BI 233 - Chapter XIV: Fluid, Electrolytes, Acid-base balance

65% of fluid in our body is ___

intracellular fluid (cytosol)

35% of fluids in our body is ____

extracellular fluid (ECT)

What are some extracellular fluids in our body?

blood plasma, lymph, CSF, perilymph, bile, etc

Osmosis is the continual movement from one compartment to another that depends on what?

the concentration of solutes in each compartment

Metabolic water is the by-product of what?

aerobic respiration and dehydration synthesis

Insensible water loss includes:

expired air, cutaneous transpiration, and sweat

Sensible water loss includes:

feces. urine, and sweat

True dehydration occurs when ____

blood volume declines due to loss of water and sodium concentration rises

Things that can attribute to true dehydration:

lack of drinking, profuse sweating, ADH hyposecretion, untreated diabetes mellitus, and overuse of diuretics

Hypovolemia is when ___

proportionate amounts of water and sodium are lost without replacement

Things that can attribute to hypovolemia:

hemorrhaging, severe burns, chronic vomiting, chronic diarrhea, and aldosterone hypersecretion

Dehydration can lead to what?

reduced blood volume pressure and osmolarity

Osmoreceptors (neurons) in circumventricular organs (in/connected to hypothalamus) detect ____

increased osmolarity

290 mOsms/L water flows out of these neurons by osmosis (via aquaporins). Causes the cells to shrink. The shrinkage cuases what?

stretch-inactivated cation channels and Na+ and K+ flow in to depolarize the cell. This voltage change opens voltage-gated Na+ channels, more Na+ flows in, depolarizing this neuron to threshold → Action potential

ADH from capillaries around DTC and collecting duct cause an increases in ____

water reabsorption by increasing the number of aquaporins in the epithelium of the renal tubules

Without proportionate intake of electrolytes, water dilutes the ECF, making it ___

hypotonic

Antidiuretic hormone (ADH) hypersecretion can lead to ____

hypotonic hydration

Total body water and osmolarity may be normal, but the volume of circulating blood may ___

drop

What is edema?

abnormal accumulation of fluid in the interstitial spaces

What is a hemorrhage?

blood pools and clots in the tissues is lost to circulation

What is pleural effusion?

fluid accumulating in the pleural cavity due to an infection in the lungs

A congestive heart failure or incompetent heart valves (which cause blood back-ups in the capillaries) can cause what?

edema

Increased blood volume can cause what?

edema

Increased blood capillary permeability can cause what?

edema

Decreased level of proteins in blood can cause what?

edema

Why is electrolyte balance important?

maintaining homeostasis, or relative constancy, of electrolytes in the body is critical for the body to function normally.

Sodium is the most significant solute in determining ___

total body water and the distribution of water among compartments. 99% is in ECF

Na+ bound to proteoglycans of cartilage retain ____

water so cartilage is well hydrated and able to function in cushioning

Na_ gradients provide potential energy commenced to ____

cotransport

Na+-K+ pump maintains ___

gradient & generates body heat

Sodium bicarbonate (NaHCO3) plays a major role in ___

buffering the pH of the ECF

Sustained abnormalities in [Na+] in the ECF occur when there are ____

severe problems with fluid balance

Hyponatremia:

[Na+] below 136 mEq/L (overhydration or inadequate intake of salt)

Hypernatremia:

[Na+] above 145 mEq/L (dehydration is the most common cause)

Aldosterone is a ____

salt retaining hormone

What is aldosterone secreted?

in the zona glomerulosa of the adrenal cortex

Aldosterone can also be secreted by _____

renin-angiotensin-aldosterone mechanism in cases of hypotension

Cells in the ascending limb of nephron loop, the distal convoluted tubule, and cortical part of collecting duct have ____

aldosterone receptors

Estrogen mimics the effect of aldosterone and causes people to retain water during _____

pregancy and part o the menstrual cycle

When blood pressure of blood volume decreases, juxtamedullary cells in kidneys release ___

renin

Renin converts angiotensinogen produced in the liver into ____

angiotensin I. This is done in the blood (plasma)

Angiotensin-Converting Enzyme (ACE) on endothelial cells in lungs (mostly) converts angiotensin I into ____

angiotensin II

Angiotensin II causes vasoconstriction and stimulates ____

aldosterone release from adrenal cortex (zona glomerulosa)

Aldosterone increases ____

Na+ and water reabsorption, further increasing blood volume and pressure

High [Na+] in blood stimulates ___

ADH release from posterior pituitary

The insertion of ADH adds more aquaporins to the ___

DCT and collecting duct which results in more water lost in urine

A drop if blood [Na+] will inhibit ___

ADH release

Atrial natriuretic peptides inhibit ____

sodium and water reabsorption, and secretion of renin, and ADH

Potassium (K+ - kalium) is the most abundant ___

ICF electrolyte

Na+-K+ pump maintains gradients, functions in ___

cotransport, and produces heat

Hyperkalemia can lead to ___

cardiac arrest (because more K+ ends up in the cell, which depolarizes too easily) if the onset of hyperkalemia is fast!

