Homeostasis in humans

• Vasodilation is a response to being too hot.
• Vasoconstriction is a response to being too cold.
• Skin hairs lie flat when we are hot and stand upright when we are cold.
• The amount of blood flowing through the skin capillaries is altered by vasoconstriction and vasodilation.
• When the temperature is too high, different processes happen: Vasodilation, sweat production, which both transfer energy from skin to the environment, resulting in a cooling effect.
• Negative feedback in temperature regulation regulates the amount of shivering, which is caused by rapid muscle contractions that release heat.
• When the body temperature is too low, a variety of processes happen: vasoconstriction, sweating stops and shivering starts.
• Negative feedback in temperature regulation also regulates the amount of sweating, which is caused by the evaporation of water in sweat, resulting in cooling.
• The control of body temperature is an example of a negative feedback mechanism.
• Glands often release a hormone, which would restore the optimum condition again.
• The thermoregulatory centre, which is contained in the hypothalamus in the brain, controls the process of maintaining body temperature.
• Blood vessels, which lead to the skin capillaries, become narrower - they constrict - which allows less blood to flow through the skin and conserve the core body temperature.
• The hairs on the skin also help to control body temperature, lying flat when we are warm, and rising when we are cold.
• The skin also has temperature receptors and sends nervous impulses back to the thermoregulatory centre.
• Effectors are the organs, tissues or cells that produce a response, such as muscles or glands.
• Coordination centres in the brain, spinal cord and pancreas receive information from the receptors, process the information and instigate a response.
• If we are too cold, nerve impulses are sent to the hair erector muscles which contract, raising the skin hairs and trapping a layer of insulating air next to the skin.
• Body temperature is one of the factors that are controlled during homeostasis.
• When we get too cold, skeletal muscles contract, causing us to shiver, which requires energy from respiration.
• When we get too hot, sweat glands in the skin release more sweat, which evaporates, transferring heat energy from the skin to the environment.
• Blood vessels leading to the skin capillaries become wider - they dilate - allowing more blood to flow through the skin, and more heat to be lost to the environment.
• Enzymes work best at a temperature of around 37°C.
• Homeostasis is the regulation of internal conditions inside cells or organisms, to create the optimum conditions for biological function.
• Body temperature and the thermoregulatory centre are important in homeostasis.
• Maintaining nitrogen balance in the body is crucial in homeostasis.
• Water content is a crucial aspect of homeostasis.
• Osmoregulation is the control of water levels and mineral salts in the blood.
• Water levels and mineral salts in the blood are controlled to protect cells by stopping too much water from entering or leaving them, as the concentrations of water and salts is the same inside and outside the cells.
• If body cells lose or gain too much water by osmosis, they do not function efficiently.
• If the concentration of water is the same inside and out the cells, they remain in their normal state.
• If the water concentration is too high outside, water enters the cell by osmosis.
• The movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration is known as osmosis.
• Plants also undergo the process of osmosis, in the same way that animal cells do.
• Having turgor is the description of a plant cell in which the vacuole has swollen due to water gain by osmosis.
• If the water concentration is too low outside compared to the inside of the cells, water will leave by osmosis and the cells may shrivel.
• The organs of excretion in humans include the skin, lungs and kidneys.
• We cannot control the level of water, ion or urea loss by the lungs or skin.
• In a hot climate, your body sweats to help keep you cool.
• If cell walls lose water, they become flaccid and the cytoplasm shrinks away from the cell wall.
• Cells are firm, when they are full of water.