Neuronal signalling

Question 1

The equilibrium potential of Na+

Answer 1

+60 mV

Question 2

The equilibrium potential of Cl-

Answer 2

-40 mV

Question 3

The equilibrium potential of K+

Answer 3

-90 mV

Question 4

The equilibrium potential of Ca2+

Answer 4

+123 mV

Question 5

Equilibrium potential

Answer 5

The voltage of the membrane which a specific ion prefers to stay at.

Question 6

Describe an action potential.

Answer 6

1. Resting potential: -70 mV
   The axon membrane is the most permeable to K+.
2. Trigger:
   A stimulus causes depolarisation which makes membrane potential less negative. If threshold potential is exceeded, this increase depolarisation= positive feedback.
3. Depolarisation:
   Membrane potential becomes more positive which triggers the opening of all gated Na+ channels. Na+ diffuses into the neurone which increase Vm to +40 mV.
4. Repolarisation:
   Gated Na+ channels are inactivated which prevents Na+ from entering the cell. Delayed rectifier K+ channels open. K+ diffuses out of the cell, which makes Vm more negative.
5. Hyperpolarisation/ Refractory period:
   Vm gets closer to the equilibrium potential of K+ (-90 mV), becomes more negative than resting potential. This prevents any further action potentials being generated.
6. Resting potential re-established:
   K+ finally shut and the K+/ Na+- ATPase restore resting potential.

Question 7

Describe the molecular lifecycle of a neurotransmitter.

Answer 7

1. It is packaged into a vesicle. This vesicle fuses with the presynaptic plasma membrane.
2. NT is released across synaptic cleft via exocytosis. NT diffuses across the synaptic cleft to the postsynaptic plasma membrane.
3. NT binds to a specific receptor on the membrane. Triggers an excitatory or inhibitory response in postsynaptic neurone.
4. Removal of NT: Enzyme breaks down NT or NT is taken into the presynaptic neurone via transporter protein.

Question 8

Inhibitor that prevents reuptake of serotonin.

Answer 8

Selective serotonin reuptake inhibitor:

Typically used as an antidepressant drug which allows serotonin to stay in the synapatic cleft for longer.

Question 9

Neurotransmitter

Answer 9

An endogenous chemical, released extracellularly by a neurone across a synapse, used to signal to other specific cells.

Can be small molecules or proteins/ peptides/ large molecules

Question 10

Small molecular neurotransmitters

Answer 10

Include:

• Amino acids: i.e glutamate
• Monoamines: i.e dopamine
• Acetylcholine

Question 11

Catecholamines

Answer 11

Family of monoamine neurotransmitters.

Includes:
Dopamine
Noradrenaline
Adrenaline.

Question 12

Dopamine

Answer 12

A catecholamine neurotransmitter that is derived from the amino acid tyrosine.

Low levels is associated with Parkinson’s disease. Dopamine against (activated dopamine receptors) are used to treat Parkinson’s.