Skin & Temperature Control Homeostasis Skin & Temperature Control

Learning Objectives 12.1 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.

The Need for Homeostasis 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

Receptors detects it Corrective mechanism Stimulus Condition increases Normal condition Condition decreases Condition rises Stimulus Condition decreases Corrective mechanism Receptor detects it

Organs involved in Homeostasis Skin (helps in temperature regulation) Kidneys (helps in the water concentration of the body) Brain (MASTERMIND) 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 :- Cornified layer (dead cells)  Protects the body from water loss, invasion of microbes & mechanical, thermal & chemical damage. 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

Functions of the Epidermis Layer is water-resistant (waterproof) Prevents evaporation of water from skin Prevents germs from entrying into the body. Protective layer, preventing mechnical injury.

Dermis Consists mainly of fibrous tissue and many other structures:- 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:- Decreased metabolic rate of the cells, resulting in less heat being produced. Relaxation of skeletal muscles to reduce heat production. Causes the hair to lie flat Vasodilation causing arterioles to increase blood supply to the skin . More heat can be lost through the skin. More sweat is produced. As sweat is removed more latent heat is removed.

What happens when temperature falls? Increased metabolic rate, resulting in more heat being produced. Shivering due to the contraction of skeletal muscles. (increases heat production) Causes hair to stand. Vasoconstriction causing arterioles in the skin to constrict. Blood is diverted from the skin to reduce heat loss.

Detected by hypothalamus Increased sweating Vasodilation Rise in Blood Temperature Heat loss Heat released During exercise Body Temp 37 C Body Temp 37 C Cold environment Blood temp rises Drop in blood temperature Decreased sweating Vasoconstriction shivering Detected by hypothalamus

Regulating Body Temperature - on a Hot Day 21 April 2017 Figure 12.7 (modified) page 246, Figure 12.8 (modified) page 246 and Figure 12.9 page 248

Regulating Body Temperature - on a Hot Day Stimulus Blood and skin temperatures rise Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 35

Regulating Body Temperature - on a Hot Day Stimulus Blood and skin temperatures rise Receptor Temperature receptors detect changes and send nerve impulses to the brain Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 36

Regulating Body Temperature - on a Hot Day hair follicle hair arteriole blood capillaries Stimulus Blood and skin temperatures rise erector muscle Figure 12.7 (modified) page 246 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 37

Regulating Body Temperature - on a Hot Day 4 Greater heat loss skin surface Stimulus Blood and skin temperatures rise capillaries 1 Arterioles in skin dilate 3 Shunt vessels constrict Figure 12.9 page 248 arteriole Receptor Temperature receptors detect changes and send nerve impulses to the brain 2 Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts More blood flows to capillaries in skin Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 38

Regulating Body Temperature - on a Hot Day 7 More latent heat lost as sweat evaporates sweat pore Stimulus Blood and skin temperatures rise sweat duct 6 Sweat production increases 5 Sweat glands more active Figure 12.8 (modified) page 246 sweat gland 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 39

Regulating Body Temperature - on a Hot Day hair follicle hair arteriole blood capillaries 8 Hair erector muscles in skin relax Stimulus Blood and skin temperatures rise erector muscle Figure 12.7 (modified) page 246 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 40

Regulating Body Temperature - on a Hot Day Stimulus Blood and skin temperatures rise Corrective Mechanism Increase in heat loss and decrease in heat production 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 41

Regulating Body Temperature - on a Hot Day Decreased metabolic rate reduces heat production Stimulus Blood and skin temperatures rise Corrective Mechanism Increase in heat loss and decrease in heat production 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 42

Regulating Body Temperature - on a Hot Day Decreased metabolic rate reduces heat production Blood temperature returns to normal levels Stimulus Blood and skin temperatures rise Corrective Mechanism Increase in heat loss and decrease in heat production 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 43

Regulating Body Temperature - on a Hot Day Decreased metabolic rate reduces heat production Blood temperature returns to normal levels Stimulus Blood and skin temperatures rise Corrective Mechanism Increase in heat loss and decrease in heat production Negative feedback 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 44

Regulating Body Temperature - on a Cold Day 21 April 2017 Figure 12.7 page 246, Figure 12.8 page 246 and Figure 12.10 page 249

Regulating Body Temperature - on a Cold Day Stimulus Blood and skin temperatures fall Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 46

