Bio307 - Ch. 20 - Fluid Balance

diuresis/diuretic

water-excretion

aquaporin

protein that selectively allows water to pass into and out of a cell, forming pores in the membrane

vasopressin (ADH)

pituitary hormone that promotes the retention of water by the kidneys and increases blood pressure (aka ADH)

stimulated release when:
- blood pressure is low
- when plasma osmolarity is high

osmoreceptors

group of cells that are sensitive to plasma osmolality, regulating water balance

aldosterone

hormone responsible stimulating the retention of Na+ and secretion of K+ in response to low blood pressure (or hyperkalemia - excessive K+ content)

acidosis

higher than normal levels of acid (excessively low pH)

alkalosis

lower than normal levels of acid (excessively high pH)

renin-angiotensin system (RAS)

critical regulator of blood volume (aka blood pressure) and systemic vascular resistance: when blood pressure is detected to be low by baroreceptors, the RAS pathway is activated which stimulates release of aldosterone

associated with blood pressure regulation via modulating blood volume, sodium reabsorption, potassium secretion, water reabsorption, vascular tone

stimulates the release of aldosterone

granular cells release renin in the kidney

Major Physiological Responses to change in blood volume/BP

Cardiovascular: vasoconstriction/vasodilation
Behavioral: thirst increases/decrease
Endocrine: ADH release control
Renal: conservation of salt and water
BP/Blood Pressure: increase/decrease

Recognize that water always moves to the area of higher total osmolarity

...

Identify the major routes by which water enters and exits the body

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Explain or identify how the osmolarity gradient is created in the loop of Henle

*diagram explanation*

Explain the mechanism by which existence of loop of Henle allows humans to concentrate urine

the ascending loop is impermeable to water, so urine becomes concentrated via the reabsorption of ions

Why degree to which urine can be concentrated to is equal to the osmolarity of the bottom of the loop of Henle

osmolarity wants to become equal (isosmotic)

Mechanism of Action of Vasopressin (when is it high/low)

aka ADH, water-retention hormone

more release when water levels are low in the body

less is released when blood pressure is higher in the body

Mechanism of Action of Aldosterone (when is it high/low)

the Na+ reabsorption hormone

released when blood pressure is low, or when K+ levels are high

inhibited when blood pressure is high, or K+ levels are low

The major signal mediating increased aldosterone release is the renin-angiotensin system (RAS)

ANGII is an inactive precursor made by the liver.

Release is high when blood pressure is low.

The target effect is to raise blood pressure in the body.

Acts at the adrenal cortex, arterioles, medulla oblongata, hypothalamus

Predict and explain how changes in plasma osmolarity, blood volume, blood pressure affects vasopressin release

Released when plasma osmolarity is high, or when blood pressure or volume (carotid, aortic, atrial receptors)

Know that: Aldosterone acts at the DCT to increase Na+ concentration

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Mechanism for how changes in respiratory rate changes and corrects blood pH

A higher respiratory rate causes more diffusion of gas (oxygen and carbon dioxide) which will take away carbon dioxide and introduce more oxygen, which would increase blood pH

When slowing respiratory rate, less CO2 would be exhaled which means that blood would maintain a more acidic pH (lower)

How kidney corrects low/high blood pH

kidney has control over the reabsorption of bicarbonate via urine into blood

less HCO3 reabsorption = lower pH (compensates to shift right, which introduces more H+ acid)
more HCO3 reabsorption = higher pH (compensation to shift left, away from acid, making it more basic)

Respiratory vs Metabolic acidosis

Acidosis: pH is too low

Resp: Hypoventilation (too much CO2)

Metabolic: ex: lactic acidosis, ketoacidosis, fat/amino acid breakdown releases acid
- can result when bicarbonate is lost by diarrhea

Respiratory vs Metabolic Alkalosis

Alkalosis: pH is too high

Resp: Hyperventilation (deficient in CO2, which would mean equation shifts left)


Metabolic: excessive vomiting of acidic stomach content, and excessive ingestion of bicarbonate-containing antacids (decrease H+)