fluid/acid and base

body fluid

• all the water and dissolved solutes (water is main component)

• Regulatory mechanisms ensure homeostasis since their malfunction may seriously endanger nervous system and organ functioning

Intracellular fluid

• part of the cytoplasm of the cell, accounts for the majority of water (70%)

• composed of water, ions (electrolytes), and other solutes

Extracellular fluid

• accounts for 30% water, fluid found outside of the cell

• composed of water, ions (electrolytes), and other solutes

• Cerebrospinal fluid (brain and SC), Plasma of the blood, Lymph, Synovial fluid

Tonicity

concentration of solution inside the cell

Osmosis

• the primary way in which water moves in and out of body compartments

• a type of passive transport

Isotonic

• no net change in fluid movement because the amount outside is the same as inside of the cell

• homeostasis

Hypertonic

• water moves out, causing cell shrinkage

• dehydration

Hypotonic

• water moves in, causing cell swelling

• fluid intake

kidneys - fluid output

water lost in the form of urine

Inspiration - fluid output

water lost through the skin

Sensible - fluid output

water lost through sweat secreted by the sweat glands contains solutes; NaCl, K+, ammonia and urea

feces - fluid output

small amount of water is lost through defecation from the GI tract

food and beverages - fluid input

make up 90% of water intakes

Cellular respiration - fluid input

makes up 10% of water intake

Hypothalamic osmoreceptors

• regulation of thirst

• trigger the posterior pituitary gland to secrete ADH (antidiuretic hormone)

Arterial and juxtaglomerular apparatus baroreceptors

ADH released into the blood and enters the kidneys (nephron); tells the collecting duct to re-absorb water and not urinate it out

sodium

• Most abundant extracellular ion

• crucial for osmolarity and fluid balance; regulated by aldosterone

chloride

• Most extracellular anion

• Aids in inhibitory effect for cells like neurons and skeletal muscle fibers; Helps balance anions in different compartments

• forms HCl acid in the stomach

potassium

• most abundant in intracellular fluid

• maintains fluid volume, nervous impulse conduction, & muscle contraction

• Exchanged for H+ to help regulate pH in intracellular fluid

• abnormal plasma levels adversely affect cardiac and neuromuscular function

bicarbonate

major component of the plasma acid-base buffer system

calcium

• structural component of bones and teeth

• blood clotting, neurotransmitter release, muscle tone & nerve and muscle function

• most abundant ion in the body

magnesium

• Activates several enzyme systems involved in the metabolism of carbohydrates and proteins

• Needed for operation of the sodium pump

• Important in neuromuscular activity & neural transmission within the central nervous system

phosphate

• present in bones and teeth, phospholipids, ATP, DNA and RNA

• intracellular anion and acts as buffer of H+ in body fluids

acid-base balance

• maintained by controlling the H+ concentration of body fluids, especially extracellular fluid

• Acid releases Hydrogen into a solution

• Base removes hydrogen in a solution

• high amount of hydrogen, low pH and vice versa

Buffer

prevents extreme changes in pH solution by binding to hydrogen and releasing hydrogen

Acidosis

blood pH below 7.35

Alkalosis

blood pH below 7.45

Respiratory System - pH Regulation

Adjusts blood pH by altering CO2 levels through changes in breathing rate

Kidneys - pH Regulation

Regulate pH by reabsorbing bicarbonate and excreting hydrogen ions, thus influencing blood acidity

buffers - pH Regulation

Proteins, bicarbonate, and phosphate systems help stabilize pH by binding or releasing H+ ions