1. Nerve Impulses When nerves are resting, the inside of the nerve cell is negative, compared to the outside of the nerve cell When a nerve cell is transporting a signal, the electrical difference changes so that a tiny part of the cell becomes positive compared to the outside – called an action potential The action potential travels along the nerve, with the difference returning to normal once it has passed 1.2.3. When an _______________ gets to the end of a nerve cell, it needs to get to another one, or the impulse would never reach our brain. But nerves do not touch each other – the impulse must cross a _________. The gap is called a ______________________. The end of the nerve carrying the impulse sends _______________ across the gap. The chemicals are ______________ by the next nerve and a new impulse starts. This ________ the impulse from one nerve to the next – all the way to the _______. Synapses

2. Hormones and the Menstrual Cycle Hormones are chemical substances that co- ordinate processes in the body. Special glands secrete (release) hormones into the body from where they are carried around the body in the bloodstream. They can act quite quickly but their effects can be slow and long lasting. A good example of how a process is controlled by hormones is the menstrual cycle. Hormones are made in the pituitary gland and ovaries which control the menstrual cycle. The levels of hormones rise and fall in a regular pattern over the 28 day cycle which affects how the body works. Follicle Stimulating Hormone (FSH) Secreted by the pituitary gland Starts the eggs maturing in the ovaries Stimulates the ovaries to produce Oestrogen Oestrogen Made and secreted by the ovaries Stimulates the lining of the womb to build up ready for pregnancy. Stops the production of more FSH Stimulates the production of Luteinising Hormone Luteinising Hormone (LH) Secreted by the pituitary gland Stimulates the release of a mature egg Stops the production of oestrogen

3. Using Plant Hormones Making Plants Grow Plant hormones can be used in rooting powder We can use this to make plant cuttings think that they are roots Gardeners take cuttings from plants, and dip them in the powder, which has the hormones in it The plants responds by growing roots Stopping Plants from Growing However, some plants are affected less than others, which is why it can be sprayed on a farmers field to kill the weed without killing the plants that the farmer wants to grow Auxin based weed killers are used by farmers and gardeners to kill off certain plants As mentioned before – the effect of too much auxin is bad for plants

4. Plant Hormones Plants make chemicals called plant hormones They are in control of processes like - The plant hormones you need to know are Auxins Tropism is the growth or turning of a plant in response to an environmental stimulus. It can be either positive – ____________ Negative - ____________ Phototropism (moving to Light): In a shoot, auxins cause positive phototropism Auxins are made in the tip of the shoot When one side of the shoot is in the light the auxins are distributed in the shady side. This makes the plant elongate on that side and turn towards the light. Geotropism (moving due to gravity): In a root auxins cause positive geotropism Auxins are also made at the tip of the root When a root is growing sideways auxins build up on the underside. Opposite to the shoot they inhibit cell growth ad the root bends downwards