Transcript 20-1 The Nervous System – how it works

Chapter 20
The Nervous System
20-1
The Nervous System – How it Works
20-1
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Receives information
about what is
happening outside
your body (the
senses), and what is
happening inside the
body.
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It also directs the way
body responds to this
information, as well
helping to maintain
homeostasis.
20-1
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Stimulus is any change or
signal in the environment
that can make an organism
react.
Bright Light
Food
A response is what your
body does in reaction to a
stimulus.
Bright light - squint
Smells of food cooking –
mouth waters.
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The cells that
carry
information
are neurons,
and the
messages are
called nerve
impulses.
A multi-polar neuron has more
than one nucleus. A uni-polar
neuron contains a single
nucleus.
– Nucleus – “the brain of the cell”.
– Axon: carries impulses away
from the cell body.
– Dendrites: Branch-like stems
that carry impulses towards the
cell body
– Synapses: tiny spaces between
the axon of one neuron and the
dendrite of another neuron.
Diagram of Neuron
There are 3 kinds of Neurons
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1. The Sensory Neurons: picks up stimuli
from the external/internal environments and
converts the stimuli into nerve impulses.
 2. Inter-neurons: Carries nerve impulses
from one neuron to another neuron.
 3. Motor Neurons: Sends an impulse to a
muscle – muscle contracts.
Communication

Chemicals such as seratonin are released by
the axon tip and carried across to the
structure.
Remember the communication line: Axon
sends messages; Dendrites receive
messages. Synapses are the spaces in
between each.
20-2
Divisions of the Nervous System
There are two divisions that
work together:
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(CNS) The Central
Nervous System: (The
brain). The brain is
located in the skull
and is the control
center of the body.
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(PNS) The Peripheral
Nervous System
consists of the spinal
cord, a thick column
of nerve tissue, that
links the brain to most
of the nerves in the
PNS.
The nerves of the PNS can be
divided into two groups:

