
28 What clinical sign would most likely indicate a problem with the cerebellum?
A) Memory loss ✖
B) Difficulty with balance and coordination ✔
C) Increased heart rate ✖
D) Impaired vision ✖
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The cerebellum is primarily responsible for coordinating voluntary movements, maintaining balance, and ensuring smooth and precise motor activities. Dysfunction in the cerebellum typically manifests as ataxia (lack of coordination), tremors, and difficulty maintaining balance, rather than issues like memory loss or impaired vision, which are associated with other brain regions.
29 What is the function of the retinotectal pathway within the visual system?
A) Relaying information for reflex orientation of the eyes to light sources ✔
B) Processing color and detailed visual information ✖
C) Storing long-term visual memories ✖
D) Coordinating eye movements with motor responses ✖
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The retinotectal pathway is involved in the reflexive orientation of the eyes toward light sources. It processes basic visual information, allowing for rapid, automatic responses to changes in the visual environment, such as turning the eyes toward a sudden light stimulus.
30 In the context of the nervous system, what is homeostasis?
A) The ability to generate new neurons ✖
B) The process of nerve signal transmission ✖
C) The maintenance of a stable internal environment ✔
D) The growth of neural circuits ✖
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Homeostasis refers to the nervous system’s ability to maintain a stable and balanced internal environment despite external changes. This involves regulating various physiological parameters such as temperature, pH, electrolyte balance, and blood pressure to ensure optimal functioning of cells and organs.
31 What is the primary source of energy for the Na+, K+ pump in neurons?
A) Glucose ✖
B) Adenosine triphosphate (ATP) ✔
C) Oxygen ✖
D) Lactic acid ✖
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The Na+, K+ pump, which maintains the resting membrane potential by actively transporting sodium out of and potassium into the neuron, primarily relies on energy derived from Adenosine triphosphate (ATP). ATP provides the necessary energy for the pump to function against the concentration gradients of Na+ and K+ ions.
32 What is an action potential and where does it typically begin in a neuron?
A) A chemical signal released at the synapse; it begins in the presynaptic terminal ✖
B) A large, rapid change in membrane potential; it begins at the axon hillock ✔
C) A small, gradual change in membrane potential; it begins in the dendrites ✖
D) The process of neurotransmitter reuptake; it begins in the synaptic cleft ✖
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An action potential is a rapid and large change in the neuron’s membrane potential that propagates along the axon. It typically begins at the axon hillock (initial segment) where the integration of excitatory and inhibitory postsynaptic potentials can trigger the threshold needed to initiate the action potential.
33 How do myelinated axons achieve faster conduction of action potentials compared to unmyelinated axons?
A) By having a larger diameter ✖
B) Through continuous signal transmission along the entire axon ✖
C) By allowing action potentials to jump between nodes of Ranvier ✔
D) By increasing the number of neurotransmitters released ✖
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Myelinated axons achieve faster conduction through saltatory conduction, where action potentials jump from one node of Ranvier to the next. The myelin sheath insulates segments of the axon, preventing ion leakage and allowing the electrical signal to travel rapidly between nodes, significantly increasing conduction velocity compared to unmyelinated axons where the action potential must travel continuously along the entire membrane.
34 What mechanism ensures that action potentials travel in one direction along an axon?
A) Saltatory conduction ✖
B) Refractory periods ✔
C) Chemical synapses ✖
D) Myelination ✖
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Refractory periods prevent action potentials from traveling backward along the axon, ensuring that they move in one direction—from the axon hillock to the axon terminals—by temporarily inactivating sodium channels right after an action potential occurs.
35 What is the role of the medulla oblongata within the brainstem?
A) It coordinates voluntary motor movements ✖
B) It processes complex cognitive functions ✖
C) It regulates vital functions such as breathing, heart rate, and blood pressure ✔
D) It serves as the primary region for memory formation ✖
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The medulla oblongata is part of the brainstem and plays a crucial role in regulating vital autonomic functions like heart rate, breathing, and blood pressure. It also contains centers that control reflexes like swallowing and coughing, ensuring basic life support functions continue without conscious control.
36 What is the primary function of the cerebral cortex in the telencephalon?
A) Reflex coordination and motor learning ✖
B) Regulation of vital reflexes like heartbeat and breathing ✖
C) Higher-order processing, including sensory perception, voluntary movement, and decision-making ✔
D) Regulation of hormonal secretion from the pituitary gland ✖
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The cerebral cortex is the outer layer of the telencephalon and is responsible for the most complex and sophisticated functions of the brain, including sensory perception, voluntary movement, decision-making, problem-solving, and higher cognitive abilities like memory and reasoning.
38 What is the primary role of the hypothalamus in the diencephalon?
A) It relays sensory information to the cerebral cortex ✖
B) It regulates autonomic functions and controls hormone secretion from the pituitary gland ✔
C) It coordinates voluntary motor control ✖
D) It processes auditory and visual information ✖
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The hypothalamus is a vital regulatory center in the brain that controls autonomic functions such as body temperature, hunger, and thirst. It also regulates the release of hormones from the pituitary gland, influencing processes like growth, metabolism, and reproductive functions.
