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Physiology Test #4
Terms in this set (331)
only occurs across capillary walls between blood and surrounding tissues
What are the 3 routes of capillary exchange across endothelial cells?
intercellular clefts, fenestrations, and through cytoplasm
What are the mechanisms involved in capillary exchange?
diffusion, transcytosis, filtration, and reabsorption
what is NET filtration equation?
(BHP + ICOP) - (IHP + BCOP)
What is BHP
blood hydrostatic pressure
What is ICOP
interstitial colloid osmotic pressure
What is BCOP
blood colloid osmotic pressure
what pressure drives fluid out (filtration) of capillary (high on arterial end of capillary, low on venous end)?
blood hydrostatic pressure (BHP)
What pressure draws fluid into (reabsorption) capillary (same on both ends)- results from plasma proteins (albumins)- more in blood?
colloid osmotic pressure (COP)
what is the pressure where total outward pressures minus total inward pressures?
NET filtration pressure
What are causes of edema?
increased capillary hydrostatic pressure, loss of plasma proteins, obstruction of lymphatic circulation, increased capillary permeability, poor venous return (CHF), kidney failure, decreased capillary reabsorption
excess fluid in tissue spaces causes low blood volume and low BP
oxygen delivery and waste removal impaired
suffocation is the consequence of what kind of edema?
headaches, nausea, seizures, and coma is consequences of what type of edema?
A gradient which is 7-13 Hg venous pressure towards the heart
What is the thoracic pump-inhalation?
thoracic cavity expands (pressure decreases) abdominal pressure increases, forcing blood upward
Where does gravity drain blood from?
drains blood from the head and neck
Does exercise (increase or decrease) venous return?
When does venous pooling occur?
any state where cardiac output is insufficient to meet metabolic needs
inadequate pumping of heart (MI)
most common type of low venous return shock; loss of blood volume; trauma, bleeding, burns, dehydration
type of low venous return shock, tumor or aneurysm
obstructed venous return shock
type of low venous return shock; long periods of standing, sitting or widespread vasodilation
venous pooling (vascular) shock
loss of vasomotor tone, vasodilation; caused from emotional shock to brainstem injury
bacterial toxins trigger vasodilation and increases capillary permeability
Severe immune reaction to antigen, histamine release, generalized vasodilation, increased capillary permeability
hemostatic mechanisms may bring about recovery
lifethreatening positive feedback loops occur - "snowball effect", decreased CO -> myocardial ischemia and infarction -> decreased CO
transient ischemic attacks, mini stroke
cerebral vascular accident (stroke)
- brain infarction caused by ischemia (atherosclerosis)
+ effects range from unnoticeable to fatal
+ recovery depends on surrounding neurons, collateral circulation
Area on base of brain that is formed from anastomosis of basilar and paired internal carotid aa
circle of willis
enzyme destroys bacterial cell walls
phagocytize antigen - antibody complexes, allergens, inflammatory chemicals and anti parasitic effects
aggregate and release enzymes
aid mobility and action of WBC's by the release of:
histamine (vasodilator) increases blood flow to infected tissue
heparin (anticoagulant) prevents immobilization of phagocytes
a vasodilator that increases blood flow to infected tissue
an anticoagulant that prevents immobilization of phagocytes
natural killer (NK) cells, nonspecific defense, large cells lyse host cells infected with viruses or cancerous
circulating precursors to macrophages
What is the defensive response to tissue injury?
limits spread of pathogens, then destroys them; removes debris, initiates tissue repair
What are the cardinal signs of inflammation?
redness (erythema), swelling (edema), heat, pain
What is caused by inflammatory chemicals (bradykinin, prostaglandins) secreted by damaged cells, pressure on nerves?
What is secreted by damaged cells, mast cells, basophils, lymphocytes, macrophages, and platelets that stimulates vasodilation that leads to hyperemia?
bradykinin, histamine and leukotrienes
What is hyperemia?
causes redness and heat, increases local metabolic rate, promotes cell multiplication and healing, dilutes toxins, provides O2, nutrients, and waste removal
- increases permeability of blood capillaries
- allows blood cells, plasma chemicals into tissue
- clotting sequesters bacteria, forms scaffold for tissue repair
- causes swelling that decreases venous flow, increases lymphatic flow that favors removal of bacteria and debris
leukocytes adhere to blood vessel walls (cell adhesion molecules)
leukocytes squeeze between endothelial cells into tissue space
leukocytes are attracted to inflammatory chemicals
polypeptides secreted by cells invaded by viruses
What is the antiviral effect?
