Homeostasis and Response

• What is Homeostasis?

  Homeostasis is the regulation of internal conditions of a cell or organism (In response to internal and external changes)
• What 3 things does Homeostasis control?

  Blood glucose concentration , body temperature and water and ion levels
• What are the 2 responses that are involved in systems that control things in Homeostasis?

  Responses using nerves and Chemical Responses using hormones
• What are the 3 things that are in all control systems?

  Receptors, Coordination centres and Effectors
• What is are receptors?

  They are cells that detect stimuli (changes in the environment)
• What is the role of coordination centres?

  They receive and process information from the receptors
• What are effectors?

  They are muscles or glands that bring about responses that restore optimum levels
• What are some examples of coordination centres?

  The brain , pancreas and spinal cord
• What is the control mechanism that links receptors, effectors and coordination centres together?

  negative feedback
• What temperature should the human body be kept at and Why?

  37 degrees Celsius. This is the optimum temperature for enzymes to work
• What is the role of the thermoregulatory centre in the brain?

  It monitors/controls body temperature and receives information in the form of impulses from temperature receptors in the skin
• Why does the thermoregulatory centre have in the brain have receptors?

  To monitor the temperature of the blood flowing through the brain
• What are the 2 mechanisms that cause a transfer of energy from the skin to the environment when your body temperature is too high?

  Vasodilation (Widening of blood vessels) and more sweat is produced and evaporates
• Why does vasodilation occur when the body temperature is too high ?

  To direct more blood to the surface of the skin
• Why does vasoconstriction occur when the body temperature is too low ?

  To direct less blood to the surface of the skin
• What is shivering?

  Where the skeletal muscles uncontrollably relax and contract quickly
• Why do humans shiver when the temperature is too low?

  Shivering transfers more heat to the blood
• Why do blood vessels in the skin narrow and widen?

  Narrowing or widening is the only way they can adjust how much energy is transferred to the environment - They cannot move
• What is the purpose of the nervous system?

  It enables humans to react to their surroundings
• What is the role of the Central Nervous System?

  It coordinates the response of the effectors (e.g. muscles contracting)
• Why are reflex actions automatic and rapid?

  To protect the body
• What are synapses?

  Gaps between neurones
• Describe how an electrical impulse is generated from one neurone to the next?

  The electrical impulse reaches the synapse. Then, a chemical diffuses across the gap and causes the electrical impulse to be generated
• What does the brain control?

  Complex behaviour
• What is the brain made out of?

  Billions of interconnected neurones
• What are the 3 main regions of the brain that carry out different functions?

  Cerebral cortex, the cerebellum and medulla
• What does the cerebral cortex control?

  It controls consciousness and memory
• What does the cerebellum control?

  It controls movement and balance
• What does the medulla control?

  It controls automatic actions such as heartbeat and breathing
• What are the 3 ways scientists have been able to map the brains regions?

  Studying patients with brain damage, using MRI scanning techniques and electrically stimulating parts of the brain
• Why is investigating and treating brain disorders difficult?

  The brain is complex and delicate
• What is the purpose of the retina?

  Contain receptor cells (They are sensitive to brightness and colour of light)
• What is the role of the optic nerve?

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

  A tough outer layer of the eye
• What is the cornea?

  A transparent region at the front of the eye
• What are the 2 roles of the iris?

  It controls the size of the pupil. And it controls the amount of light that reaches the retina
• What do the ciliary muscles and the suspensory ligaments do?

  They change the shape of the lens to focus light on the retina
• What is accommodation?

  It is changing the shape of the lens to focus on near or distant objects
• What 3 things happen when the eye focuses on a NEAR object?

  The ciliary muscles contract, the suspensory ligaments loosen and the lens becomes thicker
• What does the lens do after it becomes thicker to focus on a near object?

  It refracts light rays strongly