Week 2- Renal and Urinary System Regulation

Question 1

osmosis

Answer 1

The net movement of water
molecules through a selectively permeable membrane from an area of higher water concentration to
an area of lower water concentration until equilibrium
is reached.

Question 2

Describe the hormone anti-diuretic hormone (ADH)

Answer 2

a) production and storage of hormone

Produced in the posterior pituitary

b) mechanism(s) of release

When the osmolarity or osmotic pressure of plasma and interstitial fluid increases—that is, when water concentration decreases—by as little as 1%, osmoreceptors in the hypothalamus detect the change. Their nerve impulses stimulate secretion of more ADH into the blood

c) specific action/effect on kidney tubules

ADH stimulates insertion of the aquaporin-2–containing vesicles into the apical membranes via exocytosis.

d) action/effect on electrolytes and/or water movement

It regulates facultative water reabsorption by increasing the water permeability of principal cells in the last part of the distal convoluted tubule and throughout the collecting duct. Increased osmolarity of extracellular fluid or decreased blood volume promotes release of ADH from the posterior pituitary gland.Dehydration. When the body is dehydrated, the concentration of ADH in the blood increases. Overhydration. When the body is overhydrated , the concentration of ADH in the blood decreases.

e) type of water reabsorption which occurs

Facilacted water reabsorption through aquaporins

f) effect on volume and composition

Question 3

Explain how extracellular fluid (ECF) volume is regulated by the anti-diuretic hormone (ADH) for each situation below:

a) an increase in extracellular fluid (ECF) osmotic pressure (decrease in extracellular fluid [ECF] volume)
b) a decrease in extracellular fluid (ECF) osmotic pressure (increase in extracellular fluid [ECF] volume)

Answer 3

a)

b)

Question 4

osmolarity

Answer 4

the concentration of dissolved particles of chemicals and minerals – such as sodium and other electrolytes

high osmolarity has fewer water molecules with respect to solute particles

Question 5

Describe the renin-angiotensin mechanism

Answer 5

a) role in controlling glomerular filtration rate

It decreases the glomerular filtration rate by causing vasoconstriction of the afferent arterioles

b) role of juxtaglomerular apparatus in this mechanism

Juxtaglomerular cells secrete renin

c) mechanism for the release of renin

When blood volume and blood pressure decrease, the walls of the af erent arterioles are stretched less, causing the release of renin

d) action of renin in the blood

Renin clips of a 10–amino acid peptide called angiotensin I By clipping of two more amino acids, angiotensinconverting enzyme (ACE) converts angiotensin I to angiotensin II, which is the active form of the hormone.

e) subsequent conversions of angiotensin I

angiotensin II

f) target glands/tissues of angiotensin II

Adrenal cortex

g) the response of the target glands/tissues and their effect on controlling glomerular filtration rate, blood volume and/or blood pressure.

1. It decreases the glomerular filtration rate by causing vasoconstriction of the af erent arterioles.
2. It enhances reabsorption of Na+ and water in the proximal convoluted tubule by stimulating the activity of Na+–H+ antiporters.
3. It stimulates the adrenal cortex to release aldosterone (al-DOSter-ōn), a hormone that in turn stimulates the principal cells in the collecting ducts to reabsorb more Na+ and secrete more K+. The osmotic consequence of reabsorbing more Na+ is that more water is reabsorbed, which causes an increase in blood volume and blood pressure.

Question 6

atrial natriuretic peptide (ANP)

Answer 6

a) source of the hormone

secreted from the cardiac atria

b) stimuli causing its release

Stretching of atria of heart stimulates ANP secretion.

c) action/effects on nephron

Suppresses reabsorption of Na+ and water in proximal tubule and

collecting duct Relaxation of mesangial cells in glomerulus increases capillary surface area available for filtration.

d) action/effects on other hormones adjusting glomerular filtration rate

inhibits secretion of aldosterone and ADH

Question 7

obligatory water reabsorption and facultative water reabsorption.

Answer 7

In obligatory water reabsorption water is “obliged” to follow the Na⁺. More substances move across the membranes of the proximal convoluted tubule than any other portion of the nephron.

Facultative reabsorption, is based on need and occurs in the collecting ducts and is regulated by ADH

Question 8

Osmotic diuretic

Answer 8

These drugs are compounds which are filtered in the glomerulus but cannot be reabsorbed because there are no pumps in the nephron wall which will remove them from the filtrate. One example is a simple sugar called mannitol.

i) Which section of the nephron is affected directly (or indirectly) by this drug category?

