chapter 12 homeostasis - lecture notes
TRANSCRIPT
Chapter 12: Homeostasis
Students should be able to:
1. Define homeostasis.2. Identify and name the hairs, sweat glands and blood vessels of the
skin.3. Describe the maintenance of a constant body temperature in Man
by(a) Temperature receptors in the skin.(b) Sweating and shivering.(c) Blood vessels near the skin.(d) Coordinating role of the brain.
4. State the nervous system – brain, spinal cord and nerves.5. Describe how the 3 parts of the nervous system serve to
coordinate/regulate bodily functions.
12.1 Homeostasis
12.1.1 Definition Maintenance of a constant internal environment (steady state) in
the mammalian body Derived from Greek: (homoio = same, stasis= standstill)
12.1.2 Negative feedback control External Environment Temperature
o As external temperature changes body internal temp ____o When in hot sun, our body tends to get _______o When in the cold, our body tends to get ________
Mammalianso So-called “warm-blooded” because…o Can maintain a _________ body temperature
Analogy with air-conditioning systemso When we first switch on the air-con, the fans will turn at its
maximum speed, cooling the place ________o However, as the temperature reaches its programmed level,
the thermostat causes fans to automatically _____ its speed o When temp reaches its programmed level, the fans ______
____o When temp starts to increase as more people fill the room,
the fans will start to _______ ___ againo A similar “system” is present in the body of mammals
such systems work under the “Negative Feedback Control”
12.2 The Mammalian Skin
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12.2.1 Structure
12.3 Functions of the components of the Mammalian Skin
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12.3.1 Temperature Receptors in the Skin Nerve endings found in epidermis & the dermis Form receptors
o Function: Sense pain, pressure or temperature changes in the external environment
o For example: Touch receptors gives us a sensation of pain Temperature Receptors: Gives us a sensation of temperature
changes in the surroundings
12.3.2 Sweating & Shivering
12.3.3 Blood Vessels near the skinVasoconstriction Vasodilation
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Arterioles in the skin dilate (becomes wider)More blood flow through skin
Sweat glands become active produce more sweatMore sweat evaporates from the skin surface remove latent heatBreathing becomes more rapid help remove heat
Metabolic process of body slows down less heat is produced
Arterioles in the skin constrict (becomes smaller)Less blood flow through skin
Sweat glands become less active produce less / no sweatMetabolic process of body speed up more heat is producedHair erector muscles contracts still air trapped between hairs (goose pimples)Body muscles contract Shivering
Increase heat production
Help raise body temp to normal
12.3.4 Coordinating Role of the brain
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