Co-ordination and Control
Responding to Change
The body must responnd to internal and external conditions: you have glands that produce hormones, these are transported round your body by the blood; electrical impulses pass along the nervous system; all responses must be co-ordinated.
The steps involved in a reflex action:
- a receptor detects a stimulus (e.g sharp pain)
- a sensory neurone transmits the impulse
- a relay neurone passes the impulse on
- a motor neurone is stimulated
- the impulse is sent to the effector (muscle or gland)
- action is taken
At the junction between two neurones is a synapse. Chemicals transmit the impulse across the gap.
The Mentrual Cycle
FSH - is made by the pituaty gland and causes the egg to mature and oestrogen to be produced
Oestrogen - is produced by the overies and inhibits the further production of FHS. It stimulates the production of LH and also stimulates the womb lining to develop to receive the fertilised egg.
LH - is made by the pituitary gland and stimulates the mature egg to be released.
The Artificial Control of Fertility
The contraceptive pill contains oestrogen. This prevents the production of FSH so no eggs mature.
If a woman cannot produce mature eggs then FSH can be given. This is known as 'fertility treatment'.
Internal conditions that are controlled include: water content, ion content, temperature, blood sugar level.
Water is leaving the body all the time as we breathe out and sweat. We lose any access water in the urine (produced by the kidneys). We also lose ions in our sweat amd in the urine.
We must keep out temperature constant otherwise the enzymes in the body will not work properly (or may not work at all).
Sugar in the blood is the energy source for cells. The level of sugar in our blood must be controlled.