homeostasis skin & temperature control. learning objectives 12.1 principles of homeostasis a)...
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HomeostasisSkin & Temperature Control
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, a corrective mechanism and a negative feedback
Homeostasis Homeostasis is
defined as the maintenance of a constant internal environment.
Changes in body temperature may result in enzyme inactivation or denaturation.
Any drastic changes in our blood and the surrounding tissues fluid will affect chemical reactions in the tissue cells and will harm the body.
Cells must be bathed in tissue fluid of the correct pH and water potential. Enzyme reaction will be affected.
Negative Feedback Control The internal environment of our bodies
MUST have certain conditions within tolerable limits to continue the healthy functioning.
Done by NEGATIVE FEEDBACK control. Used to control blood sugar concentration,
water concentration & temperature of the blood.
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
StimulusCondition increases
Receptors detects it Corrective
mechanism
Condition decreases
StimulusCondition decreases
Receptor detects it
Correctivemechanism
Condition rises
Normal condition
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)
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
Skin Largest organ of the human body. An important sense organ Barrier between the body and the external
environment Organ that regulates our body temperature.
Skin
Epidermis outer layer of the skin :-a. Cornified layer (dead cells) Protects the body from water loss, invasion of
microbes & mechanical, thermal & chemical damage.
b. Granular layer New cells undergo cell divisionc. Malpighian layer to replace dead cells from the cornified layerpigmented cells (melanin) protects our skin against
harmful UV light of the sun
Functions of the Epidermis
1. Layer is water-resistant (waterproof)
2. Prevents evaporation of water from skin
3. Prevents germs from entrying into the body.
4. Protective layer, preventing mechnical injury.
Dermis Consists mainly of fibrous tissue and many other
structures:-(a) Blood vessels numerous blood vessels Arterioles that carry blood are controlled by vasometer
nerves. Nerves bring about contraction & dilation of the
arteries. Arterioles dilate (vasodilation) --> more blood is sent to
the skin. Arterioles contract (vasoconstriction) --> less blood is
sent to the skin.
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 “hair
erector” muscles. (contract --> causes the hair to stand)
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)
Dermis(d) Temperature receptors nerve endings are found in the epidermis and
dermis. Form sense organs Enable us to sense pain, pressure and
temperature changes in the external environment.
NERVE ENDINGS
Dermis(e) Fatty Tissue
--> Fat cells are present where fat is stored.
Dermis(f) Sebaceous glands 2 glands open into each hair follicle. Secreting an oily substance (sebum) into hair
follicle. Sebum lubricates the hair and keeps the skin
soft and smooth. Prevents dehydration of the skin. Has an antiseptic action.
Control of body temperature
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.
The Brain Hypothalamus is the control centre for
temperature. Detects temperature changes in the blood.
What happens when temperature rises?
Hypothalamus triggers off the following:-1. Decreased metabolic rate of the cells, resulting in
less heat being produced.2. Relaxation of skeletal muscles to reduce heat
production. Causes the hair to lie flat3. Vasodilation causing arterioles to increase blood
supply to the skin . More heat can be lost through the skin.
4. More sweat is produced. As sweat is removed more latent heat is removed.
What happens when temperature falls?
(a) Increased metabolic rate, resulting in more heat being produced.
(b) Shivering due to the contraction of skeletal muscles. (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 reduce
heat loss.
