1. Notes

2. A. A cell membrane is usually polarized.
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Cell Membrane Set-up
A. A cell membrane is usually polarized.
-excess of negative charges on the inside of the membrane
-sodium and potassium ions
B polarization is important to the conduction of nerve impulses.

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4. 1. More sodium outside and more potassium inside.
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Distribution of Ions
1. More sodium outside and more potassium inside.
2. Cytoplasm has a high amount of negative ions and proteins that can’t leave the cell. Inside is more negative than outside.
3. Channels in membranes are selective.
Potassium has easier time leaving than sodium
Potassium is impt in membrane polarization
Calcium has the hardest time of all.
4. Sodium-potassium pump-ATP is used to pump sodium and potassium ions across the membrane

5. Cell (inside) is at -70 millivolts
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Resting Potential
Active Transport allows for potassium to move out faster than sodium moving in.
This separation of charge, or potential difference, is called the resting potential.
Cell (inside) is at -70 millivolts

6. Things happen to the membrane:
When a neurotransmitter is picked up, it will stimulate the membrane.
An action potential can occur:
Repolarization
Depolarization

7. Depolarization
Inside of the membrane becomes less negative (more positive)-increase in volts
Sodium channels open and potassium channels close
Stimulation must reach a certain point (threshold) before the neuron continues on.

8. Repolarization
As depolarization takes place, potassium channels open and sodium closes, which is repolarization.
Inside of the membrane becomes negative
Refractory period-time when the neuron cannot respond to a second stimulus (time when the graph dips below resting potential)

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Action Potential
At threshold potential, membrane permeability to sodium suddenly changes in the region of stimulation.
As sodium channels open, sodium ions rush in, and the membrane potential changes and becomes depolarized.

11. -This rapid sequence of events is the action potential.
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At the same time, potassium channels open to allow potassium ions to leave the cell, the membrane becomes repolarized, and resting potential is reestablished.
-This rapid sequence of events is the action potential.
The active transport mechanism then works to maintain the original concentrations of sodium and potassium ions.
Hyperpolarization-a deep below the -70 mv occurs because gates are closed and chlorine comes into the cell. So the cell negativity drops more.

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Nerve Impulse
A nerve impulse is conducted as action potential is reached at the trigger zone and spreads by a local current flowing down the fiber, and adjacent areas of the membrane reach action potential.

14. MYELINATED VS UNMYELINATED
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Impulse Conduction
MYELINATED VS UNMYELINATED
Unmyelinated fibers conduct impulses over their entire membrane surface.
Myelinated fibers conduct impulses from node of Ranvier to node of Ranvier, a phenomenon called saltatory conduction.
Saltatory conduction is many times faster than conduction on unmyelinated neurons.
AXON DIAMETER
The greater the diameter, the faster it travels.

15. How does an action potential move from one neuron to the next?
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All-or-None Response
If a nerve fiber responds at all to a stimulus, it responds completely by conducting an impulse (all-or-none response).
Greater intensity of stimulation triggers more impulses per second, not stronger impulses.
Complete depolarization must take place for a neuron to travel along the axon
How does an action potential move from one neuron to the next?

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The Synapse
The junction between two communicating neurons is called a synapse
There exists a synaptic cleft between them across which the impulse must be conveyed.
Presynaptic neuron-carries pulse
Postsynaptic neuron-receives it
When the impulse reaches the synaptic knobs (also known as axon terminal), neurotransmitters must be released from synaptic vesicles into the synaptic cleft.
The nts are released because of the influx of calcium.
Recycled, deactivated, or attach to receptors

17. Label on your noteguide.

20. Excitatory and Inhibitory Actions
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Excitatory and Inhibitory Actions
Neurotransmitters that increase postsynaptic membrane permeability to sodium ions may trigger impulses and are excitatory.
Acetylcholine, epinephrine, norepinephrine, serotonin, amino acids
Decrease membrane permeability to sodium ions, reducing the chance that it will reach threshold, and are inhibitory.
GABA, dopamine

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Impulse Processing
How impulses are processed is dependent upon how neurons are organized in the brain and spinal cord.
Neuronal Pools
Neurons within the CNS are organized into neuronal pools with varying numbers of cells.
Each pool receives input from afferent nerves and processes the information according to the special characteristics of the pool.

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Facilitation
A particular neuron of a pool may receive excitatory or inhibitory stimulation; if the net effect is excitatory but subthreshold, the neuron becomes more excitable to incoming stimulation (a condition called facilitation).

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Convergence
A single neuron within a pool may receive impulses from two or more fibers (convergence), which makes it possible for the neuron to summate impulses from different sources.

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Divergence
Impulses leaving a neuron in a pool may be passed onto several output fibers (divergence), a pattern that serves to amplify an impulse.

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26. Reflex Arc Sensory neuron---interneuron in spinal cord---motor neuron
Autonomic
Homeostasis and survival (withdraw reflex)