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HOMEOSTASIS

HOMEOSTASIS. Maintenance of a constant internal environment Importance Enzyme reactions have a narrow optimum temperature and pH range. Fluctuation of Water potential of blood and tissue fluids affects the function of cells. Examples of Homeostasis in Humans.

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HOMEOSTASIS

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  1. HOMEOSTASIS • Maintenance of a constant internal environment Importance • Enzyme reactions have a narrow optimum temperature and pH range. • Fluctuation of Water potential of blood and tissue fluids affects the function of cells.

  2. Examples of Homeostasis in Humans • Regulating water potential of blood • Regulating blood glucose concentration • Temperature regulation.

  3. CONTROL SYSTEM • SET POINT -the desired level at which the system operates. This is monitored by a • RECEPTOR -that detects any deviation from the set point and informs the • CONTROLLER -that coordinates information from various sources and send instructions to an appropriate • EFFECTOR -that brings about necessary change needed to return system to the set point. • FEEDBACK LOOP -that informs the receptor of the changes to the system brought about by the effector.

  4. Receptor to detect stimulus Self-regulatory /automatic A corrective process to restore the normal condition A corrective process to restore the normal condition

  5. Blood vessels (capillaries & arterioles in the dermis) • Arterioles bring blood to capillaries • Arterioles controlled by nerves • Vasodilation  more blood sent to capillaries in skin • Heat from skin is lost by radiation and convection • Shunt vessels

  6. When shunt vessels constrict, more blood sent to skin surface. When shunt vessels dilate

  7. SWEAT GLANDS • Coiled tubes made up of cells which absorb fluid from surrounding capillaries and secrete into the tube. • The fluid (sweat) passes to skin surface via sweat duct • Sweat consists of mainly water, mineral salts and urea. • When the water evaporates, it removes latent heat

  8. Sensory receptors • Sensory cells that detect changes in the environment (stimuli). • These sensory cells or receptors are connected to sensory neurones (nerve cells) • Eg. touch receptors, temperature receptors, pain receptors, pressure receptors.

  9. Adipose tissue • A layer of cells where fat is stored. • The fats in the cells act as both long-term food reserve and also as an insulating layer.

  10. TEMPERATURE REGULATION • GAIN HEAT -metabolic activities, eg. respiration -eating hot food -by exercising -sun’s radiation on very hot days • HEAT LOSS -through skin by radiation, convection -evaporation of water in sweat -heat loss in exhaled air

  11. WARM ENVIRONMENT • Vasodilation • Sweating

  12. COLD ENVIRONMENT • Vasoconstriction • Shivering • Insulation • Increased metabolic rate (1. liver increases its metabolic rate) (2. low temperature induce increased activity of adrenal, thyroid and pituitary glands. Hormones from these glands help to increase metabolic rate and so produce additional heat....This requires increased consumption of food.

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