Lecture 18 - Local, Thereshold And Action Potentials

Question 1

Stimulus - chemical neurotransmitter binds to ion channel
Channel changes shape (opens)
Ions cross membrane driven by their electrochemical gradient
Neurotransmitter unbinds causing channel to close

Answer 1

Chemically gated ion channel

Question 2

Stimulus - membrane depolarises to threshold range (eg -60 mV)
Channel changes shape (opens)
Ions cross membrane driven by their electrochemical gradient
Membrane threshold changes causing channel to inactivate or close

Answer 2

Voltage gated ion channel

Question 3

Stimulus - deformation of membrane
Channel changes shape (opens)
Ions cross membrane driven by their electrochemical gradient
When membrane returns to original shape the channel opens

Answer 3

Mechanically gated ion channel

Question 4

Change in a potential membrane voltage
at a localised area
of the dendrite or cell body membrane

Answer 4

Local potential

Question 5

How does a local potential occur?

Answer 5

Neurotransmitter binds to and opens chemically gated ion channels on dendrites/cell body and allows ions to move in or out

Question 6

Local potentials can be either which 2 things?

Answer 6

Excitatory (EPSP)
Inhibitory (IPSP)

Question 7

Which 2 ways are local potentials summated in?

Answer 7

Spatial summation
Temporal summation

Question 8

Summed input from multiple pre synaptic neurons

Answer 8

Spatial summation

Question 9

Summed input from repeated firing of one pre synaptic neuron

Answer 9

Temporal summation

Question 10

If there was less sodium inside the cell on the outside of the cell, which direction would the sodium go in if we opened these sodium channels?

Answer 10

Into the cell because there is a lot more sodium outside the membrane compared to inside

Question 11

If there was more potassium inside the cell and not as much on the outside of the cell, which direction would the potassium go in if we opened these potassium channels?

Answer 11

Out of the cell because there is a lot more potassium sitting inside the cell and not so much outside

Question 12

What are the 2 excitatory neurotransmitters?

Answer 12

Acetylcholine and Norepinephrine

Question 13

What is the inhibitory neurotransmitter?

Answer 13

GABA

Question 14

When at resting membrane potential, if we get more positive we are…

Answer 14

Depolarising

Question 15

When at resting membrane potential, if we get more negative we are…

Answer 15

Hyperpolarizing

Question 16

Summed input from multiple pre synaptic neurons

Answer 16

Spatial summation

Question 17

Input from one presynaptic neuron firing repeatedly

Answer 17

Temporal summation

Question 18

Why do we talk about pre synaptic inputs being summed at the axon hillock?

Answer 18

The axon hillock has a high density of voltage gated channels

Question 19

What is the “key” that opens voltage gated channels?

Answer 19

Threshold potential (-60mV)

Question 20

What is an action potential?

Answer 20

A change in membrane potential

Question 21

How do we get from -70mV to -60mV?

Answer 21

Chemical gates have to open and let sodium in through chemical gates and then they are summed up

Question 22

Once we get to -60mV, what can be opened?

Answer 22

Voltage gated channels

Question 23

When the membrane potential is not getting any more positive anymore what has caused this?

Answer 23

We have to have stopped sodium from going in by closing the activation gate

Question 24

Action potential step 1

Answer 24

Depolarisation to threshold

Question 25

Action potential step 2

Answer 25

Activation of sodium ion channels and rapid depolarisation

Question 26

Action potential step 3

Answer 26

Inactivation of sodium ion channels and activation of potassium ion channels

Question 27

Action potential step 3.5

Answer 27

Voltage gated sodium channels start to close

Question 28

Action potential step 4

Answer 28

Voltage gated potassium channels start to close

Question 29

Action potential step 5

Answer 29

Return back to resting membrane potential

Question 30

A channel ions move through when opened by binding of a chemical/neurotransmitter. Found in membrane of neural dendrites and cell body

Answer 30

Chemically gated ion channel

Question 31

A channel ions move through when opened at -60mV (threshold potential).
Found in membrane of axon hillock, axon, and axon terminals

Answer 31

Voltage gated ion channel

Question 32

Threshold potential is … and stimulates the opening of … ion gated channels

Answer 32

Threshold potential is -60mV and stimulates the opening of voltage gated ion channels

Question 33

What type of ion channel is found in the dendrites?

Answer 33

Mechanically gated ion channels

Question 34

What type of ion channel is found in the dendrites?

Answer 34

Chemically gated ion channel

Question 35

What type of ion channel is found in the axon membrane?

Answer 35

Voltage gated ion channels