Transcript The Brain

The Brain
The brain is composed of the cerebrum, cerebellum,
and brainstem.
The cerebrum is the largest part of the brain and is
composed of right and left cerebral hemispheres. It
performs higher functions like interpreting touch,
vision and hearing, as well as speech, reasoning,
emotions, learning, and fine control of movement.
cerebrum
The outer 4 mm surface of the cerebrum is called the
cerebral cortex. The cortex contains about 70 - 75% of
the 100 billion neurons of the brain. The neuron cell
bodies, or gray matter, is at the surface and it has a
folded structure. Beneath the gray matter are long,
myelinated axons, which make up the white matter of
the cortex.
The folding of the cortex increases the brain’s surface
area allowing more neurons to fit inside the skull and
enabling higher functions. Each fold is called a
convolution or gyrus, and each groove between folds
is called a sulcus.
Lobes of the Cerebrum
The cerebral hemispheres
have distinct fissures,
which divide each
hemisphere has four
lobes: frontal, temporal,
parietal, and occipital.
Each lobe may be divided into areas that serve very
specific functions. It’s important to understand that
each lobe of the brain does not function alone. There
are very complex relationships between the lobes of
the brain and between the right and left hemispheres.
Frontal lobe
•Personality, behavior, emotions
•Judgment, planning, problem solving
•Speech: speaking and writing (Broca’s area)
•Body movement (motor strip)
•Intelligence, concentration, self awareness
Parietal lobe
•Interprets language, words
•Sense of touch, pain, temperature (sensory strip)
•Interprets signals from vision, hearing, motor, sensory
and memory
•Spatial and visual perception
Occipital lobe
•Interprets vision (color, light, movement)
Temporal lobe
•Understanding language (Wernicke’s area)
•Memory
•Hearing
•Sequencing and organization
The cerebellum is located under the cerebrum. Its
function is to coordinate voluntary muscle movements
and to maintain posture and balance.
cerebellum
The brainstem includes the midbrain, pons, and
medulla oblongata. Some texts include the
diencephalon as a brain stem structure, but others
include it in the forebrain. The brain stem acts as a
relay center connecting the cerebrum and cerebellum
to the spinal cord and performs many of the body’s
automatic functions.
diencephalon
midbrain
pons
medulla oblongata
The medulla oblongata lies between the pons and the
spinal cord. It contains centers which control key,
autonomic body functions and it relays nerve signals
between the brain and spinal cord. Important control
centers include:
•The respiratory center – controls
the rate, rhythm, and depth of
breathing
•The cardiac center – regulates
heartbeat
•The vasomotor center – controls
blood pressure
•Reflex centers – reflex arc centers
for vomiting, coughing, sneezing,
hiccupping and swallowing
The Pons is an enlarged structure located just below
midbrain and above the medulla oblongata. The
word “pons” is the Latin word for “bridge” and
indicates the function of the pons. It acts as a relay
station between the lower centers and the higher
centers of the brain. The 5th through the 8th cranial
nerves connect directly to the pons.
The midbrain (also called the mesencephalon) is
located between the diencephalon and the pons. It also
acts as a relay station between the lower centers and
the higher centers of the brain, but also contains
important visual and auditory reflex centers, as well
as motor pathways that connect the cerebrum to the
cerebellum.
The diencephalon lies at the top of the brain stem,
under and between the cerebral hemispheres and
includes the thalamus, hypothalamus, optic tracts,
optic chiasma, infundibulum, Ventricle III,
mammillary bodies, posterior pituitary gland and the
pineal gland.
Hypothalamus - is the master
control of the autonomic system.
It maintains homeostasis by
regulating such things as:
1. Hunger and body weight
2. Water and electrolytes through
controlling thirst
3. Sleep and wakefulness
4. body temperature
5. blood pressure and heart rate
6. sexual response
7. secretion of hormones from
the pituitary gland.
Thalamus - serves as a central relay station for all
sensory information (except smell) that goes into and
comes out of the cerebral cortex. It plays a key role in
pain, touch, and temperature sensation, as well as in
attention, alertness and memory.
Thalamus
The corpus callosum
connects the left and
right cerebral
hemispheres and
facilitates
communication
between the
hemispheres. It is the
largest white matter
structure in the
brain, consisting of
200–250 million
myelinated axons.
Protection of the Central Nervous System
1. The brain and spinal cord are covered and protected
by the bones of the cranium and the vertebral column.
2. The brain has hollow fluid-filled cavities called
ventricles. A clear, colorless fluid called
cerebrospinal fluid flows within the ventricles and
around the brain and spinal cord to help cushion them
from injury.
3. The brain and spinal cord are covered and protected
by three layers of tough, connective tissue called
meninges. From the outermost layer inward they are:
the dura mater, arachnoid mater, and pia mater.
Cranial nerves
The brain communicates with
the body through the spinal cord
and twelve pairs of cranial
nerves. Ten of the twelve pairs
of cranial nerves that control
hearing, eye movement, facial
sensations, taste, swallowing
and movement of the face, neck,
shoulder and tongue muscles
originate in the brainstem. The
cranial nerves for smell and
vision originate in the cerebrum.
Cranial nerves
Number
I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Name
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
vestibulocochlear
glossopharyngeal
vagus
accessory
hypoglossal
Function
smell
Sight
moves eye, pupil
moves eye
face sensation
moves eye
moves face, salivate
hearing, balance
taste, swallow
heart rate, digestion
moves head
moves tongue