A 40mV presynaptic depolarization is required to produce a synaptic potential.
Beyond this threshold there is a steep increase in amplitude of the synaptic potential in
response to small changes in the amplitude of the presynaptic potential.
2. The semilo
Overview of Synaptic Transmission
The average neuron forms about 1000 synaptic connections and
receives even more, perhaps as many as 10,000 connections.
Synapses Are Either Electrical or Chemical
The term synapse was introduced at the turn of the century
There are two main classes of cells in the nervous system:
nerve cells (neurons) and glial cells (glia).
Glial Cells Are Support Cells
Glial cells far outnumber neuronsthere are between 10 and 50 times more glial than
neurons in the central nervous system
Metabotropic second messenger signaling
The conversion of GGTP to GGDP is not NT dependent and
serves as a time out switch
Once activated by the receptor the GTPase activity becomes
rate limiting and the active state accumulates
Signaling at the Nerve-Muscle
Synapse: Directly Gated
The axon terminals lie
over a specialized region of the
muscle fiber membrane, the endplate, and are separated from the
muscle membrane by a 100 nm
Electron microscope auto
Graded synaptic potentials
Summation, temporal and spatial
spike frequency; duration and
Quantal release, (analog)
The charge separation gives rise to a difference of electrical
potential, or voltage, across the membrane call
The combination of
excitatory and inhibitory
mediating the stretch reflex
of the quadriceps muscle is
typical of circuits in the
central nervous system.
Inhibition can shape the firing pattern of a spontaneously acti
Four criteria for a neurotransmitter:
1) It is synthesized in the neuron.
2) It is present in the presynaptic terminal and is released in
amounts sufficient to exert a defined action on the postsynaptic
neuron or effector organ.
3) When administered exoge
Ion channels have three
(1) They conduct ions,
(2) they recognize and
select specific ions,
(3) they open and close in
response to specific
electrical, mechanical, or
ions flow through
channels @ 108
1Biol 418 QUIZ# 3:
1. What do all the various glutamate receptors have in common?
a. they all bind glutamic acid
b. they allow for simultaneous Na+amd K+ exchange when activiated
c. they all use Ca2+ as a second messenger
d. A and B
2. GABA stands
Jonathan R. Day
Dr. Katie Collins, PhD
Neurophysiology, BIOL 418, Spring 2014
Instructor: Jonathan R. Day, Ph.D.
Office Hours: M 3-4 pm; TR 3-5 pm (Holt 223); or by appointment
Office (Biological Scie
Communication within neuron
electric current = movement of
Bioelectric: movement of ions ~
Particles / molecules