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Cells and control - Coggle Diagram
Cells and control
Synapses and reflexes
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Nerve signal is transferred by chemicals called neurotransmitters which diffuse across a gap. They then set off a new electrical signal across the gap. The neurotransmitters then set off a new electrical signal in the next neurone.
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1.When a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS.
2.When the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger neurotransmitters to be released. These cause impulses to be sent along the relay neurone.
3.When the impulses reach a synapse between the relay neurone and the motor neurone, they trigger neurotransmitters to be released. These cause impulses to be sent along the motor neurone.
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Mitosis
Mitosis is when a cell reproduces itself by splitting in two to form two genetically identical offspring
Interphase - The cell grows to increase the amount of sub cellular structures and duplicates it DNA so there's one copy of each chromosome for each new cell.
Mitosis
1) Prophase - The chromosomes condense getting shorter and fatter. The membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm.
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3) Anaphase - Cell fibres pull the chromosomes apart. The two arms of each chromosomes go to opposite ends of the cell.
4) Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells.
Cytokinesis - Before telophase ends, the cytoplasm and the cell membrane divide to form two separate cells.
The daughter cells created in mitosis are genetically identical to their parent diploid cell so they are also diploid.
Mitosis is used to asexually reproduce and used by multicellular organisms to replace cells that have been damaged
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Cell elongation - where a plant cell expands making the cell bigger and therefore making the plant grow
Stem cells
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Adult stem cells are not as versatile as embryonic stem cells and cannot differentiate to produce any cell
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Issues - tumour development as you cannot control rate at which stem cells divide, disease transmission as viruses live inside cells and rejection and immunosuppressants can lead you to become infected.
Ethical issues - human embryos should not be used as it is a potential life but you can get from fertility clinic as they would be destroyed
Plants have unspecialised cells produced by the meristem but unlike humans can be produced as long as the plant lives, they go on to form xylem and phloem
The nervous system
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CNS - It is where all the sensory information from receptors are sent and where reflexes and actions are coordinated
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Cell division and growth
Growth in animals -Animals grow when young so when you are young cells divide at a fast rate compared to when you are an adult where most cell division is for repair
Growth in plants - In plants growth in height is mainly due to cell elongation. Cell division happens in the meristem ( the tips of the root and shoot ). Plants continue to grow and differentiate as they grow continously.
If there is a change in one of the genes that controls cell division, the cell can start dividing uncontrollably. This can result in a mass of abnormal cells called a tumour. If the tumour damages surrounding tissue, it is called cancer.
Neurones
- Sensory neurones - Carry information as electrical impulses from sensory receptors to the central nervous system
- Relay neurones - The neurones that carry electrical impulses from sensory neurones to motor neurones. They are found in the CNS.
- Motor neurones - The neurones that carry electrical impulses from the central nervous system the effectors
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