Cells and Control
- Created by: Former Member
- Created on: 09-08-19 08:28
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- Section 2 - Cells and Control
- Mitosis
- genetic material > chromosomes
- Body cells are diploid
- Produces two cells identical to original
- Cell cycle
- Interphase - cell grows to increase mitochondria and ribosomes. Duplicates DNA ( X shape)
- Mitosis in Cytokinesis: PROPHASE = membrane breaks down METAPHASE = chromosomes line up at centre ANAPHASE = cell fibres pull them apart TELOPHASE = Membranes form around two sets, cytoplasm and membrane divide to form two cells
- genetic material > chromosomes
- Cell division and growth
- CELL DIFFRENTIATION = cell changes to be more specialised
- CELL DIVISION = by mitosis
- CELL ELONGATION = plant cell expands
- cancer is a case of uncontrolled cell division
- abnormal cells = tumour attacks surrounding tissue
- Percentile charts are used to monitor growth
- Stem Cells
- embryonic stem cells hae the potential to produce any cell
- Important for growth and development of organisms
- Meristems contain plant stem cells
- generate any cell type for as long as the plant lives (xylem and phloem)
- use in medicine
- used to replace damaged specialised cells
- RISKS: tumour development, disease transmission, rejection
- The Nervous System
- Sensory receptors convert stimulus to nervous impulse - sent to CNS
- CNS coordinates a response sending info to effector by a motor neurone
- dendrites and dendrons towards cell body / axons away
- myelin sheath acts as insulator - speeds up impulse
- sensory neuron: one long dendron & one short axon
- motor neurone: many short dendrites & one long axon
- relay neurone: many short dendrites & an axon
- Sensory receptors convert stimulus to nervous impulse - sent to CNS
- Synaoses and reflexes
- Synapses connect neurones
- reflexes help prevent injury
- neurones in reflex arc go through spinal cord - they reach a synapse and neurotransmitters are released - impulses sent to effector
- quicker than normal responses - no thinking
- reflex protects the eye: light receptors > sensory neurone > relay neurone > motor neurone > circular muscles in iris contract > smaller pupil
- neurones in reflex arc go through spinal cord - they reach a synapse and neurotransmitters are released - impulses sent to effector
- Mitosis
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