cells and control

• Chromosomes

  Genetic information found in the nucleus, containing coils of DNA
• Gene


  Short section of DNA that codes for a protein and controls a characteristic
• There are 23 pairs of chromosomes in each cell of the body, resulting in 46 chromosomes in total
• Sex cells (gametes) have half the number of chromosomes, resulting in 23 chromosomes in total
• Diploid number of chromosomes

  Amount found in body cells (46 in humans)
• Haploid number of chromosomes

  Half the diploid amount (23 in humans), found in gametes
• Cell cycle


  1. Interphase

  2. Mitosis

  3. Cytokinesis
• Mitosis


  • Chromosomes line up at the equator
  • Cell fibres pull each chromosome to either side
  • Two identical daughter cells form
• Mitosis


  Cell division that produces two genetically identical diploid daughter cells
• Cell division by mitosis is important for growth, development, and replacing damaged cells in multicellular organisms
• Mitosis is a vital part of asexual reproduction
• In animals, growth occurs via cell division and differentiation
• In plants, growth occurs by cell division, differentiation, and elongation
• Cancer

  Uncontrolled cell division resulting in a tumour
• Percentiles

  Charts used to measure the growth of an organism compared to others
• Measurements used to monitor growth

  • Mass
  • Length
  • Head circumference
• Stem cell

  Undifferentiated cell that can undergo division to produce many more similar cells, some of which will differentiate
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Meristems in plants
• Therapeutic cloning


  Producing an embryo with the same genes as the patient to obtain embryonic stem cells
• The brain and spinal cord make up the central nervous system, responsible for controlling consciousness, movements, thoughts, and emotions
• Important structures of the brain

  • Cerebral hemispheres
  • Cerebellum
  • Medulla oblongata
• The cerebral hemispheres are responsible for consciousness, memory, intelligence, visual and sensory processing
• The cerebellum is responsible for controlling fine movements of muscles
• The medulla oblongata is responsible for maintaining basic autonomic bodily functions like breathing, digestion, and swallowing
• CT and PET scans are used by doctors to examine the brain
• Stem cells from discarded embryos at fertility clinics could be used for research
• Removal of stem cells results in destruction of the embryo
• Research into the process of differentiation
• People may have religious or ethical objections as it is seen as interference with the natural process of reproduction
• If the growing stem cells are contaminated with a virus, an infection can be transferred to the individual
• Money and time could be better spent on other areas of medicine
• Medulla oblongata


  A small 'elongated' structure found in the brainstem, at the base of the brain, responsible for maintaining basic autonomic bodily functions such as breathing, digestion, swallowing and sneezing
• Doctors often need to look inside the brain to examine brain tissue for injury and disease
• Cutting the skull open and physically examining the brain is highly invasive and often does not provide any clues about brain function
• CT (Computerised Tomography) scans


  Fire X-Ray radiation at the brain from several different angles to generate a 3D image of the brain, useful for examining bleeding within the skull and damage to brain structures
• PET (Positron Emission Tomography) scans


  A radioactive 'tracer' is injected into the blood before the scan, the scan is sensitive to the tracer so areas with greater blood flow are highlighted, useful for identifying cancerous tumours
• CT scans are usually not recommended for pregnant women and children as it exposes them to higher doses of radiation than a normal X-ray
• Investigating brain function and treating brain damage and disease is difficult because it is complex and delicate, easily damaged, drugs cannot always reach the brain, and it is not fully understood which part of the brain does what
• Cancerous tumours can form in the brain as in any other part of the body, they can push against other structures and blood vessels in the brain, restricting their function, and are especially difficult to remove if buried deep in the brain or spinal cord
• Nervous system response to stimuli

  1. Receptor cells convert stimulus into electrical impulse

  2. Impulse travels along sensory neurons to central nervous system

  3. Information processed, appropriate response coordinated, impulse sent along motor neurons to effectors

  4. Effectors carry out response