chapter 12 homeostasis - copy

8/4/2019 Chapter 12 Homeostasis - Copy

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HomeostasisChapter 12


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Learning Objectives12.1 Principles of Homeostasis

a) Define homeostasis

(b) Explain the basic principles of

homeostasis in terms of stimulus resulting

from a change in the internal environment, acorrective mechanism and a negative

feedback


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Homeostasis Homeostasis is

defined as the

maintenance of aconstant internal

environment.


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Changes in body temperature may result inenzyme inactivation or denaturation.

Any drastic changes in our blood and thesurrounding tissues fluid will affect chemicalreactions in the tissue cells and will harm thebody.

Cells must be bathed in tissue fluid of thecorrect pH and water potential. Enzyme

reaction will be affected.


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Negative Feedback Control The internal environment of our bodies

MUST have certain conditions within

tolerable limits to continue the healthyfunctioning.

Done by NEGATIVE FEEDBACK control.

Used to control blood sugar concentration,water concentration & temperature of the

blood.


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Negative Feedback A stimulus, which is the change in the internal

environment

A receptor that can detect the stimulus A self-regulatory corrective mechanism

A negative feedback to the receptor


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Stimulus

Condition

increases

Receptors

detects it Corrective

mechanism

Condition

decreases

Stimulus

Conditiondecreases

Receptor

detects it

Corrective

mechanism

Condition

rises

Normal

condition


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Organs involved in Homeostasis1. Skin (helps in temperature regulation)

2. Kidneys (helps in the water concentration of

the body)3. Brain (MASTERMIND)

4. Pancreas (produces insulin that helps in the

control of sugar concentration in the blood)


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Regulation of bloodglucose concentration Too much glucose in

blood

Stimulate pancreas to

secrete more insulin Causes the liver to

convert glucose to

glycogen

Blood glucose level drops

Achieved normal blood

glucose level


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Too little glucose in blood

Stimulate pancreas to secrete glucagon

which causes the liver to convert glycogento glucose

Blood glucose level rises

Achieved normal blood glucose level


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What Happens When GlucoseConcentration Rises?14 April 2012


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Stimulus

Blood glucose

concentration rises

above normal levels

14 April 2012Copyright 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 12

What Happens When Glucose Concentration Rises?


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Receptor

Islets of Langerhans

in pancreas stimulated

pancreas

Stimulus

Blood glucose

concentration rises

above normal levels




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Receptor



Corrective Mechanism

Islets of Langerhans secretesmore insulin, which istransported by blood to liverand muscles

pancreas

liver

Stimulus

Blood glucose

concentration rises

above normal levels




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Receptor



Permeability of cellsurface membraneto glucose increases



pancreas

liver

Stimulus

Blood glucose

concentration rises

above normal levels




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Receptor






Liver and musclesconvert excessglucose to glycogen.Glycogen is stored inliver and muscles

pancreas

excess glucose glycogen

liver

Stimulus

Blood glucose

concentration rises

above normal levels




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Receptor







Blood glucoseconcentrationdecreases andinsulin productionfalls

pancreas


liver

Stimulus

Blood glucose

concentration rises

above normal levels




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Receptor








pancreas


liver

Blood glucoseconcentrationreturns to normal

Stimulus

Blood glucose

concentration rises

above normal levels




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Receptor



Stimulus

Blood glucose

concentration rises

above normal levels






Negative feedback



pancreas

liver




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StimulusBlood glucose

concentration falls

below normal levels

What Happens When Glucose Concentration Falls?


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Receptor




concentration falls

below normal levels

pancreas



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concentration falls

below normal levels

pancreas

liver


Islets of Langerhans secretesmore glucagon, which istransported by blood to liverand muscles

Receptor





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Glucagon convertsstored glycogenback to glucose.From liver, glucoseenters bloodstream


concentration falls

below normal levels

pancreas

liver

glycogen glucose



Receptor





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concentration falls

below normal levels

pancreas

liver

glycogen glucoseReceptor





Blood glucoseconcentration risesand glucagonproduction decreases



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concentration falls

below normal levels

pancreas

liver

glycogen glucoseReceptor









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liver

Receptor






Negative feedback


concentration falls

below normal levels





glycogen glucose

pancreas


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Water potentialof blooddecreases

Stimulatepituitary glandto secrete moreADH More waterreabsorbed bykidney tubules,less water isexcreted Urine is moreconcentrated,

less urineproduced Return to normalcondition


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Water potential of blood increases Stimulate pituitary gland tosecrete less ADH Less water reabsorbed by kidneytubules, more water is excreted Urine is more diluted, more urine

produced Return to normal condition


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Learning Objectives

12.2 Structure and function of the skin

(c) Identify on a diagram of the skin: hairs, sweat

glands, temperature receptors, blood vessels and

fatty tissue

(d) Describe the maintenance of a constant body

temperature in humans in terms of insulation and the

role of: temperature receptors in the skin, sweating,shivering, blood vessels near the skin surface and the

co-ordinating role of the brain


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Skin

Largest organ of the human body.

