Topic 1: Intro to Physiology Flashcards
what is physiology?
-study of how the body functions
-study of physical and chemical processes in cells, tissues, organs and organ systems
-processes allow these things to work individually and together
what is homeostasis?
-ability to maintain relatively stable conditions in the bodies internal environment
-despite changes in the external environment
what is the purpose of homeostasis?
-cells can only survive within a narrow range of conditions (physiological limits)
-body conditions must be maintained for cell life
what are examples of body conditions controlled by homeostasis?
-pH
-temp
-blood gases (CO2, O2)
-blood pressure
-intracellular and extracellular fluid volumes
what maintains homeostasis?
-organ systems functioning together
what results in the failure to maintain homeostasis?
-disease
what are our regulatory systems/control centers?
-nervous system
-endocrine system
-control all the other systems
how do the regulatory systems act?
-to maintain homeostasis
-to permit departures from homeostasis in a CONTROLLED manner
what are examples of situations where homeostasis would need to be departed?
-pregnancy
-growth
-sudden fright
what does it mean when we say that homeostasis may be departed in a controlled manner?
-although homeostasis is departed, regulation is still occuring
-regulation is not “on pause”
how is homeostasis regulated?
-changes in the internal environment are detected or anticipated
-nervous system and/or endocrine system responds by altering the systems responsible for the deviating condition
what are the 2 types of nervous/endocrine responses for homeostasis regulation?
-anticipatory responses
-feedback mechanisms
what are anticipatory responses?
-responses that occur in anticipation of a future event or stimulus
-may be learned or behavioural
what is an example of an “unconscious” anticipatory response?
-increased respiratory rate at the start of exercise
-changes the gases in the blood
-increased need for oxygen
what acts during the anticipatory response for increasing the respiratory rate before exercise?
-proprioceptors (NS stretch receptors)
-signal movement before a significant change in internal conditions (gases in blood)
what is an example of an “conscious” anticipatory response?
-putting on a coat
-example of a learned/behavioural response
what are feedback mechanisms?
-mechanisms that respond to change in a system
-have 3 basic components
what are the 3 basic components of a feedback mechanism?
-receptors
-control centers
-effectors
what is the role of a receptor in a feedback mechanism?
-monitor variables/conditions
-detect stimuli
what is the role of a control center in a feedback mechanism?
-integrates info and maintains set points by signalling to effectors
what is a set point?
-range of values of a variable that do not bring a response
-normal range (physiological limits)
-ex: body temp=variable
what is the role of effectors in a feedback mechanism?
-create a response that will alter the variable/condition
-effectors are muscles and glands
what is the general pathway of a feedback mechanism?
-information from receptors (input) is sent to the control center
-control center signals the effector (output) to bring a response
what directions do changes go within feedback mechanisms?
-original change can go in either direction (up or down)
-response created by the effectors can bring the new change in either direction (depending on the type of mechanism)
what are the 2 types of feedback mechanisms?
-negative feedback
-positive feedback
what is negative feedback?
-most common homeostatic mechanism
-the result of the output is bringing the variable back to the set point (opposite/negative direction of the original direction of change/input)
what is an example of a negative feedback loop for an increase in body temp?
-high temp. is detected by thermostat cells in the hypothalamus (receptor + input)
-the brain (control center) creates a response (output)
-smooth muscle of blood vessels dilate/relax (vasodilation + response) and sweating of sweat glands to decrease body temp (opposite direction of input/stimulus)
how does the vasodilation of blood vessels bring down body temp?
-warm core blood is brought to the cooler skin surface (causing sweating)
-sweat will evaporate (increased heat loss)
how is body temp increased?
-shivering
what can sometimes occur to set points? what is an example of when this occurs?
-set points can change
-when you have a fever
what is positive feedback?
-less common mechanism
-NOT homeostatic
-output of the feedback process will intensify the input
-variable moves farther away from the set point
what is an example of positive feedback?
-childbirth (labour)
-uterine contractions > nervous system > posterior pituitary gland which release oxytocin (hormone)
-oxytocin increases the positive feedback which increases contractions
-continues until the endpoint (baby is born)
