Unit 1.1 communciation and Homeostasis (part 1)

  • This is mostly about the basics of homeostasis and temperature regulation.
  • I am writing these up in chunks so there isn't too much to abosrb at once...
  • this is most useful if you are on the OCR course but should be useful in other exam boards.
  • Next section will be: Neurons
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Preview of Unit 1.1 communciation and Homeostasis (part 1)

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Need for communication
Stimulus: Any change in the environment that causes a response.
Response:A change in behaviour or physiology as a result of a change in the
environment.
External environment: could put stress on a living organisms, it must be
monitored to survive, provoking a response that is behavioural or
physiological.
Internal environment: Waste products produced by cells can be harmful to
the body and affects the internal environment. Tissue fluid maintained by
blood which transports waste for excretion and also maintains substrate
supply for cells
Coordination: Multicellular organisms have specialised cells that can be
found in different parts of the body but need to communicate in order to work
effectively and together.…read more

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Cell signalling and communication systems
Cell signalling: relies on chemical release,which is detected by another cell.
They respond accordingly.
Neuronal system: Neurones signal to each other over synaptic junctions,
this a rapid response, or short-term response.
Hormonal system: Blood transports the hormone around the whole body,
which has been released via the endocrine organ, but is only recognised by
specific target cells. This is a long-term response.
A good system will... Cover the whole body, enable all cells to
communicate,enables rapid communication, enable both long-term and short-
term communication…read more

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Positive and negative feedback
Homeostasis: Keeping the internal environment constant despite external
changes.
Negative feedback: Brings out a reversal of a change in condition.
Positive feedback: Increases any change detected by the receptors (not
strictly about Homeostasis but you need to be aware of this).…read more

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Change away from Receptor detects
optimum change
Optimum System informs
condition Negative feedback effector
Return to optimum Effector reacts to
condition reverse change
Optimum Change away from Receptor detects
condition optimum change
Positive feedback System informs
effector
Effector reacts to
increase change…read more

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Maintaining body temp: ectotherms
Ectotherm: An organism that relies on external sources of heat to regulate its
body temperature.
Warming up:
Exposing body to sun allows more heat to be absorbed.
Orientating body towards sun exposes a larger surface area to allow more
absorption.
Altering body shape allows a larger surface area. Check out horned lizards.
Cooling down:
Orientation away from the sun.
Hiding from the sun... i.e. burrowing.
Altering body shape to decrease surface area
Increase breathing movements evaporates more water which aids cooling.…read more

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