Water, Acid/ Base, Electrolyte Balance

Intracellular Fluid

Cytosol inside cells

• combined, forms largest fluid compartment in the body

• holds 2/3 of the body’s water- 63%

Interstitial Fluid

Fluid between cells

• second largest fluid compartment

Fluid compartments- Big to small

• intracellular fluid

• Interstitial fluid

• Plasma

• Lymph

• Transcellular fluids

Transcellular Fluid

Specialized extracellular fluids

• in small extra compartments

• includes CSF, eye humors, and joint synovial fluid

Osmotic Potential

Tendency of water to cross a semipermeable membrane along ion gradients

• controlled by pumping ions

• passive

Ion gradient

Difference salt or ion concentration on the two sides of a membrane

Water enters the body from

Most-to-least

• drinking 60%

• water in moist food 30%

• anabolism 10%

Anabolic Reaction

Synthesis reaction

• builds larger molecules from smaller ones

• produces water

Water leaves the body through

Most-to-least

• urine 60%

• lungs and skin

• feces

• sweat

• catabolism

Catabolic Reaction

Breakdown reaction

• taking larger molecules and making them smaller

• consumes water per bond broken

• triggers thirst

Water Intoxication

Severe over-hydration from rapid water intake

• causes renal shutdown.

Electrolyte

Solute molecule that dissociates into ions when dissolved in water

• ions are electrically charged

Acid

Molecule that releases a proton ($H^+$) in water.

Sodium-Potassium Pump Energy Consumption

Baseline process/ always happening

• consumes $50\%$ of daily caloric intake.

Total Ion Transport Caloric Cost

uses $70\%$ of daily calories

• $50\%$ for sodium

• $20\%$ for other ions

“Hyper”

Too much

• excess fluid signs

• feels like dehydration, thirst, dry mouth, high blood pressure, swelling

“Hypo”

Too little

• low energy symptoms

• feels like “twitchy” nerves- muscle cramps, tingling, even seizures

Addison’s Disease

When the adrenal glands don’t produce enough aldosterone

• causes low sodium

• too much potassium

Hypernatremia

• CAUSES: DEHYDRATION - vomiting, diarrhea, excessive sweating

• EFFECTS: intense THIRST, weakness, nausea, loss of appetite, CONFUSION, MUSCLE TWITCHING, may progress to SEIZURES, loss of consciousness, BRAIN BLEEDING, death

Hyponatremia

• CAUSES: WATER DILUTES THE SALT IN BLOOD, drinking too much water w/o electrolytes, or HEART, LIVER, OR KIDNEY FAILURE, ADDISON’S disease- lack of aldosterone

• EFFECTS: mild nausea, headache, fatigue, confusion, muscle cramps, may progress to seizures, coma, death

Hyperkalemia

• CAUSES: kidneys not excreting enough potassium

KIDNEY DISEASE, ADDISON’S disease

Medications like ACE inhibitors

Dehydration, DIABETES

• EFFECTS: muscle weakness, nausea, SHORTNESS OF BREATH, IRREGULAR HEARTBEAT

Hypokalemia

• CAUSES: losing potassium in urine from DIURETICS, EXCESS ALDOSTERONE, losing potassium through the gut- chronic diarrhea, vomiting, laxatives

• EFFECTS: muscle weakness and cramps, fatigue, IRREGULAR HEARTBEAT, may progress to PARALYSIS

Hypercalcemia

• CAUSES: overactive parathyroid gland- too much PTH- HYPERTHYROIDISM , CANCER, excess vitamin D or calcium supplements

• EFFECTS: excessive THIRST, EXCESSIVE URINATION, nausea, constipation, muscle weakness, BONE PAIN, may progress to confusion, irregular heartbeat

Hypocalcemia

• CAUSES: underactive parathyroid- low PTH- HYPOTHYROIDISM

• EFFECTS: TINGLING IN THE LIPS & FINGERS, DRY SKIN, BRITTLE NAILS, muscle cramps, spasms, may progress to seizures, confusion and DANGEROUS HEART RHYTHM PROBLEMS

Hyperchloremia

• CAUSES: LOSING FLUIDS W/O ELECTROLYTES, TOO MUCH IV SALINE, KIDNEY PROBLEMS, DIURETIC USE, DIABETES

• EFFECTS: FEW SYMPTOMS: thirst, dry mouth, weakness, high blood pressure, RAPID BREATHING, confusion

Hypochloremia

• CAUSES: losing fluids without electrolytes, kidney or heart problems, CHRONIC RESPIRATORY ALKADOSIS

• EFFECTS: few symptoms- METABOLIC ALKADOSIS, muscle cramps, twitching, as progress to seizures

pH Scale

Logarithmic Base-$10$ scale

• each unit change reflects a tenfold ($10\times$) shift in $H^+$ concentration.

