Title: The Nervous System
1The Nervous System
Unit K
2 Central Nervous System
- Communication and coordination system of the body
- Seat of intellect and reasoning.
- Consists of the brain, spinal cord, and nerves.
3Neuron
- -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 bodymay be one or more
4- Myelin Sheath
- Myelin is a fatty substance that protects axon
- speeds transmission along axon - Called
neurilemma
- Axon
- -Carries impulses away from the cell body
- -Only one on a neuron
5NERVE IMPULSE
- A STIMULUS creates an IMPULSE.
- Impulse to dendrite to axon to neurotransmitter
to synapse.
6SYNAPSE
- A space between neurons, messages go from one
cell to another.
7SENSORY NEURONS (AFFERENT)
- Emerge from the skin or sense organs.
- Carry impulses to spinal cord and brain.
8MOTOR NEURONS (EFFERENT)
- Carry messages from brain and spinal cord to
muscles and glands.
9ASSOCIATIVE NEURONS (INTERNEURONS)
- Carry impulses from sensory neurons to motor
neurons.
10NEUROGLIA
- Cells that insulate, support and protect the
neurons, nerve glue.
11CENTRAL NERVOUS SYSTEM
Divisions of the Nervous System
- The brain and spinal cord
12Autonomic Nervous System
- Peripheral nerves and ganglia
- Supplies heart muscle, smoother muscle and
secretory glands - Involuntary i.e. automatic responses to injury
like shock and increased heart rate
13Peripheral Nervous System (PNS)
- Cranial nerves and spinal nerves are part of the
PNS
14The Brain
- 3lb mass of soft nervous tissue
- 100 billion neurons
- Protected by skull, 3 membranes called meninges,
and cerebrospinal fluid (shock absorber)
Cerebrum
15- 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
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17Coverings of the Brain (MENINGES)
- Meninges surrounds the brain and spinal cord
18- DURA MATER- outer brain covering, lines inside of
skull, tough, fluid-containing - dense fibrous
connective tissue - Layers dura mater, subdural, arachnoid,
subarachnoid, pia mater
19Coverings contd
- Subdural space
- is between the dura and arachnoid space
Next layer is the Arachnoid layer - middle layer
resembles fine cob web
20- SUBARACHNOID SPACE- between arachnoid and pia
mater, filled with CEREBROSPINAL FLUID which acts
as a liquid shock absorber and as a source of
nutrients for the brain
21Coverings contd
- PIA MATER
- innermost layer of the meninges
- covers the brains surface, comprised of blood
vessels held together by connective tissue
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23Ventricles of the Brain
- Brain contains four cavities filled with
cerebrospinal fluid called CEREBRAL VENTRICLES.
24Ventricles of the Brain (cont.)
- CHOROID PLEXUS- network of blood vessels lining
the ventricles which helps in the formation of
cerebrospinal fluid. - CEREBROSPINAL FLUID
- Forms inside ventricles of the brain.
- Serves as a liquid shock absorber
25- 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. -
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27 CEREBRUM
- Largest part of the brain
- Divided into R and L hemispheres by deep groove
- CONVULTIONS- elevated folds on the surface of the
cerebrum, they increase the surface area of the
brain
28SULCI - fissure or grooves separating cerebral
convolutions Divided into four lobes FRONTAL
(voluntary muscle movement), PARIETAL, OCCIPITAL
and TEMPORAL
29CEREBRAL FUNCTION
- Conscious thought, judgment, memory, reasoning,
and will power. - - responsible for maintaining consciousness,
- decision making, recalling information
- and normal speech
- These people were not
- using their cerebrum.
