MEDI211 Lecture Notes - Lecture 1: Autonomic Nervous System, Proportional Control, Negative Feedback
Week 1 Lecture 1 – Control Theory
Lecture objectives:
1. To introduce students to control theory as it relates to homeostasis
2. Demonstrate an understanding of the different between physiological control and regulation
3. Describe the meaning and physiological significance of different forms of control, and
feedback.
Homeostasis: the regulation of the physical, chemical and thermal status of all cells within an
organisms - maintaining the internal environment in order to survive.
Stimulus —> receptor —> input —> output —> response
Physiological control: something that we directly control; modifying physiological functions
to support life. Eg heart rate and breathing. Controlled structures are called ‘effectors’
Physiological regulation: ‘controlling’ a physiological function is designed to ‘regulate’ a
variable. Eg. We control heart rate and we control breathing in order to regulate the blood
pressure and oxygen in a manner that support life.
-If particular physiological variables move outside thresholds, this results in heat. Blood
pressure and oxygen are to controlled - they are regulated within upper and lower thresholds
to support life.
-Lungs, vessel diameter and heart are controlled in order to regulate blood pressure and blood
oxygen levels.
-Regulated variables have greater stability than controlled variables. Ie. smaller differences in
upper and lower thresholds.
Eg. Heart rate can change from 55 - 220 bpm during intense exercise, but blood pressure only
changes120 - 220mmHg.
-Controlling a physiological function is designed to regulate a variable in a manner that
supports life.
Basic elements of a control system:
1. Control involves interpreting and responding to information —> afferent signals from
receptors.
2. System error identification —> required for response
3. Means through which to react to error —> efferent signals to effector organs.
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Document Summary
To introduce students to control theory as it relates to homeostasis. Demonstrate an understanding of the different between physiological control and regulation. Describe the meaning and physiological significance of different forms of control, and feedback. Homeostasis: the regulation of the physical, chemical and thermal status of all cells within an organisms - maintaining the internal environment in order to survive. Stimulus > receptor > input > output > response. Controlled structures are called effectors" something that we directly control; modifying physiological functions. Physiological regulation: controlling" a physiological function is designed to regulate" a variable. We control heart rate and we control breathing in order to regulate the blood pressure and oxygen in a manner that support life. If particular physiological variables move outside thresholds, this results in heat. Blood pressure and oxygen are to controlled - they are regulated within upper and lower thresholds to support life.
