Lecture 2 (urinary) -EXAM 5 Flashcards
(132 cards)
1
Q
Kidneys perform a number of key functions:
* What does it regulate? (4)
A
- regulate osmolarity of body fluids by urine water and solute concentrations
- regulate plasma concentrations of Na+, K+, Ca2+, Mg2+, Cl−, HCO3−, phosphate, and sulfate
- regulate the volume of the extracellular fluid by controlling Na+ and water excretion.
- regulate arterial blood pressure by adjusting Na+ excretion and producing various substances (e.g., renin) that can affect blood pressure.
2
Q
Kidneys perform a number of key functions:
* What does it play an essential role in?
* What does it eliminate?
* What does it remove?
A
- play essential role in acid–base balance by altering renal H+ excretion and HCO3− reabsorption.
- eliminate the waste products of metabolism, including urea (the main nitrogen-containing end product of protein metabolism in humans), uric acid (an end product of purine metabolism), and creatinine (an end product of muscle metabolism).
- remove many drugs (e.g., penicillin), drug metabolites, and foreign or toxic compounds.
3
Q
Kidneys perform a number of key functions:
* The major site of what?
* Degrades what?
* What does it synthesize? (2)
A
- major sites of production of certain hormones, including erythropoietin and vitamin D3
- degrade several hormones, including insulin, glucagon, and parathyroid hormone.
- synthesize ammonia, which plays a role in acid base homeostasis
- synthesize substances that affect RBF and Na+ excretion, including arachidonic acid derivatives (prostaglandins and thromboxane A2) and kallikrein (a proteolytic enzyme that results in the production of kinins).
4
Q
When the kidneys fail, a host of problems ensue. What is used to help?
A
Dialysis and kidney transplantation are commonly used treatments for advanced (end-stage) renal failure.
5
Q
Kidneys are highly what?
A
highly vascular & innervated
6
Q
Kidneys:
* Recieve how much CO?
* What are the vessels?
* Richly innervated by what? What does this cause (3)
A
receive ~20% CO
single renal artery > anterior and posterior branch divisions > five segmental arteries
richly innervated by sympathetic nerve fibers who stimulation causes:
* constriction of renal blood vessels and a decrease in renal blood flow (RBF)
* increase in Na+ reabsorption by a direct action tubular cells
* Renin release
7
Q
Afferent (sensory) renal nerves are stimulated by what?
A
mechanical stretch or by various chemicals in the renal parenchyma.
8
Q
Explain the breakout of the arteries and veins of the kidney
* What do you change in order to affect flow?
A
9
Q
What is the functional unit of kidney? Explain the structure and how many are in one kidney?
A
Nephron-> 1 mill/kidney
10
Q
How is vascular system different in cortical nephron and juxtamedullary nephron?
A
- Cortical: only peritubular capillaries
- Jux: peritubular cap. and vasa recta
11
Q
What are the macula densa cells, mesangial cells and granular cells?
A
- Macula densa cells (chemoreceptors): monitor the composition of the fluid in the tubule lumen-> located in DCT or some books say loop of henle
- Mesangial cells: transmit information from macula densa cells to the granular cells
- Granular cells: modified vascular smooth muscle cell; synthesize and release renin
12
Q
What is the equation for excreted?
A
Excreted= filtered-reabsorbed +secreted
13
Q
Urine formation involves what three basic processes?
A
- Glomerular filtration: 20% plasma filtered, remaining 80% flows through the efferent arteriole and into the peritubular capillaries. ~180 L of plasma is filtered per day; body plasma volume filtered 65 times per day.
- Tubular reabsorption: ~178.5 L is reabsorbed. Remaining 1.5 L is excreted as urine. Reabsorbed substances include many important ions (e.g., Na+, K+, Ca2+, Mg2+, Cl−, HCO3−, and phosphate), water, important metabolites (e.g., glucose and amino acids)
- Tubular secretion: route for a substance to enter the renal tubules. Mechanism for selectively eliminating substance from the plasma
14
Q
The functional state of these urine formation processes can be evaluated using several tests based on what?
