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• OrgansOrgans– Brain, Spinal Cord (CNS), and Nerves

(PNS)• FunctionFunction

– Integration of all parts – organs - tissues - cells

– Allows control of parts to enable unification: communication - control -integration - homeostasis - survival

Chapter 10Nervous System

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Chapter 10Nervous System

Cell Types of Cell Types of Neural TissueNeural Tissue

• Neurons• Neuroglial cells

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Divisions of the Nervous System

• Central Nervous System• brain• spinal cord

• Peripheral Nervous System• nerves

• cranial nerves• spinal nerves

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Neuron Structure

Soma

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Structure:• Cell body - Soma• Axon - sends messages away from soma• Dendrite - receives messages from axon to soma.Types of Neurons:• Afferent (sensory) - to spinal cord or brain• Efferent (motor) - away from spinal cord or brain• Interneurons (synapse between 1 and 2) - from

afferent to efferent (from sensory to motor)

Neurons

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Classification of Neurons – Functional Differences

Sensory Neurons• afferent• carry impulse to CNS

Interneurons• link neurons• Found in CNS

Motor Neurons•carry impulses away from CNS• carry impulses to effectors

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Divisions Nervous SystemSee hand out

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Central Nervous SystemBrain and Spinal Cord

1. Peripheral Nervous systemSpinal nerves and Cranial nerves

Outside environment

2. Autonomic nervous system(internal environment – Smooth,Cardiac muscle, Glands)

Somatic Nervous System(Skeletal muscle)

Sympathetic DivisionPrepares body for emergency‘Fight or Flight’

Parasympathetic DivisionSalivation, Urination, Digestion,etc. Active under ordinary, restful conditions.Counterbalances effect of Sympatheticdivision

Sensory and Motor Neurons

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Divisions of Peripheral Nervous System

Sensory Division• picks up sensory information and delivers it to the CNS

Motor Division• carries information to muscles and glands

Divisions of the Motor Division• Somatic – carries information to skeletal muscle• Autonomic – carries information to smooth muscle, cardiac muscle, and glands

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Functions of Nervous System

Sensory Function• sensory receptors gather information• information is carried to the CNS

Integrative Function• sensory information used to create

• sensations• memory• thoughts• decisions

Motor Function• decisions are acted upon • impulses are carried to effectors

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Myelination of Axons

White Matter• contains myelinated axons

Gray Matter• contains unmyelinated structures• cell bodies, dendrites

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• Unmyelinated fibers conduct impulses slower.

• Myelinated fibers conduct impulses faster– Nodes of Ranvier (short region of exposed axon

between Schwann cells on neurons)– The more myelin the faster the impulse

Myelination of Axons

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• Most common disease of the nervous system

• Loss of myelin sheath

• Hard plaque lesions replace myelin

• Nerve conduction is impaired and weakened, loss of coordination, visual impairment and speech disturbances.

• Most common in women between age 20-40

• No known Cure

Multiple Sclerosis

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Reflex Arc

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• Conduction of an impulse to and from the brain and spinal cord.– TypesTypes:

• Two neuron arcTwo neuron arc - - simplest form– Consists of afferent and efferent neurons

• Three neuron arcThree neuron arc - - must common– Consists of afferent, interneurons, and

efferent

Reflex Arc

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Two Neuron Arc

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Three Neuron Arc

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The Synapse

Nerve impulses pass from neuron to neuron at synapses

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Synaptic Transmission

Neurotransmitters are released when impulse reaches synaptic knob = Acetylcholine or AcH

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• Bone is outer cover – Brain - Cranium

– Spinal cord - Vertebrae

• Meninges - inner cover– Dura Mater - outer, white fibrous tissue

– Arachnoid Membrane - cobwebby, middle

– Pia Mater - adheres to brain, transparent

• Meningitis is inflammation of meninges

Brain and Cord Coverings

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Meninges

Meninges

Grey matter

White matter

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Spinal Cord

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• 17 - 18 in. in length• Two bulges

– Cervical region - sends nerves to upper limbs

– Lumbar region - sends nerves to lower limbs

• Grey Matter– Inner core, looks like an H in cross section, made of

interneurons and motor neuron somas

• White Matter– Surrounds gray matter, consists of nerve fibers in

bundles (axons and dendrites)

Spinal Cord

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• 31 pairs - they are numbered according to where they are located.

