chapter 3 - coordination and response[1]

8/2/2019 Chapter 3 - Coordination and Response[1]

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3.1 COORDINATION AND RESPONSE Stimulus: any change or signal in the environment that can

make an organism react

2 type of stimulus :1) external stimuli : outside the body

e.g : light, sound, smell, taste, temperature,

pressure and touch

2) internal stimuli : inside the bodye.g : sugar level, body temperature, osmotic

pressure

Response : the reaction of the body towards stimulus


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Response and coordination

Oxygen content

Bodytemperature

External

Light

Sound

SmellTaste

Temperature

Osmotic PressureTouch

Stimuli

Internal


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NECESSITY FOR LIVING ORGANISMS

TO RESPOND TO STIMULI

To adjust to external stimuli by making suitable

coordinated response

To enable the organism move, feel pain or taste

To protect organisms from harm

To ensure their survival

To regulates equilibrium of the internal

environment.


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RESPONSES OF HUMANS, ANIMALSAND PLANTS TO STIMULI

Humans and animals :Respond to the external and internal

environment by coordinating functions

throughout the body

Plants :Response by growth movement (tropism),

movement of parts of plant (nastic)


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PATHWAYS INVOLVED IN DETECTING &RESPONDING TO CHANGES IN EXTERNAL

ENVIRONMENT The receptor : sensory organs, detect the stimuli. It triggers a

nerve impulses to be produced in the afferent neurone.

Afferent neurone : carries the nerve impulses to theintegrating centre

Integrating center : Brain & spinal cord, interprets theinformation and sends out another nerve impulse

Efferent neurone : carries the nerve impulses from brain tothe effectors

Effectors : response to the stimulus (muscles or glands)


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STIMULUS

RECEPTOR

INTERGRATING CENTRE

EFFECTOR

RESPONSE

AFFERENT NEURONE

EFFERENT NEURONE


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STIMULUS :Light from a candle

RECEPTOR :Photoreseptors

in the retina of eyes

RESPONSE:Move towards the candle

AFFERENTNEURONE

EFFERENTNEURONE

PATHWAY INFORMATION DUE TOEXTERNAL STIMULI

EXAMPLE : SOUND OF DOOR BELL

INTERGRATION : occurs in visual centre of the brain

EFFECTOR :Muscle in legs


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PATHWAY INFORMATION DUE TOINTERNAL STIMULI

EXAMPLE : CHANGE IN BODY TEMPERATURE

STIMULUS :A change inblood temperature

RECEPTORS :Temperature sensitive cells

in hypothalamus

INTERGRATIONThermoregulatory centre

of the hypothalamusEFFECTORS :Smooth muscle of arterioles,

sweet gland, erector muscle of skin,skelatal muscle, adrenal glands

& thyroid glandsRESONSE :

Activities heat lossfrom blood vessel

NORMALBLOOD TEMPERATURE


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Meaning of Coordination

Is the process involved in the detection of stimulusand the subsequent response of the organism towardsthe stimulus

Each response to a stimulus needs to be coordinated withother responses, otherwise there would be chaos.Example: eating requires muscle coordination to get thefood into the mouth and to cause chewing, swallowingand peristalsis and the coordination of the glandssecreting saliva and digestive juices at the right time.


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Organisation of Nervous System

Human nervous system

Brain

Peripheral nervous systementral nervous system

Spinal cord Spinal nerves Cranial nerves


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Central nervoussystem (CNS)ranial nerves

Spinal nerves

Peripheralnervous system(PNS)


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Role of Nervous System Nervous system is a communication network

Receives information from receptors

Transmit and interprets the information

Formulates appropriate response to be sent to theeffector organs

Controls and coordinates functions throughout thebody

Helps to maintain homeostasis


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Are you more right brain or left brain?


