Coordination & control

• organisms respond to changes in environment (stimulus)
• a coordinated response requires stimulus, receptor, and effector
• homeostasis is the maintenance of constant internal environment
• a temperature of 37 (enzymes), water balance for osmoregulation, and glucose concentration are things that are homeostasised
• negative feedback loop:

  A) change

  B) corrective

  
• shivering is muscles rapidly contracting and relaxing to generate heat
• hair stands up to trap a layer of warm air to insulate, and happens because erector muscles in the skin contract
• when it's hot hair lies flat to trap less air
• respiration increases when you're cold because it generates heat
• sweating occurs because water in it evaporates, cooling the body
• when does vasodilation occur?

  when it's hot
• vasoconstriction loses to less heat lost due to the amount of blood flowing near skin being less.
• vasodilation allows for more heat loss as more of the blood is flowing near skin
• nervous vs. endocrine system:

  neurones vs. secretory cells

  electrical impulses vs. hormones

  nerve fibres (axons & dendrons) vs. blood plasma

  very quickly vs. more slowly

  short time vs. may last longer