Tubule (reabsorption)

ii) Will the action impact obligatory and/or facultative water reabsorption? Explain clearly.

Obligatory as the drug will cause more osmosis into the tubule as the concentration in the tubules will be higher

iii) How has osmosis been altered – when compared to a nephron operating in the absence of this diuretic?

Concentration in tubules will be higher

iv) How does this alteration in osmosis affect blood volume?

The blood volume will decrease

Question 9

Thiazide and Thiazide-type Drugs

Answer 9

These drugs are compounds which block the symporters for reabsorption of Na+ and Cl- in the early segment of the distal convoluted tubule.

i) Which section of the nephron is affected directly (or indirectly) by this drug category?

Distal convoluted tubule (reabsorption)

ii) Will the action impact obligatory and/or facultative water reabsorption? Explain clearly.

Facultative water reabsorption because there is no obligatory in the distal end of the tubule.

iii) How has osmosis been altered – when compared to a nephron operating in the absence of this diuretic?

Concentration in tubules will be higher

iv) How does this alteration in osmosis affect blood volume?

The blood volume will decrease

Question 10

Loop (high-ceiling) diuretics

Answer 10

hese drugs are chemicals which reduce the action of the symporters responsible for the reabsorption of Na+, Cl- and K+ in the ascending limb of the Loop of Henle.

i) Which section of the nephron is affected directly (or indirectly) by this drug category?

Loop henle (reabsorption)

ii) Will the action impact obligatory and/or facultative water reabsorption? Explain clearly.

Facultative water reabsorption because it is impacting the cotransporter of the na/cl/k

iii) How has osmosis been altered – when compared to a nephron operating in the absence of this diuretic?

Concentration in tubules will be higher

iv) How does this alteration in osmosis affect blood volume?

The blood volume will decrease

Question 11

Potassium-sparing diuretics

Answer 11

Some of the drugs in this category act by reducing the amount of aldosterone in the blood

i) Which section of the nephron is affected directly (or indirectly) by this drug category?

tubules

ii) Will the action impact obligatory and/or facultative water reabsorption? Explain clearly.

Facultative water reabsorption

iii) How has osmosis been altered – when compared to a nephron operating in the absence of this diuretic?

Concentration in tubules will be higher

iv) How does this alteration in osmosis affect blood volume?

The blood volume will decrease

Question 12

Aquaretics

Answer 12

These drugs block the action of ADH.

i) Which section of the nephron is affected directly (or indirectly) by this drug category?

tubules

ii) Will the action impact obligatory and/or facultative water reabsorption? Explain clearly.

Facultative water reabsorption

iii) How has osmosis been altered – when compared to a nephron operating in the absence of this diuretic?

Concentration in tubules will be higher

iv) How does this alteration in osmosis affect blood volume?

The blood volume will decrease

Question 13

hypovolemia, hypotenson and electrolyte imbalance with duiertics

Answer 13

a) Hypovolemia

refers to a state of low extracellular fluid volume, generally secondary to combined sodium and water loss

If one was to take diuretics while having this, it would drastically make things worse and just lower the extracellular fluid volume, and created more sodium/water loss

b) Hypotension

Low blood pressure. If one was to take diuretics with hypotension it would lower blood pressure even more.

c) Electrolyte imbalance

is an abnormality in the concentration of electrolytes in the body so if one was taking diuretics it would decrease the electrolyte in the blood.

Question 14

hypokaleima

Answer 14

a) a definition of the term

lower than normal potassium level in your bloodstream

b) five behaviours indicative of the imbalance

Muscle twitchs, .Muscle cramps or weakness, Muscles that will not move (paralysis), Abnormal heart rhythms, Kidney problems

c) an explanation for this being the most common electrolyte imbalance caused by diuretics

Some diuretics will inhibit the use of pumps which will bring potassium into the bloodstream, causing less potassium

d) an explanation for the five behaviours which result from excessive loss of potassium

Within muscle cells, potassium helps relay signals from the brain that stimulate contractions

