Biology: Topic 2J Coordination and Response (Part 1A The Skin) + Hormones

Why is homeostasis important?

To maintain optimal conditions for cell function and enzyme activity.

What type of action is thermoregulation?

Involuntary action.

What is the process of thermoregulation?

Controlled by the thermoregulatory centre (TRC), which is contained in the hypothalamus region in the brain.

TRC contains thermoreceptors, which are receptors sensitive to the temperature of blood. Thermoreceptors are found in skin and brain.

Mechanism of increasing heat loss - What is sweating?

Sweat is secreted by sweat glands.

Sweat evaporates, transferring heat energy from skin to the surroundings

Mechanism of increasing heat loss - What is vasodilation?

Muscles in arterioles relax.

Arterioles near skin surface dilates

Blood flow in skin capillaries increases. → More heat is lost to surroundings through radiation.

Mechanism of increasing heat loss - What is flattening of hairs?

The hair erector muscles in skin relax.

Hairs lie flat - stops hair from trapping air which is a poor conductor of heat.

→ MORE heat is lost to surroundings through radiation.

Mechanism to decrease heat loss - What is shivering?

Skeletal muscles contract rapidly in. controlled manner.

MORE heat energy is released from respiration.

Mechanism to decrease heat loss - What is Vasoconstriction?

Muscles in arterioles contract.

Arterioles near skin surface constricts.

Blood flow in skin capillaries decreases → LESS heat is lost to surroundings through radiation.

Mechanism to decrease heat loss - What is erection of hairs?

Hair erector muscles in skin contract.

Hairs stand upright or become erect. - Traps layer of air, which is a poor conductor of heat between hairs.

→ LESS heat is lost to the surroundings through radiation.

What is a hormone?

a chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs

What is the source and function of adrenaline hormone?

source is adrenal gland.

known as the 'fight or flight' hormone as it is produced in situations where the body may be in danger

What is the effects of the adrenaline hormone?

Increased heart and breathing rate - delivers glucose and oxygen to muscle cells faster and removes carbon dioxide more efficiently

Redirects blood flow to muscles and away from non-essential organs. ensures muscles receive more oxygen (and glucose) for respiration

Dilation of blood vessels in muscles – allows more blood (and therefore glucose and oxygen) to reach active muscles

Breaking down of stored glycogen to glucose in the liver and muscle cells, with glucose released by the liver being transported to active muscle cells, which can be used in respiration by muscle cells

What is the function and source of the insulin hormone?

To regulate level of glucose in the blood. source is pancrease

What happens if levels of glucose are too high/too low?

Too high can lead to cells of the body losing water by osmosis

Too low can lead to the brain receiving insufficient glucose for respiration, potentially leading to a coma or even death

How does the pancreas and liver work to control a high level of blood glucose?

Cells in the pancreas detect the increased blood glucose levels

The pancreas produces and secretes insulin into the blood

Insulin stimulates muscles and the liver to take up glucose from the bloodstream and store it as glycogen

This reduces the concentration of glucose in the blood back to normal levels, at which point the pancreas stops secreting insulin

What is testosterones function and source?

stimulating the development of male reproductive organs and the development of secondary sexual characteristics in males

source is testes

What is progesterone function and source?

maintaining the uterine lining during pregnancy and prevents further ovulation

source is ovaries

What is oestrogens function and source?

The development of secondary sexual characteristics in females

Regulating the menstrual cycle by stimulating the repair of the lining of the uterus after menstruation and helps control the release of eggs (ovulation).

source is ovaries