Cell Signaling 4

Question 1

What are neurons designed to do

Answer 1

Communication and information processing

Question 2

What are the electrical signals used to convey messages?

Answer 2

Action potentials

Question 3

What is the electrical potential difference across the membrane at rest? (Resting Membrane Potential)

Answer 3

-70 to -75 mV

Question 4

Where are the AP started?

Answer 4

Axon hillock

Question 5

What is skeletal muscle Resting Membrane Potential?

Answer 5

-90 mV

Question 6

What is the threshold for Hyperpolarization?

Answer 6

more than -85 mV

Question 7

What is the threshold for Depolarization?

Answer 7

Less than -50 mV

Question 8

Which Ion always has some channels open in the membrane?

Answer 8

K+

Question 9

Why is the negative charge concentrated at the inner surface of the membrane?

Answer 9

Because all of the large Anions want to leave the cell due to the electrochemical gradient….but they cannot get past the membrane and so they aggregate just inside it.

Question 10

What allows for the build up of the negative charge?

Answer 10

The release of K+ ions, hence the name K+ Diffusion Potential

Question 11

What is the E(k)?

Answer 11

The equilibrium potential for K+. It is when the negative charge inside the cell equals the pull of the chemical concentration gradient.

Question 12

What is the name of the equation that allows calculation of E(k)?

Answer 12

The Nernst Equation

Question 13

What is the Nernst Equation?

Answer 13

E(k) = RT/zF ln [K]o/[K]i

Question 14

What is the E(k) at 37 degrees C

Answer 14

-90 mV

Question 15

Which cells has an RMP that equals E(k) exactly?

Answer 15

Muscle Cells

Question 16

Why doesn’t the RMP = E(k) in Nerve Cells?

Answer 16

There is a slight inward migration of Na+ ions in Nerve cells that doesn’t occur in muscle cells

Question 17

What equation relates the permeability of the membrane to each ion?

Answer 17

Goldman Equation

Question 18

What happens if the extracellular [K] is increased by a lot?

Answer 18

Depolarization

Question 19

Why is it lethal to have way too much Potassium outside of the cell membrane?

Answer 19

If the membrane potential is lost no more APs can be made which means the nervous system is toast

Question 20

What is the Equilibrium potential for Na+ ions? E(Na)

Answer 20

+ 60 mV

Question 21

What is E(Cl)?

Answer 21

-70 mV

Question 22

Draw the AP Curve with Labels

Answer 22

Ok

Question 23

What is the threshold?

Answer 23

Level of depolarization when an impulse is initiated

Question 24

What does “all or none” refer to?

Answer 24

A stimulus will trigger a complete action potential or none at all

Question 25

What is the upstroke?

Answer 25

A rapid depolarization in membrane potential from resting values towards zero

Question 26

What does overshoot mean?

Answer 26

Reversal of the membrane potential during the peak of the AP

Question 27

What is the absolute refractory period?

Answer 27

Time following an AP during which a stimulus cannot elicit a second AP

Question 28

What is the relative refractory period?

Answer 28

Time during which only an extra strong stimulus can fire a second AP

Question 29

What is the status of the voltage gated Na channels at rest?

Answer 29

Channel is closed. K+ ions are flowing out of cell | Inactivation gate is open

Question 30

What is the status of the Na channel during the Activation State?

Answer 30

Activation Gate is OPEN Inactivation Gate is OPEN This the AP Upstroke

Question 31

What is the status of the Na channel during the Inactivation State?

Answer 31

Activation Gate is OPEN | Inactivation Gate is CLOSED

Question 32

What does the refractory period prevent?

Answer 32

One AP from being fired on top of the first APs from going backward Sets an upper limit to frequency at which a nerve can fire APs

Question 33

How does conduction velocity relate to the size of the neuron?

Answer 33

Velocity increases with the diameter of the axon