Question 15

water balance

Answer 15

a) a definition of water balance

Homeostasis requires that water intake and output be balanced

b) the fluid volumes of I.C.F., I.S.F. and plasma by percentage of body weight

total body water - 40L 60%

intracellular - 25L 40% of BW

extracellular- 15L 20% BW

interstitial fluid - 12L 80% ECF

plasma - 3L 20% ECF

c) the five functions of water in the body

Regulates body temperature.Moistens tissues in the eyes, nose and mouth.Protects body organs and tissues.Lubricates joints.Carries nutrients and oxygen to cells.Lessens burden the on kidneys and liver by flushing out waste products.

d) the sources and average volumes of fluid intake and output

Fluid intake is from the mouth and is about 2.5L and output is about 2.5L

e) a definition of osmosis

the spontaneous passage or diffusion of water or other solvents through a semipermeable membrane

Question 16

three components of body movements

Answer 16

a) interstitial

Fluid found around cells found in extracellular

b) plasma

Blood found in extracellular

c) intracellular

Fluid inside the cell

Question 17

hydrostaic vs osmostic pressure

Answer 17

a) hydrostatic pressure

The pressure exerted by a fluid, has a ‘pushing’ effect

b) osmotic pressure

the pressure that must be applied to the solution side to stop fluid movement when a semipermeable membrane separates a solution from pure water. Has a ‘pulling’ effect

Question 18

ADH steps of homeostasis

Answer 18

1. Stimulus disrupts homeostasis (Osmolarity of interstitial fluid increase)
2. Osmoreceptors in the hypothalamus put an input of nerve impulses to the control center
3. hypothalamus and posterior pituitary then release ADH
4. Because of this release, principal cells become more permeable to water which increases facultative water reabsorption
5. Osmolarity of interstitial fluid decrease

Question 19

thirst mechasism

Answer 19

a) local and systemic stimuli initiating the mechanism

Increase osmolarity and decrease plasma volume

b) sensory receptors, control center and effectors involved

Basorecpectors in heart/blood, osmoreceptors in hypothalamus, sensory receptors in mouth and pharynx

c) resulting effect on fluid balance

Decrease plasma osomisty

d) feedback mechanism

See powerpoint 139 week 2

e) local and systemic stimuli inhibiting the mechanism

ADH inhibitors, such as alcohol

Na+ reabsorption inhibitors (and resultant H2O reabsorption), such as caffeine or drugs for hypertension or edema

Loop diuretics inhibit medullary gradient formation

Osmotic diuretics: substance not reabsorbed, so water remains in urine; for example, in diabetic patient, high glucose concentration pulls water from body

Question 20

electrolytes

Answer 20

a) a definition of the term

minerals in your body that have an electric charge

b) the major cations of plasma, interstitial fluid, and intracellular fluid

Sodium, potassium and calcium

c) the major anions of plasma, interstitial fluid, and intracellular fluid

Chloride and hydrogen carbonate

d) the relationship between electrolyte concentration and osmotic pressure Because electrolytes dissociate into their component ions, they, in essence, add more solute particles into the solution and have a greater effect on osmotic pressure, per mass than compounds that do not dissociate in water, such as glucose. Higher concentration increase osmotic pressure

Question 21

Describe how blood levels of calcium are regulated by parathormone (parathyroid hormone) and thyrocalcitonin (calcitonin).

Answer 21

When calcium levels are low, the parathyroid releases the parathyroid hormone which osteoclasts to degrade the bones matrix, releasing more calcium in the bloodstream. When there is high levels of calcium, the thyroid will release calcitonin which will prevent the degrading of bones causing less calcium in the bloodstream.

Question 22

Hypertonic dehydration

Answer 22

a) definition

a. More water is lost than solute (primarily sodium) creating a fluid volume deficit and a relative solute excess
b. Solute ( sodium or glucose more commonly) can also be gained in excess of water creating a similar imbalance
c. Serum osmolality is elevated, resulting in hypertonic extracellular fluid that pulls fluid into vessels from cells by osmosis and causes the cells to shrink and become dehydrated

b) primary imbalance of concern

Fluid loss is both extracellular and intracellular

c) describe three primary causes

1) Inadequate fluid intake
a) Clients who are unable to respond to thirst independently (infants, elderly, disabled, and bedridden), who have nausea, anorexia, or dysphagia, or who are NPO without IV fluid replacement are at risk to develop fluid volume defecit
b) Decreased water intake results in increased ECF solute concentration, which leads to cellular dehydration
c) A client can go several weeks to months without food, but only two or three days without water
2) Severe or prolonged isotonic fluid loss
a) May occur in conditions such as vomiting and diarrhea and eventually result in loss of more water than solute
b) ECF becomes hypertonic as compensatory mechanisms are exhausted, and the body has no more water to conserve through the kidneys
c) The hypertonic ECF then begins to draw water from the cells, dehydrating them as well
3) Watery diarrhea causes loss of more water than electrolytes

