Module 5.1 - Communication and Homeostasis
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- Created on: 07-12-18 14:40
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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
- Living organisms need to maintain a certain limited set of conditions within their cells
- 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
- features:
- 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
- maintaining a constant internal environment despite external changes
- 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
- Too Hot
- 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
- increasing the heat exchange with their environments
- 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
- communication system informs effects
- efectors react to increase change
- receptors detect change
- change away
- 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
- too cold
- 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
- fall in core temperature
- 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
- Peripheral temperature receptors
- 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
- Homeostasis - internal environments
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