Brain pres

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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.

cere

brum



The outer 4 mm surface of the cerebrum is called the

cerebral cor tex . 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

medul la 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

medul la oblongata



The medul la oblongata lies between the pons and the

spinal cord . It contains centers which control key,

autonomic body functions and it relays nerve signal s

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 ref lex 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 thirst3. Sleep and wakefulness

4. body temperature

5. blood pressure and heart rate6. 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 cerebralhemispheres and

facilitates

communicationbetween the

hemispheres. It is the

largest white matter

structure in the

brain, consisting of

200 – 250 million

myelinated axons.



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 .

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.

1. The brain and spinal cord are covered and protected

by the bones of the cranium and the vertebral column.

Protection of the Central Nervous System



Cranial nerves

The brain communicates with

the body through the spinal cordand 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 musclesoriginate in the brainstem. The

cranial nerves for smell and

vision originate in the cerebrum.



Cranial nervesNumber Name Function

I olfactory smellII optic Sight

III oculomotor moves eye, pupil

IV trochlear moves eye

V trigeminal face sensationVI abducens moves eye

VII facial moves face, salivate

VIII vestibulocochlear hearing, balance

IX glossopharyngeal taste, swallowX vagus heart rate, digestion

XI accessory moves head

XII hypoglossal moves tongue

Brain pres

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