The Brain and it's Diseases
Comparing Animal Brains:
In general, larger animals tend to have larger brains.
However, larger brains do not always equate to intelligence
and thinking ability. If
the ratio of body weight to brain weight were considered, the squirrel
monkey’s brain is larger
than a human brain. The
squirrel monkey, a small South American monkey,
may be clever, but it is not a great thinker.
Intelligence and cognitive ability are functions of density,
number of neurons and surface area of the brain. The size of various
areas of the brain is also important. The neocortex, is the area of the brain which controls social
relationships, and reasoning. It makes up 16 percent of the brain in
insect-eaters and 80 percent in humans.
Human
Brain Anatomy:
The brain
weighs about 3 pounds and has three main parts: the cerebrum, the
cerebellum and the brain stem. When removed
from the skull, the human brain is as
soft as Jello. For preservation, brains are treated with chemicals
such as formaldehyde. These were carefully dissected and encased in
plastic blocks. The brains not encased in plastic blocks were
hardened with liquid plastic in a process called plastination.
These brains
have been collected from autopsies performed by the Department of
Pathology and Laboratory Medicine at the University of Tennessee
Health Science Center and from cadavers donated to the Department of
Anatomy, University of Tennessee at Knoxville and UTHSC.
Horizontal
Section of a Human Brain:
The dark area in the brain stem, marked by an arrow, is called
substantia nigra. Many of the cells in this area would be lost in
patients with Parkinson
’s disease.
Brain
Diseases Awareness and Prevention:
The brain is
surrounded by three protective coverings known as the meninges. These are—the pia
mater, the arachnoid layer and the dura mater. The pia mater adheres
to the brain; the dura mater lines the inside of the skull and the
arachnoid layer lies in between the pia and dura mater.
Head injuries may cause bleeding between these layers. The
use of automobile seat belts and bicycle helmets can reduce many of
these injuries. Increased blood pressure may cause hemorrhage deep
inside the brain.
Meningitis: Infection of the meninges is known as meningitis.
Vaccines may prevent meningitis.
Infection of
the meninges by bacteria, viruses, or fungi causes meningitis
resulting in high fever, headache, and stiff neck. The specimen
illustrates the thickened and opaque meninges, characteristic of
bacterial meningitis.
Subdural
Hemorrhage or Hematoma:
Injuries to the head often result in bleeding under the membranes
covering the brain. Bleeding under the dura mater is called subdural
hemorrhage or hematoma. Wearing a seat belt can help reduce the
impact on the brain during an automobile accident. In this specimen
a subdural hematoma is marked by an arrow.
Cerebral
Hemorrhage: The dark clot
on the left side of this specimen is a “cerebral hemorrhage,”
a bleed in the substance of the brain. Hypertension (high blood
pressure) can cause this type of hemorrhage, which the patient
expresses as a stroke. Check your blood pressure regularly and
consult a physician if it is increased.
Cancer:
Cancer from many organs can spread to the brain.
This specimen shows spread of lung cancer to the brain. The
arrows show the cancer tissue. Smoking is one of the main causes of
lung cancer.
Nigra
