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)