Nephrology Flashcards
(291 cards)
1
Q
How can solute exchange occur?
A
1) Passive exchange
2) Bulk flow
2
Q
What is passive exchange?
A
Exchange of glucose, O2, and CO2 between interstitial fluid and plasma membranes of cells
3
Q
What is bulk flow?
A
Movement of water and a number of solutes across the capillary wall via pores
4
Q
What does bulk flow determine?
A
The distribution of ECF volume between vasculature and IF compartments
5
Q
What are the main components of the body fluid?
A
ICF and ECF (plasma and IF)
6
Q
What percent of body fluid does ICF make up?
A
67%
7
Q
What percent of body fluid does ECF make up?
A
33%
8
Q
What percent of ECF is made up of plasma?
A
20%
9
Q
What percent of ECF is made up of IF?
A
80%
10
Q
What is interstitial fluid?
A
An intermediary between the fluids in capillaries and the fluids within the cells of the tissues
11
Q
True or false: H2O and all plasma constituents are actively exchanged across the capillary wall
A
False, H2O and all plasma constituents are continuously and freely exchanged passively
12
Q
True or false: plasma and IF are nearly identical in composition
A
True
13
Q
What is different between IF and plasma?
A
Plasma contains plasma proteins while IF does not
14
Q
What happens if a change occurs in plasma and why?
A
A change in IF will also occur because they are constantly mixing
15
Q
True or false: ICF and ECF are nearly identical in composition
A
False, their compositions differ greatly due to the highly selective plasma membrane
16
Q
What statement can be made about any control mechanism that operates on plasma?
A
It in effect regulates the entire ECF
17
Q
True or false: ICF is influenced by changes in the ECF
A
True
18
Q
To what extent is ICF influenced by changes in ECF?
A
To the extent permitted by the permeability of membrane barriers surrounding the cells
19
Q
Why must ECF volume be regulated?
A
To maintain blood pressure
20
Q
Why must ECF solute concentration be regulated?
A
To prevent swelling or shrinking of cells
21
Q
What are negligible compartments of body fluid?
A
Lymph and transcellular fluids
22
Q
What are transcellular fluids?
A
Fluid that is secreted by specific cells into a particular body cavity to perform a specialized function
23
Q
What are 4 examples of transcellular fluids?
A
1) CSF
2) Synovial fluid
3) Serous fluids (peritoneal, pericardial)
4) Digestive juices
24
Q
True or false: transcellular fluids reflect changes in the body’s fluid balance
A
False, they do not reflect changes in the body’s fluid balance
25
When would transcellular fluids reflect fluid imbalances?
Under pathological conditions
26
What occurs in glaucoma?
Too much intraocular fluid pressure that pushes against the inner neural layer of the retina causing retina and optic nerve damage
27
How is glaucoma treated?
Any means that can decrease fluid pressure
28
What is dehydration?
Fluid loss, either loss of water or loss of water and solutes together
29
What is hypotonic hydration?
- Cellular overhydration or renal deficiency
- ECF is diluted causing low solute concentration promoting net osmosis into tissue cells
- Increased amount of fluid in all compartments
30
What can hypotonic hydration cause?
Nausea, vomiting, muscular cramping, and cerebral edema ultimately leading to death
31
How is hypotonic hydration treated?
Administration of IV hypertonic saline solution
32
What is edema?
An atypical accumulation of fluid in the IF leading to tissue (not cell) swelling
33
What does edema cause?
Increased distance that fluids must diffuse between the blood and cells
34
What can cause edema?
- Increase in ultrafiltration
- Decrease in absorption
- Decrease in lymphatic return
35
What percentage of most tissues is made up of water?
70-80%
36
What percentage of plasma does water make up?
93%
37
What percentage of fat is made up of water?
10%
38
What percentage of bone is made up of water?
22%
39
How can body composition be estimated?
1) Bioelectrical impedance analysis
2) Hydrostatic weighing
3) Magnetic resonance imaging (MRI)
4) Mirror
40
True or false: once urine is formed by the kidneys it can be altered in composition or volume
False, it cannot be altered
41
What can prostatic hypertrophy cause?
Partial or complete occlusion of the urethra
42
How do kidneys contribute to homeostasis?
