Homeostasis and Response

• What is homeostasis?

  The regulation of internal conditions of a cell or organism.
• Why is homeostasis important for tissues and cells?

  It maintains optimum conditions for function in response to changes.
• What are the key internal conditions regulated by homeostasis?

  • Ion levels
  • Blood glucose concentration
  • Body temperature
  • Water levels
• What happens if ion levels are too high?

  It can damage cell functions.
• How does blood glucose concentration affect energy levels?

  Too much glucose can stop catalysing.
• What is the effect of body temperature on enzymes?

  It affects their activity.
• What can happen if there is too much water in the body?

  It can cause cells to burst.
• Which parts of the body are involved in homeostasis?

  • Kidneys: Regulate water and ion concentration
  • Skin: Regulates body temperature
  • Liver and Pancreas: Regulate blood glucose levels
  • Brain and spinal cord: Carry electrical impulses
• What are the two automatic control systems involved in homeostasis?

  Nervous system and endocrine/hormonal system.
• What are the components of control systems in homeostasis?

  • Receptors: Detect stimuli
  • Coordination centres: Process information
  • Effectors: Bring about responses
• What is negative feedback in homeostasis?

  It brings levels back to normal when they are too high or too low.
• What do effectors do in the nervous system?

  They are muscles or glands that bring about responses.
• What is the role of sensory neurons?

  They carry information from receptors to the CNS.
• What is the function of the CNS?

  It coordinates responses of effectors.
• What triggers the release of neurotransmitters at a synapse?

  An electrical impulse arriving at the synapse.
• What is a reflex arc?

  • Pathway of information from receptor to effector
  • Involves sensory neurons, relay neurons, and motor neurons
• What happens to neurotransmitters after they bind to receptors on the postsynaptic neuron?

  An enzyme breaks them down for recycling.
• What is the purpose of reflex actions?

  To provide automatic and rapid responses to stimuli.
• What is reaction time?

  The time it takes to respond to a stimulus.
• What is the method for investigating reaction time?

  1. One student holds a ruler vertically.
  2. The other student catches it without warning.
  3. Record the measurement above the thumb.
  4. Repeat multiple times.
  5. Change the independent variable (e.g., distraction).
• What factors can affect reaction time?

  • Age
  • Gender
  • Drugs
• What is the control variable in the reaction time experiment?

  The same hand, person, and ruler used.
• What is the independent variable in the reaction time experiment?

  Whether or not the student is distracted.
• What is the dependent variable in the reaction time experiment?

  The reaction time measured.
• How does reaction time change with distraction?

  It decreases as distraction increases.
• What are the main regions of the brain and their functions?

  • Cerebrum: Muscle coordination and balance
  • Medulla: Controls unconscious activities (heartbeat, breathing)
  • Cerebral cortex: Controls consciousness, intelligence, memory, and language
• What methods are used to study the brain?

  • Analysing brain damage
  • Electrical stimulation
  • MRI scans
• What are the ethical issues in studying brain disorders?

  Patients with severe brain damage cannot provide consent.
• What is the role of the sclera in the eye?

  It is a tough, supporting outer coating that protects the eye.
• What is the function of the cornea?

  It is the transparent outer layer that refracts light into the eye.
• What do ciliary muscles do in the eye?

  They control the shape of the lens.
• What is the role of the optic nerve?

  It carries impulses from the retina to the brain.
• What is the process of accommodation in the eye?

  • To focus on a near object:
  • Ciliary muscles contract
  • Suspensory ligaments loosen
  • Lens becomes thicker
  • To focus on a distant object:
  • Ciliary muscles relax
  • Suspensory ligaments tighten
  • Lens becomes thinner
• What is hyperopia?

  Long sightedness where near objects cannot be focused.
• How can hyperopia be corrected?

  Using glasses with a convex lens.
• What is myopia?

  Short sightedness where distant objects cannot be focused.
• How can myopia be corrected?

  Using glasses with a concave lens.
• What are the treatments for vision defects?

  • Contact lenses: Thin lenses on the eye's surface
  • Laser eye surgery: Changes the shape of the cornea
  • Replacement lens surgery: Inserts an artificial lens
• What is the optimum body temperature for enzymes?

  37°C
• How is body temperature monitored?

  By the thermoregulatory centre in the brain.