What are some ways that drug-receptor interactions can influence neuronal firing?

Question 1

What is the driving force behind action potentials?

Answer 1

The fact that polar molecules are hyrdophyllic and lipophobic

Question 2

What are the main ions involved in action potentials?

Answer 2

1. potassium
2. sodium
3. chloride
4. Calcium
5. anions

Question 3

What is an anion?

Answer 3

Any negatively charged particle

Question 4

What are the two major forces that determine where ions will flow?

Answer 4

1. electrostatic forces (opposites attract, similars repel)

2. diffusion forces (an ion will want to go from an area of high concentration, to an area of low concentration)

Question 5

What are the different kinds of channels situated in the membrane of a neuron to aid with action potential firing?

Answer 5

1. potassium channels
2. voltage-gated sodium channels
3. voltage-gated potassium channels
4. sodium-potassium pump
5. voltage-gated calcium channels

Question 6

What happens when K+ flows out of the cell, via the potassium channels?

Answer 6

The net charge of the cell relative to the outside becomes negative (at approximately -80 mV)

Question 7

What is the equilibrium potential of potassium?

Answer 7

• 80 mV

- this is the charge at which no more K+ ions are flowing in or out of the cell

Question 8

When do the voltage-gated Na+ channels open?

Answer 8

When the membrane potential is at -40 mV

Question 9

What force(s) drive sodium into the cell?

Answer 9

Both electrostatic and diffusional forces

Question 10

To which potential does sodium cause the cell to rise to?

Answer 10

+40 mV

Question 11

When do the voltage-gated potassium channels open?

Answer 11

When the membrane potential is at +40mV

Question 12

What force(s) drive potassium out of the cell?

Answer 12

Both electrostatic and diffusional forces

Question 13

To which potential does potassium cause the cell to fall to?

Answer 13

-85mV

Question 14

When do the sodium-potassium pumps kick in? Why do they have to kick in?

Answer 14

When the membrane potential is at -85mV
- they have to kick in because the potassium channel is only SEMI permeable to K+, so the cell wouldn’t stabilize soon enough on its own

Question 15

What is the all-or-none law?

Answer 15

The law that states that an action potential either happens or it doesn’t; it can’t only get halfway

Question 16

What is the function of the axon hillock?

Answer 16

It connects the soma of the cell to the axon

Question 17

Approximately how many synapses can one neuron have?

Answer 17

In the hundreds of thousands

• each input is casting a vote to the all-or-nothing law
• the number of “votes” decides whether a cell will fire or not

Question 18

What is an undershoot?

Answer 18

Another word for hyperpolarization

Question 19

What is glutamate? What receptor does it bind to?

Answer 19

Glutamate is the main excitatory neurotransmitter in the brain
- glutamate binds to AMPA receptors (which are ligand-gated)

Question 20

What are AMPA receptors permeable to?

Answer 20

Both K+ and Na+

- thus, the net effect becomes positive, driving the cell closer towards an action potential

Question 21

What is GABA? Which receptor does it bind to?

Answer 21

GABA is the main inhibitory neurotransmitter in the brain

- GABA binds to the GABA(a) receptor, which is a ligand-gated ion channel

Question 22

What are GABA(a) receptors permeable to?

Answer 22

Chloride (Cl-)

- therefore, the net effect becomes negative, moving the cell further from generating an action potential

Question 23

What decides if a neuron will fire?

Answer 23

Which charge reaches the axon hillock first

Question 24

Why is phosphorylation of G-protein coupled receptors an important concept to remember when thinking about action potentials?

Answer 24

Because phosphorylation can either:

1. change the ion that the receptor is permeable to, or
2. affect transcription to increase or decrease the production of a receptor,

this means that G-protein coupled receptors can affect how easily a neuron will fire (acting like a sidekick to the excitatory or inhibitory neurotransmitters)

Question 25

What is excitotoxicity?

Answer 25

When a cell is so excited that it dies

Question 26

Why is it dangerous to consume alcohol while taking sleeping pills?

Answer 26

Because both act on GABA(a) receptors, decreasing the likelihood of action potentials significantly, leading to coma or death

Question 27

What is stroke damage due to?

Answer 27

When oxygen is depleted in the brain, glutamate is released uncontrollably, leading to excitotoxicity

Question 28

When do the voltage-gated Ca2+ channels open?

Answer 28

When an action potential reaches the terminal bouton

Question 29

What happens when a voltage-gated calcium channel opens?

Answer 29

It causes a second-messenger cascade to cause the vesicles in the terminal to migrate to the synaptic cleft, releasing neurotransmitters