Homeostatis ans Response

• What is homeostasis?

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

  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 sensory neurons?

  They transmit impulses to the CNS
• What is the role of motor neurons?

  They send impulses to effectors
• 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 cerebral cortex responsible for?

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

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

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

  • Complex and delicate structure
  • Easily damaged
  • Drugs may not reach the brain
  • Unclear functions of brain regions
• How do neuroscientists study brain function?

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

  Layer of light-sensitive cells in the eye
• What is the function of the optic nerve?

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

  White outer layer of the eye
• What does the cornea do?

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

  Muscles contract or relax to adjust size
• 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 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
• Where is the thermoregulatory centre located?

  In the brain
• What happens when body temperature is too high?

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

  Sweating stops and shivering occurs
• What mechanisms control body temperature?

  • Sweating and vasodilation for high temperature
  • Shivering and vasoconstriction for low temperature
  • Hairs standing on end for insulation
• What are hormones?

  Chemical messengers in the body
• What is the role of the pituitary gland?

  It is the master gland secreting hormones
• What hormone does the pancreas secrete?

  Insulin
• What does thyroxine control?

  Metabolic rate, heart rate, and temperature
• What hormone does the adrenal gland secrete?

  Adrenaline
• What is the function of oestrogen?

  Involved in the menstrual cycle and female traits
• What hormone do the testes secrete?

  Testosterone
• What is the role of testosterone?

  Involved in sperm production and male traits
• How does the hormonal system compare to the nervous system?

  It is slower but acts for longer