Communication
Topic 15: The Mammalian Brain
Biology in Focus, HSC Course
Glenda Childrawi, Margaret Robson and Stephanie Hollis
DOT Point(s)
 identify those areas of the cerebrum involved in the perception
and interpretation of light and sound
 perform a first-hand investigation to examine an appropriate
mammalian brain or model of a human brain to gather
information to distinguish the cerebrum, cerebellum and
medulla oblongata and locate the regions involved in speech,
sight and sound perception
Introduction
The brains of humans appear to
be out of proportion compared
with overall body size. This is
due to the great entanglement
of the cerebrum. The cerebrum
splits into two hemispheres, a
left and a right. Each
hemisphere receives impulses
from and exerts control over
the opposite side of the body.
otroblogpelotudo.blogspot.com
The Cerebrum
The hemispheres are divided into four lobes:
1. Frontal
2. Occipital
3. Parietal
4. Temporal
Cerebellum
best-diving.org
The Cerebrum
 Under a tough protective covering (dura matter), the surface of
the cerebrum is drawn up into folds called convolutions. This
triples the surface area of the brain where important processes
occur.
www.allposters.com -
The Cerebrum
Most of the activities of the cerebrum
occur on its outer surface, in a layer of
grey matter (cerebral cortex) only a
few millimetres thick.
Those activities fit three general
categories:
1. Motor (movement)
2. Sensory (senses)
3. Associative (higher mental
activities such as reasoning and
logic. This takes up about 95% of
the cerebral cortex)
best-diving.org
The Cerebrum
The greater the surface area of the cerebrum the greater the
ability to perform functions.
best-diving.org
Light
 Optic nerves are the sensory nerves of vision.
Fibres arise from the retina of the eye to form the optic nerve.
Each optic nerve passes through the skull via an opening in the
eye socket. The optic nerves from each eye cross over partly to
form the optic chiasma (cross).
medical-dictionary.thefreedictionary.com
Light
About half of the nerves cross
to the other side, providing
each visual cortex with the
same image as viewed by both
eyes but each eye received the
image at a slightly different
angle.
www.ocutech.com
Light
 A visual cortex lies within the
occipital lobe of each cerebral
hemisphere. Impulses reach
this lobe from the retina via
the optic nerve.
Different sites on the visual
cortex process information
from different positions on the
retina.
drugline.org
Sound
 Auditory nerves arise from the hearing (cochlea) and
equilibrium (vestibule) within the inner ear. The two divisions
merge to form one nerve now known as the vestibulochochlear
nerve. This nerve runs from the organ of Corti to the auditory
cortex, in the temporal lobe of the brain.
hydrogen.physik.uni-wuppertal.de
Sound
An auditory cortex is found on
the temporal lobe of each
cerebral hemisphere. Different
sites on this cortex receive and
interpret different sound
frequencies.
scienceblogs.com
PRAC
-Sheep Brain Dissection