1) Maintain plasma volume
2) Regulate H2O and ion concentrations
3) Acid-base balance
4) Eliminate all metabolic wastes (except CO2)
5) Endocrine
43
What is also regulated when the kidneys regulate plasma volume?
Systemic blood pressure
44
How do the kidneys regulate ion and H2O concentrations?
- Adjust for wide variations in ingestion of water, salt, and other electrolytes
- Adjust to adnormal losses through heavy sweating, vomiting, diarrhea, or hemorrhage
45
What 2 sections is the kidney divided into?
1) Renal cortex
| 2) Renal medulla
46
What is found in the renal medulla?
Renal pyramids
47
What is a nephron?
The basic functional unit of the kidney that forms urine
48
How many nephrons are found in one kidney?
More than 1 million
49
What does the nephron regulate and how?
Water and solutes by filtering the blood under pressure and then reabsorbing necessary fluid and molecules back into the blood while secreting other unneeded molecules
50
What is the main function of a nephron?
Maintain consistency in the ECF composition, which produces urine
51
What 2 basic components can a nephron be divided into?
1) Tubular component
| 2) Vascular component
52
What is a nephron composed of?
1) Renal corpuscle
| 2) Renal tubules
53
Where is the renal corpuscle found?
In the renal cortex
54
What does the renal corpuscle do?
Filters blood (first step in urine formation)
55
What type of fluid does the renal corpuscle filter?
Fluid that is almost identical in composition to plasma
56
What is the renal corpuscle composed of?
1) Glomerulus
2) Bowman's capsule
3) Filtration membrane
57
What is the glomerulus?
A capillary bed
58
Where is the Bowman's capsule found?
Surrounding the glomerulus
59
What does the Bowman's capsule do?
Collects filtrate from the glomerulus
60
What are the 2 layers of the Bowman's capsule?
1) Outer layer
| 2) Inner layer
61
What is found in the inner layer of the Bowman's capsule?
Podocytes wrapped around the glomerular capillaries
62
What does the filtration membrane consist of?
1) Glomerular endothelium
2) Basement membranes
3) Podocytes (of Bowman's capsule)
63
What type of cells are found in the glomerular endothelium?
Simple squamous with pores (fenestrations)
64
What are podocytes?
Projections that "cling" to the glomerulus
65
What are the 4 parts of a renal tubule?
1) Proximal convoluted tubule
2) Loop of Henle
3) Distal convoluted tubule
4) Collecting ducts
66
Where is the proximal convoluted tubule found?
Renal cortex
67
Where is the Loop of Henle found?
Renal medulla
68
Where is the distal convoluted tubule found?
Renal cortex
69
Where are collecting ducts found?
Renal cortex and renal medulla
70
How many nephrons drain into one collecting duct?
About 8
71
What do collecting ducts do?
Drain to the renal pelvis
72
What are the 2 types of nephrons?
1) Cortical (80%)
| 2) Juxtamedullary (20%)
73
Describe cortical nephrons
- Renal corpuscle near kidney surface in cortex
| - Short loop of Henle in outer medulla
74
Describe juxtamedullar nephrons
- Renal corpuscle in cortex near medulla
| - Long loop of Henle that penetrates deep into medulla
75
With respect to the renal blood supply, what does the aorta branch into?
Renal arteries
76
With respect to the renal blood supply, what do the renal arteries branch into?
Segmental arteries
77
With respect to the renal blood supply, what do the segmental arteries branch into?
Interlobar arteries
78
With respect to the renal blood supply, what do the interlobar arteries branch into?
Arcuate arteries
79
What is significant about the arcuate arteries?
Medulla-cortex junction
80
With respect to the renal blood supply, what do the arcuate arteries branch into?
Cortical radiate arteries
81
With respect to the renal blood supply, what do the cortical radiate arteries branch into?
Afferent arterioles
82
With respect to the renal blood supply, what do the afferent arterioles feed into?
Glomeruli
83
With respect to the renal blood supply, what exits the glomeruli?
Efferent arterioles
84
What is significant about the efferent arterioles of the glomeruli?
They are the only arterioles that drain from capillaries
85
With respect to the renal blood supply, what do the efferent arterioles branch into?
