Unit 5 Lecture 35

Question 1

What are the two parts to making an Action Potentials?

Answer 1

• neurons must be an “excitable cells”
• principal mechanism used = voltage-gated Na channel

Question 2

Explain excited cells

Answer 2

cells that can change membrane potential to generate an electrical signals

Question 3

What is the 1st step in the generation of action potentials

Answer 3

1. Local change in membrane potential

Question 4

Two types of local charges

Answer 4

Depolarization and Hyperpolarization

Question 5

Define depolarization

Answer 5

Membrane potential difference gets less negative

(Na+ enters cells through opened voltage gated channels)

Question 6

Define hyperpolarization

Answer 6

Membrane potential difference gets more negative

(K+ leaves membrane through leak channel)

Question 7

What starts action potentials?

Answer 7

Local Depolarization

Question 8

Characteristics of action potentials

Answer 8

• Use voltage gated Na+ and K+ channels
• All or none (100 mV)
• Fast over long distances
• Depolarized -> repolarized -> resting phase

Question 9

Characteristics of graded potentials

Answer 9

• Occur in dendrite and cell body
• Chemical (ligand) and mechanically gated channels
• NOT all or none (size varies w strength of stimuli)

Question 10

What are the two types of graded potentials?

Answer 10

1. Inhibitory Post-Synaptic Potentials (IPSP)
2. Excitation Post-Synaptic Potentials (EPSP)

Question 11

Define inhibatory post-synaptic potentials

Answer 11

Decreases the liklihood of post-synaptic action potentials occuring

Question 12

Define excitatory post-synaptic potentials

Answer 12

Increasees the likelihood of post-synaptic action potentials occuring

Question 13

2nd step in the generation of action potentials

Answer 13

POSITIVE FEEDBACK CYCLE

Question 14

Descirbe the positive feedback cycle

Answer 14

1. Membrane is depolarized to threshold
2. Opens voltage gated Na+ channels
3. More Na+ comes in cell
4. Depolarized even more (less negative)
5. More Na+ channels open

Question 15

What is the threshold in an action potential?

Answer 15

~ -50 mV

Question 16

3rd step in the generation of action potentials

Answer 16

Reaches critical point

• Na+ channels close (inactivation)

Question 17

4th step in the generation of action potentials

Answer 17

Depolarzation also (slowly) opens voltage gated K+ channels

Question 18

What happens when the voltage gated Na+ channels are inactivated and the voltage gated K+ channels are opened?

Answer 18

Repolarization (gets more negative) towards resting value

Question 19

Define refractory period

Answer 19

Periods during which it is hard to create a second action potential

Question 20

What are the two types of refractory periods?

Answer 20

1. Absolute refractory period
2. Relative refractory period

Question 21

Define absolute refractory period

Answer 21

• Whole peak region on AP graphs

After closing Na+ channels, membrane CAN’T be restimulated to make AP

(resetting Na+ channels)

Question 22

Define relative refractory period

Answer 22

Period basically after threshold where new AP can be produced but it takes LONGER than normal

Question 23

Why are refractory periods important

Answer 23

1. Makes max rate action potential
2. Influences forward propagation from axon hilock to axon terminal