Topic 3: Nervous System 1 - Neuronal Physiology: AP Propagation Flashcards
1
Q
What is AP propagation?
A
- to act as a communication device, an AP must be propagated along the axon’s entire length
2
Q
What occurs in AP propagation? (3 steps, 4 points)
A
- depolarization during AP (Na in) means positive ions move toward more negative on adjacent membrane
- then adjacent membrane depolarizes to reach threshold (voltage-gated Na+ open) to get AP on adjacent membrane
- movement of charge occurs in both directions, but AP moves in one direction because preceding membrane is in the absolute refractory period
- therefore get sequence of APs along membrane, each one at a time
3
Q
Where does an AP propagate to?
A
- along its entire length to the axon terminal ends
4
Q
What does the rate of propagation depend on? (2)
A
- fiber (axon) diameter
- myelination
5
Q
Why does fiber diameter determine rate of propagation?
A
- larger diameter means faster propagation because less resistance to ion flow (current)
6
Q
Why does myelination determine rate of propagation (4)
A
- unmyelinated fibers means APS all along the fiber where Na+ channels are adjacent to each other
- continuous conduction, hence slower - myelinated fibers means that AP occurs at Nodes of Ranvier where ion channels only present
- saltatory (leaping) conduction, hence fast
7
Q
What are the two fiber types?
A
- Type A and Type C
8
Q
What are characteristics of type A fibers? (3)
A
- large diameter
- myelinated
- propagates AP @ 130m/sec
9
Q
Which neurons are type A fibers, and what is the effector?
A
- sensory and motor neurons to skeletal muscles
10
Q
What are characteristics of type C fibers? (3)
A
- small diameters
- unmyelinated
- propagates APs @ 0.5 m/s
11
Q
Which divisions of the nervous system are type C fibers found, and in what fibers?
A
- Autonomic NS
- some pain fibers
12
Q
GP and AP comparison chart
A
