Cells and control

- Every living thing needs to be able to grow and repair themselves. 

- The nuclei of dipoild cells contain 2 copies of each 23 chromoses 

The cell cycle 

2 phases = interphase and mitosis 

(see cell cycle cards) 

A-sexual reproduction 

- They produce off spring that are clones; their cells have the same chromosomes as it's parents 

- Really quick because doesn't have anything else and it dosen't produce different 

- Growth - an increase in size as a result of an increase in number or size of cells 

- Growth of babies is measured on a percentile chart 

Cell differentination 

- cells produce by mitosis can become specilased thhis is called differntiation. 

e.g: Fat cells =  lots of space so that there is room to store fat droples until they are needed 

       Muscel Cells = contian special contractive protiens that can contract muscels 

- A group of cells near the end if each shoot and root allows plants to keep growing, these are called meristems 

- These cells divide by mitosis, the cells proudced then increase in length (elongation) and differenentate into specialsed cells. 

Specialised plant cells 

Root hair cells = found in the surface of plant roots, large surface area to absorb minerals and nutrients in the soil. 

Xylem cells = a long thick walled tube found in plants, formed by many dead cells, the tube carrys water and minerals in the plant. 

Percentage change in mass:

final value - start value ÷ starting value x 100 

Stem cells = cells that can repededly divide over long period of time. 

- The cells of an early-stage embryo are called embryonic stem cells. They can produce anytype of specilised cells. 

- As the cells start to divide the embryo starts to have different areas for differnt organs 

- These differnent areas start to become more specailised so they can't produce any sort of of cell anymore 

- By the time the young animal has devolped, the stem cells can only produce the specailised cell in which tissue they are

Theating diseases 

- Stem cells offer a way of treatinf diseases caused by damaged cells. 

- They use adult and embryonic stem cells such as type 1 diabetes or to recplace damaged cells. 

- Sometimes the body can reject these cells. 

- The central nervous sytem is made up of the brian and spinal cord 

Nerves - cells that carry electrical impules 

Stimlus - anything your body is sensitive too.

Sense organs - contains receptor cells that detect stimuli 

Receptor cells - create electrical impulses which travel to the brain. 

Neurotrasmissions - the trasmission of impulses. 

- When the brain coordinatates a response to a stimulus impluses are sent to the effectors 

Motor neurones - carrys impluses to the effector

Relay neurones - are short neurones that are found in the spinal cord, they link sensory and motor neurones. They make up lots of nerve tissue in the brain. 

Synapes 

- When one neruone meets another at a synapse, which contains a small gap. 

- When the impulse reaches an axon terminal a neurotrasmitter chemical is relased into the gap. 

- This is detected by th next neurone which generates a new impulse. 

- They slow down neurotrasmissions -

- Usefull becasue they are only relased from axon terminals, so impulses only travel in one direction

- Generates new neurone impluses so the original one does not loose strenth.