Download Resting Membrane Potential

Do Now 1/9/15
1. Name 3 glial cells and describe their function and location.
2. Which neural pathway transmits a signal when the internal
body temperature is too high?
3. What is the difference between the somatic and the
autonomic branches of the nervous system?
4. What is resting membrane potential?
Resting Membrane Potential
Resting Membrane Potential
• Neuron has an overall -70 mV charge
• K+ ion concentration is higher INSIDE
the neuron
• K+ will want to leave the neuron if it
can
• Na+ ion concentration is higher
OUTSIDE the neuron
• Na+ will want to enter the neuron if it
can
• Channels are closed so the ions
cannot diffuse…
yet…
How does a neuron go from
resting to firing?
• The resting membrane potential of a neuron
is -70 mV
• In order for a neuron to fire a signal, the
membrane potential must reach a certain
threshold, around -55 mV.
• This happens when another neuron stimulates
it and allows a few Na+ channels to open and a
few Na+ ions enter the axon
Action Potential
When neurons FIRE!
• Caused by the rapid opening and closing of
voltage-gated channels
• Transfer information from one place to another
in the nervous system
How do action potentials start?
• A neuron is electrically stimulated in some way
• From a sensory experience (sensory neurons)
• Accumulated electrical potentials in the dendrites
• From an outside electrical signal
• The result of any of these electrical stimulations is the
opening of Na+ ion channels
• Which direction will the Na+ ions want to go?
• What effect will the diffusion of Na+ ions have on the overall
charge of the neuron?
Membrane Potential Graph
1. Resting
Na+ channels closed
Membrane Potential Graph
2. Threshold
When the membrane
potential reaches the
threshold, the Na+
channels open, allowing
more Na+ to enter the
neuron
Membrane Potential Graph
3. Depolarization
The Na+ channels are
open and Na+ is rapidly
flowing into the neuron,
causing the membrane
potential to become more
positive
Membrane Potential Graph
4. Peak
The Na+ channels are closed
5. Repolarization
The extra K+ channels are
opened. K+ ions rush out of
the neuron, causing the
membrane potential to
become more negative
Membrane Potential Graph
6. Hyperpolarization and
return to Resting
K+ channels continue to be
open until the membrane
potential reaches the
voltage of resting membrane
potential. K+ close and
resting membrane potential
is maintained
How does the action potential
work?
How does the action potential
work?
How does the action potential
work?
1. Describe the movement of potassium and sodium ions
during an action potential.
2. What must happen before sodium can rush into the axon?
3. Why does potassium leave the neuron during
repolarization?
4. Summarize the process of an action potential.
Jumpin the (Synaptic) Gap
1. What structure is responsible for “recycling”
neurotransmitters back into the axon terminal once they have
done their job?
2. How do the vesicles “know” when to move to the membrane
to dump their contents into the synapse?
3. How does the message continue past the post-synaptic
membrane?
Excitatory Post-Synaptic Potential
(EPSPs) & Inhibitory Post-Synaptic
Potentials (IPSPs)
• Neurotransmitters released into the synaptic gap can either be
excitatory or inhibitory
• Excitatory – makes the next neuron more likely to fire (more +)
• Inhibitory – makes the next neuron less likely to fire (more -)
• Post-synaptic potentials are graded potentials
• They have an additive effect
• When multiple PSPs occur at the
same place, the combined effect is
the sum of all of them
• The combination of EPSPs and IPSPs
must reach threshold in order for the
next neuron to fire
http://sites.sinauer.com/neuroscience5e/anim
ations05.02.html