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The Nervous System
Images with permission of Eric Chudler <[email protected]>
Check out his site it is awesome!
Nerve tissues respond to stimuli and are
composed of individual cells called
neurons and their associated support
cells.
Nerve cells can measure up to two
meters in length and are well suited to
transmitting messages. These cells
convert stimuli into electrochemical
impulses and transmit the signals down
their lengths.
Neuron Structure
•Sensory neurons from receptor cells,
receive a stimulus
•Motor neurons from effector cells,
respond to a stimulus.
•Interneurons are between sensory and
motorneurons.
The Action Potential is an all or none
response, there is an AP or not!
Web site explanation.
The Action Potential moves down the
neuron from dendrite to axon then to the
end brush or presynaptic terminal.
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The Action Potential explanation!
A
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Transmitters
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one
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message.
The transmission of nerve impulses can be
altered by various substances. Stimulants
like caffeine can increase the amount of
transmitters released across the synapse.
Brain and Spinal Cord
Brain and Spinal Cord Protection
There are 3 membranes protecting the
brain and spinal cord - meninges. The
spaces between the membranes are filled
with cerebrospinal fluid. The fluid
cushions the brain and spinal cord agains
shock and removes wastes to the blood.
Stroke!
• A stroke occurs when the blood
supply to the brain is cut off by a
broken or blocked blood vessel.
• Damage to the tissue of the area
effected results from lack of fresh
oxygenated blood.
• Damage to the right side of the brain
effects the left side of the body!
Spinal Cord Damage
• Damage to the cord results in
loss of ability to use body parts
below the injury.
• Little or no sensation occurs in
effected body parts.
Medical Technology
• EEG - uses electrical impulses produced
by the brain to show brain activity
• CAT scan - produces a 3-D image using X
- rays and a computer. This can be used to
reveal disorders like tumors, broken blood
vessels and other brain problems (reduces
the need to open up people's heads!)
Medical Technology
• MRI - This machine uses
magnetic fields to excite
hydrogen atoms inside
your body. Since tumors
are different than your
body tissues they show
up on the MRI image
(they are denser). These
images are also in 3-D.
Alzheimer’s
• An illness that shows up in the elderly
portions of out population.
• Complications include loss of nerve cells
from cerebral cortex, neurofibrilar
tangles, neuritic plaques and changes in
enzyme systems in the synapse.
• This results in low levels of transmitters
and fewer neurons to transmit messages
Epilepsy
• A type of Brain disease that can result in
sudden loss of conciousness.
• Caused by non-functioning cells in the
brain that can lead to seizures.
• Usually the seizures are triggered by
something and a warning message such as
a smell precedes the event.
• Do not place an object in the mouth of the
victim.
• Peripheral Nervous System - all neurons
lying outside that brain and spinal cord.
It includes that 12 cranial nerves and 31
pairs of spinal nerves. Cranial nerves are
important for the face and senses while
the spinal nerves are useful in reflexes
and somatic control.
Somatic Nervous System
• This system is under conscious
control through motor neurons
connected to your skeletal muscle.
• Through the use of this system you
can control all voluntary actions.
Autonomic Nervous System
• This system is NOT under conscious
control and involves nerves that connect
to glands, smooth muscle and cardiac
muscle. This system has two major
components, one that stimulates the body
"sympathetic" and one that slows the
body down, "parasympathetic". The
ganglia for these systems are located next
to the spinal cord.