homeostasis and response

• What is homeostasis?

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

  It is needed for enzyme action and all cell functions
• What are the three main factors controlled by homeostasis 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 that detect changes and respond to them
• 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 (changes in the environment)
• What is the function of coordination centres in homeostasis?

  They process the information received from the receptors
• What are effectors in the context of homeostasis?

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

  It allows us to react to our surroundings and coordinate actions in response to stimuli
• How do receptor cells function in the nervous system?

  They convert a stimulus into an electrical impulse
• What happens to the electrical impulse after it is generated by receptor cells?

  It travels along sensory neurons to the central nervous system (CNS)
• What occurs in the CNS after the electrical impulse arrives?

  The information is processed and the appropriate response is coordinated
• What do motor neurons do in the nervous system?

  They send an electrical impulse to effectors
• What are reflexes?

  Automatic responses that occur before you have time to think
• What is a reflex arc?

  1. A stimulus is detected by receptors
  2. Impulses are sent along a sensory neuron
  3. In the CNS, the impulse passes to a relay neuron
  4. Impulses are sent along a motor neuron
  5. The impulse reaches an effector resulting in the appropriate response
• Why are reflexes important?

  They prevent the individual from getting hurt
• What are synapses?

  The gaps between two neurons
• What happens when an impulse reaches the end of the first neuron at a synapse?

  A chemical is released into the synapse
• What occurs after the chemical diffuses across the synapse?

  It triggers the impulse to begin again 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 is the role of the cerebral cortex?

  It controls consciousness, intelligence, memory, and language
• Where is the cerebellum located?

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

  Unconscious actions such as 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
  • It is not fully understood which part of the brain does what
• What methods do neuroscientists use to map brain regions?

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

  It contains light-sensitive cells that send impulses to the brain to create an image
• What is the optic nerve's role?

  It carries impulses from the retina to the brain
• What is the sclera?

  The white outer layer that supports the structures inside the eye
• What is the function of the cornea?

  It allows light through and bends it to focus on the retina
• What happens to the pupil in dim light?

  • Circular muscles relax
  • Radial muscles contract
  • Pupil becomes larger to allow more light in
• What do the iris muscles do?

  They contract or relax to alter the size of the pupil
• What happens to the pupil in bright light?

  • Circular muscles contract
  • Radial muscles relax
  • Pupil becomes smaller to avoid damage to the retina
• What is accommodation in the eye?

  • The process of changing the shape of the lens to focus on near or distant objects
• What occurs to the lens when focusing on a near object?

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

  • Ciliary muscles relax
  • Suspensory ligaments tighten
  • Lens becomes thinner
• 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
  • Contact lenses
  • Laser eye surgery
  • Replacement lens
• What is the thermoregulatory centre?

  The part of the brain that monitors and controls body temperature