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Right Brain Inventory Left Brain Inventory

Visual, focusing onimages, patterns

Verbal, focusing onwords, symbols, numbers

Intuitive, led by feelings Analytical, led by logic

Process ideassimultaneously Process ideassequentially, step by step


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STRUCTURE AND FUNCTIONOF THE BRAIN

Consists of 100 billion neurones and weighs about1300 1400 g in an adult

Main parts of human brain are :1) cerebrum2) cerebellum3) medulla oblongata4) thalamus5) hypothalamus


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Cerebrum

The largest and most complex region Divided into 2 parts :1) right hemisphere : control activities on left side of

body2) left hemisphere : control activities on right side of

body The outer region of cerebrum is the cerebral cortex It has folds and grooves to increase the surface area of the cerebrum Function :

- interprets information from receptors and controls the

movement of skeletal muscles and voluntary activities (under ourconscious)

- site of intelligence- carries out complex mental processes such as learning, speechremembering making judgments


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Cerebellum Second largest region Located below the cerebrum and near the top of the spinal

cord

Has 2 hemisphere Function :

- coordinates the contraction of the muscle

- helps control balance to produce precise

movements


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Medulla oblongata

Contains a number of vital centres for regulatingheartbeat, breathing and vasoconstriction.

Contains the reflex centres for vomiting, coughing,sneezing, hiccupping and swallowing


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Hypothalamus

Hypothalamus : below thalamus,

maintain homeostasis

control centre for recognition and analysis of sleep,hunger, body temperature, blood pressure and waterbalance

Control pituitary glands (secrete hormones that

influence other glands)


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Thalamus Thalamus : is made up of two masses of grey matter It lies deep in the cerebral hemispehes

Contain relay stations for impulses responsiblefor sorting information which goes in andcomes out of the cerebral cortex

integrates the information that is carried out by

sensory receptors to the cerebrum byenhancing some signals and blocking


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SPINAL CORD The link between the brain and the peripheral nervous system

Contained within the vertebral column Surrounded by cerebrospinal fluid (as a cushions the

cord and provides nutrients)

Consists of :

1) grey matter ( in the middle)2) white matter (around grey matter) N : Grey matter

C: i. surrounded by white matter

ii. consists of mainly of cell bodies of nerve cells

N : White matter

C : i. consists of myelin-coated axons of neurones that extend

up and down the spinal cord


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SPINAL CORD Spinal nerves arise from the spinal cord

Each spinal nerves consists of

1) dorsal roots : contains the axons of afferent neuron: conduct impulses to the spinal cord

from sensory receptors: consists of dorsal root ganglion

which composed of cell bodies of

afferent neurones

2) ventral roots : contains the axons of efferentneuron: conduct impulses away from the

spinal cord to effectors


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SPINAL CORD Function of spinal cord :

i. to process certain types of sensory information andsend out responses via the efferent neurons

ii. Convey signals to and from the brainiii. Neural pathway for reflexes


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A Neurone has :1)Function : transmit nerve impulses to other nerve cells, gland or

muscles

2) There are 3 types of neurones:i. Afferent or sensory neurones:

: carry sensory information from receptor cells into the brain andspinal cord

ii. Efferent or motor neurones:: carry information from the brain or spinal cord to effectors,muscle or gland cells

iii. Interneurone:: conveys impulses between various parts of the brain and spinal

cord: transmit impulses between afferent neurones and efferentneurones

: transmit impulses from one side of the spinal cord to the otherside of from the brain to spinal cord or vice versa


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Afferent NeuronMoving away from a central organ or point. Relays messages from receptors to the

brain or spinal cord

Efferent NeuronMoving toward a central organ or point

Relays messages from the brain or spinal cord to the muscles and organs


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Interneuron (relay neurone):Relays message from sensory neurone to motor neurone

Make up the brain and spinal cord


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A Neurone has :1) Cell body :

- contain nucleus

- integrates signals and coordinates metabolic activities

2) Dendrites :- threadlike extensions from cell body

- carry impulses towards cell body

3) Axons :- long and thin fibre from cell body

- carry impulses away from cell body

- surrounded by myelin sheath to protect and insulates the axons and help speed

up the conduction of nerve impulses

- myelin sheath has many gaps called node of Ranvier

4) Axon terminals / synaptic terminals:- ending of axons

- have small swelling called synaptic knobs

- transmits signals to muscle cells, gland cells or the dendrites of another neurone