A
renal clearance concept
15
Q
NOTES
- Glomeruli of cortical nephrons are located where? What are their loops of henle like?
- JM nephrons have glomeruli located where? Waht are their loop sof henle like?
- JM nephrons are what?
- When effective circulating blood volume is reduced, a higher proportion of renal blood flow (RBF) is directed to what?
A
- Glomeruli of cortical nephrons are located in the outer cortex and the loops of Henle are short.
- JM nephrons have glomeruli located deep in the cortex and have long loops of Henle, many extending to the tip of the renal papilla.
- JM nephrons are “salt conserving” and are important for urine concentration.
- When effective circulating blood volume is reduced, a higher proportion of renal blood flow (RBF) is directed to JM nephrons, helping to conserve extracellular fluid (ECF) volume.
16
Q
Glomerular filtration rate is primarily what?
A
- primarily a physical process and does not involve intracellular pumps (no active transport)
- Major force is hydrostatic pressure of blood
17
Q
What are the three layers of the glomerular fitration barrier?
A
- Endothelium: Pores too large to restrict the passage of the smaller plasma proteins.
- Basement membrane: Negatively charged so repels plasma proteins (since proteins are usually - charged)
- Visceral layer of the Bowman capsule: Podocytes, filtration slit, slit diaphragm, meshlike barrier, filtration of small proteins.
18
Q
What is ultrafilrate, filtered and non-filtered?
A
- Ultrafiltrate: filtration of small molecules but restricts the passage of macromolecules
- Filtered: low molecular weight substances that are freely dissolved in plasma and includes various polar organic molecules such as glucose, amino acids, ions peptides, drugs, and waste products (e.g., creatinine and urea).
- Non-filtered: blood cells, large proteins (Proteinuria is the hallmark of glomerular filtration barrier disorder.)-> if damaged to membrane protein will be in urine which is not good
19
Q
What is the effect of molecular size of the glomerular filtration of macromolecules? Inulin?
A
- hemoglobin and albumin are just large enough to avoid filtration at normal glomeruli on the basis of their size
- Inulin: is not reabsorbed or secreted so can measure the rate of clearance
20
Q
What is the effect of electrical charge on glmerular filtration of macromolecules
A
filtration of negatively charged macromolecules (but not small anions) is reduced.
21
Q
Glomerular hemodyamic forces:
* Characterized by what?
* GFR depends on what?
* Average capillary hydrostatic pressure in glomerulus much is what compared to skeletal muscle?
* Capillary hydrostatic pressure declines little because why?
* At efferent end, an increase in COP opposes what?
A
- Characterized by high capillary pressure and low vascular resistance
- GFR depends on Starling forces - balance of hydrostatic & colloid osmotic pressures
- Average capillary hydrostatic pressure in glomerulus much higher than skeletal muscle (55 vs 25 mmHg)
- Capillary hydrostatic pressure declines little because glomerulus contains many (30 to 50) capillary loops in parallel = low resistance to blood flow
- At efferent end, an increase in COP opposes the outward movement of fluid.
22
Q
Using the pictures, explain the difference between skeletal and glomerular capillary?
A
23
Q
A
24
Q
Why is the glomerular filtration hight?
A
the glomerular capillary blood is exposed to a large, porous surface and there is a high transmural pressure gradient favoring filtration.
25
What creates a high capillary hydrostatic blood pressure to drive filtration?
Having an arteriolar resistance vessel at the distal end of the glomerular capillary instead of a venule creates
26
RBF is affected by what? (3)
1) hormones,
2) extrinsic neural stimulation
3) local regulatory factors.
27
Autoregulation of RBF:
* Maintains a constant blood flow during what?
* RBF kept relatively constant when perfusion pressure is varied btw what?
