Central Nervous SystemCentral Nervous System

Communication and coordination system Communication and coordination system of the bodyof the body

Seat of intellect and reasoning.Seat of intellect and reasoning.

Consists of the Consists of the brain, spinal cord, and brain, spinal cord, and nerves.nerves.

NeuronNeuron-Nerve cell

-Transmits a message from one cell to another

-Has a nucleus, cytoplasm, and cell membrane

Dendrites

Nerve cell processes that

carry impulse to cell body…may be one or more

AxonAxon

--Carries impulses Carries impulses away from the away from the cell bodycell body

-Only one on a -Only one on a neuronneuron

Myelin Sheath

•Myelin is a fatty substance that protects axon

•speeds transmission along axon - Called neurilemma

NERVE IMPULSE

A STIMULUS creates an IMPULSE.

Impulse to dendrite to axon to neurotransmitter to synapse.

SYNAPSE

A space between neurons, messages go from one cell to another.

SENSORY NEURONS (AFFERENT)

Emerge from the skin or sense organs.

Carry impulses to spinal cord and brain.

MOTOR NEURONS

(EFFERENT)

Carry messages from brain and spinal cord to muscles and glands.

ASSOCIATIVE NEURONS (INTERNEURONS)

Carry impulses from sensory neurons to motor neurons.

NEUROGLIA

Cells that insulate, support and protect the neurons, nerve glue.

CENTRAL CENTRAL NERVOUS NERVOUS SYSTEMSYSTEM

The brain The brain and spinal and spinal cordcord

Divisions of the Nervous System

Autonomic Nervous SystemAutonomic Nervous System

Peripheral nerves and gangliaPeripheral nerves and ganglia

Supplies heart muscle, smoother Supplies heart muscle, smoother muscle and secretory glandsmuscle and secretory glands

Involuntary Involuntary i.e. automatic responses to i.e. automatic responses to injury like shock and increased heart injury like shock and increased heart raterate

Peripheral Nervous System (PNS)

Cranial nerves Cranial nerves and spinal and spinal nerves are nerves are part of the part of the PNSPNS

The BrainThe Brain 3lb mass of soft

nervous tissue

100 billion neurons

Protected by skull, 3 membranes called meninges, and cerebrospinal fluid (shock absorber)

Cerebrum

Adequate blood supply is needed, brain tissue will die in 4-8 mins without O2

Divided into 4 major parts: cerebrum, diencephalon (near midbrain), cerebellum, brain stem

Coverings of the Brain Coverings of the Brain ((MENINGESMENINGES))

Meninges surrounds the brain and spinal cord

DURA MATER- DURA MATER- outer brain covering, lines inside of skull, tough, fluid-containing - dense fibrous connective tissue

Layers = dura mater, subdural, arachnoid, subarachnoid, pia mater

Coverings cont’dCoverings cont’d

Subdural space Subdural space is between the dura

and arachnoid space

Next layer is the ArachnoidArachnoid layer- middle layer – resembles fine cob web

SUBARACHNOID SPACE-

SUBARACHNOID SPACE-

between arachnoid and pia mater,

between arachnoid and pia mater,

filled with filled with CEREBROSPINAL

CEREBROSPINAL

FLUIDFLUID which

which acts as a liquid

acts as a liquid

shock absorber

shock absorber and as a source of

and as a source of

nutrients for the brain

nutrients for the brain

Coverings cont’dCoverings cont’d

PIA MATERPIA MATER

innermost layer of the meningesinnermost layer of the meninges

covers the brain’s surface, covers the brain’s surface, comprised of blood vessels held comprised of blood vessels held together by connective tissuetogether by connective tissue

Ventricles of the BrainVentricles of the Brain

Brain contains Brain contains four cavities filled four cavities filled with cerebrospinal fluid called with cerebrospinal fluid called CEREBRAL VENTRICLESCEREBRAL VENTRICLES..

Ventricles of the Brain (cont.)Ventricles of the Brain (cont.)

