7 2 homeostasis

Homeostasis is the maintenance of a constant internal environment within set limits.

Homeostasis is important because it maintains optimal conditions for enzyme action and cell function.

In the human body, homeostasis regulates:

Thermoregulation ensures that the temperature inside the body remains optimal for enzyme activity.

Structures A-D are:

Thermoregulation mechanisms that occur in the dermis include:

Thermoregulation mechanisms that occur in the epidermis include:

The hypothalamus contains the thermoregulatory centre which monitors and controls body temperature.

Shivering aids temperature regulation because the rapid muscle contractions generate heat through respiration; this helps to raise the core body temperature.

Vasodilation is a cooling mechanism in which the diameter of skin arterioles increases. This increases blood flow to capillaries in the skin surface, transferring heat to the environment by radiation.

An increase in body temperature causes the arterioles that supply the skin capillaries to dilate; this increases blood flow to the skin surfaces and increases heat loss.

True. Exercise raises core body temperature due to increased metabolic activity in the contracting muscles. Sweating and vasodilation occur as part of the temperature regulation mechanisms of the skin.

True. Vasoconstriction is a heat retention mechanism. The diameter of skin arterioles decreases to reduce blood flow to capillaries in the surface of the skin. This minimises heat loss by radiation.

False. Capillaries do not have a muscle layer and therefore cannot constrict. Constriction occurs in the arterioles that supply the skin capillaries, reducing blood flow to the skin surface.

Osmoregulation is the maintenance of the balance of water and salts within the body.

Osmoregulation is important because it ensures that cells do not gain or lose water by osmosis.

Loss of water by osmosis can impact cells as follows:

True. If osmoregulation does not occur and the water concentration of the body fluids increases then cells may take on water by osmosis; in animal cells this can result in cell lysis (bursting).

The organ system responsible for the filtration of blood and the production of urine is the urinary system.

The four main structures of the urinary system are:

The tubes that connect the kidneys to the bladder are the ureters.

ADH affects the permeability of the kidney tubules to water:

True. More ADH makes the walls of the collecting duct more permeable to water. This means that more water is reabsorbed into the blood and urine is more concentrated.

The following mechanisms occur to produce dilute urine:

Kidney failure is a condition where the kidneys do not function properly, leading to a build-up of toxic waste in the body which can be fatal if not treated.

Dialysis is a treatment for kidney failure where a machine acts as an artificial kidney, removing most of the urea and maintaining the water and salt balance in the blood.

A kidney transplant is a surgical procedure where a healthy kidney from a donor is implanted into a patient with kidney failure, offering a long-term solution compared to dialysis.

Advantages of a kidney transplant over dialysis are that it provides:

Disadvantages of kidney transplants include:

False. Urea is produced from the breakdown of excess amino acids in the liver.

The pancreas is the gland that produces hormones in response to changing blood glucose levels.

False. Insulin reduces blood glucose levels by increasing the uptake of glucose from the blood into the body cells, where it is converted into glycogen.

In liver and muscle cells excess glucose is converted into glycogen for storage.

When blood glucose concentration is too low the pancreas produces the hormone glucagon.

The hormone glucagon is produced when the blood glucose concentration is too low. It causes glycogen to be converted into glucose and released into the blood.

Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin to control blood glucose levels.

Type 2 diabetes is a disorder where the body cells no longer respond to insulin produced by the pancreas.

A carbohydrate-controlled diet and an exercise regime are common treatments for Type 2 diabetes.

Obesity is a major risk factor for Type 2 diabetes.

Type 1 diabetes is controlled by insulin injections.

Obese individuals have an increased risk of developing Type 2 diabetes compared to non-obese individuals. An individual with a BMI over 30 has an increased risk of developing Type 2 diabetes.

Individuals with a lot of excess fat stored around the abdomen area have an increased risk of developing Type 2 diabetes. A waste:hip ratio above 1.0 for men and 0.85 for women is associated with an increased risk of developing Type 2 diabetes.