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.
Muscle Physiology MCQs
1 Troponin and tropomyosin are components of which one of the following structures?
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Troponin and tropomyosin are regulatory proteins associated with the actin filaments in skeletal and cardiac muscle. They regulate the contraction process by controlling the interaction between actin and myosin. Troponin binds calcium ions, which induces a change in the tropomyosin configuration, allowing myosin to bind to actin, resulting in muscle contraction.
2 Action potentials in skeletal muscle cells trigger the release from the sarcoplasmic reticulum of what ion critical to the muscleโs contractile process?
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The release of calcium ions (Caยฒโบ) from the sarcoplasmic reticulum is a key step in muscle contraction. When the muscle cellโs action potential reaches the sarcoplasmic reticulum, it opens calcium release channels, allowing Caยฒโบ to flow into the cytoplasm, where it binds to troponin, initiating the contraction process.
3 A gross skeletal muscle belly can be instructed (by the central nervous system) to contract more forcefully by:
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Muscle contraction strength can be increased by recruiting more motor units (spatial summation) or by increasing the rate of action potentials in the motor neurons, causing more frequent contractions (temporal summation). These two mechanisms ensure that the muscle generates more force as needed.
4 Which one of the following is not found in smooth muscle?
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Smooth muscle lacks T tubules, which are found in skeletal and cardiac muscle. T tubules help transmit action potentials to the interior of muscle fibers. In smooth muscle, calcium entry for contraction is achieved mainly through caveolae, small invaginations in the plasma membrane.
5 Which one of the following is least likely to be significantly associated with a muscle that is primarily involved in brief, powerful movements?
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Muscles that perform brief, powerful movements typically have large motor units and fast-twitch fibers. These muscles are designed for quick and strong contractions, while small motor units are associated with fine, precise control, such as in muscles responsible for small, delicate movements.
6 Which of the following is the primary role of the sarcoplasmic reticulum in muscle contraction?
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The sarcoplasmic reticulum is an organelle in muscle cells responsible for storing calcium ions and releasing them into the cytoplasm when the muscle is stimulated by an action potential. This release of calcium is crucial for initiating the interaction between actin and myosin, which leads to muscle contraction.
7 The sliding filament mechanism in muscle contraction primarily involves which of the following processes?
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Muscle contraction occurs when actin filaments slide past myosin filaments, shortening the sarcomere and thus the entire muscle fiber. This process is powered by ATP and regulated by calcium ions released from the sarcoplasmic reticulum.
8 Fast-twitch muscle fibers are characterized by which of the following?
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Fast-twitch muscle fibers contract quickly and are designed for short bursts of power and speed, such as sprinting or jumping. However, they fatigue quickly because they rely on anaerobic metabolism, which produces energy less efficiently than aerobic metabolism.
9 Which of the following is a distinguishing feature of slow-twitch muscle fibers?
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Slow-twitch fibers are specialized for endurance and sustained activity, such as maintaining posture or long-distance running. They rely heavily on aerobic metabolism and have abundant blood vessels, mitochondria, and myoglobin, allowing them to resist fatigue.
10 What is the function of T tubules in skeletal muscle fibers?
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T tubules (transverse tubules) are extensions of the muscle fiberโs plasma membrane that penetrate into the fiberโs interior. They carry action potentials deep into the muscle fiber, allowing the sarcoplasmic reticulum to release calcium ions uniformly and ensuring synchronized contraction throughout the fiber.
11 Which of the following statements about the motor unit is correct?
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A motor unit is defined as one motor neuron and all the muscle fibers it innervates. Small motor units control precise movements, while larger motor units are responsible for more powerful, less precise actions. Each motor neuron can control multiple muscle fibers, but each fiber is only innervated by one motor neuron.
12 Which of the following best explains why skeletal muscle contracts more forcefully as more motor units are recruited?
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As more motor units are recruited, more muscle fibers are activated, leading to an increased number of actin and myosin interactions. This increases the total force generated by the muscle, a process known as spatial summation.
