13.5 Synapses Flashcards
what is a synapse?
the junction between two neurones
what is a cholinergic synapse?
synapse between a motor neurone and an effector
what chemicals are used to transmit an impulse across a synapse?
neurotransmitters
what is the synaptic cleft?
gap between the axon of one neurone and the dendrite of the other neurone
what is the presynaptic neurone?
neurone which carries the impulse to the synapse
what is the postsynaptic neurone?
neurone which recieves the impulse from the synapse
what is the synaptic knob?
swollen end of presynaptic neurone which contains mitochondria and ER in order to produce neurotransmitters
what are the synaptic vesicles?
vesicles which contain neurotransmitters which fuse with the presynaptic membrane and undergo exocytosis
what two types of neurotransmitters are there?
excitatory
inhibitory
what are excitatory neurotransmitters?
cause the depolarisation of the postsynaptic neurone and cause an action potential to be generated once a threshold is passed
what is an example of an excitatory neurotransmitter?
acetylcholine
what are inhibtory neurotransmitters?
cause the hyperpolarisation of the postsynaptic membrane which prevents an action potential from being generated
what is an example of a inhibitory neurone?
GABA
how does an action potential cross a synapse?
action potential reaches the end of the presynaptic knob
depolarisation of the presynaptic membrane causes Ca2+ channels to open
Ca2+ ions diffuse in which causes vesicles containing the neurotransmitter to fuse with the membrane and release the neurotransmitter by exocytosis
the neurotransmitter diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane causing Na+ channels to open
Na+ ions diffuse in to the postsynaptic neurone which triggers the action potential
what happens to the neurotransmitters left in the receptors?
enzymes break them down and they are taken back to the presynaptic knob
why is it important to remove the neurotransmitters from the receptors?
prevents the action potential being generated again
what enzyme breaks down acetylcholine?
acetylcholinesterase
what does acetylcholinesterase break acetylcholine into?
ethanoic acid and choline
what is summation?
when an action potential is generated once the threshold is passed
what are the types of summation?
temporal
spatial
what is spatial summation?
when many neurones go into one neurone in order to pass the threshold and generate an action potential
what is temporal summation?
when one neurone produces more neurotransmitters over a short period of time in order to pass the threshold and generate an action potential
what is the role of synapses
ensure impulses are unidirectional
allow for an impulse from one neurone to reach multiple neurones
allow for multiple impulses from multiple neurones to reach a neurone
why do synapses ensure unidirectional flow?
neurotransmitter receptors are only found in the postsynaptic membrane so an impulse can only travel from the presynaptic to the postsynaptic
