Lecture: Physiology 3: Introduction to physiology Flashcards
What is homeostasis?
Regulation of a constant internal environment through the process of positive and negative feedback.
What is negative feedback?
Negative feedback control systems respond when conditions change from the ideal or set point and returns conditions to this set point.
What are examples of negative feedback?
Examples: temperature control, blood pressure regulation, rate of metabolism, and blood sugar regulation.
What is positive feedback?
Feedback system that causes an increase in the original stimulus and intensifies its effect.
What are examples of positive feedback?
Examples: childbirth, ovulation, blood clotting, and lactation.
What limits feedback?
Feedback is limited at the capacity of the system/body
What are the key components of a feedback system?
- Event that triggers a perturbation away from normal
- Receptors to sense stimuli
- Control centre to make appropriate decision and send commands
- Effectors to respond and to bring back the value of the variable to the normal level
What are receptors?
Components that monitor the environment and senses a stimulus (detects the change in the ideal value).
What is the control centre?
Component that determines the ideal range for the value of the variable. According to the set value, the control centre then makes appropriate decisions and sends commands (signals) to the effectors.
What are effectors?
Components that receive signals from the control centre and try to bring back the value of the variable to the normal level.
What is a physiological example of pressure in medicine?
Expansion of lungs, when thoracic wall expands, creates a negative pressure between the pleural membranes.
What is a pathophysiological example of pressure in medicine?
Pneumothorax; caused when air or gas is present in the pleural cavity as a result of trauma or barotrauma (SCUBA).
What is a physiological example of force in medicine?
According to Starling’s Law, the more you fill the heart’s ventricles, the more it pumps out, and with greater force, due to the stretching of the heart muscle cells.
What is a pathophysiological example of force in medicine?
Dilated cardiomyopathy; causes the heart chambers to expand and weaken so the ventricles cannot contract enough or generate enough force thus they decrease the movement of blood around the body.