- generalized protection
- interferons diffuse to neighboring cells and stimulate them to produce antiviral proteins
- activate NK cells and macrophages - destroy infected host cells
group of proteins in blood that must be activated by pathogens to exert their effect
What are the pathways of the complement system?
classic vs. alternate
What are the mechanisms of action of complement system?
- enhanced inflammation (stimulates release of inflammatory chemicals)
- opsonization (promotes phagocytosis) [sugar coating]
- cytolysis (membrane attack complex)
can do more good that harm
- accelerates metabolic rate and tissue repair
- inhibits pathogen reproduction
secreted by macrophages, stimulates anterior hypothalamus to secrete PGE which resets body thermostat higher - 102 degree F
results from prior exposure, protects against only a particular (specific) pathogen (disease causing antigen); in the immune system
specific (adaptive) defense (immunity)
triggers an immune response, complex molecules > 10,000 amu, unique structures, antigenic determinants (parts)
too small, host macromolecule must bind to them to stimulate immune response
What is the antibody structure?
4 protein chains, 2 heavy (longer-inner) and 2 light (shorter-outer), each chain has a constant and variable region, the variable regions form the antigen-binding site
by amino acid sequences of C (Constant) region of antibody
monomer in plasma; dimer in mucus, saliva, tears, milk, intestinal secretions, prevents adherence to epithelia
monomer, B cell membrane, antigen receptor
monomer; tonsils, skin, mucous membranes; stimulates release of histamines, attracts eosinophils
monomer; 75-85% circulating, crosses placenta to fetus, secondary immune response, binds complement
IgG, antibodies, agglutinins
monomer; B cell membrane, antigen receptor; pentamer in plasma, primary immune response, agglutination
dna segments shuffled and form new combinations of base sequences to produce antibody genes
stem cells of fetus colonize thymus for ______ days
__________ stimulate maturing T cells to produce 10,000-100,000 plasma membrane proteins, antigen receptors
antigen receptors in place
upon binding to antigen, cell divides rapidly, forms a ______ of T cells with identical receptors
destruction of clones in fetus capable of responding to self-antigens, leaves the body in a state of self-tolerance
Where are the sites of development for B lymphocytes?
fetal stem cells in liver, bone marrow, junction of small and large intestine and appendix
How do B cells clone?
synthesize antigen receptors, divide rapidly, produce immunocompetent clones
what is MHC
major histocompatibility complex
What are antigen-presenting cells (APCs)?
cells that process an antigen and display it to a T cell (B cells and macrophages)
Hormone like messengers between lymphocytes
produced by lymphocytes
produced by macrophages
Role of MHC-I proteins:
- found on nearly all body cells
- display antigens produced by host cells
- stimulate attack by cytotoxic T cells
Role of MHC-II proteins:
- found only on antigen presenting cells
- stimulate helper T cells
tell other cells that antigens sticking out are being transported
T cells in thymus develop receptors for either MHC-I or II proteins
What is humoral immunity?
attack: plasma cells release antibodies, bind to antigen, render it harmless, 'tag it' for destruction
antibodies mask pathogenic region of antigen (attack)
antigen binds to IgM or IgG, antibody changes shape, initiates complement binding; primary defense against foreign cells, bacteria
antibody has 2-10 binding sites, binds to multiple enemy cells immobilizing them
antibody binds antigen molecules not cells, creates antigen-antibody complex, phagocytize by eosinophil
some B cells differentiate into ______
_______ attack and destroy foreign cells and diseased host cells
carry out attack
cytotoxic (killer) T cells
promote cytotoxic T cell action and defense mechanisms
Helper T cells
regulator T cells
descended from killer T cells
memory T cells
CD4 and CD8 proteins that are linked to second messenger system that triggers ________ : activated T cell enlarges, multiplies, forms clone of identical T cells
clonal selection requires _______
what is costimulation?
helper T cell binds to macrophage, macrophage releases interleukin-1, this stimulates helper T cell to release and synthesize receptors for interleukin-2 causes large population of activated T cells
what do helper T cells do for the attack phase?
