The Central Nervous System

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• The Central Nervous System
• The Story of Phineas Gage
• On 13th. September 1848, an accidental explosion
  of a charge he had set blew his tamping iron
  through his head. 
• The tamping iron was 3 feet 7 inches long and
  weighed 13 1/2 pounds.  It was 1 1/4 inches in
  diameter at one end (not circumference as in the
  newspaper report) and tapered over a distance of
  about 1-foot to a diameter of 1/4 inch at the
  other.  The tamping iron went in point first
  under his left cheek bone and completely out
  through the top of his head, landing about 25 to
  30 yards behind him.  Phineas was knocked over
  but may not have lost consciousness even though
  most of the front part of the left side of his
  brain was destroyed.  Dr. John Martyn Harlow, the
  young physician of Cavendish, treated him with
  such success that he returned home to Lebanon,
  New Hampshire 10 weeks later.

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• I. Functional Anatomy of the Brain
• A. There are four main regions of the brain
  which include
• Cerebral hemispheres (Cerebrum), diencephalon,
  brain stem and the cerebellum

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• B. The Cerebral Hemispheres The paired left and
  right superior parts of the brain and make up
  more than half the mass of the entire brain!
  This part of the brain involves conscious
  behaviors including speech, memory, emotional
  responses, and voluntary movement, personality.
• 1. The surface is made of ridges (gyri) and
  grooves (sulci)
• 2. Fissures (deep grooves) divide the cerebrum
  into lobes
• 3. The outermost area of the cerebrum is made
  of gray matter (covering an underlying layer of
  white matter), and called the cerebral cortex.
  The remaining cerebral hemisphere tissue- the
  deeper white matter- is composed of bundles of
  nerve fibers carrying the impulses to or from
  the cortex.

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• a. One large fiber tract (bundle of nerves)
  called the corpus callosum, connects the right
  and left cerebral hemispheres
• b. The basal nuclei is an internal island of gray
  matter deep within the cerebral cortex. It helps
  regulate the voluntary motor activities.

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Lobes of the Cerebum
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• 4. Surface lobes of the cerebrum include
• a. Frontal lobe
• 1) Primary motor area- allows us to move our
  skeletal muscles under conscious control
• 2) Brocas area- motor speech area that
  directs muscles involved in speech, usually
  only present in left hemisphere.
• 3)High level intellectual reasoning are also
  believed to be in the anterior portion of the
  frontal lobe

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• b. Parietal lobe
• 1. Somatic sensory areas- allows you to
  recognize pain, coldness and touch
• - The left side of the sensory cortex interprets
  impulses from the right side of the body and
  vice versa.

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• c. Occipital lobe
• 1)Visual interpretation
• d. Temporal lobe-
• 1) Auditory interpretation,
• speech, memory, Wernickes
• area (language intrepretation)
• Specialized areas of the Cerebrum

Temporal lobe
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Cerebral Lobe Review

• http//www.youtube.com/watch?vsnO68aJTOpM

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• C. The Diencephalon or Interbrain
• 1. Sits on top of the brain stem and is
  enclosed by the cerebral hemispheres.
• 2. Composed of three main parts Thalamus,
  epithalamus, and hypothalamus
• a. Thalamus- A relay station for sensory
  impulses, allows us to recognize a sensation as
  pleasant or unpleasant, the impulse is eventually
  sent to the sensory cortex for localization and
  interpretation of the sensation

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• b. Hypothalamus- An important part of the
  autonomic system. Its job is regulating body
  temperature, water balance, appetite, and
  metabolism. Also includes the Limbic system- our
  emotional brain. The Limbic system is involved
  in our appetite, thirst, pain, sex, and pleasure
  centers. The pituitary gland is attached to the
  hypothalamus.

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• c. Epithalamus- Forms the roof of the third
  ventricle. Important parts include the pineal
  body(produces melatonin into regulate sleep/wake
  cycles) and choroid plexus (forms cerebrospinal
  fluid).