39 The pons plays an important role in which of the following?
A) Coordinating balance and posture ✖
B) Transmitting information from the cerebral cortex to the cerebellum ✔
C) Processing olfactory and gustatory information ✖
D) Regulating hormonal balance ✖
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The pons serves as a bridge between the cerebral cortex and the cerebellum, transmitting motor commands to help coordinate movements. It also contains nuclei that are involved in regulating respiration, sleep, and facial sensations.
40 What type of neurotransmitter is primarily inhibitory in the central nervous system?
A) Glutamate ✖
B) Acetylcholine ✖
C) GABA ✔
D) Dopamine ✖
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Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system, playing a key role in reducing neuronal excitability and preventing excessive firing.
A) A complex pathway that involves the brain in every response ✖
B) A neural pathway that mediates a reflex action, usually involving only the spinal cord ✔
C) A type of voluntary response mediated by the cerebral cortex ✖
D) A sequence of actions that requires conscious thought ✖
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A reflex arc is a simple neural pathway that enables a reflex action. It typically involves sensory neurons that synapse with motor neurons in the spinal cord, allowing for rapid responses without the involvement of higher brain centers.
42 Which structure connects the brain to the spinal cord?
A) Cerebellum ✖
B) Medulla oblongata ✔
C) Thalamus ✖
D) Pons ✖
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The medulla oblongata is a part of the brainstem that connects the brain to the spinal cord and is responsible for regulating vital functions such as breathing, heart rate, and blood pressure.
43 What mechanism do inhibitory neurotransmitters typically use to affect the postsynaptic neuron?
A) They cause depolarization of the postsynaptic membrane ✖
B) They prevent neurotransmitter release from the presynaptic neuron ✖
C) They increase the permeability of the postsynaptic membrane to sodium ions ✖
D) They open channels that allow chloride ions to enter the postsynaptic neuron ✔
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Inhibitory neurotransmitters (like GABA) typically cause hyperpolarization of the postsynaptic membrane by opening channels that allow chloride ions (Cl-) to enter the neuron, making it less likely to generate an action potential.
44 Which of the following best describes the role of microglia in the central nervous system?
A) They provide structural support to neurons ✖
B) They produce myelin ✖
C) They act as immune cells that respond to injury or infection ✔
D) They release neurotransmitters ✖
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Microglia are the resident immune cells of the central nervous system, responsible for monitoring the environment, responding to injury, and clearing away debris and pathogens.
45 Which of the following structures is NOT part of the brainstem?
A) Midbrain ✖
B) Pons ✖
C) Medulla oblongata ✖
D) Cerebellum ✔
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The cerebellum is a separate structure from the brainstem and is primarily involved in coordination and balance. The brainstem consists of the midbrain, pons, and medulla oblongata.
46 What is the primary purpose of the sympathetic division of the autonomic nervous system?
A) To promote rest and digestion ✖
B) To prepare the body for “fight or flight” responses ✔
C) To facilitate communication between sensory and motor neurons ✖
D) To regulate voluntary muscle movements ✖
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The sympathetic division of the autonomic nervous system prepares the body for rapid responses to stressful situations, increasing heart rate, blood flow to muscles, and energy availability for immediate action.
47 What process allows the brain to adjust to new experiences and learn over time?
A) Neurogenesis ✖
B) Neuroplasticity ✔
C) Synaptic cleft formation ✖
D) Myelination ✖
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Neuroplasticity refers to the brain’s ability to adapt and reorganize itself by forming new neural connections in response to learning, experience, or injury.
48 Which type of neuron connects sensory and motor neurons within the central nervous system?
A) Afferent neurons ✖
B) Efferent neurons ✖
C) Interneurons ✔
D) Motor neurons ✖
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Interneurons are neurons that connect sensory neurons to motor neurons within the central nervous system. They play a crucial role in processing information and coordinating responses.
B) To secrete melatonin and regulate circadian rhythms ✔
C) To facilitate neurotransmission ✖
D) To maintain body temperature ✖
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The pineal gland produces melatonin, a hormone that helps regulate sleep-wake cycles and circadian rhythms, influencing sleep patterns and overall biological rhythms.
50 What happens during the repolarization phase of an action potential?
A) Sodium ions enter the neuron ✖
B) Potassium ions leave the neuron, restoring the negative internal charge ✔
C) The neuron is unable to respond to any stimuli ✖
D) Calcium ions are released into the synapse ✖
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During repolarization, voltage-gated potassium channels open, allowing potassium ions (K+) to flow out of the neuron, which helps return the membrane potential to a negative state after depolarization.
52 What occurs during the absolute refractory period of a neuron?
A) The neuron can fire another action potential if stimulated. ✖
B) The neuron cannot fire another action potential regardless of the stimulus strength. ✔
C) The neuron is preparing to return to its resting potential. ✖
D) The neuron is releasing neurotransmitters. ✖
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During the absolute refractory period, the voltage-gated sodium channels are inactivated after an action potential, making it impossible for the neuron to fire another action potential.