13 What is the function of calcium ions (Caยฒโบ) in muscle contraction?
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Calcium ions bind to troponin, causing a conformational change that moves tropomyosin away from the myosin binding sites on actin. This allows myosin heads to attach to actin, initiating the cross-bridge cycle and muscle contraction.
14 Which of the following best describes the role of ATP during muscle contraction?
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After the power stroke, ATP binds to the myosin head, causing it to detach from actin. ATP is then hydrolyzed, re-cocking the myosin head, enabling another cycle of contraction. Additionally, ATP is necessary to pump calcium ions back into the sarcoplasmic reticulum during relaxation.
15 Which of the following is true about the difference between cardiac and skeletal muscle contraction?
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In cardiac muscle, extracellular calcium influx is necessary to trigger further calcium release from the sarcoplasmic reticulum. In contrast, skeletal muscle contraction relies almost exclusively on calcium stored within the sarcoplasmic reticulum.
16 In which of the following ways is smooth muscle contraction different from skeletal muscle contraction?
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Smooth muscle relies heavily on extracellular calcium because it lacks a well-developed sarcoplasmic reticulum. The calcium influx from the extracellular space triggers contraction, which is typically slower but sustained compared to skeletal muscle.
17 What is the primary function of the Z disks in a sarcomere?
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Z disks anchor the actin filaments and mark the boundaries of a sarcomere, ensuring proper alignment during muscle contraction and relaxation. They play a crucial role in maintaining the structural integrity of the sarcomere.
18 What is the significance of the motor neuron pool in muscle control?
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The motor neuron pool consists of all the motor neurons that innervate a specific muscle. It plays a crucial role in generating force by regulating motor unit recruitment and firing.
19 Which of the following processes best explains how muscles prevent fatigue during prolonged low-intensity activities?
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During prolonged, low-intensity activities, muscles prevent fatigue by alternating the activation of motor units. This rotation allows some muscle fibers to rest while others maintain the required force, delaying fatigue.
20 Which of the following statements about electromyograms (EMGs) is correct?
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An electromyogram (EMG) records the electrical activity produced by muscles during contraction. EMGs are valuable in diagnosing neuromuscular disorders and assessing muscle function.
21 What is the role of titin in the sarcomere?
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Titin is a large protein that attaches thick myosin filaments to the Z disk, maintaining sarcomere alignment and elasticity. It helps the sarcomere return to its resting length after contraction.
22 How do smooth muscle cells differ from skeletal muscle cells in terms of neural control?
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Smooth muscle cells are regulated by the autonomic nervous system, hormones, and mechanical stimuli such as stretch. This diverse control allows smooth muscles to function independently from conscious thought.
23 Which of the following statements about excitation-contraction coupling in skeletal muscle is correct?
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When an action potential travels along the sarcolemma and into the T tubules, it triggers the release of calcium from the sarcoplasmic reticulum. This calcium is essential for the interaction between actin and myosin that leads to muscle contraction.
24 Which of the following types of muscle fibers would you expect to predominate in muscles used for maintaining posture?
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Slow-twitch fibers are specialized for endurance activities. They rely on aerobic metabolism and are resistant to fatigue, making them ideal for muscles that maintain posture over extended periods.
25 Which mechanism allows skeletal muscle fibers to increase the force of contraction without changing the length of the muscle?
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Isometric contractions occur when a muscle generates force without changing length. These contractions are essential for stabilizing joints and maintaining posture.
26 What is the primary difference between the action potentials in cardiac muscle and skeletal muscle?
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Cardiac muscle action potentials feature a plateau phase due to prolonged calcium influx, ensuring the heart muscle contracts long enough for effective blood pumping. This distinguishes cardiac muscle from skeletal muscle.
Reflex Physiology MCQs
27 Which of the following is NOT always a component of a reflex arc?
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Not all reflex arcs involve interneurons. Some reflexes, such as monosynaptic reflexes, involve a direct synapse between the sensory and motor neurons, bypassing the interneuron step.
