Biology paper 2

• Homeostasis is the maintenance of a constant internal environment and to keep your body functioning properly, we need to control our blood glucose levels, our water levels and our temperature
• Brain


  • Control center, sending signals to various parts of the body
• Parts of the body involved in homeostasis

  • Pancreas
  • Muscles (e.g. shivering)
  • Glands (produce hormones)
• Nervous system


  Consists of the brain, spinal cord (central nervous system), neurons, receptors and effectors
• Reflex


  1. Signal travels from receptor to spinal cord and back again

  2. Signal travels from receptor to brain and back again
• Nerve cells


  Have a very long cell body to send fast electrical signals, but signals between nerve cells are slow chemical signals across a synapse
• Parts of the endocrine system

  • Pituitary gland
  • Thyroid
  • Adrenal glands
  • Pancreas
  • Ovaries
  • Testes
• Testes


  Produce testosterone, which has effects like growing muscles and increasing hair growth
• Ovaries


  Produce estrogen, which is responsible for maturation of eggs and the menstrual cycle
• Pancreas


  Produces insulin, important for regulating blood glucose levels
• Adrenal glands


  Produce adrenalin, important for the fight-or-flight response
• Thyroid


  Produces thyroxine, important in regulating metabolism
• Pituitary gland


  Produces follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
• Control of blood glucose


  1. After a meal, blood glucose rises, pancreas produces insulin, insulin causes cells to remove glucose from blood, lowering blood glucose

  2. If blood glucose gets too low, pancreas produces glucagon, stored glucose is released back into blood, raising blood glucose
• Glycogen


  Stored form of glucose in liver and muscle cells
• Types of diabetes


  • Type 1 (pancreas doesn't produce enough insulin)
  • Type 2 (cells become insensitive to insulin)
• Symptoms of diabetes include loss of weight, increased urination, thirst, blurry vision, fatigue, hunger
• Treatment for type 1 diabetes

  Insulin injections
• Treatment for type 2 diabetes

  Controlling diet and exercise
• Menstrual cycle


  1. Follicle-stimulating hormone rises to grow egg

  2. Luteinizing hormone peaks to release egg

  3. Estrogen builds up to stimulate luteinizing hormone

  4. Progesterone builds up to prepare uterus lining, then decreases causing lining to break down
• Methods of contraception


  • Hormonal (pill, coil/IUD)
  • Non-hormonal (condom, diaphragm)
  • Sterilization (vasectomy, tubal ligation)
• Condoms protect against both pregnancy and sexually transmitted diseases
• About 1 in 6 people experience infertility, with male and female factors each contributing about half
• IVF


  Involves taking many drugs with side effects, is very expensive, and has a 40% success rate per cycle
• Mitosis


  Leads to two identical daughter cells
• Meiosis


  Leads to four genetically different daughter cells
• Mitosis is used for growth and repair, meiosis is used for sexual reproduction
• Mitosis produces diploid cells, meiosis produces haploid cells
• Gametes


  • Eggs (in women)
  • Sperm (in men)
  • Pollen (in plants)
• Meiosis


  Chromosomes line up and divide twice, resulting in haploid cells
• Asexual reproduction produces genetically identical offspring
• Gene


  Stretch of DNA that codes for a characteristic
• Genome


  All the genes in a body
• Gamete


  Sex cell (sperm or egg)
• Chromosome


  Bundled up DNA
• Allele


  Different versions of a gene
• Dominant


  Only need one gene to express a characteristic
• Recessive


  Need two identical recessive genes to express a characteristic
• Homozygous


  Genes are the same
• Heterozygous


  Genes are different