5.1 Communication and homeostasis Flashcards
What is an effector?
A cell, tissue or argan that brings about a responce.
What is homeostasis?
Maintaining a constant internal enviroment despite changes in external and internal factors.
What is negative feedback?
The mechanism that reverses a change, bringing the system bacl to the optimum.
What is positive feedback?
The mechanism that increases a change, taking the system further away from the optimum.
What are sensory receptors?
Cells, sensory never endings that respond to a stimulus in the internal or external enviroment of an organism and can create action potentials.
What aspects may be maintained by homeostasis?
- Body temperature
- Blood glucose concentration
- Blood salt concentration
- Water potential in the blood
- Blood pressure
- Carbon dioxide concetration
For negative feedback to occur, what processes must occur?
- A change in the internal enviroment must be detected.
- The change must be signalled to other cells.
- There must be an effective responce that reverses the change in conditions.
Is positive or negative feedback more common?
Negative feedback is more common than positive feeback.
What is an example of harmful positive feedback?
When the core body temperature enzymes become less active and the exergonic reactions that release heat are slower and release less heat, allowing the body to cool further.
What is an example of benificial postive feedback?
At the end of preganancy, the cervix begins to stretch, causing the poterior putuitary gland to secrete the hormone oxycotin. Tjis increases the uterine contractions which stretch the cervix more so the baby can be born.
What conditions do exymes require to work effeciently?
- A suitable temperature
- A suitable pH
- An aqueous enviroment that keeps the substrates and products in solution
- Freedom from toxins and excess inhabitors
What are the two major systems of communication that work by cell siganlling?
- Neuronal system
- Hormonal system
What is an ectrothrem?
An oranism that relies on external sources of heat to maintain body temperature.
What is an endotherm?
An organism that uses heat from metabolic reactions to maintain body temperature.
What happens to enzymes if temperature is increased too high?
They denature, changoing their shape, loosing their function.