53 Which neurotransmitter is primarily associated with mood regulation?
A) Dopamine ✖
B) Acetylcholine ✖
C) Norepinephrine ✖
D) Serotonin ✔
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Serotonin is a neurotransmitter that plays a crucial role in mood regulation, and its imbalance is often associated with mood disorders like depression.
54 Which brain structure is primarily involved in memory formation?
A) Thalamus ✖
B) Hippocampus ✔
C) Cerebellum ✖
D) Medulla oblongata ✖
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The hippocampus is a critical brain region involved in the formation of new memories and learning, playing an essential role in spatial navigation and the consolidation of information from short-term to long-term memory.
55 How do action potentials propagate along an unmyelinated axon?
A) By jumping from node to node ✖
B) By continuously depolarizing adjacent segments of the membrane ✔
C) By sending signals through the myelin sheath ✖
D) By synapsing with other neurons ✖
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In unmyelinated axons, action potentials propagate by continuously depolarizing adjacent segments of the membrane, leading to sequential opening of voltage-gated sodium channels along the axon.
56 What is the role of the choroid plexus in the brain?
A) To regulate the blood-brain barrier ✖
B) To produce cerebrospinal fluid (CSF) ✔
C) To facilitate neurotransmitter release ✖
D) To connect the two hemispheres of the brain ✖
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The choroid plexus is a structure within the ventricles of the brain that produces cerebrospinal fluid (CSF), which cushions the brain and provides nutrients.
57 What is the main effect of the parasympathetic nervous system?
A) To prepare the body for physical activity ✖
B) To promote relaxation and conserve energy ✔
C) To increase heart rate and blood pressure ✖
D) To enhance the “fight or flight” response ✖
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The parasympathetic nervous system is responsible for promoting a state of rest and digest, conserving energy, and regulating functions such as slowing the heart rate and stimulating digestion.
59 Which structure in the brain is primarily responsible for processing visual information?
A) Occipital lobe ✔
B) Temporal lobe ✖
C) Parietal lobe ✖
D) Frontal lobe ✖
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The occipital lobe is the region of the brain responsible for processing visual information received from the eyes, allowing for perception and interpretation of visual stimuli.
The temporal lobe is involved in processing auditory information and is also important for memory formation, including aspects of language and visual memory.
A typical neuron consists of four main anatomical regions: dendrites (which receive signals), the cell body (soma, which processes information), the axon (which transmits signals), and presynaptic terminals (which communicate with other neurons or target cells). Each part plays a crucial role in the neuron’s function.
62 What is the resting membrane potential of most mammalian neurons?
A) +40 mV ✖
B) -70 mV ✔
C) +70 mV ✖
D) 0 mV ✖
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The resting membrane potential of most mammalian neurons is approximately -70 mV, indicating that the inside of the neuron is negatively charged relative to the outside. This potential is primarily maintained by the differential distribution of ions, particularly sodium (Na+) and potassium (K+), across the neuronal membrane.
63 What is the primary function of the myelin sheath?
A) To produce neurotransmitters ✖
B) To insulate axons and increase the speed of action potentials ✔
C) To provide structural support to neurons ✖
D) To connect neurons to muscles ✖
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The myelin sheath, formed by glial cells (Schwann cells in the PNS and oligodendrocytes in the CNS), insulates axons, which significantly increases the speed of action potentials through a process called saltatory conduction. This allows electrical impulses to jump from node to node (nodes of Ranvier), speeding up signal transmission along the axon.
64 How is an action potential initiated in a neuron?
A) By the influx of potassium ions ✖
B) By the influx of sodium ions when the membrane depolarizes to threshold ✔
C) By the release of neurotransmitters ✖
D) By the outflow of calcium ions ✖
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An action potential is initiated when the membrane potential of a neuron depolarizes to a threshold level, typically around -55 mV. This depolarization occurs primarily due to the influx of sodium ions (Na+) through voltage-gated sodium channels, resulting in a rapid change in membrane potential.
65 Which type of signal decreases the likelihood of an action potential in a postsynaptic neuron?
A) Excitatory postsynaptic potential (EPSP) ✖
B) Inhibitory postsynaptic potential (IPSP) ✔
C) Action potential ✖
D) Resting membrane potential ✖
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An inhibitory postsynaptic potential (IPSP) occurs when the membrane potential of the postsynaptic neuron becomes more negative (hyperpolarized) due to the influx of chloride ions (Cl-) or the efflux of potassium ions (K+). This hyperpolarization decreases the likelihood of reaching the threshold for action potential initiation.
66 What is the role of neurotransmitters in synaptic transmission?
A) They transmit electrical signals directly across the synapse. ✖
B) They facilitate the conversion of action potentials into muscle contractions. ✖
C) They bind to receptors on the postsynaptic cell to initiate a response. ✔
D) They generate action potentials in the presynaptic neuron. ✖
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Neurotransmitters are chemical messengers released from presynaptic terminals into the synaptic cleft. They bind to specific receptors on the postsynaptic cell, leading to changes in membrane potential and initiating either excitatory or inhibitory responses in the postsynaptic neuron.