Somatic Nervous
System: Controls
voluntary actions,
such as walking,
eating, and writing.
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Autonomic Nervous
System: Controls
involuntary actions
such as breathing, and
your heartbeat.
PNS cont’d
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The PNS consists of a network of nerves
that branch out from the CNS and connect
to the rest of the body. There are a total of
43 pairs of nerves that make up the PNS.
The Brain
The Brain
The Brain
MRI Brain Image
Pet Scan of Brain
Normal Brain vs. Alzheimer’s
The Brain
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The brain weighs about 3 pounds and
contains about 100 billion nerve cells
(neurons). You are born with every nerve
cell you will ever have. Neuron cells do
not reproduce. It is important to exercise
our brains which causes stimulation.
Alcohol and drugs do kill brain cells, and
these cells cannot be repaired.
Looking Inside
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1. The cortex, involves thought, language,
voluntary motion, reasoning, and
perception.
 2. The midbrain involves vision and eye
movement, and body movement.
 3. The cerebellum: “Little brain”, involves
movement, posture, and balance.
Inside – con’d
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4. The brainstem: involves the heart rate,
breathing, and the blood pressure –
involuntary actions.
 5. The thalamus: involves sensory
processing and movement.
 6. Hippocampus: this is where learning and
memory takes place.
 7. Limbic System: Emotions.
Laceration of the brain
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Laceration of the brain begins the day we are born.
 Our brain starts separating into two hemispheres –
the right and left.
 Our brains takes about 7-10 years to fully lacerate.
This is why younger children have a better chance
of surviving any kind of brain damage – a new
part of the brain takes over the functions of the
damaged areas. However, once the brain is fully
lacerated, this process is difficult, and usually
brain damage is permanent.
 The two hemispheres communicate via the corpus
callosum.
Are boys smarter than girls?
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Why even question this? Well, there has
been so much research done in this area,
because some theories believe: boys tend to
be more right-brained (logic, reasoning
(math), whereas, girls tend to be leftbrained, (language, communication, and
verbal skills).
Are boys smarter then girls?
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The truth is there is no hard scientific
evidence to suggest this. However,
psychological tests suggest that the sexes
differ in their abilities at different skills.
 Men – logic/math and Women: language
Are boys smarter then girls?
Women’s brains, on average, are slightly
smaller than men’s, but women are also
smaller in body size.
 Studies also suggest women have the same
number of brain cells as men, just crammed
into a smaller space.
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Are boys smarter than girls?
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One important aspect of the debate, girls and boys
brains do develop under the control of different
sex hormones:
boys – testosterone and girls – estrogen.
What does this mean? There is a clear difference for
women, in the structure of the hypothalamus, the
part of the brain that regulates body cycles –
temperature, sleep, emotions, and menstruation.
This area is larger in men than in women..
Are boys smarter than girls?
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No, men and women, on the average, tend
to access one hemisphere more than the
other – leaving each sex with different
skills. On the average. Learning to
exercise our brain into using both sides of
the brain is possible.
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Visual exercises enhances the right side
of the brain.
Diseases and Disorders of the
Brain
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These are just some:
 1. Alzheimer’s Disease: this in not due to
aging, this is a true disease that involves
memory loss and emotions. Sometimes
drug users and alcohol abusers can develop
Alzheimer's in later years.
Asperger
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This is a disease said to be a form of autism.
Asperger usually affects boys, and deals
with social and communications problems,
however, usually a person with asperger has
average intelligence, or above average
intelligence – socialization is the main area
of the disorder.
Gulf War Syndrome
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This disorder is due to chemical nerve
agents used during the war. When the
soldiers returned home, symptoms appeared
in the form of:
– Concentration and memory problems
– Rashes, headaches, muscle/joint pain
– Respiratory problems
Some other disorders
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ADD/ADHD
Autism
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Mental Health: Schizophrenia, bipolar disorder, manic depression
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Spina Bifida
Tourette Syndrome
Narcolepsy
Dyslexia
Epilepsy
Fetal Alcohol Syndrome
Huntington’s Disease
Lead Poisoning
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Lyme Disease
Multiple Sclerosis
Stroke
Repeated Concussion (Soccer brain)
20-3
The Senses
The Five Senses
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Sight
 Hearing
 Smell
 Taste
 Touch
The Eye
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Your eye responds to the stimuli of light.
Your eyes convert this stimuli into pulses
that your brain interprets, then enabling you
to see.
• What do you see below?
A Square
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Although the picture on the previous page is
missing a full line to complete the square –
your brain actually fills in the missing
information by drawing upon your databank
in the memory.
Divisions of the eye
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Iris: regulates how much light enters the eye.
Pupil: opening in the eye in which the light
enters.
Cornea: Light first strikes the eye here and begins
to pass through.
Retina: this is where nerve impulses begin.
Optic Nerve: carries nerve impulses from the
retina to the cerebrum.
Need glasses?
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Nearsighted:
 You can see
close-up
clearly,
however, you
have trouble
seeing far
away.
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Farsighted:
 You can see distant objects
clearly, but you have
trouble seeing close-up.
 Farsighted is also part of
the aging process – about
the age of 40 – seeing
close-up becomes difficult.
Hearing – The Ear
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The ear converts sound to nerve impulses
that your brain then interprets.
 There are three divisions of the ear:
– The outer ear.
– The middle ear
– The inner ear.
Important parts of the ear:
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The eardrum: vibrates when sound waves
hit it.
 The Semicircular Canals: balance
 The 3 bones in the middle ear, (Malleus,
Incus, and Stape), transmit the vibrations
from the eardrum to the Cochlea (inner ear).
Taste, Smell, and Touch
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The sense of smell and taste depend on
chemicals to trigger responses.
 The tongue has four area’s of taste:
– Salty (Fish), bitter (Coffee), Sweet (Sugar), and
Sour (lemon/lime).
The sense of touch is controlled by the skin: pain,
temperature, heavy pressure and light touch.
20-4
Alcohol and Drugs
Facts about 8th graders and
alcohol
Nearly 70% of 8th graders perceive alcohol
as very easy to attain.
 Approximately 20% of 8th grades have had
alcohol in the last 30 days.
 About 20% of 8th graders report having
been drunk at least once already in their life.
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Consequences
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A teenager who begins drinking this young is 4 times as
likely to develop alcohol dependence.
 During adolescence, significant changes occur in the body,
including the formation of new networks in the brain,
which can be affected.
 Alcohol is associated with many adolescent risk behaviors:
other drug use, weapon carrying or fighting, perpetrating
or being the victim of date rape.
 For ages 15-20, motor vehicle accidents are the leading
cause of death, where alcohol is usually involved.
 Alcohol use is also linked with youthful deaths by
drowning, suicide, and homicide.
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A drug is any chemical  Medicines are legal
that causes change in a
drugs that help the
person’s behavior:
body to fight
infections, diseases,
– Coffee
and injuries.
– Cigarettes
– Alcohol
– Tylenol
– Diet pills
– Antibiotics
Most Common Abused Drugs
Alcohol
Marijuana
Cocaine
Tolerance
Most abused drugs alter, or change a person’s
mood and feelings.
 When someone develops an addiction to a drug,
they may develop a tolerance as well. Tolerance is
a state in which the drug has been used so much,
the user now needs larger and larger amounts to
get the same effect. Tolerance can lead to
overdosing and death.
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Withdrawal
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For a drug abuser and certain drugs, the body
develops a physical addiction. When you miss a
dose, the body goes into withdrawal.
– Coffee – caffeine can be addictive. When an avid
coffee drinker suddenly gives up their coffee intake,
migraines can occur.
– Heroine: Fever, shakes, nausea, and severe pain.
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Drug Divisions
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Depressants: Slows down the activity of the
CNS – alcohol.
 Stimulants: Speed up the body process –
nicotine, diet pills, and caffeine.
 Inhalants: Are inhaled through the nose and
are extremely dangerous. (Aerosol cans)
 Hallucinogens: Marijuana or Ecstasy
 Steroids: synthetic chemicals; hormones