B5- Homeostasis and Response

• What is homeostasis?

  Maintenance of a constant internal environment
• Why is homeostasis necessary?

  It is needed for enzyme action and cell functions
• What does homeostasis control in the human body?

  • Blood glucose concentration
  • Body temperature
  • Water levels
• What role do receptors play in control systems?

  They detect stimuli in the environment
• What are coordination centres in the body?

  They process information from receptors
• What are effectors in the control systems?

  They bring about responses to restore conditions
• What is the function of the nervous system?

  To react to surroundings and coordinate actions
• How do receptor cells function?

  They convert a stimulus into an electrical impulse
• What is the pathway of an electrical impulse in the nervous system?

  From sensory neurons to CNS, then motor neurons
• What are reflexes?

  Automatic responses that prevent injury
• What is a reflex arc?

  1. Stimulus detected by receptors
  2. Impulses sent along sensory neuron
  3. Impulse passes to relay neuron in CNS
  4. Impulses sent along motor neuron
  5. Impulse reaches effector for response
• What are synapses?

  Gaps between two neurons
• How do impulses cross synapses?

  A chemical is released and diffuses across
• What is reaction time?

  Time taken to respond to a stimulus
• How can reaction time be measured?

  Using the ruler drop test
• What is the brain made up of?

  Many connected neurons
• What does the cerebral cortex control?

  Consciousness, intelligence, memory, and language
• Where is the cerebellum located?

  Towards the bottom/back of the brain
• What does the medulla control?

  Unconscious actions like breathing and heart rate
• Why is investigating brain function difficult?

  • Complexity and delicacy of the brain
  • Susceptibility to damage
  • Drugs may not reach the brain
  • Unclear functions of brain regions
• How do neuroscientists study brain function?

  By studying brain damage, stimulation, and MRI
• What does the retina do?

  Contains light-sensitive cells to create images
• What is the function of the optic nerve?

  Transmits impulses from the retina to the brain
• What is the sclera?

  White outer layer supporting the eye structures
• What is the role of the cornea?

  Allows and focuses light onto the retina
• How does the iris control pupil size?

  Muscles contract or relax to change size
• What happens to the pupil in bright light?

  • Circular muscles contract
  • Radial muscles relax
  • Pupil becomes smaller
• What happens to the pupil in dim light?

  • Circular muscles relax
  • Radial muscles contract
  • Pupil becomes larger
• What is accommodation in the eye?

  • Process of focusing on near or distant objects
  • Involves ciliary muscles and suspensory ligaments
• How does the eye focus on a near object?

  • Ciliary muscles contract
  • Suspensory ligaments loosen
  • Lens becomes thicker and more curved
• How does the eye focus on a distant object?

  • Ciliary muscles relax
  • Suspensory ligaments tighten
  • Lens becomes thinner
• What is myopia?

  Short sightedness due to a too curved lens
• What is hyperopia?

  Long sightedness due to a too flat lens
• What are the treatment methods for eye defects?

  • Spectacle lenses (concave/convex)
  • Contact lenses (hard/soft)
  • Laser eye surgery
  • Replacement lens
• What is the thermoregulatory centre?

  It monitors and controls body temperature
• What is the normal human body temperature?

  37.5 degrees Celsius
• What happens when body temperature is too high?

  • Sweat is produced
  • Vasodilation occurs
• What happens when body temperature is too low?

  • Sweating stops
  • Shivering occurs
  • Vasoconstriction occurs
• How do the mechanisms for temperature control work?

  • Sweating and vasodilation cool the body
  • Shivering and vasoconstriction warm the body
• What are the two communication systems in the human body?

  Nervous system and endocrine system