Body Temp 37 C
Detected by hypothalamusRise in Blood
Temperature
Heat releasedDuring exercise
Heat loss
Body Temp 37 C
Increased sweatingVasodilation
Coldenvironment
Drop in bloodtemperature
Blood temprises
Decreased sweatingVasoconstriction
shiveringDetected by
hypothalamus
Regulating Body Temperature - on a Hot Day
April 19, 2023
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 35
Stimulus
Blood and skin temperatures rise
Regulating Body Temperature - on a Hot Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 36
Stimulus
Blood and skin temperatures rise
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Regulating Body Temperature - on a Hot Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 37
Stimulus
Blood and skin temperatures rise
blood capillaries
hair folliclehair
arteriole
erector muscle
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Regulating Body Temperature - on a Hot Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 38
Stimulus
Blood and skin temperatures rise
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends 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
Regulating Body Temperature - on a Hot Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 39
Stimulus
Blood and skin temperatures rise
Hypothalamus of brain is stimulated and sends 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
6
7
5
Regulating Body Temperature - on a Hot Day
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 40
Stimulus
Blood and skin temperatures rise
Hair erector muscles in skin relax
erector muscle
blood capillaries
hair folliclehair
arteriole
8
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Regulating Body Temperature - on a Hot Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 41
Stimulus
Blood and skin temperatures rise
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Corrective Mechanism
Increase in heat loss and decrease in heat production
Regulating Body Temperature - on a Hot Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 42
Stimulus
Blood and skin temperatures rise
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Corrective Mechanism
Increase in heat loss and decrease in heat production
Decreased metabolic rate reduces heat production
Regulating Body Temperature - on a Hot Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 43
Stimulus
Blood and skin temperatures rise
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Corrective Mechanism
Increase in heat loss and decrease in heat production
Blood temperature returns to normal levels
Decreased metabolic rate reduces heat production
Regulating Body Temperature - on a Hot Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 44
Stimulus
Blood and skin temperatures rise
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Corrective Mechanism
Increase in heat loss and decrease in heat production
Blood temperature returns to normal levels
Negativefeedback
Decreased metabolic rate reduces heat production
Regulating Body Temperature - on a Hot Day
Regulating Body Temperature - on a Cold Day
April 19, 2023
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 46
Stimulus
Blood and skin temperatures fall
Regulating Body Temperature - on a Cold Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 47
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Regulating Body Temperature - on a Cold Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 48
blood capillariesarteriole
hair hair follicle
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
erector muscles
Regulating Body Temperature - on a Cold Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 49
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Less blood flows to capillaries in skin
Arterioles in skin constrict
Shunt vessels dilate
skin surfacecapillaries
arteriole
1
2
3
Less heat loss
4
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Regulating Body Temperature - on a Cold Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 50
Sweat glands less active
Sweat production decreases
Less latent heat lost
sweat pore
sweat duct
sweat gland
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
56
7
Regulating Body Temperature - on a Cold Day
Hair erector muscles in skin contract
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 51
erector muscles
blood capillariesarteriole
hair hair follicle
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
8
Regulating Body Temperature - on a Cold Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 52
Shivering occurs when insufficient heat is produced
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is
stimulated and sends nerve impulses to relevant body parts
Corrective Mechanism
Decrease in heat loss and increase in heat production
Regulating Body Temperature - on a Cold Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 53
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Corrective Mechanism
Decrease in heat loss and increase in heat production
Increased metabolic rate increases heat production
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Regulating Body Temperature - on a Cold Day
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 54
Blood temperature returns to normal levels
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Corrective Mechanism
Decrease in heat loss and increase in heat production
Increased metabolic rate increases heat production
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
Regulating Body Temperature - on a Cold Day
Regulating Body Temperature - on a Cold Day
Corrective Mechanism
Decrease in heat loss and increase in heat production
Increased metabolic rate increases heat production
Blood temperature returns to normal levels
Negativefeedback
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 55
Stimulus
Blood and skin temperatures fall
Receptor
Temperature receptors detect changes and send nerve impulses to the brain
Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts
HomeostasisHomeostasis (Concept Map)April 19, 2023
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 57
HOMEOSTASIS
The maintenance of a constant internal environment
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 58
Principles of Homeostasis
HOMEOSTASIS
The maintenance of a constant internal environment
Principles of Homeostasis
Stimulus
Change in internal environment
HOMEOSTASIS
The maintenance of a constant internal environment
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 59
Principles of Homeostasis
Stimulus
Change in internal environment
HOMEOSTASIS
The maintenance of a constant internal environment
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 60
Receptors
Detect the change
Principles of Homeostasis
Stimulus
Change in internal environment
HOMEOSTASIS
The maintenance of a constant internal environment
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 61
Receptors
Detect the change
Self-corrective Mechanism
To rectify the change
Principles of Homeostasis
Stimulus
Change in internal environment
HOMEOSTASIS
The maintenance of a constant internal environment
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 62
Receptors
Detect the change
Self-corrective Mechanism
To rectify the change
Examples
Regulation of blood glucose concentration
Principles of Homeostasis
Stimulus
Change in internal environment
HOMEOSTASIS
The maintenance of a constant internal environment
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 63
Receptors
Detect the change
Self-corrective Mechanism
To rectify the change
Examples
Regulation of blood glucose concentration
Regulation of blood water potential
Principles of Homeostasis
Stimulus
Change in internal environment
HOMEOSTASIS
The maintenance of a constant internal environment
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 64
Receptors
Detect the change
Self-corrective Mechanism
To rectify the change
Examples
Regulation of blood glucose concentration
Regulation of blood water potential
Regulation of body temperature
April 19, 2023Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 65
Principles of Homeostasis
Stimulus Receptors Self-corrective Mechanism Negative Feedback
Change in internal environment
Detect the change
Regulation of blood glucose concentration
Examples
To rectify the change
Regulation of blood water potential
Regulation of body temperature
The reverse effect of the change
HOMEOSTASIS
The maintenance of a constant internal environment