The Brain

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The Brain

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

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The Brain
Cerebrum
Hypothalamus
Cerebellum
Pituitary gland
Medulla
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Areas of the brain

• The brain is composed of Cerebral Hemispheres,
  Cerebellum and Medulla

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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
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cerebellum

• Co-ordination of body movement, balance and
  posture

Cerebral Hemispheres
Cerebellum
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cerebrum/cerebral hemispheres

• 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.

Cerebral Hemispheres
Cerebellum
Medulla
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cerebrum/cerebral hemispheres

• 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

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Areas of the cerebrum
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The Areas can be split into 3 groups

• Sensory Areas
• Motor Areas
• Association Areas

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Motor
Association
Sensory
Sensory area for impulses from eyes
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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

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Mapping of the sensory motor areas to the body
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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.

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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.

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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 Brocas area

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Brocas Area
Brocas area
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Wernickes Area

• In 1967 Karl Wernicke noticed damage to another
  region of the cortex.
• Werniches area is connected to Brocas area by a
  bundle of nerve fibres.
• If this was damaged the patient can understand
  language but cannot repeat words.
• So Werniches area is concerned with
  understanding language. Brocas area is concerned
  with controlling the muscles that produce speech

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Wernickes Area
Wernickes area
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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

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Optic Chiasma
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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

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A close shave