WEEK 10 - Topic 1 - Homeostasis (Intro) Flashcards
What is a feedback?
A response
What is a stressor?
The stimulus
What is the difference between a negative feedback mechanism and a positive feedback mechanism?
Negative feedback: A homeostatic control mechanism in which the effector response negates the effects of the original stimulus.
Positive feedback: A process in which the effector response enhances the effects of the original stimulus.
What are the components of a feedback mechanism?
- Stimulus (change in variable)
- Receptor/Sensor (detects the stimulus and sends info to the control centre)
- (Info sent along the afferent pathway to control centre)
- Control centre (determines set point, analyses the information and determines response)
- (Info sent along the efferent pathway to effector)
- Effector (causes the response; negates or enhances effects of stimulus)
Examples of some important homeostatic variables
Body temp
Blood pressure
Blood Ca2+ levels
What are changes in a variable termed as?
Stimulus
What is a stimulus
Change in variable
Define homeostasis
Homeostasis is a state of stable internal environment of the body or a tendency towards such a state
Is a variable in a system controlled by negative feedback maintained perfectly?
No, the variable oscillates between an acceptable range - the normal range of function
Who coined the word homeostasis?
Walter Cannon
Can the set point of function be reset? Give example.
Yes. For eg, the set point for GH increases at night, and more GH is secreted.
What is the set point of function?
A set point is the baseline level at which functions can operate efficiently and the variables oscillate around this point (usually the midpoint of a narrow range of values).
It is also the value towards which the system is returned if a disturbance is detected.
For homeostasis what conditions are observed?
The variables in the blood are measured as the composition of blood reflects the status of the ECF, which in turn affects cell functions
What is the range of values at which functions operate efficiently called?
Normal range of function
What is the internal milieu of the body?
The ECF
Which systems are involved in directing homeostatic responses?
Nervous and endocrine system
Why are variables in the blood measured to maintain homeostasis?
The composition of the blood plasma reflects the status of the ECF, which in turn affects cell functions
What does humoral mean?
Pertaining to the fluids of the body
(REVISION) ECF includes:
- Interstitial fluid
- Blood plasma
- Transcellular fluid
Who is the father of homeostasis?
Claude Bernard
What is an error signal?
Deviation from original value of a variable due to the maintained environmental perturbation
What is an error?
Deviation from a set point
What is a gain?
The gain describes how well a system copes with a stressor; how well the system can correct deviations from the original set point.
Correction/error
Hot day, 45C
Body temperature may only rise to 38C from 37.5C.
What is the correction, error and gain?
Correction: -7C
Error: 0.5C
Gain: 14
