Homeostasis and response

• What is homeostatis?

  regulation of internal conditions of the body
• What does homeostasis respond to?

  external and internal changes
• Why is homeostasis important?

  it keeps conditions constant for enzyme action and cell functions
• What does homeostasis control in the body?

  blood glucose concentration

  body temperature

  water and ion levels
• What might control systems involve in homeostasis?

  responses using nerves

  chemical responses using hormones
• What do all control systems include?

  Receptors

  coordination centres

  effectors
• What is the role of receptors?

  detect stimuli
• What do coordination centres do?

  receive and process info from receptors
• What is the role of effectors?

  bring about responses that restore optimum levels
• Why must the body be kept at around 37 degrees?

  Optimum temperature for enzymes to work
• What is one function of the thermoregulatory centre in the brain?

  monitors and control body temperature
• What happens if the body temperature is too high?

  Vasodilation
• What happens if the body temperature is too low?

  vasoconstriction
• What occurs during vasoconstriction?

  blood vessels narrow/constrict, less blood flow to surface of skin, sweating stops, skeletal muscles contract (shiver)
• What happens during vasodilation?

  blood vessels dilate/widen, more blood to surface of skin, more heat loss, more sweat produced
• What does the nervous system enable us to do?

  React to their surrounding and coordinate behaviour
• Where does information go after receptor cells?

  Central nervous system
• What is the CNS composed of?

  brain and spinal cord
• What does the CNS coordinate?

  response of the effectors
• What are reflex actions?

  automatic and rapid
• Why do we need reflex actions?

  to protect the body
• Do reflex actions involve the conscious part of the brain?

  no
• How do neurones communicate?

  synapses (as not directly connected)
• What are synapses?

  gaps between the neurones
• What type of behaviour does the brain control?

  Complex
• What is the brain made of?

  billions of interconnected neurons
• What are the 3 main regions of the brain?

  Cerebral cortex, cerebellum, medulla
• How have neuroscientists been able to map the regions of the brain to functions?

  -studying patients with brain damage

  -electrically stimulating parts of the brain

  -using MRI scanning
• Why is treating brain disorders difficult?

  the brain is very complex and delicate
• What type of organ is the eye?

  sense
• What does the retina contain?

  receptor cells
• What are the receptors cells in the brain sensitive to?

  brightness and colour of light
• What does the optic nerve do?

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

  tough outer layer
• What is the cornea?

  transparent membrane, covers eyeball
• What does the iris do?

  control size of pupil and light reaching retina
• What do the ciliary muscles and suspensory ligaments do?

  Change shape of lens to focus light onto retina
• What is accomodation?

  process of changing shape of lens to focus on near/distant objects
• Why are the eye defects myopia and hyperopia caused?

  rays of light not focussing on retina
• What is the name for short sightendness?

  myopia