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• D. The Brain Stem
• 1. Attaches to the spinal cord.
• 2. There are three parts of the brain stem
  midbrain, pons and medulla oblongata.
• a. Midbrain- is mostly composed of
  nerve fiber tracts. It also contains the
  cerebral aqueduct which is a tiny canal that
  connects the third and fourth ventricle.
  The corpora quadrigemina is dorsally
  located with rounded protrusions that are
  reflex centers for vision and hearing.
• b. Pons- The bulging part of the brain
  stem that is composed mostly of nerve fiber
  tracts. It houses important nuclei that
  control our breathing.
• also important because it contains nerve
  fibers connecting the cerebellum to the rest of
  the brain, and allows facial expressions

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• c. Medulla Oblongata- The lowest part of the
  brain stem that merges into the spinal cord. It
  controls important centers that help control
  blood pressure, heart rate, breathing,
  swallowing, and vomiting.
• E. Reticular Formation
• 1. Gray matter that runs along the brain stem.
• 2. Involved in motor control of visceral
  organs. It also contains a special group of
  neurons called the reticular activating system
  that plays a role in consciousness and
  awake/sleep cycles.
• (RAS alerts a person when a friend speaks and
  enables that person to ignore other sounds and
  focus on the one sound.

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• F. The cerebellum
• 1. Projects dorsally from under the occipital
  lobe of the cerebrum. It also contains two
  hemispheres with convoluted surfaces.
• 2. Its job is providing involuntary control of
  body movements (balance), and posture.

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• II. Protection of the Central Nervous System
• A. The scalp and skin provide the first layer of
  protections.
• B. The skull and vertebral column provide the
  second layer.

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• C. A layer of connective tissue called the
  meninges provides the final protection for the
  CNS. There are three meningeal layers.
• 1. Dura mater- the outermost layer that is tough
  and hard.
• 2. Arachnoid mater- the middle web-like layer
• 3. Pia Mater- internal layer that clings to the
  surface of the brain

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The picture below shows a brain with the dura
removed from the cortex exposing the arachnoid
membrane. The tiny protruding white parts seen
near the center of the photo are the visible
arachnoid granulations. The transparent membrane
over the entire brain surface is the arachnoid
membrane.
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• Four Regions of the brain
• Use your notes to write down the four main brain
  regions

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Are you feeling brainy today?
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• D. Cerebrospinal fluid- the fluid that forms a
  watery cushion to protect the brain.
• 1. Its composition is similar to blood plasma
• 2. Formed by the choroids plexus
• 3. Circulated in arachnoid space, ventricles,
  and central canal of the spinal cord
• You tube Cerbrospinal fluid circulation

MRI showing pulsation Of CSF
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Hydrocephalus

• Imbalance in CSF produced and amount absorbed
• Obstruction
• Poor absorption
• Overproduction

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• E. Blood Brain Barrier- The barrier that keeps
  neurons separated from blood borne substances.
  The brain is dependent upon the constant internal
  environment more than any other organ in your
  body.
• 1. The barrier is created by the least permeable
  capillaries in the body.
• 2. The astrocytes contribute to creating this
  barrier.
• 3. Exclusion of many substances helps maintain
  the delicate balance required by the brain.
  However, the barrier fails to prevent the
  following substances from entering
• Fats and fat soluble molecules, Respiratory
  gases, Alcohol, Nicotine, Anesthesia

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Blood Brain Barrier
Meningitis Meningitis is an inflammation of the
membranes that surround the brain and spinal cord
(these membranes are known as meninges).
Meningitis is most commonly caused by infections
with various pathogens, examples of which are
Streptococcus pneumoniae and Haemophilus
influenzae.
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• III. Traumatic Brain Injuries
• A. Concussion- a slight brain injury, victim may
  be dizzy, or lose consciousness briefly but there
  is no permanent brain damage.
• B. Contusion- nervous tissue destruction occurs
  and the tissue does not regenerate. A severe
  brain stem contusion would cause someone to go
  into a coma.
• How are they different?
• Contusions are localized, while concussions are
  widespread. Contusions are macroscopic, while
  concussions are microscopic.BOTH are due to head
  trauma
• BOTH are serious, BOTH are common

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• C. Cerebral Edema (swelling) or hemorrhage
  (bleeding) - Swelling or bleeding of the brain
  due to an inflammatory response. This places
  pressure on brain tissue- this is a serious
  situation.