Peritubular capillaries and vasa recta
86
What are peritubular capillaries?
Cortical nephrons in renal cortex
87
What are vasa recta?
Juxtaglomerular nephrons in the renal medulla
88
With respect to the renal blood supply, what do the peritubular capillaries and vasa recta form when they join?
Cortical radiate veins
89
With respect to the renal blood supply, what do the cortical radiate veins become?
Arcuate veins
90
With respect to the renal blood supply, what do the arcuate veins become?
Interlobar veins
91
With respect to the renal blood supply, what do the interlobar veins become?
Renal veins
92
With respect to the renal blood supply, what do the renal veins become?
Inferior vena cava
93
What is the function of the juxtaglomerular complex?
Regulates filtrate formation
94
What does the ascending limb of the juxtaglomerular complex pass through?
The fork formed by the 2 afferent and efferent arterioles
95
What is special about the juxtaglomerular complex?
Is the point of contact between the end of the ascending limb and the afferent and efferent arterioles at the renal corpuscle of the same nephron
96
What are the 2 portions of the juxtaglomerular complex?
1) Tubular portion
| 2) Vascular portion
97
What does the tubular portion of the juxtaglomerular complex contain?
Macula densa, which are modified (tall and narrow) ascending limb cells
98
What does the vascular portion of the juxtaglomerular complex contain?
Granular juxtaglomerular cells, which are the afferent and efferent arteriolar portion
99
What is the function of granular juxtaglomerular cells?
- Monitor BP
| - Contain renin
100
At rest, what percent of cardiac output is going to the kidneys?
About 20%
101
What 3 basic processes occur in the nephron to form urine?
1) Glomerular filtration
2) Tubular reabsorption
3) Tubular secretion
102
Where does glomerular filtration occur?
Glomerular capillaries
103
What percent of plasma in glomerulus is filtered into the Bowman's capsule?
20%
104
How is plasma in the glomerules filtered into the Bowman's capsule?
Bulk flow (pressure gradient) across the filtration membrane
105
How much filtrate is collectively formed per minute?
125 mL
106
How many times is the entire plasma volume filtered per day?
About 65 times per day
107
What is filtrate?
Plasma minus large proteins
108
What makes up filtrate?
Water, glucose, amino acids, vitamins, ions, urea, and small amounts of small proteins
109
What is the pH of filtrate?
About 7.45
110
What is albuminuria
- When the filtration membrane allows excessive albumin into the urine
- Occurs in some renal disease
111
What are the 4 types of pressure that occur in glomerular filtration?
1) Glomerular hydrostatic pressure
2) Plasma-colloid osmotic pressure
3) Capsular hydrostatic pressure
4) Capsular osmotic pressure
112
What is the normal value of glomerular hydrostatic pressure and does it favour or oppose filtration?
- 55 mmHg
| - Favoured
113
What is the normal value of plasma-colloid osmotic pressure and does it favour or oppose filtration?
- 30 mmHg
| - Opposed
114
What is the normal value of capsular hydrostatic pressure and does it favour or oppose filtration?
- 15 mmHg
| - Opposed
115
What is the normal value of capsular osmotic pressure and does it favour or oppose filtration?
- 0 mmHg
| - Favoured
116
What is value of net filtration pressure?
(55 + 0) - (30 + 15) = 10 mmHg
117
What is the normal glomerular filtration rate?
About 180 L/day of filtrate
118
What happens to about 1% of filtered volume?
It remains at the end of collecting duct
119
Why must GFR be regulated?
To keep GFR from changing when MAP changes
120
How is GFR regulated?
1) Autoregulation (intrinsic regulation), which is aimed at preventing spontaneous changes in GFR
2) Extrinsic symp. control, which is aimed at long-term regulation of MAP
121
How do both control mechanisms work to regulate GFR?
Adjust glomerular blood flow by regulating the radius and thus the resistance of the afferent arteriole
122
How does autoregulation work to regulate GFR?
