Bio paper 2

• Homeostasis


  The regulation of the conditions inside your body and cells. It maintains a stable internal environment in response to changes in internal and external conditions.
• Components of control systems

  • Receptors
  • Coordination centres
  • Effectors
• Receptors


  • To detect stimuli (changes in environment)
• Coordination centres


  • To receive and process information from receptors and organise a response
• Effectors


  • To produce a response to counteract change and restore optimal conditions
• Automatic control systems can involve nervous or chemical responses
• Things in your body maintained by control systems

  • Body temperature
  • Blood glucose level
  • Water content
• Synapse


  The connection between two neurones. A nerve signal is transferred across a synapse by the diffusion of chemicals.
• Reflex Arc


  1. Stimulation of pain receptor

  2. Impulses travel along sensory neurone

  3. Impulses passed along relay neurone

  4. Impulses travel along motor neurone

  5. Muscle contracts and arm moves
• Neurones


  Cells that carry information as electrical impulses in the nervous system
• Central Nervous System (CNS)

  Consists of the brain and spinal cord. It is connected to the body by sensory neurones and motor neurones.
• Effectors


  Can be muscles (which respond to nervous impulses by contracting) or glands (which secrete hormones)
• Controlling Blood Glucose


  1. Pancreas detects high blood glucose and secretes insulin

  2. Insulin causes glucose to move into cells

  3. Insulin makes the liver turn glucose into glycogen, which is stored

  4. Blood glucose reduced
• Increasing Blood Glucose


  1. Blood with too little glucose

  2. Glucagon secreted

  3. Glucagon makes the liver turn glycogen into glucose, which is released

  4. Blood glucose increased
• Insulin and glucagon work in a negative feedback cycle
• Type 1 Diabetes


  Pancreas produces little or no insulin
• Type 2 Diabetes


  Cells no longer respond to insulin properly
• Adrenaline


  • Released in response to fear or stress
  • Increases supply of oxygen and glucose to muscles and brain
  • Readies body for 'fight or flight'
• Thyroxine


  • Plays a role in regulating the basal metabolic rate
  • Important for protein synthesis for growth and development
• Puberty


  When the body starts releasing sex hormones, which trigger the development of secondary sexual characteristics
• Main reproductive hormones


  • Testosterone (in men)
  • Oestrogen (in women)
• Menstrual Cycle


  1. Menstruation starts, uterus lining breaks down

  2. Uterus lining builds up

  3. Egg develops and is released from ovary

  4. Wall is maintained if no fertilised egg lands
• FSH (Follicle-Stimulating Hormone)


  Causes an egg to mature in an ovary
• LH (Luteinising Hormone)


  Stimulates ovulation
• Oestrogen


  Causes uterus lining to grow
• Progesterone


  Maintains uterus lining, inhibits FSH and LH
• Hormonal contraception methods


  • Oral contraceptive pills
  • Contraceptive implant
  • Injections or skin patches
  • Intrauterine devices
• Non-hormonal contraception methods


  • Condoms and diaphragms
  • Sterilisation
  • Spermicides
  • Abstaining from sexual intercourse
• IVF (In Vitro Fertilisation)

  1. Woman given FSH and LH to stimulate egg maturation

  2. Eggs collected from ovaries

  3. Eggs fertilised in lab with sperm

  4. Fertilised eggs grown into embryos

  5. One or two embryos transferred to woman's uterus
• DNA (Deoxyribonucleic Acid)


  The chemical a cell's nuclear genetic material is made from
• Chromosomes


  Long molecules of DNA that normally come in pairs. Humans have 23 pairs.
• Gene


  A small section of DNA found on a chromosome that codes for a particular sequence of amino acids
• Genome


  An organism's entire set of genetic material
• Types of reproduction


  • Asexual
  • Sexual
• Meiosis


  1. Cell duplicates genetic information

  2. Cell divides, each new cell has one copy of each chromosome

  3. Both cells divide again to make four gametes, each with a single set of chromosomes
• Gametes


  Cells produced by meiosis in the reproductive organs
• Fertilisation


  Two gametes fuse to form a cell with the normal number of chromosomes, which then divides by mitosis to form an embryo
• Genetic terms


  • Allele
  • Dominant
  • Recessive
  • Homozygous
  • Heterozygous
  • Genotype
  • Phenotype
• Genetic diagrams


  • Punnett square for X and Y chromosome sex determination
  • Punnett square for a genetic cross between pea plants
• Polydactyly


  Genetic disorder where a baby is born with extra fingers or toes, caused by a dominant allele