final exam

• Aqueous solution


  Internal environment of the human body is an aqueous (watery) solution
• Water


  • Major solvent in the body
  • Contains solutes like electrolytes—any mineral with a charge
• Electrolytes


  Na+, Cl–, K+, Ca++
• Water movement


  1. Moves between different body compartments via osmosis

  2. Moves from areas of lower solute concentration toward areas of higher solute concentration
• Majority of body mass is water
• Water content


  • Infants ~75% of body mass is water
  • Adults 50–60% of body mass is water
  • Teeth and adipose 8–10% water
  • Brain and kidneys 80–85% water
• Fluid compartments


  Contain body fluids separated from each other compartment by a physical barrier
• Fluid compartments


  • Intracellular Fluid (ICF)—all fluid within cells
  • Extracellular Fluid (ECF)—fluid that surrounds all cells
• Intracellular Fluid (ICF)


  • Two-thirds of total water in human body
  • Mainly cytosol and cytoplasm found in cells
  • Regulated to maintain health of cells
• Extracellular Fluid (ECF)


  • One-third of total water in human body
  • 20% of ECF is plasma
  • 80% of ECF is interstitial fluid (IF)
• Interstitial fluid (IF)


  • Includes cerebrospinal fluid (CSF), lymph, synovial fluid, pleural fluid, pericardial fluid, peritoneal fluid, and aqueous humor
• Composition of bodily fluids


  • Main components of ECF, plasma and interstitial fluid (IF) are similar in composition
  • ICF has higher concentration of potassium, phosphate, magnesium, and protein than ECF
  • Bodily fluids are electrically neutral
  • Maintained by sodium-potassium pumps
• Fluid movement between compartments


  1. Hydrostatic and osmotic pressure gradients determine where fluid will move

  2. If hydrostatic pressure is greater than osmotic pressure, fluid leaves capillary

  3. Amount of fluid filtered is proportional to size of gradient
• Osmotic gradients


  1. Draw fluid toward areas of higher solute concentration

  2. Water moves toward areas of greater solute concentration or lower water concentration

  3. Water moves between ICF and ECF due to osmosis

  4. Water will move between compartments to replace water that tissues have lost
• Solute movement between compartments


  1. Active transport can be used to move solutes against a concentration gradient

  2. Passive mechanisms can be used to allow solutes to move down a concentration gradient
• Water balance: regulation of water intake


  1. Loss of water should be roughly balanced by water intake daily

  2. Water gained by ingestion (main method), and cellular respiration

  3. Water intake regulated by osmoreceptors in hypothalamus
• Water intoxication


  • Results from consumption of too much pure water
  • Consuming pure water decreases osmolarity of ECF
  • This leads to increased volume of fluids like CSF
  • The cranial cavity is unable to accommodate increased volume and pressure placed on brain and brainstem may become deadly
• Regulation of water output


  1. Water is lost via urination (main method), defecation, evaporation, sweating, and exhalation

  2. Excessive water loss can lead to decreased blood pressure

  3. Hypothalamus detects loss with osmoreceptors
• Role of ADH


  • Antidiuretic Hormone (ADH) released in response to elevated blood osmolarity
  • Promotes insertion of aquaporins in collecting ducts
  • Allows kidneys to reabsorb additional water
  • Also promotes vasoconstriction of arterioles
• Role of electrolytes


  • Transmission of action potentials
  • Enzymatic function
  • Urine formation
  • Muscle contraction
  • Release of hormones from endocrine glands
  • pH regulation
• Sodium


  • Most common ion in ECF
  • Plays a role in action potentials, urine formation, bodily fluid osmolarity, muscle contraction, and membrane transport
  • Excess is cleared in urine
  • Hyponatremia—low blood levels of sodium
  • Hypernatremia—high blood levels of sodium
• Potassium


  • Most common ion in ICF
  • Plays a role in resting membrane potential, action potentials, and muscle contraction
  • Hypokalemia—low blood levels of potassium
  • Hyperkalemia—high blood levels of potassium
  • Can disrupt functioning of nervous system, heart, and skeletal muscles
• Chloride