67 What occurs during the depolarization phase of an action potential?
A) Sodium channels close, and potassium channels open. ✖
B) Potassium ions exit the neuron, causing hyperpolarization. ✖
C) Sodium ions rapidly enter the neuron, causing the membrane potential to become more positive. ✔
D) The neuron returns to its resting potential. ✖
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During the depolarization phase of an action potential, voltage-gated sodium channels open, allowing sodium ions (Na+) to flow into the neuron. This influx of positive ions makes the inside of the neuron more positive, leading to a rapid rise in membrane potential.
68 What is the significance of the nodes of Ranvier in myelinated axons?
A) They prevent action potentials from occurring. ✖
B) They facilitate faster propagation of action potentials through saltatory conduction. ✔
C) They serve as synapses between neurons. ✖
D) They produce neurotransmitters. ✖
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The nodes of Ranvier are gaps in the myelin sheath where voltage-gated sodium channels are concentrated. These nodes allow action potentials to jump from one node to the next, significantly increasing the speed of signal transmission in myelinated axons through a process known as saltatory conduction.
69 Which of the following accurately describes the action potential?
A) It is a graded response that varies in magnitude. ✖
B) It occurs when the membrane potential reaches a threshold and propagates along the axon without decrement. ✔
C) It is generated solely by potassium ion movement. ✖
D) It only occurs in the dendrites of the neuron. ✖
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An action potential is an all-or-nothing response that occurs when a neuron’s membrane potential reaches a threshold level. Once initiated, it propagates along the axon without decrement, meaning the amplitude remains consistent as it travels down the length of the axon.
A) To facilitate the transfer of electrical signals between neurons ✖
B) To allow the diffusion of neurotransmitters from the presynaptic to the postsynaptic neuron ✔
C) To house voltage-gated ion channels ✖
D) To connect sensory receptors to the CNS ✖
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The synaptic cleft is the small gap between the presynaptic and postsynaptic neurons where neurotransmitters diffuse after being released from the presynaptic terminal. This diffusion is crucial for synaptic transmission, enabling communication between neurons.
71 What is the primary mechanism for repolarization during an action potential?
A) Influx of sodium ions ✖
B) Efflux of potassium ions ✔
C) Active transport of calcium ions ✖
D) Opening of chloride channels ✖
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Incorrect! The correct answer is shown in green.
Repolarization during an action potential occurs primarily due to the efflux of potassium ions (K+) from the neuron. After the peak of the action potential, voltage-gated potassium channels open, allowing K+ to exit the cell, which helps return the membrane potential to its resting state.
72 What type of neurotransmitter is primarily involved in excitatory postsynaptic potentials (EPSPs)?
A) Gamma-aminobutyric acid (GABA) ✖
B) Acetylcholine (ACh) ✔
C) Dopamine ✖
D) Serotonin ✖
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Acetylcholine (ACh) is a common neurotransmitter involved in creating excitatory postsynaptic potentials (EPSPs) by binding to receptors on the postsynaptic neuron, leading to depolarization and increased likelihood of generating an action potential.
73 What is the role of the axon hillock in a neuron?
A) It receives signals from other neurons. ✖
B) It integrates incoming signals and determines if an action potential will occur. ✔
C) It releases neurotransmitters into the synaptic cleft. ✖
D) It generates the myelin sheath. ✖
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The axon hillock is the region of the neuron where the axon originates from the cell body. It is crucial for integrating signals received from the dendrites and cell body and determining whether the membrane potential reaches the threshold to initiate an action potential.
74 What physiological process allows for the rapid conduction of action potentials along myelinated axons?
A) Continuous conduction ✖
B) Saltatory conduction ✔
C) Passive conduction ✖
D) Regenerative conduction ✖
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Saltatory conduction is the process by which action potentials jump from one node of Ranvier to the next along myelinated axons. This method allows for much faster transmission of electrical signals compared to continuous conduction along unmyelinated axons.
75 How do inhibitory postsynaptic potentials (IPSPs) affect a neuron?
A) They increase the likelihood of an action potential. ✖
B) They decrease the likelihood of an action potential. ✔
C) They have no effect on the neuron. ✖
D) They trigger neurotransmitter release. ✖
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Inhibitory postsynaptic potentials (IPSPs) result in hyperpolarization of the postsynaptic membrane, making it more negative and reducing the likelihood that the neuron will reach the threshold necessary to generate an action potential.
76 Which type of channel opens in response to depolarization during an action potential?
A) Potassium channels ✖
B) Calcium channels ✖
C) Voltage-gated sodium channels ✔
D) Ligand-gated channels ✖
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During the depolarization phase of an action potential, voltage-gated sodium channels open in response to a change in membrane potential, allowing sodium ions to flow into the neuron and causing further depolarization.
77 What is the primary mechanism by which neurotransmitters are removed from the synaptic cleft?
A) Diffusion ✖
B) Reuptake by the presynaptic neuron ✖
C) Enzymatic degradation ✖
D) Both B and C ✔
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Neurotransmitters are removed from the synaptic cleft primarily by reuptake into the presynaptic neuron or by enzymatic degradation. Reuptake is a common mechanism where neurotransmitters are transported back into the presynaptic neuron, while enzymatic degradation involves specific enzymes breaking down neurotransmitters, such as acetylcholinesterase for acetylcholine.
