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1

cell type of nervous system

neurons and glia

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Neuron

Responsible for communication; transmit, receive and integrate information

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glia

support, nourish and protect cells, *they can be replaced unlike neurons

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3 main parts of the neuron

dendrites, cell body or soma, axon

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dendrite

branching region of neurons

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cell body or soma

contains the nucleus, genetic blueprint that guides the cells functions or producing proteins and chemical messages

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axon

"root" how it passes through (how its transmitted), moves along the axon, chemicals release at the end of the axon so the other cells get the message, covering the axon is a type of glia cell

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Myelin Sheath

insulates axons and speeds transmission of signals, they are white, it is why we say "white matter" just glia cells , information and messages passed much quicker with the myeline sheath

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multiple sclerosis

de-myelinating disease. auto immune disorders that attack the myeline sheath, problems with muscular movement, tend to come and go

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hodgkin and huxley

1952, first ones to explain nerve impulse, won the nobel prize

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hodgkin and huxley experiment

take squids (have large axons) can embed an electrode inside the neuron and outside to see what electro pulses are going on. fluid inside and outside the cell within the fluid there are electrically charged ions

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resting potential

stable negative charge -70mV

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neuron at rest

negative charge on inside compared to outside of cell

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ions involved neural impulse

potassium (k+) inside of the cell, sodium (Na+) on the outside

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Action Potential cause

spike caused by a change in the flow of the ions

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action potential ion flow

little gates or channel all along the axon open when stimulated to create a change in ion concentration, Na rushed in, once it moves past K goes out, resetting the resting potential

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What happens when the action potential moves along the axon

it reaches the terminal buttons which release neurotransmitters

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threshold for action potential

-50 mV

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Depolarization

Na+ ions rush into the cell making the inside of the cell positive

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Repolarization

K+ ions rush out of the cell, resetting the charge making it negative

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Hyperpolarization

during the time that so many k+ ions rush out of the cell it becomes more negative than the resting period, then the gates close and the concentration returns to resting potential

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transmit action potential to other cells

the ion flow at one location creates a charge that affects the neighbouring regions that spark the action potential of the next region...

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Speed of action potential

1 millisecond (100m/s)

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Relative refractory Period

where you could create a new action potential but the cell needs more stimulation, during hyperpolarization. Extra work to generate another action potential, threshold is bigger because the cell is so negative, so you would need a lot of excitatory stimulation

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Absolute Refractory period

depolarization refers to the fact that you cannot generate another action potential in the cell, no matter how strong the stimulus another action potential will not occur

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all or none law

refers to the fact that if we get to the -50mV we will have an action potential if we dont we will get nothing

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Characteristics of every action potential

same magnitude, same overall change is electrical energy were recording over the membrane, variable firing rate, travels extremely fast

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Variable Firing Rate

different cells will fire action potential at different rates (how many times a second does this happen in a cell)

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travels extremely fast

a myelin sheath allow for the information to move that fast 100m/sec, produce action potentials to code for different information. we need motor and sensory information to travel really quickly so that our body responds to prevent injury

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Where are neurotransmitters stored

synaptic vesicles