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• D. Cerebrovascular Accident (CVA) - commonly
  called a stroke. It is the result of a ruptured
  blood vessel supplying a region of the brain.
  The brain tissue that is supplied with oxygen
  from the vessel will die. The loss of function
  depends on the area of the brain affected and the
  severity of the stroke.

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• E. Alzheimers disease- A progressive
  degenerative disease affecting the brain.
  Victims experience memory loss, and confusion.
  (caused by plaques protein deposits- in between
  the neurons)

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• F. Parkinsons disease- A basal nuclei problem
  resulting from the degeneration of dopamine
  releasing neurons. Patients experience tremors,
  a shuffling gait, trouble getting their muscle
  going, and head nodding.

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Meningial LayersProtection for the CNS
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• IV. Spinal Nerves
• A. There is a pair of spinal nerves at the
  level of each vertebra for a total of 31 pairs
• B. Spinal nerves are formed by the combination
  of the ventral and dorsal roots of the spinal
  cord
• C. Spinal nerves are named for the region from
  which they arise

A dermatome is an area of skin that is mainly
supplied by a single spinal nerve.
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• V. Cranial Nerves
• A. Twelve pairs of cranial nerves extend from
  the brain to serve the head and neck region. The
  exception is the vagus nerve which extends into
  the thorax and abdomen.
• B. Most cranial nerves are mixed nerves
  however three pairs are purely sensory. The
  optic (vision), olfactory (smell), and
  vestibulocochlear (balance and hearing). There is
  a chart on pg. 231- 232 that identify each
  cranial nerve by number, origin, function and how
  to test the nerve.

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• Corpus callosum
• Pineal gland/epithalamus
• Cerebellum
• Pons
• Medulla oblongata
• Cerebral cortex
• Brocas area
• Thalamus
• Hypothalamus
• Frontal lobe
• Choroid plexus

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Identify the following brain structures
1
2

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3
8
7
4
6
5
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Question of the week Why Do I Sometimes See
Stars?

• Answer "Seeing stars" is a common visual
  complaint, but it is usually a normal and
  harmless occurrence. If you close your eyes and
  rub them, you will probably see spots and flashes
  of light. These images you see are called
  "phosphenes," an entoptic phenomenon
  characterized by the experience of seeing light
  without light actually entering the eye.
  Phosphenes are produced by pressure on the eyes.
  The pressure is translated into various patterns
  by the optic nerve.These stars, or spots of
  light, that you see can occur after a sneeze, a
  deep cough, a blow to the head or low blood
  pressure (such as standing up too quickly).Some
  people see flashes or lines of light that often
  last up to 10 to 20 minutes. These flashes of
  light are generally caused by a spasm of blood
  vessels in the brain, called a "migraine." If a
  headache follows the flashes, it is called a
  "migraine headache." If these flashes or lines of
  light occur without a headache, it is called an
  "ophthalmic migraine," or migraine without a
  headache.While usually harmless, frequent
  flashes of light can be a warning sign of
  something more serious. A comprehensive eye
  examination will be needed to determine the
  cause.

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Brain Dissection Structures

• External Anatomy Internal Anatomy
• __ Spinal Cord __ corpus callosum
• __ Cerebellum __ pons
• __ Cerebrum __ pituitary gland
• __ Gyri __ lateral ventricle
• __ Sulci __ pineal gland
• __ Olfactory bulb __ midbrain
• __ occipital lobe __ hypothalamus
• __ Optic chiasm __ thalamus
• __ frontal lobe __ medulla oblongata
• __ parietal lobe
• __ temporal lobe

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Sheep Brain
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Cross-section Anatomy
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Study for your test!