78 Which of the following statements about the resting membrane potential is TRUE?
A) It is primarily determined by the concentration of calcium ions inside the neuron. ✖
B) It remains constant regardless of the state of the neuron. ✖
C) It is created by the unequal distribution of ions, particularly sodium and potassium, across the membrane. ✔
D) It is the same for all cell types in the body. ✖
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The resting membrane potential is established by the differential distribution of ions, primarily sodium (Na+) and potassium (K+), across the neuronal membrane. The sodium-potassium pump plays a key role in maintaining this gradient, which results in a negative charge inside the neuron at rest.
79 In the context of neuron signaling, what is meant by “graded potentials”?
A) Potentials that always lead to action potentials. ✖
B) Changes in membrane potential that vary in size and can be excitatory or inhibitory. ✔
C) A constant potential maintained during resting conditions. ✖
D) Rapid changes in membrane potential that do not vary in size. ✖
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Graded potentials are local changes in membrane potential that vary in magnitude depending on the strength of the stimulus. They can be excitatory (depolarizing) or inhibitory (hyperpolarizing) and are crucial for determining whether an action potential will be generated at the axon hillock.
80 What happens during the hyperpolarization phase of an action potential?
A) The membrane potential becomes more positive than the resting potential. ✖
B) Potassium ions are pumped out of the neuron, making the inside more negative. ✔
C) Sodium channels open, allowing sodium ions to flow into the neuron. ✖
D) The neuron resets to its resting potential. ✖
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During the hyperpolarization phase, voltage-gated potassium channels remain open, allowing potassium ions (K+) to exit the neuron. This outflow makes the inside of the neuron more negative than the resting potential, temporarily increasing the difference in charge across the membrane.
81 Which of the following processes occurs at the presynaptic terminal during neurotransmitter release?
A) Depolarization of the postsynaptic membrane ✖
B) Influx of sodium ions ✖
C) Influx of calcium ions ✔
D) Hyperpolarization of the presynaptic terminal ✖
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When an action potential reaches the presynaptic terminal, it causes voltage-gated calcium channels to open, allowing calcium ions (Ca2+) to flow into the terminal. This influx of calcium triggers the release of neurotransmitters from synaptic vesicles into the synaptic cleft.
82 What determines whether a postsynaptic neuron will fire an action potential?
A) The type of neurotransmitter released ✖
B) The net effect of excitatory and inhibitory postsynaptic potentials ✔
C) The distance from the synapse to the axon hillock ✖
D) The concentration of neurotransmitters in the synaptic cleft ✖
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Whether a postsynaptic neuron fires an action potential depends on the summation of excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) that it receives. If the net effect brings the membrane potential to threshold, an action potential will be generated.
83 What type of synapse is characterized by the release of neurotransmitters?
A) Electrical synapse ✖
B) Chemical synapse ✔
C) Myelinated synapse ✖
D) Reflex synapse ✖
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A chemical synapse is characterized by the release of neurotransmitters from the presynaptic neuron into the synaptic cleft, where they bind to receptors on the postsynaptic neuron. This process allows for complex signaling between neurons.
84 What is the effect of an excitatory neurotransmitter on the postsynaptic neuron?
A) It causes hyperpolarization. ✖
B) It decreases the likelihood of an action potential. ✖
C) It causes depolarization and increases the likelihood of an action potential. ✔
D) It has no effect on the postsynaptic neuron. ✖
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Excitatory neurotransmitters bind to receptors on the postsynaptic neuron, causing depolarization of the membrane. This depolarization increases the likelihood that the neuron will reach the threshold required to generate an action potential.
85 Which of the following is a feature of action potentials?
A) They are graded responses that can vary in strength. ✖
B) They are all-or-nothing events once the threshold is reached. ✔
C) They occur only in the dendrites of a neuron. ✖
D) They always result in the release of neurotransmitters. ✖
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Action potentials are all-or-nothing responses; once the membrane potential reaches a certain threshold, an action potential is generated. The strength of the action potential is consistent and does not vary, unlike graded potentials.
B) The opening of potassium channels and the closure of sodium channels ✔
C) The release of neurotransmitters ✖
D) The return of the membrane potential to resting levels ✖
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The refractory period occurs after an action potential when the voltage-gated sodium channels are inactivated and potassium channels are open, preventing the neuron from firing another action potential for a brief period. This period ensures that action potentials travel in one direction and that the neuron has time to recover.
87 Which of the following statements about neurotransmitter receptors is true?
A) They can only bind one specific type of neurotransmitter. ✖
B) They are only found on presynaptic neurons. ✖
C) They can initiate a response in the postsynaptic neuron upon binding with neurotransmitters. ✔
D) They are located in the synaptic cleft. ✖
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Neurotransmitter receptors are located on the postsynaptic neuron and can initiate various responses (excitatory or inhibitory) when a neurotransmitter binds to them. Each receptor type is specific to particular neurotransmitters, leading to a specific physiological effect.
