Lecture 1 Flashcards
Define control and give example
The action of a system on the responses that oppose perturbations e.g. body core temperature is REGULATED thru the CONTROL of heat released from macronutrients
Define regulation
The maintaining constant of a variable in the milieu intérieure (internal environment). The main property of a regulatory system is that a deviation of the regulated variable triggers a correcting response that opposes the deviation
How can ACS be modelled? What does this allow us to do?
• These control systems are modeled using
mathematics
• Equations are often fit to existing
biological data & subsequently are useful
in making predictions
• Understanding biological control systems
allows us to mimic them (e.g. Artificial
Organs)
Define system
• A system - a set of components that interact in such a way as to form a complete behaving or functioning unit
Define a control system
A set of components that regulates a system or systems
- > gives an OUTPUT in response to an INPUT
- > can accept varying INPUTS & produce the appropriate OUTPUT
Define open loop control system and give example
- control of system is independent of the output of the system
- e.g. driving with your eyes closed
Define closed loop control system and give example? ANOTHER NAME?
- control of system is dependent of the output of the system also known as (a.k.a.) feedback control system (FCS)
- e.g. driving with your eyes open
Fxn of reference selector
- compares actual output with the input signal and generates an error (actuating) signal as difference between desired and actual signal
- control system then acts on the actuating signal to produce an output close to the desired output
What is negative feedback control?
occurs when the output of a system acts to oppose changes to the input of the system
What is positive feedback control?
A mechanism in a system that monitors performance inputs rather than outputs, and reacts so as to maintain a specified state, thus preventing or minimizing problems before they occur. e.g. cooling of the skin can start a shivering response
thus minimizing the need for shivering
Define regulator and provide example
- type of FeedbackCS where a constant steady state input gives a constant output
e. g. CV system is a regulator which maintains constant BP in blood vessels
BP control system is an example of what feedback system
Negative feedback system
Another name for positive feedback
Cumulative causation
Is a system undergoing positive feedback stable?
• A system undergoing positive feedback is unstable. It will tend to spiral out of
control as the effect amplifies itself.
Example of a positive feedback system
e.g. contractions in childbirth. When a contraction occurs, the hormone oxytocin is
released into the body, which stimulates further contractions. This results in
contractions increasing in amplitude and frequency.
