Ch. 12: Nervous Tissue

Front 1

Brian

Back 1

100 billion neurons housed in skull

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Cranial Nerves

Back 2

12 pairs emerge from base of brain

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nerve

Back 3

axons and neurons. Has connective tissue and blood vessels. Occurs ouside brain and spinal cord.

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Spinal cord

Back 4

conects to brian and down vertabre

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spinal nerves

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31 emerge from spinal cord

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ganglia

Back 6

small mass of nervous tissue. Located outside brain and spinal cord. Primarily contain cell bodies and neurons.

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Enteric Plexuses

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Network of neurons in walls of G.I. tract.

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Sensory Receptors

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Specialized cells or dendrites of sensory neurons that monitor internal or external changes.

Front 9

Sensory Function

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dectects changes (stimuli) within or outside body. Sensory (afferent) neurons carry out this function. Carry this information to brain and spinal cord or from a lower to a higher level in spinal cord and brain.

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Intergrative Gunction

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Analises info. stores it. Decides on an approriate response. *Interneurons do this and are most common neurons in the body.

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Motor Function

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responds to stimuli by initiating muscle contractions. MOtor (efferent) neurons carry this info from brain to spinal cord or out of there to effectors to respond. (ex: muscle cells or gland cells)

Front 12

Central Neverous System (CNS)

Back 12

Consists of brain and spinal cord. Carries out intergrated function

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Peripheral nervous system

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Cranial nerves, spinal nerves, ganglia, and sensory receptors. Supply rest of body The PNS consist of three sub-systems.
Somatic (sns)- takes info from wall and sense receptors to CNS. Conduct info to effectors in skeletal muscle.
Autonomic (ANS)- take info from viscera(organs) to CNS. Motor part takes info from CNS to effector that are smooth and xardiac muscles or glands. Uasually invoulentary. Motor has 2 divisions.
1. Parasympathetic- rest and digest reponse. Restores or conserves energy. (dec. heart rate)
2. Sympathetic Division- involves experdture of energy (when under stress or excited) (fight or flight) (increase heart rate)
3. Enteric (ENS) enteric plexuses of G.I. tract and can cork independantly of ANS. Monitor chemical changes in G.I. tracts and stretch walls

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Cell body

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1. contains nucleus and organells like mytochondria.
2. niss. bodies are rough E.R. that produce protien and involved in groth of PNS to regerat damage.

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Acon Hillock

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lone shapped elevation of cell body where axon joins cell body.

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Nerve Fiber

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any natural process comming from cell body. (Dendrites and axons)

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Dendrites

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processes from cells that recives input. Part of nuerons and usually are short and highly branched.

Front 18

Axon

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1. Typically one. May branch into azon collatoral.
2. Carries nerve impulses to another nueron, muscle fiber, or gland cell.
3. Initial segment is part of axon closest to cell body.
4. Trigger cone is where axon meets cell body. Is where action potential starts.
5. axoplasm is axon cytoplasm.
6. Axolemma is axon plasma membrane.
7. Synaptic end bulbs or varicositres occur at ends of axon and contain synaptic besicles. They store neurotransmitters which affect other neurons, muscles, ect. (Synapse is a connection between a neuron and another cell, but more commonly two neurons.)

Front 19

Mutipolar Neuron

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Has several dendrites and ONE axon connected to cell body.

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Bipolar Neuron

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ONE axon and ONE dendrite. Found in vision, hearing, ect.

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Unipolar Neuron

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Only one process from body and this fiber connects to the main fiber their trigger zone is at junction of axon and dendrite (in sensory)

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Neuroglial cell

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more common than neurons and assist nutrons

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Astrocytes

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star shapped. Physically support neurons. Maintian chemical enviornment for action pontential. Help from blood-brain barrier. Transport substances from blood vessles to neurons. Help learning by influencing synapses.

Front 24

Oligodemrocytes

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Form myelin sheath around axons in CNS. Reason we cant repair damafe done by stroke or to spines

Front 25

Ependymal Cells

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Form pithelial membrane lining, Cerevral cavities(ventricles), and central canal of spinal canal. Produce Cerebrospinal fluid (CBF)

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Neuroglia of PNS

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Schwann cells produce myelin sheath around PNS. Help with regeneration of PNS.Satellite cells suround and support cell bodies of neurons in PNS in ganglia. Regulate exchange of materials between cell bodies and interstitial fluid.

Front 27

Myelination

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a myelin sheath formed by neuroglial cells. Around most acons. Multi-layered lipid and protine convering axon. Prevent impulses from jumping across neurons and help increase impulse speed.

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Nodes of Ranuier

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gaps along myelin sheath which speed up the rate of impulse transmission.

Front 29

Neurolemma

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outer nucleated cytoplasmic layer of myelin sheath in PNS acons. Help regulate an axon when injured. CNS axons DO NOT have this.

In the PNS each shwann cell forms one sheath between two nodes. In CNS each oligdendrocyte forms sheath aroudn several adjacent axons

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White matter

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area of nervous tissue that consists of myelinated processes of neurons

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Gray matter

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area of nervous tissue that consists of neuron cless bodies, dendrites, axon terminals, unmyelinated axons, and neuroglia. (A nucleus is a cluseter of cell bodies in the CNS.) (the ceribreal cortex is grey matter and where we do our thinking.