A) They enhance the release of neurotransmitters. ✖
B) They block sodium channels, preventing action potentials. ✔
C) They increase potassium ion flow into the neuron. ✖
D) They promote synaptic transmission. ✖
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Local anesthetics work by blocking voltage-gated sodium channels in neurons, preventing the influx of sodium ions. This inhibition stops the generation and propagation of action potentials, effectively blocking sensation in the area where the anesthetic is applied.
89 How does the nervous system maintain homeostasis?
A) By generating new neurons continuously ✖
B) By regulating physiological processes through feedback mechanisms ✔
C) By deactivating synaptic transmission ✖
D) By stopping neurotransmitter release in the brain ✖
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Homeostasis is maintained through feedback mechanisms involving the nervous system, which helps regulate body temperature, blood pressure, and other critical physiological processes.
92 What distinguishes sympathetic from parasympathetic responses?
A) Sympathetic responses prepare the body for action, while parasympathetic responses promote rest and digestion. ✔
B) Both systems stimulate the fight-or-flight response ✖
C) The parasympathetic system only activates during sleep ✖
D) Both systems inhibit heart rate during stress ✖
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Sympathetic responses prepare the body for emergencies (e.g., increasing heart rate), while parasympathetic responses help restore the body to a restful state, promoting digestion and energy conservation.
93 Which of the following describes the absolute refractory period?
A) The neuron is at resting potential after an action potential ✖
B) The neuron cannot fire another action potential regardless of stimulus strength ✔
C) The neuron can fire another action potential if stimulated ✖
D) The neuron is preparing to repolarize after a potential ✖
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The absolute refractory period is the time during which a neuron is unable to fire another action potential, regardless of the strength of the incoming stimulus. This occurs because the voltage-gated sodium channels are inactivated after an action potential, preventing further depolarization.
94 Which of the following best describes a neurotransmitter?
A) A chemical messenger that transmits signals across a synapse ✔
B) A protein that facilitates signal transduction ✖
C) A hormone that regulates metabolism ✖
D) An ion that maintains resting potential ✖
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Neurotransmitters are chemicals released from the presynaptic neuron into the synaptic cleft that bind to receptors on the postsynaptic neuron. They play a crucial role in transmitting signals between neurons, influencing various physiological processes.
95 What is the purpose of the synaptic vesicles in the presynaptic neuron?
A) To generate action potentials ✖
B) To store and release neurotransmitters ✔
C) To maintain resting membrane potential ✖
D) To provide structural support ✖
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Synaptic vesicles are membrane-bound structures within the presynaptic neuron that store neurotransmitters. When an action potential reaches the presynaptic terminal, these vesicles fuse with the membrane and release their contents into the synaptic cleft, allowing for signal transmission.
96 Which neurotransmitter is primarily involved in the “fight or flight” response?
A) Serotonin ✖
B) Norepinephrine ✔
C) Acetylcholine ✖
D) Dopamine ✖
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Norepinephrine is a neurotransmitter that plays a key role in the sympathetic nervous system’s response to stress, known as the “fight or flight” response. It increases heart rate, blood flow to muscles, and energy availability, preparing the body for immediate action.
97 What is the role of ligand-gated ion channels in postsynaptic signaling?
A) They transmit action potentials along the axon ✖
B) They generate the resting membrane potential ✖
C) They open in response to neurotransmitter binding, allowing ions to flow across the membrane ✔
D) They facilitate neurotransmitter release from vesicles ✖
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Ligand-gated ion channels are activated when neurotransmitters bind to their specific receptors on the postsynaptic membrane. This binding causes the channels to open, allowing the flow of ions (such as Na+ or Cl-) across the membrane, which can lead to depolarization or hyperpolarization of the postsynaptic neuron.
98 What is the primary role of dendrites in a neuron?
A) To receive and integrate signals from other neurons ✔
B) To release neurotransmitters into the synaptic cleft ✖
C) To maintain the neuron’s resting membrane potential ✖
D) To transmit electrical signals away from the cell body ✖
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Dendrites are the branching structures of a neuron that receive signals from other neurons and transmit this information to the cell body for processing. They play a crucial role in integrating synaptic input and determining the overall response of the neuron.
99 What is the significance of the sodium-potassium pump in maintaining resting membrane potential?
A) It generates electrical impulses along the axon ✖
B) It allows calcium ions to enter the cell ✖
C) It pumps sodium ions out of the neuron and potassium ions into the neuron, creating a concentration gradient ✔
D) It prevents action potentials from occurring ✖
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The sodium-potassium pump is an active transport mechanism that moves three sodium ions (Na+) out of the neuron and two potassium ions (K+) into the neuron, maintaining the concentration gradients essential for the resting membrane potential. This activity helps keep the inside of the neuron negatively charged compared to the outside.
A) The process of generating new neurons in the brain. ✖
B) The process of removing dead neurons from the nervous system. ✖
C) The ability of neurons to change their connections and behavior in response to experience. ✔
D) The rigid structure of neurons that prevents change. ✖
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Neuroplasticity refers to the ability of the brain and nervous system to adapt and reorganize by forming new neural connections throughout life. This process allows the nervous system to adjust to new experiences, learning, and recovery from injuries.