Hypokalemia can lead to ___

cells hyperpolarize and nerves, muscles are harder to excite. Leads to muscles weakness, loss of muscle tone, depressed reflexes, irregular electrical activity of the heart

Hypercalcemia can result from ___

hyperparathyroidism or hypothyroidism

Hypercalcemia can reduce depolarization and impair action potential generation due to ____

Ca2+ blocking sodium movement through voltage-gated sodium channels.

Hypocalcemia can be caused by ____

vitamin D deficiency, diarrhea, pregnancy, lactation, acidosis, hypothyroidism, and hyperthyroidism

Hypocalcemia increases sodium ion permeability and leads to _____

overexcitation

Magnesium is the cofactor for many ___

enzymes, membrane proteins , and nucleic acids

Intestinal absorption of Mg2+ is regulated by ___

vitamin D

Hypermagnesemia is rare and usually due to kidney problems. However, this can lead to ____

lethargy, muscle weakness, weak reflexes, respiratory depression or failure, etc. b/c Mg2+ inhibits the release of ACh (it is a Ca2+ antagonist)

Hypomagnesemia can cause ____

malabsorption, vomiting, alcohol use disorder, diarrhea, renal disease. Results in hyperirritability of nervous and muscular system (tremors, spasms, tetanus, hypertension, tachycardia)

Phosphate is relatively concentrated in the ___

intracellular fluid in equilibrium as inorganic phosphate, monohydrogen phosphate, and dihydrogen phosphate ions

Most extracellular phosphate is stored in ____

bones and teeth as calcium phosphate

The blood and tissue fluid have pH of ___

7.35-7.45

Our metabolism constantly produces acids:

lactic acid (fermentation), phosphoric acids from nucleic acid metabolism, fatty acids and ketones (fat catabolism), carbonic acid from carbon dioxide

Strong acid - dissociates (ionizes) in water and gives up all of its ___

protons

Weak acid:

ionizes only slightly

Strong base - molecule that has a strong tendency to bind ____

H+ and raise pH

Weak base:

binds less of the available H+

A buffer is any mechanism that resists ____

pH changes by converting a strong acid or base to a weak one

A physiological buffer is a system (respiratory or unrinary) that stabilizes ____

pH by controlling the body's output of acids, bases, or CO2

A chemical buffer is a substance that binds H+ and removes it from solution as its ____

concentrations rise, or releases H+ into solution as its concentration falls

Intercalated type A cells of distal convoluted tubule and collecting ducts respond to increased [H+] by:

secreting H+ into the filtrate and synthesize new HCO3- to be absorbed into the blood

Intercalated type B cells of distal convoluted tubule and collecting ducts respond to decreased [H+] by:

absorbing H+ into the blood from filtrate and synthesize new HCO3- to be secreted into filtrate (and excreted)

At rest, aerobic respiration produces ~200 mL/min of CO2 in cells as a ___

waste product

During exercise, additional CO2 produced by body cells enters blood, increasing PCO2 → chemoreceptors in the brainstem, aorta, and carotid bodies are stimulated → this sensory input is relayed to the ____

respiratory center → sends signals to increase breathing depth → CO2 is within homeostasis within a few minutes → no effect on pH of blood (homeostasis!)

The chemical buffering system acts very fast. The function is ___

rapid, but temporary until physiological buffering systems like the lungs and kidneys can permanently eliminate excess acid or base

The bicarbonate buffer system is a solution of carbonic acid and bicarbonate ions. It is the most important buffering system in the ____

extracellular fluid

The phosphate buffer system is the most important buffering system in the ___

intracellular fluid and within renal tubules

Acidosis is a pH below ___

7.35

Alkalosis is a pH above ___

7.45

Acidosis can lead to ___

hyperkalemia

Alkalosis can lead to ___

hypokalemia