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The Nervous System - 7th Grade

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William Begoyan

on 10 May 2018

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Transcript of The Nervous System - 7th Grade

The Nervous System
Page 53 in your ISN
By: Mr. Begoyan
What is the nervous system?
The
nervous system
coordinates an organism's voluntary and involuntary actions and transmits and receives signals between different parts of its body.
The nervous system also maintains
homeostasis,
where variables are regulated so that internal conditions remain stable and relatively constant.
Stimulus
A
stimulus
is a detectable change in the internal or external environment that is picked up by the nervous system.
Response
A
response
is a body's reaction to a given stimulus.
The Neuron
The neuron (nerve cell)
is an electrically excitable cell that processes and transmits information through electrical and chemical signals through the nervous system.
The message that a neuron carries is called a
nerve impulse.
In a neuron, the
dendrite
receives nerve impulses, while the
axon
transmits them.
The nervous system works on a stimulus/response system.
There are 3 types neurons
Unipolar neurons:
Sensory, pick up and transmit stimuli.
Bipolar neurons:
special sensory cells found in sensory organs.
Multipolar neurons:
Motor and internuerons which interpret and transmit the response and connect to muscles.
The location where one neuron transfers the impulse to another is called a
synapse
.
The impulse is carried from one neuron to the next by chemical messengers called
neurotransmitters.
The 2 parts of the nervous system
Central nervous system (CNS)
The brain and the spinal cord make up the
CNS
The brain is divided into 3 major parts.
The
cerebrum
controls all voluntary actions in the body.
The
cerebellum
(little brain) is a region of the brain that plays an important role in motor control and parts of speech.
The
brainstem
controls many basic functions including heart rate, breathing, sleeping, eating, and other involuntary actions.
It also connects the brain to the spinal cord.
The cerebrum is broken into 4 regions:
Frontal lobe
,
Parietal Lobe
,
Occipital lobe
, and the
Temporal lobe.
Each lobe performs specific function(s) for the body.
The
spinal cord
is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brainstem to the bottom of the last lumbar of the spine.
The spinal cord functions primarily in the transmission of neural signals between the brain and the rest of the body, but it can independently control numerous reflexes.
The spinal cord connects the central and peripheral nervous systems.
Peripheral nervous system (PNS)
The
PNS
is the part of the nervous system that consists of the nerves outside of the brain and spinal cord.
The main function of the PNS is to connect the CNS to the limbs and organs.
Essentially serving as a communication relay between the brain and the extremities.
The PNS is
not
protected by the bone or by the blood–brain barrier, which leaves it exposed to toxins and mechanical injuries.
The PNS includes most of the sensory systems.
Sensory organs
The eye
Light first enters the
cornea
, a clear covering of the eye.
The light then passes through an opening called the
pupil.
The
iris
is a band of muscle that will adjust the size of the pupil.
The
lens
focuses the light.
The light then strikes the light sensitive
retina
at the back of the eye.
In the retina there are tiny receptor cells:
rods
(black/white vision) and
cones

(color vision)
.
The impulse is then passed along the
optic nerve
to the brain.
The Ear
Sound first enters the outer ear through a funnel shaped
Pinna
.
Sound waves then pass through the
auditory canal
and enters the middle ear.
In the middle ear, sound waves strike a thin membrane called the
eardrum.
The waves are then transmitted to a series of tiny bones:
Malleus
,
Incus
, and
Stapes
.
The inner ear contains the
Cochlea
, where tiny sensory hairs will vibrate and pass on the impulse to the brain.
Fluid filled canals in the inner ear, the
semicircular ducts
, are responsible for our sense of balance.
The tongue contains tiny sensory organs (
taste buds
) that respond to chemicals in food.
Tongue and Taste
Nose and Smell
A cluster of nerve cells at the top of the nasal passage, the
olfactory bulb
, responds to chemicals inhaled.
Questions 1
1. What does the nervous system do and how does it function?
2. What is a neuron?
3. What are the two important parts of a neuron and what do they do?
4. What are the different types of neurons and what their purpose?
5. What is a synapse?
6. What is a neurotransmitter?
Questions 2
1. What makes up the CNs?
2. What are the 3 parts of the brain?
3. What are the 4 lobes of the cerebrum?
4. What is the purpose of the spinal cord?
5. What makes up the PNS, and what does it lack compared the CNS?
6. Describe how light travels through the eye.
7. Where is the retina?
8. Describe how sound travels through the ear.
9. What is the purpose of the cochlea?
10. How does the tongue work?
11. How does the nose work?
Homework
On page 52, split the page in 2 halves.
On the left, list all of the parts of the CNS with a brief description of each part.
On the right, list all of the parts of the PNS with a brief description of each part.
Colors
and
visuals
are
encouraged
.
signal
Signal
The CNS is protected by bone and by the blood–brain barrier, which protects it from toxins and mechanical injuries.
Glial cells
surround neurons and provide support, protection, and insulation for them.
Full transcript