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28 Which of the following is FALSE regarding sensory receptors in a reflex arc?
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Sensory receptors detect external stimuli and transduce them into action potentials but do not convert CNS action potentials into physical activity, which is the role of motor neurons.
29 What happens to the frequency of action potentials in a sensory neuron as stimulus intensity increases?
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As the intensity of a stimulus increases, the frequency of action potentials generated in the sensory neuron also increases, allowing the nervous system to interpret the strength of the stimulus.
30 Which of the following is an example of a segmental reflex?
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The quadriceps stretch reflex is a classic example of a segmental reflex, where the reflex arc occurs within a limited number of spinal segments.
31 In which type of reflex arc does the CNS circuitry traverse several spinal cord segments?
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An intersegmental reflex arc involves pathways that traverse multiple spinal cord segments, allowing the integration of input from several levels before producing a response.
32 Which of the following reflexes is considered suprasegmental, involving both the spinal cord and the brain?
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The pupillary light reflex is a suprasegmental reflex because it involves brainstem circuits in addition to the spinal cord, allowing for the regulation of pupil diameter in response to light.
33 Which of the following best describes a polysynaptic reflex?
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A polysynaptic reflex involves one or more interneurons between the sensory and motor neurons, allowing for more complex reflex responses compared to monosynaptic reflexes.
34 What is the role of interneurons in a polysynaptic reflex arc?
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Interneurons in polysynaptic reflex arcs modulate and integrate input before relaying the signal to motor neurons, contributing to more complex and adaptable reflexes.
35 Which of the following reflexes involves both excitation and inhibition of muscles?
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The flexor withdrawal reflex involves the excitation of flexor muscles to withdraw the limb from a harmful stimulus, along with the inhibition of extensor muscles via reciprocal inhibition.
36 Which change may result from damage to descending motor tracts that modulate reflexes?
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Damage to descending motor tracts can reduce inhibitory control over reflexes, resulting in exaggerated responses, known as hyperreflexia, commonly observed in spinal cord injuries.
37 What is the role of sensory receptors in a reflex arc?
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Sensory receptors detect environmental changes (e.g., heat, pressure) and transduce them into electrical signals (action potentials) that are transmitted to the CNS for processing.
38 What happens to the intensity of a stimulus when the frequency of action potentials increases?
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The CNS interprets a higher frequency of action potentials as a more intense stimulus, allowing it to respond appropriately based on the strength of the input.
39 In a monosynaptic reflex, how many synapses are involved?
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A monosynaptic reflex, such as the patellar reflex, involves a single synapse between a sensory neuron and a motor neuron, allowing for a rapid response.
40 Which of the following components in a reflex arc is responsible for executing the final reflex action?
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The motor neuron transmits signals from the central nervous system to the effector organ, executing the final reflex action, such as a muscle contraction.
41 In a suprasegmental reflex, which parts of the nervous system are involved?
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Suprasegmental reflexes involve both the spinal cord and the brain, such as the pupillary light reflex, which requires sensory input to be processed in the brainstem.
42 What is the role of reciprocal inhibition in reflex arcs?
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Reciprocal inhibition ensures that when one set of muscles contracts (e.g., flexors), the antagonistic muscles (e.g., extensors) are inhibited, preventing interference with the movement.
43 What happens to reflex responses when descending motor tracts are damaged?
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Damage to descending motor tracts reduces inhibitory input, leading to exaggerated reflexes, known as hyperreflexia, often seen in spinal cord injuries.
44 Which of the following statements describes the function of interneurons in reflex arcs?
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Interneurons process and modulate sensory input within the CNS before transmitting signals to motor neurons, enabling more complex reflex responses.
Muscle Spindle and Golgi Tendon Organ MCQs
45 What happens to the frequency of action potentials in sensory neurons of muscle spindles when the muscle is stretched?
