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Homeostasis

Terms in this set (17)

Define homeostasis
Maintainence of a constant internal environment
State the importance of thermoregulation.
Enzymes require optimal temperatures to function efficiently.
Low temperatures cause enzymes to be inactive while high temperatures denature enzymes.
State the importance of blood glucose regulation.
Glucose molecules affect water potential of plasma and tissue fluid.
Since glucose is a respiratory substrate, a reduced concentration would impair respiration.
State the importance of osmoregulation.
Water potential of plasma and tissue fluid is affected.
Cells may burst or become crenated.
List the general homeostasis process.
1) A stimulus causes a change in internal environment.
2) Receptors detect this change
3) Body will respond with corrective mechanism to reverse the direction of this change.
4) Internal environment is returned to the set point/norm.
List the main functions of the skin.
1) Mechanical protection (epidermis)
- Barrier to prevent the entry of bacteria into the body
- Separates internal body from environment

2) Thermoregulation (dermis)
- Enables human body temperature to remain close to the set point of 37C
State the function of sweat glands.
Secrete sweat onto the surface of the skin, which evaporates and removes latent heat of vaporisation, cooling the body down.
State the function of temperature receptors (aka thermoreceptors)
Detect temperature of the surrounding skin, generate nerve impulses to be sent to the nervous system.
State the function of blood vessels.
Arterioles or venules located in the subcutaneous layer or fatty layer of the skin. They are capable of vasoconstriction and vasodilation to control the amount of blood flowing through the capillaries near the surface of the skin.
State the function of fatty tissue.
(Not part of the skin) - Provides insulation and padding for the body
[Homeostasis process] Describe what happens when temperature rises above the norm.
1) High air temperature or exercise causes body temperature to rise above the norm.
2) Higher temperature in blood is detected by the hypothalamus (internal body temperature) and temperature receptors in the skin (temperature of surroundings).
3) Nerve impulses are sent by the hypothalamus to a number of effectors.
4) Vasodilation of arterioles causes increased blood flow through capillaries near the skin surface, resulting in more heat loss via conduction, convection and radiation.
5) Sweat glands become more active, secreting more sweat to the skin surface. More sweat evaporates, thus more latent heat of vaporisation is removed, resulting in more heat loss.
6) Decreased metabolic activity.
7) Body temperature falls towards 37C.
[Homeostasis process] Describe what happens when temperature falls below the norm.
1) Low air temperature or drinking cold drink causes body temperature to fall below the norm.
2) Lower temperature in blood is detected by hypothalamus (internal body temperature) and temperature receptors (temperature of surroundings)
3) Nerve impulses are sent by the hypothalamus to a number of effectors.
4) Vasoconstriction of arterioles results in decreased blood flow through the capillaries near the surface of the skin, reducing heat loss via conduction, convection and radiation.
5) Sweat glands become less active. Less sweat secreted to the surface of the skin, less sweat evaporates, less latent heat of vaporisation removed, less heat loss.
6) Shivering. The involuntary muscle contraction releases heat.
7) Increased metabolic activity.
8) Body temperature rises towards 37C.
[Homeostasis process] Describe what happens when blood glucose concentration rises above the norm.
1) Eating a meal high in carbohydrates causes an increase in blood glucose concentration (due to the digestion and absorption of carbohydrates)
2) High blood glucose concentration is detected by the pancreas.
3) Beta cells of the Islets of Langerhans of the pancreas release insulin into the bloodstream. Insulin travels in blood to target organs.
4) Liver and muscle (target organs) respond to insulin.
- Liver and muscle cells have higher membrane permeability to increase uptake of glucose into cells via facilitated diffusion.
- Insulin activates the enzyme which speeds up the conversion of glucose into glycogen within those cells.
- Thus cells absorb and remove glucose from the blood.
5) Therefore, blood glucose concentration falls towards the norm.
[Homeostasis process] Describe what happens when blood glucose concentration falls below the norm.
1) Using up glucose (fasting, exercise) causes a lower blood glucose concentration than norm.
2) Lower blood glucose concentration is detected by the pancreas.
3) Alpha-cells of the Islets of Langerhans in the pancreas release glucagon into the bloodstream. Glucagon travels in blood towards target organs.
4) Liver (target organ) responds to glucagon.
- Glucagon activates the enzyme which converts glycogen into glucose within liver cells. Thus, liver cells release glucose into the blood.
5) Blood glucose concentration rises towards the norm.
State the role of the hypothalamus and pituitary gland in ADH.
The hypothalamus produces ADH (anti-diuretic hormone), which is stored and released by the pituitary gland.
[Homeostasis process] Describe what happens when blood has a more negative water potential than the norm.
1) Sweating, vigorous exercise, not drinking enough water can cause blood to have a more negative water potential than the norm.
2) More negative water potential in blood is detected by hypothalamus of the brain.
3) Pituitary gland releases more ADH into the bloodstream. ADH travels in blood to target organ (kidney/wall of the collecting duct)
4) With more ADH, there is increased permeability of the wall of the collecting duct to water molecules. More water is reabsorbed, thus urine has a lower content and less water is lost in urine.
5) Water potential of blood rises to the norm.
[Homeostasis process] Describe what happens when blood has a less negative water potential than the norm.
1) Drinking a lot of water causes blood to have a less negative water potential than the norm.
2) Less negative water potential of blood is detected by the hypothalamus of the brain.
3) Pituitary gland releases less ADH in the bloodstream. ADH travels in blood to target organ (kidney/wall of the collecting duct).
4) With less ADH, there is decreased permeability of the walls of the collecting duct to water molecules. Less water is reabsorbed, so urine has a higher water content and more water is lost in urine.
5) Water potential of blood falls towards the norm.
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