Nervous System Part 5
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Transcript Nervous System Part 5
Chapter 7 – Part 5
The Nervous System
Protection of the Central Nervous
System
1.
2.
3.
4.
Scalp and skin
Skull and vertebral column
Meninges
Cerebrospinal fluid
5. Blood brain
barrier
Meninges
The three connective tissue membranes
covering and protecting the CNS
structures are meninges.
Three Layers:
1. Dura Mater
2. Arachnoid Mater
3. Pia Mater
Meninges
1. Dura Mater – Outer
most layer
Feels tough & leathery
Folds inward in several
areas
Double-layered external covering
1. Periosteum – Attached to the inner
surface of the skull
2. Meningeal Layer – Outer covering of
the brain
Meninges
2. Arachnoid
Layer – Middle
meningeal layer
Web-like
3. Pia Mater – Innermost membrane of
the meninges
Clings tightly to the surface of the brain and
spinal cord, following every fold
Delicate layer
Cerebrospinal Fluid
Similar to blood
plasma composition
Formed by the choroid
plexus
Forms a watery cushion to protect the
brain
Continually circulated in arachnoid
space, ventricles, and central canal of
the spinal cord
Ventricles and Location of the
Cerebrospinal Fluid
Meningitis
Meningitis - Inflammation of
the meninges
Serious threat to the brain
because bacterial or viral meningitis
may spread into the nervous system of
the CNS.
Usually diagnosed by taking a sample of
cerebrospinal fluid
Procedure is called a lumbar (spinal)
tap
Blood Brain Barrier
No other body organ is so absolutely
dependent on a constant internal
environment as is the brain.
Other body tissues can withstand the rather
small fluctuations in the concentrations of
hormones, ions, and nutrients that continually
occur, particularly after eating or exercise.
If the brain were exposed to such chemical
changes, uncontrolled neural activity might
result!
Remember that certain ions are involved in
initiating nerve impulses and some amino
acids serve as neurotransmitters.
Blood Brain Barrier
Neurons are kept separated
from bloodborne substances
by a blood-brain barrier.
Composed of the least
permeable capillaries of the
body.
Only water, glucose and
essential amino acids can easily
pass through the walls of these
capillaries.
Metabolic wastes (urea, toxins,
proteins, and most drugs) are
prevented from entering the
brain.
Blood Brain Barrier
The following contribute to the barrier:
1. Astrocytes
2. Relative impermeability of the capillaries Most responsible for providing this
protection
Useless against some substances
Fats and fat soluble molecules
Respiratory gases
Alcohol
Nicotine
Anesthesia
Traumatic Brain Injuries
Concussion
Slight brain injury
May be dizzy, “see stars”,
or lose consciousness
briefly
No permanent brain
damage
Contusion
Nervous tissue destruction
occurs
Nervous tissue does not
regenerate
Shows an area of subarachnoid hemorrhage with
bleeding and an area of brain contusion where
the white ischemic brain has died
Traumatic Brain Injuries
Cerebral Edema –
Swelling of the brain
due to inflammatory
response to injury
Hemorrhaging –
Bleeding from
ruptured vessels
Traumatic Brain Injuries
After head blows,
death may result from
intracranial hemorrhage
or from cerebral edema.
Both may compress and
kill brain tissue
Individuals who are
initially alert and lucid
following head trauma
and then begin to deteriorate neurologically later
are most likely hemorrhaging or suffering the
consequences of edema.
Cerebrovascular Accident (CVA)
Commonly called a stroke
Third leading cause of
death in the US
Occur when blood
circulation to a brain
area is blocked (blood
clot or a ruptured blood
vessel)
Brain tissue supplied with oxygen from that
blood source dies
Loss of some functions or death may result
Cerebrovascular Accident (CVA)
• Fewer than 1/3 of those surviving a CVA
are alive 3 years later.
• Some patients recover at least partly,
because undamaged neurons spread
into areas where neurons have died and
take over some lost functions.
• Most of the recovery seen after brain
injury is due to this phenomenon.
Alzheimer’s Disease
Progressive
degenerative
brain disease that
ultimately results in
dementia (mental
deterioration)
Structural changes in
the brain include
abnormal protein
deposits and twisted
fibers within neurons
Alzheimer’s Disease
Mostly seen in the elderly,
but may begin in middle
age
Victims experience
memory loss, irritability,
confusion and ultimately,
hallucinations and death
5-15% of people over 65
develop this condition.
Parkinson’s Disease
Cause: Results from a
degeneration of the
dopamine-releasing
neurons, and as those
neurons degenerate, the
dopamine-deprived basal
nuclei they target become overactive
Typically strikes people in their 50s and 60s
(Michael J. Fox is an exception)
Cause of Parkinson’s is still unknown
Parkinson’s Disease
Symptoms include:
1. Persistent tremor at rest
exhibited by head
nodding and “pill-rolling”
movement of the fingers
2. Forward-bent walking
posture and shuffling
gait
3. Stiff facial expression
4. Trouble initiating
movement or getting
their muscles going
Huntington’s Disease
Genetic disease that leads to
massive degeneration of the
basal nuclei and later of the
cerebral cortex
Strikes during the middle age
Symptoms:
Initial - wild, jerky, and almost continuous
flapping movements
Later - marked mental deterioration
Progressive and usually fatal within 15 years of
onset of symptoms
Treatment of Parkinson’s and
Huntington’s Disease
Parkinson’s Disease
Signs and Symptoms – Inhibition of the
motor drive
Treatment – Usually treated with drugs that
enhance dopamine’s effects
Huntington’s Disease
Signs and Symptoms - Overstimulation of
the motor drive (opposite of Parkinson’s
disease)
Treatment – Usually treated with drugs that
block dopamine’s effects