B5

• What is homeostasis?

  Regulation of internal body conditions
• Why is homeostasis important for enzyme action?

  It maintains optimal conditions for enzyme function
• What are the components of control systems in homeostasis?

  • Receptors: Detect stimuli
  • Coordination centres: Process information and organize responses
  • Effectors: Produce responses to restore conditions
• What are three things maintained by control systems in the body?

  Body temperature, blood glucose level, water content
• What are neurones?

  Cells that carry information as electrical impulses
• What is the function of the central nervous system (CNS)?

  It consists of the brain and spinal cord
• How do effectors respond to nervous impulses?

  Muscles contract or glands secrete hormones
• What is a synapse?

  The connection between two neurones
• How is a nerve signal transferred across a synapse?

  By the diffusion of chemicals
• What are the five steps in a 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
• What is the brain responsible for?

  All complex behaviours in humans
• What are three methods for studying the brain?

  Observe patients, stimulate brain parts, use MRI
• What is the function of the iris in the eye?

  Controls pupil size
• What happens to the pupil in bright light?

  The pupil shrinks
• What is accommodation in the eye?

  The lens changes shape to focus light
• What are common defects of the eye?

  • Long-sightedness (hyperopia): Focus behind retina, fixed with convex lens
  • Short-sightedness (myopia): Focus in front of retina, fixed with concave lens
• What is the role of temperature receptors in the body?

  Detect core body temperature changes
• What happens when the body is too hot?

  Blood vessels dilate and sweat is produced
• What is the role of the thermoregulatory centre?

  Receives information and triggers effectors
• What happens when the body is too cold?

  Blood vessels constrict and shivering occurs
• What is the endocrine system?

  • Made up of glands
  • Secretes hormones into the bloodstream
  • Carries hormones to target organs
• What hormone do the testes produce?

  Testosterone
• What is the role of insulin?

  Turns glucose into glycogen in the liver
• What is glucagon's function?

  Turns glycogen into glucose in the liver
• What are the types of diabetes?

  • Type 1: Pancreas produces little or no insulin
  • Type 2: Body does not respond to insulin properly
• What is the effect of adrenaline?

  Increases heart rate and glucose supply
• What does thyroxine regulate?

  Basal metabolic rate and growth
• What happens to excess amino acids in the body?

  • Deaminated in the liver
  • Converted into toxic ammonia
  • Ammonia is converted into urea
• How is urine concentration controlled?

  By anti-diuretic hormone (ADH)
• What happens when blood's water content is too high?

  Less ADH is released, less water reabsorbed
• What happens when blood's water content is too low?

  More ADH is released, more water reabsorbed
• What is kidney failure and its treatment?

  • Kidney failure requires regular dialysis
  • Healthy kidneys can be transplanted from donors
• What triggers puberty in the body?

  Release of sex hormones
• What is the main reproductive hormone in men?

  Testosterone
• What is the main reproductive hormone in women?

  Oestrogen
• What are the stages of the menstrual cycle?

  1. Menstruation starts
  2. Uterus lining builds up
  3. Ovulation occurs
  4. Uterus lining maintained or breaks down
• What does FSH do in the menstrual cycle?

  Causes an egg to mature in an ovary
• What does LH do in the menstrual cycle?

  Stimulates ovulation
• What are hormonal methods of contraception?

  • Oral contraceptive pills inhibit FSH
  • Contraceptive implants release progesterone
  • Injections and skin patches work similarly
• What are non-hormonal methods of contraception?

  • Condoms and diaphragms prevent sperm from reaching egg
  • Sterilisation is a permanent procedure
  • Spermicides disable or kill sperm