B5

• What is a synapse?

  A gap where neurones meet
• What happens when a chemical diffuses across the synapse?

  It binds to a receptor on the next neurone
• What is homeostasis?

  Regulation of internal conditions for optimum function
• What does homeostasis maintain in the body?

  • Blood glucose concentration
  • Body temperature
  • Water concentration in blood
• What are the components of homeostasis control systems?

  • Receptor cells
  • Coordination centres
  • Effectors
• What do receptor cells do?

  They detect stimuli in the environment
• What is the role of effectors in homeostasis?

  They bring about a response to restore levels
• How does information from receptors reach the CNS?

  It passes along cells as electrical impulses
• What is the role of the CNS?

  It coordinates the response of the effectors
• What is the pathway of a voluntary response?

  1. Stimulus: Lights switch on
  2. Receptor: Cells in retina
  3. Sensory neurone: Carries impulse to coordinator
  4. Coordinator: CNS (brain or spinal cord)
  5. Motor neurone: Carries impulse to effector
  6. Effector: Muscles connected to iris
  7. Response: Pupils get smaller
• What is the pathway of a reflex arc?

  1. Stimulus: Touch hot plate
  2. Receptor: Cells in finger
  3. Sensory neurone: Carries impulse to relay neurone
  4. Relay neurone: Connects sensory and motor neurones
  5. Motor neurone: Carries impulse to effector
  6. Effector: Biceps muscle contracts
  7. Response: Withdraw hand
• What are reflex actions?

  Automatic and rapid actions that protect humans
• What do sense organs contain?

  • Ears: Sound and balance
  • Eyes: Light
  • Skin: Touch, pressure, pain, temperature
  • Nose and tongue: Chemicals for smell and taste
• What is the definition of homeostasis?

  Regulation of internal conditions of a cell
• What is a stimulus?

  An environmental change
• What is negative feedback?

  How changes in the body get reversed
• What is a receptor?

  A cell that detects stimuli
• What is a coordination centre?

  Receives and processes information
• What is the central nervous system?

  The brain and spinal cord
• What is a neurone?

  A cell that transmits electrical impulses
• What is an effector?

  A gland or muscle that causes a response
• What is a response in homeostasis?

  Restores optimum conditions in the body
• What is a reflex?

  A fast, automatic nervous action
• What are the characteristics of neurones?

  • Long axon for long-distance impulse transmission
  • Dendrites/branches for connections with other neurones
• What are the methods of contraception?

  • Oral contraceptive (pill)
  • Injection, implant, patch
  • Barrier methods (condoms/diaphragms)
  • Intrauterine devices
  • Spermicidal agents
  • Abstinence
  • Surgery (vasectomy)
• How does the oral contraceptive work?

  Inhibits FSH so no eggs mature
• What is the role of injection, implant, and patch contraceptives?

  Releases progesterone to inhibit egg maturation
• How do barrier methods of contraception work?

  They prevent sperm from reaching the egg
• What do intrauterine devices do?

  Prevent implantation of an embryo
• What do spermicidal agents do?

  Kill or disable sperm
• What is abstinence in terms of contraception?

  Avoiding sex when an egg may be present
• What is the purpose of surgery in contraception?

  To stop having offspring through sterilization
• What hormones control the menstrual cycle?

  • FSH: Matures an egg, stimulates oestrogen
  • LH: Stimulates release of an egg (ovulation)
  • Oestrogen: Develops uterus lining, inhibits FSH
  • Progesterone: Maintains uterus lining, inhibits LH
• What is the role of the endocrine system?

  • Made of glands releasing hormones
  • Hormones travel in the bloodstream
  • Target organs produce effects
• How does the endocrine system compare to the nervous system?

  Effects are slower but last longer
• What are the roles of different endocrine glands?

  • Pituitary: Master gland, stimulates others
  • Thyroid: Controls metabolic rate
  • Pancreas: Controls glucose levels
  • Adrenal: Prepares body for stress
  • Ovaries: Produce oestrogen, secondary sex characteristics
  • Testes: Produce testosterone, sperm production
• How is blood glucose concentration controlled?

  By the pancreas through negative feedback
• What happens when blood glucose is too high?

  Pancreas produces insulin to lower levels
• What does insulin do?

  Moves glucose from blood into cells
• What happens when blood glucose is too low?

  Pancreas produces glucagon to raise levels