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Neurone : the cells that carry information through the

nervous system The message that a neurone carries in the form of an

electrical signal called nerve impulses


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Afferent neuron Interneuron Efferent neuron

Length ofFibers

Long dendrites and

short axon

Short dendrites

and short or

long axon

Short dendrites

and long axons

Location Cell body anddendrite are

outside of the

spinal cord; the cell

body is located in a

dorsal root ganglion

Entirely within

the spinal cord

or CNS

Dendrites and

the cell body are

located in the

spinal cord; the

axon is outside

of the spinal

cord

Function Conduct impulse tothe spinal cord

Interconnect the

sensory neuron

with appropriate

motor neuron

Conduct

impulse to an

effectors

(muscle or

gland)


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The transmission pathway of information

1 Stimulus (sound of doorbell)


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1. Stimulus (sound of doorbell)

2. Receptors in the ear detect stimulus

3. Afferent neuroneThe receptors triggers nerve impulses in the afferent neurone

4. InterneuroneAfferent neurone carry the nerve impulses to the interneurone in the brain

5. Central nervous systemThe brain integrates and interprets the nerve impulses.

The brain make a decision and send out the nerve impulses to efferent neurone

6. Efferent neuroneCarry the nerve impulses to effector

7. EffectorContraction of muscle in the hand carry out the response

8. ResponseThe hand reaches out to open the door


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Transmission of information across synapses- Synaptic cleft narrow space beyond the synaptic terminal

- separates the synaptic terminal from the dendrite ofa receiving neurone, a muscle cell or gland cell

- The electric signal carrying the message must be transmitted acrossthe synaptic cleft to the adjacent cell

BUT HOW?- Transmission occurs via a chemical process as opposed to an

electrical process

- the transmission of information is slowest at the synapse.- Snake venom block the action of neurotransmitter and cause

paralysis


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Transmission of information

across synapses
http://www.sciencemag.org/sciext/vis2005/show/images/slide1_large.jpg


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Transmission of information across synapsesNEUROTRANSMITTERS

- The chemical substances involved in transmission

- Store in small synaptic vesicles clustered at the tip ofthe synaptic terminal

- There are many neurotransmitters among which are :i. acytycholine

ii. Noradrenaline

iii. Serotonin

iv. Dopamine- After the neurotransmitter relayed its message it is

rapidly broken down by an enzyme or taken up bysynaptic terminal and recycled


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Transmission of information across synapses- Synaptic vesicle only present at synaptic terminals, hence

only the presynaptic membrane can dischargeneurotrasmitters

- Receptor only present on the postsynaptic membrane,

ensuring that only the postsynaptic membrane can receivea chemical signal

- The importance of synapes:i. controlling and intergrating nerve impulses by

that are transmitted by stimulated receptors.ii. Allow nerve impulses to be transmitted in one

direction


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Mechanisms of transmission across synapsesElectrical impulses reaches the presynaptic membrane

Triggers the synaptic vesicles to release neurotransmitters into the synaptic cleftNeurotransmitter diffuse across the synaptic cleft and bind with receptors (specific

protein), attached to the postsynaptic membrane

Lead to the generation of a new electrical signal in the neighbouring neuron

Transmission of information across a synapse first involves conversation of an electricalto chemical signal (neurotransmitter)

Reconversation : chemical to electrical at postsynaptic membrane

After the neurotransmitter has relayed its message, it is rapidly broken down by enzymesor taken up again by the synaptic terminal and recycled


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CocaineCocaine is a strong central nervous system stimulant that increases levels ofdopamine, a brain chemical (or neurotransmitter) associated with pleasure and

movement,Certain brain cells, or neurons, use dopamine to communicate. Normally,dopamine is released by a neuron in response to a pleasurable signal (e.g., thesmell of good food), and then recycled back into the cell that released it, thusshutting off the signal between neurons.Cocaine acts by preventing the dopamine from being recycled, causing

excessive amounts of the neurotransmitter to build up, amplifying the message toand response of the receiving neuron, and ultimately disrupting normalcommunication.It is this excess of dopamine that is responsible for cocaines euphoric effects.With repeated use, cocaine can cause long-term changes in the brains rewardsystem and in other brain systems as well, which may eventually lead toaddiction.With repeated use, tolerance to the cocaine high also often develops. Manycocaine abusers report that they seek but fail to achieve as much pleasure asthey did from their first exposure. Some users will increase their dose in anattempt to intensify and prolong the euphoria, but this can also increase the risk

of adverse psychological or physiological effects.


