homeostasis and response

• What is homeostasis?


  The regulation of internal conditions in a cell or organism is response to internal and external changes
• Why is homeostasis important?

  It keeps conditions constant for enzyme activity and cell functions
• What can homeostasis include the control of?

  Blood glucose, body temperature, water and ion levels
• What might the control systems of homeostasis involve?

  Responses using nerves, chemical response using hormones
• What do all control systems involve?

  Receptors, coordination centres, effectors
• What is a receptor?


  Cells that detect stimuli (a change in environment)
• What are coordination centres?

  Places such as the brain, spinal cord and pancreas which receive and process information from receptors
• What are effectors?


  Muscles or glands which bring about responses to restore optimum levels
• What is negative feedback?

  A receptor senses a change in stimulus, the coordinating centre compares stimulus to a set point, and effector produces a response to correct distance from set point and so the cycle continues

  
• What is the ideal temperature for the human body?

  37 degrees
• Why is the optimum temperature for the human body 37 degrees?

  Gives optimum temperature for enzymes to work
• What does the thermoregulatory centre in the brain do?

  Monitors and controls body temperature
• What does the thermoregulatory centre in the brain use to get imformation from?

  It has receptors that monitor the temperature of the blood flowing through the brain and receives impulses from temperature receptors in the skin
• What happens if body temperature is too high?

  Blood vessels widen so more blood goes to the surface of the skin (Vasodilation), more sweat is produced from the sweat glands which evaporates - both of these cause a transfer of energy from skin to the environment
• What happens if body temperature is too low?

  Blood vessels marrow so blood goes away from surface of skin (vasoconstriction), sweating stops, skeletal muscles uncontrollably contact and relax quickly (shiver) which transfers heat to blood
• What does the nervous system allow humans to do?

  React with their surroundings and coordinate behaviour
• What is the pathway for a normal nerve impulse?

  Receptor to CNS to effector
• What is the CNS?

  The spinal cord and brain
• What is a reflex action?


  Automatic and rapid so they protect the body. They don't involve the conscious part of the brain
• What is the reflex pathway?


  Receptors to sensory neurone to CNS to relay neurone to effector
• What is the gap between neurones called?

  Synapse
• What type of impulse goes through a neurone?

  An electrical impulse
• What is the endocrine system?

  Include glands which secrete hormones into the bloodstream
• What are hormones?


  Chemical messengers that are carries in the blood to a target organ where they produce an effect
• How do the effect of the nervous system and hormones compare?

  Nervous system is faster, hormones effects last longer
• What is the pituitary gland?

  The 'master gland' that secretes hormones. These can have an effect on other glands to stimulate other hormones to be released
• Where is the pituitary gland?

  Near the brain
• Where is the thyroid gland?


  In your throat
• Where is the pancreas?

  In your belly
• Where are the ovaries and testes?

  Reproductive systems
• What organ controls blood glucose?

  The pancreas
• What happens if blood glucose concentration is too high?

  The pancreas releases insulin which causes glucose to move into muscle cells and the liver where it is stored and glycogen
• What happens if the blood concentration is too low?

  The pancreas releases glucagon which causes the release of glycogen from the liver and muscles back into glucose in the blood stream
• What is type one diabetes?

  A disease that causes the pancreas to produce insufficient insulin resulting in uncontrolled high blood glucose levels
• How is type one diabetes treated?

  Insulin injections
• What is type two diabetes?

  The body cells no longer respond to insulin
• What is a risk factor for type two diabetes?

  Obesity
• How is type two diabetes treated?

  With carbohydrate-controlled diet and regular exercise
• How does water leave the body?

  From the lungs during breathing, from the skin in sweat and in urine
• Which gland secretes oestrogen?

  The ovaries