Brain
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One of the largest organs in the adult
body—3 pounds (1400 g)
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Almost 100 billion neurons and as many
glia
Most new neurons are produced before
and shortly after birth
Synapses are made and broken
throughout life
Neurons do NOT undergo mitosis
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Brain
• 4 major portions
• Cerebrum-- Largest part of brain in humans
– Higher mental function, memory, personality
• Diencephalon- processes sensory info- mostly
gray matter- controls emotional experiences (in
limbic system)
• Cerebellum-Balance and coordination,
coordinates voluntary muscle movements
• Brain Stem- Controls visceral functions
(autonomic)
Brainstem
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Mostly white matter
Visceral, autonomic functions
“Reptilian”
3 parts:
–Medulla oblongata
–Pons
–Midbrain
Brainstem: medulla oblongata
- Lowest part of the brainstem
- Continuation of spinal cord,
above foramen magnum
- Mostly white matter
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Brainstem: medulla oblongata
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Functions:
 -Reflexes
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heart rate, dilation of blood
vessels, breathing rate
-Other
reflexes: vomiting, coughing,
sneezing, blinking, etc
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Brainstem: Pons
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Pons
 -Located above the medulla and below the
midbrain
 -Contains reflexes to regulate respiration
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Brainstem: Midbrain
-Located above the pons and below the
cerebrum; forms the midsection of the
brain
 -some cranial nerve reflexes like pupil
dilation & eye movement
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Cerebellum
Structure
 Second largest part of the brain—contains
most neurons most computing power
 Located below cerebrum; transverse fissure
separates these two
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Cerebellum: function
• Functions: shares with cerebrum
– Helps control posture and balance
– Coordinates motor commands from cerebrum
with sensory info coming from muscles makes
muscle movement “smooth” and “coordinated”
Diencephalon
“between brain” near 3rd ventricle
A. Thalamus
• main relay station for sensory impulses on way to
cerebrum
• recognition of touch, temperature
• makes associations between sensory impulses and
pleasantness or not
Diencephalon
B. Hypothalamus- regulates & coordinates autonomic activities,
helps control responses made by visceral effectors, link between
“psyche” and soma (mind’s influence over body and how you
feel), hunger, sleep
Diencephalon
C. Pineal gland: Biological clock, releases melatonin into blood
- Melatonin: “sleep hormone”
- subtle changes in sunlight and lunar light cause
shifts to melatonin cycle
- jet lag?
- night shift?
Diencephalon
• D. Optic chiasma: region where right and left optic nerves
cross each other before entering the brain
Cerebrum
• Cerebrum: Largest part of brain in humans
– 2 halves= cerebral hemispheres
– Higher mental function
– Somatic senses and “special” senses
– Motor control
– Consciousness, language
• Cerebral cortex- outermost layer; gray matter
Cerebral fissures
• Longitudinal fissure: divides cerebrum into L
and R hemisphere
Cerebral fissures
• Central sulcus: groove between frontal and
parietal lobes
Cerebral fissures
• Lateral fissure: deep groove between
temporal lobe and frontal/parietal lobes
Cerebral fissures
• Parietooccipital sulcus: groove between
occipital and parietal lobes
Lobes of Cerebrum
Frontal Lobe: reasoning, thinking, attention,
language (higher cognitive functions)
–Broca’s area makes speech possible
–Primary motor cortex coordinates and initiates
motor movements
Lobes of Cerebrum
• Parietal Lobe: Integrates sensory info: touch,
pain, temperature, relation of body parts
– Visual processing
– Spatial mapping
– Number representation
Lobes of Cerebrum
• Temporal Lobe: hearing, perception, face
recognition
• Wernicke’s area: at intersection of temporal,
occipital, and parietal on LEFT SIDE of brain;
Helps you recognize and understand language
Patient with stroke in Left posterior
temporal lobe
• Boy, I'm sweating, I'm awful nervous, you know, once in a
while I get caught up, I can't get caught up, I can't
mention the tarripoi, a month ago, quite a little, I've
done a lot well, I impose a lot, while, on the other hand,
you know what I mean, I have to run around, look it over,
trebbin and all that sort of stuff. Oh sure, go ahead, any
old think you want. If I could I would. Oh, I'm taking the
word the wrong way to say, all of the barbers here
whenever they stop you it's going around and around, if
you know what I mean, that is tying and tying for
repucer, repuceration, well, we were trying the best that
we could while another time it was with the beds over
there the same thing…
• “I certainly have seen individuals with
Wernicke's aphasia carry on very well in their
lives, for example taking buses to their
appointments, caring for their children, and
even driving. Thus, they clearly 'think'. How
much of this is verbally-mediated thought
though is unclear.”
Lobes of Cerebrum
• Occipital Lobe: vision: color, orientation,
motion
– Must project to other lobes
– Vision projects to temporal lobe to recognize
identity of object