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Presynaptic Neuron (Synaptic Cleft (Post Synaptic Neuron (there is an…
Presynaptic Neuron
Synaptic Cleft
Post Synaptic Neuron
can be on the neuron or on the effector tissue
there is an active site for a specific NT for the receptor
temporarily opens ligand gated channels directly (ionotropic)
post-synaptic potential is created and its magnitude is based on the number of channels opened
inhibitory IPSP
hyper polarizing
positive ions flow out, negative ions flow in
excitatory EPSP
depolarizing
positive ions flow in, negative ions flow out
fast chemical transmission
Receptor could be a nicotinic receptor for acetylcholine
Ach will activate muscles at the neuromuscular junction
Neurotransmitter diffuses across the synaptic cleft to the post synaptic neuron membrane receptors
Left over NT is removed
Broken down by catabolic enzymes on Post synaptic neuron membrane
via re-uptake pumps on presynaptic membrane
monoamine oxidase breaks down norepinephrine
can be degraded by enzymes in axon terminal
In the CNS glial cells break down NT
Neurotransmitter is packaged into a vesicle
Vesicle with the NT fuses with the presynaptic membrane
Neurotransmitter is released through exocytosis into the synaptic cleft
VG Ca++ channels open and Ca++ enters down the gradient increasing the Ca++ content
AT REST
VG Na+ and VG K+ channels are closed
K+ leak channels are open and K+ is moving freely according to its equilibrium
Depolarization
Na+ VGC open and Na+ moves into the cell w/ its concentration gradient
membrane slowly depolarizes to threshold point and action potential is started-NO RETURN