Physiology of Nerve Conduction and Synapses PDF

**[Physiology of Nerve Conduction and Synapses]** - Fiber diameter: Greater the diameter, greater the AP - Myelination: Myelinated nerves conduct faster - Autoimmune disease - Affects approx. 3 million persons worldwide - Ages: 20-50 - Approx. 2/3 are women - Damaged myelin form...

**[Physiology of Nerve Conduction and Synapses]** - Fiber diameter: Greater the diameter, greater the AP - Myelination: Myelinated nerves conduct faster - Autoimmune disease - Affects approx. 3 million persons worldwide - Ages: 20-50 - Approx. 2/3 are women - Damaged myelin forms scar tissues (sclerosis) - [Most synapses are **chemical**]: - An action potential at the axon terminal causes release neurotransmitter(s) from the presynaptic membrane that diffuses across the synaptic cleft and attaches to specific receptors on the postsynaptic membrane - Some synapses are (rarely) electrical: - An action potential is directly transmitted from one cell to another through very close contacts between cells - gap junctions - The sign of a chemical synapse can be either excitatory or inhibitory; - This is the advantage of a chemical synapse, as an action potential can lead to release of neurotransmitters that either cause depolarization (excitation) or to hyperpolarization (inhibition) of the postsynaptic neuron - Release of glutamate, an excitatory neurotransmitter, causes opening of Na+ channels in the postsynaptic membrane - Influx of Na+ causes depolarization of postsynaptic neuron and the generation of EPSP - Release of GABA, an inhibitory neurotransmitter, causes opening of Cl- channels in the postsynaptic membrane - Influx of **Cl- causes hyperpolarization** of the postsynaptic neuron and the generation of an IPSP