A chemical messenger
sent into the bloodstream
targets an organ
where they produce an effect.
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Synaptic transmission.
Stage1
An electrical impulse travels along the axon of a neuron.
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Synaptic transmission
Stage2
This stimulates the release of chemical messengers called neurotransmitters from the vesicles moving and binding to the cell membrane of the presynapse within the nerve cell.
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Synaptic transmission
Stage3
The neurotransmitters diffuse across the gap.
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Synaptic transmission
Stage4
The neurotransmitters bind with receptors on the membrane of the next neuron.
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Synaptic transmission
Stage5
This stimulates the post synaptic neuron to transmit an electrical impulse if enough excitatory neurotransmitters is taken up in the post synapse.
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Synaptic transmission
Stage6
The neurotransmitters are reabsorbed in the vesicles of the pre synaptic neuron or are either broken down chemical by enzymes in the synapse.
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What is excitatory neurotransmitters?
E.g noradrenaline
Makes the posy synaptic cell more likely to fire.
Excitatory neurotransmitters binding with the post synaptic receptor causes an electrical change in the membrane.
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What is inhibitory neurotransmitters?
E.g serotonin
makes them less likely to fire.
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What is the Sympathomedullary pathway?
Hypothalamus activates the autonomic nervous system on the sympathetic branch.
This activates the adrenal medulla.
The release of adrenaline and noradrenaline prepares the body for flight or fight. Once the parasympathetic is activated the body turn back
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What is noradenaline?
Responsible for increasing heart rate, triggering the release from energy stores and increasing blood flow to skeletal muscle.
Increases brain oxygen supply.
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What is adrenaline?
Regulates heart rate, blood vessels and air passage diameters which is crucial component of the fight or flight response.
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What is the Hypothalamic pituirity adreno pathway (HPAC)?
Hypothalamus stimulates the release of CRF in the bloodstream which activates the piturity gland. This releases ACTH which activates the adrenal cortex which stimulates the release of cortisol.
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What is cortisol?
Hormone involved in chronic stress.
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Why do neurons transmit information in one direction at a synapse?
the vesicles are only on the ends of the pre synaptic cell and the receptors are at the dendrites of the post synaptic cell.
Therefor, neurotransmitters can only travel one way.
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