Nervous System and Neuron Physiology

What is the sequence of information flow in the nervous system?

Stimulus → sensory receptor → afferent neuron → CNS (integration) → efferent neuron → effector

What event occurs when an action potential reaches the axon terminal?

Neurotransmitters are released

What determines if a post-synaptic neuron will fire?

Whether the threshold is reached

Which cells are responsible for myelination in the PNS and CNS respectively?

Schwann cells (PNS) and oligodendrocytes (CNS)

How does myelin increase the speed of nerve impulses?

By allowing the impulse to jump from node to node, known as saltatory conduction

What two factors establish the resting membrane potential?

Unequal ion distribution and membrane permeability

What is the typical ion distribution at rest?

Na⁺ is concentrated outside, while K⁺ is concentrated inside

What is the function of the Na⁺/K⁺ pump?

It uses ATP to move 3 Na⁺ out and 2 K⁺ in to maintain resting potential

What is the threshold voltage required to trigger an action potential?

-55 mV

What ion movement characterizes depolarization?

Na⁺ channels open and Na⁺ enters the cell

What ion movement characterizes repolarization?

K⁺ channels open and K⁺ exits the cell

What occurs during hyperpolarization?

The membrane potential becomes more negative than the resting state

What is the correct chronological order of an action potential?

Resting → stimulus → depolarization → repolarization → hyperpolarization → resting

How does an action potential propagate along an unmyelinated axon?

Local currents trigger adjacent segments of the membrane

What is the difference between absolute and relative refractory periods?

Absolute: neuron cannot fire; Relative: neuron requires a stronger stimulus to fire

How does the PNS respond to axon injury?

The distal part degenerates and Schwann cells guide the regrowth

Why is CNS nerve regeneration limited?

Lack of a neurilemma or guiding structure

Which ion movement makes the interior of the neuron more positive?

Na⁺ entering

Which ion movement restores the negative charge of the neuron?

K⁺ leaving

Why is an action potential described as 'all-or-none'?

It only occurs if the threshold is reached; otherwise, nothing happens