CHOROID PLEXUS- CHOROID PLEXUS- network of blood network of blood vessels lining the ventricles vessels lining the ventricles which which helps in the formation of helps in the formation of cerebrospinal fluid.cerebrospinal fluid.

CEREBROSPINAL FLUIDCEREBROSPINAL FLUID Forms inside ventricles of the brain.Forms inside ventricles of the brain. Serves as a liquid shock absorberServes as a liquid shock absorber

BLOOD-BRAIN BARRIER- choroid plexus capillaries prevent substances (like drugs) from penetrating brain tissue – this makes infections, like meningitis, difficult to cure.

LUMBAR PUNCTURE- removal of CSF from spinal canal, needle puncture between 3rd and 4th lumbar vertebrae.

CEREBRUMCEREBRUM Largest part of the brainLargest part of the brain

Divided into R and L hemispheres by Divided into R and L hemispheres by deep groovedeep groove

CONVULTIONS- CONVULTIONS- elevated folds on elevated folds on the surface of the cerebrum, they the surface of the cerebrum, they increase the surface area of the increase the surface area of the brainbrain

SULCI - fissure or grooves separating cerebral convolutions

Divided into four lobes – FRONTAL (voluntary muscle movement), PARIETAL, OCCIPITAL and TEMPORAL

CEREBRAL FUNCTIONCEREBRAL FUNCTIONConscious thought, Conscious thought,

judgment, memory, judgment, memory, reasoning, and will reasoning, and will power.power.

- - responsible for responsible for maintaining maintaining consciousness, consciousness,

decision making, decision making, recalling information recalling information

and normal speechand normal speechThese people were notThese people were not

using their cerebrum.using their cerebrum.

DIENCEPHALONDIENCEPHALON Located between cerebrum and Located between cerebrum and

midbrainmidbrain Composed of Composed of THALAMUSTHALAMUS and and

HYPOTHALAMUSHYPOTHALAMUS

Vital functions of the hypothalamus:

1. Autonomic nervous control 2. Temperature control 3. Appetite control 4. Emotional state 5. Sleep control

CEREBELLUMCEREBELLUM 22ndnd largest part of brain largest part of brain Composed of two Composed of two

hemisphereshemispheres below the cerebrumbelow the cerebrum Controls all body functions Controls all body functions

related to skeletal muscles, related to skeletal muscles, including:including:o Balance, walkingBalance, walkingo Muscle toneMuscle toneo Coordination of muscle Coordination of muscle

movementsmovements

Controls all body functions Controls all body functions related to skeletal muscles, related to skeletal muscles, including:including:

o Balance, walkingBalance, walkingo Muscle toneMuscle toneo Coordination of muscle Coordination of muscle

movementsmovements

BRAIN STEMBRAIN STEM Made up of Made up of PONSPONS, , MEDULLAMEDULLA and and MIDBRAINMIDBRAIN Pons – in front of cerebellum, between midbrain Pons – in front of cerebellum, between midbrain

and medulla – contains center that controls and medulla – contains center that controls respirationrespiration

Midbrain – controls vision and hearingMidbrain – controls vision and hearing Medulla oblongata Medulla oblongata – bulb-shaped structure – bulb-shaped structure

between pons and spinal cord, inside the cranium between pons and spinal cord, inside the cranium above foramen magnum (opening in vertebral above foramen magnum (opening in vertebral column)column)

- - Responsible for:Responsible for: 1. Heart rate1. Heart rate 2. Blood pressure2. Blood pressureClick for picture…

Begins at foramen magnum Begins at foramen magnum and continues down to and continues down to 22ndnd lumbar vertebraelumbar vertebrae

White and soft, in spinal canalWhite and soft, in spinal canal Surrounded by cerebrospinal Surrounded by cerebrospinal

fluidfluid

FUNCTIONS AS:FUNCTIONS AS:

1.1. Reflex centerReflex center

2.2. Conduction pathway to and Conduction pathway to and from the brainfrom the brain

SPINAL CORDSPINAL CORD

Injury to spinal cord Injury to spinal cord = = difficulty with movement difficulty with movement (paraplegia – paralysis of legs) (paraplegia – paralysis of legs) and problems breathingand problems breathing