101 Which type of glial cell is responsible for forming the myelin sheath in the central nervous system?
A) Oligodendrocytes ✔
B) Astrocytes ✖
C) Schwann cells ✖
D) Microglia ✖
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Oligodendrocytes are the glial cells that produce the myelin sheath around axons in the central nervous system (CNS). Schwann cells perform a similar function in the peripheral nervous system (PNS).
102 What is the function of excitatory neurotransmitters in the nervous system?
A) They decrease the likelihood of action potential generation. ✖
B) They enhance the likelihood of action potential generation by causing depolarization. ✔
C) They prevent neurotransmitter release. ✖
D) They inhibit the activity of glial cells. ✖
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Excitatory neurotransmitters, such as glutamate, bind to receptors on the postsynaptic neuron and cause depolarization, increasing the likelihood that the neuron will reach the threshold to generate an action potential.
103 Which phase of an action potential is characterized by the opening of voltage-gated potassium channels?
A) Repolarization ✔
B) Depolarization ✖
C) Hyperpolarization ✖
D) Resting phase ✖
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During repolarization, voltage-gated potassium channels open, allowing potassium ions (K+) to flow out of the neuron, which helps to restore the negative charge inside the neuron after the rapid depolarization phase.
104 Which neurotransmitter is involved in motor control and is deficient in Parkinson’s disease?
A) Acetylcholine ✖
B) Serotonin ✖
C) Norepinephrine ✖
D) Dopamine ✔
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Dopamine is a neurotransmitter crucial for regulating movement and coordination. In Parkinson’s disease, there is a deficiency of dopamine due to the degeneration of dopaminergic neurons in the substantia nigra, leading to motor control difficulties.
105 How does the presence of myelin affect the conduction velocity of action potentials?
A) It decreases conduction velocity. ✖
B) It has no effect on conduction velocity. ✖
C) It increases conduction velocity. ✔
D) It causes action potentials to stop completely. ✖
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Myelin acts as an insulator around axons, allowing for faster transmission of action potentials via saltatory conduction, where action potentials jump from one node of Ranvier to the next. This significantly increases conduction velocity compared to unmyelinated axons.
106 What is the primary role of calcium ions in synaptic transmission?
A) They trigger the release of neurotransmitters from vesicles. ✔
B) They facilitate the synthesis of neurotransmitters. ✖
C) They help in the propagation of action potentials along the axon. ✖
D) They maintain resting membrane potential. ✖
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Calcium ions (Ca2+) play a crucial role in synaptic transmission. When an action potential arrives at the presynaptic terminal, the influx of Ca2+ through voltage-gated calcium channels triggers the fusion of synaptic vesicles with the presynaptic membrane, leading to the release of neurotransmitters into the synaptic cleft.
107 What role does acetylcholine play at the neuromuscular junction?
A) It inhibits muscle contraction. ✖
B) It promotes muscle contraction by binding to receptors on muscle fibers. ✔
C) It prevents synaptic transmission. ✖
D) It is only involved in the central nervous system. ✖
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At the neuromuscular junction, acetylcholine (ACh) is released from motor neurons and binds to receptors on muscle fibers, leading to depolarization of the muscle membrane and triggering muscle contraction. It is essential for voluntary muscle movement.
108 What physiological change occurs when a neuron is depolarized?
A) The inside of the neuron becomes more negative relative to the outside. ✖
B) The membrane potential increases towards zero or becomes positive. ✔
C) Potassium channels open, allowing K+ to enter the neuron. ✖
D) Calcium is removed from the cytoplasm. ✖
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Depolarization occurs when the membrane potential of a neuron becomes less negative (more positive) due to the influx of sodium ions (Na+) when voltage-gated sodium channels open. This shift in membrane potential can lead to the generation of an action potential.
109 What effect do neurotransmitter reuptake inhibitors have on synaptic transmission?
A) They prevent neurotransmitter release. ✖
B) They prolong the action of neurotransmitters in the synaptic cleft. ✔
C) They decrease neurotransmitter levels in the synapse. ✖
D) They enhance the synthesis of neurotransmitters. ✖
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Neurotransmitter reuptake inhibitors block the reabsorption of neurotransmitters by the presynaptic neuron, leading to an increased concentration of neurotransmitters in the synaptic cleft. This prolongs their action on the postsynaptic receptors, enhancing synaptic transmission.
110 Which part of the neuron is responsible for transmitting signals to other neurons?
A) Dendrites ✖
B) Cell body ✖
C) Axon ✔
D) Synapse ✖
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The axon is the part of the neuron that conducts electrical impulses away from the cell body to other neurons, muscles, or glands. It is essential for transmitting signals over long distances.
111 What characterizes the all-or-nothing principle of action potentials?
A) The size of the action potential varies with stimulus strength. ✖
B) Action potentials are generated only if the threshold is reached; otherwise, no action occurs. ✔
C) Action potentials can be graded in magnitude. ✖
D) It applies only to excitatory neurotransmitter responses. ✖
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The all-or-nothing principle states that once a neuron’s membrane potential reaches a certain threshold, an action potential will be generated at full amplitude. If the threshold is not reached, no action potential occurs.
