The Brain

The human brain is the site of the major coordination in the nervous system.

The BrainThe Brain

Cerebrum

Cerebellum

Medulla

Pituitary gland

Hypothalamus

Areas of the brain The brain is composed of Cerebral

Hemispheres, Cerebellum and MedullaMedulla

Cerebral Hemispheres

Cerebellum

medulla Controls autonomic activities including heart rate, and

ventilation rate Impulse transmitted from medulla via sympathetic or

parasympathetic branch of automatic nervous system

Medulla

Cerebral Hemispheres

Cerebellum

cerebellum Co-ordination of body movement,

balance and posture

Cerebral Hemispheres

Cerebellum

Highly Folded and so has a large SA. Patients with injuries to specific parts

of the brain can be studied to see how their functions are altered.

cerebrum/cerebral hemispheres

Medulla

Cerebral Hemispheres

Cerebellum

Different parts of the brain can be stimulated electrically to see which muscles in the body respond

Conversely different parts of the body can be stimulated to see which parts of the brain show electrical activity.

More recently MRI (magnetic resonance imaging) has been used in brain study

cerebrum/cerebral hemispheres

Areas of the cerebrum

Visual sensory area

Visual associationarea

Proprioception sensory area

Mainmotorarea

Mainsensoryarea

Complex movementmotor area

Higher functionsassociation area

Speechassociationarea

Smellsensoryarea Auditory

sensoryarea

Visual andauditoryassociationarea

Comprehensionassociationarea

Sensoryareas

Associationareas

Motorareas

The Areas can be split into 3 groups Sensory Areas

Motor Areas

Association Areas

Association Motor

Sensory

Sensory area for impulses from eyes

cerebrum/cerebral hemispheres

•Sensory areas of the cerebral hemispheres receive impulses from sense organs and transmit them to the association areas

•The association areas of the cerebral hemispheres receive impulses - interpret them in the light of similar past experiences and transmit impulses to motor areas

•The motor areas transmit impulses to the effectors

•The size of the sensory and motor areas is related to the number of receptors in that area

•The left and right cerebral hemispheres control the opposite sides of the body

Mapping of the sensory & motor areas to the body

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lde

r

legs

toes

ankle

MotorCortex

shou

lder

toes

genita lia

foot

SensoryCortex

Sensory & Motor Maps

The maps show that regions of the body with many sensory (or motor) neurones have corresponding large areas of the cerebrum linked to them.

So for example the lips occupy a larger region of the sensory cortex than the shoulder, because there are more sensory neurones in the lips.

Association Areas Are used to compare sensory input with

previous experiences, and make decisions These areas are involved in speech,

understanding and memory retrieval The frontal lobes are large in humans and it

is thought that they responsible for higher functions like abstract thought, personality & emotion.

Speech The left side of the brain Patients with speech problems gave 1st clues

about how the brain controls language 1981 Dr Paul Broca described a patient who

could only say the word “tan”. When the patient died Broca examined the

brain and found damage to the left cerebral hemisphere

This part of the brain is now know as Broca’s area

Broca’s Area

Broca’s area

Wernicke’s Area In 1967 Karl Wernicke noticed damage to

another region of the cortex. Werniche’s area is connected to Broca’s area

by a bundle of nerve fibres. If this was damaged the patient can

understand language but cannot repeat words. So Werniche’s area is concerned with

understanding language. Broca’s area is concerned with controlling the muscles that produce speech

Wernicke’s Area

Wernicke’s area

Visual Processing

The visual sensory area is at the back of the brain & receives sensory input from the optic nerves

The 2 hemispheres see slightly different images from the opposite of the visual field, and differences can be used to judge distance

Optic Chiasma

Summary Sensory areas – receive input from

receptors Motor areas – Origin of impulses which

bring about voluntary movements These receive/transmit impulses from

the opposite side of the body Association areas – interpret sensory

information in the light of experience

A close shave