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Synapses - Coggle Diagram
Synapses
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Reflexes
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Sherrington strapped a dog into a harness above the ground and pinched one of the dog's feet - the dog flexed the pinched leg and extended the other legs
other legs extended: inhibitory postsynaptic potential (IPSP) - increases the negative charge within the cell, moving it farther from the threshold and decreasing the propability of an action potential
IPSP occurs when synaptic input selectively opens the gates for potassium ions to leave the cell (positive charge) or for chloride ions to enter the cell (carrying a negative charge)
the other legs need to be extended, otherwise the dog would lose balance
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temporal summation
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a light pinch of the dog's foot did not evoke a reflex, but a few rapidly repeated pinches did
the neuron that delivers transmission is the presynaptic neuron, and the one that receives it is the postsynaptic neuron
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spatial summation
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a pinch too weak to elicit a reflex - two pinches at different points together produce a reflex - activates seperate sensory neurons, whose axons converged onto one neuron in the spinal cord
drugs
hallucinogenic drugs (distort perception) like LSD chemically resemble serotonin - they provide stimulation at inappropriate times or for longer-than-usual durations
nicotine - stimulates a family of acetylcholine receptors (nicotine receptors) - releasing dopamine (associated with reward)
opiate drugs are chemically similart to the opium poppy (morphine, heroin, methadone - these bind to the same receptors as endorphins - releive pain by acting on receptors in the brain as well as in the skin
stimulant drugs like amphetamine and cocaine (and methylphenidate aka ritalin) inhibit the transporters for dopamine, serotonin and norepinephrine thus decreasing the reuptake and prolonging the effects of the neurotransmitters
COMT breaks down the excess dopamine fasater than the presynaptic cell can replace it and a fea hours after taking this drug, a user has a deficit of dopamine - withdrawal state
Hormones
a hormone is a chemical secreted by cells in one part of the body and conveyed by the blood to influence other cells throughout the whole body, where it is needed
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electrical synapses: a few special-purpose synapses do operate electrically - where exact synchrony between teo cells is important --> rhythmic breathing
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synapses: neurons communicate by trasmitting chemicals at specialised junctions, called synapses