EXSS 380: EXAM 1 | QUESTIONS AND ANSWERS | 2025/2026 UPDATE |
WITH COMPLETE SOLUTION!!
1. Information about the rate of change in muscle length (kinesthesia) is primarily provided
by which type of sensory afferent?
A) Type Ia
B) Type Ib
C) Type II
D) Type III
Correct Answer: A) Type Ia
Rationale: Type Ia afferents are the primary sensory endings of the muscle spindle. They are
highly sensitive to the velocity of muscle stretch, providing the central nervous system with
dynamic information about limb movement (kinesthesia).
2. In the context of the muscle spindle, a change in muscle length is directly proportional to
a change in:
A) Muscle force
B) Joint motion (angle)
C) Tendon tension
D) Skin stretch
Correct Answer: B) Joint motion (angle)
Rationale: Muscles cross joints. As a joint flexes or extends, the muscles crossing that joint will
lengthen or shorten. The muscle spindle detects this change in muscle length, which the CNS
interprets as a change in the joint angle.
3. Information about static muscle length (joint position sense or proprioception) is
primarily provided by which type of sensory afferent?
A) Type Ia
B) Type Ib
C) Type II
D) Type IV
Correct Answer: C) Type II
Rationale: Type II afferents are the secondary sensory endings of the muscle spindle. They are
sensitive to the absolute length of the muscle, providing the CNS with static information about
the position of a limb in space (proprioception).
4. The Golgi tendon organ (GTO) is innervated by Type Ib afferents. Its firing rate is
proportional to the tension in the tendon, which is created when:
A) The muscle spindle is stretched.
B) The skin over the muscle is stretched.
C) Collagen strands in the tendon pinch the nerve endings.
D) The joint capsule is compressed.
,[Type here]
Correct Answer: C) Collagen strands in the tendon pinch the nerve endings.
Rationale: The nerve endings of the Type Ib afferent are interwoven with the collagen fibers of
the tendon. When the muscle contracts and creates tension, these collagen strands are pulled taut,
compressing or "pinching" the nerve endings and causing them to fire.
5. Which sensory afferent is primarily responsible for sensing muscle force/tension?
A) Type Ia
B) Type Ib
C) Type II
D) Articular receptors
Correct Answer: B) Type Ib
Rationale: Type Ib afferents are the sensory neurons that innervate the Golgi tendon organs
(GTOs). GTOs are located at the musculotendinous junction and are exquisitely sensitive to
changes in muscle tension or force.
6. Receptors that are anatomically similar to Golgi tendon organs but are located in
ligaments are known as:
A) Pacinian corpuscles
B) Ruffini endings
C) Golgi endings
D) Free nerve endings
Correct Answer: C) Golgi endings
Rationale: Golgi-like endings are found within ligaments and function similarly to GTOs,
providing information about ligament tension and joint position, particularly at the extremes of
the range of motion.
7. Which type of sensory receptor is known to fire signals primarily at the extreme limits of
a joint's range of motion, acting as "limit detectors"?
A) Muscle spindles
B) Golgi tendon organs
C) Cutaneous receptors
D) Articular receptors
Correct Answer: D) Articular receptors
Rationale: Articular (joint) receptors, such as Ruffini and Pacinian corpuscles and Golgi
endings, are located in the joint capsule and ligaments. Many of these receptors are most active
at the very end of the joint's range of motion, providing a signal to the CNS about joint position
and helping to prevent injury.
8. In addition to muscle spindles, which other type of receptor provides significant input for
our sense of proprioception, particularly for the distal joints like those in the fingers?
A) Articular receptors
, [Type here]
B) Visual receptors
C) Cutaneous receptors
D) Vestibular receptors
Correct Answer: C) Cutaneous receptors
Rationale: Cutaneous mechanoreceptors in the skin, which detect stretch, are also important
sources of proprioceptive information. The stretching of skin on one side of a joint and the
slackening on the other provides the CNS with information about the joint's angle.
9. The electrical potential difference across the membrane of a resting skeletal muscle cell is
approximately:
A) +30 mV
B) 0 mV
C) -70 mV
D) -80 mV
Correct Answer: D) -80 mV
Rationale: Similar to neurons, muscle cells (sarcolemma) maintain a negative resting membrane
potential. In skeletal muscle, this potential is typically around -80 to -90 mV.
10. In a neuron, excitation (depolarization) and inhibition (hyperpolarization) are
fundamentally caused by:
A) The action of the sodium-potassium pump.
B) Changes in the resting membrane potential.
C) The release of calcium from the sarcoplasmic reticulum.
D) The synthesis of new proteins.
Correct Answer: B) Changes in the resting membrane potential.
Rationale: Both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic
potentials (IPSPs) are small, localized changes in the resting membrane potential of the
postsynaptic neuron. These changes are what move the neuron closer to (excitation) or further
from (inhibition) the threshold for firing an action potential.
11. The movement of an ion across a neuron's membrane is determined by the net force,
which is the sum of which two forces?
A) Gravitational force and electrical force.
B) Concentration gradient and electrostatic force.
C) Strong nuclear force and weak nuclear force.
D) Centripetal force and centrifugal force.
Correct Answer: B) Concentration gradient and electrostatic force.
