14.4) Homeostasis Homeostasis: is the maintenance of a constant internal environment. Homeostasis is the control of internal conditions within set limits: Cells: change composition of blood as they remove nutrients and O2 and add wastes and CO2. Heart: keeps...
14.3) Hormones in humans Hormone: is a chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target The role of adrenaline: As adrenaline circulates around the body it affects a number of...
14.5) Tropic responses Plants need light and water for photosynthesis. They have developed responses called tropisms to help make sure they grow towards sources of light and water. Gravi(geo)tropism: is a response in which plant grows towards or away...
14.2) Sense organs Sense organs: are groups of sensory cells responding to specific stimuli, such as light, sound, touch, temperature and chemicals. Pupil reflex: The pupil of the eye is the dark round area in the centre of it. It is surrounded by a coloured ring...
14.1) Nervous control in humans Co-ordination is the way all the organs and systems of the body are made to work efficiently together. A nerve impulse is an electrical signal that passes along nerve cells called neurons. The human nervous system...