Neurons and Synaptic Transmission
- Created by: hellostudents
- Created on: 23-04-20 17:29
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- Neuron and Synaptic Transmission
- Structure and Function of Neurons
- Neurons = specialised cells that carry neural information throughout the body
- Dendrites receive signals from other neurons or from sensory receptors
- Cell body is the control centre of the neuron. From here the impulses are carried along the axon
- Axon is where the impulses are terminated at the axon terminal
- Myelin sheath is an insulating layer around the axon if it is damaged the impulses slow down
- Sensory neurons:
- Carry nerve impulses from sensory receptors the spinal cord and the brain
- When they reach the brain they are converted into sensations so the organism can react accordingly
- Impulses terminated in the spinal cord allows for reflexes occur quickly with out delay
- Carry nerve impulses from sensory receptors the spinal cord and the brain
- Relay neurons:
- Allow sensory and motor neurons to communicate
- Lie within the brain and the spinal cord
- Motor neurons:
- Form synapses with muscles and control their contractions
- Release neurotransmitters that trigger a response and lead to muscle movement
- Strength of muscle contraction depends on the rate of the firing of axons of motor neurons that control
- Synaptic Transmission
- 1) An action potential arrives at the terminal button at the end of the axon
- 2) For it to be transferred it must cross a synapse between the presynaptic neuron and the postsynaptic neuron
- 3) End of the axon there are a number of synaptic vesicles that contain neurotransmitters
- 4) Once the AP reaches the vesicles they release their contents through exocytosis
- 5) The neurotransmitters diffuses across the gap between the pre and post cell where it binds to receptors
- 6) Once the y are activated the receptors produce excitatory or inhibitory effects on the postsynaptic neuron
- Excitatory and Inhibitory Neurotransmitters
- Excitatory neurotransmitters e.g noradrenaline increase the likelihood that an excitatory signal is sent to the postsynaptic cell which is then more likely to fire
- Nervous systems on switches
- When binding with a postsynaptic cell causes an electrical change in the membrane resulting in an EPSP
- Inhibitory neurotransmitters e.g serotonin decrease the likelihood of the neuron firing. They are generally responsible for calming the mind and bodying filtering out unnecessary excitatory neurons
- Nervous systems off switches
- When bonded with a postsynaptic receptor results in an IPSP
- Nerve cells can receive both IPSP and EPSP at the same time the likelihood of the cell firing is determined by adding up the synaptic input
- The strength of an EPSP can be increased by spacial summation and temporal summation
- Spacial summation is where a large number of EPSPs are generated at many different synapses on the same postsynaptic neuron at the same time
- Temporal summation is when a large number of EPSPs are generated at the same synapse by high frequency action potentials on the presynaptic nerve
- The strength of an EPSP can be increased by spacial summation and temporal summation
- Excitatory neurotransmitters e.g noradrenaline increase the likelihood that an excitatory signal is sent to the postsynaptic cell which is then more likely to fire
- Structure and Function of Neurons
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