Topic 5

• What is homeostasis?

  The maintenance of a constant environment to maintain optimum conditions
• Give 3 examples of conditions maintained by homeostasis?

  Body temperature, blood glucose concentration and water levels
• What are the 2 types of responses?

  Nervous and chemical
• What three components do all control systems have?

  Receptors, coordination centres and effectors
• What is the function of a receptor?

  To detect and respond to specific stimuli.
• How does a stimulus lead to a response being carried out?

  • stimulus is converted into electrical impulses by receptors
  • these are passed along sensory neurones to the CNS.
  • the CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector
  • the effector carries out the response
• What sequence describes how the nervous system works?

  Stimulus -> receptor -> coordinator -> effector -> response
• What is a reflex action and why are they so important?

  A reflex action is an automatic, rapid response that does not involve the conscious part of the brain. They aid survival by preventing harm to the body.
• What is a synapse?

  A gap between neurones where chemicals diffuse to get across
• What and where is the cerebral cortex located?

  Near the front of the brain, it controls high level functions such as memory, speech and problem-solving
• What and where is the cerebellum located?

  At the back of brain, it controls motor skills such as movement, balance and coordination.
• What is the medulla?

  Part of the brainstem which controls unconscious actions such as heart & breathing rate, signals to adrenal glands to release adrenaline
• How can we investigate the brains functions?

  Via electrical stimulation or MRI scans
• What is electrical stimulations?

  Application of weak electrical currents to excite nerves or muscles
• What are MRI scans?


  Magnetic Resonance Imaging scans to see detailed images of the brain
• What are the risks of investigating the brains functions?

  Due to the delicacy of the brain, investigating and treating it can be difficult
• What is accomodation?


  The alteration of the lens' shape in order to focus on near or distant objects
• What happens when we focus on far objects?

  Ciliary muscles relax, suspensory ligaments tighten and lens becomes thin
• What happens when we focus on near objects?

  Ciliary muscles contract, suspensory ligaments loosen and lens becomes thick.
• What is myopia and how can it be treated?

  Short sightedness as a result of lens being too curved causing images to appear blurry. Can be treated by concave lenses.
• What is hyperopia and how can it be treated?

  Long sightedness as a result of lens being too flat. Images appear out of focus. It can be treated by convex lenses.
• What is the retina?

  The retina is the light-sensitive layer of tissue at the back of the eye that contains photoreceptor cells.
• What is the optic nerve?


  The optic nerve is a bundle of nerve fibers that carries visual information from the eye to the brain.
• What is the sclera?

  The white tough outer layer of the eyeball.
• What is the cornea?

  Curved transparent outer layer of the eye that allows light in the eye.
• What is the iris?

  The iris controls the size of the pupil by contracting or relaxing its muscles
• What do ciliary muscles and suspensory ligaments do?

  Hold the lens in place and control its shape
• What is thermoregulation?


  The process of maintaining a stable internal body temperature.
• What happens when were too hot?

  • Sweat glands produce sweat which evaporate and cool us down
  • Vasodilation: blood vessels dilate to increase blood flow to the skin to increase the rate of heat loss
• What happens when were too cold?

  • Shivering: muscles produce more heat
  • Hair stands up to trap air and act as insulation
  • Vasoconstriction: blood vessels contract to reduce heat loss
• What is the endocrine system?

  A system of glands that produce and secrete hormones into the bloodstream to regulate various bodily functions.
• What glands are in the endocrine system?

  Pituitary: referred to as the 'master' gland as it sends signals to other glands

  Thyroid: Controls growth, metabolism and more

  Pancreas: Secretes insulin to control blood sugar

  Adrenal glands: produces adrenaline

  Ovaries: produces oestrogen and release eggs

  Testes: produces sperm
• How do we control our blood sugar levels?

  Via a negative feedback system.

  If we have high blood glucose levels: Pancreas secretes insulin which causes glucose to move from the bloodstream into cells for respiration and excess glucose is converted into glycogen

  If we have low blood glucose levels: Pancreas secretes glucagon which causes liver and muscles to convert glycogen back into glucose
• What is Type 1 diabetes?

  A disorder where there is low-insulin production. It affects children and teenagers and is controlled by taking insulin daily. Symptoms can be extreme feeling of thirst, frequent urinating and very tired. It causes abnormal genes, attacks cells in pancreas and the body breaks down its own fat
• What is Type 2 diabetes?

  A disorder caused by poor lifestyle diet. Its common in obese people or people over 40. The body no longer responds to insulin in this type. Symptoms can be weight loss & loss of muscle bulk. It causes excessive body weight and the body is unable to produce insulin effectively
• How is water lost in the body?

  Through exhalation, urinating and sweating
• How is excess water removed?

  Its removed by kidneys to the bladder
• What is in urea?

  Ammonia from amino acids obtained from excess protein break downs in the liver
• What happens when we have too much water?

  Water moves in via osmosis and cells become turgid, meaning they could burst
• What happens when we have too little water?

  Water moves out via osmosis leading to cells becoming flaccid