Transcript DIVISIONS OF THE NERVOUS SYSTEM

DIVISIONS OF THE NERVOUS SYSTEM
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Central Nervous System: Control center of the body
Consists of the brain and spinal cord
Function: To relay messages, process, compare, & analyze information.
Peripheral Nervous System
Consists of all the nerves and associated cells not part of the brain & spinal cord.
Including cranial and spinals nerves & ganglia (collection of nerve cell bodies)
CENTRAL NERVOUS SYSTEM
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Consists of the brain & spinal cord.
Brain is the main switching unit of the CNS; impulses originate here
Spinal cord links brain & rest of the body
The brain consists of:
35 billion neurons w/ a mass of 1.4 kilograms
meninges- 3 layers of connective tissue connecting one tissue to another
pia mater- innermost layer, covering and binding to the surface of the brain
fibrous w/ many blood vessels carrying food and OXYGEN to spinal cord
dura mater- outer most layer; thick connective tissue
arachnoid- thin, cobweblike layer between the two maters
cerebrospinal- between the pia mater & arachnoid, fluid-shock absorber
Spinal cord: 42-45 cm in length, protected by bone (vertebral column),
menings, and cerebrospinal fluid.
THE CEREBRUM
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The largest and most prominent part of the brain.
Controls all voluntary activities of the body.
Site of intelligence, learning, and judgment.
Corpus callosum- connects the right and left hemispheres together.
The many folds of the brain increase the S/A.
Lobes- Divisions of the hemispheres named for the bones they cover.
Each hemisphere controls the other side of the body.
Right shows creativity & artistic; Left shows analytical & mathematical
THE CEREBRAL CORTEX:
Outer surface of gray matter composed of densely packed nerve cells
Cerebral Medulla- Inner surface of white matter made of bundles of
myelinated axons.
CEREBELLUM & BRAINSTEM
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CEREBELLUM
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2nd largest part of the brain, located at the back of the skull.
Coordinates & balances the actions of the muscles
Damages causes muscles weakness & lack of coordination.
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THE BRAINSTEM
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Connects the brain to the spinal cord.
Medulla oblongata- controls involuntary actions; breathing, swallowing, etc
Contains cells of the reticular activating system; alerts & awakens brain
Pons- The link between the cerebral cortex & the cerebellum.
Midbrain- smallest division of the brainstem; controls hearing and vision.
THALAMUS & HYPOTHALAMUS
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Found between the brainstem and cerebrum.
Thalamus: Gray matter; switching station for sensory input.
Each sense, except smell, channels its nerves through the thalamus.
Hypothalamus: Below thalamus, controls hunger, thirst, fatigue, anger, &
body temperature.
FUNCTIONS OF THE BRAIN
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See fig. 37-16
Performed in the gray matter of the cerebral cortex.
Penfield’s experiments: brain senses no pain, so he could stimulate the brain w/
weak electrical signals while the patient was awake.
Not the whole story but; Sensory neurons synapse in spinal cord, neurons in
spinal cord relay to thalamus, then relays to sensory cortex.
BRAIN WAVES
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Brain Waves
If voltage electrodes are placed on the scalp there is a weak electrical signal
Electroencephalogram (EEG) gives general idea of the brain’s activity
Sleep: Cerebral cortex is at the lowest possible level in which a person is in a
state of unconsciousness & can be awakened by normal sensory stimulation.
MEMORY
Short term: Generally vanishes in a few days depending on its importance
Thought to be stored in the cerebral cortex
Long term: Permanent memories, may fade with time.
Could be stored in the total of the brain instead of just one region.
THE SPINAL CORD: Communication link between the brain and PNS
Regulates reflexes: the simplest response to a stimuli
Two types of tissues: central is gray matter & outer is white matter