Flashcards in Synapses Deck (21):
What is a synapse?
The junction between two neurones (or a neurone and an effector).
What are neurotransmitters?
Chemicals used to transmit impulses across the synapses.
What is the synaptic cleft?
The gap which separates the axon of one neurone from the dendrite of her next neurone.
What is a presynaptic neurone?
The neurone along which the impulse has arrived.
What is the postsynaptic neurone?
Neurone that receives the neurotransmitter.
What is the synaptic knob?
The swollen end of the presynaptic neurone.
What are synaptic vesicles?
Vesicles containing neurotransmitters.
What are neurotransmitter receptors?
Receptor molecules which the neurotransmitter binds to in the postsynaptic membrane.
What are the two types of neurotransmitter?
Excitatory and inhibitory.
What do excitatory neurotransmitters do?
Result in the depolarisation of the postsynaptic membrane.
Action potential can be triggered.
What do inhibitory neurotransmitters do?
Result in the hyperpolarisation of the postsynaptic membrane.
Action potential is prevented from being triggered.
Describe in steps the mechanism of transmission of impulse across synapses.
1) AP reaches end of presynaptic neurone.
2) Calcium ion channels triggered to open.
3) Calcium ions diffuse into synaptic knob.
4) Synaptic vesicles fuse with membrane, neurotransmitter is released.
5) Neurotransmitter diffuses across synaptic cleft and binds to receptors.
6) a Sodium ion channels open.
7) Sodium ions diffuse into postsynaptic neurone.
8) AP is triggered in postsynaptic neurone.
What are the three main roles of the synapse?
To ensure impulses are unidirectional.
To allow an impulse from one neurone to be transmitted to a number of neurones.
To allow a number of neurones to feed into the same synapse.
What is summation?
When the amount of neurotransmitter builds up sufficiently to reach the threshold so much that an action potential is triggered.
What are the two ways in which summation can occur?
Spatial summation and Temporal summation.
When does spatial summation occur?
When many presynaptic neurones connect to one postsynaptic neurone. Builds up to a high enough level in the synapse.
When does temporal summation occur?
When a single presynaptic neurone releases neurotransmitter several times over a short period. Builds up in synapse until amount is sufficient.
Do drugs that stimulate the nervous system create more or fewer action potentials?
More, which results in an enhanced response.
Do drugs that inhibit the nervous system create more or fewer action potentials?
Fewer, which results in a reduced response.
Drugs that stimulate the nervous system work by...(3 ways)
1) Mimicking the shape of a neurotransmitter.
2) Stimulating the release of more neurotransmitter.
3) Inhibiting the enzyme responsible for breaking down the neurotransmitter