- secretes lymphokines
- coordinate humoral and cellular immunity
What cells only directly attack enemy cells?
contacts cell with antigen- MHC-I protein complex, release perforin, a protein inserts into enemy plasma membrane, creates holes
lethal hit mechanism
kills target cell by destroying DNA
a lymphokine keeps macrophages in the area
migration inhibiting factor
kills cancer cells in 2-3 days
tumor necrosis factor
a lymphokine keeps macrophages in the area
What is the purpose of regulatory T cells?
prevents autoimmune diseases, as pathogens disappear, slows down immune reaction
production of one's own antibodies or T cells as a result of infection or natural exposure to antigen (produces memory cells)
natural active immunity
production of one's own antibodies or T cells as a result of vaccination (produces memory cells)
artificial active immunity
type of immunity that is temporary, fetus acquires antibodies from mother
natural passive immunity (through placenta, milk)
type of immunity that is temporary, injection of immune serum
artificial passive immunity (snakebite, rabies, tetanus)
excessive immune reaction against antigens that most people tolerate - allergens
What type of hypersensitivity is most common?
Type I (acute) hypersensitivity
occurs in sensitized people allergen caps IgE on mast cells, basophils; release inflammatory chemicals, cause local edema, mucus hypersecretion, congestion; hives, watery eyes runny nose are typical
(most common chronic illness in children) inhaled allergens, histamines, bronchiole constriction
bronchiolar constriction, dyspnea, vasodilation, shock, death; treatment - epinephrine
What is type II hypersensitivity also known as?
type of hypersensitivity where transfusion reactions are an example, IgG or IgM binds to antigens on cells and lyses them through complement fixation
type II hypersensitivity
What is type III hypersensitivity known as?
type of hypersensitivity which is widespread antigen-antibody complexing, complexes trigger intense inflammation, involved in acute glomerulonephritis and in systemic lupus erythematosus
Type III hypersensitivity
type of hypersensitivity with:
12-72 hour delay
- APC's in lymph nodes display antigens to helper T cells, which secrete interferon and lymphokines that activate cytotoxic T cells and macrophages
- cosmetic and poison ivy allergies - haptens
- TB skin test
Type IV hypersensitivity (delayed)
failure of self tolerance, production of autoantibodies
severe combined immunodeficiency disease (SCID)
- hereditary lack of t and B cells
- vulnerability to opportunistic infection
- HIV structure
type of disease that:
- invades helper T cells, macrophages, neutrophils and brain cells by "tricking" them to internalize the viruses by receptor mediated endocytosis
- reverse transcriptase uses viral RNA as template to synthesize DNA, (retrovirus), new DNA inserted into host cell DNA, may be dormant for months to years
What are the signs and symptoms of AIDS?
first symptoms - flulike chills and fever
- AID-related complex (ARC) may appear
- susceptible to opportunistic infections
white patches on mucous membranes may appear
cancer originates in endothelial cells of blood vessels causes purple lesions in skin
how is HIV transmitted?
through blood, semen, vaginal secretions, breast milk, or across placenta
Most common - sex, contaminated blood products, contaminated needles
- not transmitted by casual contact
mixture of gases, each contributes its partial pressure
what is 1 atm. of pressure at sea level?
Partial pressures determine rate of diffusion of gas and gas exchange between blood and alveolus
Composition of air
humidified, exchanges gases with blood, mixes with residual air
gases diffuse down their concentration gradients
amount of gas that dissolves in water is determined by its solubility in water and its partial pressure in air
Factors affecting gas exchange
concentration gradients of gases, gas solubility, membrane thickness, membrane surface area, and ventilation-perfusion coupling
The factor affecting gas exchange that is:
- CO2 is 20 times as soluble as O2
- equal amounts of CO2 and O2 are exchanged, O2 has increased concentration gradient, CO2 has increased solubility
What is membrane thickness for affecting gas exchange
0.5 um thick
What factors in regard to membrane surface area affect gas exchange?
