ch. 24
Which are effects of dehydration?
-reduced salivation -increased blood osmolarity - reduced blood pressure
Why are electrolytes physiologically important?
-they affect the osmolarity of the body fluids -they are chemically reactive and participate in metabolism -they determine the electrical potential across cell membranes
The typical American diet contains 3 to 7 g of sodium per day. How much sodium per day does a typical adult need?
.5
What can lead to a sudden increase in extracellular potassium?
A transfusion with outdated blood in which K+ has leaked out during storage A crush injury Hemolytic anemia
The atrial and brain natriuretic peptides inhibit the secretion of which of the following?
ADH renin
Most magnesium is found in intracellular fluid complexed with ______.
ATP
Long-term thirst satiation depends on which of the following?
Absorption of water from the small intestine
Which statements are true regarding potassium homeostasis?
Aldosterone stimulates renal secretion of potassium. Potassium homeostasis is closely linked to that of sodium.
Which inhibit ADH release?
Blood osmolarity is too low. Blood volume and pressure are too high.
Why do cells maintain a very low intracellular calcium concentration?
Calcium phosphate crystals would precipitate in the cytoplasm if levels were high.
cells maintain a very low intracellular calcium concentration to avoid crystallization of calcium phosphate. Which mechanisms maintain intracellular calcium concentrations low?
Cells often have a protein called calsequestrin, which binds the stored Ca2+ and keeps it chemically unreactive. Cells actively pump out Ca2+. Cells sequester Ca2+ in the smooth ER and release it only when needed.
What are the primary effects of aldosterone on urine composition?
Decreases NaCl, increases K+, and decreases pH
In which form of fluid imbalance is total body water reduced and osmolarity elevated?
Dehydration (negative water balance)
sodium is more abundant in
ECF
Which are possible causes of hypokalemia?
Excessive use of laxatives Heavy sweating, chronic vomiting or diarrhea Aldosterone hypersecretion Alkalosis
Which causes an increase in the sodium permeability of plasma membranes, making the nervous and muscular systems to be overly excitable?
Hypocalcemia
Which statements are true regarding how water intake is regulated?
Hypothalamic neurons produce antidiuretic hormone (ADH), thus promoting water conservation. Osmoreceptors respond to angiotensin II and to rising osmolarity of the ECF. Cerebral cortex produces a conscious sense of thirst
Which best defines osmoreceptors?
Hypothalamic neurons that respond to increased solute concentration in the extracellular fluid
In which form of fluid imbalance is total body water elevated while osmolarity is reduced?
Hypotonic hydration (positive water balance, water intoxication)
potassium is more abundant in
ICF
Dehydration that occurs in cases such as in profuse sweating affects which of the following fluid compartments?
ICF, blood, & tissue fluid
Which is referred to as the "salt-retaining hormone" because it plays the primary role in adjusting sodium excretion?
aldosteron
Estrogen causes women to retain salt and water during pregnancy by mimicking the effects of which other steroid hormone?
aldosterone
Which is referred to as the "salt-retaining hormone" because it plays the primary role in adjusting sodium excretion?
aldosterone
Increased blood osmolarity stimulates hypothalamic osmoreceptors. This triggers the posterior pituitary to release which of the following
antidiuretic hormone- adh
In response to ADH release, collecting duct cells in the kidneys increase their expression of proteins called ________. These proteins act as water channels and allow the kidneys to reabsorb more water and produce less urine.
aquaporins
water moves by capillary filtration from the ____ to the_____-
blood tissue fluid
Which are affected by aldosterone?
blood pressure urine volume blood volume
Which is a cation that lends strength to the skeleton, activates muscle contraction, serves as a second messenger for some hormones and neurotransmitters, and is an essential factor in blood clotting?
calcium
etany occurs when the plasma concentration of which ion drops to 6 mg/dL?
calcium
Potassium imbalances are the most dangerous of all electrolyte imbalances. What is the most serious consequence of potassium imbalance?
cardiac abnormlalities
in___water diffuses through the epidermis and evaporates.
cutaneous transpiration
Total body water is reduced; ECF becomes hypertonic.
dehydration
water moves by osmosis from the ______ to the _______
digestive tract bloodstream
Water balance is most directly tied to which of the following?
electrolyte balance
Which term is used to refer to the ions that participate in important metabolic and physiological processes?
electrolytes
Hypertonic =
elevated
Mimics the effect of aldosterone and causes women to retain water during pregnancy and part of the menstrual cycle
estrogen
blood plasma is a type of
extracellular fluid
transcellular fluid is a type of
extracellular fluid
Most of the body's magnesium is lost in which of the following?
feces
a person in a state of ____ when daily gains and losses are equal
fluid balance
The blood, lymph, tissue fluid, and transcellular fluid are all examples of which of the following?
fluid compartments
Pulmonary and cerebral edema are among the most serious effects of which of the following?
