synaptic transmission Flashcards
1
Q
explain what chemical transmission is
A
- neurons communicate with each other within groups known as neural networks
- each neuron is separated from the next by a tiny gap called the synapse
- signals within neurons are transmitted electrically.
- signals between neurons are are transmitted chemically across the synapse
- when the electrical impulse reaches the end of the neurone (known as the presynaptic terminal) it triggers the release of neurotransmitter from tiny sacs called synaptic vesicles.
2
Q
explain the role of neurotransmitters
A
- they are chemicals that diffuse across the synapse to the next neuron in the chain
- once a neurotransmitter crosses the gap, it is taken up by a postsynaptic receptor site on the dendrites of the next neuron (axons TO/dendrites AWAY from the synapse)
- here the chemical message is converted back into electrical impulse and the process of transmission begins again in this other neuron
- the direction of travel can only go one way because neurotransmitters are released from the presynaptic neuron terminal and received by the postsynaptic neuron (receptor site)
- they have specific functions and fit perfectly into the postsynaptic receptor site.
3
Q
explain excitation
A
- neurotransmitters can have an excitatory effect on the neighbouring neuron. E.g. adrenaline (an element of the stress response which is both a hormone and a neurotransmitter) causes excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire.
4
Q
explain what inhibition is
A
- the neurotransmitter serotonin causes inhibition in the receiving neuron. resulting in the neuron becoming more negatively charged and less likely to fire.
5
Q
explain what summation is
A
- whether a postsynaptic neuron fires is decided by the process or summation. The excitatory and inhibitory influences are summed
- if the net effect on the postsynaptic neuron is inhibitory then the postsynaptic neuron is less likely to fire.
- if the net is excitatory it is more likely to fire- the inside of the postsynaptic neuron momentarily becomes positively charged. Once the electrical impulse is created it travels down the neuron.
- therefore the action potential of the postsynaptic neuron is only triggered is the sum of the excitatory and inhibitory signals at any one time reaches the threshold.
6
Q
what is synaptic transmission?
A
the process by which neighbouring neurons communicate with each other by sending chemical messages across the synapse that separates them
7
Q
what us a neurotransmitter
A
- are brain chemicals released from synaptic vesicles that relay signals across the synapse from one neuron to another.
- can be broadly divided into those that perform an inhibitory and excitatory function.
8
Q
explain the process of synaptic transmission
A
- when an electrical impulse at the end of the neuron (presynaptic terminal), it triggers the release of neurotransmitters from sacs called synaptic vesicles.
- neurotransmitters are chemicals that diffuse across the synapse to the next neuron in the chain. once it crosses the gap they are picked up by a post-synaptic receptor site on the dendrites of the next neuron. The chemical message is then converted back to electrical and the process begins again.
- neurotransmitters either have an excitatory or inhibitory effect on neighbouring neurons. Serotonin gives an inhibitory effect so the neuron becomes more negatively charged and is less likely to fire. Adrenaline causes a excitatory effect of the post-synaptic neuron and increases its positive charge so its more likely to fire.
- summation then happens when the influences are summed. If the net effect is inhibitory in the post-synaptic neuron its less likely to fire and if its excitatory its more likely to fire. The action potential of post-synaptic neuron is only triggered if the sum of excitatory and inhibitory signals at any on time reaches the threshold.
