module 5 - 13.5 synapses Flashcards
what is the synaptic cleft?
a gap that separates the axon of one neurone from the dendrite of the next neurone
what is involved in the structure of a synapse?
- synaptic cleft
- presynaptic neurone
- postsynaptic neurone
- synaptic knob
- synaptic vesicles
- neurotransmitter receptors
- voltage gated calcium ion channel proteins
what is the presynaptic neurone?
action potential (impulse) arrives at the synapse along its neurone
what is the postsynaptic neurone?
neurone that receives the neurotransmitter
what is the synaptic knob?
swollen end of the presynaptic neurone, with many mitochondria and extensive ER to synthesise neurotransmitters
what are the synaptic vesicles?
contain neurotransmitter that fuses with presynaptic membrane and diffuses into synaptic cleft
what are neurotransmitters that are sodium ion channel proteins?
specific protein molecules in postsynaptic plasma membrane where the transmitter will bind too
what does polarised mean?
more positive charge on outside than inside
what does depolarised mean?
more negative charge on outside than inside 1 (Na+ goes into cell)
what does repolarisation mean?
more positive goes out, more negative on inside (K+ goes out of cell)
what is an excitatory neurotransmitter/what does it do?
- cross synaptic cleft
- cause localised depolarisation of postsynaptic membrane, if this reaches threshold potential then action potential is initiated
- common in CNS and neurotransmitter junctions
- e.g. acetylcholine
what is an inhibitory neurotransmitter/what does it do?
- cross synaptic cleft
- cause hyperpolarisation of the postsynaptic membrane
- prevent action potentials being initiated
- e.g. GABA
what is an electrical synapse?
- the place where there is a direct physical connection between pre and postsynaptic neurone
- connection takes the form of a channel (gap junction) that allows current int eh form of ions to flow directly from one cell to another
- allows very fast cell signalling
what is an example of an electrical synapse?
transmission of the depolarising current from cell to cell, across chambers of the heart, so cells contract in unison
what is meant by ‘unidirectional impulses’ as a role of a synapse?
- neurotransmitter receptors are only present in postsynaptic membrane
- allows impulse from one neurone to transmit to a number of neurone