The Nervous The Nervous SystemSystemPart 1Part 1

““Organization of the Nervous Organization of the Nervous System”System”

Parkinson’s and Alzheimer’s disease both affect the nervous Parkinson’s and Alzheimer’s disease both affect the nervous system.system.

*The nervous system is the “wiring” that keeps the body connected and functioning. *Works with the endocrine system to keep the body in homeostatic balance. *The nervous system also enables us to learn, form memories and allow for critical and creative thinking in ways not fully understood.

Parkinson’s kills dopamine producing cells, so there is nothing to stop muscle contractions.

Alzheimer's affects memory cells.

Organization of theOrganization of the Nervous System Nervous System

Central Nervous System (CNS)Central Nervous System (CNS) Brain and spinal cordBrain and spinal cord makes decisions makes decisions made up of tracts of fibersmade up of tracts of fibers

Peripheral Nervous System Peripheral Nervous System (PNS)(PNS) Cranial and spinal nervesCranial and spinal nerves Relays info to and from the CNSRelays info to and from the CNS made up of Nervesmade up of Nerves

Organization of the Organization of the Peripheral Nervous SystemPeripheral Nervous System

Afferent Divisions (Sensory Afferent Divisions (Sensory messages)messages) carries info towards the CNScarries info towards the CNS

Efferent Divisions (Motor messages)Efferent Divisions (Motor messages) carries info away from the CNScarries info away from the CNS

Organization of the Organization of the Peripheral Nervous SystemPeripheral Nervous System

Somatic Nervous System (SNS) VoluntarySomatic Nervous System (SNS) Voluntary Controls skeletal musclesControls skeletal muscles Somatic sensory divisionSomatic sensory division :(afferent) stimulus from :(afferent) stimulus from

muscle receptors to the CNS.muscle receptors to the CNS. Somatic motor divisionSomatic motor division: (efferent) response from : (efferent) response from

CNS to skeletal musclesCNS to skeletal muscles

Autonomic Nervous System (ANS) InvoluntaryAutonomic Nervous System (ANS) Involuntary Controls smooth and cardiac muscles, glandsControls smooth and cardiac muscles, glands Visceral sensory divisionVisceral sensory division: (afferent) stimulus from : (afferent) stimulus from

organ receptors to CNS. organ receptors to CNS. Visceral motor divisionVisceral motor division: (efferent) response from : (efferent) response from

CNS to organsCNS to organs Sympathetic and parasympathicSympathetic and parasympathic

Divisions of Autonomic Divisions of Autonomic Nervous SystemNervous System

Involuntary part of the peripheral nervous systemInvoluntary part of the peripheral nervous system

Sympathetic DivisionSympathetic Division ““Fight or flight” responseFight or flight” response Takes over to deal with immediate threatsTakes over to deal with immediate threats

Parasympathetic DivisionParasympathetic Division ““Rest and repair” divisionRest and repair” division Coordinates normal resting activitiesCoordinates normal resting activities

The Nervous The Nervous SystemSystemPart 2Part 2

““Cells of the Nervous System”Cells of the Nervous System”

Cells of the Nervous Cells of the Nervous SystemSystem Neurons (nerve cells)Neurons (nerve cells)

Excitable cells that Excitable cells that transmit signalstransmit signals

Neuroglia (glial cells)Neuroglia (glial cells) Are support cells for Are support cells for

the neuronsthe neurons Sometimes called Sometimes called

“nurse” cells“nurse” cells

NeuronsNeuronsKey PartsKey Parts No centrioles because No centrioles because

amitoticamitotic Soma or cell body -contains

the nucleus Nissl bodies - ribosomes to

make neurotransmitters. Dendrites(receptors) -

receive signals Axon - long arm extending

away from cell body, transmits signal away from cell body to next neuron

Axons can have side branches called axon collaterals.

Path of Nerve ImpulsePath of Nerve ImpulseDendrite Dendrite cell body cell body axon axon synapse synapse

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Structural Classification of Structural Classification of NeuronsNeurons

A. MultipolarA. Multipolar Most neurons in brain and spinal Most neurons in brain and spinal

cord are multipolarcord are multipolarB. BipolarB. Bipolar

Only one axon and dendriteOnly one axon and dendrite Least numerousLeast numerous Found in eye, inner ear and noseFound in eye, inner ear and nose

C. UnipolarC. Unipolar One end branches toward CNS One end branches toward CNS

while the other goes toward PNSwhile the other goes toward PNS Two processes form a long axonTwo processes form a long axon Carries both sensory and motor Carries both sensory and motor

info.info.

TYPES OF GLIAL CELLSTYPES OF GLIAL CELLSA.A. AstrocytesAstrocytes

B.B. MicrogliaMicroglia

C.C. Ependymal cellsEpendymal cells

D.D. OligodendrocytesOligodendrocytes

E.E. Schwann cellsSchwann cells

F.F. Satellite cellsSatellite cells

AstrocyteAstrocyte

Astrocytes- ‘star cells’Astrocytes- ‘star cells’ Found only in the CNSFound only in the CNS Largest and most Largest and most

numerous type of glianumerous type of glia Bridge between Bridge between

capillaries and neurons capillaries and neurons filter harmful filter harmful

substances and substances and transport nutrients.transport nutrients.

They form the blood-They form the blood-brain barrier (BBB)brain barrier (BBB)

MicrogliaMicroglia

MicrogliaMicroglia

Found in CNSFound in CNS Small and Small and

stationarystationary Fight infection in Fight infection in

brain tissue brain tissue through through phagocytosis.phagocytosis.

Ependymal cellsEpendymal cells

Ependymal cellsEpendymal cells

Found only in CNSFound only in CNS Line fluid-filled Line fluid-filled

cavities in the brain cavities in the brain and spinal cordand spinal cord

Form Cerebrospinal Form Cerebrospinal fluid (CSF)fluid (CSF)

Cilia helps keep fluid Cilia helps keep fluid circulating through circulating through brain and spinal brain and spinal cord.cord.

MyelinMyelin

Whitish fatty material that increases Whitish fatty material that increases speed of conduction in an axonspeed of conduction in an axon

Insulates nerve fiber axonsInsulates nerve fiber axons Myelinated fibers are called white matterMyelinated fibers are called white matter Non-myelinated fibers are called gray Non-myelinated fibers are called gray

mattermatter Destroyed in individuals with multiple Destroyed in individuals with multiple

sclerosissclerosis

Schwann CellsSchwann Cells

Schwann CellsSchwann Cells

Found only in PNSFound only in PNS Form myelin Form myelin

sheaths around sheaths around cells of the PNS.cells of the PNS.

Gaps between Gaps between schwann cells are schwann cells are called called nodes of nodes of ranvierranvier..

OligodendrocytesOligodendrocytes

OligodendrocytesOligodendrocytes

Found only in CNSFound only in CNS Produce the fatty Produce the fatty

myelin sheath myelin sheath around the nerve around the nerve fibers of CNSfibers of CNS

Hold nerve fibers Hold nerve fibers togethertogether

Quick CheckQuick Check

1.1. What is the difference between What is the difference between neurons and glial cells?neurons and glial cells?

2.2. What does myelin do?What does myelin do?

3.3. Which glial cell makes myelin in the Which glial cell makes myelin in the CNS?CNS?