100 ml blood in alveolar capillaries, spread over 70 m2 (size of tennis court)
What factors in regard to ventilation-perfusion coupling affect gas exchange?
areas of good ventilation need good perfusion (vasodilation)
concentration of oxygen in arterial blood
20 ml/dl (98.5% bound to hemoglobin)
each heme group of 4 global chains may bind O2, oxyhemoglobin (HbO2), deoxyhemoglobin (HHb)
binding to hemoglobin
- relationship between hemoglobin saturation and Po2 is not a simple linear one
- after binding with O2, hemoglobin changes shape to facilitate further uptake (positive feedback cycle)
oxyhemoglobin dissociation curve
where is most of carbon dioxide transported
carbonic acid (HCO3-) or bicarbonate
carbonic anhydrase in RBC catalyzes
keeps reaction proceeding, exchanges HCO3- for Cl-
What is O2 unloading?
H+ binding to HbO2 decreases its affinity for O2
- Hb arrives 97% saturated, leaves 75% saturated - venous reserve
- utilization coefficient: amount of oxygen Hb has released
active tissue has decreased P02, O2 is released
what is reverse chloride shift?
Cl- moves out of RBC to replace lost negative bicarbonate ions
active tissue has increased CO2, which raises H+ and lowers pH, O2 is released
RBC's produce this as a metabolic intermediate, BPG binds to Hb and causes HbO2 to release O2 (molecule)
low level of HbO2 (as in active tissue) enables blood to transport more CO2
What in the brain controls unconscious breathing?
nuerons in medulla oblongata and pons
what in the brain controls voluntary breathing?
What does the phrenic nerve do?
it is the main nerve for respiration. constant breathing. It innervates the diaphragm and intercostal nerves go to intercostal muscles
Do you have to have a stimulus from the expiratory center to breathe?
What does the inspiratory center do?
more frequently they fire, more deeply you inhale, longer duration they fire, breath is prolonged, slow rate
sends continual inhibitory impulses to inspiratory center, as impulse frequency rises, breathe faster and shallower
sends continual stimulatory impulses to inspiratory center
- input from limbic system and hypothalamus
- input from airways and lungs
afferent connections to brainstem
excessive inflation triggers this reflex, stops inspiration (animals more than humans)
input where brainstem and arteries monitor blood pH, CO2 and O2 levels
input from chemoreceptors
signals medulla by vagus nerves
signals medulla by glossopharyngeal nerves
Type of peripheral chemoreceptors
aortic and carotid bodies
primarily monitor pH of CSF
caused by failure of pulmonary ventilation
what has the strongest effect on respiration rate?
pH of CSF
what is hypercapnia
greater than 43 mmHg CO2
T/F: CO2 easily crosses blood-brain barrier
What type of chemoreceptors strongly stimulate inspiratory center?
How is respiratory acidosis corrected?
by hyperventilation, pushes reaction to the "left" by blowing off CO2
What is respiratory alkalosis?
- hypocapnia <37 mmHg
- corrected by hypoventilation, pushes reaction to the right
- increases H+, lowers pH to normal
Direct effects of carbon dioxide on respirations
Indirect - through pH
direct - increases CO2 may directly stimulate peripheral chemoreceptors and trigger increases ventilation more quickly than central chemoreceptors
What is the effect of oxygen on respirations
usually little effect, chronic hypoxemia, PO < 60 mmHg
usually due to inadequate pulmonary gas exchange
blueness of skin
pure O2 breathed at 2.5 atm or greater
oxygen toxicity (oxygen excess)
pressure here is usually less
contraction flattens ________
as volume of thoracic cavity increases, negative pressure "pulls" on visceral pleura
decreased intrapleural pressure
lungs expand with the visceral pleura
decreases intrapulmonary pressure
intrapleural minus intrapulmonary pressure
increased intrabdominal pressure forces diaphragm upward, increased pressure on thoracic cavity
contract abdominal muscles
presence of air in pleural cavity, loss of negative intrapleural pressure allows lungs to recoil and collapse
collapse of whole or partial lung
a slippery substance secreted into alveoli to prevent lungs from sticking together
- primary control over resistance to airflow
triggered by airborne irritants, cold air, parasympathetic stimulation, histamine
sympathetic nerves, epinephrine
fills conducting division of airway, cannot exchange gases
conducting division of airway
anatomic dead space
air that actually ventilates alveoli multiplied by the respiratory rate
alveolar ventilation rate
affects on respiratory volumes and capacities
Age, exercise, body size, restrictive disorders, obstructive disorders
What is the importance of Daltons Law?
nitrogen is larger (constitutes 78.6% of atmosphere), more air in the space than in our lungs and mixes with dead air
gases diffuse down their concentration gradients
amount of oxygen Hb has released
low level of HbO2 enables blood to transport more CO2
excessive inflation triggers this reflex, stops inspiration
What are the kidney functions?
filters blood plasma, eliminates waste (excretion), and returns useful chemicals to blood, secretes renin which stimulates aldosterone, regulates blood volume, blood pressure, and body fluid osmolarity, regulates acid base balance
Nitrogenous wastes of kidneys
urea, uric acid, creatinine
concentration of nitrogen wastes (urea) in the blood
blood urea nitrogen (BUN)
Elevated levels (azotemia) of BUN indicate _______
excess production or renal insufficiency
What are the major blood suppliers of the kidney?