Regulating Body Temperature - on a Cold Day Stimulus Blood and skin temperatures fall Receptor Temperature receptors detect changes and send nerve impulses to the brain Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 47

Regulating Body Temperature - on a Cold Day hair follicle hair arteriole blood capillaries Stimulus Blood and skin temperatures fall erector muscles Figure 12.7 page 246 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 48

Regulating Body Temperature - on a Cold Day 4 Less heat loss Stimulus Blood and skin temperatures fall skin surface capillaries 1 3 Arterioles in skin constrict Shunt vessels dilate Figure 12.10 page 249 arteriole Receptor Temperature receptors detect changes and send nerve impulses to the brain 2 Hypothalamus of brain is stimulated and sends nerve impulses to relevant body parts Less blood flows to capillaries in skin Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 49

Regulating Body Temperature - on a Cold Day 7 Less latent heat lost sweat pore Stimulus Blood and skin temperatures fall sweat duct 6 Sweat production decreases 5 Sweat glands less active Figure 12.8 page 246 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 sweat gland Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 50

Regulating Body Temperature - on a Cold Day hair follicle hair arteriole blood capillaries Stimulus Blood and skin temperatures fall 8 Hair erector muscles in skin contract erector muscles Figure 12.7 page 246 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 51

Regulating Body Temperature - on a Cold Day Shivering occurs when insufficient heat is produced Stimulus Blood and skin temperatures fall Corrective Mechanism Decrease in heat loss and increase in heat production 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 52

Regulating Body Temperature - on a Cold Day Increased metabolic rate increases heat production Stimulus Blood and skin temperatures fall Corrective Mechanism Decrease in heat loss and increase in heat production 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 53

Regulating Body Temperature - on a Cold Day Increased metabolic rate increases heat production Blood temperature returns to normal levels Stimulus Blood and skin temperatures fall Corrective Mechanism Decrease in heat loss and increase in heat production 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 54

Regulating Body Temperature - on a Cold Day Increased metabolic rate increases heat production Blood temperature returns to normal levels Stimulus Blood and skin temperatures fall Corrective Mechanism Decrease in heat loss and increase in heat production Negative feedback 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 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 55

Homeostasis (Concept Map) 21 April 2017 Concept Map page 251

HOMEOSTASIS The maintenance of a constant internal environment Concept Map page 251 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 57

Principles of Homeostasis The maintenance of a constant internal environment Principles of Homeostasis Concept Map page 251 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 58

Principles of Homeostasis The maintenance of a constant internal environment Principles of Homeostasis Stimulus Change in internal environment Concept Map page 251 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 59

Principles of Homeostasis The maintenance of a constant internal environment Principles of Homeostasis Stimulus Receptors Change in internal environment Detect the change Concept Map page 251 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 60

Principles of Homeostasis Self-corrective Mechanism The maintenance of a constant internal environment Principles of Homeostasis Stimulus Receptors Self-corrective Mechanism Change in internal environment Detect the change To rectify the change Concept Map page 251 Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 61

Principles of Homeostasis Self-corrective Mechanism The maintenance of a constant internal environment Principles of Homeostasis Stimulus Receptors Self-corrective Mechanism Change in internal environment Detect the change To rectify the change Examples Concept Map page 251 Regulation of blood glucose concentration Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 62

Principles of Homeostasis Self-corrective Mechanism The maintenance of a constant internal environment Principles of Homeostasis Stimulus Receptors Self-corrective Mechanism Change in internal environment Detect the change To rectify the change Examples Concept Map page 251 Regulation of blood glucose concentration Regulation of blood water potential Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 63

Principles of Homeostasis Self-corrective Mechanism The maintenance of a constant internal environment Principles of Homeostasis Stimulus Receptors Self-corrective Mechanism Change in internal environment Detect the change To rectify the change Examples Concept Map page 251 Regulation of blood glucose concentration Regulation of blood water potential Regulation of body temperature Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 64

Principles of Homeostasis Self-corrective Mechanism The maintenance of a constant internal environment Principles of Homeostasis Stimulus Receptors Self-corrective Mechanism Negative Feedback Change in internal environment Detect the change To rectify the change The reverse effect of the change Examples Concept Map page 251 Regulation of blood glucose concentration Regulation of blood water potential Regulation of body temperature Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd. 21 April 2017 65