An important sense organ

Barrier between the body and the externalenvironment

Organ that regulates our body temperature.
http://www.brainpop.com/health/integumentary/skin/index.wemlhttp://www.brainpop.com/health/integumentary/skin/index.weml


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Skin


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Epidermis

outer layer of the skin :-a. Cornified layer (dead cells)

Protects the body from water loss, invasion ofmicrobes & mechanical, thermal & chemicaldamage.

b. Granular layer

New cells undergo cell division

c. Malpighian layer

to replace dead cells from the cornified layer

pigmented cells (melanin) protects our skin against

harmful UV light of the sun


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Functions of the Epidermis

1. Layer is water-resistant (waterproof)

2. Prevents evaporation

of water from skin3. Prevents germs from

entrying into the body.

4. Protective layer,preventing mechnicalinjury.


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Dermis

Consists mainly of fibrous tissue and many otherstructures:-

(a) Blood vessels

numerous blood vessels

Arterioles that carry blood are controlled byvasometer nerves.

Nerves bring about contraction & dilation of thearteries.

Arterioles dilate (vasodilation) --> more blood issent to the skin.

Arterioles contract (vasoconstriction) --> less blood

is sent to the skin.


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Dermis

(b) Hair

Common feature of mammals.

Grow inside the hair follicle

At the base of the follicle is a mass of tissue

containing blood capillaries.

Attached to the hair follicles are the hairerector muscles. (contract --> causes the hair

to stand)


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Dermis

(c ) Sweat glands

sweat is secreted in the sweat glands.

Sweat glands ---> sweat duct ---> sweat pore

surface of skin.

Sweat = urea + water + salt (sodium chloride)


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Dermis

(d) Temperature receptors

nerve endings are found in the epidermis and

dermis. Form sense organs

Enable us to sense pain, pressureand

temperature changes in the externalenvironment.


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NERVE

ENDINGS


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Dermis

(e) Fatty Tissue

--> Fat cells are present where fat is stored.


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Dermis

(f) Sebaceous glands

2 glands open into each hair follicle.

Secreting an oily substance (sebum) into hairfollicle.

Sebum lubricates the hair and keeps the skin

soft and smooth. Prevents dehydration of the skin.

Has an antiseptic action.


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Control of body

temperature


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Skin

Able to detect temperature change in the

external environment.

A change in atmospheric temperature -->detected by temperature receptors on the skin

--> start some mechanisms to control the

temperature.


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The Brain

Hypothalamus is the control centre for

temperature.

Detects temperature changes in the blood.


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What happens when temperature rises?

Hypothalamus triggers off the following:-

1. Decreased metabolic rate of the cells, resulting inless heat being produced.

2. Relaxation of skeletal muscles to reduce heatproduction. Causes the hair to lie flat

3. Vasodilation causing arterioles to increase bloodsupply to the skin . More heat can be lost through

the skin.

4. More sweat is produced. As sweat is removedmore latent heat is removed.
http://www.brainpop.com/health/endocrine/homeostasis/index.wemlhttp://www.brainpop.com/health/endocrine/homeostasis/index.weml


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What happens when temperature falls?

(a) Increased metabolic rate, resulting in moreheat being produced.

(b) Shivering due to the contraction of skeletalmuscles. (increases heat production)

(c) Causes hair to stand.

(d) Vasoconstriction causing arterioles in the

skin to constrict.

(e) Blood is diverted from the skin to reduceheat loss.


