Lab assignment 1: CAPs

Question 1

describe the differences between CAPs and APs with respect to amplitude and number of neurons

Answer 1

CAP - lower amplitude, many neurons

AP - larger amplitude, one neuron

Question 2

in a CAP measurement experiment, why is the nerve wet but not immersed?

Answer 2

the nerve is wet to allow external ∆V to be observed and measured, but not immersed so that the signal does not dissipate quickly into the surrounding fluid

Question 3

why doesn’t the response of a nerve follow the all-or-none law of a neuron?

Answer 3

a nerve displays a CAP, a summation of APs of individual neurons
-therefore some APs may be initiated while some are not (diff properties of each neuron), until the stimulus is great enough to activate all APs and reach max CAP

Question 4

supramaximal CAP stimulus

Answer 4

stimulus ∆V greater than the ∆V necessary to produce CAP max

Question 5

what determines the maximum frequency of firing in an axon?

Answer 5

absolute refractory period length

Question 6

list 3 major factors that affect conduction velocity

Answer 6

• myelenation
• axon diameter
• temperature

Question 7

how does local anesthetic that blocks voltage gated Na+ channels affect a CAP?

Answer 7

• CAP amplitude decreases (fewer neurons reach threshold)

- mean conduction velocity decreases and distribution widens (Rm up, τ up, λ up)