Lecture 4: Nervous System 4

Question 1

The speed of impulse condition is determined primarily by which two factors?

Answer 1

1. The presence or absence of the myelin sheath

2. The diameter of the axon

Question 2

How does axon diameter influence propagation velocity of an AP?

Answer 2

• The larger the diameter of the axon the less resistance to ion flow, the faster the velocity
• Because cytoplasm offers resistance to ion flow

Question 3

Three types of axon fibers

Answer 3

Type A
Type B
Type C

Question 4

What are the largest fibers?

Answer 4

Type A (4-20 um)

Question 5

How quickly can Type A fibers carry action potentials?

Answer 5

300 mph

Question 6

What information do Type A fibers carry?

Answer 6

• Sensory info to CNS concerning position, balance, delicate touch, and pressure sensations from the surface of the skin
• Commands from motor neurons that control skeletal muscles

Question 7

What is the purpose of Type A fibers?

Answer 7

• Carry impulses about danger in the outside environment

- Exist where quick reaction might mean survival

Question 8

Type B fiber size

Answer 8

Diameters of 2-4 um

Question 9

Type B fiber speed

Answer 9

40 mph

Question 10

Type C fiber size

Answer 10

Under 2um

Question 11

Type C fiber speed

Answer 11

2 mph

Question 12

What fiber types are myelinated?

Answer 12

A and B

Question 13

What fiber types are unmyelinated?

Answer 13

C

Question 14

Purpose of fiber types B and C

Answer 14

Carry less urgent information concerning temperature, pain, general touch and pressure sensations to the CNS.

Question 15

Where do fiber types B and C carry instructions?

Answer 15

To smooth muscle, cardiac muscle, and glands

Question 16

Type B and C fibers are generally part of what system?

Answer 16

ANS

Question 17

Synapse

Answer 17

A site where information is transmitted from one cell to another