Communication and Homeostasis

• Communication Systems in Multicellular Organisms


  Systems that enable coordination and response to changes in both internal and external environments
• Importance of communication systems in multicellular organisms

  • Enable coordination among different organs essential for the organism's survival
  • Allow response to changes in both internal and external environments
• Communication systems in animals

  • Signalling the brain to initiate responses like vasoconstriction and shivering to conserve heat
• Communication systems in plants

  • Photoreceptor cells detecting changes in light intensity and triggering hormone production to regulate growth and development
• Cell Signalling


  The process by which cells communicate with each other to coordinate functions and respond to stimuli
• Signalling between adjacent cells

  • Through gap junctions allowing small molecules to pass directly from one cell to another
• Signalling between distant cells

  • Through release of hormones into the bloodstream to target cells with specific receptors
• Signalling between distant cells

  • Release of insulin by pancreatic cells regulating glucose levels in muscle and adipose tissue
• Mechanisms of cell signalling

  • Neuronal system transmitting electrical impulses across synapses
  • Hormonal system releasing chemical messengers into the bloodstream to target cells
• Rapid and long-term responses to stimuli

  Enabled by cell signalling mechanisms
• Receptors


  Detect deviations from optimal conditions and transmit information to control centres in the brain
• Effectors


  Muscles and glands that initiate responses to counteract deviations and restore homeostasis
• Receptors and effectors in the human body

  • Pancreatic cells releasing insulin or glucagon to regulate blood glucose levels
• Homeostasis


  The maintenance of a constant internal environment despite changes in external and internal factors
• Negative feedback mechanisms


  • Counter deviations from optimal conditions, e.g. temperature regulation through sweating and vasoconstriction
• Positive feedback mechanisms


  • Amplify deviations from normal conditions, leading to destabilisation, e.g. childbirth or blood clotting
• Temperature control in endotherms

  1. Peripheral temperature receptors detect changes

  2. Hypothalamus integrates sensory input and initiates responses

  3. Effectors in skin and muscles regulate heat production and loss
• Behavioural responses in ectotherms

  • Basking in the sun, seeking shade, adjusting body position to optimise heat gain or loss
• Physiological and behavioural responses in endotherms

  Allow for precise control of body temperature and activity in diverse environments
• Physiological and behavioural responses in ectotherms

  Allow for optimisation of heat gain or loss in the environment, but constrain activity levels and habitat range
• Endotherms have a high energy requirement for thermoregulation, which may limit resource allocation to growth and reproduction
• Ectotherms have lower energy expenditure on thermoregulation, allowing for more efficient resource allocation to growth and reproduction
• Ectotherms are constrained by environmental temperatures, with reduced activity and metabolic rates in colder conditions
• Body Temperature


  The internal temperature of an organism, typically around 37°C (98.6°F) for mammals and birds.
• Thermoregulation


  The process by which the body maintains a stable internal temperature despite changes in the environment.
• Endotherms


  Endotherms are animals that possess physiological mechanisms to control their internal body temperature (they can maintain their body temperatures using heat generated within their body tissues)
• Endotherm cooling systems


  Vasodilation

  Sweating

  Flattening of hairs
• Endotherm warming mechanisms


  • Vasoconstriction
  • Boosting metabolic rate
  • Shivering
  • Erection of hairs
• Structures in human skin involved in increasing or reducing heat loss