The Human brain

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The Human brain

• The most complex mechanism known

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Human brain

• 25 billion neurons
• Require continuous supply of oxygen and glucose
• If brain deprived of blood it results in damage
  (ex- stroke)
• Hollow organ
• Fluid filled spaces called ventricles

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The medulla

• Most posterior portion of the brain stem
• Continuous with the spinal cord
• Consists of white matter (nerve tracts) and gray
  matter (cell bodies), carries messages to and
  from spinal cord
• Motor fibers cross here, right brain controls
  lefts side of body, left brain controls right
  side.

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Medulla continued

• Gray and white matter known as the reticular
  formation extend from the spinal cord through the
  medulla and upward through the brain stem and
  thalamus.
• It keeps cerebrum conscious and alert
• Also houses several vital reflex centers

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Reflex centers of the medulla

• 1. cardiac centers that control heart rate
• 2. vasomotor centers that help reg. blood
  pressure by controlling the diameter of blood
  vessels.
• 3. respiratory centers that initiate and reg.
  breathing.

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The pons

• Forms a bulge on the anterior surface of the
  brain stem.
• Continuous with medulla.
• Consists of nerve fibers passing from medulla to
  other parts of the brain.
• Helps reg. respiration

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The midbrain

• Shortest portion of brain stem.
• Has bundles of neurons connecting the lower
  portion of the brain with spinal cord.
• Contains reflex centers for vision and hearing.

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The diencephalon includes thalamus and
hypothalamus

• Thalamus
• Major relay center
• Controls all sensory info except smell

• Hypothalamus
• Control center of the autonomic center. Link
  between mind and body.
• Links nervous system with endocrine system.
• Produces 2 hormones ADH (anti diuretic hormone)
  and oxytocin.

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Hypothalamus continued

• Oxytocin stimulates contraction of the uterus
  during childbirth and release of milk). ADH
  (prevents production of dilute urine) and
  oxytocin are stored in the posterior lobe of the
  pituitary gland.
• Helps maintain fluid balance by reg. the volume
  of water excreted by the kidneys. Also contains a
  thirst center to let us know when we need fluids.
• Regulates body temperature

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Hypothalamus continued

• Appetite and satiety (fullness) regualte food
  intake.
• Influences sexual behavior, emotional aspects of
  sensory input, pleasure, and pain.

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The cerebellum

• Responsible for coordination of movement
• 2nd largest part of the brain
• Contains 2 lateral masses called hemispheres and
  a connecting portion.
• Helps make movements smooth and steady rather
  than trembling
• Helps maintain muscle tone and posture
• Impulses from the organ of balance (vestibular
  apparatus) in the inner ear are continuoulst
  delivered to the cerebellum which maintains
  equilibrium.

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The cerebrum

• Largest part of the brain and most prominent.
• Controls motor activities, interprets sensation,
  serves as the center of intellect, memory,
  language, and consciousness.
• Divided into hemispheres
• cerebral cortex- thin outer layer of the
  cerebrum, consists of gray matter

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Hemispheres of the cerebrum cont

• Basal ganglia- lie within the white matter of
  the cerebrum, play an important role in movement.
  
• The two cavities in the cerebrum are called the
  lateral ventricles.
• The brain in folded into convolutions and in
  between them are shallow grooves called sulci and
  the deep pockets are called fissures.
• The cerebrum is partially divided into right and
  left halves called the right and left cerebral
  hemispheres. They are separated by a deep groove
  called the longitudinal fissure.

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The cerebrum has sensory, motor, and association
functions

• Sensory functions receives info from sense
  receptors and interprets these messages
• Motor functions motor areas of the cerebrum are
  responsible for all voluntary movement and for
  some involuntary movement
• Association functions learning and reasoning,
  memory storage and recall, language abilities and
  even consciousness.

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Lobes of the cerebrum specialize in certain
functions

• Frontal lobe- motor cortex, formation of words.
• Parietal lobe- receives info from skin and joints
  integrates info with visual, auditory and sensory
  association.
• Occipital lobe- receives info from the thalamus
  about what we see and integrates the info in
  order to formulate an appropriates response.

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• Temporal lobe- reception and integration of
  auditory messages
• Limbic lobe- a link between emotional and
  cognitive thought.
• Central lobe- involved with somatic and autonomic
  activities.