* When the perfusion pressure is raised, what happens? Lowered?
* When MAP is between 80 and 180 mmHg the Glomerular Filtration Rate (GFR) is what?
* When does the GFR cease?
* Maintains a **constant blood flow** during changes in **mean arterial pressure**
* RBF kept relatively **constant** when perfusion pressure is varied from **80 to 180 mm Hg**
* When the **perfusion pressure is raised** the **renal arterioles constrict**, when **lowered they dilate**, thereby maintaining a constant blood flow and capillary pressure.
* When MAP is between 80 and 180 mmHg the Glomerular Filtration Rate (GFR) = **125mL/min**
* GFR ceases at MAP < 50 mm Hg
28
Optimal renal blood flow is maintained by what?
* Optimal renal blood flow is maintained by **autoregulation (intrinsic/local)**
29
What are the two renal intrisic autoregulation mechanism?
Myogenic and tubuloglomerular feedback mechanism
30
What is the myogenic mechanism?
* increase in **pressure stretches** the afferent arteriolar walls which then activate stretch-activated cation channels in the arteriolar smooth muscle cells.
* this causes intracellular Ca2+ to rise, resulting in, **smooth muscle contraction**
* a reduction in vessel lumen diameter which increase resistance/decreased flow
* **Counteracts the effect of high perfusion pressure, which would otherwise have increased RBF.**
31
What is the tubuloglomerular feedback mechanism.
When single-nephron glomerular filtration rate (GFR) is increased—for example, because of an increase in arterial blood pressure—more NaCl is delivered to and reabsorbed by the macula densa, leading to constriction of the nearby afferent arteriole. This negative feedback system plays a role in autoregulation of renal blood flow and GFR.
32
What are the three ways of renal extrinsic regulation?
* Sympathetic nerve stimulation
* hormones/chemicals
* Renal protective mechanism
33
For renal extrinsic regulation: how does sympathetic nerve stimulation work/do?
* **Vasoconstriction of afferent or efferent arteriole = decrease in RBF**.
* Activated under stressful conditions - cold temperatures, deep anesthesia, fearful situations, hemorrhage, pain, and strenuous exercise.
* In these conditions, viewed as an emergency mechanism that helps increase TPR, MAP, CO
34
For renal extrinsic regulation, what hormones/chemicals vasodilate and vasoconstrict?
* **Kidney vasoconstrictors**:adenosine, angiotensin II, endothelin, epinephrine, norepinephrine, ADH
* **Kidney vasodilators:** atrial natriuretic peptide, dopamine, histamine, kinins, nitric oxide, and prostaglandins
35
For renal extrinsic regulation, what is the renal protective mechanism?
* A sustained increase in sympathetic nerve activity or plasma angiotensin II concentration stimulates the production of **renal vasodilator prostaglandins.**
* These prostaglandins oppose the pure constrictor effect of chronic sympathetic nerve stimulation or angiotensin II, such as that seen in chronic heart failure.
* **Prevents too severe a reduction in RBF** in chronic pathological conditions that could cause renal damage.
36
What profoundly affect the GFR?
Changes in glomerular capillary hydrostatic pressure
37
38
Explain the reabsorption and secretion of the different areas in the renal tube
39
Tubular absorption involves what?
involves diffusion and active transport
40
Where is water reabsored? Sodium?
WATER:
* all regions of the renal tubule. Exceptions are ascending limb of the loop of Henle and DCT and CD (unless alsosterone and ADH are secreted)
SODIUM:
* PCT ~65%
* loop of Henle 25%
* remaining DCT and CD (when aldosterone and ADH present)
41
Where is glucose and urea reabsorbed? What is urea dependent on
* **GLUCOSE**: PCT 100%
* **UREA**: PCT via passive transport. Urea reabsorption is dependent on the reabsorption of water in PCT
42
What is load dependence
increase in the filtered load of Na+ from the glomerulus stimulates an increase in sodium reabsorption by the tubule such that the **percent of sodium reabsorbed remains the same**. This phenomenon is called **glomerulotubular balance**
43
What are the characteritics of the PCT?
