Topic 2

• what is mitosis?

  cell division the results in new body cells being produced
• what does diploid mean?

  having two copies of each chromosome
• list three reasons why mitosis is important?

  -growth

  -repairs tissues/replaces cells

  -asexual reproduction
• what are the five stages of mitosis?

  Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
• what occurs before mitosis?

  Interphase
• what happens in interphase?

  -DNA is replicated (chromosomes are copied)

  -cell organelles are duplicated
• what happens in the nucleus during prophase?

  it starts to break down and spindle fibres appear
• what happens in the nucleus during metaphase?

  -chromosomes line up along the middle of the cell

  -the spindle fibres attach to the chromosomes at the centrometre

  (middle of the X shape)
• what happens in the nucleus during anaphase?

  the chromosomes separate and are pulled to each end of the cell by the spindle fibres
• what happens in the nucleus during telophase?

  a membrane forms around each set of chromosomes to form 2 new nuclei
• what happens in the nucleus during cytokinesis?

  the cell surface membrane divides to form 2 separate cells

  (in plant cells, cells form a wall)
• in asexual reproduction what are the offspring referred to as?

  clones
• what is the process that changes undifferentiated cells in to specialised ones?

  Differentiation
• what is a stem cell?

  an undifferentiated cell
• name two ways a red blood cell is specialised

  -no nucleus

  -large surface area
• what are the two types of stem cell?

  -adult stem cells

  -embryonic stem cells
• how are stem cells used in medicine?

  bone marrow transplants
• list three potential risks of stem cell treatment

  -cells made divide to rapidly and cause a tumour

  -disease through transmission

  -rejection by recipients immune system
• why might some people disagree with using embryonic stem cells in research?

  because it destroys life
• where are stem cells found in plants?

  Meristems
• what is the definition of growth?

  increase in size as a result of an increase in number/size of cells
• where does growth occur in plants?

  roots and shoots (meristems)
• what happens if cells start to divide uncontrollably?

  Cancer
• how does growth occur in animals?

  -cell division

  -cell differentiation
• how does growth occur in plants?

  -cell division

  -cell differentiation

  -cell elongation
• what does it mean if a child is on the 75th percentile for height?

  75% of children the same age are shorter
• what is the function of the nervous system?

  allow communication between different parts of the body
• name the organs in the central nervous system (CNS)

  -brain

  -spinal chord
• what is the spinal chord?

  a long column of neurones the connect the brain to the rest of the body
• what is the function of the spinal chord?

  to carry information between the brain and the rest of the body
• what is the function of the sensory neurone?

  to carry impulses from receptor cells in the sensory organs to the CNS
• what is the function of the motor neurone?

  to carry impulses from the CNS to the effectors
• what are relay neurones?

  short neurones found in the spinal chord linking the motor and sensory neurones
• what feature allows impulses to be transmitted quickly along a neurone?

  -long axon

  -sensory neurons have a myelin sheath
• what is the function of the myelin sheath?

  insulates the neurone to stop the impulse losing energy
• which substance transmits an impulse from one neurone to another?

  neurotransmitter
• what is a synapse?

  a gap between two neurones across which neurotransmitters diffuse
• what is the word for a change in the environment that the body reacts to?

  Stimulus
• describe the path of a reflex arc

  stimulus--> receptor--> sensory neurone--> relay neurone--> effector-->response
• what is the advantage of a reflex arc?

  is allows a fast automatic response to danger