Chapter 15: The Brain!

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Chapter 15 The Brain!

• Lesson Objectives
• To describe the gross structure of the brain and
  the functions of the cerebrum, cerebellum,
  medulla oblongata and hypothalamus

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Brain teasers what do you see?
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Stare at the dot for a few seconds, then move
your head closer to it!
http//www.pennmedicine.org/encyclopedia/em_Displa
yAnimation.aspx?gcid000016ptid17
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What does the brain ideally look like?
Of course, really the brain is dynamic and
individually variable
http//www.pbs.org/wnet/brain/3d/index.html -
information on Brain Anatomy!
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Brain structure
Cerebrum (left and right cerebral hemispheres)
linked by corpus callosum
The brain is an expanded extension of the spinal
cord It contains ventricles containing
CEREBRO-SPINAL FLUID (continuous with the spinal
cord) Consists of myelinated (white areas) and
unmyelinated (grey areas) neurones
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Brain structure annotate!
Ventricle containing cerebro-spinal fluid
(secreted by the meninges)
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Right versus left Cerebrum
Verbal
Non-verbal
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The cerebrum highly folded area
Parietal lobe
Sensory area
Motor area
Frontal lobe
Contains an area involved with planning actions
and movements
Occipital lobe
Corpus callosum links the two cerebral
hemispheres
A large association area in the parietal and
occipital lobes is involved in determining body
position
NOT SHOWN Temporal lobe!
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The cerebrum highly folded area
NOT SHOWN Amygdala (almonds) - coordinates
the action of the autonomic and endocrine systems
as well as a role in emotions Hippocampus
(seahorse) role in memory (making new
memories)
Limbic system (part of) emotions and memory
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Studying the brain BRAIN SCANS
CAT scan (computer assisted tomography) Uses
X-rays to find out about the tissues in the
brain Put many slices of the brain together to
create a 3D image!
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Studying the brain BRAIN SCANS
CAT scan (computer assisted tomography)
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Studying the brain BRAIN SCANS

• PET Scan (positive emission tomography)
• Inject radioactive material (labelled
  2-deoxyglucose)
• Respiring cells take this up and use it in
  glycolysis (phosphorylate it)
• It cannot be metabolised further or removed from
  the cell
• Scan to detect the decay of the material
  (half-life)

More metabolically active regions of the brain
take up more 2-deoxyglucose. Give patient
injection and then give them a stimulation or get
them to think about something
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Studying the brain BRAIN SCANS
PET Scans
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Studying the brain BRAIN SCANS
MRI (magnetic resonance imaging) Used to find
out which parts of the brain are active at
different times Computer-controlled equipment
measures the magnetic field from Haemoglobin in
different regions of the brain Oxyhaemoglobin
has a smaller magnetic effect than
deoxyhaemoglobin Areas with high activity have a
greater level of oxyhaemoglobin
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Two association areas in the left hemisphere -
language
Brocas aphasia http//www.youtube.com/watch?vgo
cIUW3E-go Wernickes aphasia http//www.youtube
.com/watch?vaVhYN7NTIKU
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The Cerebellum
Cerebellum folded surface Controls movement and
posture responsible for balance, coordination,
eye movement and fine manipulation Receives
impulses from ears, eyes, stretch receptors in
muscles and other parts of the brain Integrates
information and uses it to coordinate skeletal
muscle contraction
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The Brain Stem
Mesencephalon (midbrain)
Medulla oblongata Links the brain and spinal
cord Coordinates and controls involuntary
movements (breathing, heartbeat etc.)
Pons conducts signals from the cerebrum to the
cerebellum and medulla as well as sensory signals
to the thalamus
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Diencephalon - the interbrain

• Hypothalamus
• Links the nervous system to the endocrine system
  via the pituitary
• Size of an almond in humans!
• Controls body temperature, hunger, thirst,
  fatigue, anger and circadian cycles (autonomic
  nervous system)

• Thalamus (left and right)
• Believed to process and relay sensory info.
  selectively to cerebral cortex
• The links with the cortex may be linked with
  consciousness
• Regulates sleep and wakefulness (damage leads to
  a coma!)

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Studying the brain
Frontal lobe damage Phineas Gage (1823-1860)
was a railroad construction foreman An 1848
explosion forced a steel tamping rod through his
head Others said he was no longer Gage
3.2 cm diameter rod! Went through his head from
bottom to top and landed approx. 30 metres behind
him!