44
Over 70% of filtered solutes & water reabsorbed along what?
Along PCT: PCT responsible for reabsorbing all of the filtered glucose and amino acids, and reabsorbs the largest fraction of the filtered Na+, K+, Ca2+, Cl−, HCO3−, and water and secretes various organic anions and cations.
45
What is essential for sodium reabsorption? Explain
**Active Na+/K+-ATPase pump is essential for sodium reabsorption.**
* All sodium transport is dependent on the sodium ATPase pumps in the basolateral membrane.
* Sodium reabsorption across the apical membrane is accomplished through Na to solute cotransporters, H+- driven sodium reabsorption, and paracellular Cl–-driven sodium transport.
* Glucose, amino acids, phosphate, and numerous other substances are transported by separate carriers.
46
What are the characteristics of DCT and collecting duct?
47
Small amounts of water and sodium are reabsorbed where? What can cause a major increase?
* Small amounts of water and sodium are reabsorbed in the DCT and Collecting Duct.
* However, ion and water transport in the DCT and collecting ducts can be dramatically increased by presence of certain hormones.
48
What does aldosterone do?
Aldosterone increases Na+ reabsorption as well as K+ and H+ secretion with the secretory effects primarily occurring in the connecting ducts and cortical region of the collecting ducts.
49
What does ADH do?
Arginine vasopressin, also called **antidiuretic hormone (ADH)** increases water permeability in the collecting ducts
50
What are the two type of cells + what do they do in late distal tubule and collecting duct?
51
TUBULE SECRETION:
* The most important constituents secreted are what?
* PCT secretion eliminates what?
* Distal part of DCT and CD are the primary site for what?
* The most important constituents secreted are H+, K+, and Cl−.
* PCT secretion eliminates many toxins and drugs from the blood.
* Distal part of DCT and CD are the primary site for K+ secretion.
52
* In PCT, water reabsorption was what?
* In LoH, water reabsorption is not what?
* In PCT, water reabsorption was obligatory (water followed the solutes).
* In LoH, water reabsorption is not automatically coupled to reabsorption of solutes.
53
In LoH, water reabsorption is not automatically coupled to reabsorption of solutes. Why is this?
Descending limb: water moves out
* Permeable to water
* Impermeable to salts
Ascending limb: salts pumped out
* Impermeable to water
* Permeable to salts (has salt pumps)
54
Explain how we get dilute filtrate and salty medulla
55
Explain how the countercurent multiplier including what is a multiplier and countercurrent
56
What produces osmotically concentrated urine
Arginine vasopressin (AVP/ADH) is one mechanism that produces osmotically concentrated urine
57
What happens in the absence and presence of AVP?
* In the absence of AVP, the kidney collecting ducts are relatively water impermeable.
* In the presence of AVP, collecting duct water permeability is increased
58
If adh is present, do we have concentrated or unconcentrated urine?
concentrated
59
* What is renal clearance used for?
* Clearance is based on what?
* What molecule equals the glomerular filtration rate?
* Renal clearance of a substance is a key clinical measurement
* Renal clearance can also be used as an indirect way to measure glomerular function.
* Clearance is based on the concept that when a substance is excreted in the urine, it is as if a certain volume of plasma was completely cleared of the substance.
* Inulin clearance equals the glomerular filtration rate
60
Because IN is not reabsorbed, secreted, synthesized, destroyed, or stored by the kidney tubules, the filtered IN load equals what?
Because IN is not reabsorbed, secreted, synthesized, destroyed, or stored by the kidney tubules, the filtered IN load equals the rate of IN excretion
61
* Renal titration curves can be used to determine what?
* What is the renal threshold?
