Download The CNS - Mr. Lesiuk

The Central Nervous System
The central nervous system (CNS) consists of the spinal cord
and brain.
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Organization of the Nervous System
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Both are protected by bone, wrapped in protective membranes called
meninges, and surrounded and cushioned with cerebrospinal fluid that
is produced in the ventricles of the brain.
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The ventricles are interconnecting cavities that produce and serve as a
reservoir for cerebrospinal fluid.
The CNS receives and integrates sensory input and formulates motor
output.
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Gray matter contains cell bodies and short, nonmyelinated fibers; white matter
contains myelinated axons that run in tracts.
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The Spinal Cord
The spinal cord extends from the base of the brain through the vertebral
canal.
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Structure of the Spinal Cord
A central canal holds cerebrospinal fluid.
Gray matter of the spinal cord forms an “H” and contains interneurons and
portions of sensory and motor neurons.
White matter consists of ascending tracts (dorsally) taking sensory information to
the brain and descending tracts (ventrally) carrying motor information from the
brain. Tracts cross just before entering the brain. So left right.
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THIS ANATOMY
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Functions of the Spinal Cord
The spinal cord is the center for many reflex arcs.
It also sends sensory information to the brain and receives motor output
from the brain, extending communication from the brain to the
peripheral nerves for both control of voluntary skeletal muscles and
involuntary internal organs.
Severing the spinal cord produces paralysis.
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The Brain
The brain has four cavities called ventricles.
The cerebrum has two lateral ventricles, the diencephalon has the third
ventricle, and the brain stem and cerebellum have the fourth ventricle.
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The Cerebrum
The cerebrum or telencephalon has two cerebral hemispheres connected
by the corpus callosum.
.
SEE THE
“C”
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Cerebral Lobes
Learning, memory, language and speech take place in the cerebrum.
Sulci divide each hemisphere into lobes including the frontal, parietal, occipital,
and temporal lobes
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- Frontal
- Parietal
- Temporal
- Occipital
- Cerebellum
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- Brain Stem
The Cerebral Cortex
The cerebral cortex is a thin, highly convoluted outer layer of gray matter
covering both hemispheres.
The primary motor area is in the frontal lobe; this commands skeletal muscle.
The primary somatosensory area is dorsal to the central sulcus or groove.
The primary visual area is at the back occipital lobe.
The temporal lobe has the primary auditory area.
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Language and Speech
Language and speech are dependent upon Broca’s area (a motor speech
area) and Wernicke’s area (a sensory speech area) that are involved in
communication.
These two areas are located only in the left hemisphere; the left
hemisphere functions in language in general and not just in speech.
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The Diencephalon (Two in the Head)
The hypothalamus and thalamus are in the diencephalon that encircles
the third ventricle.
The hypothalamus controls homeostasis and the pituitary gland, and the
thalamus receives all sensory input except smell and integrates it and
sends it to the cerebrum.
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The Cerebellum – “little brain”
The cerebellum receives sensory input from eyes, ears, joints and
muscles and receives motor input from the cerebral cortex.
It integrates this information to maintain posture, coordination and
balance.
The cerebellum is involved in learning of new motor skills, such as
playing the piano or hitting a golf ball.
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The Brain Stem
The brain stem contains the medulla oblongata, pons, and midbrain.
The medulla oblongata and pons have centers for vital functions such as
breathing, heartbeat, and vasoconstriction.
The medulla also coordinates swallowing and some other automatic
reactions (many reflex centers for heartbeat, breathing and BP)
The midbrain acts as a relay station between the cerebrum and spinal
cord or cerebellum.
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The Reticular Formation
The reticular formation is a complex network of nuclei and fibers that
extend the length of the brain stem.
One portion of the reticular formation, called the reticular activating
system, arouses the cerebrum via the thalamus causing alertness.
It is believed to act as a filter for incoming sensory impulses.
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