Homeostasis + 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 in the environment
• What are coordination centres in the body?

  Brain, spinal cord, and pancreas
• What do effectors do in homeostasis?

  Bring about responses to restore optimum conditions
• What is the function of the nervous system?

  To react to surroundings and coordinate actions
• What do receptor cells 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 after receiving an impulse?

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

  Sending impulses to effectors
• What are reflexes?

  Automatic responses that occur without thinking
• What is a reflex arc?

  A pathway for quick vital 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 are synapses?

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

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

  Triggers the impulse to begin in the next neuron
• How can reaction time be 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?

  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?

  • 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 parts of the brain
  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?

  The white outer layer of the eye
• What does the cornea do?

  Allows light through and focuses it on the retina
• What is the function of the iris?

  Controls the size of the pupil
• How does the pupil size change in bright light?

  • Circular muscles contract
  • Radial muscles relax
  • Pupil becomes smaller
• How does the pupil size change 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 to focus on a near object?

  • Ciliary muscles contract
  • Suspensory ligaments loosen
  • Lens becomes thicker and more curved
• What happens to the lens to focus on a distant object?

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

  Short sightedness
• What causes myopia?

  The lens is too curved for distant objects
• What is hyperopia?

  Long sightedness
• What causes hyperopia?

  The lens is too flat to refract light enough