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Exam #3 W 4/2 in class
Review T 4/1 from 5-7pm in PAI 3.02
Before Exam #3: the nervous system,
movement and the immune system
Two ways to think about the world:
Reductionism
atoms
molecules
organelles
cells
tissues
organs
systems
organisms
environment
Two ways to think about the world:
Reductionism
atoms
molecules
organelles
cells
tissues
organs
systems
organisms
Wholism environment
Sensing and reacting to
the environment is critical
Failure to properly sense and react to the
environment can be fatal
Nerves allow us to perceive the environment
while the brain integrates the incoming signals
to determine an appropriate response.
CB 48.3
Neurons: cells specialized for
transmitting signals
CB 48.5
Parts of a neuron
Axon
Signals
In the brain neurons are shorter and highly
interconnected
CB 48.7
CB 48.5
Neurons: signals move through neurons
electrically and between neurons chemically
Nervous System Signaling
Stimulus
Transduction
Transduction
Response
Ionic gradients in
neurons
plasma membrane
CB 48.10
Na+/K+
pump
Na+
ATP–>ADP
K+
At rest, the Na+/K+
gradient is maintained
CB 48.13
Depolarization occurs
with the opening of Na+
channels
CB 48.13
An action
potential starts
when the local
depolarization
causes other
Na+ channels
to open
CB 48.13
Action potentials only occur when the initial
depolarization is above the threshold
CB 48.12
An action
potential starts
when the local
depolarization
causes other
Na+ channels
to open
CB 48.13
CB 48.13
Repolarization
is achieved
via closing
Na+ and
opening K+
channels
the Na+/K+ pump reestablishes the resting state
CB 48.13
Depolarization of one
part of the membrane
opens Na+ channels
further along so the
signal travels from one
end to the other
CB 48.14
Myelination: allows the depolarization to
travel faster
CB 48.8
Myelination: allows the depolarization to
travel faster…it jumps
CB 48.15
Neurons: signals move through neurons
electrically and between neurons chemically
CB 48.5
At the end of the neuron, neurotransmitters are
released signaling the next neuron to depolarize
CB 48.17
Neurotransmitters can be excitatory or inhibitory
(+)
CB tbl 48.1
(–)
(–)
(+)
(+/–)
(–)
At the synapse the electrical signal is
converted to a chemical signal
electrical
at synapse
chemical
electrical
Neurons are commonly connected to many
other neurons, and the effect of the different
incoming signals determines what the neuron
will do.
CB 48.16
Neurons are commonly connected to many
other neurons, and the effect of the different
incoming signals determines what the neuron
will do.
CB 48.18
Incoming signals move through neurons. Only signals
above the threshold are transmitted along the neuron.
Neuron videos:
http://www.youtube.com/watch?v=YwN9aCobCy8
http://www.blackwellpublishing.com/matthews/actionp.html
http://www.blackwellpublishing.com/matthews/nmj.html
The brain and the
central nervous
system integrate
the various
incoming signals
CB 48.19