d) describe and explain the replacement solutions used

HYPOTONIC IVS FOR HYPERTONIC DEHYDRATION

1) 5% dextrose in water (D5 W): although 5% dextrose (D5 W) is isotonic in the IV bag, it has a hypotonic effect in the body; the dextrose is quickly metabolized once infused intravenously, leaving free water that shifts by osmosis from vessels into cells; for each litre of D5 W, roughly 2/3 enters cells and 1/3 remains in extracellular space
2) 0.45% saline (1/2 NS) and 0.225 saline (1/4 NS): these fluids provide free water to cells as small amounts of sodium and chloride; approximately 1/2 of each liter infused moves into cells and 1/2 remains in extracellular space

Question 23

isotonic dehydration

Answer 23

a) definition

Fluid and solute are lost in proportional amounts, thus serum osmolality remains normal and no osmotic force is created. b. Intracellular water is not disturbed and fluid losses are primarily ECF (especially the vascular volume), which can quickly lead to shock

b) primary imbalance of concern

Isotonic fluid loss is primarily an extracellular fluid loss that requires extracellular fluid replacement, with emphasis on the vascular volume

c) describe three primary causes

1) Hemorrhage results in loss of fluid, electrolytes, proteins, and blood cells in proportional amounts, often resulting in inadequate vascular volume

2) Gastrointestinal losses (vomiting, continuous NG suction, diarrhea, drainage from fistulas and tubes) contain abundant electrolytes; thus GI fluid and electrolytes tend to be lost in fairly proportional amounts
3) Fever, environmental heat, and diaphoresis result in profuse sweating, which causes water and sodium loss from the skin in fairly equal proportions

4) Burns (especially large burns) initially damage skin and capillary membranes, allowing fluid, electrolytes, and proteins to escape into the burned tissue area, which often results in inadequate vascular volume

d) describe and explain the replacement solutions used

1) Normal saline (NS; 0.9% NaCl): sodium and chloride in water with the same osmolality as normal plasma; NS provides no calories or free water (water without solute)
2) Ringer’s solution: contains sodium, potassium, calcium, and potassium in similar concentrations to plasma, but no dextrose, magnesium, or bicarbonate; Ringer’s solution provides no calories or free water
3) Lactated Ringer’s solution (LR): contains sodium, chloride, potassium, calcium, and lactate in concentrations similar to normal plasma; LR provides no dextrose, magnesium, or free water

Question 24

4 elctrolyte inbalances and what they are

Answer 24

a) hyponatremia/hypernatremia

Hyponatremia occurs when total body water is in excess of sodium, and hypernatremia develops when body water is relatively decreased in relation to sodium

b) hypochloremia/hyperchloremia

hyperchloremia (elevated serum chloride concentrations) or hypochloremia (reduced serum chloride concentrations

c) hypokalemia/hyperkalemia

Hypokalemia (low potassium), hyperkalemia (high potassium)

d) hypocalcemia/hypercalcemia

Hypocalcemia denotes a lower than average amount of calcium, while hypercalcemia is an overabundance of calcium

Question 25

acid-base balance

Answer 25

a) definition of the terms acid, base and “acid-base balance”

Acid is a solution under 7, Base is a solution over 7.the state of having the right amount of acid and base in the blood and other body fluids

b) definition of the term “pH”

a figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid and higher values more alkaline

c) relationship between hydrogen ion concentration and pH of blood

Hydrogen ions will decrease the pH of blood, making it more acidic

d) normal pH range of blood

7.35 to 7.45

Question 26

three major mechanisms of pH control in the body

Answer 26

1. Buffer systems. Buffers act quickly to temporarily bind H+, removing the highly reactive, excess H+ from solution. Buffers thus raise pH of body fluids but do not remove H+ from the body.
2. Exhalation of carbon dioxide. By increasing the rate and depth of breathing, more carbon dioxide can be exhaled. Within minutes this reduces the level of carbonic acid in blood, which raises the blood pH (reduces blood H+ level).
3. Kidney excretion of H+. The slowest mechanism, but the only way to eliminate acids other than carbonic acid, is through their excretion in urine.