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Action Potential

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move along axon

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Graded Potential

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move along dendrites and cell bodies

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resting membrane Potential

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slight negative charge on the inside. Slight positive charge on the outside. Typically about -70 millivolts (mv) on inside. This area of neurons are polarized.

Front 35

Gated Ion Channels

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when these are stimulated to they allow ions to move in or out through plasma membrane.

Front 36

Leakage Ion Channels

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Open randomly. NOt directly involved in graded potential. Maintain resting potential constantly opening and closing and letting K ions out of cell.

Front 37

Volatage-Gated Ion Channel

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open in respons to voltage or change in electrical charge. Pass from one neuron to another at a synapse to produce a graded potential.

Front 38

Ligand-Gated Ion Channel

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Opens in respons to ligands. Important when impulses pass from one neuron to another at a synapse to produce a graded potential. (Ligands are chemicals that bond to receptors)

Front 39

Mechanically-Gated Ion Channel

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open in resonse to vibrations soundwaves, touch, or streching. Important in producing graded potentials in sense receptors

Front 40

Fractors in Maintaining Resting Mambrane Potential

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1. Greater concentraction of neg. charged phosphates and protines on inside of plasma membrane.
2. greater concentration of positivly charged sodium ions on outside
3. membrane is impermeable to Na+ but moderatly permeable to K.
4. *K at higher concentration on inside of neurons. (remember this point)

Front 41

Graded Potentials

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1. Generated by opening ligon-gated or mechanically- gated chennels.
2. usually occur at dendrites or cell bodies. ONly travel to trigger zone. May be summoned to produce action potential
3. variation in amplitude.

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Hyperpolarizing

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makes inside of receiving ion more negitivily charged

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Depolarizing

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makes the inside of neuron less negativily charged. )excitatory or less polarized)

Front 44

Nerve action potential

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temporary depolarization (neuron becomes positive inside) and then repolarization of a part of a neuron. It lasts 1/1000 of a sec. (one thousandth of a second or one millisecond) and involves voltage-gated channels. Ap works by all or none principle. Once initiated at trigger zone they reach a constant amp of +33 MV on inside or proceed to end of axon.

Front 45

Depolarization Phase

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at trigger zone, suffician incoming depolarizing grated potential open voltage gated sodium channes enough so movement of Na+ in brings the number of membrane potenial to a threashold level. . This stimulates activation gates on many nearby voltage gated sodium channels to open suddenly and sodium rushes in by simple difusion to make inside positive. This is called Depolarization.

*K opens slower than Na+*

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Repolarization Phase

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Inactivation gates on Na+ channels close so that Na+ stops rushin in. One gates on K channel opens so K flows out by siffusion to return indise a negative voltage again. These K gates enventually close.

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Refractory Period

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a time period when recently stimulated neurons CANT respond to incoming info. Large diameter axon has a shorter refactory period and thus can transmit more impulses per second.

Front 48

The Na+K+ Pump

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takes 1/3 of our energy to use this. Keeps concentration of Na+ on outside and K+ on inside.

*Novicain blocks nerves by opening Na+ voltage gated channels

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Continuous Conduction

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depolarization of one area of plasma membrane opens the voltage gated Na+ channel in adjacent axons as impulses travel along membrane. C fiber 6 ft per second. A fibers 410 ft per sec.

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Saltatory Conduction

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occurs in myelinated fibers and depolarization of one node of renvier causes Na+ channel only at next to node to open. This is faster and more energy sufficent. (only have to pump ions at nodes. Dont have to pump them in and out) (dull pain traveling along unmeylinated bigers sharp pain travels with asltatory conduction. ex: stubbing your toe. Sharp pain first and then dull pain._ 30 times faster than continuous conduction.

Front 51

Exitatory Postsynaptic Potential (EPSP)

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Neurotransmitter opens cation channel and mainly Na+ flows to make inside more positive. If happens enough an action potential will be gernerated at trigger zone.

Front 52

Inhibitory Postsynaptic Potential (IPSP)

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Neurotransmitter opens Cl- channel to allow Cl-(chlorine) in so inside is more negative. This will decrease the chance of an action potential being generated

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Removal of Neurotransmitter

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Once message is sent across synapse, the neurtransmitter is removed from the synapse by:
Diffusion
Enzymatic Degradation
Re-uptake by presynaptic neurons.

*Prozac interfers with reuptake of serotonin.

You have over 1000 synapses in ONE neuron

Front 54

Spatial Summation

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several presynaptic end bulbs are fireing which increses Neurotransmitter buld up at postsynaptic neuro

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Temperal Summation

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one presynaptic bulb fires many times to increse Neurotransmitter build up at postsynaptic neuron

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Acetylcholine

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exciatory at nuerotranmitter junctions

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Glutamale and Aspartate

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escitatory in CNS

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Gamma and Glycine

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inhibitory in CNS

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ATP and other Purines

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exciatory in CNS and PNS

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Nitric Oxide

2. Enkephalines, endorphoins, and Dynorphins

3. Substance P

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not storesd in vesicals

2. Natural pain killers


3. Pain.