biology topic 2

• Mitosis


  1. Cell division

  2. Growth and repair
• Mitosis always produces identical cells
• Mistakes in DNA copying during mitosis

  Can cause uncontrolled cell division and tumors
• Growth


  Increase in size or number
• Plant cell growth


  Cells elongate and divide at roots
• Animal cell growth


  Cells typically just divide
• Percentile charts


  Measure growth by comparing to other organisms
• Stem cells


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

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


  • Can turn into any type of specialized cell
  • Found in early embryo
• Adult stem cells


  • Can only turn into certain types of specialized cells
  • Found in animals that have stopped growing
• Plant meristem stem cells


  • Can turn into any type of plant cell
  • Found in plants that continue growing
• Stem cells can be used in medicine to produce needed cell types, but there are risks of tumor growth or immune rejection
• Nervous system


  System that sends and receives information
• Parts of the nervous system

  • Central nervous system (brain and spinal cord)
  • Peripheral nervous system (all other neurons)
• Motor neurons


  • Have dendrites on cell body and axon
  • Carry impulses to muscles and glands
• Relay neurons


  • Look like motor neurons
  • Found in brain and spinal cord
• Myelin sheath


  Insulates neurons and speeds up impulses
• Synapse


  Small gap between neurons where neurotransmitters are released
• Cerebrum


  • Makes up main bulk of brain
  • Divided into two hemispheres
• Cerebellum


  • Responsible for motor functions like walking
• CT scan


  Builds up image of brain structure and shape
• PET scan


  Measures brain activity by detecting radioactive glucose uptake
• Reflex arc

  1. Receptor detects stimulus

  2. Impulse travels directly to effector without going through brain

  3. Effector (muscle) responds quickly
• Lens

  • Focuses light onto retina
• Iris and pupil


  • Control amount of light entering eye
• Cornea


  • Helps focus light
• Optic nerve


  • Sends visual information to brain
• Retina


  • Contains light-sensitive rods and cones
• Rods


  Detect differences in light intensity, work well in dim light
• Cones


  Detect color, need bright light to function
• Lens shape


  Changes to focus light from near or far objects
• Long-sightedness


  Light focused behind retina, close objects appear blurred
• Cataracts

  Clouding of the lens, caused by protein buildup