EX344 S2025 Exam 3 Study Guide

Cell body

Contains the nucleus of a neuron.

Dendrites

Conduct impulses toward the cell body of a neuron.

Axon

Carries electrical impulses away from the cell body, may be covered in Schwann cells.

Schwann cells

Form a discontinuous myelin sheath along the axon.

Synapse

Contact points between the axon of one neuron and the dendrite of another neuron.

Sensory division

Afferent fibers that transmit impulses from receptors to the central nervous system (CNS).

Motor division

Efferent fibers that transmit impulses from the CNS to effector organs.

Irritability

The ability to respond to a stimulus and trigger a neural impulse.

Resting membrane potential

The electrical charge of a neuron when it is not active, typically -70mV.

Action potential occurs when …

a stimulus of sufficient strength depolarizes the neuron.

Repolarization

The return to resting membrane potential after depolarization.

All-or-none principle

Once a nerve impulse is initiated, it will travel the length of the neuron.

Excitatory postsynaptic potentials (EPSP)

Promote neural depolarization, summing several EPSPs can lead to an action potential.

Inhibitory postsynaptic potentials (IPSP)

Cause hyperpolarization, making it more difficult for a neuron to fire an action potential.

Joint proprioceptors

Receptors that provide the CNS with information about body position, located in joints and muscles.

Golgi tendon organ

Monitors force production in a muscle and helps prevent injuries.

Muscle spindle

Provides feedback about muscle length and rate of shortening.

Motor unit

A motor neuron and all the muscle fibers it innervates.

Innervation ratio

The number of muscle fibers per motor neuron.

Type S motor unit

Slow motor unit composed of type I fibers.

Type FR motor unit

Fast, fatigue-resistant motor unit composed of type IIa fibers.

Type FF motor unit

Fast, fatiguable motor unit composed of type IIb fibers.

Sliding filament theory

Mechanism explaining muscle contraction through the sliding of myofilaments (actin and myosin).

Acetylcholine

Neurotransmitter released from motor neurons that triggers muscle contraction.

Excitation-contraction coupling

Process by which an action potential in a muscle fiber leads to muscle contraction.

Postactivation potentiation

A phenomenon where previous muscle contractions enhance subsequent contraction performance.

Chronic traumatic encephalopathy (CTE)

Degenerative brain disease associated with repeated trauma, leading to neuronal death and axon loss.

Withdrawal reflex

A reflex that removes a limb from a painful stimulus.

conductivity

transmission of the impulse along as axon

an action potential

Opens Na+ channels, and Na+ diffuses into cell. Inside becomes more positive

free nerve endings

most abundant type of joint proprioceptors, sensitive to touch and pressure

golgi-type receptors

found in ligaments and around joints, functionally similar to nerve endings

Pacinian corpuscles

located around joints, detect rate of joint rotation

intrafusal fibers

thin muscle cells, run parallel to normal fibers

extrafusal fibers

normal fibers

gamma motor neurons

stimulate intrafusal fibers to contract in concert with extrafusal fibers

GTOs

monitor force development in muscle, can prevent muscle injury during excessive force generation

spinal cord

motor neurons are located on the …

motor neurons

carry neural messages from the spinal cord to skeletal muscles

recruitment pattern

type I->type IIa->type IIb

the size principle

the “orderly recruitment of motor units during exercise” (smallest MUs 1^st )

components of the brainstem

midbrain, medulla oblongata, and pons

low ratio

in muscles involved in the fine motor control (23/1)

higher ratio

in muscles that do not require fine motor control (1000/1)

motor unit recruitment

recruitment of additional muscle fibers by activating more muscle units

spinal tuning

refers to neural networks within spinal cord that refine voluntary movement after receiving messages from higher brain centers

kinesthesia

awareness of the position and movement of the parts of the body by means of sensory organs (proprioceptors) in the muscles and joints.