30- DIENCEPHALON
- Located between cerebrum and midbrain
- Composed of THALAMUS and HYPOTHALAMUS
31- Vital functions of the hypothalamus
- 1. Autonomic nervous control
- 2. Temperature control
- 3. Appetite control
- 4. Emotional state
- 5. Sleep control
32- CEREBELLUM
- 2nd largest part of brain
- Composed of two hemispheres
- below the cerebrum
- Controls all body functions related to skeletal
muscles, including - Balance, walking
- Muscle tone
- Coordination of muscle movements
33- Controls all body functions related to skeletal
muscles, including - Balance, walking
- Muscle tone
- Coordination of muscle movements
34BRAIN STEM
- Made up of PONS, MEDULLA and MIDBRAIN
- Pons in front of cerebellum, between midbrain
and medulla contains center that controls
respiration - Midbrain controls vision and hearing
- Medulla oblongata bulb-shaped structure between
pons and spinal cord, inside the cranium above
foramen magnum (opening in vertebral column) - - Responsible for
- 1. Heart rate
- 2. Blood pressure
Click for picture
35SPINAL CORD
- Begins at foramen magnum and continues down to
2nd lumbar vertebrae - White and soft, in spinal canal
- Surrounded by cerebrospinal fluid
- FUNCTIONS AS
- Reflex center
- Conduction pathway to and from the brain
Injury to spinal cord difficulty with movement
(paraplegia paralysis of legs) and problems
breathing
36 Peripheral Nervous System
- All of the nerves outside the central nervous
system - NERVES
- Contains sensory and motor nerves (afferent and
efferent)
37 Cranial Nerves
- 12 pairs
- Begin in the brain
- Designated by number and name
38On Old Olympus Towering Top A Finn
And German Vault And Hop
Mnemonic for the 12 cranial nerves
39- SPINAL NERVES
- Originate at spinal cord and go through openings
in vertebrae - 31 pairs of spinal nerves
- All are mixed (afferent and motor) nerves
- Named in relation to their location on the spinal
cord
40- 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 -
41- Parasympathetic Nervous system counters SNS
decreases heart rate, decreases respiratory rate,
etc - REFLEX
- Unconscious and involuntary
- In a simple reflex, only a sensory nerve and
motor nerve involved example knee-jerk
reflex
42Disorders of the Nervous System
- MENINGITIS
- Inflammation of the lining of the brain and
spinal cord - May be bacterial or viral
- Symptoms- headache, fever and stiff neck, nausea
and vomiting - In severe form, may lead to paralysis, coma and
death - If bacterial, may be treated with antibiotics
- Dx by removing csf with a needle lumbar puncture
43- 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
44CEREBRAL PALSY
- Disturbance in voluntary muscular action due to
brain damage. - May be due to birth injury or abnormal brain
development - Spastic Quadriplegia- spastic paralysis in all
four limbs. - Sx- head rolling, grimacing,
- difficult speech and swallowing
- No impairments of intellect.
45- POLIOMYELITIS
- Viral disease of nerve pathways of spinal cord-
causing progressive muscle weakness leading to
paralysis - Almost eradicated in USA (vaccine)
- DEMENTIA
- Loss of 2 areas of complex behavior, such as
languages, memory, visual and spatial abilities,
or judgment - Interferes with persons daily life.
46HYDROCEPHALUS
- Increased volume of cerebrospinal fluid within
ventricles of the brain. - Usually, blockage in 3rd and 4th ventricle
- Enlargement of the head, usually noticed at
birth. - Bypass or shunt performed to relieve pressure.
47- ALZHEIMERS DISEASE
- Progressive disease that begins with problems
remembering characterized by early senility,
confusion, and loss of recognition of persons - Nerve endings in cortex of brain degenerate and
block signals that pass between nerve cells - Abnormal fibers build up creating tangles
48- Cause Unknown
- 1st stage (2-4 yrs) involves confusion,
short-term memory loss, anxiety, poor judgment - 2nd stage (2-10 yrs) increase in memory loss,
logic problems, and loss of social skills - 3rd stage (1-3 yrs) inability to recognize
oneself, weight loss, seizures, mood swings and
aphasia
49- PARKINSONS DISEASE
- Symps - tremors, shuffling gait, pill-rolling,
and muscular rigidity. - Decrease in neurotransmitter dopamine
- RX- L-dopa and other drugs to treat symptoms.
50- MULTIPLE SCLEROSIS (MS)
- Chronic inflammatory disease of CNS - autoimmune
- Immune cells attack myelin sheath of axon-myelin
sheath destroyed, leaving scar tissue on nerve
cellstransmission of nerve impulses blocked.
51- Cause- UNKNOWN
- Sx- weakness of extremities, numbness, double
vision, nystagmus, speech problems, loss of
coordination, possible paralysis. - Typically strikes young adults age 20-40, mostly
women - Rx- Avonex- slows progression
52 Cerebral Vascular Accident
- Stroke or CVA
- Interruption of blood and O2 to the brain
blockage of blood to the brain - Tissue death
- Third leading cause of death in USA
- PARALYSIS- loss of power of motion or sensation
- HEMIPLEGIA- paralysis on one side of the body
Symptoms ?
53- Risk Factors
- Smoking
- Hypertension
- Heart disease
- Family history
- Causes of CVA
- 90 caused by blood clots
- Clots lodge in carotid arteries, blocking the
flow of blood to the brain - 10 caused by ruptured blood vessels in the
brain
54- SYMPTOMS
- Hemiplegia on the opposite side of the body
- Sudden, severe headache
- Dizziness
- Sudden loss of vision in one eye
- Aphasia
- Dysphasia
- Coma
- Possible death