Lecture 2 -basic cellular neurophysiology

Question 1

What are the 2 types of cellular communication?

Answer 1

1. hormonal/autocrine signalling - uses chemical hormones and is slow, general, sustained and not very controlled.
2. neurotransmission/electrical - intracellular signalling through rapid changes of membrane potential and is fast, local, transient and accurate.

Question 2

Describe the resting membrane potential.

Answer 2

all cells have a potential difference across the cell membrane.
inside is negative to the outside.
an inactive neuron has a voltage across its membrane - RMP

Question 3

Describe the electrochemical gradient.

Answer 3

consists of 2 parts - the chemical gradient and the electrical gradient.

chemical gradient = concentration difference from the inside and outside of the cell. K can move outside down its chemical gradient due to leak channels. Na can’t move inside down its chemical gradient due to membrane impermeability.

electrical gradient = ionic charge different across the membrane. Na/K ATPase switches 3 Na for 2 K = increases negative charge on the inside of the cell.

Question 4

What is the Nernst equation for?

Answer 4

gives the equilibrium potential of an ion present on both sides of a membrane.

Question 5

What are the equilibrium potentials of Na, K and Cl?

Answer 5

Na = +60mV
K = -80mV
Cl = -65mV

Question 6

What is the Goldman equation for?

Answer 6

Nernst equation does not account the membrane is differentially impermeable to many ions, thus influencing the RMP.
RMP = sum of the equilibrium potentials of all ions.

Question 7

What phase of the action potential is the voltage-gated sodium channel responsible for?

Answer 7

depolarisation phase

Question 8

What phase of the action potential is the voltage gated potassium channel responsible for?

Answer 8

repolarisation phase

Question 9

What is the absolute refractory period?

Answer 9

the short time after an AP where the membrane is incapable of generating another AP

Question 10

Briefly describe the initiation of an action potential.

Answer 10

• stimulation of neurotransmitter receptors around the cell body causes small changes in membrane potential called excitatory postsynaptic potentials or inhibitory postsynaptic potentials.
• EPSP and IPSP occurring close in time summate at a threshold of -55mV - VGNaC open

Question 11

Where do action potentials start?

Answer 11

axon hillock

Question 12

What is the speed of the movement of each AP dependent on?

Answer 12

1. axon diameter
2. membrane resistance (myelination)

Question 13

What is neurotransmission?

Answer 13

a chemical or electrical signalling that occurs in junctions between neurons known as synapses

Question 14

Name the 5 main types of neurotransmitters and some examples of each.

Answer 14

1. amino acids - glutamate, GABA
2. amines - dopamine, noradrenaline, 5-HT
3. peptides - CRH, opioids, substance P
4. ATP
5. nitric oxide

Question 15

What are the 5 key stages of neurotransmission?

Answer 15

1. synthesis - synthesised in the cell body or close to the site of release.
2. storage - stored in synaptic vesicles to protect them from degradation.
3. release - via exocytosis of synaptic vesicles.
4. receptor interactions - binding of the transmitter to the receptor causes membrane and/or intracellular responses.
5. termination - most removed from the synaptic cleft by an active uptake process