2010.07.14 control systems chapter 2

8/9/2019 2010.07.14 Control Systems Chapter 2

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CONTROLLINGCONTROLLING

SYSTEMSSYSTEMS

CHAPTER 4CHAPTER 4

CONTROLLINGCONTROLLING

SYSTEMSSYSTEMS

CHAPTER 4CHAPTER 4


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4.2 Senses, the key to our world

For survival an animal depends on informationabout its surroundings so it can escape

predators, find food and locate a mate.

Moths sensors in their antennae can detect

pheromones over a distance of several

kilometers. Scallops eyes sense the changes of

light. The shadow of a predator. Whales and

dolphin use sonar.

There are different types of sensory receptors.

Mechanoreceptors sensitive to touch.

Photoreceptors sensitve to light.

4.2 Senses, the key to our world

For survival an animal depends on informationabout its surroundings so it can escape

predators, find food and locate a mate.

Moths sensors in their antennae can detect

pheromones over a distance of several

kilometers. Scallops eyes sense the changes of

light. The shadow of a predator. Whales and

dolphin use sonar.

There are different types of sensory receptors.

Mechanoreceptors sensitive to touch.

Photoreceptors sensitve to light.


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Thermoreceptors respond to changes in

temperature.

Chemoreceptors sensitive to chemicalespecially in food.

A stimulus is any factor that stimulates a

receptor and brings about a response.

Example is we touch a hot body (stimulus) and

we jerk our hand away (response).

The sensitive skin

Our skin responds to many different

sensations such as touch, pain and

temperature.

Thermoreceptors respond to changes in

temperature.

Chemoreceptors sensitive to chemicalespecially in food.

A stimulus is any factor that stimulates a

receptor and brings about a response.

Example is we touch a hot body (stimulus) and

we jerk our hand away (response).

The sensitive skin

Our skin responds to many different

sensations such as touch, pain and

temperature.


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Receptors alert you to hot surfaces or a biting

mosquito.

Sometimes receptor cells become so used to a

stimulation that they stop responding to it, even

though it is still there. For example when

swimming the water may feel cold for a shortwhile. Becoming used to a stimulus is called

habituation.

How we hearThe grouping together of receptors is common

to sense organs such as the ear. The ear is

responsible not only forsound but also for

balance.


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There are three main parts of the ear.

the outer ear or pinna the visible part.

the middle ear the ear drum and the tiny

bones (hammer, anvil and stirrup).

the inner ear the cochlea.


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The hairs in the cochlea convert the sound

vibrations into nerve impulses that are sent

through the auditory nerves to the brain.

The balance is achieved by the fluid filled

semicircular canals.

ACTIVITY In Action What did you say P.98


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ACTIVITY In Action The bionic ear P.100

The eye, a view of the worldWhen looking at an eye we see the coloured

part in the middle called the iris. It has an

opening called the pupil. Behind the pupil lies

the lens. The lens bends (refracts) light to helpfocus the light rays onto the photoreceptors in

the retina at the back of the eye. Messages are

sent from the photoreceptors via the optic

nerve to the brain.

There are two types of photoreceptors, rods

and cones. Cones are our colour receptors and

work in bright light. Rods work in dim light.


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Fewer cones than normal results in coloured

blindness.


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A sense of smell and taste

The chemoreceptors for taste and smell (theolfactory sense) work together. Food doesnt

taste as good when you have a cold. We have

about 10 000 taste buds on the surface of our

tongue. There are five main tastes.

Sweet Sour Salty Bitter

Unami (savoury)


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In the animal world a sense of smell is

important for survival. Pheromones are used by

animals to recognise a mate, mark out territoryand, sometimes, as an alarm signal.

Questions 4.2 Page 103

4.3 The brain communications centre

The brain controls and regulates all body

functions.

The human brain contains about 100 billionneurones in a space of 200 1400 mL.

Damaged brain cell cannot be replaced.

The brain is protected by a skull.


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In and around the brain and spinal cord is the

cerebrospinal fluid which protects the brain

from hard bumps. The brain is also protected

by three thin membranes. These membranes

are called meninges. Meningitis an

inflammation of the meninges caused by

bacteria or viruses, can be life-threatening.

The cerebrum

The cerebrum occupies more than 80% of the

brain. Its many folds increases the surface area

three time. It controls our conscious thoughts,

controls movement and receives sensory

messages from each part of our body.


