Chapter 20Chapter 20

The Nervous System

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The Nervous System – How it Works

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Receives information about what is happening outside your body (the senses), and what is happening inside the body.

It also directs the way body responds to this information, as well helping to maintain homeostasis.

20-120-1 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.

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 NeuronDiagram of Neuron

There are 3 kinds of NeuronsThere are 3 kinds of Neurons

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.

CommunicationCommunication

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.

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Divisions of the Nervous System

There are two divisions that There are two divisions that work together:work together:

(CNS) The Central Nervous System: (The brain). The brain is located in the skull and is the control center of the body.

(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 The nerves of the PNS can be divided into two groups:divided into two groups:

Somatic Nervous System: Controls voluntary actions, such as walking, eating, and writing.

Autonomic Nervous System: Controls involuntary actions such as breathing, and your heartbeat.

PNS cont’dPNS cont’d

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 BrainThe Brain

The BrainThe Brain

The BrainThe Brain

MRI Brain ImageMRI Brain Image

Pet Scan of BrainPet Scan of Brain

Normal Brain vs. Alzheimer’sNormal Brain vs. Alzheimer’s

The BrainThe Brain

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 InsideLooking Inside

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’dInside – con’d

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 brainLaceration of the brain

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?Are boys smarter than girls?

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 left-brained, (language, communication, and verbal skills).

Are boys smarter then girls?Are boys smarter then girls?

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?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.

Are boys smarter than girls?Are boys smarter than girls? 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?Are boys smarter than girls?

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.

Visual exercises enhances the right side of the brain.

Diseases and Disorders of the Diseases and Disorders of the BrainBrain

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.

AspergerAsperger

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 SyndromeGulf War Syndrome

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 disordersSome other disorders

ADD/ADHD Autism Lyme Disease

Mental Health: Schizophrenia, bipolar disorder, manic depression

Spina Bifida Multiple Sclerosis Tourette Syndrome Stroke Narcolepsy Repeated Concussion (Soccer brain) Dyslexia Epilepsy Fetal Alcohol Syndrome Huntington’s Disease Lead Poisoning

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The Senses

The Five SensesThe Five Senses

SightHearingSmellTasteTouch

The EyeThe Eye

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 SquareA Square

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 eyeDivisions of the eye

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?Need glasses?

Nearsighted: You can see

close-up clearly, however, you have trouble seeing far away.

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 EarHearing – The Ear

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:Important parts of the ear:

The eardrum: vibrates when sound waves hit it.

The Semicircular Canals: balanceThe 3 bones in the middle ear, (Malleus,

Incus, and Stape), transmit the vibrations from the eardrum to the Cochlea (inner ear).

Taste, Smell, and TouchTaste, Smell, and Touch

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.

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Alcohol and Drugs

Facts about 8Facts about 8thth graders and graders and alcoholalcohol

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.

ConsequencesConsequences 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.

A drug is any chemical that causes change in a person’s behavior:– Coffee– Cigarettes– Alcohol– Diet pills

Medicines are legal drugs that help the body to fight infections, diseases, and injuries.– Tylenol– Antibiotics

Most Common Abused DrugsMost Common Abused Drugs

Alcohol

Marijuana

Cocaine

ToleranceTolerance

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.

WithdrawalWithdrawal

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.

Drug DivisionsDrug Divisions

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 EcstasySteroids: synthetic chemicals; hormones