1Chapter 10 Key Terms

AcetylcholineEpinephrineAfferent NeuronsEfferent NeuronsAstrocytesAxonAxon TerminalsDopamineDendritesEndorphinsNeuronsReflex ArcSchwann CellsSynapseSerotoninGray MatterHorns

Dura Mater

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ANATOMY & PHYSIOLOGYCHAPTER 10: NERVOUS SYSTEM

INTRODUCTION, SPINAL CORD, AND SPINAL NERVES

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Nervous System

Control system of the bodyControls organs and systems of the body Interprets stimuli from environmentHelps us react to those stimuliHelps maintain homeostasis

4Nervous System

CNSBrain

Spinal Cord

PNSCranial nervesSpinal nerves

Afferent Efferent

Somatic Autonomic

Sympathetic Parasympathetic

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Organization

Central Nervous System (CNS)Controls the whole system Includes brain and spinal cord

Peripheral Nervous System (PNS)Consists of all nerves that connect the CNS with

sensory receptors, muscles, and glandsDivided into two categories

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Organization

PNSAfferent Peripheral System

Take info from sensory receptors to CNS

Efferent Peripheral SystemTake info from CNS to muscles and glands

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Organization

EfferentAutonomic Nervous System (ANS)

Impulses from CNS to smooth muscle, cardiac muscle, and glands

Involuntary

Somatic Nervous System (SNS)Impulses from CNS to skeletal muscleVoluntary

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Organization

ANSSympathetic division

Speeds up activity“Fight or flight” responseUses norepinephrine as neurotransmitter

Parasympathetic“Rest and digest” responseStimulates vegetative activities (digestion…)Uses acetylcholine as neurotransmitter

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Classification of Nerve Cells

Nervous tissue is a composition of 2 types of cellsNeuroglia (glial cells) – “nerve glue”

Support and protect neuronsMake up 60% of all brain cells

NeuronsNerve cells that transmit nerve impulses through

electrochemical changes

NervesBundle of nerve cells or fibers

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Classification of Nerve Cells

NeurogliaAstrocyte: attach nerve cell to blood vessel for

nutrientsOligodendoglia: support between nerve cellsMicroglial: protect CNS by destroying microbesEpendymal: line fluid-filled cavities of brainSchwann: form myelin sheath around nerve fibers in

PNS

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Structure of a

Neuron

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Structural Classification

MultipolarContains several dendrites and one axon

BipolarOne dendrite and one axonTwo processes come off the cell

UnipolarOnly one process from the bodyMost sensory neurons

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Functional Classification

Sensory Neuron (Afferent)Receive impulse directly from receptorUnipolar neurons

Association NeuronTransmit impulse to appropriate part of brain for processingMultipolar neurons found in brain and spinal cord (most

common) Motor Neuron (Efferent)

Final cell to receive impulse – causes reaction to the stimulus

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Nerve Impulse

Neuron contains concentrations of ions inside and outside of cellGreater concentration of Na+ ions outside of cellGreater concentration of K+ ions inside cellConcentration maintained by sodium-potassium pump

Resting PotentialPositive charge outside cell, negative charge inside

cell

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Nerve Impulse

Depolarization (Action Potential)Na+ rush into cell, causing positive charge inside cellAs this happens, K+ move outside to restore resting

potential Repolarization

Sodium-Potassium pump restores equilibriumPumps sodium back outside cell membrane and

potassium back inside cell membrane Transmission occurs only at nodes of Ranvier

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Nerve Impulse

All-or-None Law If a nerve fiber carries any

impulse, it will carry a full strength impulse

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Synaptic Transmission

SynapseArea where axon terminals

are anchored close to dendrites of another neuron

Neurotransmitters connect to receptors on postsynaptic neuron

This triggers an influx of sodium in postsynaptic neuron

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Synaptic Transmission

Acetylcholine is the most common neurotransmitter Acetylcholinesterase breaks down Acetylcholine

after it has performed its function Other notable neurotransmitters:

SerotoninEpinephrineDopamineEndorphins

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Reflexes

Involuntary reaction to an external stimulus Reflex Arc

Pathway that results in a reflex5 parts

Sensory receptor in skinAfferent/Sensory neuronAssociation neuron in spinal cordEfferent/Motor neuronEffector (Muscle)

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Common Reflexes

Knee-jerk reflex Blushing Cough reflex Shivering Yawning Babinski Reflex (Video) Eye-blink reflex

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Spinal Cord

Begins as continuation of the brain stem

Surrounded and protected by vertebrae (bone) and intervertebral disks (fibrocartilage)

Made up of 31 segments Also protected by a series of

connective tissue membranes called spinal meninges

Also protected by cerebrospinal fluid

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Spinal Cord

FunctionsTransmit impulses to and from the brainAlso is center for reflexes

Posterior/Dorsal RootContains only sensory fibers

Anterior/Ventral RootContains only motor fibers

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Spinal Cord

Posterior Gray HornSensory fibers

Anterior Gray HornMotor fibers

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Spinal Nerves

5 regions for the 31 spinal nervesCervical (8)Thoracic (12)Lumbar (5)Sacral (5)Coccygeal (1)