Communication and homeostasis. Flashcards
What is meant by cell signalling?
The way in which cells communicate with each other
List what needs to be maintained in the body.
- Optimum body temperature (37°)
- Blood pH
- Blood glucose concentration
- Water potential in the blood
- Blood pressure
- Blood salt concentration
- Carbon dioxide concentration
Define homeostasis
Maintaining a constant internal environment despite changes in external and internal factors
What are the two systems of communication?
- Hormonal system
Uses the blood to transport signals with chemical messengers (hormones) - works on specific target cell and has longer lasting effects - Neuronal system
Neurones that communicate through electrical impulses
What is meant by an effector?
A cell, tissue or organ that brings about a response
Write out the response pathway
Stimulus —> Receptor —> Communication pathway (eg cell signalling) —> Effector —> Response
What do sensory receptors do?
They monitor changes in the external or internal environment to detect change.
If a change is detected they are stimulated and create action potential
What is negative feedback?
A feedback mechanism that reverses a change, counteracting and returning the system back to the optimum.
What is positive feedback?
A feedback mechanism that amplifies a change, taking the system farther away from equilibrium
Give an example of both negative and positive feedback
- Negative feedback: thermoregulation
- Positive feedback: oxytocin for labour contractions
What is the difference between an ectotherm and endotherm
- Ectotherm
An organism that relies on external sources of heat to maintain body temperature - Endotherm
An organism that uses heat from metabolic reactions to maintain body temperature
What do ectotherms do when they are too cold?
- Move into a sunny area
- Lie on a warm surface
- Expose a larger surface area to the sun
What do ectotherms do when they are too hot
- Move out of the sun
- Move underground
- Reduce the body surface exposed to the sun