  • Most common anion in ECF
  • Plays a role in osmotic balance between ICF and ECF, electrical balance of ECF, and neuronal functioning
  • Is also a component of hydrochloric acid in the stomach
  • Hypochloremia—low blood levels of chloride
  • Hyperchloremia—high blood levels of chloride
• Bicarbonate


  • Most common anion in blood
  • Plays a role in buffering the pH of the bodily fluids
  • Carbon dioxide is converted into bicarbonate for transport
  • Conversion occurs in red bloods cells using the enzyme carbonic anhydrase
  • Converted back into carbon dioxide in the lungs for exhalation
• Calcium


  • Mainly contained within bones and teeth
  • Plays a role in muscle contraction, neurotransmitter release, enzyme activity, and blood clotting
  • Absorbed via the intestine using active form of vitamin D
  • Hypocalcemia—low blood levels of calcium
  • Hypercalcemia—high blood levels of calcium
• Phosphate


  • Present in three ionic forms within the body
  • Major component of ICF
  • Component of the matrix of bone and teeth, phospholipids, ATP, nucleotides
  • Plays a role in the buffering body fluids
  • Hypophosphatemia—low blood levels of phosphate
  • Hyperphosphatemia—high blood levels of phosphate
• Calcium


  • Mainly contained within bones and teeth
  • Plays a role in muscle contraction, neurotransmitter release, enzyme activity, and blood clotting
  • Absorbed via the intestine using active form of vitamin D
• Hypocalcemia


  Low blood levels of calcium
• Hypercalcemia


  High blood levels of calcium
• Phosphate


  • Present in three ionic forms within the body
  • Major component of ICF
  • Component of the matrix of bone and teeth, phospholipids, ATP, nucleotides
  • Plays a role in the buffering body fluids
• Hypophosphatemia


  Low blood levels of phosphate
• Hyperphosphatemia


  High blood levels of phosphate
• Regulation of Sodium and Potassium


  1. Homeostatic range maintained by kidneys

  2. Excess of either ion is released in urine

  3. Kidneys reabsorb more if the level of either ion is low

  4. Angiotensin II and aldosterone help the kidney regulate sodium and potassium levels in the blood
• Regulation of Calcium and Phosphate


  1. Parathyroid hormone increases blood calcium and decreases blood phosphate, stimulates osteoclasts to release calcium from bone matrix

  2. Calcitriol aids in calcium absorption in the intestine

  3. Calcitonin decreases blood calcium levels, calcium removed from blood and incorporated into bony matrix
• Acid-Base Balance: pH Scale


  • Maintaining acid-base balance is critical for physiological function
  • pH scale is a measurement of the hydrogen ion (H+) concentration
  • Blood pH range is 7.35–7.45
  • Buffers prevent rapid changes in pH, quickly donate hydrogen ions or remove them from solution, limited capacity
  • Respiratory and urinary systems also help maintain acid-base balance
• Protein Buffer


  • Amino group can accept hydrogen ions if pH is too acidic
  • Carboxyl group can donate hydrogen ions if pH is too alkaline
  • Aids in buffering pH of blood and ICF
  • Protein component of hemoglobin buffers red blood cells during formation of bicarbonate ions
• Bicarbonate-Carbonic Acid Buffer


  • Bicarbonate ions can accept hydrogen ions when pH is too acidic
  • Carbonic acid can donate hydrogen ions when pH is too alkaline
  • Bicarbonate ions can be converted into carbon dioxide, acid can be eliminated by exhalation
• Respiratory Regulation of Acid-Base Balance


  1. If pH is too acidic, hyperventilation occurs, carbon dioxide is exhaled

  2. If pH is too alkaline, hypoventilation occurs, retained carbon dioxide is converted into hydrogen ions
• Renal Regulation of Acid-Base Balance

  1. If pH is too acidic, kidneys increase secretion of hydrogen ions and reabsorption of bicarbonate ions

  2. If pH is too alkaline, kidneys decrease secretion of hydrogen ions and reabsorption of bicarbonate ions
• Acidosis


  Blood pH below 7.35, may lead to suppression of nervous system activity, coma, and death