- renal artery
- afferent arterioles
- glomerulus (cluster of capillaries)
- efferent arterioles
- peritubular capillaries
- renal vein
Microscopic functional unit of kidney
consists of the renal capsule
blood flows into the renal capsule from the ________ arteriole and fluid is filtered out of the glomerular capillary
T/F: Like other capillaries, pressures determine net filtration (capillary exchange) and only a portion of the fluid (filtrate) exits
cells of the glomerular capsule that have finger-like extensions called pedicels
Unlike most other capillaries, the blood flows from the capillary bed into another ______ rather than into a venule (portal system)
creates a plasma like filtrate of the blood
removes useful solutes from the filtrate, returns them to the blood
removes additional wastes from the blood, adds them to the filtrate
Removes water from the urine and returns it to blood, concentrates wastes.
collects in capsular space, flows into renal tubule
exits the glomerular capsule; longest and most coiled (convoluted) tubule
proximal convoluted tubule (PCT)
initial part of descending limb and part or all of ascending limb, active transport of salts
lower part of descending limb, very water permeable
empties into the collecting duct
distal convoluted tubule (DCT)
what is the flow of gomerular filtrate?
glomerular capsule - PCT - nephron loop - DCT - collecting duct - papillary duct - minor calyx - major calyx - renal pelvis - ureter - urinary bladder - urethra
In glomerular filtration, the efferent arteriole is significantly smaller than the afferent, a larger than average blood hydrostatic pressure occurs in the kidney capillaries. This BHP does drop from one end of the capillary to another, but unlike other capillaries, it doesn't drop enough to allow filtrate to be reabsorbed
What are cortical nephrons (85%)?
- short nephron loops
- efferent arterioles branch off peritubular (surrounding tubule) capillaries
What are juxtamedullary nephrons (15%)?
- very long nephron loops, maintain salt gradient, helps conserve water
- efferent arterioles branch off vasa recta, blood supply for medulla
volume of blood plasma cleared of a waste in 1 minute
what is the equation for GFR?
NFP x Kf = approx. 125 mL per min or 180 L per day
What is the equation for renal clearance?
C = UV/P (U = waste concentration in urine, V = rate of urine output, P = waste concentration in plasma)
filtrate formed per one minute
glomerular filtration rate (GFR)
depends on permeability and surface area of filtration barrier
filtration coefficient (Kf)
consists of cells of the distal convoluted tubule that come near (junta) the glomerular capsule and "touch" the afferent arteriole
juxtaglomerular apparatus (JGA)
the JG cells of the DCT are called the ________ and monitor the GFR, respond to changes in BP
constrict afferent arteriole, dilate efferent (leads to decreased BP and decreased GFR)
increased BP (increased GFR)
dilate afferent arteriole, constrict efferent (leads to increased BP, increased GFR)
decreased BP (decreased GFR)
strenuous exercise or acute conditions (circulatory shock) stimulate afferent ______ to constrict
______ GFR and urine production, redirecting blood flow to heart, brain and skeletal muscles
the JG cells of the arterioles can secrete ______ in response to a BP decrease
blood has unusually high COP here, and BHP is only 8 mmm Hg; this favors reabsorption, water absorbed by osmosis and carries other solutes with it (solvent drag)
- reabsorbs 65% of GF (obligatory) to peritubular capillaries
- great length, prominent microvilli and abundant mitochondria for active transport
- reabsorbs greater variety of chemicals than other parts of nephron
proximal convoluted tubules (PCT)
when transport proteins of plasma membrane are saturated; different value for different substance
what is obligatory reabsorption?
