Paper 2

• Define homeostasis

  • Regulation of the internal conditions of a cell or organism to maintain optimal conditions for function in response to internal and external changes
• Explain why homeostasis is important

  • It maintains optimal conditions for enzyme action and cell function
• State 3 conditions controlled in the human body

  • Blood glucose concentration
  • Body temperature
  • Water levels
• State the two types of responses that homeostasis may involve

  • Nervous responses
  • Chemical responses
• State the 3 parts of a control system

  • Receptors
  • Coordination centres
  • Effectors
• Describe a receptor

  • Cells that detect stimuli (changes in the environment)
• Describe a coordination centre

  • Receive and process information from receptors (e.g. brain, spinal cord and pancreas)
• Describe an effector

  • Muscles or glands, which bring about responses to restore optimum conditions
• Describe the purpose of the human nervous system


  • To enable humans to react to their surroundings and coordinate their behaviour
• Describe how information passes along cells (neurones)

  • As electrical impulses
• Describe a neurone

  • A cell that passes information along in the form of electrical impulses
• Describe the central nervous system (CNS)

  • Brain and spinal cord
  • Receives information from receptors and coordinates response of the effectors
• Describe how effectors respond to impulses from the CNS

  • Muscles contract or glands secrete hormones
• Describe the pathway from stimulus to response

  • Stimulus > receptor > coordinator > effector > response
• Describe a reflex action

  • An automatic, rapid response
  • do not involve conscious part of the brain
• Explain why reflex actions are important

  They allow organisms to respond to danger and keep them safe
• Describe the structures of the reflex arc in order

  • Receptor > sensory neurone > relay neurone > motor neurone > effector
• Describe a synapse

  • A junction between two neurones
• Explain how information passes across a synapse

  • The electrical impulse causes chemicals to be released, these diffuse across the gap (synapse)
• Describe the endocrine system

  • The endocrine system is composed of glands which secrete chemicals called hormones directly into the blood
• Describe how hormones travel around the body

  • In the blood from the gland to the target organ
• Compare the endocrine system with the nervous system

  • The effects of the endocrine are slower than the nervous system but act for longer
• State the name of 'master gland' in the body

  • The pituitary gland
• Explain why the pituitary gland is described as a master gland

  • It secretes several hormones into the blood in response to body conditions. These in turn act on other glands to stimulate the release of other hormones to bring about effects
• Name 6 glands in the body (make sure you know where each one is located)


  • Pituitary gland,
  • Pancreas,
  • Thyroid,
  • Adrenal gland,
  • Ovaries,
  • Testes
• Name the organ that monitors and controls blood glucose concentration

  • Pancreas
• Name the hormone produced by the pancreas when blood glucose concentration is too high

  • Insulin
• Explain how insulin reduces blood glucose concentration

  • It causes glucose to move from the blood to the cells
• Describe what happens to excess glucose in liver and muscle cells

  • It is converted into glycogen
• Describe type 1 diabetes

  • pancreas does not produce insulin
  • high blood glucose levels
  • treat with insulin injection
• Describe type 2 diabetes

  • Cells do not respond to insulin produced by the pancreas.
  • Treat with carbohydrate controlled diet and exercise.
  • Obesity is a risk factor
• State the name of the hormone produced by the pancreas if blood glucose levels are too low

  • Glucagon
• Explain how glucagon increases blood glucose concentration

  • Causes glycogen to be converted into glucose and released into the blood
• Describe puberty

  • Development of secondary sex characteristics due to hormones
• Define oestrogen

  • Female reproductive hormone
  • Produced by the ovaries
• Describe ovulation


  • The maturation and release of an egg every 28 days
• Describe testosterone

  • Male reproductive hormone, Produced by testes,
  • Stimulates sperm production
• Describe FHS (follicle stimulating hormone)


  • Produced by pituitary gland, Causes egg to mature in ovary
• Describe LH (luteinising hormone)


  • Produced by pituitary gland,
  • Stimulates release of an egg
• Describe the role of oestrogen and progesterone in the menstrual cycle


  • Maintain the uterus lining