Nervous System—Anatomy of the Brain
Lecture 7
Today we’re going to talk about the brain. We’re going to begin what is
one of the largest series of lectures in this whole course devoted to the
study of the nervous system. Now, the brain is where most of us believe
that it all happens; it’s one of the most complex organs in the body,
probably one of the least fully understood.
I
n this, the rst of seven
lectures on the nervous
system, we start by
examining the brain:
its principal components
(the outer coverings, the
cerebrospinal uid, and the
blood vessels) and its main
anatomical divisions (the
brain stem, the cerebellum,
the diencephalon, and
© iStockphoto/Thinkstock.
the cerebrum). Next, we
examine the divisions
of the cerebrum (two
hemispheres, each with
four lobes) and the The largest part of the human brain is the
cerebrum, which divided into two hemispheres
functional areas of the (left and right) and four lobes.
cerebral cortex.
The brain is among the largest organs in the body, weighing about 3 pounds
and containing more than 100 billion cells. It constitutes just 2% of the
body’s weight but consumes 20% of the body’s blood supply. Virtually all
of the activities of the rest of the body are devoted to the care and protection
of the brain. The brain is covered and protected by a rigid, bony case—the
skull. The skull is composed of two layers of bone with air spaces between
them. This makes the skull lighter and more protective than solid bone.
37
, Principal components of the brain
The meninges are the coverings of the brain.
The dura mater (“hard mother”) is the outer and toughest covering.
It also separates most of the two halves of the brain.
The arachnoid (“spiderlike”) is the middle layer. It circulates
cerebrospinal uid and blood.
The pia mater (“delicate mother”) is the innermost covering. It
adheres to the brain.
The arachnoid villae secrete cerebrospinal uid (CSF) in the brain’s
sinus (open spaces). CSF covers the brain and spinal cord.
CSF is produced by the choroid plexuses, located in the walls of the
ventricles. It is reabsorbed through the arachnoid villae in the dural
venous sinuses. It has the following functions:
Lecture 7: Nervous System—Anatomy of the Brain
It provides mechanical protection for the brain and spinal cord,
and it provides buoyancy.
It provides chemical protection: It is the optimal environment
for neuron function.
It circulates nutrients to parts of the brain, and it is an exchange
area for wastes.
The brain requires a slightly different operating environment than the body.
The blood-brain barrier separates the two systems.
38
Lecture 7
Today we’re going to talk about the brain. We’re going to begin what is
one of the largest series of lectures in this whole course devoted to the
study of the nervous system. Now, the brain is where most of us believe
that it all happens; it’s one of the most complex organs in the body,
probably one of the least fully understood.
I
n this, the rst of seven
lectures on the nervous
system, we start by
examining the brain:
its principal components
(the outer coverings, the
cerebrospinal uid, and the
blood vessels) and its main
anatomical divisions (the
brain stem, the cerebellum,
the diencephalon, and
© iStockphoto/Thinkstock.
the cerebrum). Next, we
examine the divisions
of the cerebrum (two
hemispheres, each with
four lobes) and the The largest part of the human brain is the
cerebrum, which divided into two hemispheres
functional areas of the (left and right) and four lobes.
cerebral cortex.
The brain is among the largest organs in the body, weighing about 3 pounds
and containing more than 100 billion cells. It constitutes just 2% of the
body’s weight but consumes 20% of the body’s blood supply. Virtually all
of the activities of the rest of the body are devoted to the care and protection
of the brain. The brain is covered and protected by a rigid, bony case—the
skull. The skull is composed of two layers of bone with air spaces between
them. This makes the skull lighter and more protective than solid bone.
37
, Principal components of the brain
The meninges are the coverings of the brain.
The dura mater (“hard mother”) is the outer and toughest covering.
It also separates most of the two halves of the brain.
The arachnoid (“spiderlike”) is the middle layer. It circulates
cerebrospinal uid and blood.
The pia mater (“delicate mother”) is the innermost covering. It
adheres to the brain.
The arachnoid villae secrete cerebrospinal uid (CSF) in the brain’s
sinus (open spaces). CSF covers the brain and spinal cord.
CSF is produced by the choroid plexuses, located in the walls of the
ventricles. It is reabsorbed through the arachnoid villae in the dural
venous sinuses. It has the following functions:
Lecture 7: Nervous System—Anatomy of the Brain
It provides mechanical protection for the brain and spinal cord,
and it provides buoyancy.
It provides chemical protection: It is the optimal environment
for neuron function.
It circulates nutrients to parts of the brain, and it is an exchange
area for wastes.
The brain requires a slightly different operating environment than the body.
The blood-brain barrier separates the two systems.
38