1) Myogenic mechanism
| 2) Juxtaglomerular apparatus
123
Describe the myogenic mechanism of GFR regulation
- Increased MAP = stretch = afferent arteriole smooth muscle contracts = prevents increased BP in glomerular caps = GFR stays normal
- Vice versa
124
Describe the juxtaglomerular apparatus of GFR regulation
- Changes in GFR = changes in flow of flitrate past macula dense cells that detect changes in salt levels of fluid flowing past them
- Increased GFR = more fluid is filtered = more salt delivery to macula densa cells = release ATP = extracellular degradation forms adenosine = afferentarteriole v/c = increased GFR to normal
- Decreased salt delivery to macula densa cells = decreased release of ATP = decreased extracellular adenosine = afferent arteriole v/d = increased GFR to normal
125
True or false: intrinsic/autoregulation overrides extrinsic regulation of GFR
False, extrinsic overrides intrinsic regulation of GFR
126
What can extrinsic regulation do to GFR?
Can change it on purpose even when MAP is within the autoregulatory range
127
What mediates extrinsic control of GFR?
The sympathetic nervous system
128
How does extrinsic control regulate GFR?
- SNS causes arteriole v/c
- Afferent causes decreased flow into glomerules; efferent causes blood to back up in glomerulus
- Moderate SNS activation causes both to balance and GFR not to change dramatically
129
What can extreme stress do to GFR?
Can decrease it
130
What can cause changes to plasma-colloid osmotic pressure (PCOP)?
1) Dehydration causes increased PCOP, which causes decreased GFR
2) Severe burns causes decreased PCOP, which causes increased GFR
131
What can cause a change in capsular hydrostatic pressure (CHP)?
Urinary tract obstruction (ex: kidney stones, enlarged prostate) causes increased CHP, which causes decreased GFR
132
What percent of filtrate is reabsorbed?
99%
133
Where is filtrate reabsorbed from and where to?
- From tubules
| - Into peritubular and vasa recta capillaries
134
True or false: all consituents are at the same concentration in the glomerular filtrate and in the plasma
False, plasma proteins are at different concentrations in filtrate and plasma
135
What are the 2 steps of reabsorption?
1) Active or passive transport from tubule fluid to renal IF
| 2) Active or passive transport from IF to blood
136
How many barriers must a reabsorbed substance cross?
5
137
When will absorption be considered active?
If any one of the steps in transepithelial transport of a substance requires energy
138
What is an example of active reabsorption?
An active Na/K pump in the basolateral membrane is essential for Na reabsorption
139
What percent of total energy spent by the kidneys is used for Na transport?
80%
140
What substances generally require active reabsorption?
Na, other ions, glucose, and amino acids
141
What substance generally require passive reabsorption?
Cl, water, and urea
142
What is the primary role of the proximal convoluted tubule in the process of reabsorption?
Fluid and electrolyte transport
143
What percent of glucose and amino acids are reabsorbed by sodium?
100%
144
How does sodium reabsorb glucose and amino acids?
Dependent, secondary active transport
145
What percent of sodium is reabsorbed by active transport?
67%
146
What is the final result of the proximal convoluted tubule in the process of reabsorption?
- Large amount of solute is removed and filtrate volume is decreased
- Filtrate is isotonic to plasma
147
What is the primary role of the loop of Henle in the process of reabsorption?
Reabsorbs into vasa recta
148
What is reabsorbed in the descending limb of the loop of Henle?
Water only
149
What is reabsorbed in the ascending limb of the loop of Henle?
25% NaCl only
150
What is reabsorbed in the distal convoluted tubule and collecting duct and what does this cause?
- 8% Na; causes increased aldosterone and decreased atrial natriuretic peptide (ANP)
- Facultative reabsorption of water; causes increased ADH
151
What 4 things do nephrons normally absorb?
- 99% of filtered water
- 99.5% of filtered NaCl
- 100% of filtered glucose
- 50% of filtered urea
152
What may be found in filtrate?
Trace amounts of amino acids and proteins (depending on diet)
153
What should never be found in filtrate?
Glucose or blood
154
Where does tubular secretion occur?
From peritubular blood into filtrate
155
What are the main substances that are secreted in tubular secretion?
- Wastes such as urea, uric acid, and some hormones
- Potassium
- H+ which helps maintain blood plasma pH
156
What does the countercurrent multiplier mechanism permit?
Excretion of urine that is dilute or concentrated (100 - 1200 mOsm/L)
157
What does the countercurrent multiplier mechanism produce?