* What is splay?
* The plateau of the glucose reabsorption rate is what?
* Who do you see glucosuria in?
* **Renal titration curves** can be used to determine the maximum rate of solute transport **(transport maximum, Tm)** for solutes with saturable transport.
* The plasma solute concentration at which the solute first appears in urine is called the **renal threshold.**
* The glucose reabsorption curve levels off gradually rather than reaching the plateau abruptly. This phenomenon is called **splay** and is due to variability in the tubular transport maxima between nephrons.
* The plateau of the glucose reabsorption rate is the **Tm** for glucose.
* Glucosuria in Diabetes mellitus
62
What is the involunary micturition reflex?
1. Stretch receptors detect filling of bladder, transmit afferent signals to spinal cord
2. Signals return to bladder from spinal cord segments S2 and S3 via parasympathetic fibers in pelvic nerve
3. Efferent signals excite detrusor muscle
4. Efferent signals relax internal urethral sphincter. Urine is involuntarily voided if not inhibited by brain
63
What is the voluntary control of bladder?
1. For vol. control, micturition center in pons recieves signals from stretch receptors
2. If it is timely to urinate, pons returns signals to spinal interneurons that excite detrusor and relax internal urethral sphinceter. Urine is voided
3. If it is untimely to urinate, signals from cerebrum excite spinal interneurons that keep external urethral sphicter contracted. Urine is retained in bladder
4. If it timely to urinate, signals from cerebrum inhibit sacral neurons that keep external sphicter closed. External urethral sphincter relaxes and urine is voided
64
65
Explain the breakdown of total body mass
They have semi permeable membranes
66
What does intetsitial fluid also include? What can it also be called?
* Includes lymph, CSF, synovial fluid, aqueous and vitreous humor (eyes), pleural, peritoneal, and pericardial fluids
* Water continuously exchanges between fluid compartments
* Also called the third space/transcellular fluids
67
As people age, they tend to lose muscle and add adipose tissue; hence what happens?
water content declines with age
68
Explain how plasma and intracellular fluid composition are different?
* Plasma: Increase amount of NaCl, Hco3, and Ca
* Intracellular: K, HPO4 and proteins (anions)
69
Explain what happens when we add a hypotonic, hypertonic and isotonic saline
70
Why is transcellular fluid called the slow extracellular fluid compartment?
Transcellular fluid makes up about 17.5% of total body water by volume, and because of its slow equilibrating properties, it is sometimes called the slow extracellular fluid compartment.
71
Why is the ECF called the fast extracellular fluid compartment?
TheremainingECF compartments (plasma and interstitial fluid) can quickly equilibrate with the ICF. They are often called collectively the fast extracellular fluid compartment
72
* Explain how we keep our fluid balanced through gains and losses
* What is the minimum obigatory urine output?
73
AVP/ADH control of water balance is critical
in regulating what?
extracellular fluid osmolality
74
What hormones are secreted from the posterior pit?
ADH and oxytocin
75
The main mechanism controlling AVP release under ordinary circumstances is what?
is a change in plasma osmolality
76
Explain the relationship between plasma AVP level and plasma osmolality
77
Explain the relationship between urine osmolality and plasma AVP levels
the entire range of urine osmolalities, from dilute to concentrated urine, is a linear function of plasma AVP in healthy people
78
* When plasma osmolality rises, what neurons shrink?
* What stimulates AVP(ADH) release?
* When plasma osmolality rises, neurons called **osmoreceptor cells**, located in the anterior hypothalamus, shrink.
* Extracellular Na+ and Cl− are effective osmoles and thus stimulate **AVP (ADH) release.**
79
Explain what happens when you are dehydrated?
80
Explain how we get the sense of thrist
81
Explain the relationship between plasma arginine vasopressin (AVP) and blood volume
An increased blood volume inhibits AVP release, whereas a decreased blood volume (hypovolemia) stimulates AVP release.
