Co-ordination and control

Reflex arc

Hormonal responseInternal conditions which need to be controlled:• Water• Ion• Temperature• Sugar

Hormones are chemicals; 1. Regulate functions of organs and cells2. Coordinate body processes3. Are secreted by glands into the blood stream4. Travel in the blood stream to target organs.

Control Internal conditions that are controlled include:

■ the water content of the body – water leaves the body via the lungs when we breathe out and via the skin when we sweat to cool us down, and excess water is lost via the kidneys in the urine

■ the ion content of the body – ions are lost via the skin when we sweat and excess ions are lost via the kidneys in the urine

■ temperature – to maintain the temperature at which enzymes work best

■ blood sugar levels – to provide the cells with a constant supply of energy.

Plant responsePhototropism: Plants grow towards light

Geotropism: response of plants to gravity. E.g. roots grow downwards.

Menstrual CycleSeveral hormone co-ordinate the menstrual cycle:1. Follicle stimulating hormone (FSH) produce by the

pituitary gland job cause eggs in the ovary to mature and stimulates the production of oestrogen.

2. Oestrogen produced by the ovaries stimulates the production of LH and prevent production of FSH.

3. Luteinising hormone (LH) produced in the pituitary gland stimulates the release of the egg (ovulation).

4. Progesterone made in the ovaries maintains the uterus lining and prevents the secretion of FSH.

Contraceptive pills

Combined pill:Contains Oestrogen and Progesterone. As when these hormones are in high levels they prevent the release of FSH. High levels of Oestrogen cause side effects.

Mini pill:Progesterone only less side effects.

IVF

1. Women undergoing IVF are injected with FSH and LH (to make the woman produce more eggs).

2. Eggs are then collected from the mother.3. The eggs are fertilised by mixing them with the

fathers sperm in a glass dish.4. Sperm are selected and injected into each egg.5. Fertilised eggs develop into embryos.6. Embryos are inserted into the mothers uterus.