Nervous

System

Health Science I

The Nervous System Divisions• Central nervous system (CNS)• Communication and coordination system of the body• intellect and reasoning• brain and spinal cord

• Peripheral Nervous system (PNS)aka sensory-somatic• cranial nerves and spinal nerves

• Autonomic Nervous system (ANS)• Peripheral nerves and ganglia • Sympathetic• Parasympathetic

Cellular Structures of the Nervous System

• Neuron• Nerve cell• Transmits a message from one cell to the next• Has a nucleus, cytoplasm, and cell membrane

• Dendrites• Nerve cell processes that carry impulse to cell body• May be one or many

• Axon• Carries impulse away from cell body• Only one on a neuron

Cellular Structures of the Nervous System

• Myelin sheath (neurilemma)• Covering that speeds up the nerve impulse along the

axon• Myelin is a fatty substance that protects the axon

• Synapse• Space between neurons, messages go from one cell to

the next

Types of Neurons

• Sensory Neurons (AFFERENT)• 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

Summarize

•Describe the structures of the neuron? What types are there? What is the difference between them?

Structures of the Central Nervous System

• Brain• 3 lb. mass of soft nervous tissue• 100 billion neurons• Protected by skull, three membranes called meninges,

and cerebrospinal fluid (CSF)• Adequate blood supply is needed, brain tissue will die

in 4-8 mins without O2

• Divided into 4 major parts: cerebrum, diencephalon, cerebellum, brain stem

Structures of the Central Nervous System

• Cerebrum (higher brain function takes place here)• Largest part of the brain• Divided into R and L hemispheres by deep groove

(longitudinal fissure)• Convolutions: elevated folds on the surface of the

cerebrum, they increase the surface area of the brain• Sulci: fissure or grooves separating cerebral

convolutions• Divided into four lobes: frontal, parietal, occipital and

temporal

Structures of the Central Nervous System

• Diencephalon• Located between cerebrum and midbrain• Composed of Thalamus, Hypothalamus, Pineal body,

Pituitary gland

• Limbic system• Located in the center of the brain• Encircles the top of the brain stem

Structures of the Central Nervous System• Cerebellum(little

brain)• Located behind the

pons and below the cerebrum• Composed of two

hemispheres• functions-maintain

posture, coordinates.

Structures of the Nervous System

• Brain stem- connect brain to spinal cord• Consist of Midbrain,

Pons and Medulla oblongata• Pathway for ascending

and descending tracts

Summarize

•Describe the structures of the brain

Structures of the Central Nervous System

• Meninges• Dura mater• Outermost layer lines inside of skull, tough dense fibrous

connective tissue• Arachnoid• Middle layer resembles fine cobweb

• Pia mater• Innermost layer comprised of blood vessels held together by

connective tissue

Structures of the Central Nervous System

• Subdural Space between dura and arachnoid• Subarachnoid space between arachnoid and pia

mater,filled with CSF acts as shock absorber and source of nutrients

CRABOf

DEATH

SUBDURALHEMMORHAGE

Structures of the Central Nervous System

• Ventricles • Right and left lateral ventricles• Third ventricle behind and below the lateral ventricles• Fourth ventricle is below the 3rd, in front of the

cerebellum and behind the pons and medulla oblongata• lined cavities deep within the brain• filled with cerebrospinal fluid• Choroid plexus – rich network of blood vessels

Structures of the Central Nervous System

• Cerebrospinal Fluid (CSF)• Forms inside ventricles of the brain• Serves as a liquid shock absorber protecting the brain

and spinal cord• Blood-brain Barrier – choroid plexus capillaries prevent

substances (like drugs) from penetrating brain tissue – this makes infections, like meningitis, difficult to cure

• Lumbar Puncture (LP)• removal of CSF from spinal canal, needle puncture

between 3rd and 4th lumbar vertebrae

•What are the structures of the brain? https://www.youtube.com/watch?v=IwofyN198YU

Structures of the Central Nervous System

• Spinal Cord (spinal reflexes, nerve impulse)• Begins at foramen magnum and continues down to 2nd

lumbar vertebrae• White and soft, in spinal canal• Surrounded by cerebrospinal fluid, vertebrae, and

meninges

Spinal tap video

• http://www.youtube.com/watch?v=R2_0gOI8uV0

STRUCTURES OF THE PERIPHERAL NERVOUS SYSTEM

• All of the nerves of the body and ganglia• Cranial nerves • Spinal nerves

• Autonomic nervous system is special part of PNS

STRUCTURES OF THE PERIPHERAL NERVOUS SYSTEM

• Nerves• Bundle of nerve fibers enclosed by connective tissue• Sensory, motor or mixed

• Cranial Nerves• 12 pairs• Begin in the brain• Designated by number and name

Cranial nerves• I. Olfactory• II. Optic• III. Oculomotor• IV. Trochlear• V. Trigeminal• VI. Abducens

• VII. Facial• VIII.