• Emerge from cord through foramen of vertebrae.

• Each nerve level attaches to a body section– Dermatone - patches of skin that correspond to each nerve.

• Herpes Zoster - (causes chicken pox and shingles) lies dormant at the ends of nerves.– Causes eruptions of red swollen patches which are very

painful

Spinal Nerves

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Spinal nerves

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Dermatomes

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Spinal nerves

• Broken neck at 3, 4, or 5 vertebrae = damage to phrenic nerve– This nerve controls the diaphragm

– Without artificial respiration, patient will die.

Spinal Nerves

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• Size– 3 pounds

– Larger in men than women

– Larger in young than old

– Full size by age 18

– Contains 100 billion neurons

Brain

http://www.cbsnews.com/2100-500165_162-6890474.html

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Brain

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Brain stem

oblongata

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Divisions of the Brain

• Brainstem– Midbrain– Pons– Medulla oblongata

• Cerebellum

• Diencephalon

• Cerebrum

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• Medulla Oblongata– Most vital part of the brain– Injury or disease proves fatal– Lowest part of brainstem– Function

• Vital centers - cardiac, dilates blood vessels (drops and increases blood pressure), respiratory

• Nonvital centers - vomiting, coughing, sneezing, hiccupping, swallowing.

Divisions of the Brainstem

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• Pons

–Above the medulla oblongata

–Function• Helps regulate respiration gases, chewing, saliva secretion, hearing

Divisions of the Brainstem

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• Midbrain– Located above the pons and below

the cerebrum

– Function• Reflex center: eye movements, hearing

Divisions of the Brainstem

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• Second largest part of the brain• Function

– Maintains equilibrium– Helps control posture– Smoothes movements instead of being jerky, trembling

or uncoordinated

• Diseases (hemorrhage, tumor)– Cause ataxia - muscle incoordination

• Diagnose with a finger to nose test

– Tremors– Disturbances of walk and balance

Cerebellum

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• Located between the midbrain and cerebrum

• Consists of the hypothalamus and thalamus– HypothalamusHypothalamus: regulator of autonomic

activities; mind-body link (tears); maintains water balance, waking state, appetite, and body temperature

– ThalamusThalamus: recognizes sensations of pain, temp., and touch; relays sensory impulses to cerebrum; associates sensory impulses to emotions, arousal or alerting mechanism

Diencephalon

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Cerebrum

Gyrus/ fold

Cerebellum

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• Largest part of the brain

• Consists of two halves and 5 lobes– Right hemisphere

• Spatial abilities - see whole picture

– Left hemisphere• Analytical skills

Cerebrum

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• Five Lobes– Frontal - forehead

– Parietal - posterior top

– Temporal - temples

– Occipital - posterior base

– Insula - hidden from view

Cerebrum

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• Function– Sensory: visual and auditory

– Motor ability: movement of muscles

– Integrative ability:

• Ability to receive sensory impulses and send motor impulses.

• Consciousness: state of awareness

• Memory: major mental activity

• Use of language: ability to speak and write words and understand words

• Emotions

Cerebrum

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Cerebrum

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http://www.pbs.org/wgbh/nova/assets/swf/1/mapping-the-brain/mapping-the-brain.html

http://www.pbs.org/wgbh/nova/body/brain-trauma.html

http://www.pbs.org/wgbh/nova/body/psychology-magic.html

http://www.pbs.org/wgbh/nova/body/mirror-neurons.html

http://www.pbs.org/wgbh/nova/body/how-memory-works.html