Dropping from a pH of 7 to a 5

10 × 10 more acidic = 100x

Dropping from a 5 to a 4 on the pH scale

10 × 1 = 10x more acidic

Rising from an 8 to an 11 on the pH scale

10 × 10 × 10 = 1000 more basic

Neutral pH ($7.0$)

Aqueous state where $H^+$ concentration = $OH^-$ concentration.

Normal Blood pH Range

arterial blood range between $7.35$ and $7.45$.

Antioxidant

Molecule neutralizing free $H^+$ ions and free radicals in fluids.

Medullary Respiratory Regulation

Central chemoreceptors in the brain’s medulla watch hydrogen atoms$H^+$

• triggered when CO2 turns into carbonic acid in the CSF

• drops the pH in CSF

• brain increases ventilation to exhale excess $CO_2$

Renal Ammonium Formation

Renal binding of ammonia ($NH_3$ ) with $H^+$ to trap and excrete $NH_4^+$ in urine.

• in the nephron’s proximal tubule the kidney breaks down glutamine into ammonia $NH_3$ and a hydrogen ion $H^+$

• The ammonia grabs the hydrogen ion and forms $NH_4^+$

• $NH_4^+$ is later excetreted in urine as ammonia chloride

Heat exhaustion

A warning sign

• body still sweats

• feels weak, dizzy, may have cramps

• body temp under 104 degrees

Heat Stroke

Catastrophic thermoregulatory and hydration breakdown, often following heat exhaustion

• a medical emergency

• core temp is 104+ degrees

• body stops sweating, skin gets dry and hot

• can cause confusion, seizures, LOC, coma, death

Fluid Compartments

• Intracellular fluid ($63\%$)

• extracellular fluid ($37\%$) spaces.

Total Body Water

• Averages 63% of male body weight

• $50\%$ of female body weight.

Metabolic water

Water the body makes when it breaks down the food you eat

• byproduct of catabolism

• provides$10\%$ of daily water

Macula Densa Cells

Kidney JGA cells sensing low blood volume and releasing epinephrine.

Juxtaglomerular Granular Cells

JGA cells secreting renin upon epinephrine stimulation.

Renin

Kidney enzyme

• converts angiotensinogen into angiotensin I

Angiotensin-Converting Enzyme (ACE)

Pulmonary and renal enzyme

• converts angiotensin I into active angiotensin II

Angiotensin II

Vasoconstrictor

• raises blood pressure

• stimulates ADH and aldosterone secretion

Antidiuretic Hormone (ADH)

Posterior pituitary peptide

• promotes water retention by inserting aquaporins in collecting ducts

Aquaporins

Membrane water channels

• inserted into nephron collecting ducts by ADH

Aldosterone

Adrenal steroid hormone activating $Na^+/K^+$ pumps to reabsorb sodium and water.

Alcohol (Diuretic Effect)

Diuretic action

• inhibits pituitary ADH secretion.

Caffeine (Diuretic Effect)

Diuretic action

• inhibits renal $Na^+$ reabsorption.

Cation

Positively charged ion- has more protons than electrons b/c it lost electrons

• Na+, K+, calcium- Ca2+ are common examples

• CATions are PAWS-itively charged

Anion

A negatively charged ion- it has more electrons than protons after gaining electrons

• Cl- and bicarbonate are common examples

Sodium ($Na^+$)

Major cation essential for fluid balance and nerve impulses.

Potassium ($K^+$)

Primary cation essential for nerve impulse transmission.

Calcium ($Ca^{2+}$)

Cation required for muscle contraction and intracellular communication.

Hydrogen Ion ($H^+$)

Proton driving ATP synthase and determining body fluid pH.

Chloride ($Cl^-$)

Primary anion maintaining fluid osmolarity.

Acid

Substance that releases $H^+$ in water, lowering solution pH.

Carbonic Acid

Acid produced when $CO_2$ dissolves in water

• quickly breaks down into H+ and bicarbonate

• reversible in lungs to exhale CO2 from alveoli

  
  

Lactic Acid

Acid generated by anaerobic glucose metabolism

• adds extra H+ making blood more acidic

• kidneys dump that H+ in urine

Bicarbonate Buffer System

Primary chemical buffer system

• stabilizes blood pH by binding or releasing $H^+$

Respiratory Center (Medulla)

Brainstem center monitoring $CO_2$

• increases ventilation to expel excess H+ ( makes fluids more acidic)

Renal Excretion of $H^+$

Active tubular secretion of excess $H^+$ for urinary elimination.

Ammonium ($NH_4^+$)

Impermeable ion formed by ammonia ($NH_3$) binding $H^+$

• trapped for urinary excretion