Homeostasis and Response

• What is homeostasis?

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

  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 nervous and hormonal communication play in homeostasis?

  They are involved in automatic control systems
• What are the components of control systems in homeostasis?

  • Receptors: detect stimuli
  • Coordination centres: process information
  • Effectors: bring about responses
• What are receptors in the context of homeostasis?

  Cells that detect stimuli
• What is the function of coordination centres?

  Process information received from receptors
• What are effectors in homeostasis?

  Muscles or glands that bring about responses
• How does the nervous system help us react to stimuli?

  It coordinates actions in response to stimuli
• What do receptor cells convert a stimulus into?

  An electrical impulse
• What travels along sensory neurons?

  The electrical impulse from receptors
• What happens in the central nervous system (CNS) after receiving an impulse?

  Information is processed and response coordinated
• What are motor neurons responsible for?

  Sending impulses to effectors
• What is the role of effectors in the nervous system?

  Carry out the response to stimuli
• What are reflexes?

  Automatic responses before conscious thought
• Why are reflexes important?

  They prevent individuals from getting hurt
• What is a reflex arc?

  A pathway for quick reflex responses
• What are the steps in a reflex arc?

  1. Stimulus detected by receptors
  2. Impulses sent along a sensory neuron
  3. Impulse passes to a relay neuron in the CNS
  4. Impulses sent along a motor neuron
  5. Impulse reaches an effector for response
• What happens at synapses between neurons?

  A chemical is released to trigger the next impulse
• 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
  • Controls complex behaviour
  • Part of the central nervous system
• What are the components of the brain and their functions?

  1. Cerebral cortex: consciousness, intelligence, memory, language
  2. Cerebellum: fine muscle movement
  3. Medulla: unconscious actions (breathing, heart rate)
• Why is investigating brain function difficult?

  It is complex, delicate, and not fully understood
• How do neuroscientists map brain regions?

  1. Studying patients with brain damage
  2. Electrically stimulating different parts
  3. Using MRI scanning techniques
• What does the retina do?

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

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

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

  Allows light through and focuses it onto the retina
• What do the iris muscles do?

  Alter the size of the pupil in response to light
• How does the pupil size change in bright and dim light?

  • Bright light: circular muscles contract, radial relax
  • Dim light: circular muscles relax, radial contract
• What is the process of accommodation in the eye?

  To focus on a near object:

  • Ciliary muscles contract
  • Suspensory ligaments loosen
  • Lens becomes thicker and more curved

  
  

  To focus on a distant object:

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

  Shortsightedness due to a too-curved lens
• What is hyperopia?

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

  • Spectacle lenses: concave for myopia, convex for hyperopia
  • Contact lenses: similar function to glasses
  • Laser eye surgery: alters cornea thickness or curvature
  • Replacement lens: artificial lens for hyperopia
• Where is the thermoregulatory centre located?

  In the brain
• What does the thermoregulatory centre monitor?

  Body temperature
• What type of receptors does the thermoregulatory centre have?

  Temperature receptors
• How do skin receptors contribute to thermoregulation?

  They send impulses to the thermoregulatory centre
• What is the normal human body temperature?

  37.5 degrees Celsius