Vestibulocochlear• IX.

Glossopharyngeal• X. Vagus• XI. Accessory• XII. Hypoglossal

• http://www.youtube.com/watch?v=KEGb1qndBnc• http://

www.youtube.com/watch?v=a0vtkXMr7qQ

STRUCTURES OF THE PERIPHERAL NERVOUS SYSTEM

• Spinal Nerves• Start at spinal cord and go through openings in

vertebrae• 31 pairs of spinal nerves• All are mixed nerves• Named in relation to their location on the spinal cord

Structures of the Autonomic Nervous system

• Regulates activities of visceral organs • Not subject to conscious control, controls

involuntary or automatic activities

the Autonomic Nervous system• Parasympathetic Nervous• counters effects of SNS,

decreases heart rate

• Sympathetic Nervous System• From the base brain, and both

sides of the spinal cord• These nerves connect to all

internal organs• the “fight or flight” system –

when the body perceives danger, SNS sends message to adrenal medulla to secrete adrenaline – heartbeat increases

Functions of the central nervous system

• Neurons• Sensory neurons-emerge from the skin or sense

organs, carry impulses to spinal cord and brain• Motor neurons-carry messages from brain and spinal

cord to muscles and glands• Associative neurons-carry impulses from sensory

neurons to motor neurons

• repeat

Functions of the cerebrum

• Frontal Lobe• controls motor functions, R side controls voluntary

movement of the L; 2 areas for speech

EmotionsPersonality

MoralityIntellectSpeech

Broca’s Area

Functions of the cerebrum

• Parietal Lobe• Sensory area, receptors for pain, touch, heat, and cold

Sensory MotorPain

TouchHeat

Functions of the cerebrum

• Occipital Lobe• visual area, controls eyesight

Vision

Functions of the cerebrum

• Temporal Lobe• Auditory area, olfactory area

Hearing Smell

Functions of the Cerebrum

• Cerebral cortex• Covers the brain, aka gray matter• Controls conscious thought, judgment, memory,

reasoning, and willpower

Functions of the cerebellum

• Maintain balance and muscle tone• Coordinate muscle movement, control of all

voluntary movement• Injury or removal results in motor impairment

Function of limbic system

• Acts as brains pleasure center• Dopamine is released from limbic system• Controls fear, aggression and rage

Functions of the Diencephalon

• Thalamus • Relays sensory stimuli to cerebrum

• Hypothalamus• Autonomic nervous control, cardiac control,

temperature control, appetite control, water balance, oxytocin manufactured, GI control, emotional state and sleep control• 9 vital functions

Function of the brainstem

• Midbrain• Responsible for vision and hearing

• Pons • Respiratory control

• Medulla Oblongata • Heart rate and B/P control, depth and rate of

respiration, swallowing and vomiting

Function of the spinal cord and CSF

• Spinal cord• Reflex center and conduction pathway to and from the

brain

• CSF• Shock absorber, transports nutrients and removes

waste

Functions of the peripheral nervous system

• Control the automatic or involuntary activities of the body• To act as reflex center of the body• Why can spinal cord and PNS both be reflex

centers???

Function of the cranial nerves• I. smell• II. vision eyesight• III. eye movement• IV. Eye movement• V. face and teeth

muscle/chewing• VI. eye movement

• VII. Facial Expression• VIII. Hearing and

balance• IX. Throat muscle and

taste• X. throat muscles,

heart, digestive system• XI. neck mov’t• XII. tongue mov’t

Function of the spinal nerves

• Sends messages to and from spinal cord and brain to all parts of the body

Functions of the ANS

• Regulates activities of visceral organs • Sympathetic Nervous System• Speeds up heart rate w/ fear• Causes secretion of adrenaline

• Parasympathetic Nervous System • Slows HR• Reverses the sympathetic response

https://www.youtube.com/watch?v=tm-YGOFhhHE

Reflex act

• Unconscious and involuntary• Receptors pick up stimuli ( in heat, light, etc.)

