cells and control

• Mitosis - division of cells

  • creates 2 genetically identical daughter cells
  • happens everywhere in body
  • growth and repair
  • diploid cells
• Interphase

  • DNA replicated
  • cell growth
• Prophase

  • nuclear membrane breaks down
  • spindle fibres formed
• Metaphase

  • chromosomes line up along the middle of the cell
• Anaphase

  • pulled to opposite ends of the cell by spindle fibres
• Telophase

  • new nuclear membrane forms
• Cykotenisis

  • 2 genetically identical daughter cells formed
• Meiosis - division of cells

  • happens in reproductive organs
  • testes / ovaries
  • 4 genetically different cells created
  • creates gametes
  • haploid cells
• Specialised cells

  • cells differentiate
  • become specialised for a specific purpose
• sperm cell

  • mitochondria - energy
  • tail - to swim
  • acrosomes - get through egg cell wall
• root hair cell

  • large surface area - absorb water / mineral ions
  • mitochondria - energy for active transport
• stem cells

  • undifferentiated cells
  • bone marrow / can only turn into blood cells
  • embryonic cells / can turn into any type of cell
• can be used to help illness

  • sickle cell anaemia - replace faulty red blood cells
  • paralysis - replace faulty nerve cells
• embryonic stem cells

  • risk of rejection
  • ethical concerns - destroying an embryo / potential life
• CNS - brain / spinal cord
• cerebral cortex - high level processes

  • language
  • memory
• cerebellum

  • balance
  • posture
• medulla - automatic processes

  • heart rate
  • breathing
• study the brain

  • CT scan
  • PET scan
  • MRI scan
• difficult to treat

  • hard to access
  • very complicated
  • a lot can go wrong
• synapse

  • gap between neurones
  • electrical impulse sparks release of neurotransmitter chemical
  • diffuses across synapse
  • binds with receptor cells
  • sparks new electrical impulse on a new neurone
• Reflex arc

  • stimulus
  • receptor
  • sensory neurone
  • relay neurone
  • CNS
  • motor neurone
  • effector
  • responce
• reflex arc purpose

  • happen very quickly
  • protect from harm
• Eye

  • OPTIC NERVE - sends impulses to CNS
  • LENS / CORNEA - refract light
  • RETINA:
  • cone cells - detect colour
  • rod cells - detects light intensity
• Iris reflex - dim light

  • pupil dilate
  • radial muscles contract
  • circular muscles relax
• Iris reflex - bright light

  • pupil contracts
  • radial muscles relax
  • circular muscles contract
• vision defects - long sighted

  • close - blurry
  • far - clear
  • eyeball too short - image focus behind the retina
  • corrected by converging lens
• vision defects - short sighted

  • close - clear
  • far - blurry
  • eyeball too long - image focus in front of the retina
  • corrected with diverging lens