synapses

Question 1

what are the different types of synapse

Answer 1

1) electrical- a gap junction small enough that an electrical impulse is transmitted directly from one neurone to the next
2) chemical- impulse transmitted via a neurotransmitter that diffuses across the synaptic cleft from the presynaptic membrane to the post synaptic membrane

Question 2

define neurotransmitter

Answer 2

a chemical secreted in response to an action potential which carries a chemical signal across the synapse helping to initiate a new action potential

Question 3

outline synaptic transmission

Answer 3

1) the arrival of an action potential at the axon terminal causes calcium ion gated channels to open and calcium ions to flood in down the conc gradients
2) the influx of calcium ions causes synaptic vesicles to migrate and fuse to the presynaptic membrane and release neurotransmitter acetylcholine via exocytosis
3) the NT diffuses down the conc gradient across the synaptic cleft and binds to specific receptor
4) 2 acetylcholine needs to bind via cooperative binding
5) once bound the receptor protein changes shape opening the sodium ion gated channels causing depolarisation

Question 4

outline the reuptake of acetylcholine

Answer 4

1) it is broken down by acetylcholinesterase into choline and ethanoic acid
2) these diffuse back across the synaptic cleft to the presynaptic membrane and reform acetylcholine and are repackaged into vesicles

Question 5

how do neurones only transmit impulses in one direction

Answer 5

• synaptic vesicles only occur at presynaptic membrane
• move down conc gradient
• receptors only at post synaptic membrane

Question 6

what are the properties of synapsis

Answer 6

• transmit info between neurones
• pass impulses in one direction
• protect the response system from over stimulation
• filter out low level stimuli

Question 7

what is temporal summation

Answer 7

depolarisation builds up over time to reach threshold at which an action potential is initiated