(Slide 8-17)

What occurs if fluid intake does not equal fluid output?

Fluid Imbalance

Fluid imbalance is organized into what five categories?

• Volume depletion

• Volume excess

• Dehydration

• Hypotonic Hydration

• Fluid Sequestration

What best described what happens during:

• Volume depletion

• Volume excess

Osmolarity is constant

• Isotonic Fluid is lost or gained

  • Isotonic fluid = Water + Solutes

What best described what happens during:

• Dehydration

• Hypotonic Hydration

Osmolarity changes

• Water is lost or gained

  • Osmolarity increases or decreases

What is volume depletion?

Isotonic loss of water and solute with decreased ECF volume and unchanged osmolarity.

• → ECF volume ↓ → Osmolarity stays the same → No water shift → Cells unchanged

What is volume excess?

Isotonic gain of water and solute with increased ECF volume and unchanged osmolarity.

• → ECF volume ↑ → Osmolarity stays the same → No water shift → Cells unchanged

What defines dehydration (hypertonic imbalance)?

Water loss exceeds solute loss, increasing ECF osmolarity and causing cells to shrink.

• → ECF osmolarity ↑ → Water leaves cells → Cells shrink

What defines hypotonic hydration?

Water gain exceeds solute gain, decreasing ECF osmolarity and causing cells to swell.

• drinking larges amounts of water in a short amount of time

• → ECF osmolarity ↓ → Water enters cells → Cells swell

What is fluid sequestration?

Abnormal accumulation of fluid in a specific compartment such as interstitial space (edema)

• Body fluid distributed abnormally

What is Fluid Sequestration caused by?

• Ex: Edema

• Abnormal changes in the cardiovascular system

• Abnormal blood composition

• Changes to lymph vessels

What is hyponatremia?

Low sodium concentration in the ECF

• specifically blood/blood plasma

Hypotonic hydration is also known as?

Water intoxication

• when cells swell

Water intoxication/Hypotonic hydration is caused when a person?

Drinking water faster than the kidneys can excrete it or replacing losses with plain water (no electrolytes)

• Can lead to convulsions ,coma, or death

• Hypoatremia

Why is water intoxication/Hypotonic hydration dangerous?

Cell swelling in the brain increases intracranial pressure and can cause seizures or coma.

• Convulsions, coma, and possible death

What direction does water move when ECF becomes hypotonic?

Into cells

What direction does water move when ECF becomes hypertonic?

Out of cells

What is the key difference between isotonic and osmotic fluid imbalances?

Isotonic imbalances change volume only; osmotic imbalances change both osmolarity and cell size.

Excessive blood loss, sweating, vomiting, or diarrhea coupled with intake of plain water leads to?

Decreased Na+ concentration of interstitial fluid and plasma (hyponatremia)

Decreased Nat concentration of interstitial fluid and plasma (hyponatremia) leads to?

Decreased osmolarity of interstitial fluid and plasma

Decreased osmolarity of interstitial fluid and plasma leads to?

Osmosis of water from interstitial fluid into intracellular fluid

Osmosis of water from interstitial fluid into intracellular fluid causes?

Water intoxication (cells swell)

What Abnormal changes in the cardiovascular system causes Fluid Sequestration?

Valves are not functioning properly

What Abnormal changes in the blood composition causes Fluid Sequestration?

Not enough plasma protein

• decreases blood colloid osmotic pressure

  • less fluid in capillaries

What is an example of Fluid Sequestration?

Edema

What are the bodies means of regulating fluid balance?

• Monitor blood volume

• Blood pressure

• Blood plasma osmolarity

How does fluid intake affect blood volume, pressure, and osmolarity?

• Blood volume increases

• Blood Pressure increases

• Blood Osmolarity decreases

  • if water gain exceeds solute gain

How does fluid output affect blood volume, pressure, and osmolarity?

• Blood volume decreases

• Blood Pressure decreases

• Blood Osmolarity increases

  • If water is lost more than solute

Blood/Plasma Osmolarity is?

How concentrated the blood is with solutes (mainly sodium)

What four hormones are involved with the hormonal Regulation of Fluid & Solute Output?

• ADH

• Aldosterone

• Angiotensin ll

• ANP

Which hormone is being described?

• Released when osmolarity increases or blood volume decreases

• Inserts aquaporins → water reabsorption increases

• Urine volume decreases

• Blood volume increases

• Blood osmolarity decreases

Main goal is water reabsorption and cause vasoconstriction

ADH (Antidiuretic Hormone)

Which hormone is being described?

• Released when:

  • K⁺ is high

  • Na⁺ is low

  • Angiotensin II is high

• Increases Na⁺ reabsorption

• Water follows sodium

• Blood volume increases

• Increases K⁺ secretion

Aldosterone

Which hormone is being described?

• Activated when blood pressure is low

• Causes:

  • Vasoconstriction

  • Thirst

  • ADH release

  • Aldosterone release

Angiotensin II

Which hormone is being described?

• Released when atria stretch (high blood volume)

• Causes:

  • Na⁺ excretion increases

  • Water excretion increases

  • Blood volume decreases

  • Blood pressure decreases

• Opposes RAAS

• Promotes natriuresis; decreases blood volume/BP.

