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.
The thermoregulatory system is an example of what feedback system and its fxn
maintains body temperature near 37º, negative feedback
A reference selector or comparator in a control system
a)
a
