topic 2: cells and control

• adult stem cells

  • stem cells that can differentiate into a limited range of cell types, e.g. bone marrow stem cells
• anaphase

  • the third stage of mitosis in which the chromatids are pulled to opposite poles of the cell by spindle fibres
• asexual reproduction

  • a form of reproduction involving a single parent that creates genetically identical offspring
• axon

  • a long fibre that conducts nerve impulses away from the cell body
• cancer

  • a non-communicable disease caused by changes in the cell that lead to uncontrolled growth and division
• cataract

  • cloudy patch which forms on the lens of the eye and prevents light from entering normally
  • affected individuals have blurred vision, difficulty seeing the intensity of colours and problems with glare
  • it is treated using surgery to exchange the clouded lens for a synthetic one
• cell cycle

  • a series of events that take place in a cell, involving cell growth, DNA replication and cell division
• cell differentiation

  • the process by which an undifferentiated cell becomes specialised for its function
• cell elongation

  • the process by which cells expand and enlarge, enabling the growth of a plant
• central nervous system (CNS)

  • the brain and spinal cord
• cerebellum

  • the region of the brain that controls muscle coordination and non-voluntary movement
  • (e.g. balance, posture)
• cerebral hemisphere

  • one half of the cerebrum
  • the left hemisphere controls muscles on the right side of the body and vice versa
• cerebrum

  • the largest region of the brain consisting of two hemispheres
  • it is responsible for movement, memory, intelligence, language and vision
• chromatid

  • one 'arm' of a replicated chromosome
• chromosome

  • a long, coiled molecule of DNA that carries genetic information in the form of genes
• colour blindness

  • a deficiency of the eye that makes it difficult to distinguish between colours
• cone cells

  • cells found in the retina that are sensitive to high light intensity (bright light) and which detect different colours
• cornea

  • he transparent outer covering that reflects light entering the eye
• CT scan

  • an imaging technique that uses X-rays to create detailed images of internal organs
• cytokinesis

  • the division of the cytoplasm at the end of mitosis to produce two new daughter cells
• dendrites

  • short, branched extensions of dendrons that provide a large surface area to receive nerve impulses from other neurones
• dendron

  • branched extensions of a nerve cell body that connect to other neurones and carry impulses towards the body
• diploid cell

  • a cell that contains two copies of each chromosome (i.e. a full set of chromosomes)
• effector

  • an organ, tissue, or cell that produces a response to a stimulus
• embryonic stem cells

  • stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
• eye

  • a sense organ containing receptors sensitive to light intensity and colour
• growth

  • an increase in mass or size
• haploid cell

  • a cell that contains a single copy of each chromosome (i.e. half the number of chromosomes)
• interphase

  • the longest stage of the cell cycle that involves cell growth, the synthesis of new organelles and DNA replication
• iris

  • a pigmented ring of muscles that controls the size of the pupil to alter how much light enters the eye
• lens

  • a transparent, biconvex structure that refracts light, focusing it onto the retina
• long-sightedness

  • a defect of the eye where nearby objects appear out of focus due to the convergence of light rays behind the retina
  • this occurs when the eyeball is too short or the lens is less elastic
  • it is corrected using a convex lens
• medulla oblongata

  • the region of the brain that regulates unconscious activities such as breathing and heart rate
• meristem tissue

  • plant tissues containing undifferentiated stem cells
• metaphase

  • the second stage of mitosis in which the chromosomes align at the cell equator
• mitosis

  • a form of cell division that produces two genetically identical daughter cells (with a full set of chromosomes) from one parent cell
• motor neurone

  • a neurone that carries nerve impulses from the central nervous system to the effectors
• myelin sheath

  • an electrically insulating layer that surrounds the axon and increases the speed of nerve impulses
• neurones

  • nerve cells adapted to quickly transmit nerve impulses
  • they are the functional units of the nervous system
• neurotransmitters

  • chemicals that are used for communication between neurones and their target cells