Download The Central Nervous System

`Title: The Central Nervous System
Introduction: The central nervous system consists of the brain and the spinal cord.
The brain is the control center for your thoughts, emotions, creativity, wisdom,
memories, and all the activities and behaviors that make you who you are. Made up
of about 100 billion neurons and 10–50 trillion neuroglia, the adult brain has a mass
of only about 1300 g (almost 3 lb).
Humans have realized the importance of the brain for thousands of years. The
Egyptians are given credit for the first anatomic descriptions of the brain, which
date back as far as 3000 B.C. Egyptian records describe paralysis, loss of cognitive
function, and personality changes associated with skull fracture and brain damage.
As far back as the fifth century B.C., the Greek physician Hippocrates realized the
importance of the brain in mediating personality, emotion, and thought. Some South
American cultures were even known to perform a primitive form of brain surgery
known as trepanation, in which a hole was drilled into the skull with bronze surgical
tools. Although our understanding of the human brain has improved dramatically
since ancient times, especially over the last 150 years, we have only begun to
scratch the surface.
The spinal cord mediates some of your most rapid reactions to environmental
changes. If you pick up something hot, you may drop the object even before the
sensation of extreme heat or pain reaches your conscious perception. The spinal
cord is the pathway for sensory nerve impulses traveling to the brain and motor
nerve impulses traveling from the brain toward skeletal muscles and other effectors.
1- Major Parts of the CNS – The brain consists of four (4) major parts:
The cerebrum, the diencephalon, the brainstem and the
cerebellum
a- The cerebrum
1-
2- Amygdala
3- Hemispheric lateralization –
4- Major areas and lobe control
a- Broca’s area –
b- Wernicke’s area
c- Lobes
Parietal
Temporal
Occipital
Frontal
d- Differences between men and woman -
b- The diencephalon
1- Pineal gland
2- Thalamus
3- Hypothalamus
c- The brainstem
d- The cerebellum is found posterior to the brainstem
d- The Central Nervous System is protected by two types of
connective tissue (CT): the bony skull and the vertebrae
and the cranial and spinal meninges. In addition the
cerebral spinal fluid (CSF) which is produced by the brain
surrounds and cushions the brain and spinal cord
e- The meninges – the meninges are three connective tissue
coverings the envelope the brain and spinal cord
a- The dura mater – the most superficial and strongest of the connective
tissues is the dura. The dura separates the two hemispheres of the
cerebrum. It separates the hemispheres of the cerebellum and separates
the cerebrum from the cerebellum
b- Arachnoid
c- The Pia
d- Denticulate ligament – (small teeth) suspends the spinal cord in the
middle of the membrane sheaths and protects the spinal cord against
sudden displacement
e- Superior sagittal sinus
f- Blood flow to the brain and spinal cord
a- Blood supplies oxygen and nutrients to the central nervous system
b- Blood
c- Blood
d- In adults the brain constitutes about 2% of the body weight but consumes
20% of the oxygen and glucose
e- Neurons make ATP from glucose in the brain
f- When specific neurons are activated there is an increase in blood flow to
that portion of the brain
g-
h- No glucose is stored in the brain. Therefore, a continuous supply is
needed. It blood has a low glucose level (hypoglycemia) mental confusion,
dizziness and loss of consciousness may occur
i- Cerebral vascular accidents
g- Blood-Brain Barrier (BBB) The blood brain barrier protects
the brain from harmful substances and pathogens by
preventing passage of these substances from the blood into
the fluid of the brain tissue (cerebral spinal fluid)
a- Glucose is able to pass the BBB by active transport (requires energy,
glucose is always passing into the blood, hence the concentration is high)
b- Proteins and antibodies do not pass through the barrier – therefore
infections in the brain can be very difficult to treat, i.e., meningitis
c- Carbon dioxide, oxygen and alcohol pass through the membrane freely,
this is why fetal alcohol syndrome can be so serious
d- Inflammation (meningitis) can break down the barrier and cause damage
to the brain
e- Other immunocompetant areas in the body exist, i.e., the blood-placenta
barrier and the blood-testes barrier