82
* The receptors for blood volume includes what?
* Arterial baroreceptors in the carotid sinuses and aortic arch also reflex change what?
* Decrease in renal blood flow stimulates renin release, which leads to what?
* High circulating level of AVP exerts what?
* The receptors for blood volume include **stretch receptors in the right atrium** of the heart and in the pulmonary veins within the pericardium.
* **Arterial baroreceptors** in the carotid sinuses and aortic arch also reflex change AVP release; however, **a fall in pressure** at these sites stimulates AVP release.
* Finally, a **decrease in renal blood flow** stimulates renin release, which leads to increased angiotensin II production. Angiotensin II stimulates AVP release by acting on the brain.
* high circulating level of AVP exerts a significant **vasoconstrictor effect**, which helps compensate by raising the blood pressure
83
* What determines ECF volume?
* Kidneys excrete only a small percentage of what?
* Glomerulotubular balance prevents what? How?
Na+ content of the ECF compartment determines **ECF volume**
Kidneys excrete only a small percentage of the filtered sodium load.
**Glomerulotubular balance** prevents massive changes in Na excretion.
* tubules increase the rate of Na+ reabsorption when GFR (and thus filtered sodium load) is increased and decrease the rate of Na+ reabsorption when GFR is decreased
84
What are the percentages of filtered load of sodium reabsorbed along the nephron?
85
Extracellular Na+ is regulated by what?
the renin– angiotensin–aldosterone system and atrial natriuretic peptide.
86
Renal sympathetic nerve stimulation
decreases or increases Na secretion?
Decreases
87
Stimulation of renal sympathetic nerves reduces renal Na+ excretion in at least three ways:
1. It produces a **decline in GFR** and renal blood flow, leading to a decreased filtered Na+ load and peritubular capillary hydrostatic pressure, both of which favor sodium reabsorption and thus diminished Na+ excretion.
2. It has a direct **stimulatory effect on Na+ reabsorption** by the renal tubules.
3. It causes **renin release**, which results in increased plasma angiotensin II and aldosterone levels, both of which increase tubular Na+ reabsorption.
88
Activation of the sympathetic nervous
system occurs when?
in a number of stressful circumstances (such as hemorrhage) in which the conservation of salt and water by the kidneys is of clear benefit.
89
Explain the RAAS pathway and what happens?
90
Explain Atrial natriuretic peptide (ANP) and its actions
91
* Distribution of potassium between intracellular and extracellular fluid is what?
* A normal plasma K+ level ranges from what?
* What is hypo and herkalemia?
*Distribution of potassium between intracellular and extracellular fluid is tightly regulated.
* A normal plasma K+ level ranges from **3.5 to 5.0 mEq/L.** By definition, a plasma K+ level below 3.5 mEq/L is **hypokalemia** and a plasma K+ level above 5.0 mEq/L is **hyperkalemia**
92
What is the postassium balance for healthy adult?
93
What are the factors influencing the distribution of potassium between intracellular and extracellular fluids?
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* Abnormal renal K+ excretion is the major cause of what?
* Changes in dietary potassium intake changes what?
* Abnormal renal K+ excretion is the major cause of potassium imbalance.
* Changes in dietary potassium intake change renal potassium excretion in an appropriate direction.
95
What is the percentage of the filtered load of potassium remaining in tubular fluid as it flows down the nephron?
96
What is the effect of increased dietary potassium intake on potassium excretion?
97
* What is an acid? Strong vs weak?
* What is a base? Strong vs weak?
**Acids**: any chemical that releases H! in solution
* **A strong acid**, e.g. hydrochloric acid (HCl), gives up most of its H+, drastically lowers pH of a solution
* **A weak acids**, e.g. carbonic acid HCO3 keeps most H+ chemically bound, does not affect pH much
**Bases**: any chemical that accepts H+
* **Strong bases,** e.g. hydroxide ion (OH-), have a strong tendency to bind H+, markedly raising pH
* **Weak bases**, such as the bicarbonate ion (HCO3), bind less of the available H+ and have less effect on pH
98
What is ph and what is ph inversely related to?