112 Which of the following describes the function of Schwann cells?
A) They regulate blood flow to neurons. ✖
B) They form myelin sheaths around axons in the central nervous system. ✖
C) They produce cerebrospinal fluid. ✖
D) They form myelin sheaths around axons in the peripheral nervous system. ✔
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Schwann cells are glial cells in the peripheral nervous system that wrap around axons to form myelin sheaths. This myelination increases the speed of action potential conduction and provides insulation for the axons.
113 What is the main function of the neuromuscular junction?
A) To transmit motor commands from the muscle to the CNS ✖
B) To generate action potentials within muscle fibers ✖
C) To transmit signals from motor neurons to skeletal muscle fibers through acetylcholine release ✔
D) To inhibit muscle contraction when necessary ✖
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The neuromuscular junction is a specialized synapse where motor neurons release acetylcholine, which binds to receptors on the muscle fiber membrane, causing muscle contraction.
114 Which ion is necessary to release neurotransmitters from the presynaptic terminal?
A) Sodium (Na+) ✖
B) Potassium (K+) ✖
C) Calcium (Ca2+) ✔
D) Chloride (Cl-) ✖
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The influx of calcium ions into the presynaptic terminal triggers the fusion of synaptic vesicles with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.
115 What type of neurotransmitter receptor is found at the neuromuscular junction?
A) Muscarinic acetylcholine receptor ✖
B) Nicotinic acetylcholine receptor ✔
C) GABA receptor ✖
D) Dopamine receptor ✖
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The neuromuscular junction contains nicotinic acetylcholine receptors, which are ligand-gated ion channels that open when acetylcholine binds, allowing sodium ions to enter the muscle fiber and trigger contraction.
116 What happens to acetylcholine after it is released into the synaptic cleft?
A) It binds to postsynaptic receptors and then diffuses away ✖
B) It is broken down by acetylcholinesterase into acetate and choline ✔
C) It is reabsorbed intact by the presynaptic neuron ✖
D) It triggers an action potential in the postsynaptic membrane and remains bound indefinitely ✖
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Acetylcholinesterase rapidly breaks down acetylcholine in the synaptic cleft into acetate and choline, terminating the signal. The choline is then recycled by the presynaptic neuron.
117 Which process ensures that neurotransmitter release is tightly regulated at the neuromuscular junction?
A) Continuous release of acetylcholine into the synaptic cleft ✖
B) Depolarization of the postsynaptic muscle fiber ✖
C) Ca2+ influx triggering vesicle fusion and neurotransmitter release ✔
D) The reuptake of acetylcholine by the postsynaptic cell ✖
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Calcium ions entering the presynaptic terminal trigger the fusion of synaptic vesicles with the membrane, ensuring that neurotransmitter release occurs only in response to an action potential.
118 How does acetylcholinesterase affect synaptic transmission at the neuromuscular junction?
A) It enhances the effect of acetylcholine by keeping it in the cleft longer ✖
B) It degrades acetylcholine, stopping the transmission of the signal ✔
C) It transports acetylcholine back into the presynaptic neuron ✖
D) It stimulates the release of acetylcholine from the presynaptic vesicles ✖
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Acetylcholinesterase is responsible for breaking down acetylcholine in the synaptic cleft, terminating the signal, and allowing the muscle fiber to relax.
119 What causes the depolarization of the postsynaptic muscle fiber at the neuromuscular junction?
A) Influx of calcium ions ✖
B) Binding of acetylcholine to muscarinic receptors ✖
C) Influx of sodium ions through nicotinic acetylcholine receptors ✔
D) Efflux of potassium ions ✖
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When acetylcholine binds to nicotinic receptors on the muscle fiber, sodium ions enter the muscle, causing depolarization and triggering an action potential that leads to muscle contraction.
120 How does the SNARE complex contribute to neurotransmitter release?
A) It forms channels that allow neurotransmitters to pass through the membrane ✖
B) It binds to acetylcholine receptors on the postsynaptic membrane ✖
C) It helps vesicles dock and fuse with the presynaptic membrane in response to Ca2+ influx ✔
D) It breaks down acetylcholine in the synaptic cleft ✖
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The SNARE complex is involved in the priming and docking of synaptic vesicles, facilitating their fusion with the presynaptic membrane when calcium ions enter, leading to neurotransmitter release.
121 What is the role of acetylcholinesterase inhibitors in conditions like myasthenia gravis?
A) To reduce the amount of acetylcholine released ✖
B) To enhance acetylcholine breakdown at the synapse ✖
C) To prolong the presence of acetylcholine in the synapse by preventing its breakdown ✔
D) To prevent acetylcholine from binding to its receptors ✖
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Acetylcholinesterase inhibitors block the enzyme acetylcholinesterase, preventing it from breaking down acetylcholine, thus increasing its availability at the synapse and improving muscle contraction in conditions like myasthenia gravis.