Fluid & Electrolyte

Diffusion

Passive transport, movement of particles from high concentration to low. How water moves through the lipid bilayer

Hydrostatic pressure

Mechanical force of water pushing against cellular membranes

Osmosis

The movement of water from higher to lower concentration

Osmolality

Controls the distribution of movement of water between body compartment.

Technically the number of milliosmoles per kg of water,

Oncotic pressure

The overall osmotic effect of colloids (such as plasma proteins)

Aquaporins

Water channel proteins that provide permeability to water

Capillary hydrostatic pressure

Facilitates the outward movement of water from the capillary to the interstitial space

Systems responsible for Na and H2O balance

Systems responsible for …

• Renal

• Endocrine

RAAS system

Multi-organ “system” that increased blood pressure

Osmoreceptors

Specialized receptors that detect changes in osmolality

Most are located in the hypothalamus

ANP

Atrial natriuretic peptide, made by the atria, released from the heart when the transmural atrial pressure increases (increased volume), when the tension in the LV wall increases, or when the MAP increases

BNP

B-type natriuretic peptide, made by the ventricles, released from the heart when the transmural atrial pressure increases (increased volume), when the tension in the LV wall increases, or when the MAP increases

Baroreceptors

Receptors sensitive to changes in blood pressure/volume that are located in the aorta, pulmonary arteries, and carotid sinus

Stimulate thirst and the release of ADH

Regulates K+

Aldosterone conserves Na but regulates the concentration of which electrolyte?

Lungs and kidneys

What buffers acid base imbalance?

4 types of acid base imbalance

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Compensation (acid base)

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Anion gap

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Mechanism of edema

Mechanism of

Caused by venous or lymphatic obstruction, increased vascular volume, plasma protein losses, or increased capilarry membrane permeability

SIADH

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DI

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Electrolyte imbalances with excessive vomiting

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Electrolyte imbalances with excessive diarrhea

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EKG changes w/ electrolytes

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s&s of electrolyte imbalances

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Sodium

What solute is responsible for the osmotic balance of the ECF?

Potassium

What solute helps maintain the ICF osmotic balance?

Capillary oncotic pressure

Osmoticaly attracts water from the interstitial space back into the capillary

Interstitial hydrostatic pressure

Facilitates the inward movement of water from the interstitial space into the capillary

Interstitial oncotic pressure

Osmotically attracts water from the capillary wall

Forces favoring filtration

= Capillary hydrostatic pressure + intersitial oncotic pressure

Forces opposing filtration

= Capillary oncotic pressure + interstitial hydrostatic pressure

total body water

The sum of all fluids in the body, higher in infants d/t less body fat, lower in old age d/t loss of muscle/increase of body fat

net filtration

movement of water across the capillary wall (= forces favoring filtration - forces opposing filtration)

increases hydrostatic pressure

What does increased vascular volume do?

decreases plasma oncotic pressure

What does increased capillary membane permeability cause?

effusion

fluid accumulation within a body cavity/space, sometimes called a third space

aldosterone

hormone responsible for regulating sodium balance by increasing reabsorption in the distal tubules of the kidneys

renin

enzyme secreted by juxtaglomerular cells of the kidneys when…

• blood pressure/volume is reduced

• when Na+ levels in the renal tubules are depressed

• there is increased firing of the renal sympathetic nerves

angiotensin i

inactive polypeptide, converted into angiotensin ii by ACE

angiotensin ii

a potent vasoconstrictor, converted from angiotensin i by ACE

ANH

Involved with decreasing renal tubular resorption and promoting urinary excretion of sodium

Decreased renal perfusion

What activates the RAAS system?

The liver

Which organ(s) releases angiotensinogen?

kidneys

Which organ(s) releases renin?

Lungs

Which organ(s) release angiotensin-converting enzyme (ACE)?

Adrenal cortex

What releases aldosterone?

Aldosterone

What hormone causes:

• Potassium excretion

• Sodium and water retention

• Increased ECF

vasoconstriction

What is the function of Angiotensin II?

Acid base balance

Refers to the concentration of hydrogen ions in body fluids, which needs to be in a very narrow range to maintain homeostasis