Peripheral Nervous SystemPeripheral Nervous System

All of the nerves outside the All of the nerves outside the central nervous systemcentral nervous system

NERVESNERVES Contains sensory and motor Contains sensory and motor

nerves (afferent and nerves (afferent and efferent)efferent)

Cranial NervesCranial Nerves12 pairs12 pairs

Begin in the brainBegin in the brain

Designated by number and nameDesignated by number and name

On Old Olympus’ToweringTopAFinn AndGermanVaultAndHop

SPINAL NERVESSPINAL NERVES

Originate at spinal cord and go through Originate at spinal cord and go through openings in vertebraeopenings in vertebrae

31 pairs of spinal nerves31 pairs of spinal nerves

All are mixed (afferent and motor) nervesAll are mixed (afferent and motor) nerves

Named in relation to their location on the spinal Named in relation to their location on the spinal cordcord

AUTONOMIC NERVOUS SYSTEM Regulates activities of visceral organs (i.e. beating of heart) Not subject to conscious control SYMPATHETIC NERVOUS SYSTEM- the “fight or flight” system- when the body perceives danger, SNS sends message to adrenal medulla (above kidney) to secrete adrenaline - heartbeat increases, resp rate increases, etc•

• PARASYMPATHETIC NERVOUS PARASYMPATHETIC NERVOUS SYSTEM SYSTEM counters SNS – decreases heart counters SNS – decreases heart rate, decreases respiratory rate, etcrate, decreases respiratory rate, etc

REFLEXREFLEX Unconscious and involuntaryUnconscious and involuntary In a simple reflex, only a sensory nerve In a simple reflex, only a sensory nerve

and motor nerve and motor nerve involved – example involved – example “knee-jerk” reflex“knee-jerk” reflex

Disorders of the Nervous SystemDisorders of the Nervous SystemMENINGITISMENINGITIS

Inflammation of the lining of the brain Inflammation of the lining of the brain and spinal cordand spinal cord

May be bacterial or viralMay be bacterial or viral

Symptoms- Symptoms- headache, fever and stiff headache, fever and stiff neck, nausea and vomitingneck, nausea and vomiting

In severe form, may lead to paralysis, In severe form, may lead to paralysis, coma and deathcoma and death

If bacterial, may be treated with If bacterial, may be treated with antibioticsantibiotics

Dx by removing csf with a needle = Dx by removing csf with a needle = lumbar puncturelumbar puncture

EPILEPSY

Seizure disorder of the brain, characterized by recurring and excessive discharge from neurons

Seizures believed to be result of spontaneous, uncontrolled electrical activity of neurons

Cause – Uncertain

Victim may have hallucinations and seizures

Grand mal – severe, convulsive seizure

Petit mal - milder

CEREBRAL PALSYCEREBRAL PALSY

• Disturbance in Disturbance in voluntary muscular action voluntary muscular action due to brain damage.due to brain damage.

• May be due to birth injury or abnormal May be due to birth injury or abnormal brain developmentbrain development

• Spastic Quadriplegia- spastic paralysis in Spastic Quadriplegia- spastic paralysis in all four limbs.all four limbs.

• Sx- Sx- head rolling, grimacing, head rolling, grimacing, difficult speech and swallowingdifficult speech and swallowing• No impairments of intellectNo impairments of intellect..

POLIOMYELITISPOLIOMYELITIS

• ViralViral disease of nerve disease of nerve pathways of spinal cord- pathways of spinal cord- causing causing progressive muscle progressive muscle weakness leading to weakness leading to paralysisparalysis

• Almost Almost eradicatederadicated in USA in USA (vaccine)(vaccine)

DEMENTIADEMENTIA

• Loss of 2 areas of complex Loss of 2 areas of complex behavior, such as languages, behavior, such as languages, memory, visual and spatial memory, visual and spatial abilities, or judgmentabilities, or judgment

• Interferes with person’s daily Interferes with person’s daily life.life.

