Homeostasis and Response

• Abstinence


  Deliberately refraining from having sexual intercourse
• Accommodation


  The process of changing the shape of the lens to focus on near or distant objects
• Adrenaline


  A hormone that is produced by the adrenal glands in response to fear or stress which increases the heart rate and boosts the delivery of blood to the brain and muscles as a part of the 'fight or flight' response
• Antidiuretic hormone (ADH)


  A hormone that increases the reabsorption of water in the kidney tubules
• Contraception


  Methods used to prevent pregnancy
• Coordination centres


  Areas of the body like the brain, spinal cord and pancreas that receive and process information from receptors
• Deamination


  A process occurring in the liver that removes the amino group from an amino acid to produce ammonia
• Dialysis


  A method of treating kidney failure or disease where the blood is artificially filtered to remove waste and toxins
• Effectors


  Muscles or glands which bring about responses which restore optimum levels
• Ethene


  A type of plant hormone which controls cell division and the ripening of fruits
• Follicle stimulating hormone (FSH)


  A female reproductive hormone that causes the maturation of an egg in the ovary
• Geotropism/Gravitropism


  A plant's directional growth response to gravity
• Gibberellins


  A type of plant hormone which initiates seed germination
• Gland


  A group of cells that secrete chemicals called hormones directly into the bloodstream
• Glucagon


  A hormone produced by the pancreas that causes glycogen to be converted into glucose and released into the blood
• Homeostasis


  The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
• Hyperopia


  A defect of the eye where nearby objects appear out of focus (also called long sightedness)
• In Vitro Fertilisation (IVF)


  Fertilising a woman's egg using sperm outside of the body
• Luteinising hormone (LH)


  A female reproductive hormone that stimulates the release of an egg
• Homeostasis


  The maintenance of a constant internal environment
• Myopia


  A defect of the eye where distant objects appear out of focus (also called short sightedness)
• What homeostasis controls in the human body

  • Blood glucose concentration
  • Body temperature
  • Water levels
• Negative feedback cycle


  A regulatory mechanism that reverses a change
• Control systems


  • Receptors - cells that detect stimuli
  • Coordination centres - process the information received from the receptors
  • Effectors - bring about responses to bring the conditions in the body back to optimum levels
• Response to a stimulus

  1. Receptor cells convert a stimulus into an electrical impulse

  2. Electrical impulse travels along sensory neurons to the central nervous system

  3. Information is processed and the appropriate response is coordinated

  4. Electrical impulse is sent along motor neurons to effectors

  5. Effectors carry out the response
• Oestrogen


  The main female reproductive hormone which causes the uterus lining to grow and repair
• Reflex


  Automatic responses which take place before you have time to think
• Phototropism


  A plant's directional growth response to light
• Reflex arc


  1. Stimulus is detected by receptors

  2. Impulses are sent along a sensory neuron

  3. In the CNS the impulse passes to a relay neuron

  4. Impulses are sent along a motor neuron

  5. The impulse reaches an effector resulting in the appropriate response
• Receptors


  Organs or cells that detect stimuli
• Synapse


  The gaps between two neurons
• Reflex action


  A rapid and automatic response to a stimulus
• Reaction time


  How long it takes you to respond to a stimulus
• Selective reabsorption


  Reabsorbing certain useful molecules (like glucose, some ions and water) back into the blood after they have been filtered out
• Components of the brain

  • Cerebral cortex
  • Cerebellum
  • Medulla
• Stimuli


  Changes in the environment
• Challenges in investigating brain function and treating brain damage/disease

  • It is complex and delicate
  • It is easily damaged
  • Drugs given to treat diseases cannot always reach the brain because of the membranes that surround it
  • It is not fully understood which part of the brain does what
• Methods used by neuroscientists to map brain function

  1. Studying patients with brain damage

  2. Electrically stimulating different parts of the brain

  3. Using MRI scanning techniques
• Target organ


  The organ which a hormone acts on to produce an effect
• Testosterone


  The main male reproductive hormone produced by the testes and it stimulates sperm production