Question 27

buffer

Answer 27

Most buffer systems in the body consist of a weak acid and the salt of that acid, which functions as a weak base. Buffers prevent rapid, drastic changes in the pH of body fluids by converting strong acids and bases into weak acids and weak bases within fractions of a second.

Question 28

acids/bases

Answer 28

a) strong acid

A strong acid is one that completely ionizes (dissociates) in a solution. The strong acids are hydrochloric acid, nitric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, perchloric acid, and chloric acid

b) strong base

a base that is completely dissociated in an aqueous solution. These compounds ionize in water to yield one or more hydroxide ion (OH-) per molecule of base

c) weak acid

an acid that doesn’t produce many hydrogen ions when in aqueous solution. Weak acids have relatively low pH values and are used to neutralize strong bases

d) weak base

upon dissolution in water, does not dissociate completely

Question 29

protein buffere system

Answer 29

protein buffer system is the most abundant buffer in intracellular fluid and blood plasma. For example, the protein hemoglobin is an especially good buffer within red blood cells, and albumin is the main protein buffer in blood plasma. Proteins are composed of amino acids, organic molecules that contain at least one carboxyl group (COOH) and at least one amino group (NH2); these groups are the functional components of the protein buf er system. The free carboxyl group at one end of a protein acts like an acid by releasing H+ when pH rises

Question 30

phsophate buffer systems

Answer 30

The phosphate buffer system acts via a mechanism similar to the one for the carbonic acid– bicarbonate buf er system. The components of the phosphate buffer system are the ions dihydrogen phosphate (H2PO4 −) and monohydrogen phosphate (HPO4 2−).When a strong base in presence, it will use dihydrogen phosphate (H2PO4 −) which is a weak acid to neutralize the base it will result in water and (HPO4 2−). When a strong acid is present, (HPO4 2−) monohydrogen phosphate, which is a weak base, will neutralize the acid.

Question 31

carbonic acid- bicarbonate buffer system

Answer 31

carbonic acid–bicarbonate buffer system is based on the bicarbonate ion (HCO3 −), which can act as a weak base, and carbonic acid (H2CO3), which can act as a weak acid. As you have already learned, HCO3 − is a significant anion in both intracellular and extracellular fluids. Because the kidneys also synthesize new HCO3 − and reabsorb filtered HCO3 −, this important buffer is not lost in the urine. If there is an excess of H+, the HCO3 − can function as a weak base and remove the excess H+, the opposite can error if the

Question 32

how is carbon dioxide brought into the blood

Answer 32

(i) dissolved in solution
(ii) buffered with water as carbonic acid
(iii) bound to proteins, particularly haemoglobin.

Question 33

9. Explain for each of the following changes in blood pCO2 levels:

Answer 33

i) an increase in blood pCO2

a) blood hydrogen ion levels

An increase in the carbon dioxide (CO2) concentration in body fluids increases H+ concentration

b) blood pH

lowers the pH

ii) a decrease in blood pCO2 the effect on:

a) blood hydrogen ion levels

An decrease in the carbon dioxide (CO2) concentration in body fluids decreases H+ concentration

b) blood pH

Rises the pH

Question 34

respirtory system homeostats of pH of blood

Answer 34

i) increased blood hydrogen ion concentration

a) the area in the brain sensitive to the change

Dorsal respiratory group in the medulla oblongata

b) the type of receptors which detect the change

Central chemoreceptors in medulla oblongata, Peripheral chemoreceptors in aortic and carotid bodies

c) the response of the receptors and mechanism involved in initiating a response in the effectors.

Diaphragm

d) the effect on the rate and depth of respirations

Contracts more forcefully and frequently so more CO2 is exhaled

e) the effect on blood carbon dioxide levels

Less carbon dioxide will be found

f) the effect on blood pH

The pH will rise

ii) decreased blood hydrogen ion concentration considering:

a) the area in the brain sensitive to the change

Central chemoreceptors in medulla oblongata

b) the type of receptors which detect the change

Central chemoreceptors in medulla oblongata, Peripheral chemoreceptors in aortic and carotid bodies

c) the response of the receptors and mechanism involved in initiating a response in the effectors.

Diagraphm

d) the effect on the rate and depth of respirations

Contracts less forcefully and less frequently so less CO2 is exhaled

e) the effect on blood carbon dioxide levels

More carbon dioxide in blood

f) the effect on blood pH

pH will lower