A vertical osmotic gradient (solute concentration increases in ISF as you move deeper into the medulla)
158
What produces the vertical osmotic gradient?
Juxtamedullary nephrons
159
What 3 things occur within the loop of Henle with respect to the countercurrent multiplier mechanism?
1) Filtrate moves down descending limb and water moves into ISF by osmosis
2) Highly concentrated filtrate enters ascending limb
3) Filtrate leaving ascending limb is lower in osmolarity than plasma
160
How is NaCl pumped out of the ascending limb of the loop of Henle?
Against the concentration gradient
161
What is the descending limb of the loop of Henle permeable and impermeable to?
- Permeable to water
| - Impermeable to NaCl
162
What is the ascending limb of the loop of Henle permeable and impermeable to?
- Permeable to NaCl
| - Impermeable to water
163
What is filtrate in the ascending limb lower in osmolarity than plasma?
- Ascending limb is impermeable to water
| - Ascending limb NaCl pump
164
What occurs within the early distal convoluted tubule with respect to the countercurrent multiplier mechanism?
- More salt is removed from filtrate (reabsorbed)
| - No water removed, therefore 100 mOsm/L when enters late DCT
165
Concentrated urine means a ______ blood pressure
Low
166
What happens in the distal convoluted tubule and collecting duct to make urine concentrated?
- Aldosterone increases Na reabsorption
| - ADH increases facultative water reabsorption
167
What is the highest concentration that urine can be?
1200 mOsm/L
168
Dilute urine means a ______ blood pressure
High
169
What happens in the distal convoluted tubule and collecting duct to make urine dilute?
ANP inhibits ADH and aldosterone, making it impermeable to water and NaCl
170
What is the average amount of urine produced per day?
1 - 1.5 L
171
What are 2 regulators of urine?
1) Hormonal
| 2) SNS
172
What 4 hormonal controls regulate urine concentration?
1) Renin-angiotensin system
2) ADH
3) Aldosterone
4) ANP
173
How does the renin-angiotensin system regulate urine concentration?
Granular cells of the juxtaglomerular apparatus secrete renin
174
What causes juxtaglomerular cells to secrete renin?
- Decreased blood pressure or ECF volume
- Decreased NaCl in filtrate
- Increased SNS activity
175
Granular cells act as _______
Intrarenal baroreceptors
176
How is decreased NaCl in filtrate detected?
At the macula densa which trigger the granular cells
177
Granular cells are innervated by the ______ NS
Sympathetic
178
What are 4 general causes of increased angiotensin 2?
1) Increased NaCl reabsorption and K secretion
2) Increased systemic BP (MAP)
3) Decreased GFR
4) Increased facultative water reabsorption
179
What does ADH cause?
Increased facultative reabsorption of water in the DCT and collecting ducts
180
What percent of water reabsorption is obligatory in the proximal convoluted tubule?
65%
181
What percent of water reabsorption is obligatory in the distal convoluted tubule and collecting duct?
It is variable based on the secretion of ADH
182
What does ADH secretion do to tubule cells?
Increases the permeability of tubule cells to water
183
Where does an osmotic gradient exist and why?
Outside the tubules from the transport of water by osmosis
184
What 4 things cause ADH to increase?
1) Low blood pressure/volume
2) Increased plasma osmolarity
3) Increased angiotensin 2
4) Nicotine or nausea
185
What 5 things cause ADH to decrease?
1) High blood pressure/volume
2) Decreased plasma osmolarity
3) Decreased angiotensin 2
4) Increased ANP
5) Alcohol and caffeine
186
When does aldosterone increase?
When angiotensin 2 increases and plasma K is high
187
What does aldosterone do with respect to genes?
Turn on genes that increase the number of Na/K ATPase in DCT and CD, which causes increased Na reabsorption and K secretion
188
What is caused by Na reabsorption in late DCT and CD?
Water follows and Cl follows
189
What is the net result of aldosterone on regulation of urine concentration?
Greater passive inward flux of Na into the tubular cells from the lumen and increased active pumping of Na out of the cells into the plasma (Increased Na reabsorption with Cl following)
190
What happens to nephrons in the absence of aldosterone?
