Chapter 17

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1

endoneurium

within a nerve each fiber is surrounded by a delicate connective tissue sheath
(which insulates it from the other neuron )
wraps an individual axon

2

perineurium

groups of fiber are bound by a coarser connective tissue, called the
wraps a fascicle (bundle of axons)

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epineurium

all the fascicles are bound together by a white fibrous connective tissue sheath
forming the cordlike nerve (wraps entire nerve)

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mixed nerves

nerves carrying both sensory (afferent) & motor(efferent) fibers are called
most nerves including all spinal nerves

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Nervous tissue

is made up of just two principal cell populations neurons & supporting cells
neuroglia nerve glue gial cells

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Schwann & satellite cells

the most important glial cells in the PNS

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action potential AP

An electrical signal that propagates along the membrane of a neuron or muscle fiber (cell )arapid change in membrane potential that involves a depolarization followed by a Repolarization .

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excitability

the ability of muscle fibers to receive & respond to stimuli the ability of neurons to respond to stimuli & generate nerve impulses

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Depolarization

Tripped

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Repolarization

resending

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resting membrane potential

is the difference in voltage of the fluids inside a cell and outside a cell, which is usually between -70 to -80 millivolts (mV). All

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, How do ether, curare and lidocaine inhibit nerve impulses

Lidocaine can be used to numb the skin before placement of an IV line or minor surgery. Explain why lidocaine is appropriate for this application (hint: think about the branches of the peripheral nervous system.)
Lidocaine blocks sodium channels.

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What is the effect of curare on eliciting an action potential?

it is an alpha-toxin that binds to acetylcholine binding sites on the postsynaptic cell membrane, which prevents the acetylcholine from acting. Curare blocks synaptic transmission by preventing neural

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The Effects of Curare on Nerve Impulse

Description
Curare is a generic term for South American arrow poisons, usually from the strychnos toxifera or chondrodendron tomentosum plants. Also known as tubocurarine, curare functions as a neuro-muscular blocking agent, or muscle relaxant

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The Effects of Curare on Nerve Impulse

Location of Action
Curare acts at the junction between the nerve and muscle to block the transmission of nerve impulses. Nerve impulses are electrochemical messages that propagate along nerve fibers and muscle cells to produce an action.

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Factors affecting nerve conduction velocity

The factors affecting nerve conduction velocity are as follows:(i) Axon diameter:An axon with a larger diameter conducts faster. In an unmyelinated fiber, the speed of propagation is directly

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Factors affecting nerve conduction velocity

How does myelination affect nerve conduction velocity?
Another question is..why does the addition of sodium chloride elecit an action potential? (Hint: Think about the sodium permeability of the neuron.)

Schwarn cells lay down myelin and wrap it around the axon. When a signal is moving down the axon (i.e.the sodium and potassium exchange is occurring as the channels open) each channel will only open after the one before it has opened. The myelin sets up local circuits, which mean that the spaces between the channels are further apart, thus, the signal can jump between them at a far greater speed than if it was a continuous set of membrane channels.

In the watery interstitial fluid between the cells, the salt will dissociate into sodium and chloride ions. The sodium will alter the charge gradient across the membrane, causing the opening of channels and the generation of an action potential.