* pH = the negative logarithm of [H+] in moles/liter pH = -log [H+]
* pH is inversely related to hydrogen ion concentration.
99
Note survival range: 6.8-8
100
What does blood ph below 6.8 cause? What about pH above 8?
101
* Acids are continuously produced in the body and threaten what?
* Physiologically, acids fall into two groups, what are they?
* The distinction between these groups arises because why?
* noncarbonic acids in the body are not directly affected by what/
* [Acids are **continuously produced** in the body and threaten the normal pH range of the ECF and ICF.
* Physiologically, acids fall into **two groups**: (1) H2CO3 (carbonic acid) and (2) all other acids (noncarbonic; also called “nonvolatile” or “fixed” acids).
* The distinction between these groups arises because H2CO3 is in equilibrium with the volatile gas CO2, which can leave the body via the lungs. The concentration of H2CO3 in arterial blood is, therefore, affected by **respiratory activity**.
* By contrast, noncarbonic acids in the body are not directly affected by breathing. Noncarbonic acids are buffered in the body and are then **excreted by the kidneys.**
102
Cellular oxidation provides a constant source of what?
carbon dioxide (carbonic acid).
103
* Nonvolatile acids originate from incomplete metabolism of what?
* When does this happen?
Nonvolatile acids originate from incomplete metabolism of carbohydrates and fats.
* Incomplete oxidation of carbohydrates occurs when the tissues do not receive enough oxygen, as during strenuous exercise or hemorrhagic or cardiogenic shock. In such states, glucose metabolism yields lactic acid.
* Incomplete fatty acid oxidation occurs in uncontrolled diabetes mellitus, starvation, and alcoholism and produces ketone body acids (acetoacetic and β-hydroxybutyric acids). These acids have pKa values around 4 to 5. At blood pH, they mostly dissociate into their anions and H+, making the blood more acidic
104
* What is a buffer?
* What is the first line defense and second line defense against pH shift?
105
Explain teh intergration of the body's buffering system (picture)
106
107
Explain the difference in closed and open system response of bicarb-CO2 system (picture)
108
The bicarbonate buffer system is the basis for what?
for the strong buffering capacity of the respiratory system
* Neutralizes 2-3 times as much acid as the chemical buffers can
109
CO" is constantly produced by aerobic metabolism (normally eliminated by the lungs at an equivalent rate): (2)
110
Increased CO" and decreased pH stimulates what? What about increased pH?
Increased CO" and decreased pH stimulate pulmonary ventilation, while an increased pH inhibits pulmonary ventilation
111
Kidneys play a crucial role in maintaining what? How?
* Kidneys play a crucial role in maintaining the body’s acid–base homeostasis.
* Kidneys excrete excess acid to maintain acid–base balance
112
What does alpha and beta intercalated cells do?
1. an acid-secreting α-intercalated cell
2. a bicarbonate-secreting β-intercalated cell.
113
Kidneys regulate blood pH by reabsorbing filtered what? How?
* reabsorbing filtered bicarbonate
* Filtered HCO3− combines with secreted H+ and is reabsorbed indirectly. Carbonic anhydrase (CA) is present in the cells and, in the proximal tubule, on the brush border.
114
How does HPO4 play a role in acid base regulation? Ammonia?
115
* A loss of H+ in the urine is equivalent what?
* How is H+ is lost from the body? What does this lead to?
* A loss of HCO3− from the body is equivalent to what?
* A loss of H+ in the urine is equivalent to adding new HCO3− to the blood.
* The same is true if H+ is lost from the body via another route such as by vomiting of acidic gastric juice. This process leads to a rise in plasma HCO3−.
* Conversely, a loss of HCO3− from the body is equivalent to adding H+ to the blood.
