Action of the transmitter substance on the postsynaptic neuron—function of receptor proteins. Types of receptors in the postsynaptic membrane

Question 1

mechanism - step 1

Answer 1

ARRIVAL OF ACTION POTENTIAL

the action potential travels along axon along its length to pre-synaptic membrane, this is where the processs begins

Question 2

mechanism - step 2

Answer 2

DEPOLARISATION

voltage gated calcium ion channel opens
due to action potential arriving at pre-synaptic membrane

calcium ions enter from extracellular fluid down electrochemical gradient into cell

Question 3

mechanism - step 3

Answer 3

CALCIUM SENSING PROTEINS

influx of Ca2+ into the cell is detected by calcium-sensing proteins such as synaptotagmin

these are part of vesicular membrane

synaptotagmin fuses with Ca2+ = conformnational changes

Question 4

mechanism - step 4

Answer 4

SYNAPTIC VESICLE DOCKING

synaptic vesicles are docked onto pre-synaptic membrane

via proteins involved in SNARE complex
- syntaxin
- SNAP-25
- synaptobevin

Question 5

mechanism - step 5

Answer 5

NEUROTRANSMITTER RELEASE

fusion of pre-synaptic membrane + vesicular membrane = exit via pore neurotransmitter release by exocytosis

across synaptic cleft to receptors on post-synaptic membrane via diffusion to reach post-synaptic membrane receptors

Question 6

mechanism - step 6

Answer 6

RESPONSE

• opening of ion channels
• activation of secondary messenger pathways

Question 7

mechanism - step 7

Answer 7

TERMINATION

1 - reuptake of neurotransmitter into pre-synaptic terminal by transporter protein

2 - enzymatic degradation in synaptic cleft

3 - diffusion of neurotransmitter away synaptic cleft

Question 8

Types of receptors in the postsynaptic membrane
EXAMPLE 1

Answer 8

ionotropic = ligand gated ion channels that open when neurotransmitter binds to it

• nicotnic Ach receptors for neurotransmitter of Ach to bind causing influx of na+ / ca2+ ions at neuromuscular junction for muscle contraction
• GABA_A = influx of cl- for inhibitory neurotransmission to the brain
• glutamate = NMDA/ AMPA await for glutamate to bind for excitatory neurotransmission

Question 9

Types of receptors in the postsynaptic membrane
EXAMPLE 2

Answer 9

METABTROPIC RECEPTORS = g-coupled protein receptors -> intracellular cascade events -> cell signalling transduction pathways

• muscarinic Ach receptors
• dopamine receptors

Question 10

Types of receptors in the postsynaptic membrane
EXAMPLE 3

Answer 10

tyrosine kinase
- synaptic plasticity
- growth factor signalling pathways

Question 11

Types of receptors in the postsynaptic membrane
EXAMPLE 4

Answer 11

NEUROPEPTIDE RECEPTORS

receptors + neuropeptide (substance P)
- pain transmission
- inflammatory response
- mood regulation

Question 12

Types of receptors in the postsynaptic membrane
EXAMPLE 5

Answer 12

CYTOKINE RECEPTORS
= immune response