90% of water is reabsorbed in this way
- As solutes are reabsorbed, so it water. (water is "obliged" to follow)
doesn't reabsorb as much as the PCT, but still important. this reabsorption is sometimes called facultative in that how much reabsorption occurs depends on hormonal control
DCT and Collecting Duct
- promotes Na+ reabsorption
- Na+ reabsorption promotes water reabsorption
- water reabsorption decreases urine volume, but increases blood volume (increased BP)
What are the effects of atrial natriuretic factor (ANF)?
- increased BP
- stimulates right atrium to secrete ANF which promotes Na+ and water excretion, decreases BP
What are the effects of ADH (in posterior pituitary)?
dehydration stimulates hypothalamus (osmoreceptors) to stimulate posterior pituitary to release ADH
- ADH increases water reabsorption
Blood osmolarity is at 300 mOsm, so glomerular filtrate is at _______
when does filtrate osmolarity change considerably?
as it passes through the renal tubes
NaCl is reabsorbed by cortical CD and water remains in urine
producing hypotonic (dilute) urine
GFR drops, tubular reabsorption increases and less NaCL remains in CD, ADH increases CD's water permeability, more water is reabsorbed and urine is more concentrated
producing hypertonic (concentrated) urine
recaptures NaCl and returns it to renal medulla
reabsorbs water but not salt (concentrates tubular fluid)
descending limb (countercurrent multiplier)
reabsorbs Na+, K+, and Cl- but not water (maintains high osmolarity of renal medulla and dilutes tubular fluid)
ascending limb (countercurrent multiplier)
water diffuses out of blood while NaCl diffuses into blood
descending capillaries (countercurrent multiplier)
where is countercurrent multiplier occurring?
exchanges by vasa recta in the juxtamedullary capillaries
water diffuses into blood while NaCl diffuses out of blood
highly permeable that accounts for 40% of high osmolarity of medulla
Normal urine volume is ____
Polyuria is ____
Oliguria is ___
< 500 mL/day
Anuria is _____
diabetes with no hyperglycemia or glycosuria
diabetes insipidus (ADH hyposecretion)
diabetes with glycosuria but no hyperglycemia (hereditary deficiency of glucose transporters)
diabetes with hyperglycemia and glycosuria
type of diabetes that is hyper secretion of GH
type of diabetes that is hyper secretion of cortisol
increases urine output and decreases blood volume
- used to treat hypertension and congestive heart failure
- increases GFR and decreases tubular reabsorption
what % of water is ICF and ECF?
65% ICF and 35% ECF (25% tissue, 8% blood plasma & lymph, 2% transcellular fluid)
play a principle role in water distribution and total water content
water that we take in
water that we break down
- from aerobic metabolism
- from dehydration synthesis
Routes of water loss are:
urine, feces, expired breath, sweat, cutaneous transpiration
Respiratory loss increases with .....
cold, dry air or heavy work
perspiration loss increases with ....
hot, humid air or heavy work
what is the equation for renal clearance (C)
decreased blood volume and pressure or increased blood osmolarity
stimulation of thirst center is where
produced in response to decreased BP
produced in response to increased blood osmolarity
signal in response to increased ECF osmolarity
thirst center sends sympathetic signals to salivary glands
inhibition of salivation
short term, fast acting satiation mechanisms
cooling and moistening of mouth, distention of stomach and intestine
long term inhibition of thirst
rehydration of blood
What is the only control over water output?
through variations in urine volume
What is the regulation of output?
- by controlling Na+ reabsorption (changes volume) as Na+ is reabsorbed or excreted, water follows it
- action of ADH (changes concentration of urine)
+ ADH secretion (as well as thirst center) stimulated by hypothalamic osmoreceptors in response to dehydration
-- the effects: slows decrease in water volume and increases osmolarity
What is volume depletion (hypovolemia)?
total body water decreases, osmolarity normal
- i.e. hemorrhage, severe burns, chronic vomiting or diarrhea
total body water decreases, osmolarity rises results from lack of drinking water, diabetes, profuse sweating, diuretics
- infants are more vulnerable
- high metabolic rates demands high urine excretion, kidneys cannot concentrate urine effectively, greater ratio of body surface to mass
- affects all fluid compartments
- most serious effects: circulatory shock, neurological dysfunction, infant mortality
What happens with profuse sweating?
produced by capillary filtration, blood volume and pressure drop, osmolarity rises, blood absorbs tissue fluid to replace loss, fluid pulled from ICF
both Na+ and water retained, ECF isotonic
more water than Na+ retained or ingested, ECF hypotonic, can cause cellular swelling
What are the most serious effects of water excess?
pulmonary and cerebral edema
what are the sodium functions?