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Body Temp37 C

Detected by

hypothalamusRise in Blood

Temperature

Heat released

During exerciseHeat loss

Body Temp37 C

Increased sweating

Vasodilation

Cold

environment

Drop in blood

temperature

Blood temp

rises

Decreased sweating

Vasoconstriction

shiveringDetected by

hypothalamus


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Regulating Body Temperature - on a Hot Day

14 April 2012



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Stimulus

Blood and skintemperatures rise

Regulating Body Temperature on a Hot Day



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Stimulus


Receptor

Temperature receptors

detect changes and send

nerve impulses to the brain




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Stimulus


blood capillaries

hair folliclehair

arteriole

erector muscle

Receptor




Hypothalamus of brain

is stimulated and sends

nerve impulses to

relevant body parts




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Stimulus


Receptor






nerve impulses to

relevant body parts

arteriole

capillariesskin surface

Arterioles in

skin dilate

1

More blood flows to

capillaries in skin

2

3

Greater heat loss

4

Shunt vessels constrict




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Stimulus




nerve impulses to

relevant body parts

sweat duct

sweat pore

sweat gland

Sweat glands

more active

Sweat

production

increases

More latent heat lost as sweat evaporates

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7

5


Receptor






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Stimulus


Hair erector

muscles in

skin relax

erector muscle

blood capillaries

hair folliclehair

arteriole

8

Receptor






nerve impulses to

relevant body parts




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Stimulus


Receptor






nerve impulses to

relevant body parts


Increase in heat loss anddecrease in heat

production




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Stimulus


Receptor






nerve impulses to

relevant body parts



production

Decreased

metabolic rate

reduces heatproduction

egu at g ody e pe atu e o a ot ay



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Stimulus


Receptor






nerve impulses to

relevant body parts



production

Blood temperature

returns to normal levels

Decreased

metabolic rate


g g y p y



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Stimulus


Receptor






nerve impulses to

relevant body parts



production

Blood temperature


Negative

feedback

Decreased

metabolic rate


g g y p y


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Regulating Body Temperature - on a Cold Day

14 April 2012



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Stimulus

Blood and skin

temperatures fall

g g y p y



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Stimulus

Blood and skin

temperatures fall

Receptor



nerve impulses to the

brain

g g y p y



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blood capillariesarteriole

hair hair follicle

Stimulus

Blood and skin

temperatures fall

Receptor




brain



nerve impulses to

relevant body parts

erector muscles

g g y p y



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Stimulus

Blood and skin

temperatures fall

Receptor




brain

Less blood flows to

capillaries in skin

Arterioles in

skin constrictShunt vessels dilate

skin surfacecapillaries

arteriole

1

2

3

Less heat loss

4



nerve impulses to

relevant body parts

g g y p y



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Sweat glands

less active

Sweat

production

decreases

Less latent heat lost

sweat pore

sweat duct

sweat gland

Stimulus

Blood and skin

temperatures fall

Receptor




brain



nerve impulses to

relevant body parts

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7

g g y p y



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Hair erector

muscles in

skin contract


erector muscles

blood capillariesarteriole

hair hair follicle

Stimulus

Blood and skin

temperatures fall

Receptor




brain



nerve impulses to

relevant body parts

8



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Shivering occurs when

insufficient heat is produced

Stimulus

Blood and skin

temperatures fall

Receptor




brain


is

stimulated and sends

nerve impulses to

relevant body parts


Decrease in heat loss

and increase in heat

production



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Stimulus

Blood and skin

temperatures fall

Receptor




brain




production

Increased

metabolic rate

increases heatproduction



nerve impulses to

relevant body parts



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Blood temperature


Stimulus

Blood and skin

temperatures fall

Receptor




brain




production

Increased

metabolic rate




nerve impulses to

relevant body parts



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production

Increased

metabolic rate


Blood temperature


Negative

feedback


Stimulus

Blood and skin

temperatures fall

Receptor




brain



nerve impulses to

relevant body parts


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Chapter 12 HomeostasisHomeostasis (Concept Map)14 April 2012


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HOMEOSTASIS

The maintenance of a constant internal environment


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Principles of Homeostasis

HOMEOSTASIS



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Stimulus

Change ininternalenvironment

HOMEOSTASIS




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Stimulus


HOMEOSTASIS



Receptors

Detect thechange


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Stimulus


HOMEOSTASIS



Receptors

Detect thechange

Self-corrective Mechanism

To rectify thechange


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Stimulus


HOMEOSTASIS



Receptors

Detect thechange



Examples

Regulation ofblood glucoseconcentration


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Stimulus


HOMEOSTASIS



Receptors

Detect thechange



Examples


Regulation ofblood waterpotential


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Stimulus


HOMEOSTASIS



Receptors

Detect thechange



Examples



Regulation ofbody temperature

HOMEOSTASIS


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Stimulus Receptors Self-corrective Mechanism Negative Feedback


Detect thechange


Examples



Regulation ofbody temperature

The reverseeffect of thechange

HOMEOSTASIS


chapter 12 homeostasis - copy

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