Module 5.1 - Communication and Homeostasis 

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  • Module 5.1 - Communication and Homeostasis
    • Homeostasis - internal environments
      • Living organisms need to maintain a certain limited set of conditions within their cells
        • Allows for flexibility
      • Cellular actions rely on enzymes
      • specific set of conditions
        • suitable temperature + suitable pH + aqueous environments+no toxins/inhibitors
    • Stimulus
      • Any Changes in the environment that causes a responce
    • Response
      • A change in behaviour or physiology as a result of a change in the environment.
    • Internal Environments
      • animal cells and tissue fluid
      • Accumulation of excess waste acts as a stimulus to cause the removal of these products
      • Cell activity  alters its environment
        • use up stubstrates
        • produce products some of which may be toxic
    • Maintaining internal environments
      • tissue fluid composition is maintained by blood
      • waste in tissue fluid drains into the blood
      • excretion prevents accumulation
      • concentrations are maintained
    • coordination
      • cells (multi-cellular organisms) differentiate (specialised)  forming tissues/organs
      • Needs a good communication system
        • features:
          • covers the whole body
          • enables cell communication
          • rapid
          • specific
          • enables short-term & long-term responses
    • cell signalling
      • cell communication
      • used in neuronal system and horizontal  system
    • Homeostasis
      • maintaining a constant internal environment despite external changes
        • e.g. body temperature, blood glucose concentration, blood sate concentrations, blood pressure, water potential of blood and CO2 concentration
    • Negative Feedback
      • Reversal of any changes in the internal environment to return to the optimum state.
      • Detected by receptors
      • Communication system informs effectors
      • effectors react to reverse change
      • structures required:
        • Sensory receptors
        • communication system (hormonal/neuronal)
        • Effector cells (muscles)
    • Behavioural Adaptations
      • Too Hot
        • move into shade
        • increased surface area exposure
        • remain inactive
      • too cold
        • move into sunlight
        • extreme - cold
          • roll into a ball to decrease surface area
        • move about to generate heat in muscle
        • decrease exposed surface area
    • Temperature regulation in ectotherms
      • increasing the heat exchange with their environments
        • orientate body to sun
        • Expose body to sun
        • orientate body away from the sun
        • Hide in a burrow
        • alter body shape
        • increase breathing rate
      • E.g. a lizard
        • A drop in internal body temperature means they move to expose their body to warmer places in the sun
        • when their temperature increases they move somewhere cooler like a burrow in the sand
    • Ectotherms
      • Body temperature fluctuates with external temperature
      • Advantages
        • Need less food
        • Greater proportion of energy used for growth
        • Use less food in respiration
      • Disadvantages
        • may not be capable of activity during winter months
        • less active during cooler temperatures
    • Positive Feedback
      • Increases changes detected by receptors
      • Does not lead to homeostasis
      • e.g. hibernation
        • core temperature drops
      • e.g. dilation of the cervix at the end of pregnancy
      • optimum condition
        • change away
          • receptors detect change
            • communication system informs effects
              • efectors react to increase change
          • efectors react to increase change
    • Endotherms
      • Maintain body temperature within strict limits
      • independent of external temperature
    • Examples of negative feedback
      • control of room temperature
      • control of body temperature
      • control of blood glucose levels
      • control of body water concentrations
    • Physiological adaptations - endotherms
      • too cold
        • sweat glands secrete less, you don't pant, the hairs on your skin are raised, arterioles vasoconstrict, liver cells increase metabolism and skeletal muscles spontaneously combust (shiver)
      • too hot
        • sweat glands secrete more sweat, you pant the hairs on your skin lie flat, arterioles vascodilate and the liver cells reduce the rate of metabolism
    • Controlling Body Temp by Negative Feedback
      • thermoregulatiory centre in hypothalamus detects change
      • nervous and hormonal systems carry signals to skin,liver and muscles
        • fall in core temperature
          • rise in metabolic reactions
          • release more heat from exergonic reactions
          • release heat through muscle contractions
          • Decrease loss of heat, temp
    • Detecting changes in body temperature
      • Peripheral temperature receptors
        • "early warning" system
        • detect changes in temperature of the extremities
        • sends signals to the brain to initiate behavioural mechanisms to maintain core temperature
      • thermoregularory centre in the hypothalamus
        • monitors blood temperature
        • detects changes in core temperature
    • Endotherms
      • Uses internal sources of heat to maintain body temperature
      • many chemical reactions in the body are exergonic
        • Exergonic = releases energy (e/g/ respiration)
      • Advantages
        • consistent body temperature
        • activity possible even when cool
        • inhibit colder parts of the planet
      • they show behavioural and phsyiological adaptations
      • Disadvantage
        • energy used up to maintain constant temperature
        • More food required
        • less energy used in growth

Comments

RebeccaSmithySmith

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Hey all, it doesn't appear to print properly so my apologies for that and I don't really know to correct it, but I don't know whether it's just me or not. 

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