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Lecture

1e The chemical synapse .doc

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Department
Biology
Course
BIOL 273
Professor
Norman Scott
Semester
Fall

Description
1e The Chemical synapse How are signals transmitted between cells? - neurons join to other neurons by gap junctions( set of holes through the membranes that allow electrical signals to pass through from one cell to the other) = electrical synapses - most neurons communicate with other cells CHEMICALLY through CHEMICAL synapses - illustration in notebook - synapse: presynaptic axon terminal, synaptic cleft, postsynaptic dendrite - presynaptic cell: cell that releases the NT - postsynaptic cell: binds the NT - space between the two = synaptic cleft (interstitial fluid) - when NT binds to receptor , it can initiate graded potentials (either depolarizing 'excitatory postsynaptic potential EPSP' or hyper-polarizing 'inhibitory postsynaptic potential IPSP') > receptor is ligand-gated channel Neurotransmitters and Receptors - amount of NT bound to receptors is in equilibrium with the amount that is free in the synaptic cleft - any factor that decreases the amount of free NT reduces the no. of NT-bound receptors: 1) diffusion out of synaptic cleft (NT) 2) degradation by enzymes in the cleft 3) uptake by glial cells or re-uptake by the presynaptic cell (recycle) - only one kind of NT releases and one kind of receptor - in any synapse there's only one kind of GP(signal) to be produced(transmitted) : either excitatory postsynaptic potential or inhibitory postsynaptic potential (not both) - a single neuron can have up to 10,000 synapses !!! ^ - a single axon can have multi branches (axon terminals), a single AP can bring about the release of diff NTs at diff chemical synapses - pre synaptic inhibition vs. pre synaptic facilitation - recently discovered that postsynaptic cell can signal the presynaptic. Allows a bidirectional exchange of information: - presynaptic cell axon terminal is converting electrical signals into chemical signals because the more action potentials it receives the faster it arrives the more NT is released - postsynaptic membrane does the opposite, incoming chemical signals (NT) are converted to electrical signals (GP) - the mor
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