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Chapter 26
Anatomy
| Question | Answer |
|---|---|
| cell function depends on | a continuous supply of nutrients, removal of metabolic wastes, and a physical and chemical homeostasis of the surrounding fluids |
| water mass in healthy young men | 60% of their total weight |
| water mass in healthy young women | 50% of their total weight |
| why do men have a higher water mass than women? | woman have more body fat and men have more muscle (muscle has a higher water content) |
| which body tissue has the lowest water content? | adipose tissue |
| two main fluid compartments in the body | intracellular fluid and extracellular fluid |
| main compartments of ECF | plasma and intersitial fluid (lymph, humors of eye, synovial fluid, GI secretions, etc) |
| electrolytes | dissociate into ions in water; can conduct electrical current |
| nonelectrolytes | dont dissociate into ions in water; cant conduct electrical current (usually organic molecules) |
| what is the one big difference between plasma and interstitial fluid content? | plasma has a high protein content and interstitial fluid does not |
| difference between ions in ICF and ECF | K in ICF > K in ECF Na in ICF < Na in ECF |
| where do exchanges of fluid and solutes between plasma and interstitial fluid take place? | across capillaries |
| where do exchanges between interstitial fluid and ICF take place? | across plasma membranes |
| osmolality of ICF and ECF | equal except briefly when changes occur and then quickly equalize again |
| osmolality | number of solute particles dissolved in 1 kg of water (solvent) |
| osmolarity | number of solute particles present in 1 liter of solution |
| insensible water loss | water lost as vapor from lungs in expired air or water that diffuses directly through skin |
| how is water lost from the body? | insensible water loss, perspiration, feces, urine |
| range of osmolality of body fluids in healthy peeople | 280-300 mOsm/kg |
| what happens if osmolality goes above 300? | thirst is triggered and antidurietic hormone is secreted |
| what happens if osmolality goes below 280? | both thirst and ADH secretion are inhibited |
| what type of receptors stimulate the desire for water? | osmoreceptors and baroreceptors |
| osmoreceptors | when neurons in hypothalamic center lose water by osmosis to hypertonic body ECF, thirst is stimulated |
| baroreceptors | when these receptors sense decreased BP, thirst center neurons are stimulated |
| why can we not survive long without drinking? | we have obligatory water losses and a min daily urine output of 500ml to get rid of metabolic waste products |
| most important control of ADH secretion | osmolality of ECF |
| if osmolality of ECF is increased | ADH secretion increases |
| if osmolality of ECF is decreased | ADH secretion is decreased |
| what else influences ADH secretion? | large changes in blood volume or blood pressure |
| what are the three abnormalities of water balance? | dehydration, hypotonic hydration, and edema |
| dehydration | negative fluid balance; results from water output exceeding water input over a period of time |
| immediate cause of dehydration | decrease in ECF |
| decrease in ECF causes.. | increase of osmotic pressure which causes cells shrinking by osmotic pressure |
| what type of illness can cause dehydration? | prolonged vomiting or diarrhea, severe burns or hemorrhaging |
| what endocrine problems can cause dehydration | diabetes mellitus and diabetes insipidus |
| diabetes mellitus | insulin deficiency or resistance (glucose is osmotic diuretic) |
| diabetes insipidus | caused by ADH deficiency |
| other causes of dehydratio | water deprivation, excessive sweating, diuretic abuse |
| hypotonic hydration | a type of cellular overhydration which leads to nausea, vomiting, muscular cramping, and cerebral edema. damaging to neurons |
| how does hypotonic hydration harm? | usually a decrease of ECF osmolality causes decrease of ADH so that excess water leaves body in urine but when a lot of fluid is consumed this cannot happen fast enough; more water causes cell swelling |
| hyponatremia | normal amount of sodium in plasma but excessive water |
| edema | an atypical accumulation of fluid in the interstitial space, leading to tissue swelling |
| hypotonic hydration leads to increased fluid in.. | all compartments of the body |
| edema leads to increased fluid in.. | only interstitial fluid |
| what causes edema? | any event that causes increased fluid flow out of blood or anything that hinders fluid return to blood |
| ways that edema impairs function | increases distance for nutrients and oxygen to travel from capillary to cell and blood volume and blood pressure decrease which decreases efficiency of cardio system |
| events that cause increased fluid flow out of blood | anything that increases capillary hydrostatic pressure or anything that increases capillary permeability |
| causes of increased capillary hydrostatic pressure | imcompetent venous valves, congestive heart failure, high blood volume, etc. |
| things that hinder fluid return to blood | imbalance between colloid osmotic pressures on the two sides of the capillary membrane |
| hypoproteinemia | causes decrease of osmolality in plasma |
| most important ion involved in fluid and electrolyte balance and overall body homeostasis | sodium |
| why is sodium the primary ion in controlling ECF volume and water distribution in the body? | it's the most abundant cation in ECF and the only one exerting significant osmotic pressure and plasma membranes are relatively impermeable to sodium |
| why does water follow sodium? | osmotic pressure |
| three things that cause adrenal cortex to secrete aldosterone | increased potassium, decreased sodium, and renin-angiotensin system |
| two effects of aldosterone on the kidney tubues | increased sodium reabsorption and increased potassium secretion |
| hyperkalemia | increased potassium |
| hyponatremia | decreased sodium |
| effect of atrial natriuretic peptide | decreases Na and water reabsorption resulting in decreased blood volume and BP |
| buffer | a chemical substance or system that minimizes changes in pH by releasing or binding hydrogen ions |
| acidosis | state of abnormally high hydrogen ion concentration in the ECf |
| alkalosis | state of abnormally low hydrogen ion concentration in ECF |
| acids | proton donors |
| bases | proton aceptors |
| three main chemical buffer systems in the body | bicarbonate buffer system, phosphate buffer system, protein buffer system |
| bicarbonate buffer system | a mixture of sodium carbonic acid and its salt, sodium bicarbonate; buffers both fluid compartments but is only important in the ECF |
| phosphate buffer system | a mixture of sodium dihydrogen phosphate and sodium monohydrogen phosphate; important in buffering ICF and urine but relatively unimportant in plasma |
| protein buffer system | protein molecules can act as weak bases or weak acids; end of amino acid (--COOH) can dissociate to release H |
Created by:
showalterc