cells and control

• Mitosis


  1. Cell division

  2. Growth and repair
• Interphase


  1. Cell replicates DNA

  2. Cell makes more organelles like mitochondria and ribosomes
• Prophase


  1. The chromosomes condense, getting shorter and fatter

  2. The membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm
• Metaphase


  The chromosomes line up at the center of the cell
• Anaphase


  Spindle fibers pull the chromosomes apart. Then the chromatids are pulled to opposite ends of the cell
• Telophase


  Membrane form around each of the sets of the chromosomes. These become the nuclei of the two new cells - the nucleus has divided
• Cytokinesis


  Cytoplasm splits creating two daughter cells
• Mitosis always produces two new genetically identical cells
• Mistakes in DNA copying during mitosis

  Can cause mutations and uncontrolled cell division, creating a tumor
• Growth


  Increase in size or number
• Plant cell growth


  • Growth in height is mainly due to cell elongation- cell division usually just happen in the tips of the roots and shoots. But plants often grow continuously - even really old trees will keep on putting on new branches. so plants continue to differentiate to develop new parts
• Animal cell growth


  • Happens by cell division. Animals tend to grow while they're young and they reach full growth and stop growing. so when you're young, cells divide at a fast rate but once you're adult, most cell division is for repair- the cells divide to replace old or damaged cell. This also means, in most animals, cell differentiation is lost at an early stage
• Percentile charts


  Used to measure growth and compare an organism's growth against others
• Stem cells


  Unspecialized cells that can differentiate into specialized cells
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Plant stem cells
• Embryonic stem cells


  • Can turn into any type of specialized cell
• Adult stem cells


  • Can only turn into certain types of specialized cells
• Plant stem cells


  • Can turn into any type of specialized cell
• Stem cells can be used in medicine to help cure and fix certain diseases
• There are problems with using stem cells, such as the cells continuing to divide and creating a tumor, or the body's immune system rejecting the cells
• Nervous system


  The way the body sends and receives information
• Parts of the nervous system

  • Central nervous system (brain and spinal cord)
  • Peripheral nervous system (all other neurons)
• Types of nerve cells

  • Sensory neurons
  • Motor neurons
  • Relay neurons
• Sensory neurons


  • Connected to receptors that take in the surroundings
• Motor neurons


  • Carry impulses to muscles or glands
• Relay neurons


  • Short neurons found in the brain and spinal cord
• Myelin sheath


  Covers and insulates neurons to speed up impulses
• Nerve impulse pathway


  1. Stimulus

  2. Receptor

  3. Sensory neuron

  4. Relay neuron

  5. Motor neuron

  6. Effector (muscle or gland)

  7. Response
• Synapse


  Small gap between neurons where neurotransmitters are released
• Main parts of the brain

  • Cerebrum
  • Cerebellum
  • Brain stem/medulla oblongata
• Cerebrum


  • Makes up the main bulk of the brain, divided into two hemispheres
• Cerebellum


  • Responsible for motor functions like walking
• Brain stem/medulla oblongata


  • Responsible for unconscious processes like breathing and heart rate
• CT scan


  Builds up an image of the shapes and structures in the brain using an x-ray beam
• PET scan


  Measures brain activity by detecting radioactive glucose taken up by more active brain cells
• Reflex arc


  A completely unconscious process that allows the body to quickly react to potentially dangerous situations
• Parts of the eye

  • Lens
  • Iris
  • Pupil
  • Cornea
  • Optic nerve
  • Retina
• Lens


  • Focuses light into the eye
• Iris


  • Colored part of the eye that controls the pupil
• Pupil


  • Hole in the middle of the iris that allows light into the eye