fluid excess
the kidneys can't compensate for:
for inadequate intake
Promotes sodium reabsorption and edema
glucocorticoid
the kidneys can compensate for:
high fluid intake through diuresis
The concentration gradient for K+ across the membrane becomes steeper, resulting in hyperpolarization. This makes neurons and muscle cells less excitable.
hyperkalemia
What stimulates the secretion of aldosterone?
hyperkalemia hypotension hyponatremia
Which term refers to a plasma sodium concentration in excess of 145 mEq/L?
hypernatremia
Which most often results from heavy sweating, chronic vomiting or diarrhea, excessive use of laxatives, aldosterone hypersecretion, or alkalosis?
hypokalemia
Which term refers to a plasma sodium concentration less than 130 mEq/L
hyponatremia
What stimulates the secretion of aldosterone? Select all that apply.
hyponatremia hypotension hyperkalemia
Total body water is elevated; ECF becomes hypotonic.
hypotonic hydration
What might happen if you lost large volumes of water and salt and then drank large quantities of plain water?
hypotonic hydration
Which term (also called water intoxication or positive water balance), refers to a condition in which more water than sodium is retained or ingested?
hypotonic hydration
Total body water is reduced; ECF remains isotonic.
hypovolemia
Which term is another name for volume depletion? This occurs when proportionate amounts of both water and sodium are lost without replacement.
hypovolemia
Even though aldosterone ______ the tubular reabsorption of sodium and water, this is offset by a(n) ______ in GFR; thus there is only a small ______ in urine output.
increases; increase; decrease
Hypercalcemia causes which of the following?
inhibition of depolarization of nerve and muscle cells Reduced sodium permeability of plasma membranes Muscular weakness, depressed reflexes, and cardiac arrhythmia
output through the breath and cutaneous transpiration is called
insensible water loss
Which represents the largest fluid compartment in the body?
intracellular fluid
What happens to ECF osmolarity during dehydration?
it increases
Which statement about dehydration is true?
it raises blood osmolarity
Fluid deficiency can cause serious effects. For example, circulatory shock may be caused by which of the following?
loss of blood volume
Which is a common effect of hypokalemia?
loss of muscle tone
Which is produced as a by-product of dehydration synthesis reactions and aerobic respiration?
metabolic water
Which term refers to water formed by dehydration synthesis and aerobic respiration?
metabolic water
Which inhibits Na+ and water reabsorption and lowers the blood pressure?
natriuretic peptides
Which are possible effects of fluid deficiency?
neurological dysfunction circulatory shock
isotonic
normal
_____________ output that is relatively unavoidable: expired air, cutaneous transpiration, sweat, fecal moisture, and the minimum urine output, about 400 mL/day, needed to prevent azotemia.
obligatory water loss
Which is the same in the ICF and in the blood plasma?
osmolarity
Fluid intake is governed by thirst and it is regulated by a group of hypothalamic neurons called , __________which respond to angiotensin II and to rising osmolarity of the ECF.
osmoreceptors
How does water move from the digestive tract to the bloodstream?
osmosis
If a local imbalance between the intracellular and extracellular fluid occurs, water movement called ______ restores the balance. This depends on the relative concentration of solutes in each compartment.
osmosis
By which means can water move from one fluid compartment to another?
osmosis capillary filtration
If the osmolarity of the tissue fluid rises, water moves ______ the cells.
out of
Which hormone plays a major role in calcium homeostasis?
parathyroid hormone
Which term refers to water that is taken into the body in food and drink?
performed water
Prolonged, heavy work increases which of the following? Select all that apply.
perspiration respiratory loss
Which ion is the greatest determinant of intracellular osmolarity and cell volume?
potassium
which electrolyte imbalance is the most dangerous
potassium
Water intake totals about 2500 mL/day. The combination of water from food (about 700 mL) and drink (about 1600 mL) is known as
preformed water
Reduces sodium reabsorption and has a diuretic effect
progesterone
Neurons and muscle cells depolarize suddenly and fire action potentials. Synchronous activation of cardiac muscle cells can lead to cardiac arrest
rapid-onset hyperkalemia
hypotonic
reduced
Fluid intake is governed mainly by thirst. Which of the following can make a person thirsty?
reduced blood pressure
Dehydration ______ blood volume and ______ blood osmolarity.
reduces, raises
Aldosterone stimulates which of the following?
renal section of potassium renal reabsorption of sodium
When we are thirsty, we salivate less because osmoreceptor response inhibits ___________, and also because the lower capillary blood pressure and higher blood osmolarity in a dehydrated person, leads to a decrease in saliva production.
salivary glands
Which type of water loss is noticeable output, particularly through the urine and in case of sufficient sweating to produce obvious wetness of the skin?
sensible
Aldosterone, antidiuretic hormone, and the natriuretic peptides help maintain concentrations which of the following?
sodium
During dehydration, urine volume decreases and more body water is retained. This is often due to increased reabsorption of which of the following?
sodium
The most abundant solute particles are electrolytes, especially potassium in the intracellular fluid (ICF) and ______ in the extracellular fluid (ECF).
sodium
Which ion is the most significant solute in determining total body water and the distribution of water among fluid compartments?
sodium
Changes in urine volume are often linked to adjustments in which of the following?
sodium reabsorption
Voltage-gated sodium channels inactivate. This prevents the firing of action potentials.
sow-onset hyperkalemia
When a person is thirsty, the osmoreceptor response leads to ______ output from the hypothalamus that inhibits salivation.
sympathetic
Which compartment would fluid accumulate during edema
the tissue fluid comp.
