EDT Neuroanatomy & Physiology 3 — Questions and Answers
Question 1: Which layer of a peripheral nerve surrounds individual axons?
- Epineurium
- Perineurium
- Endoneurium (Correct answer)
- Myelin sheath
Correct answer: Endoneurium
The endoneurium is the innermost connective tissue layer that directly ensheathes each individual nerve fiber.
Question 2: The H-reflex is the electrophysiological analogue of which clinical reflex?
- Babinski reflex
- Hoffmann reflex
- Ankle (Achilles) tendon reflex (Correct answer)
- Patellar tendon reflex
Correct answer: Ankle (Achilles) tendon reflex
The H-reflex bypasses the muscle spindle and electrically activates Ia afferents, mimicking the ankle tendon (Achilles) reflex arc.
Question 3: What is the function of Ia afferent fibers from muscle spindles?
- Detect Golgi tendon organ stretch
- Signal nociception from muscle
- Signal dynamic and static muscle stretch to the spinal cord (Correct answer)
- Carry motor commands to intrafusal fibers
Correct answer: Signal dynamic and static muscle stretch to the spinal cord
Ia afferents from primary endings of muscle spindles signal both the dynamic (velocity) and static (length) components of muscle stretch.
Question 4: In a demyelinating neuropathy, which electrodiagnostic parameter is most characteristically prolonged?
- Amplitude of the CMAP
- Distal motor latency (Correct answer)
- Duration of the F-wave
- Needle EMG insertional activity
Correct answer: Distal motor latency
Loss of myelin slows conduction velocity and prolongs distal motor latency, the hallmark of a demyelinating process on NCS.
Question 5: Which spinal cord levels form the lumbosacral plexus roots that contribute to the sciatic nerve?
- C5–C8 and T1
- L1–L3
- L4–S3 (Correct answer)
- S2–S4
Correct answer: L4–S3
The sciatic nerve is formed from anterior rami of L4 through S3, making it the largest nerve in the body.
Question 6: Which type of muscle fiber has the fastest contraction speed and is recruited last during voluntary effort?
- Type I (slow-twitch)
- Type IIa (fast-twitch oxidative)
- Type IIx/IIb (fast-twitch glycolytic) (Correct answer)
- Intrafusal fiber
Correct answer: Type IIx/IIb (fast-twitch glycolytic)
Type IIx/IIb fast-twitch glycolytic fibers contract fastest but fatigue quickly and are recruited only during high-force output per the size principle.
Question 7: What anatomical structure separates the brachial plexus into divisions above and below it?
- First rib
- Clavicle (Correct answer)
- Coracoid process
- Scalene muscles
Correct answer: Clavicle
The clavicle divides the brachial plexus into supraclavicular (trunks) and infraclavicular (cords) segments.
EDT Neuroanatomy & Physiology 3
Which layer of a peripheral nerve surrounds individual axons?