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COORDINATION

VOLUNTARY INVOLUNTARYI/C : Brain / CerebrumE : Skeletal muscleExample: Talking

WalkingThinking

I/C : Medulla oblongata /hypothalamus

E : Smooth muscleExample: Homeostasis

I/C : spinal cordE : Skeletal muscleExample: hot and sharp

knee jerk


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Voluntary Action- Skeletal muscle- Examples: walking, talking etc- Under conscious control

- Governed by the cerebral cortex of the cerebrum

Receptor Interneuronefferent neurone

Efferent neuroneffector


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Involuntary Action Skeletal Muscle : reflex arc

Examples: touching a hot stove or a sharp pin, removefinger without having to think about it

- Under unconscious control

- Reflexes rapid and involuntary responses to stimuli

- The nerve pathway involved in a reflex action is called areflex arc

TOUCHING A HOT OBJECT (THREE NEURONE)


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When the skin is in contact with a hot object, sensory receptor in skin is stimulated

Sensory receptor at skin triggers nerve impulse move through afferent neuroneto the spinal cord

This nerve impulse across the synapse to the interneurone in grey matter of spinalcord

From interneurone, the nerve impulse crosses another synapse and is transferredTo efferent neurone

Efferent neurone brings out nerve impulse from the spinal cordto effecctor (biceps muscle)

Biceps muscle is stimulate to contract causing the hand to move away from the hotobject


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KNEE JERK TWO NEURONE


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The hammer hits a tendon that connects the quardiceps musclein the thigh to a bone in the lower leg

As the hammer strikes the tendon, the force stretches thequadriceps muscles And stimulate the stretch receptors

in the muscles, tiggering nerve impulsesAfferent neurone transmits the information to the

efferent neurone in the spinal cordThe efferent neurone transmits this impulse to the quardiceps

muscle,and the muscle contact swings the leg forward


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Diseases of the nervous systemAlzheimers

- A neurologica, disease- Caused by the shrink of brain tissues and lack ofneurotransmitter such as acetylcholine- Usually affects the elder- The symptoms are:loss of intellilgence, loss of memory, mildconfusion and poor concentration- Also inherited


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Diseases of the nervous systemParkinsons

- A neurologica, disease- Caused by :i. The reduce level of neurotransmitter(dopamine) in the braincaused weakening of the musclesii. The huge of the cerebral arteries- When it happens the muscles cannot function

smoothly and become stiff and jerky in theiractions- Usually affects the elder- No inherited


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Endocrine system :

Controls the bodys activities by releasing hormones Made up of endocrine glands Does not have ducts Consists of endocrine glands that produce and release

hormone directly into bloodstream and the blood carriesthe hormones to the target cells Can regulate activities in tissues and organ situated farfrom the glands The endocrine system complements the nervous system

H


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Hormones :

Chemicals in the bloodstream that can regulate theactivities of organ and tissues.

Functions

of hormone

Reproduction Growth Homeostasis


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NERVOUS SYSTEM ENDOCRINE SYSTEM


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NERVOUS SYSTEM vs ENDOCRINE SYSTEM

NERVOUS SYSTEM ENDOCRINE SYSTEM

Control voluntary & involuntary

actions

Control involuntary actions

Conveys electrical signals

(nerve impulses)

Conveys chemical signals

(hormones)

Messages are conducted via

neurones

Messages are conducted via

bloodstream

Messages are conveyed rapidly Messages are conveyed slowly

Messages are carried betweenspecific locations

Messages are carried to variouslocations

Responses & effects are temporary

& reversible

Responses & effects are long lasting

& irreversible


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MAJOR GLANDS OF THE ENDOCRINE SYSTEM


