4. The Brain Stem
Corpus
Callosum
Gyri
Sucli

5. The Brain Stem
• smallest and from an evolutionary viewpoint, the
oldest and most primitive part of the brain.
• continuous with the spinal cord, and is composed
of the parts of the hindbrain and midbrain.
• The medulla oblongata and pons control heart
rate, constriction of blood vessels, digestion,
swallowing, vomitting and respiration.
• The midbrain consists of connections between
the hindbrain and forebrain, & visual and
auditory reflexes. Mammals use this part of the
brain only for eye reflexes.

6. • The Reticular System, Arousal, and Sleep.
– The reticular activating system (RAS) of the reticular
formation.
• Regulates sleep
and arousal.
• Acts as a
sensory filter.

7. Cerebellum
Corpus
Callosum
Gyri
Sucli

8. Cerebellum
• 3rd part of the hindbrain, but it is not
considered part of the brain stem.
• Functions include fine motor coordination and
body movement, posture, and balance.
• This region of the brain is enlarged in birds
and controls muscle action needed for flight.

9. FOREBRAIN
Corpus
Callosum
Divided into 2
Gyri general regions:
Sucli
•Diencephalon
•Cerebrum

10. Diencephalon
• The thalamus and hypothalamus are the parts
of the diencephalon.
• The thalamus acts as a switching center for
nerve messages.
• The hypothalamus is a major homeostatic
center having both nervous and endocrine
functions for control of hormones.

11. • largest part of the human brain, is divided
into left and right hemispheres connected
to each other by the corpus callosum.
• hemispheres are covered by a thin layer of
Cerebrum gray matter known as the cerebral cortex,
the most recently evolved region of the
vertebrate brain.
• Fish have no cerebral cortex, amphibians
and reptiles have only rudiments of this
area.
The cortex in each hemisphere of
• the cerebrum is between 1 and 4
mm thick. Folds divide the cortex
into four lobes: occipital,
temporal, parietal, and frontal.
No region of the brain functions
alone, although major functions
of various parts of the lobes have
been determined.

13. Sensory Regions of the Cerebrum
Frontal Lobe Parietal Lobe
•Speech •Speech
•Emotions •Somatosensory Areas & taste
•Motor control •Reading
Temporal Lobe Occipital Lobe
•Smell •vision
•hearing

14. Motor Cortex Map
•Developed by Dr.
William Penfield
(Canadian from McGill Univ.)
•Maps motor (or
sensory areas) on the
cerebral cortex of each
hemisphere of the
brain.
•Each hemisphere of
the brain controls the
opposite sides of the
body.

16. HOMUNCULUS MODELS
•Homunculus models are sculptures of the human body
•each body part is shown in proportion to the amount of brain
area dedicated to its motor control or sensory control

17. What does the homunculus tell us?
1. The human brain is ‘heavy handed’.
– WHY?
2. Mouth parts are also very important.
– WHY?
What about other animals?
Platypus

18. Brain Comparisons
EQ
Brain to Body
size Ratio
Development
of Cerebral
Cortex
Endocasts