ABEM ABEM Anatomy & Neurophysiology 1 — Questions and Answers
Question 1: Which ion channel is primarily responsible for the upstroke of a nerve action potential?
- Voltage-gated sodium channels (Correct answer)
- Voltage-gated potassium channels
- Ligand-gated calcium channels
- Chloride leak channels
Correct answer: Voltage-gated sodium channels
Voltage-gated sodium channels open rapidly in response to membrane depolarization, driving the fast upstroke of the action potential.
Question 2: The anterior interosseous nerve is a branch of which major nerve?
- Ulnar nerve
- Radial nerve
- Median nerve (Correct answer)
- Musculocutaneous nerve
Correct answer: Median nerve
The anterior interosseous nerve arises from the median nerve in the proximal forearm and supplies the deep flexor compartment.
Question 3: What is the resting membrane potential of a typical mammalian motor neuron?
- -30 mV
- -70 mV (Correct answer)
- -90 mV
- +40 mV
Correct answer: -70 mV
The resting membrane potential of most mammalian neurons is approximately -70 mV, maintained by the Na+/K+ ATPase pump.
Question 4: Which structure forms the myelin sheath in the peripheral nervous system?
- Oligodendrocytes
- Astrocytes
- Schwann cells (Correct answer)
- Microglia
Correct answer: Schwann cells
Schwann cells wrap around peripheral nerve axons to form the myelin sheath, enabling saltatory conduction.
Question 5: The dorsal interossei muscles of the hand are innervated by which nerve?
- Median nerve
- Radial nerve
- Ulnar nerve (Correct answer)
- Anterior interosseous nerve
Correct answer: Ulnar nerve
The dorsal interossei are innervated by the deep branch of the ulnar nerve and function to abduct the fingers.
Question 6: At a node of Ranvier, the action potential jumps from one node to the next in a process called:
- Continuous conduction
- Saltatory conduction (Correct answer)
- Ephaptic transmission
- Antidromic conduction
Correct answer: Saltatory conduction
Saltatory conduction describes the jumping of the action potential between nodes of Ranvier, greatly increasing conduction velocity.
ABEM ABEM Anatomy & Neurophysiology 1
Which ion channel is primarily responsible for the upstroke of a nerve action potential?