Homeostasis and feedback mechanisms Flashcards
(23 cards)
Homeostasis
Dynamic maintenance of stable conditions for cells so that cell is able to survive.
Not an exact point but a range of normal for various parameters.
Internal environment is defined as the extracellular fluid.
What are regulated directly by homeostasis
plasma and ECF
-organ systems function to homeostatically maintain some extracellular parameter.
what is regulated indirectly by homeostasis
ICF
What kind of things do cells need
ecf (high in sodium), certain ph, temperature, glucose, osmolarity, nutrient balance, waste disposal
3 body compartments
extracellular compartment (outside the cells and plasma 3L), intracellular compartment (28 L) and interstitial fluid (11 L)
ECF divided into…
plasma (3L) within the vascular system interstital fluid (14L) directly bathing cells
ECF is high in
NA+, Cl-, HCO3-, 02, glucose and fatty acids
ICF size and contains…
28L
k+, Mg+ and PO4
where are most of the proteins found
ICF
what parameters are are regulated by homeostasis
appropriate concentration of gasses, ions, nutrients, ions and H20, appropriate temperature level and appropriate plasma volume
Two basic mechanisms for homeostatic regulation
intrinsic regulation and extrinsic regulation
Example of intrinsic regulation
occurs within a cell or tissue without the help of a hormone or nerve.
ex. scientist should be able to remove a tissue and/or organ and provided with the same physiological conditions and still see the regulatory response
ex: local control of blood flow, frank starling law of the heart
forms of intrinsic regulation
active hyperemia (increase in blood flow in response to the products of metabolism) autoregulation (keeps blood flow constant despite changes in mean arterial blood pressure)
extrinsic regulation
occurs from outside of the tissue by an endocrine or nervous system.
ex. activation of the PNS or SNS
neuro extrinsic mechanisms
tends to be rapid, fast on and off,
endocrine mechanisms
slower and have longer effects
feedback loop
way to control some physiologic parameter. A change in that parameter exerts a stimulus on the system. The system sense the stimulus then communicates the intensity with the control center or integrating center. The control center evaluates from normal or from the setpoint. If an action is needed the control center communicates this to an effector (muscle or gland). Effector produces a response to the stimulus.
Negative feedback loop
The response from the effector opposes the stimulus and returns the system to setpoint.
ex: BP, temp, H20, oxyhemoglobin curve baroreceptors, body fluids, furnace
Positive feedback system
response from the effector reinforces the stimulus and adds an additional increase to the stimulus.
ex: labor, orgasm, action potential, lactation, blood clotting, hormonal chages leading to ovulation
- good for building to a completion event
Factors that affect normal ranges or set point
age, gender, genetics, environmental factors
ability to maintain homeostasis is dependent on
Integrity of the physiologic system (age, gender, genetics) the nature of the stress and situational factors (time and place) if homeostatic mechanisms cannot be maintained disease results
examples of stressors that can change physiologic parameters
pathogens and parasites, genetic disease, cancer, autoimmune disease, degenerative changes, trauma, toxins, environmental factors, nutritional deficiencies or excesses
Parts of the feedback loop
Receptor (monitors some parameter)
Afferent (receptor communicates to the integrating center and a neuro mechanisms via this pathway)
Control Center (determines what the parameter should be and what type of action should be taken to maintain the parameter)
Efferent (motor pathway, acts on an effector)
Effector (either a gland or muscle brings about some response that effects the parameter)