Which term is a catch-all category for cerebrospinal, synovial, peritoneal, pleural, and pericardial fluids; vitreous and aqueous humors of the eye; bile; and fluid in the digestive, urinary, and respiratory tracts?
transcellular fluid
Which is an example of insensible water loss?
transpiration of water from the skin
Water output is primarily controlled through variations in which of the following?
urine volume
If the body has retained too much sodium and water, but the ECF remains isotonic, the person has which of the following?
volume excess
Which can result from aldosterone hypersecretion or renal failure?
volume excess
total body water is elevated; ECF remains isotonic.
volume excess
Which are types of fluid excess?
volume excess hypotonic hydration
Sodium is actively pumped across membranes. What compounds passively follow it?
water and chloride
Which of the following best defines cutaneous transpiration
water loss through skin
Which are examples of sensible water loss?
water loss through: urine & profuse sweating
What are possible consequences of hypernatremia? Select all that apply.
water retention edema hypertension
Calcium homeostasis is regulated by which hormones?
PTH Calcitriol Calcitonin
Calcium does which of the following?
Participates in muscle contraction Participates in bone and tooth development Acts as second messenger and activates exocytosis during neurotransmission Acts as a factor for blood clotting
What are possible effects of hypokalemia?
Reflexes may become depressed. Electrical activity of the heart becomes irregular. Neurons become hyperpolarized and are less excitable.
Which occurs when blood volume and pressure are too high?
Release of ADH is inhibited.
Which statement is correct regarding the relative abundance of electrolytes in the ECF and ICF?
Sodium is more abundant in the ECF potassium is more abundant in the ICF.
Which determines the direction and extent of osmosis between the intracellular and extracellular compartments
Solute concentrations in the various compartments
Which are fast-acting stimuli that cause a temporary, short-term inhibition of thirst?
Moistening the mouth Cooling the mouth Distension of the stomach
The simplest cause of dehydration is a lack of drinking water. Which of the following can also cause dehydration? Select all that apply.
Overuse of diuretics Cold or hot weather Diabetes mellitus Profuse sweating
A newborn baby's weight is as much as 75% water, whereas obese and elderly people's weight is as little as
45% water
Match each fluid compartment with the percentage of the body water that it contains. ICF- Tissue fluid: Blood plasma & lymph: Trancellular fluid:
65% 25% 8% 2%
Which regulate sodium homeostasis?
Antidiuretic hormone Aldosterone Natriuretic peptides
The water content (as a percentage of total body weight) of a 70 kg young male is which of the following?
Around 55 - 60% of total body weight
Which best describes how aldosterone acts as the "salt retaining hormone"?
It increases the number of Na+-K+ pumps in the nephron.
Which are important functions of sodium?
It participates in cotransport of glucose, K+ and Ca+. It participates in muscle and nerve depolarization. It is involved in generating body heat via the Na-K pump.
Which are important functions of sodium?
It participates in muscle and nerve depolarization. It is involved in generating body heat via the Na-K pump. It participates in cotransport of glucose, K+ and Ca+.
Which are functions of potassium?
It plays a role in cotransport and thermogenesis via the Na+- K+ pump. It helps produce the resting membrane potentials and action potentials of nerve and muscle cells. It is an essential cofactor for protein synthesis and some other metabolic processes. It is the greatest determinant of intracellular osmolarity and cell volume.
How does blood plasma differ from the intracellular fluid?
K+ concentration is lower in plasma. Na+ concentration is higher in plasma. Ca2+ concentration is higher in plasma.
Why do people salivate less when they are thirsty?
Lower capillary blood pressure and higher osmolarity of the blood leads to a decrease in saliva production. Sympathetic output from the hypothalamus inhibits the salivary glands.
Long-term satiation of thirst depends on which of the following?
Lowering of blood osmolarity
Which best describes the role of the kidneys in maintaining water balance during dehydration?
The kidneys can slow down the rate of water and electrolyte loss through changes in urine volume and composition.
types of transcellular fluids.
Vitreous and aqueous humors of the eye Bile and fluid in the digestive, urinary, and respiratory tracts Cerebrospinal, synovial, peritoneal, pleural, and pericardial fluids
Which can cause hypotonic hydration?
adh hyper secretion
