Biology Homeostasis

• What is homeostasis?

  Regulation of internal conditions in an organism for optimal function in response to internal/external changes
• What 3 things does homeostasis control in humans?

  • Blood glucose levels
  • Temperature
  • Water content
• How is homeostasis achieved automatically?

  By control systems
• What three things do all control systems have and what are their roles?

  • Receptors: Cells in sense organs that detect stimuli
  • Co ordination centres: Link receptors to effectors and process info
  • Effectors: Bring about a response to change (Muscles/Glands)
• Give an example of co-ordination centres?

  • Brain
  • Spinal cord
  • Pancreas
• What is the function of the nervous system?

  Allows us react to our surroundings and coordinate actions in response to stimuli
• How does the nervous system work?

  • Receptor cells detect stimuli and covert it into electrical impulse sending it to the CNS via neuron
  • Info is processed in CNS and electrical impulse is sent to effectors via relay neuron
  • Impulse is sent along motor neuron which effector contract/secrete hormone
• What are automatic responses?

  Ones that take place without you thinking and prevent you from getting hurt as they don't involve conscious part of Brain
• What is the pathway of the reflex arc?

  • Stimulus detected by receptors
  • Impulse passes down sensory neuron to relay neuron in CNS
  • CNS sends impulse to effectors via relay neuron to motor neurone
  • Impulse reaches effector resulting in appropriate response
• Example of reflex arcs?

  Moving hand away from hot surface

  Pupils constricting in a high light to avoid damage
• What are the adaptations of neurons?

  • Long
  • Thin
  • Many branched connections on either end

  This is to connect one place in body to the other
• How does one neuron trigger electrical impulse in another?

  Through synapses as chemicals diffuse from one neuron to another
• What is reaction time and how is it measured?

  • How long it takes you to respond to stimuli measured using ruler drop test
• What is the brain made up of + function

  Has many interconnected neurons and controls complex behaviour
• What are the three important parts of the Brain?

  • Cerebral Cortex
  • Cerebellum
  • Medulla
• What is the function of cerebral cortex?

  • To control higher brain functions

  Language, thought and intelligence
• What is the function of cerebellum?

  • Controls muscle contractions to help with balance and control of body
• What is the function of the medulla?

  Controls unconscious functions like breathing and heart rate
• What ways can the brain be studied?

  • Studying people with brain damage
  • Electrically stimulating different parts of the brain
  • Using scans like MRI
• What are the problems with studying the brain?

  • Ethical issues in studying people with brain damage
  • Brain is hard to access as its inside skull so we can't see/treat it
  • Complex and delicate ( we don't know all its functions)
  • Some drugs don't reach brain due to membrane coating it

  However using electrical stimulation helps diagnose disorders like epilepsy
• What is the function of the Eye and its structure?

  • Sense organs with receptor cells sensitive to light and colour

  The functions are;

  • Accommodation to focus on near/distant objects
  • Adaptation to bright/dim light
• What are the 7 structures of the eye?

  • Cornea
  • Cilliary muscles
  • Retina
  • Pupil
  • Optical nerve
  • Sclera
  • Iris
  • Suspensory ligaments
• What's the function of the cornea and Iris?

  Cornea: Allows and refracts light passing through

  • It is transparent with no blood vessels

  Iris: Controls how big/small pupil is
• What is the function of the optic nerve and sclera?

  • Optic nerve: Carries electrical impulse from eye to brain
  • Sclera: White layer that covers eyeball
• What is the function of retina

  • Retina: Has receptor cells that detect colour and intensity of light
• What is the function of ciliary muscles and suspensory ligaments?

  Holds lens in place and contracts to change its shape
• What is the process of accommodation to focus on a near object?

  • Cillary muscles contract
  • Suspensory ligaments relax
  • Lens is thicker and more curved refracting light more
• Name two eye defects

  -Myopia: nearsightedness....Lens is too curved so distant objects look blury

  -Hyperopia: Lens is too flat so doesn't refract light enough
• What are the treatments of the defects?

  • Concave lenses for myopia (spreads light out) Convex lenses for hyperopia (focuses light)
  • Laser eye surgery to reduce thickness of lens or change curvature
  • Replacement lenses but this can lead to cataracts forming