Topic 5 - homeostasis

• 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 in the environment
• What is the function of coordination centres?

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

  Muscles or glands that bring about responses
• What is the primary function of the nervous system?

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

  Convert a stimulus into an electrical impulse
• How does an electrical impulse travel in the nervous system?

  Along sensory neurons to the central nervous system
• What happens in the central nervous system (CNS)?

  Information is processed and responses are coordinated
• What are reflexes?

  Automatic responses that occur without thinking
• What are motor neurons responsible for?

  Sending impulses to effectors
• Why are reflexes important?

  They prevent individuals from getting hurt
• 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
• What happens when an impulse reaches the end of a neuron?

  A chemical is released into the synapse
• What does the chemical released in the synapse do?

  Triggers the impulse to begin in the next neuron
• How is reaction time measured?

  With 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?

  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?

  • The brain is complex and delicate
  • It is easily damaged
  • Drugs cannot always reach the brain
  • Its functions are not fully understood
• How do neuroscientists map brain regions?

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

  Contains light-sensitive cells that create images
• What is the sclera?

  White outer layer that supports the eye
• What is the function of the optic nerve?

  Carries impulses from the retina to the brain
• What is the function of the iris?

  Controls the size of the pupil
• What does the cornea do?

  Bends and focuses light onto the retina
• How does the pupil react in dim light?

  Circular muscles relax, radial muscles contract
• What is accommodation in the eye?

  • Focusing on near objects: ciliary muscles contract, suspensory ligaments loosen, lens thickens
  • Focusing on distant objects: ciliary muscles relax, suspensory ligaments tighten, lens thins
• What is myopia?

  Short sightedness where distant objects appear blurry
• What is hyperopia?

  Long sightedness where near objects appear blurry
• 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 shape
  • Replacement lens: artificial lens for hyperopia
• Where is the thermoregulatory centre located?

  In the brain
• What does the thermoregulatory centre monitor?

  The temperature of the blood
• What is the normal human body temperature?

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

  • Sweat is produced
  • Vasodilation occurs