and react is called response• In a simple reflex, only a sensory nerve and

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

Disorders of the Nervous System

• Alzheimer’s disease• Cerebral palsy• Epilepsy• Hydrocephalus• Meningitis• Multiple sclerosis

• Neuritis• Paralysis• Parkinson’s disease• Poliomyelitis• Spinal cord injury• West Nile virus

Alzheimer’s Disease• Progressive disease that begins with problems

remembering• Nerve endings in cortex of brain degenerate and

block signals that pass between nerve cells• Called plaques

• Abnormal fibers build up creating tangles• Cause – unknown could be virus, genetics, or

environmental factors

Alzheimer’s Disease

• First stage (2-4 years) involves confusion, short-term memory loss, anxiety, poor judgment• 2nd stage (2-10 years) increase in memory loss,

difficulty recognizing people, motor problems, logic problems, and loss of social skills• 3rd stage (1-3 years) inability to recognize oneself,

weight loss, seizures, mood swings and aphasiahttps://www.youtube.com/watch?v=yJXTXN4xrI8

Cerebral palsy

• Disturbance is voluntary muscular action due to brain damage• Cause- unknown, may be from birth injury or

abnormal brain development• Symptoms: head rolling, grimacing, difficulty with

speech or swallowing and spastic quadriplegia (muscle tightens)• No impairment of intellect

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• Rx- anticonvulsants

Did you know Van Gough had

Epilepsy?

Hydrocephalus

• Increased volume of CSF w/in ventricles of the brain• Cause: blockage in 3rd or 4th ventricle• Head enlargement• Rx: shunt or bypass to prevent pressure buildup• http://www.youtube.com/watch?v=bHD8zYImKq

A

Meningitis

• Inflammation of the lining of the brain and spinal cord• May be bacterial or viral• Symptoms – headache, fever and stiff neck• In severe form, may lead to paralysis, coma and

death• If bacterial, may be treated with antibiotics

Multiple sclerosis (MS)

• Inflammatory disease of CNS when immune cells attack myelin sheath destroying sheath and delaying or blocking nerve impulses• Cause: unknown• Symptoms: weakness in extremities, dbl vision,

nystagmus, speech problems, loss of coordination and possible paralysis

Multiple sclerosis (MS)• Usually strikes ppl 20-40 yrs. old and 2/3 are

women• Disease has flare ups and is progressive• Rx: Medications treat flare up and slow

progression, rest, exercise, and minimal stress

Montel WilliamsAndJack OsborneHave MS

neuritis• Inflammation of a nerve or nerve trunk• Symptoms: pain, hypersensitivity, loss of

sensation, muscular atrophy, weakness, paresthesia (tingling, burning, crawling of skin)• Causes- infection, chemical, or other dx such as

alcoholism• Rx- eliminate cause and relieve symptoms

Paralysis

• Loss of power of motion or sensation• Hemiplegia- paralysis to one side of the body• Cause- stroke, spinal cord injury, nerve disorders

(ALS-Lou Gehrigs disease, Polio, Bell’s Palsy)• Rx- rehab to prevent atrophy, may never regain

use of affected area

Parkinson’s disease

• Symptoms: tremors, shuffling gait, pill-rolling hands, difficulty initiating mov’t and muscular rigidity• Cause: decrease in dopamine production• Rx- no cure, medications to replace dopamine (L-

dopa) and treat symptoms

Poliomyelitis

• Infections of nerve pathways in spinal cord that causes paralysis• Symptoms: Headache, sore throat, vomiting• Rx- Vaccine, treat symptoms

Spinal cord injury

• Causes- Assault, falls, gunshot wounds, motor vehicle accidents, sports injuries (particularly diving into shallow water), arthritis, cut, pull or bleeding in spinal cord• Symptoms: spasticity, numbness, sensory

changes, weakness, paralysis• Rx- surgery, steroids, braces, rehab

Spinal cord injury

• How well a person does depends on the level of injury. Injuries near the top of the spine lead to more disability than injuries low in the spine• Complications: respiratory illnesses,

bed sores, UTI, incontinence, DVT, and contractures

Spinal cord injury

West Nile virus

• Virus passed by infected mosquito's, typically affects very young/old and immunocompromised • Symptoms: abdominal pain, fever, diarrhea,

swollen lymph nodes, rash, muscle aches and can lead to encephalitis or meningitis• Rx- Treat symptoms, wait for virus to clear (3-6

days)