D236 EXAM WGU: D236 SECTION 1 -
HOMEOSTASIS AND CELLULAR
RESPONSE, 2025/2026 WITH
CORRECT/ACCURATE ANSWERS
oliguria
urine output of less than 400 mL/day or less than 20 to 30
mL/hour.
Diruesis
loss of water from the body in the form of urine
furosemide/hydrochlorothiazide
patho
suffering or disease
pathophysiology
refers to the study of abnormal changes in body functions that
are the causes, consequences, or concomitants of disease
processes.
Starling's Law of Capillary Forces
Starling’s Law of Capillary Forces explains the movement of fluid
that occurs at every capillary bed in the body.
There are two major opposing forces at every capillary
membrane:
1. Hydrostatic pressure
,2. Osmotic pressure (includes oncotic pressure)
Within every capillary, electrolytes and proteins within the blood
exert osmotic pressure.
The fluid within the capillary exerts hydrostatic pressure.
These pressure forces oppose each other and attempt to balance
each other out at every capillary membrane, thereby creating a
state of homeostasis
Principles of Starling’s Law can be applied in the clinical
setting.
For example, swelling can be reduced using an Epsom salt bath,
which is a hypertonic magnesium salt solution. Placing a swollen
finger in an Epsom salt bath will draw ICF from the finger into the
Epsom salt solution, thereby reducing the fingers swelling.
Fluid homeostasis
Various physiologic mechanisms work together in order to
maintain fluid homeostasis.
In terms of fluid volume, both fluid intake and output must be
regulated to prevent fluid volume overload, also known as edema,
and fluid volume deficit, also known as dehydration.
However, in addition to fluid volume status, the relative
composition of body fluids, including electrolyte and acid or base
concentrations, needs to be consistent.
The kidney, rennin-angiotensin-aldosterone system (RAAS),
osmoreceptors, thirst sensation, antidiuretic hormone (ADH), and
natriuretic peptides work together to maintain fluid homeostasis
in the body
Osmoreceptors, ADH, and thirst.
,Changes in plasma osmolarity are responsible for both the
sensation of thirst and the release of ADH, also called arginine
vasopressin.
High plasma osmolarity stimulates osmoreceptors in the
hypothalamus.
This stimulates the hypothalamic thirst center of the brain, as well
as promoting the release of ADH from the posterior pituitary.
Thirst is a conscious desire to drink fluids.
It is triggered by a response in the thirst center, which is located
in the anterior hypothalamus.
The osmoreceptors respond to changes in both blood osmolarity
and blood fluid volume.
When there is an increase in blood osmolarity, ICF shifts into ECF
and the cells shrink, stimulating the thirst center.
This center transmits signals to the cerebral cortex, promoting the
sensation of thirst.
Thirst causes a conscious desire to drink fluids, which brings
water into the body's bloodstream to reduce osmolarity.
Massive loss of blood and fluid volume, as is seen in severe
trauma, will trigger the sense of thirst as well.
In a healthy person, osmoreceptors, ADH, and thirst responses
work together.
ADH is produced by the hypothalamus.
, Once the ADH is synthesized, it travels by an axonal transport
mechanism to the posterior pituitary gland.
When the bloodstream lacks sufficient water, plasma osmolarity is
increased and the osmoreceptors shrink.
This stimulates the ADH neurons to depolarize, releasing ADH
from the posterior pituitary.
In addition to changes in osmolarity, other factors such as pain,
trauma, and medications stimulate the release of ADH.
After release into the bloodstream, ADH stimulates water
reabsorption from the nephron tubule fluid at the collecting duct
into the bloodstream.
This raises the blood's water content and decreases the water in
the tubule fluid, which eventually becomes concentrated urine.
When there is enough water in the bloodstream, plasma
osmolarity decreases, and ADH secretion is inhibited.
raas
renin-angiotensin-aldosterone system
Hypotension, hypovolemia, dehydration, and low cardiac output
cause low circulation throughout the body
Reduced circulation causes low renal perfusion, which stimulates
renin secretion by the kidney’s juxtaglomerular apparatus.
Renin initiates the RAAS, a compensatory mechanism used to
replenish blood volume and raise blood pressure
