Transcript NERVOUS SYSTEM – Forero, Barrera, Leyton

BY
•Sebastian Leyton
•Valentina Forero
•Daniel Barrera
Every time you have an internal or external change
that causes a response is called a stimulus. Every
day you experience thousands of stimuli. Noise,
light and smell of substances are examples of
stimuli outside your body. Chemical substances
like hormones are stimuli inside your body.
Control systems maintain homeostasis. Your
nervous system is one of the control systems
in your body
Nerve cells or neurons are the basic functioning units in the nervous
system. There are three types of neurons; Sensory , motor and
interneuron's. Sensory neurons receive information and send
impulses to the brain and spinal cord, here interneuron's relay
these impulses to the motor neurons. These conduct impulses
from the brain or spinal cord to the rest of the body.
Nucleus
Neurons don't touch each other. When an impulse is
about to move to the next neuron it has to pass a
small space called the synapse. At the end of the
axon a chemical is released which flows across the
synapse and makes the impulse pass to the next
dendrite.
The nervous system is divided in 2, the central nervous
system (CNS) and the peripheral nervous system
(PNS).
The central nervous system includes the brain and
spinal cord. The brain controls all the body's
activities. The spinal cord is made up of many
neurons. It is about the with of a thumb and 43cm
long.
Every nerve that connects the brain and spinal cord to the rest of
the body is part of the PNS. It includes 12 pairs of nerves that
connect to the brain called cranial nerves, and 31 pairs that
connect to the spinal cord called spinal nerves. Spinal nerves
carry impulses from your brain to all your body and from your
body to the brain. Some only have sensory neurons and some
have only motor neurons but most have both.
The PNS is divided in 2. The somatic system controls
voluntary actions like talking. It has cranial and spinal
nerves that go to your skeletal muscles. The
autonomic nervous system controls involuntary
actions like breathing.
Your nervous system controls all your actions and an injury to it
could be very dangerous. For example a hard blow to the back
of your head can make you lose your vision. And an injury to
your spinal cord can make you paralyzed. This is why you
must protect yourself.
A reflex is an involuntary response to stimulus. It
allows the body to respond without having to think.
They occur when your touch something sharp, very
hot or cold and others. Reflexes are controlled by the
spinal cord. Then the brain helps the pain stop.
Some drugs like alcohol and caffeine affect the nervous
system. Alcohol moves through the neurons cell
membrane and disrupt their normal functions.
Caffeine speeds up the central nervous system.
References
Glencoe science level green