The Human brain
The most complex mechanism
known
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
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.
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
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.
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
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.
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.
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
Hypothalamus continued…
• Appetite and satiety (fullness) regualte
food intake.
• Influences sexual behavior, emotional
aspects of sensory input, pleasure, and
pain.
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.
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
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.
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.
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.
• 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.