neurons and synaptic transmission Flashcards
where are 80% of neurons in the body located?
in the brain
how do neurons provide the nervous system with its primary means of communication?
by transmitting signals electrically and chemically
what are the three types of neurons?
sensory neuron
relay neurons
motor neurons
what does the cell body of a neuron include?
a nucleus which contains the genetic material of the cell
what are the branchlike structures of a neuron called and what do they do?
dendrites which carry nerve impulses from neighbouring neurons towards the cell body
what does the axon do?
carry impulses away from the cell body down the legnth of the neuron
what is the axon covered in?
a fatty layer of myelin sheath that protects the axon and speeds up electrical transmission of the impulse
what would happen if the myelin sheath was continuous?
this would slow down electrical impulses
what is the myelin sheath segmented by?
nodes of ranvier
what do nodes of Ranvier do?
speed up the transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon
what is at the end of the axon?
terminal buttons that communicate with the next neuron in the chain across a synapse
where are sensory neurons located?
in the PNS in clusters (ganglia)
what % of neurons do relay neurons make up?
97% and most are found in the brain and visual system
when a neuron is in a resting state inside the cell how is it charged?
negatively compared to the outside
what causes an action potential to occur?
when a neuron is activated by a stimulus, the inside of the cell becomes positively charged
what does an action potential create?
an electrical impulse that travels down the axon towards the end of the neuron
how do neurons communicate?
within neural networks
how are signals within neurons transmitted?
electrically
how are signals between neurons transmitted?
chemically across the synapse
what happens when the electrical impulse reaches the end of the neuron (presynaptic terminal)?
it triggers the release of neurotransmitter from synaptic vesicles
what are neurotransmitters?
chemicals that diffuse across the synapse to the next neuron in the chain
what happens once a neurotransmitter crosses the gap?
it is taken up by the postsynaptic receptor site of the next neuron
why can the direction of travel only be one way?
because neurotransmitters are released from the presynaptic neuron terminal and received by the postsynaptic neuron
what do neurotransmitters have either of?
excitatory or inhibitory effect on the neighbouring neuron
what does te process of summation decide?
wether a postsynaptic neuron fires
what is likely to happen if the net effect on the postsynaptic neuron is inhibitory
the postsynaptic neuron is less likely to fire
what is likely to happen if the net effect is excitatory?
it is more likely to fire
when is the action potential of the postsynaptic neuron triggered?
if the sum of the excitatory and inhibitory signals at any one time reaches the threshold
