Homeostasis & Control Systems Flashcards
What does homeostasis mean?
Maintenance of a constant internal environment
Underpins all life processes
What is a controlled variable?
Some aspect of the internal environment e.g. blood pressure, plasma [glucose]
What is a set point?
Value at which the variable should be maintained
What is the primary mechanism of negative feedback control?
Aims to maintain a controlled variable at its set point
Controlled variable = aspects of internal environment
Set point (ideal value) = value at which variable should be maintained
What are the main components of a negative feedback loop?
- Sensor = detects the change in variable and switches mechanism off after change
- Integrating centre = processes information & causes change
- Effector = brings change
What role do baroreceptors play in the regulation of blood pressure?
Detect changes in blood pressure and send signals to the medulla oblongata
What is the function of the medulla oblongata in blood pressure regulation?
Acts as the integrating center
What is the role of the autonomic nervous system in blood pressure regulation?
- Increases cardiac output
- Causes vasoconstriction
What is an example of a variable that shows diurnal changes in set point?
Body temperature
True or False: Positive feedback mechanisms reinforce the initial stimulus.
True
Give two examples of positive feedback mechanisms.
- Action potential in nerves
- Blood clotting
What are the two control systems involved in homeostasis?
- Nervous system
- Endocrine system
What are the effects of the nervous system?
Rapid, short term effects (seconds)
E.g. baroreflex
What are the effects of the endocrine system?
Long term effects (minutes to days)
E.g. growth, metabolism, blood volume regulation
What are the two divisions of the autonomic nervous system?
- Sympathetic
- Parasympathetic
What is the primary function of the sympathetic nervous system?
More active in stressful situations (‘flight or fight’ response)
What is the primary function of the parasympathetic nervous system?
More active in vegetative situations
What neurotransmitter is released by the adrenal medulla?
Adrenaline (epinephrine)
What type of response does the sympathetic division typically elicit?
‘Flight or fight’ response
Fill in the blank: The preganglionic fibers of the sympathetic nervous system are _______.
Short
Fill in the blank: The preganglionic fibers of the parasympathetic nervous system are _______.
Long
What is an example of hormonal control in homeostasis?
- Thyroid hormones - metabolism
- Growth hormone - growth
What is the feedback mechanism for cortisol regulation?
Negative feedback involving CRH and ACTH
What is the feedback mechanism for oxytocin during suckling?
Positive feedback
