HP Lab 3 Mean Nerve Conduction Velocity

Compound action potential (CAP)

• the sum of all the individual APs occurring in the nerve (or muscle) when it’s stimulated

• measured from the speed of conduction through a nerve or muscle

  • It appears as a composite waveform on the recording trace, where each “peak” reflects the contribution of a group of fibers that conduct at a similar speed.

  • Amplitude grows with a stronger stimulus because more axons are recruited.

  • Fast‑conducting fibers produce early peaks, while slower fibers add later components, giving the ______ its characteristic multi‑phasic shape.

fascicle

• A bundle of many individual axons (nerve fibers) that travel together within a peripheral nerve.

  • bundle of neurons wrapped with connective tissue

• bundle of ______ wrapped in connective tissue forms into neuron

internal resistance

friction as ions move through the cytoplasm of the axon

• It depends mainly on the axon’s diameter – a larger diameter provides a wider “pipe,” lowering ________

mean nerve conduction velocity

• the average speed at which an electrical impulse travels along a peripheral nerve, calculated from the difference in distance and latency between two stimulation points

• Velocity =  (distance between points (in meters)) / difference bet. deltaT_A and deltaT_B (in seconds)

membrane resistance

• flux across the membrane

• The resistance to ionic current flow across the axonal membrane (i.e., through the lipid bilayer and any insulating layers).

• Myelination = higher ______ = higher current down axon

nerve

• a bundle of fascicles wrapped with connective tissue

• carry sensory, motor, or mixed information, allowing muscles to contract, skin to feel, and organs to receive autonomic signals.

• Can be sensory neurons, motor neurons or both

• Cell bodies often clustered together

neuron

the fundamental signaling cell of the nervous system that transmits electrical and chemical information throughout the body.

• consists of a cell body (soma) containing the nucleus, dendrites that receive inputs, and a single axon that carries the output signal over long distances.

• Function: When the neuronal signaling cell reaches threshold, an action potential travels down the axon, releasing neurotransmitters at synaptic terminals to communicate with other neurons, muscles, or glands.

ulnar nerve

• Speed of conduction through a nerve or muscle can be measured by a compound action potential (CAP)

• Stimulate CAP in ulnar motor nerve → measure CAP of the abductor minimi digiti (quinti)

• a major peripheral nerve that originates from the spinal cord and travels down the arm (spinal muscle nerve of hand) to innervate muscles and skin of the forearm and hand.

  • Path: It runs along the medial side of the upper arm, passes posterior to the medial nerve of the elbow (the “funny bone” spot), then travels in the forearm to supply the hand’s intrinsic muscles.

  • Function: Provides muscle contraction to most of the small hand muscles (e.g., the abductor digiti minimi) and sensory innervation to the little finger and the ulnar side of the ring finger.