communication and homeostasis

• requirements of a good communication system

  • extend over whole body
  • send and receive messages and signals
  • specific and rapid
  • long and short term
• stimulus is a change in the environment that causes a response in the body
• response is a change in behaviour or physiology as a result of change in the environment
• respond to external stimuli to keep themselves safe
• respond to internal stimuli to remain at homeostasis
• behavioural responses to external stimuli

  • hibernation
  • migration
  • courtship
• physiological responses to external stimuli

  • shivering
  • sweating
• homestasis is the maintenance of the internal environment in a constant state despite the changes in external and internal factors
• dynamic equilibrium is when a steady state is remained
• homeostasis corrects any deviation away from the optimum to keep conditions within a narrow range in which enzymes can function
• negative feedback

  1. stimulus detected by a receptor (chemoreceptor, baroreceptors, stretch)
  2. communication pathway - neuronal or hormonal
• glucose regulation as an example of negative feedback

  • stimulus - blood sugar levels
  • receptor - pancreas
  • communication pathway - hormonal
  • effector - liver
• positive feedback is the a process that increases any change detected by receptors against homeostasis
• hypothermia as an example of positive feedback

  1. below a certain temp enzymes become less active
  2. body cools further
• examples of positive feedback

  • platelet activation in blood clotting
  • action potential generation
  • hypothermia
• ectotherms rely on external sources of heat to regulate their body temperature
• advantages of ecotherms

  • use less of their food in respiration
  • find less food
  • greater energy for growth
• disadvantages of ecotherms

  • less active in cooler temps
  • greater risk of predation
  • must hibernate
• ecotherms example behaviours

  • sweating
  • shivering
  • flying
  • hibernating
  • breathing
• endotherms are organisms that use internal sources of heat such as metabolic reactions in respiration to maintain its body temperature
• exergonic reactions release heat energy
• advantages of an endotherm

  • active at all times of the day
  • ability to inhibit colder areas of the world
• disadvantages of endotherms

  • more food required
  • less growth
• how do endotherms regulate their temperature

  • role of hypothalamus - monitors blood temp
  • role of peripheral temp receptors - skin detects change in temps
• physiological mechanisms to maintain body temperature

  • sweat glands in skin
  • mouth and nose - animal panting
  • hairs on skin - relax if hot, erect if cold
  • aterioles - vasodilation, vasoconstriction
  • skeletal muscles - rapid contraction, shivering