Biology topic 5 - Homeostasis and Response

• what is homeostasis ?

  • maintaining a stable internal environment homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and eternal changes
• what does homeostasis do ?

  it maintains optimal conditions for enzyme action
• what does our body have that regulates our internal environment ?

  automatic control systems that are made up of 3 components which are the receptors, coordination centres and effectors
• what does homeostasis control in the human body ?

  1. blood glucose concentration 2. body temperature 3. water levels
• what do receptors do ?

  detect stimuli ( changes in the environment )
• what do the coordination centres do ?

  examples of the CC are the brain, spinal cord and pancreas and the CC receive and process information from the receptors
• what do effectors do ?

  examples of effectors are muscles and glands and the effectors bring about responses which restore optimum levels.
• what is negative feedback ?

  a mechanism that brings the level of glucose or water when too high or low back to normal. it counteracts change
• what does the nervous system do ?

  Enables humans to react to their surroundings and to coordinate their behaviour. it detects and reacts to stimuli.
• what is the Central Nervous system?

  a coordination centre that receives information from the receptors and then coordinates a response and this response is carried out by effectors.
• what does the CNS do ?

  it is made up of the brain and spinal cord. the CNS coordinates the response of effectors which may be muscles contracting or glands secreting.
• what is the nervous system made up of?

  CNS, sensory and motor neurones and effectors
• what is a neurone ?

  nerve cells
• what is a nerve ?


  a bundle of neurones
• what are the 3 types of neurones ?

  sensory, motor or relay neurone
• what are receptors ?


  a group of specialised cells that detect a change in stimulus (environment) and stimulate electrical impulses in response
• what are sensory neurones ?


  neurones that carry information as electrical impulses from the receptors to the CNS
• what are motor neurones ?

  neurones that carry electrical impulses from the CNS as effectors.
• what are synapses ?


  the connection between 2 neurones
• what are reflexes and what do they prevent ?

  they prevent injury and they are rapid, automatic responses to certain stimuli and they do not involve the conscious part of the brain.
• what is a reflex arc ?


  the passage of information in a reflex from receptor to effector
• what happens when a stimulus is detected by receptors ?

  impulses are sent along a sensory neurone to a relay neurone in the CNS.
• what happens when the impulses reach a synapse between the sensory and relay neurone?

  they trigger chemicals to be released and these chemicals cause impulses to be sent along the relay neurone
• what is reaction time and the factors affected by it ?


  the time it takes to respond to a stimulus - often less than a second and factors affected : age, gender , drugs
• what do the pancreas do ?

  produce insulin which is used to regulate the blood glucose level
• where are hormones produced in and secreted by ?

  produced in and secreted by various glands , called endocrine glands and these glands make up the endocrine system.
• give examples of glands

  pituary gland, ovaries, testes, adrenal gland, thyroxide , pancreas
• what do the ovaries do ?


  produce oestogen which is involved in the menstrual cycle.
• what do the testes do ?

  produce testerone which control puberty and sperm production in males.
• what is the endocrine system composed of ?

  it is composed of glands which secrete chemicals called hormones directly into the bloodstream.
• what are hormones ?

  chemical messengers released directly into the blood and they are carried in the bloodstream to other parts of the body but only affects the target organ. the blood carries the hormone to a target organ where it produces an effect.
• what do hormones do ?

  control things in organ and cells that need constant adjustment
• what is the pituaty gland and what does it do ?

  it produces many hormones that regulate body conditions. the pituary gland in the brain is a 'master gland' which secretes several hormones in the blood in response to body conditions. these hormones act on other glands directing them to release hormones that bring about change.
• what does the thyroid do ?

  produce thyroxine which is involved in regulating things like the rate of metabolism , heart rate and temperature.
• what does adrenal gland do ?

  produces adrenaline which is used to prepare the body for a 'flight or fight' response.
• what is type 2 diabetes ?

  where a person becomes resistant to their own insulin. the body cells no longer respond to insulin produced by the pancreas. this can cause a person's blood glucose level rise to a dangerous level.
• what is the treatment for type 2 diabetes ?

  eating a carbohydrate controlled diet and getting regular exercise.
• what is the risk factor for type 2 diabetes ?

  obesity
• what is diabetes ?

  a condition that affects your ability to control your blood sugar levels.
• what are the types of diabetes ?

  type 1 and type 2