Physiology 3120 Lecture Notes - Lecture 8: Axon Hillock, Depolarization, Schwann Cell

• School: Western University
• Department: Physiology
• Course: Physiology 3120
• Professor: Tom Stavraky

Document Summary

Presynaptic nerve causes release of neurotransmitter onto post synaptic nerve that releases neurotransmitter onto dendrite (cell body) Neurotransmitter builds up a positive charge inside post synaptic nerve (particularily at axon hillock) so this positive charge is the stimulus that is going to initiate that depolarization. The magnitude of the depolarization required to initiate an action potential. The depolarizing forces (coming from the positive charge started by the presynaptic nerve) must overcome the natural stabilizing forces (trying to return to -70mv) So at threshold (-55mv), the depolarizing forces are strong enough to overcome the stabilizing forces shown in table. +ive charge flowing into cell at synapse (-60mv) Decays rapidly with distance and time from point of stimulus they are not propagated. Magnitude of the response is proportional to the magnitude of the stimulus (graded) May be depolarizing (excitatory postsynaptic potential, epsp) or hyperpolarizing (inhibitory postsynaptic potential, ipsp)