HYDROCEPHALUSHYDROCEPHALUS

• Increased volume of cerebrospinal fluid Increased volume of cerebrospinal fluid within ventricles of the brain.within ventricles of the brain.

• Usually, blockage in 3Usually, blockage in 3rdrd and 4 and 4thth ventricle ventricle• Enlargement of the head, usually noticed Enlargement of the head, usually noticed

at birth.at birth.• Bypass or shunt performed to relieve Bypass or shunt performed to relieve

pressure.pressure.

ALZHEIMER’S DISEASEALZHEIMER’S DISEASE

Progressive disease that Progressive disease that begins with problems begins with problems remembering – characterized remembering – characterized by early senility, confusion, by early senility, confusion, and loss of recognition of and loss of recognition of personspersons

Nerve endings Nerve endings in cortex of in cortex of brain brain degeneratedegenerate and block and block signals that pass between signals that pass between nerve cellsnerve cells

Abnormal fibers build up Abnormal fibers build up creating tanglescreating tangles

Cause – UnknownCause – Unknown 11stst stage (2-4 yrs) involves confusion, short- stage (2-4 yrs) involves confusion, short-

term memory loss, anxiety, poor judgmentterm memory loss, anxiety, poor judgment 22ndnd stage (2-10 yrs) increase in memory stage (2-10 yrs) increase in memory

loss, logic problems, and loss of social skillsloss, logic problems, and loss of social skills

33rdrd stage stage (1-3 yrs) inability to recognize (1-3 yrs) inability to recognize oneself, weight loss, seizures, mood swings oneself, weight loss, seizures, mood swings and and aphasiaaphasia

PARKINSON’S DISEASEPARKINSON’S DISEASE

• Symps - Symps - tremorstremors, , shuffling gaitshuffling gait, pill-, pill-rolling, and muscular rolling, and muscular rigidity.rigidity.

• Decrease in Decrease in neurotransmitter neurotransmitter dopaminedopamine

• RX- L-dopa and other RX- L-dopa and other drugs to treat drugs to treat symptoms.symptoms.

MULTIPLE SCLEROSIS (MS)

•Chronic inflammatory disease of CNS - autoimmune

•Immune cells attack myelin sheath of axon-myelin sheath destroyed, leaving scar tissue on nerve cells…transmission of nerve impulses blocked.

• Cause- UNKNOWNCause- UNKNOWN

• Sx- weakness of extremities, Sx- weakness of extremities, numbness, double numbness, double vision, vision, nystagmus, speech problems, loss of nystagmus, speech problems, loss of

coordination, possible paralysis.coordination, possible paralysis.

• Typically strikes young adults age 20-Typically strikes young adults age 20-40, mostly 40, mostly womenwomen

• Rx- Avonex- slows progressionRx- Avonex- slows progression

Cerebral Vascular AccidentCerebral Vascular Accident

StrokeStroke or CVA or CVA Interruption of blood Interruption of blood

and O2 to the brain – and O2 to the brain – blockage of blood to blockage of blood to the brainthe brain

Tissue deathTissue death Third leading cause Third leading cause

of death in USAof death in USA

PARALYSIS- loss of power of motion

or sensationHEMIPLEGIA-

paralysis on one side of the body

Symptoms →

Risk FactorsRisk Factors SmokingSmoking HypertensionHypertension Heart diseaseHeart disease Family historyFamily history

Causes of CVACauses of CVA 90% caused by blood clots90% caused by blood clots Clots lodge in carotid arteries, blocking the flow of Clots lodge in carotid arteries, blocking the flow of

blood to the brainblood to the brain 10% caused by ruptured blood vessels in the brain10% caused by ruptured blood vessels in the brain

SYMPTOMSSYMPTOMS Hemiplegia on the opposite side Hemiplegia on the opposite side

of the bodyof the body Sudden, severe headacheSudden, severe headache DizzinessDizziness Sudden loss of vision in one eyeSudden loss of vision in one eye AphasiaAphasia DysphasiaDysphasia ComaComa Possible deathPossible death