Homeostasis and 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 nervous and hormonal communication play in homeostasis?

  They detect changes and respond automatically
• 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 from receptors
• What are effectors in homeostasis?

  Muscles or glands that respond
• What is the role of the nervous system?

  Allows reaction to surroundings and coordinates actions
• What do receptor cells convert into an electrical impulse?

  A stimulus
• How does an electrical impulse travel in the nervous system?

  Along sensory neurons to the CNS
• What happens in the CNS after receiving an impulse?

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

  Sending impulses to effectors
• What are reflexes?

  Automatic responses before conscious thought
• 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 is the function of synapses?

  Gaps between two neurons
• What happens when an impulse reaches the end of a neuron?

  A chemical is released into the synapse
• How does the chemical in the synapse affect the next neuron?

  It triggers the impulse to begin again
• 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?

  Bottom/back of the brain
• What does the medulla control?

  Unconscious actions like breathing
• 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 map brain regions?

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

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

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

  Supports the structures inside the eye
• What does the cornea do?

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

  Muscles contract or relax to alter 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
• What happens to the lens when focusing on a near object?

  Ciliary muscles contract and lens thickens
• What happens to the lens when focusing on a distant object?

  Ciliary muscles relax and lens thins
• What is myopia?

  Short sightedness
• What causes myopia?

  The lens is too curved
• What is hyperopia?

  Long sightedness
• What causes hyperopia?

  The lens is too flat