Neurons and synaptic transmission Flashcards
What are the three types of neuron?
Neurons and synaptic transmission
Sensory, relay and motor
Cell body
Neurons and synaptic transmission
Nucleus - which contains genetic material
Dendrites protude from cell body and carry nerve impulses from neighbouring neurons towards the cell body
Axon
Neurons and synaptic transmission
Carries impulses away from cell body down the length of the neuron
Covered in fatty layer of myelin sheath which protects axon and speeds up electrical transmission
Nodes of Ranvier
Neurons and synaptic transmission
Segmented gaps in myelin sheath
Speed up transmission of impulse by foricng it to jump across gaps
Terminal buttons
Neurons and synaptic transmission
At the end of axon
Communicate with next neuron in chain across the synapse
Location of motor neurons
Neurons and synaptic transmission
Cell body in CNS but long axons form part of the PNS
Location of sensory neurons
Neurons and synaptic transmission
Outside of CNS, in the PNS in clusters known as ganglia
Location of relay neurons
Neurons and synaptic transmission
Make up 97% of all neurons
Found within brain and visual system
How are neurons fired?
Neurons and synaptic transmission
When in resting state, inside of cell is negatively charged compared to outside
When a neuron is activated by a stimulus, inside of cell becomes positively charged for split second causing action potential to occur
Creates electrical impulse that travels down axon towards end of neuron
Chemical vs Electrical transmission
Neurons and synaptic transmission
Signals within neurons are transmitted electrically
Signals between neurons are transmitted chemically across the synapse
When electrical impulse reaches end of neuron it triggers the release of neurotransmitter from synaptic vesicles
How do neurotransmitters diffuse across the synapse?
Once crossing gap, it is taken up by postsynaptic receptor site on dendrites of next neuron
Here, chemical message is converted back into an electrical impulse and the process of transmission begins again
Direction of travel is one way
Excitation and inhibition
Neurons and synaptic transmission
Serotonin cause inhibition in recieving neuron - neuron becomes more negatively charged and less likely to fire
Adrenaline cuases excitation of the postsynaptic neuron by increasing its positive charge and making it more likley to fire
Summation
Neurons and synaptic transmission
Summation decides whether postsynaptic neuron fires or not
Excitatory and inhibitory influences are summed
If net effect on postsyn neuron is inhibitory then postsyn neuron is less likely to fire
If net effect is excitatory it is more likely to fire
Once electrical impulse is created it travels down the neuron
