Sensorimotor

Question 1

Describe an inborn reflex.

Answer 1

An inborn (intrinsic) reflex is a rapid, involuntary, and predictable motor response to a stimulus.

Question 2

Explain how learned reflexes differ from inborn reflexes.

Answer 2

Learned (acquired) reflexes result from practice or repetition, unlike inborn reflexes which are innate.

Question 3

Define somatic reflexes and their function.

Answer 3

Somatic reflexes activate skeletal muscle and are involved in voluntary motor responses.

Question 4

What are autonomic reflexes and their role?

Answer 4

Autonomic (visceral) reflexes activate visceral effectors such as smooth or cardiac muscle or glands.

Question 5

How do spinal reflexes operate in relation to the brain?

Answer 5

Spinal reflexes occur without direct involvement of higher brain centers, but the brain is informed of spinal reflex activity.

Question 6

How does the brain influence muscle length through the stretch reflex?

Answer 6

The brain sets the muscle’s length by regulating the stretch reflex, which adjusts muscle tone reflexively to maintain posture.

Question 7

Explain the clinical importance of testing somatic reflexes.

Answer 7

Testing somatic reflexes is important clinically to assess the condition of the nervous system; abnormalities may indicate degeneration or pathology.

Question 8

List the most commonly assessed reflexes in clinical settings.

Answer 8

The most commonly assessed reflexes are stretch, flexor, and superficial reflexes.

Question 9

Describe the role of proprioceptors in muscle coordination.

Answer 9

Proprioceptors provide the nervous system with information about muscle length and tension to coordinate skeletal muscle smoothly.

Question 10

What are muscle spindles and their function?

Answer 10

Muscle spindles are sensory receptors that provide information about muscle stretch and are composed of modified skeletal muscle fibers.

Question 11

Explain how external and internal stretches affect muscle spindles.

Answer 11

External stretch occurs when an external force lengthens the entire muscle, while internal stretch happens when gamma motor neurons stimulate the ends of the spindle to contract, stretching the spindle.

Question 12

Describe the role of muscle spindles in the stretch reflex.

Answer 12

Muscle spindles detect changes in muscle length and the rate of stretch, sending impulses to the spinal cord to initiate a reflex response.

Question 13

Explain the structure of muscle spindles.

Answer 13

Muscle spindles consist of 3–10 intrafusal muscle fibers enclosed in a connective tissue capsule, with central regions lacking myofilaments.

Question 14

Differentiate between extrafusal and intrafusal muscle fibers.

Answer 14

Extrafusal muscle fibers are the regular contractile muscle fibers, while intrafusal muscle fibers are specialized fibers within muscle spindles.

Question 15

Explain the two ways muscle spindles can be stretched.

Answer 15

Muscle spindles can be stretched by external stretch from an external force or internal stretch from γ motor neurons stimulating spindle ends.

Question 16

What are anulospiral endings and their function?

Answer 16

Anulospiral endings are primary sensory endings that wrap around muscle spindles and are stimulated by the rate and degree of stretch.

Question 17

Describe flower spray endings in muscle spindles.

Answer 17

Flower spray endings are secondary sensory endings located at the ends of muscle spindles, stimulated only by the degree of stretch.

Question 18

How do gamma (γ) efferent fibers contribute to muscle spindle function?

Answer 18

Gamma (γ) efferent fibers innervate the contractile end regions of muscle spindles, helping to maintain spindle sensitivity.

Question 19

What is the role of alpha (α) efferent fibers in muscle function?

Answer 19

Alpha (α) efferent fibers innervate extrafusal muscle fibers, which are responsible for muscle contraction.

Question 21

Do stretch reflexes play a role in maintaining muscle tone?

Answer 21

Yes, stretch reflexes help maintain muscle tone in large postural muscles and adjust it reflexively in response to changes in muscle length.

Question 22

Explain the knee-jerk reflex as an example of a stretch reflex.

Answer 22

In the knee-jerk reflex, the quadriceps muscle is stretched, causing it to contract while the hamstrings relax, preventing the knee from buckling.

Question 23

Define monosynaptic and ipsilateral reflexes in the context of stretch reflexes.

Answer 23

Monosynaptic reflexes involve a single synapse between sensory and motor neurons, while ipsilateral reflexes occur on the same side of the body.

Question 24

How does reciprocal inhibition function during a stretch reflex?

Answer 24

Reciprocal inhibition occurs when afferent fibers synapse with interneurons that inhibit the motor neurons of antagonistic muscles, allowing the stretched muscle to contract while the antagonist relaxes.

Question 25

What is the significance of positive reflex reactions in stretch reflexes?

Answer 25

Positive reflex reactions indicate that sensory and motor connections between the muscle and spinal cord are intact, and the strength of the response reflects the degree of spinal cord excitability.

Question 26

Describe the role of polysynaptic reflexes in muscle protection.

Answer 26

Polysynaptic reflexes help prevent damage due to excessive stretch by producing muscle relaxation in response to tension.

Question 27

Explain how tendon reflexes are activated.

Answer 27

Tendon reflexes are activated by contraction or passive stretch of a muscle, leading to afferent impulses being transmitted to the spinal cord.

Question 28

What happens to a contracting muscle during a tendon reflex

Answer 28

During a tendon reflex, the contracting muscle relaxes in response to the tension detected by the muscle spindle.

Question 29

Describe the role of the antagonist in muscle contraction.

Answer 29

Antagonist contracts through reciprocal activation, allowing for coordinated movement and adjustment of muscle tension.

Question 29

Explain the flexor (withdrawal) reflex.

Answer 29

The flexor reflex is initiated by a painful stimulus, causing an automatic withdrawal of the threatened body part. It is ipsilateral and polysynaptic, involving multiple muscles for effective response.

Question 30

How does the brain influence the flexor reflex?

Answer 30

The brain can override the flexor reflex, as seen when a person anticipates a painful stimulus, such as a finger stick for a blood test, and consciously prevents the arm from withdrawing.

Question 31

Define the crossed extensor reflex and its components.

Answer 31

The crossed extensor reflex occurs alongside flexor reflexes in weight-bearing limbs to maintain balance, consisting of an ipsilateral withdrawal reflex and a contralateral extensor reflex.

Question 32

What happens during the crossed extensor reflex when stepping on broken glass?

Answer 32

When stepping barefoot on broken glass, the damaged leg withdraws (flexes) while the opposite leg extends to support the weight shift.

Question 33

Describe the superficial reflexes and their clinical significance.

Answer 33

Superficial reflexes are elicited by gentle cutaneous stimulation and are clinically important as they can signal problems in upper motor pathways or cord-level reflex arcs.

Question 34

Explain the plantar reflex and its significance.

Answer 34

The plantar reflex tests the integrity of the spinal cord from L4 to S2, where stroking the lateral aspect of the sole of the foot results in downward flexion of the toes.

Question 35

What is Babinski’s sign and when does it occur?

Answer 35

Babinski’s sign occurs when there is damage to the motor cortex or corticospinal tracts, causing the hallux to dorsiflex and smaller toes to fan laterally, which is normal in infants up to about 1 year due to incomplete myelination.

Question 36

Define the abdominal reflex and its testing method.

Answer 36

The abdominal reflex tests the integrity of the spinal cord from T8 to T12, where stroking the skin of the lateral abdomen results in contraction of abdominal muscles and movement of the umbilicus toward the stimulus.

Question 37

How does the intensity of the abdominal reflex vary among individuals?

Answer 37

The intensity of the abdominal reflex can vary from one person to another and may be absent in cases of corticospinal tract lesions.