Homeostasis

Question 1

Homeostasis

Answer 1

the maintenance of a constant internal environment

Question 2

homeostasis is the control of internal conditions within set limits

Answer 2

Allows the environment to be at a constant for cells to function. internal conditions must be maintained within set limits, if these limits are exceeded, Negative feedback mechanisms work to correct the change and restore internal environment to optimum temperature.

Question 3

concept of control by negative feedback

Answer 3

internal conditions must be maintained within set limits, if these limits are exceeded, Negative feedback mechanisms work to correct the change and restore internal environment to optimum temperature.

Question 4

control of the glucose concentration of the blood by the liver and the roles of insulin and glucagon from the pancreas

Answer 4

Insulin and glucagon are synthesized in the cells of pancreas.

• Insulin: When blood glucose concentration is too high , detected by pancreas and secretes insulin. Liver cells use some glucose in respiration and store some glucose as glycogen. Thus blood glucose concentration falls.
• Glucagon: When blood glucose concentration Is too low, Glucagon is secreted, liver breaks down glycogen into glucose, glucose is released from the liver into the blood and blood glucose concentration rises.

Question 5

symptoms and treatment of type 1 diabetes

Answer 5

People with diabetes cannot produce insulin. Type 1 diabetes is caused by autoimmune response, in which antibodies attack cells in pancreas which usually make insulin. Thus no insulin can be produced. . Type 1 diabetes is treated by patients injecting insulin into them. stem cells and artificial pancreas are also treatments however are expensive.
-Symptoms: increased thirst, increased urination, and increased hunger.

Question 6

Name and identify on a diagram of the skin: hairs, hair erector muscles, sweat glands, receptors, sensory neurones, blood vessels and fatty tissue

Answer 6

…

Question 7

The maintenance of a constant internal body temperature in humans in terms of insulation, sweating, shivering and the role of the brain (limited to blood temperature receptors and coordination)

Answer 7

It is important to maintain constant temperature 37 degrees C. As is optimum temperature for enzyme reaction, If temperature was lower, rate of reaction would decrease. If too high, enzymes would denature, preventing reactions from occurring. Temperature is regulated by the Hypothalamus, which contains thermoreceptors. If temperature moves away from optimum, response is triggered to return temperature back to optimum.

When the temperature rises, the hypothalamus stimulates:

• Hair to lie flat – the hair erector muscle is relaxed, allowing the hair to lie flat against the skin, so no air is trapped close to the skin, so we are insulated less. This is less effective in humans as we do not have as much body hair/ fur as some animals.
• Vasodilation – the muscles in the walls of the arterioles supplying skin-surface capillaries relax, increasing the size of the arteriole lumen. More blood flows, so more heat can be lost to the environment from the blood at a time.
• Sweating – sweat is secreted by sweat glands. It evaporates, taking heat from the skin with it, causing the body to cool down.
• Metabolism slows down – metabolism usually consists of exothermic reactions (reactions that give off heat energy) so slower metabolism means less heat is given off at a time.

When the temperature falls, the hypothalamus stimulates:

• Hair to stand erect – the erector muscle contracts, pulling the hair to stand up straight. This allows the hair to trap air close to the skin. As air is an insulator, it traps heat close to the skin, warming up the body.
• Vasoconstriction – muscles in arteriole walls contract, making the lumen smaller, so less blood travels through the skin at a time, reducing the heat loss per unit time.
• Reduces sweating – so less sweat evaporates, making the body cool down less.
• Metabolism may increase.
• Shivering – muscles in some part of the body involuntarily contract and relax very quickly, producing heat as a result.

Question 8

the maintenance of a constant internal body temperature in humans in terms of vasodilation and vasoconstriction of arterioles supplying skin surface capillaries

Answer 8

Reaction to low internal temperature:
-Shivering: Muscles contract to produce heat
-Vasoconstriction: Blood vessels constrict to reduce surface area and move away from surface of the skin to reduce heat loss.
Reaction to high internal temperature:
-Sweating: Sweat evaporates from the surface of the skin, reducing surface temperature.
-Vasodilation: Blood vessel dilate, causing more heat loss to the environment.