NEUROSCI 101 Lecture Notes - Lecture 3: Axon Hillock, Sodium-Potassium Alloy, Chemical Synapse

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17 May 2016
Department
Professor
2-4-16
Ch. 4: Neurochemistry
Pre-Lecture Questions:
Why don’t action potentials occur in dendrites?
EPSPs are smaller in the dendrites than in the axon and receive the impulse that
comes from the axon hillock. Dendrites also don’t have voltage-gated Na/K
channels to allow ion flow.
What normally causes sodium to rush in and initiate an action potential at the axon
hillock?
At the axon hillock, graded potentials such as EPSP/IPSPs are being summed
up. Na+ wants to pass through the cell membrane because of the principle of
electrostatic attraction (opposite charges attract) to make the inside of the cell
less negative.
In giant squid axon, action potentials are faster than graded potentials.
F, giant squid axons are unmyelinated
myelination speeds action potentials but doesn’t make action potentials faster
than graded potentials
GRADED POTENTIALS ARE ALWAYS FASTER
A +3 mV charge is administered to a giant squid axon. How would the voltage change
after the charge was given?
The voltage reading would decrement as it moves away from the site of
stimulation. This charge is considered a graded potential because it hasn’t
reached threshold (minimum requirement for +20 mV) yet.
(types of neurotransmitters, types of receptors/receptor binding, packaging, enzyme
deactivation discussed in paper notes)
Modern Memory Research
Carl Lashley (1940s) - searched for the “engram,” the region in the cortex associated
with memory creation, unable to find it, he declared that memories were distributed
throughout the cortex
Donald Hebb (1949)
learning and its retention (memory) involves strengthening of synapses
when an axon in cell A is near enough to excite cell B and repeatedly takes part
in firing it, some growth process or metabolic change takes place such that A’s
efficiency as a cell firing B is increased > learning occurs
over time, cont. firing must strengthen connection b/w A, B
how to “strengthen” a synapse (EPSPs increase when synapses get stronger):
increase NT release from presynaptic terminal
increased sensitivity of postsynaptic terminal
combination of both
long-term learning causes any of the following:
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