3.6.2 Synapses Questions And Answers Review
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(synapses) inhibitory neurotransmitters - ANS-hyperpolarise postsynaptic membrane so
potential
... [Show More] difference is more negative, preventing an action potential from firing / eg
GABA opens Cl- channels so hyperpolarises membrane
(synapses) synapse definition - ANS-a junction between neurones and effectors
(synapses) process - ANS-action potential reaches pre-synaptic knob and triggers
release of neurotransmitters from vesicles / diffuse across synaptic cleft to post-synaptic
neurone or effector and bind to post-synaptic receptors where are converted back to
action potentials in an excitatory response, or have desired response at effector
(synapses) cholinergic synapses use - ANS-acetylecholine (ACh), which binds to
cholinergic receptors and causes a cholinergic synapse
(synapses) cholinergic synapses process - 1 arrival of action potential - ANS-action
potential arrives at synaptic knob of presynaptic neurone, stimulating voltage-gated
Ca2+ ion channels in presynaptic neurone to open / calcium ions diffuse into synaptic
knob - are later pumped out via active transport
(synapses) cholinergic synapses process - 2 fusion of vesicles - ANS-influx of calcium
ions into synaptic knob causes synaptic vesicles to fuse with presynaptic membrane /
vesicles release ACh into synaptic cleft via exocytosis
(synapses) cholinergic synapses process - 3 diffusion of ACh - ANS-ACh diffuses
across synaptic cleft and binds to specific, complementary cholinergic receptors on
post-synaptic membrane / sodium ion channels open and depolarisation occurs as an
influx Na+ ions move into post-synaptic / action potential fired if threshold is reached in
post-synaptic membrane / ACh removed from synaptic cleft so response is not
continuous / acetylcholinesterase (AChE) hydrolyses ACh and products are reabsorbed
by post-synaptic neurone, used to make ACh
(synapses) excitatory neurotransmitters - ANS-depolarise postsynaptic membrane, so
action potential occurs if the threshold is reached
(synapses) excitatory neurotransmitter example. CONTINUES... [Show Less]