Neurophysiology Exam Clinical Ex Phys

What are the three main structures of a neuron, and what is the function of each?

dendrites, axon, and the cell body

True or False: Afferent neurons carry signals from the central nervous system to muscles, while

efferent neurons carry signals from receptors to the central nervous system.

False

What structural change often occurs in neurons during Multiple Sclerosis that interferes with fast

action potential conduction?

Destruction of the myelin sheath, demyelination

Why is the resting membrane potential of a neuron typically around -70 mV?

The membrane is selectively permeable to ions

Explain the different phases of an action potential in terms of ion movement and channel activity.

Explain what the “all-or-none” principle means in relation to action potential generation.

The all or none principle means that once a stimulus reaches a certain threshold, it will either produce maximal action potential, or none at all

What is the definition of a motor unit?

a single motor neuron and all of the muscle fibers it controls

Walk through the sequence of events that occur at the neuromuscular junction leading to a muscle

action potential.

True or False: The dorsal horns of the spinal cord contain motor neurons, while the ventral horns

contain sensory neurons

False

Where do corticospinal tract axons cross, and what type of movement do they primarily control?

The pyramidal decussation in the lower medulla of the brainstem. Precise, skilled, and voluntary fine movements

True or False: Dual innervation means that most organs receive input from both the sympathetic

and parasympathetic nervous systems, often with opposing effects.

True

True or False: Only motor neurons depolarize and generate an action potential; sensory neurons

use a different mechanism.

False

True or False: Smaller muscles with fine control rely more on rate coding than motor unit

recruitment to regulate force

True

When muscles contract strongly, how do the Golgi tendon organs respond, and what reflexes do

they produce?

They rapid fire action potentials along type 1B sensory fibers

What does Henneman’s size principle tell us about the order in which motor units are activated?

That motor units are recruited in an orderly sequence from smallest to largest as the demand for muscle force increases

Explain what rate coding is and how it helps regulate muscle force. In your answer, include how

the frequency-tension relationship contributes.

The rate or frequency that a motor neuron fires action potentials to its connected muscle fibers