6.5 Synaptic transmission

Question 1

what is a synapse

Answer 1

junction between neuron and another neuron or neuron and an effector cell

Question 2

synaptic cleft

Answer 2

gap between cells at a synapse

Question 3

synaptic knob

Answer 3

swelling in presynaptic neuron

Question 4

where are synaptic vesicles found

Answer 4

synaptic knob

Question 5

what do synaptic vesicles contain

Answer 5

neurotransmitters

Question 6

what happens when an action potential reaches the end of a neuron

Answer 6

neurotransmitters are real eased into synaptic cleft

Question 7

what happens after neurotransmitters are released

Answer 7

diffuse across to postsynaptic membrane and bind to specific receptors

Question 8

what happens when neurotransmitters bind to receptors

Answer 8

action potential
muscle contraction
hormone secretion

Question 9

what does acetylcholine bind to

Answer 9

cholinergic receptors

Question 10

why are impulses unidirectional

Answer 10

receptors are only on post synaptic membrane so can only travel in one direction

Question 11

how is nerve impulse sent across a cholonergix synapse

Answer 11

• action potential at synaptic onob of presynaptic neuron triggers voltage gated CA2+ channel to open
• Ca2+ diffuses into synaptic onob
• causes synaptic vesicles to fuse with presynaptic membrane
• vesicles release acetylcholine into synaptic cleft (exocytosis)
• acetylcholine diffuses across synaptic cleft, binds to specific cholinergic receptors on postsynaptic membrane
• Na+ channels in postsynaptic open, influx of Na+ causes depolarisation
• if threshold reached > action potential generated
• acetylcholine hydrolysed by acetylcholinesterase
• acetate and choline reabsorbed imto presynaptic neuron and used to make more ACH

Question 12

do the calcium ions move into or out of synaptic knob

Answer 12

INTO

Question 13

what is exocytosis

Answer 13

processes by which a vesicle inside a cell moves to
the cell-surface membrane, fuses with the membrane and releases its
contents outside the cell

Question 14

what do excitatory neurotransmitters do

Answer 14

depolarise the postsynaptic membrane
> action potential fired if threshold is reached

Question 15

is acetylcholine excitatory or inhibitory

Answer 15

excitatory (in cholinergic synapses in CNS and neuromuscular junctions)

Question 16

what is GABA

Answer 16

Inhibitatory neurotransmetteurs

Question 17

what do inhibitory neurotransmitters do

Answer 17

hyperpolarise post synaptic membrane preventing it from firing an action potential

Question 18

what does GABA do

Answer 18

when it
binds to its receptors it causes potassium ion
channels to open on the postsynaptic membrane,
hyperpolarising the neurone.

Question 19

when can acetylcholine act as an inhibitory

Answer 19

cholinergic synapses in the
heart.
> can cause
potassium ion channels to open on the
postsynaptic membrane, hyperpolarising it

Question 20

what is an inhibitory synapse

Answer 20

synapse where inhibitatory neurotransmitters are released from presynaptic membranes

Question 21

what is summation

Answer 21

Effect of neurotransmitters released from many neurons is added together
___ sum of total lots of smaller impulses triggers an action potential fired

Question 22

two types of summation

Answer 22

spatial
temporal

Question 23

what is spatial summation

Answer 23

two or more presynaptic neurons release their neurotransmitters at the same time onto the same post synaptic neuron
— small amount can be enough to reach threshold in postsynaptic and trigger an action potential

Question 24

what happens if some neurons release an inhibitory neurotransmitter

Answer 24

total effect of all neurotransmitters may be no action potential

Question 25

what is temporal

Answer 25

where two or more nerve impulses arrive in quick succession from the same presynaptic neuron - makes action potential more likely as neurotransmitter released into synaptic cleft

Question 26

why do impulses have to follow eachother quickly

Answer 26

neurotransmitter will be removed from the cleft before it’s reached threshold lebel to trigger action potential

Question 27

what is a neuromuscular junction

Answer 27

specialised cholinergic synapse between a motor neuron and a muscular cell

Question 28

what do neuromuscular junctions use

Answer 28

acetylcholine which binds to nicotinic cholinergic receptors

Question 29

compare cholinergic and neuromuscular

Answer 29

neromuscular : motor neuron and muscle fibre, main function is to stimulate muscle contraction cholinergic : between two neurons, used to transmit signals for various functions

Question 30

differences between neuromuscular junction and cholinergic

Answer 30

in neuromuscular - postsynaptic membrane has clefts which store acetylcholinesterase - postsynaptic has more receptors - acetylcholine is always excitatory

Question 31

similarities between neuromuscular and cholinergic

Answer 31

- both release acetylcholine from vesicles in the presynaptic membrane - then diffuses across the synaptic cleft and binds to cholinergic receptors on postsynaptic membrane, this triggers an action potential if the threshold is reached - acetylcholine broken down by acetylcholinesterase in both

Question 33

how do agonists affect synapses

Answer 33

same shape as neurotransmitters so they mimic their action at receptors - more receptors are activated

Question 34

how do antagonists affect synapses

Answer 34

block receptors so they can’t be activated by neurotransmitters so fewer receptors can be activated

Question 35

what do drugs that inhibit the enzyme that breaks down neurotransmitters do

Answer 35

more neurotransmitters in synaptic cleft to bind to receptors and they are there for longer

Question 36

what do drugs that stimulate the release of neurotransmitters do

Answer 36

more receptors activated

Question 37

what do drigs that inhibit the release of neurotransmitters

Answer 37

fewer receptors activated

Question 38

what is endogenous

Answer 38

produced naturally by the body

Question 39

what is an autoimmune disease

Answer 39

persons immune system mistakes their own cells for for pathogens so it starts to attack them