- membrane potentials
- accounts for 90-95% of osmolarity of ECF
- Na+ - K+ pump (Na+ in and K+ out)
- NaHCO3- has major role in buffering pH
released with increased BP - kidneys excrete more Na+ and water, thus decreasing BP
ANF (atrial natriuretic factor)
plasma sodium > 145 mEq/L leads to water retention, hypertension and edema
plasma sodium < 130 mEq/L is the result of excess body water, quickly corrected by excretion of excess water
what % of K+ in glomerular filtrate is reabsorbed by the PCT
determines intracellular osmolarity
most abundant cation of ICF
what is the most dangerous imbalance of electrolytes?
What are the effects of hyperkalemia?
- if concentration rises quickly, (crush injury) the sudden increase in extra cellular K+ makes nerve and muscle cells abnormally excitable
- slow onset, inactivates voltage-gated Na+ channels, nerve and muscle cells become less excitable
What are the effects of hypokalemia?
sweating, chronic vomiting or diarrhea, laxatives
- nerve and muscle cells less excitable leading to muscle weakness, loss of muscle tone, decreased reflexes, arrhythmia
most abundant anions in ECF
required in formation of HCl
CO2 loading and unloading in RBC's
______ plays a major role in regulating pH
result of dietary excess or IV saline
result of hyponatremia
functions of calcium
What does calcitonin do in children?
affect bone deposition and resorption, intestinal absorption and urinary excretion
effects of hypercalcemia
alkalosis, hyperparathyroidism, hypothyroidism
- decreased membrane Na+ permeability, inhibits depolarization
- causes muscular weakness, depressed reflexes, cardiac arrhythmias
effects of hypocalcemia?
vitamin D decreases, diarrhea, pregnancy, acidosis, lactation, hypoparathyroidism, hyperthyroidism, increased membrane Na+ permeability, causing nervous and muscular systems to be abnormally excitable
What do very low levels of calcium result in?
tetanus, laryngospasm, death
T/F: Phosphate is a buffer
activates metabolic pathways by phosphorylating enzymes, buffers pH
If plasma concentration drops, renal tubules reabsorb all filtered ______
what hormone increases the excretion of phosphate?
______ are sensitive to pH
What are challenges to acid-base balance?
metabolism produces lactic acid, phosphoric acids, fatty acids, ketones and carbonic acids
The functions of buffers?
- resist changes in pH
function of physiological buffer?
+ system that controls output of acids, bases or CO2
+ urinary system buffers greatest quantity, takes several hours
+ respiratory system buffers within minutes
function of chemical buffer?
- restore normal pH in fractions of a second
- bicarbonate, phosphate and protein systems
bicarbonate buffer system: What is the reversible reaction important in ECF?
CO2 + H2O -> H2CO3 -> HCO3- + H+ (can go either way, lowers or raises pH by releasing or binding H+)
What is the equation for the phosphate buffer system?
H2PO4- <-> HPO4(2-) + H+
Why is the phosphate buffer system important?
important to the ICF and renal tubules where phosphates are more concentrated and function closer to their optimum pH of 6.8
* Neutralizes 2-3 times as much acid as chemical buffers can, collaborates with bicarbonate system
respiratory control of pH
* most powerful buffer system (but slow), the renal tubules secrete H+ into tubular fluid, then excreted in urine
renal control of pH
* H+ diffuses into cells and drives out K+, elevating K+ concentration in ECF
- H+ buffered by protein in ICF, causing membrane hyper polarization, nerve and muscle cells are harder to stimulate, CNS depression from confusion to death
* H+ diffuses out of cells and K+ diffuses in, membranes depolarized, nerves overstimulate muscles causing spasms, tetany, convulsions, respiratory paralysis
* rate of alveolar ventilation falls behind CO2 production
* CO2 eliminated faster than it is produced
respiratory alkalosis (hyperventilation)
* increased production of organic acids (lactic acid, ketones), alcoholism, diabetes, acidic drugs (aspirin), loss of base (chronic diarrhea, laxative overuse)
* (rare) overuse of bicarbonates (antacids), loss of acid (chronic vomiting)
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