Cellular Neurophysiology

Question 1

What is the organisation of the Neural Cell Membrane?

Answer 1

Channels allow ions in and out of neuron
Channels can be open or closed

Question 2

What are the ion pumps?

Answer 2

In the channels, pumps push or pull ions inside or outside of the neuron

Question 3

What is the excitation threshold?

Answer 3

Neuron needs to be pushed so they reach the excitation threshold so the action potential can happen

Question 4

What are neurotransmitters?

Answer 4

Gap between axon and dendrite, the gap is called a synapse
Axon sends signal to dendrite via chemical messengers, called neuron transmitters
Dendrite receive neurotransmitters, becomes an electrical signal, which begins action potential

Question 5

What are glial cells?

Answer 5

Provide support to neurons
Regulate blood flow
Supply nutrients to neurons
Guide development
Guide neural migration and produce chemicals to stop it
they communicate with other glial cells but on a slower basis as it’s chemical

Question 6

What are ligand gated ion channels?

Answer 6

Type of postsynaptic receptor
Binds with neurontransmitter
Ion-channel which open to allow ions to pass through the membrane
Leads to either depolarization or hyperpolarization

Question 7

What are voltage gated ion channels?

Answer 7

In response to voltage (e.g. whether a cell is depolarized.)
Sodium channel and Potassium channel

Question 8

What is ATP?

Answer 8

Adenosine Triphosphate
Inside the cell
Attach to pump, release one phosphate to the channel which releases energy for the pump to work

Question 9

What is ADP?

Answer 9

Adenosine Diphosphate
The Adenosine Triphosphate after it’s lost one of its phosphates
di- 2 phosphates
tri- 3 phosphates

Question 10

What is a H gate?

Answer 10

Channels are always open
H-gate inactivates (‘‘closes’’) the channel. This is a block that is put in the way of the channel. Only happens for sodium channels

Question 11

What are myelin sheaths?

Answer 11

Myelin sheath speeds up communication between neurons
It surrounds the axon
Node of Ranvier: spaces between the myelin sheaths, it isn’t surrounded by the myelin sheath

Question 12

What triggers channels to open?

Answer 12

Channels are activated by different type of neurotransmitters, e.g. key and lock, there needs to be a match to open the channel
If the neurotransmitter doesn’t fit the channel stays closed
Neurotransmitters bind to sites on the receptive neuron

Question 13

What are presynaptic and postsynaptic cells?

Answer 13

Neurotransmitters are in the synaptic vesicles, which is in the presynaptic cell, released into the synapse, neurotransmitters are activated in the channels, the channels are located in the postsynaptic cell
Neurotransmitters are chemical signals

Question 14

What is stage 1 in action potentials?

Answer 14

To reach equilibrium, sodium channels allow ions inside the neuron, these are chemically activated
Outside (sodium) is positively charged, inside (potassium) negatively charged, so outside positively charged ions are going inside the neuron

Question 15

What happens in stage 2 (depolarizing) action potentials?

Answer 15

Excitation
Overshooting happens: more ions than needed are sent inside the neuron
Voltage increases
Majority of sodium is now inside the neuron

Question 16

What happens in stage 3 (repolarization) action potentials?

Answer 16

At this point, potassium channels open so sodium channels close, electrically activated, negatively charged potassium ions are let into the cell, and positively charged ions are let out
Voltage decreases
Undershoot also happens here: Now sodium ions are mostly inside, while potassium ions are outside

Question 17

What happens in stage 5 (the refractory period) in action potentials?

Answer 17

Neuron can’t be excited anymore during this period, neuron needs to go back to the resting potential to reach another action potential

Question 18

What happens in an electrical transmission?

Answer 18

No gap between the synaptic cells
Gap junctions: neuron membranes touch
Both neurons are isopotential, meaning electrical changes in one neuron are instantaneously reflected in the other neuron

Question 19

What is stage 4 (hyperpolarization) in action potentials?

Answer 19

Inhibition
The potential is negative because there are too many potassium ions
The potential is more negative than the resting state and the threshold which is required for triggering action potentials

Question 20

Why are electrical synapses useful?

Answer 20

When information needs to be conducted more quickly, chemical signals are slower

Question 21

What are spines in dendrites?

Answer 21

Knob at the end of the dendrite where the inputs are received from other neurons

Question 22

What is a resting potential?

Answer 22

More negatively charged on the inside, positively charged on the outside
Not actively signalling

Question 23

What is saltatory conduction?

Answer 23

Action potential jumps from one Node of Ranvier to the next Node of Ranvier

Question 24

What are axons?

Answer 24

Long projection from the cell body
Longest are motor neurons