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MAJOR GLANDS OF THE ENDOCRINE SYSTEM

Pituitary gland

Thyroid gland

Adrenal gland

Pancreas

Gonads

(testes & ovary)

ENDOCRINE HORMONE Target FUNCTION


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ENDOCRINEGLAND

HORMONE Targetorgan

FUNCTION

Anterior pituitary

gland

-Blood pressure

-Growth

-Water balance

-Produce hormonesto regulate activities

of other glands

Thyroid-stimulating

hormone (TSH)

Thyroid Stimulates the synthesis

and release of thyroxine

from thyroid gland

Follicle stimulating

hormone (FSH)

Gonads Stimulates production of

mature sperm & eggs

Luteinising hormones

(LH)

Gonads Stimulates ovulation &

corpus luteum () & sexhormones ()

Adrenocorticotrophic

hormones (ACTH)

Adrenal

glands

Stimulates adrenal cortex

to release hormone

Growth hormones Soft tissue,bones

Stimulates proteinsynthesis and growth

Prolactin Mamary

gland

Stimulates milk

production


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ENDOCRINEGLAND HORMONE TARGETORGAN FUNCTIONPosterior

pituitary gland

Antidiuretic

hormones

(ADH)

Kidneys Stimulates kidneys to

reabsorb water

Oxytocin Uterus &

mamary gland

Stimulates contraction

of uterine muscles

during childbirth and

stimulates spermejaculation

FUNCTION OF HORMONES PRODUCED BY


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FUNCTION OF HORMONES PRODUCED BYENDOCRINE GLANDS

ENDOCRINEGLAND

HORMONE TARGETORGAN

FUNCTION

Thyroid gland thyroxine All tissues -Regulates the bodys

metabolism

-Helps in normal physical and

mental developements

Adrenal gland Adrenaline

(adrenal

medulla)

Kidneys Increase heartbeat rate,

breathing rate, blood pressure,

metabolic rate, blood flow th

the muscles and glucose level in

blood (emergency situation)

Aldosterone

(adrenal

cortex)

Cardiac and

other muscle

Regulates the reabsorption of

sodium ions in the kidneys

FUNCTION OF HORMONES PRODUCED BY


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FUNCTION OF HORMONES PRODUCED BYENDOCRINE GLANDS

ENDOCRINE GLAND

HORMONE TARGETORGAN

FUNCTION

Pancreas Insulin Liver,muscleandadiposetissue

- Stimulates the conversion ofexcess glucose to glycogen

- Lower the level of glucose in theblood

Glucagon Liver,muscle,adiposetissie

- Stimulates the breakdown ofglycogen to glucose

- Increases the level of glucose inblood


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ENDOCRINEGLAND

HORMONE TARGETORGAN

FUNCTIONOvaries Estrogen Gonads, skin,

mucsle &

nones

- stimulates the development of

eggs and female reproduction

organ

- stimulates the development of

secondary characteristics in

Progesterone Gonads - prepares the uterus for

implantation of embryo

testes Testosterone Gonads, skin,

mucsle &

nones

-Stimulates sperm production

and development of testes

-stimulates the development of

secondary characteristics in


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Secretion of hormones

Hormone secretionis regulated by

Another hormoneLevel of certain

substancesNervous system

Secretion of hormones:


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Secretion of hormones:by another hormone

Hypothalamus

Thyroid gland

Pituitary gland

TRH

TSH

Thyroxine

Target cell

Example :

S ti f h


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HIGH thyroxine levelLOW thyroxine level

TSH thyroxine

thyroxineTSH

Inhibits

Inhibits

Stimulates

Stimulates


Secretion of hormones:


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Pituitary gland

Anterior lobe Posterior lobe

HORMONE TARGET ORGAN HORMONE

ACTH Adrenal gland aldosterone

TSH Thyroid gland Thyroxine

FSH & LH Ovaries, testes Oestrogen,progesterone,testosterone

GH Bone & muscle x

PRL Mamary gland x

HORMONE TARGETORGAN

ADH Kidney

Oxytocin Smoothmuscle inuterus

Secretion of hormones :