ANP (Atrial Natriuretic Peptide)

Main factor that determines body fluid volume?

Extent of urinary salt loss (how much salt you lose in urine)

• Lose a lot of Na⁺ in urine → lose water → blood volume drops

• Keep Na⁺ (via aldosterone) → keep water → blood volume rises

When we talk about how much sodium you keep or lose it is?

body fluid volume

Main factor that determines body fluid osmolarity?

Extent of urinary water loss (how much water you lose in urine)

• Lose water → osmolarity increases → blood becomes concentrated

• Keep water → osmolarity decreases → blood becomes diluted

When we talk about how much water you keep or lose it is?

Osmolarity

Water follows?

Salt

ADH is produced by the?

Hypothalamus

ADH is released and stored by the?

Posterior Pituitary Gland

What is the purpose of ADH?

• Constricts Arterioles

  • increases BP in surface arteries

• Increases Reabsorption of H2O in kidneys

  • increases BV

What is the excessive loss of sodium in Urine?

Natriuresis

What is not a major function of ADH?

It affects some social behaviors in mammals

The binding of ADH to receptors on the epithelial cells of the collecting tubule (principal cells) results in?

Aquaporins being inserted into the plasma membrane

• move water channel proteins, called aquaporins, from the interior of the cells to the apical surface, where these proteins are inserted into the cell membrane

What are water channel proteins?

Aquaporins

Aquaporins being inserted into the plasma/cell membrane causes?

An increase in the water permeability of these cells (principal cells)

• a large increase in water passage from the urine through the walls of the collecting tubules

• leading to more reabsorption of water into the bloodstream.

An increase in the permeability of the principal cells of the collecting tubule leads to?

• Urine becomes concentrated (less water more solutes)

• Blood Volume increases

• Blood Osmolarity decreases

What is the stimuli/trigger of aldosterone?

• High K⁺ levels

• Low Na⁺ levels

• Release of Angiotensin II

What are the actions of aldosterone secretion?

• These ALWAYS happen at the same time

• Kidneys reabsorb Na⁺

  • Water follows → blood volume ↑

• Kidneys secrete K⁺

Aldosterone is released by the?

Adrenal Gland

Aldosterone facilitates?

The reabsorption of Na+ and thus the reabsorption of water.

During aldosterone secretion, what is the end result?

Restores Na⁺/K⁺ balance

What releases renin?

Kidneys

What is the stimuli/trigger that causes the kidneys to release renin?

Low blood pressure

What pre-enzyme does the liver release into the blood?

Angiotensinogen

Renin converts angiotensinogen into?

Angiotensin l

• inactivated

ACE (Angiotensin-converting enzyme) converts angiotensin I into?

Angiotensin ll

• activated

ACE (Angiotensin-converting enzyme) is released by the?

Lungs

Angiotensin II stimulates?

• Aldosterone secretion by adrenal cortex

  • Na⁺ and water reabsorption increase

• ADH (Vasopressin) secretion

  • Water reabsorption increases

• Thirst

• Vasoconstriction of Blood vessels

End goal of angiotensin ll?

• Increase Blood volume

  • by water reabsorption

• Increase Blood pressure

  • by vasoconstriction blood vessels

Insufficient H2O in the body means?

• Decreased blood volume

• Increased blood osmolarity

Decreased blood volume caused by insufficient H2O in the body causes?

Decrease in blood pressure

• which then activates the Sympathetic Nervous system using Baroreceptors

  • which then activates the RAA pathway

Increased blood osmolarity caused by insufficient H2O in the body causes?

• Dry mouth

• Osmoreceptors in the hypothalamus detect increase in osmolarity

What three factors stimulate the thirst center hypothalamus?

• Increase in Angiotensin ll

• Dry mouth

• Osmoreceptors in the hypothalamus detect increase in osmolarity

When the thirst center in the hypothalamus is secreted, what happens?

• Increases our thirst

• Which then causes us to drink water

• Which then decreases the blood osmolarity and increases blood volume

The thirst response begins when?

Osmoreceptors detect a decrease in water levels in the blood.

What hormone is released when the atria stretch due to increased blood volume after a salty meal?

ANP (Atrial Natriuretic Peptide)

• increases GFR

• increases Na⁺ excretion (natriuresis)

• increases water loss

• decreases blood volume.

Why does angiotensin II decrease after eating a very salty meal?

High blood volume suppresses renin release → less angiotensin II → less aldosterone → reduced Na⁺ and water reabsorption.

How does aldosterone respond to a salty meal, and why?

Aldosterone decreases because angiotensin II is low

• This reduces Na⁺ reabsorption so the kidneys excrete more Na⁺ and water to lower blood volume.

What causes a reduced reabsorption of NaCl by the kidneys?

• Increased release of ANP

• Decreased formation of Angiotensin ll

  • Increases glomerular filtration rate

  • decreases release of aldosterone

Reduced reabsorption of NaCl by the kidneys causes?

• Increased loss of Na and Cl in urine (natriuresis)

• Increased loss of water in urine by Osmosis

• Decreased blood volume