Rationale: The concentration gradient is the force that drives an ion to move from an area of
high concentration to an area of low concentration. The electrostatic force is the force that drives
WITH COMPLETE SOLUTION!!
1. Information about the rate of change in muscle length (kinesthesia) is primarily provided
by which type of sensory afferent?
A) Type Ia
B) Type Ib
C) Type II
D) Type III
Correct Answer: A) Type Ia
Rationale: Type Ia afferents are the primary sensory endings of the muscle spindle. They are
highly sensitive to the velocity of muscle stretch, providing the central nervous system with
dynamic information about limb movement (kinesthesia).
2. In the context of the muscle spindle, a change in muscle length is directly proportional to
a change in:
A) Muscle force
B) Joint motion (angle)
C) Tendon tension
D) Skin stretch
Correct Answer: B) Joint motion (angle)
Rationale: Muscles cross joints. As a joint flexes or extends, the muscles crossing that joint will
lengthen or shorten. The muscle spindle detects this change in muscle length, which the CNS
interprets as a change in the joint angle.
3. Information about static muscle length (joint position sense or proprioception) is
primarily provided by which type of sensory afferent?
A) Type Ia
B) Type Ib
C) Type II
D) Type IV
Correct Answer: C) Type II
Rationale: Type II afferents are the secondary sensory endings of the muscle spindle. They are
sensitive to the absolute length of the muscle, providing the CNS with static information about
the position of a limb in space (proprioception).
4. The Golgi tendon organ (GTO) is innervated by Type Ib afferents. Its firing rate is
proportional to the tension in the tendon, which is created when:
A) The muscle spindle is stretched.
B) The skin over the muscle is stretched.
C) Collagen strands in the tendon pinch the nerve endings.
D) The joint capsule is compressed.
,[Type here]
Correct Answer: C) Collagen strands in the tendon pinch the nerve endings.
Rationale: The nerve endings of the Type Ib afferent are interwoven with the collagen fibers of
the tendon. When the muscle contracts and creates tension, these collagen strands are pulled taut,
compressing or "pinching" the nerve endings and causing them to fire.
5. Which sensory afferent is primarily responsible for sensing muscle force/tension?
A) Type Ia
B) Type Ib
C) Type II
D) Articular receptors
Correct Answer: B) Type Ib
Rationale: Type Ib afferents are the sensory neurons that innervate the Golgi tendon organs
(GTOs). GTOs are located at the musculotendinous junction and are exquisitely sensitive to
changes in muscle tension or force.
6. Receptors that are anatomically similar to Golgi tendon organs but are located in
ligaments are known as:
A) Pacinian corpuscles
B) Ruffini endings
C) Golgi endings
D) Free nerve endings
Correct Answer: C) Golgi endings
Rationale: Golgi-like endings are found within ligaments and function similarly to GTOs,
providing information about ligament tension and joint position, particularly at the extremes of
the range of motion.
7. Which type of sensory receptor is known to fire signals primarily at the extreme limits of
a joint's range of motion, acting as "limit detectors"?
A) Muscle spindles
B) Golgi tendon organs
C) Cutaneous receptors
D) Articular receptors
Correct Answer: D) Articular receptors
Rationale: Articular (joint) receptors, such as Ruffini and Pacinian corpuscles and Golgi
endings, are located in the joint capsule and ligaments. Many of these receptors are most active
at the very end of the joint's range of motion, providing a signal to the CNS about joint position
and helping to prevent injury.
8. In addition to muscle spindles, which other type of receptor provides significant input for
our sense of proprioception, particularly for the distal joints like those in the fingers?
A) Articular receptors
, [Type here]
B) Visual receptors
C) Cutaneous receptors
D) Vestibular receptors
Correct Answer: C) Cutaneous receptors
Rationale: Cutaneous mechanoreceptors in the skin, which detect stretch, are also important
sources of proprioceptive information. The stretching of skin on one side of a joint and the
slackening on the other provides the CNS with information about the joint's angle.
9. The electrical potential difference across the membrane of a resting skeletal muscle cell is
approximately:
A) +30 mV
B) 0 mV
C) -70 mV
D) -80 mV
Correct Answer: D) -80 mV
Rationale: Similar to neurons, muscle cells (sarcolemma) maintain a negative resting membrane
potential. In skeletal muscle, this potential is typically around -80 to -90 mV.
10. In a neuron, excitation (depolarization) and inhibition (hyperpolarization) are
fundamentally caused by:
A) The action of the sodium-potassium pump.
B) Changes in the resting membrane potential.
C) The release of calcium from the sarcoplasmic reticulum.
D) The synthesis of new proteins.
Correct Answer: B) Changes in the resting membrane potential.
Rationale: Both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic
potentials (IPSPs) are small, localized changes in the resting membrane potential of the
postsynaptic neuron. These changes are what move the neuron closer to (excitation) or further
from (inhibition) the threshold for firing an action potential.
11. The movement of an ion across a neuron's membrane is determined by the net force,
which is the sum of which two forces?
A) Gravitational force and electrical force.
B) Concentration gradient and electrostatic force.
C) Strong nuclear force and weak nuclear force.
D) Centripetal force and centrifugal force.
Correct Answer: B) Concentration gradient and electrostatic force.
Rationale: The concentration gradient is the force that drives an ion to move from an area of
high concentration to an area of low concentration. The electrostatic force is the force that drives