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Secretion of hormones :by level certain substances

Example :Glucose

High glucoselevel

Glycogen(stored in liver

& muscle)

Insulin

Glucagon

Secretion of hormones :


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Secretion of hormones :by nervous system

EXAMPLE : Pituitary gland is controlled by hypothalamus

Hypothalamus receives nerve impulses from receptorthen stimulates pituitary gland

EXAMPLE :

Adrenal gland stimulated to release hormones bynervous system


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Coordination involving both thenervous system and endocrine system

During fight or flight situation

Example : excited, frightened

The hypothalamus send nerves impulses to

adrenal medulla

Adrenal medulla secrete adrenaline &

noradrenaline

Heartbeat, breathing rate, blood pressure, blood

glucose level and metabolic activity increases

Hormonal Imbalances and Related


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Disease DWARFISM

The organs of the person often fail to grow and the bodyproportion is childlike

Induce with growth hormone using genetic engineering

GIGANTISM

Condition characterised by an abnormal increase in the length of

bones

The person grows to be abnormally tall

ACROMEGALY

Caused by the over secretion of human growth hormone during

adulthood results

A condition in which the bones, hands, feet, cheeks and jaws

thicken and other tissues enlarge



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Disease

CRETINISM (chillhood)

Too little thyroxine secretion cause severe mental retardation

MYXEDEMA (adult)

Have slow heart rate, low body temperature, high sensitivity to

cold, general lethargy and a tendency to gain weight easily

A lack of iodine in the diet also lowers the production of

thyroxine

Too much secretion of thyroxine can cause an increase in the

metabolic rate of the body

Symptoms: excessive sweating, heat intolerance, increased bowel ,

nervousness, rapid heart rate and weight loss



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Disease

GOITER Thyroid gland grow and enlarge to two or three times its size

Cause of goiter is iodine deficiency

Thyroid cannot make and release enough thyroxine

So it enlarges in response to excess stimulation from the pituitarygland



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Disease DIABETES MELLITUS

Is a chronic condition associated with abnormally high levels ofglucose in the blood

People with diabetes mellitus either do not produce enough

insulin or cannot use the insulin that either bodies produce

So glucose builds up in the bloodstream Symptoms :

i. increased frequency of urination

ii. Excessive thirst

iii. Numberness or burning sensation in the feet, ankles and legs

iv. Blurred or poor vision

v. Fatigue and poor wound healing

Secure : i. insulin are produce by genetically engineered bacteria



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Disease HYPOGLYCAEMIA

Over secretion of insulin an abnormally low level of glucose inthe blood

Symptoms :

i. Fatigue

ii. Insomniaiii. Mental confusion

iv. Nervousness

v. Mood swings

vi. Faintness and headaches

vii. Several hypoglycemia can lead to convulsions and

unconsciousness



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Disease DIABETES INSIPIDUS

Caused by the inability of the posterior pituitary to secrete

antideuretic hormone (ADH)

Symptom :

i. Excretes a large amount of urineii. Thirsty all the time

iii. The person may die of dehydration if deprived of water even

for a day


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LEARNING OUTCOMES

1. state what plant hormones are,

2. give some examples of plant hormones,

3. infer the effects of auxins on growthresponses,

4. explain the role of auxins in tropism,

5. state the use of hormones inagriculture.


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1.CONCEPT

D E S

DDefinitiongive meaning

E Examplegive suitable example

S Significantgive the (good / bad) effect


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PLANT HORMONESIn plants, response is controlled by plant

hormones @ plant growth regulators

Aplant hormoneis achemical substancewhich is produced by the plant andinfluences the growthanddevelopmentofthe plant

Examples :auxinsandethylene


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PLANT HORMONESDDefinition=Classification+characteristicPLANT HORMONES:

is achemical substance + produced by the plantEExample

auxinsandethyleneSSignificant

influences the growthanddevelopmentof the plant


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Effects of auxins on growth responses

Plants respond to stimuli by growing in acertain direction.This growth response calledtropism

These responses are controlled by auxins


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What is the role of auxins ingrowth response?


