Central Nervous System

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The History of the study of the Brain

• Early brain studies used the method of
  phrenology.
• Phrenology examination of the skull where bumps
  and indentations are used to make a mental map
  and were then related to the character of that
  person.
• The end of World War II and the massive quantity
  of brain injuries leads many people to examine
  the brain on a deeper level.
• New technologies like the MRI have allowed
  doctors to observe the brain in operation in
  incredible detail.

http//skepdic.com/phren.html
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Overview The Nervous System

• Central Nervous System (CNS) Brain Spinal
  Cord
• Peripheral Nervous System Nerves to rest of
  body
• Sensory nerves carry messages from the body to
  the brain
• Motor nerves carry messages from the brain to the
  body

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Central Nervous System - Anatomy Function -
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The Human Spinal Cord
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The Spinal Cord

• The main pathway for information connecting the
  brain and peripheral nervous system
• - Conducts sensory information from the
  peripheral nervous system (both somatic and
  autonomic) to the brain.
• - Conducts motor information from the brain
  to the various effectors (skeletal muscles,
  cardiac muscle, smooth muscle, glands).
• Serves as a minor coordinating center responsible
  for some simple reflexes (e.g., withdrawal
  reflex).
• The average spinal cord is 45 cm long in men and
  43 cm long in women. The spinal cord weighs
  approximately 35 g.

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The Spinal Cord Vertebrae

• The human spinal cord is protected by the bony
  spinal column. The spinal column is made up of
  bones called vertebrae.
• The spinal cord is located in the vertebral
  foramen and is made up of 30 segments 7
  cervical, 12 thoracic, 5 lumbar, 5 sacral and 1
  coccyx. A pair of spinal nerves exits from each
  segment of the spinal cord.

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• The vertebral column provides structural support
  for the trunk and surrounds and protects the
  spinal cord.
• The vertebral column also provides attachment
  points for the muscles of the back and ribs.
• The vertebral disks serve as shock absorbers
  during activities such as walking, running, and
  jumping. They also allow the spine to flex and
  extend. Common injury Ruptured Disk

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Famous Spinal Cord Injuries

• Mike Utley 1991 Detroit Lions Offensive Lion
  fractured his 6th and 7th cervical vertebrae.

http//www.mikeutley.org/images/mike.gif
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• Christopher Reeves
• Well, I totally decimated my first cervical
  vertebra and my second, and so my body and my
  spine and my head were not connected. Only my
  neck muscles were holding my head on, and
  fortunately I didn't suffer any brain damage, at
  least none that I can detect. laughter But, you
  know, that's what they tell me at any rate. But
  they literally had to put my head back on my
  body, and a wonderful surgeon, Dr. John Jane at
  the University of Virginia, was the one who
  operated on me, and they had to make it up. They
  had never done anything like this before, because
  this is what is called a hangman's injury, you
  know, like if you get dropped through the trap
  door and then cut down, sent to rehab and told to
  have a nice life.

http//record.wustl.edu/archive/2000/12-01-00/phot
os/reeves.jpg
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How does the brain protect itself?
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Four ways the brain protects itself

• 1. Skull -
• 2. Meninges
• 3. Cerebrospinal Fluid
• 4. Blood Brain Barrier (BBB)

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Central Nervous System- The Coverings of the
Brain (Shocks)
Meninges

• Both the brain and the spinal cord are covered in
  three continuous sheets of connective tissue, the
  meninges.
• The dura mater (the dura) the outer layer
• The arachnoid the middle layer
• The pia mater (the pia) the inner layer
• The meninges PAD the brain

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http//www.baltimoresun.com/media/photo/2004-05/12
819309.jpg
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Central Nervous System- Cerebrospinal Fluid
(CSF) -
The entire surface of central nervous system is
bathed by a clear, colorless fluid, called
cerebrospinal fluid (CSF). The CSF is contained
within a system of fluid-filled cavities called
ventricles.

• The total volume of CSF is 125-150 ml
• Normal resting pressure of the CSF is between
  150-180 mmH2O.
• Total production of CSF is about 400-500 ml/day
  (about 0.36 ml/min)

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Central Nervous System- Cerebrospinal Fluid
(CSF) -

• What does the CSF do?
• Protection The CSF protects the brain from
  damage by buffering the brain.
• Buoyancy The pressure at the base of the brain
  is reduced by immersing in the CSF.
• Excretion of waste products The one-way flow
  from the CSF to the blood takes potentially
  harmful metabolites, drugs and other substances
  away from the brain.
• Endocrine medium for the brain The CSF serves to
  transport hormones to other areas of the brain.

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Central Nervous System - Blood-Brain Barrier
(BBB) -
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What is the Blood-Brain Barrier (BBB) ?
The barrier exists between the blood and the
brain
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BBB History

• The late 19th century, Paul Ehrlichs experiment
  Certain dyes (e.g., a series of aniline
  derivatives) administered intravenously to small
  animals stained all the organs except the brain
  The brain has a lower affinity for the dye than
  the other tissues.
• In 1913, Edwin G. Goldmans experiment
• The dye trypan blue, directly injected into
  the cerebrospinal fluid of rabbits or dogs,
  readily stained the entire brain but did not
  enter the bloodstream to stain the other internal
  organs The CNS is separated from the blood by a
  barrier of some kind.

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BBB History

• The late 1960s
• Electron microscopy confirmed the hypothesis
  that brain capillaries provide the anatomical
  basis of the BBB
• Recent studies
• - The BBB is present in all vertebrate brains
• - The BBB is laid down within the first 3
  months of human fetal life

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BBB FunctionNeuroprotective Role
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BBB Function

• Physical Barrier
• To protect the brain tissues from foreign
  substances or certain chemicals in the blood
  that may injure the brain

Biological Shield or Safeguard
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BBB FunctionNeuroprotective RoleObstacle
to Drug Delivery
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• In order to cross the BBB in
  pharmacologically significant amounts, the
  therapeutic drugs must have the following
  characteristics
• Lipid soluble
• Have a molecular weight lt 400 Daltons
• Not be a substrate for a BBB active efflux
  transporter

This class of drugs constitutes lt2 of all
potential small molecule drugs. Only few brain
disorders, such as depression, schizophrenia,
chronic pain, and epilepsy, respond to such
drugs. 100 of large molecule drugs and 98 of
small molecule drugs do not cross the BBB.
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Reflection

• Of the four protective functions, which do you
  think would be most important in the field of
  psychology? Why?