Homeostasis Flashcards
What is an effector?
A cell, tissue or organ that brings about a response.
Define homeostasis.
Maintaining a constant internal environment despite changes in external and internal factors.
What is negative feedback?
The mechanism that reverses a change, bringing the system back 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 nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials.
Give six aspects maintained by homeostasis.
Body temperature Blood glucose concentration Blood salt concentration Water potential of the blood Blood pressure Carbon dioxide concentration
What is the standard response pathway?
Stimulus -> receptor -> communication pathway (cell signalling) -> effector -> response
Give an example of a sensory receptor.
Temperature receptors.
Where are temperature receptors found in the body?
On the surface of the body (skin)
Temperature receptors in the brain
Give an example of a communication system in the body.
The neuronal system or the hormonal system.
How do the communication systems work?
By signalling between cells.
The messages from the receptor to the coordination centre are known as what?
The input
What are the messages sent to the effectors calls?
The output
Give examples of effectors.
Liver cells
Muscle cells
Where is the coordination centre usually?
In the brain.
Explain the flow diagram of negative feedback.
Change away from optimum -> Receptors detect change -> communication system informs effector -> effector reacts to reverse change -> return to optimum condition -> receptors detect a reduction in stimulus -> reduce the input to the coordination centre -> output from coordination centre to effectors reduces -> effectors reduce their activity.
For negative feedback to work what processes must occur?
A change to the internal environment must be detected.
The change must be signalled to other cells.
There must be an effective response that reverses the change in condition.
When is positive feedback used?
To stimulate an increase in change.
Give two examples of positive feedback.
Dilation of the cervix during labour due to the secretion of the hormone oxytocin.
The activity of neurones also relies on positive feedback.
What does oxytocin increase during labour?
The uterine contractions which stretch the cervix more.
