Water Handling - Kidneys Flashcards Preview

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Flashcards in Water Handling - Kidneys Deck (17):

What is the osmolarity of all the parts of the tubule?

Proximal: 300mOsm
Descending: 300-1400mOsm
Ascending: 800-200mOsm
DCD: 200-100mOsm
Collecting: 100-1400mOsm


Why is osmosis important in water handling?

Water moves by osmosis out of the tubule to match the osmolarity of the medulla


What happens to water reabsorption of ADH is present?

Present: water will be reabsorbed out of the collecting duct and match the osmolarity of the surrounding medulla as it increases in [] on the way down. Urine will be low volume and high concentration of solutes

Not present: Water will not be reabsorbed because there will be no aquaporin channels to allow the water out of the collecting duct. Urine will be high volume but low concentration because osmolarity of the surrounding medulla will not have as strong an effect


How are water and salt regulated different than any other process in the body?

They both can be regulated independently to maintain homeostasis


What is the average expulsion of urine a day?

-low as 0.4L
-high as 25L


Where does most of our water come form?

What we drink and what we eat


Where do we lose most of our water from?

Skin & Lungs


How do kidneys and blood volume relate?

Kidneys can control the blood volume. If total body water decreases the ECF (blood plasma) volume decreases, blood pressure decreases.

If total body water increases, blood volume increases
-help by not constricting fluids in the tubules


How do kidneys know when ADH is required?

Kidneys rely on pressure differences to determine whether or not ADH is required


Where is ADH
-Hormone properties

Made: In the hypothalamus
Stored: In the posterior pituitary
Properties: Peptide hormone, receptors on the outside of the cells, released directly to the blood
Stimulus: high plasma osmolarity and low ECF volume (resulting in low BP)
Action: Increases the number of AQII channels on the luminal membrane of the collecting duct


What are the sensors for ADH?

Osmoreceptors: Located in the hypothalamus, Increased plasma osmolarity causes receptors to shrink in volume triggering ADH release
-when plasma is higher than normal, causes receptors to decrease in volume causing ADH release because the solution around the cell is a higher osmolarity

Baroreceptors: Located in the aortic arch and carotid sinus, when ECF decreases ADH is released because there are fewer action potentials sent to the hypothalamus via these receptors


How does ADH cause more water reabsorption in the collecting duct?

When ADH is present it is released from the posterior pituitary, binds extracellular receptors, increases the number of AQII channels on the luminal membrane in the collecting duct
-AQII are in vesicles in the cytoplasm of tubule cells


What happens when plasma osmolarity is higher than normal?

ADH is released


What is the flow chart outlining the stops that cause an increase in water reabsorption in the collecting duct starting with an increase in plasma osmolarity

Increase in plasma osmolarity, osmoreceptors shrivel, ADH is released, ADH binds receptors in the collecting duct, More AQII channels move to luminal membrane, More water is reabsorbed


What is the flow chart outlining the steps that cause an increases in water reabsorption in the collecting duct beginning with a decrease in total body water

Decrease in total body water, decrease in BP and ECF, senses by baroreceptors in arctic arch and carotid, decrease in AP's sent to the hypothalamus from baroreceptors triggers the release of ADH, stimulates kidneys to take up more water via more AQII channels


What is diuresis?

Increased production of urine


What are the 2 main causes of diuresis?

Diabetes insipidus: Reduced ADH function (genetic or receptors on collecting duct can't recognize the ADH), increasing urine production

Alcohol: Inhibits ADH release from posterior pituitary and enhances urine production