Presentation on theme: "Skin & Temperature Control"— Presentation transcript:
1 Skin & Temperature Control HomeostasisSkin & Temperature Control
2 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
3 HomeostasisHomeostasis is defined as the maintenance of a constant internal environment.
4 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.
5 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.
6 Negative FeedbackA stimulus, which is the change in the internal environmentA receptor that can detect the stimulusA self-regulatory corrective mechanismA negative feedback to the receptor
7 Receptorsdetects itCorrectivemechanismStimulusConditionincreasesNormalconditionConditiondecreasesConditionrisesStimulusConditiondecreasesCorrectivemechanismReceptordetects it
8 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)
9 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
10 Skin Largest organ of the human body. An important sense organ Barrier between the body and the external environmentOrgan that regulates our body temperature.
13 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 divisionc. Malpighian layerto replace dead cells from the cornified layerpigmented cells (melanin) protects our skin against harmful UV light of the sun
14 Functions of the Epidermis Layer is water-resistant (waterproof)Prevents evaporation of water from skinPrevents germs from entrying into the body.Protective layer, preventing mechnical injury.
16 Dermis Consists mainly of fibrous tissue and many other structures:- Blood vesselsnumerous blood vesselsArterioles 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.
17 Dermis (b) Hair Common feature of mammals. Grow inside the hair follicleAt 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)
24 Dermis (e) Fatty Tissue --> Fat cells are present where fat is stored.
25 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.
28 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.
29 The Brain Hypothalamus is the control centre for temperature. Detects temperature changes in the blood.
30 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 flatVasodilation 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.
32 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.
33 Detected byhypothalamusIncreased sweatingVasodilationRise in BloodTemperatureHeat lossHeat releasedDuring exerciseBody Temp37 CBody Temp37 CColdenvironmentBlood temprisesDrop in bloodtemperatureDecreased sweatingVasoconstrictionshiveringDetected byhypothalamus
34 Regulating Body Temperature - on a Hot Day 21 April 2017Figure 12.7 (modified) page 246, Figure 12.8 (modified) page 246 and Figure 12.9 page 248