Lecture 5 - action potential

Question 1

What is action potential?

Answer 1

• electrical impulses send signals
• temporary shift in membrane (elec.) potential
• causes the release of NTs

Question 2

What causes action potential?

Answer 2

• it starts when a NT binds to the receptor

Question 3

What is the voltage change for action potential?

Answer 3

-70mV to +50mV

Question 4

At what charge do Na+ channels open?

Answer 4

-50mV (negative 50)

Question 5

What happens when Na+ channels open?

Answer 5

The cell gets really positive really fast

Question 6

At what voltage do K+ channels open up?

Answer 6

+50mV

Question 7

What is the axon hillock?

Answer 7

Where all the electrical energy in the cell ends up to determine if there will be an action potential propagating through (moving along) the axon

Question 8

What happens when the action potential reaches the terminal?

Answer 8

• It causes the release of NTs from the terminals
• The NT does not enter the new cell, it just binds to the receptor
• Opens ion channel for the new neuron
• in the membrane of the terminal, there are Ca++ voltage-gated channels
• Action potential activates Ca++ channels
• when the Ca++ channels open, the terminal membrane and vesicle membrane blend together/fuse
• NT binds to receptor

Question 9

The pufferfish contains tetradotoxin, this toxin blocks Na+ voltage-gated channels what will happen to the action potential? What will happen to the transmission in the neuron?

Answer 9

If the Na+ voltage-gated channels can’t open, action potential can’t occur. There will be no transmission in the neuron

Question 10

Draw an action potential indicating what causes the changes in charge (eg Na+ goes in…)

Answer 10

• at -50mV, Na+ goes in, neuron shoots up (positive)
• at +50mV, K+ channels open, K+ goes out, cell becomes super negative

Question 11

Draw an action potential indicating what causes the changes in charge (eg Na+ goes in…)

Answer 11

• at -50mV, Na+ goes in, neuron shoots up (positive)
  –> Depolarizing phase
• at +50mV, K+ channels open, K+ goes out, cell becomes super negative
  –> Repolarizing phase
• cell temporarily gets lower than -70mV
  –> undershoot

Question 12

Where in the neuron is action potential generated? Why this location?

Answer 12

• Action potential only happens at the nodes of ranvier
• It happens at the nodes because…
  
  1. that’s the only place on the axon where there
     isn’t myelin
  2. that’s the only place where there are voltage-
     gated channels

Question 13

The action potential starts in the axon hillock. Why does it start in the AH and not dendrites?

Answer 13

• Dendrites DO NOT have voltage-gated channels
• AH DOES have voltage-gated channels

Question 14

What causes the release of NTs? What happens to the NTs after they’re released? What happens after that?

Answer 14

• at the membrane of the terminal, there are Ca++ channels
• they open up, which causes the membrane to blend/fuse
• the NT crosses the synapse and binds to the receptor of the post-synaptic neuron
• the NT causes ion channels to open on the post-synaptic neuron, which changes its charge
  –> can make it generate its own action potential
  –> can make the neuron inhibited

Question 15

List 3 characteristics of a substance to be classified as a NT

Answer 15

1. it must be created by and stored in a neuron
2. it must be the only thing causing the reaction
   –> If you experimentally put only the neurotransmitter on the receptor, the postsynaptic cell would respond the same way
3. it must be able to return to the original neuron
4. it must be released when the neuron is excited

Question 16

List the 5 types of NTs

Answer 16

1. Amino acids.
2. Amines.
3. Acetylcholine (Ach.)
4. Peptides.
5. Non-traditional.

Question 17

What is DA? What type of NT?

Answer 17

Dopamine
Amines –> monoamine

Question 18

What is NE? What type of NT?

Answer 18

norepinephrine
Amines –> monoamine

Question 19

What is 5-HT? What type of NT?

Answer 19

Seratonin
Amines

Question 20

What is GABA? What type of NT?

Answer 20

Gamma-AMINO butyric Acid
Amino acid

Question 21

What type of NT is ACh?

Answer 21

Acetylcholine

Question 22

What does ACh affect? What problem is associated with it?

Answer 22

Memory and muscular contractions
Alzheimers

Question 23

What problem is associated with monoamines?

Answer 23

Key cause of mental illness

Question 24

What does dopamine affect? What problem is associated with it?

Answer 24

Affect:
1. motivation and reward
2. emotions
3. motor control
Problems:
- Schizophrenia
- Parkinson’s

Question 25

What does norepinephrine affect/problems?

Answer 25

- mood states - attention - fight or flight

Question 26

What does seratonin affect?

Answer 26

- patterns of sleep - mood levels

Question 27

What does GABA do?

Answer 27

Universal inhibitory NT (anti-anxiety)

Question 28

What does Glutamate do?

Answer 28

Universal excitatory NT (learning and memory)

Question 29

Match the columns a. GABA 1. Alzheimer's disease b. 5-HT 2. Sleep pattern c. DA 3. Parkinson's disease d. NE 4. Inhibitory NT e. ACh 5. Attention

Answer 29

a. GABA --> 4. Inhibitory NT b. 5-HT --> 2. Sleep pattern (seratonin) c. DA --> 3. Parkinson's disease d. NE --> 5. Attention e. ACh --> 1. Alzheimer's disease

Question 30

Some medications for Parkinson’s have been shown to affect emotions. What would that be the case?

Answer 30

Parkinson's medications increase dopamine all over the place, not just the specific pathway that needs it. This can elevate mood as well as increase likelihood of addiction in general