W5

Question 1

Passive membrane qualities

What is the equation to calculate the length of a pasive electrical signal?

How do you make the signal travel further?

Answer 1

Decrease Rm (myelin)

Decrease Ri (big axons)

Question 2

What are some characteristics of the passive flow of current?

Answer 2

1. practically instant
2. signal fades very quickly

Question 3

What are the characteristics of active flow of current across the axon?

Answer 3

1. the strength of the signal stays the same
2. the speed is quite slow

Question 4

Why doesn’t the action potential travel backwards along the axon?

Answer 4

Because of the undershoot phase, which inhibits reactivation. Rrefraktärzeit.

Question 5

How do myelinated axons conduct action potential?

Answer 5

Through saltatory action potential.

1. current is conducted passivly over longer distances because of myelin coating
2. at nodes of Ranvier, action potential is actively stimulated.

Question 6

Speed of

a. vertibrate motor axon
b. pain axon
c. Squit axon
d. Crab axon

Answer 6

a. 70-120m-s
b. 0.5-2m/s
c. 20m/s
d. 3m/s

Question 7

Toxins which affect ion channels channels.

Answer 7

Tetrodotoxin (Fugu rubipres) blocks K+ channels

Kegelschnecke (conus mediterraneus)

Question 8

What are the four funtional groups of ion channels?

Answer 8

1. current gated channels - resting and action potential
2. Ligand gated channels - Postsynaptic potential
3. current and ligand gated channels - NMDA
4. Temperature and stretch sensitive