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ColeoptileIs a tough protective sheath that enclosesthe shoot tips of monocotyledonous plant

(Example : maize, paddy, oat)

When the coleoptile degenerates during

seed germination, the shoot emerges


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AUXINS

Function :1) promotecell elongationorcelllengthening2) increase the rate of cell division

Are produced in the apical meristem of thecoleoptile at the tips of shoots

As auxins from the tips of the shoots moves downto the region of cell elongation , the hormonestimulates growthandelongationorlengthening

Experiment to investigate the effect of auxins on


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growth of coleoptileColeptile in the dark

E1

Tip of coleoptile

cut off just

above zone of

elongation

E2

Tip placed on jelly-

like block of agar @

gelatin

E3

Tip placed on agar block

and placed on one side

of coleoptile

After 2hours

After 2hours


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Tip removed Agar block placed on

cut coleoptile

agar block placed on

one side of

coleoptile

Tip removed:no further growth

Tip replaced :coleoptile grows

straight up

coleoptile grows

straight up

coleoptile grows in

a curve


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What conclusion can you make on theeffects of auxins on growthresponse? Auxins are produced in the apical meristem ofthe shoot.

Auxins promotes theelongation of cellsin theshoot.


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Effects of auxins on the growth response in shoots


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What is tropism?

Type of responsewhere thedirection of growth isdeterminedby the direction of the stimulus


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Example of tropismTropism Stimulus Response

Phototropisme

Geotropisme


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Phototropisme Direction oflight fromone side

Geotropisme


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Geotropisme Force ofgravity


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PhototropismeDirection of

light fromone side

1.Shootbent toward light(Positive phototropisme)2.Rootsgrow away from light(Negativephototropisme)

Geotropisme Force ofgravity


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1.Shootbent toward light(Positive phototropisme)2.Rootsgrow away from light(Negativephototropisme)

GeotropismeForce of

gravity

1.Shoots grow upwards against the

force of gravity

(Negativegeotropisme)2.Roots grow downwards in the

direction of gravity(Positive geotropisme)


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Phototropisme & GEOTROPISME


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Conclusion1. The tip of the coleoptile is the light-

sensitive region

2. The meristem cells at the tip of shoot produces

auxins

3. Auxinsmove awayfrom the light &accumulate inthe shaded side4. High concentration of auxins in theshootpromoteelongation of the cell in shoot5. High concentration of auxins in therootinhibitelongation of the cell in root

Geotropism


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Geotropism


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Commercial uses: Auxins1. In hormone rooting powder(produce rootquickly)2. In selective weed killer

3. In fruit setting(parthenocarpy)4. In producing bushy plants5. In promoting growth of plants & fruits

Commercial uses: Auxins


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Auxins are used for a variety of agricultural purposes,

including:Promotion of rooting of cuttings (e.g., Rootone). Thebase of the cutting is dipped in a powder containing NAAor indolebutyric acid (IBA) prior to planting.

Induction of flowering in pineapple (actually caused by

the auxin-induced production of ethylene). NAA isgenerally employed as the auxin.

Prevention of preharvest fruit drop.

Auxin type herbicides (e.g., 2-4-D).


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Commercial uses: Ethylene / ethene Promoting the ripening of fruit Fruits can be ripened quickly for sale by

exposing them toethylene gas Ethylene stimulating the production of

cellulase Cellulase hydrolyses cellulose in plant cell

walls making the fruit soft

Also promotes the breakdown of complex

carbohydrates into simpler sugarthe fruit

become sweeter


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ANSWER


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(i) Auxin/ Giberelin

(ii)

F1: Hormone / Auxin / Giberelin induces the

wall of ovary to develop.

F2 : Ovary wall develops into the flash offruit

F3 : Fruit is produced without seed (and

bigger)

F4 : Formation of fruit without fertilization.

(iii) Parthenocarpy


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~ END ~

chapter 3 - coordination and response[1]

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