Homeostasis and physiological variables Flashcards
Physiology definition
-Study of how organisms function
-How function is controlled and maintained in order to stay healthy
Physiological vs pathophysiological
Physiological = normal function/health
Pathophysiological = abnormal function/health
What is a physiological variable?
A measure of a body condition
Homeostasis definition
Dynamic maintenance of physiological variables within a predictable range
Set point definition
The normal value for a physiological variable (e.g. 37 degrees body temp)
What is meant by hierarchy of importance
-Certain physiological variables are more important than others
E.g. Osmolality (salt/water balance) is more important immediate survival than blood pressure. BP can be elevated too high to maintain osmolality
Negative feedback definition
-A change is sensed and a response is initiated to reverse that change
-The effect is to maintain physiological variables within a predicted range
Feed forward definition
-Anticipation of a change brings about the response to that change before the change can be detected by negative feedback sensors
Positive feedback definition
-A change in a variable triggers a response that causes further change in that variable
-The effect is therefore amplification of the change rather than normalisation
Key features of all negative feedback loops
What type are negative feeback loops typically?
-Neuronal
-Hormonal
-Sometimes paracrine
ANS in physiological control
-ANS controls involuntary processes
-Manages things like CO, GI tract mobility, bladder control, exocrine/endocrine secretions
-Sympathetic and parasympathetic have opposing actions and ‘fine tune’ the variables
What type of feedback is feed forward control usually?
-Often neuronal
E.g. The anticipation of a meal stimulates saliva and gastric juice production
What are the human endocrine organs?
Classes of hormones
-Tyrosine derivatives
-Peptides
-Polypeptides
-Glycopeptides
-Steroids
What is the precursor for steroid hormones and what hormones does it produce?
-Cholesterol
-Mainly found in liver
-Used to produce estradiol and testosterone in ovaries and testes
-Used to produce cortisol and aldosterone in adrenal cortex
Hormones, receptors and mechanisms
Paracrine homeostatic control
Examples of paracrine homeostatic control
Positive feeback example
