Bio paper 2

• Synapse


  A gap between the two neurons in which chemicals diffuse across
• Electrical impulse travel


  1. Along the first axon

  2. Triggers the nerve-ending of a neuron to release neurotransmitters

  3. Neurotransmitter diffuses across the synapse (gap) and binds with receptor molecules on the membrane of the second neuron

  4. Receptor molecules on the second neuron transmit electrical impulses
• Neurotransmitter


  A chemical involved in passing nerve impulses
• Central nervous system


  Receives and processes information from receptors (made up of brain and spinal cords)
• Information from receptors


  1. Passes along sensory neurons as electrical impulses to the CNS

  2. Responses of effectors include muscles or glands secreting hormones
• Stimulus


  • Receptor
  • Sensory neuron
  • Motor neuron
  • Effector
• Reflex


  A rapid response to certain stimuli that don't involve the conscious part of the body
• Reflex


  1. Receptors in skin detect stimuli (change in temp)

  2. Sensory neuron sends electrical impulses to relay neuron in the CNS

  3. Motor neuron sends electrical impulses to an effector

  4. Effector produces response
• Endocrine system


  A group of glands which secrete chemicals called hormones directly into the bloodstream
• Compared to the nervous system

  The action is slower but acts for longer
• Pituitary gland


  Known as the master gland because it releases hormones which control the release of other hormones
• Pancreas


  Releases the hormones insulin and glucagon which control blood glucose levels
• Thyroid


  Releases thyroxine which controls metabolism and is involved in maintaining body temperature and heart rate
• Adrenal gland


  Releases adrenaline causing changes in the body such as increased breathing rate, blood glucose, blood flow and dilated pupil
• Ovary


  Releases oestrogen involved in the menstrual cycle
• Testes


  Releases testosterone which controls sperm production
• Blood glucose regulation


  1. Blood with too little glucose

  2. Glucagon secreted by pancreas

  3. Glycogen made by liver turned into glucose

  4. Glucose released into blood by liver

  5. Blood with too much glucose

  6. Insulin secreted by pancreas

  7. Insulin causes glucose to move from blood to cells

  8. Insulin makes liver turn glucose into glycogen

  9. Glucose moves from blood to muscle
• Diabetes


  A condition which affects the ability to control blood sugar levels
• Type 1 diabetes


  The pancreas produces little or no insulin, meaning a person's blood glucose level can rise and kill them
• Testosterone


  The main reproductive hormone in men, produced by the testes and stimulates sperm production
• Oestrogen


  The main reproductive hormone in women, produced by the ovaries and is involved in the menstrual cycle
• Menstrual cycle


  1. Lining of uterus breaks down

  2. Lining of uterus builds up again into a thick spongy layer full of blood vessels, ready to receive an egg

  3. Egg develops and is released-called ovulation

  4. If no fertilised egg has landed on the uterus by day 28, the spongy lining breaks down
• Hormones controlling menstrual cycle

  • FSH
  • Oestrogen
  • LH
  • Progesterone
• FSH


  Produced in pituitary gland, causes an egg to mature in one of the ovaries (follicle), stimulates the ovaries to produce oestrogen
• Oestrogen


  Produced in the ovaries, causes the lining of the uterus to grow, stimulates the release of LH and inhibits release of FSH
• Contraception


  A method to prevent fertilisation of any egg by sperm
• Oestrogen contraception


  Prevents the release of an egg by inhibiting the production of FSH and egg development
• Progesterone contraception


  Reduces fertility by stimulating the production of thick mucus to prevent any sperm from reaching an egg
• Oral contraceptives


  Certain hormones to inhibit FSH production so that no eggs mature
• Injection, implant, or skin patch contraception

  Release progesterone slowly to inhibit the maturation and release of eggs
• Barrier contraception


  Condoms prevent sperm from reaching the egg
• Intrauterine device


  Prevents egg from implanting in the uterine lining
• Spermicidal agents


  Kill or disable the sperm
• Surgical contraception


  Female or male sterilisation such as vasectomy
• Meiosis


  The type of cell division which produces gametes for sexual reproduction
• Meiosis


  1. Cells in reproductive organs divide by meiosis to form gametes

  2. Gametes join at fertilisation to restore the normal number of chromosomes

  3. The new cell divides by mitosis and the number of cells increase

  4. As the embryo develops, cells differentiate

  5. When a cell divides to form gametes, copies of the genetic information are made

  6. The cell divides twice to form 4 gametes, each with a single set of chromosomes

  7. All gametes are genetically different from each other
• Allele


  Different versions of a particular gene
• Dominant allele


  Always expressed, even with only one copy
• Recessive allele


  Only expressed with two copies present
• Homozygous


  If the two alleles are present at the same time