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When a muscle is stretched, the intrafusal fibers of the muscle spindle are also stretched, increasing the frequency of action potentials generated by the sensory neurons. This allows the CNS to detect changes in muscle length.
46 Activation of the Golgi tendon organ in a muscle leads to which of the following responses?
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The Golgi tendon organ detects tension in the muscle and sends signals that polysynaptically inhibit the ฮฑ motor neurons, reducing muscle contraction and preventing excessive tension.
47 Which of the following is NOT characteristic of the muscle spindle?
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The muscle spindle is sensitive to changes in muscle length but not muscle tension, which is detected by the Golgi tendon organ.
48 Gamma (ฮณ) motor neurons serve which of the following functions?
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Gamma motor neurons adjust the sensitivity of the muscle spindle by regulating the tension of intrafusal fibers during muscle contraction.
49 What is the role of the muscle spindle in reflexes such as the knee-jerk reflex?
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In the knee-jerk reflex, the muscle spindle detects stretching of the quadriceps and sends sensory information to the CNS, leading to a monosynaptic activation of ฮฑ motor neurons, causing muscle contraction.
50 How does the CNS prevent slackening of the muscle spindle during muscle contraction?
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The CNS coactivates both ฮฑ and ฮณ motor neurons to keep the muscle spindle taut during contraction, ensuring it remains sensitive to further stretches.
51 Which of the following best describes the function of the Golgi tendon organ?
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The Golgi tendon organ detects tension generated by muscle contractions and sends signals to reduce excessive tension, preventing muscle damage.
52 What is the purpose of inhibitory interneurons in the stretch reflex?
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Inhibitory interneurons in the stretch reflex arc prevent the contraction of antagonist muscles, allowing smooth and efficient movement of the agonist muscle.
53 Which of the following best describes the relationship between extrafusal and intrafusal muscle fibers?
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Intrafusal fibers are arranged in parallel with extrafusal fibers, allowing the muscle spindle to detect changes in muscle length during contraction or stretch.
54 What role do type IA spindle sensory neurons play during muscle stretch?
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Type Ia spindle sensory neurons are sensitive to changes in muscle length, especially during dynamic movements, providing feedback to the CNS about the rate and magnitude of stretching.
55 Which of the following best describes the role of alpha (ฮฑ) motor neurons in muscle contraction?
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Alpha (ฮฑ) motor neurons innervate extrafusal muscle fibers, which are responsible for generating the force required for muscle contraction.
56 Which sensory information is detected by muscle spindles?
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Muscle spindles detect changes in muscle length and the rate of stretch, helping regulate muscle tone and coordination.
57 How does the Golgi tendon organ contribute to muscle protection?
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The Golgi tendon organ detects muscle tension and sends inhibitory signals to ฮฑ motor neurons, reducing contraction to prevent injury from excessive force.
58 What is the role of dynamic nuclear bag fibers in muscle spindles?
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Dynamic nuclear bag fibers detect rapid changes in muscle length, providing critical input during quick stretches to maintain posture and balance.
59 Which statement about gamma (ฮณ) motor neurons is NOT true?
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Gamma motor neurons are usually coactivated with ฮฑ motor neurons to ensure the muscle spindle remains sensitive to stretch during contraction.
60 Which of the following best describes the role of the muscle spindle in maintaining posture?
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The muscle spindle continuously monitors muscle length and stretch, allowing the CNS to make automatic adjustments to maintain posture, especially in response to small, involuntary shifts in body position.
61 How does the CNS modulate the sensitivity of the muscle spindle to muscle stretch?
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Gamma motor neurons adjust the tension of the intrafusal fibers in the muscle spindle, modulating its sensitivity to stretch. This allows the spindle to remain sensitive even during muscle contraction.
62 Which of the following accurately describes the interaction between muscle spindles and Golgi tendon organs in maintaining muscle control?
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The muscle spindle monitors changes in muscle length and stretch, while the Golgi tendon organ detects muscle tension. Together, they help the CNS coordinate appropriate muscle responses for movement and protection against injury.
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