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The cerebrum is made up of two parts called

cerebral hemispheres, the left and right side of

the brain. One side normally dominated in aparticular task. Example left, language and

mathematical ability. Right, creative and

emotional.

At the base of the cerebrum is the cerebellum.

It is responsible for coordination and balance.

The brain stem can be seen where the spinal

cord widens. It controls the vital functions,breathing, blood pressure and heart rate.

Experiment 4.4 Long - and short term

memory


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Neurotransmitters, drugs and mental diseases

The neurotransmitters that exist in the gap

(synapses) between the neurones controls

when the nerve fires so they dont all fire at thesame time.

Acetycholine is an example of a neurotransitter.

The lack of it accounts for the disease,Alzheimers


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Some neurotransmitters

Noradrenaline Involved in our state of alertness

Dopamine Associated with emotionalbehaviour and movement. Lack of

causes shaking as in Parkinsonsdisease.

Serotonin Lowered levels of serotonin areassociated with depression.

Enkephalinsand

Endorphins

Pain-deadening neurotransmitters.Their function is mimicked by

morphine, heroin, pethidine and

codeine.


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Question 4.3 Page 107

In Action Pages 108 1094.4 Chemical messengers

Control in animals

Hormones are chemical substances that, justlike nerves, act as messengers in the body. They

are design to stimulate a specific organ, their

target organ.

These hormones are produced by the endocrine

glands. They releases hormones directly into

the bloodstream.


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Hormones Released

from

Target organ Effect

Growthhormone

Pituitary Most body cells Growth

Anti-diuretic

hormone

Pituitary Kidneys Controls urine

flow

Thyroxine Thyroid Many, e.g. liver Controlsmetabolic rate

Insulin Pancreas Liver, muscles Control blood

sugar

Adrenaline Adrenals Muscles, heart

liver

Readiness for

action

Sex hormones Pituitary, testes

and ovaries

Various Sexual

development,

fertility


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Pituitary gland

The pituitary gland controls all other glands. Itcontrols birth contractions, body temperature,

water balance, sleep and growth. It is located at

the base of the brain connected to the

hypothalamus, which provides the link betweenthe nervous and endocrine systems.

Thyroid gland

It is located in the front of the throat, it releasestwo hormones, thyroxine and calcitonin.

Calcitonin takes calcium from the blood and

turns it into bone.


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Thyroxine controls the metabolic rate. It speeds

up cellular respiration.

Steroids

Oestrogen gives females their rounded shape

and testosterone gives males their facial hair.

Anabolic steroids are synthetic growth

hormones that are illegally used by athletes and

bodybuilders.

The adrenal glands secrete adrenaline duringtimes of danger and stress. This increases

heart rate, breathing rate and glucose levels in

the blood.


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Adrenaline is known as the fight or flight

hormone.

In insects, hormones play a major role during

growth, moulting and metamorphosis.


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Control in plants

Plant movement

Plants do respond to their surroundings. Their

responses are called tropisms. Phototropism is

the growth towards light. Geotropism is the

growth of root downwards in response to

gravity.


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Experiment 4.5 Taking control of plants Page

112

Experiment 4.6 If you cut off the tip of a shoot

Page 113

Leaf drop

Plants dont normally drop healthy leaves.

Before a leaf drops, the plant removes any

stored food, the chlorophyll, and much of the

water. Many plants transfer waste product intothe leave before they drop.

Abscisic acid causes the cells to die at the point

where the leaf joins the stem and the leaf drops.


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Commercial use of plant hormones

Growth hormones

Plant hormones are very important

commercially.

Auxin can be used to produce fruit that has notbeen fertilised such as seedless tomatoes and

cucumbers.

Cytokinins can be used to promote bushy pot

plants

Gibberellins are used to thin out flowers and

fruit.


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Fruit ripening

In the early 1900s they discovered that thegases from oranges could ripen bananas. That

gas was ethene (ethylene). Tomatoes, oranges

and picked greens are keep in cold storage and

exposed to ethene when it is time to marketthem.

Flowering

Lengthening the day light hours artificiallyspeeds up the growing time for flowers. This

allows growers to cater to the market demands.


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Questions 4.4 Page 115

Chapter ReviewKey ideas

Review questions


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2010.07.14 control systems chapter 2

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