116
Ammonium ions are formed from and secreted into what?
H+ from H2CO3 is consumed when ?
Ammonium ions are formed from glutamine in the cell and are secreted into the tubular urine (top). H+ from H2CO3 (bottom) is consumed when α-ketoglutarate is converted into glucose or CO2 and H2O.
117
Cellular pH is maintained by extruding what?
Hydrogen ions
118
* Body cells usually maintain a constant what?
* The cell is acidified by the production of what?
* To maintain a stable intracellular pH, the cell must do what?
* Many cells also possess various what?
* Body cells usually maintain a **constant intracellular pH**.
* The cell is acidified by the production of H+ from metabolism and the influx of H+ from the extracellular fluid (favored by the inside negative cell membrane potential).
* To maintain a stable intracellular pH, the cell must **extrude hydrogen ions at a rate matching their input.**
* Many cells also possess various **HCO3− transporters** (one example is shown) that defend against excess acid or base.
119
What are the four physiologic disturbances of acid base balance can we have?
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123
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* As with respiratory acidosis, during respiratory alkalosis, most of the buffering occurs where?
* Cell proteins and organic phosphates liberate what? What does this cause?
* When cellular mechanisms are overwhelmed what happens?
* As with respiratory acidosis, during respiratory alkalosis, most of the buffering occurs within cells.
* Cell proteins and organic phosphates liberate hydrogen ions, which are added to the ECF and lower the plasma HCO3− concentration, thereby reducing the alkaline shift in pH.
* When cellular mechanisms are overwhelmed, respiratory and renal mechanism come into play.
125
# Lungs and kidneys compensate for respiratory acidosis and alkalosis.
* An initial rise in arterial PCO2 leads to what? What compenstates this?
* In additio, the kidneys will do what?
* The kidneys compensate for respiratory alkalosis by what? A reduced PCO2 reduces what?
* An initial rise in arterial PCO2 leads to acidosis and a fall in pH. The lungs then compensate for the elevated arterial PCO2 by increasing breathing thereby diminishing the severity of the acidosis.
* In addition, the kidneys compensate for respiratory acidosis by adding more H+ to the urine and adding new HCO3− to the blood. This compensation takes several days to develop fully.
* The kidneys compensate for respiratory alkalosis by excreting HCO3− in the urine. A reduced PCO2 reduces H+ secretion by the kidney tubule epithelium.
126
127
What is metabolic acidosis?
Metabolic acidosis is a condition in which tissue and blood pH is abnormally low due to an increase in nonvolatile acids.
128
* Metabolic acidosis is buffered by what?
* In metabolic acidosis, roughly half the buffering occurs in what?
* What is the principal buffer in ECF?
* The acidic blood pH stimulates the respiratory system to do what? What does this cause?
* The kidneys respond to metabolic acidosis, as well, by doing what?
129
* Metabolic alkalosis is buffered primarily by what?
* Chemical buffers in the body limit the alkaline shift in blood pH by what? What does this result in?
* Respiratory compensation for metabolic alkalosis is limited because why?
* The kidneys respond to metabolic alkalosis by doing what? What does this cause?
130
Plasma anion gap is used to determine the etiology of what?
Metabolic acidosis
* The anion gap is a useful concept, especially when trying to determine the possible cause of metabolic acidosis. Plasma anion gap is calculated from sodium, chloride, and bicarbonate concentrations. In any body fluid, the sum of the cations and the sum of the anions are equal because solutions are electrically neutral.
131
When is the anion gap normal with and without potassium?
132
What is uncompenstated, partially compensated and fully compensated mean?
* **Uncompensated**: The body has not made any changes to counteract the pH disturbance
* **Partially compensated:** The body has made changes to counteract the pH disturbance, but the disturbance is still not corrected.
* **Fully compensated**: The body has made changes to counteract and correct the pH disturbance.