Nephrons can rapidly remove excess Na from the body
191
How much Na can be lost with complete absence of aldosterone?
20 grams per day
192
How much Na can be lost with maximum secretion of aldosterone?
0 grams because all filtered Na will be reabsorbed
193
What 2 mechanisms can cause aldosterone secretion?
1) Increased plasma K
| 2) Decreased Na, ECF volume, or arterial pressure
194
What causes ANP to be secreted?
- Increased blood pressure
- Hypervolemia (too much fluid in the blood),
- Exercise
195
What does ANP cause?
- Inhibition of Na reabsorption, thus increasing Na excretion
- Inhibition of renin, angiotensin 2 and aldosterone
- Increased GFR by v/d of afferent arteriole
- Decreased CO by inhibiting symp nervous activity to heart and blood vessels
196
What can exacerbate a failing heart and why?
- Increased salt and water reabsorption
| - Failing heart means CO is reduced and MAP is low, which means angiotensin 2 is increased
197
What do diuretics do?
Inhibit tubular reabsorption of Na, increasing water loss and reducing excess EFC
198
What else besides diuretics can inhibit salt and fluid reabsorption?
- ACE inhibitors
| - Aldosterone receptor blockers
199
What does increased sympathetic NS impulse cause with respect to regulation of urine concentration?
Afferent and efferent arterioles constrict
200
What does decreased sympathetic NS impulse cause with respect to regulation of urine concentration?
Afferent and efferent arterioles relax
201
What happens when MAP increases with respect to regulation of urine concentration?
Flow to kidney increases causing v/c in spite of decreased SNS, renin, and angiotensin 2 and increased ANP, meaning GFR returns to resting
202
What does a lack of ADH and aldosterone mean for urine?
It will be dilute, so blood volume will decrease and MAP will decrease
203
What happens if there is a large decrease in blood pressure or volume?
V/c signals get stronger than intrinsic mechanisms, so GFR decreases
204
What are the normal constituents of urine?
- Water
- Nitrogenous wastes
- Regulated substances (ex: ions)
205
What type of nitrogenous wastes are found in urine?
- Urea
- Uric acid
- Creatinine
206
How is urea produced?
From amino acid metabolism
207
What percent of urea is reabsorbed?
About 50%
208
How is uric acid produced?
From nucleic acid breakdown
209
What percent of uric acid is reabsorbed?
About 10%
210
What is gout?
When uric acid accumulates between joints because it is poorly water soluble
211
What are kidney stones made of?
Crystallized uric acid
212
How is creatinine produced?
From breakdown of creatine in skeletal muscle
213
What percent of creatinine is reabsorbed?
None because production and excretion is constant
214
What are creatinine levels used to estimate?
GFR, which can indicate kidney disease before symptoms occur
215
What is the normal pH range of urine?
4.5 - 8
216
What are 3 abnormal constituents of urine?
1) Proteins
| 2) Glucose
217
What is another name for proteinuria?
Albuminuria
218
What causes albuminuria?
Increased permeability of glomerules due to heavy metals or glomerulonephritis
219
What is glycosuria?
When glucose is present in urine
220
What are 5 causes of renal failure?
1) Infectious organisms
2) Toxic agents
3) Inappropriate immune responses
4) Obstruction of urine flow
5) Insufficient renal blood supply
221
What is urinary incontinence?
Inability to prevent discharge of urine
222
What is renal plasma clearance?
The volume of plasma cleared of a substance in one minute
223
What is renal plasma clearance used for?
To estimate the time a substance remains in blood
224
What substance can be used to estimate GFR and why?
- Inulin
| - Is filtered but not reabsorbed, secreted, or metabolized, therefore the amount in urine = amount filtered
225
What does it mean if plasma clearance is less than GFR of a substance and what are 2 examples of this?
- The substance is reabsorbed from filtrate
| - Ex: urea and glucose
226
What does it mean if plasma clearance is greater than GFR of a substance and what are 2 examples of this?
- Substance is secreted into filtrate
| - Ex: penicillin and H+
227
What does acid-base balance refer to?
Precise regulation of free H+ concentration in body fluids
228
What are acids?
A group of H+ containing substances that dissociate in solution to release free H+ and anions
229
What are bases?
A group of substances that combine with free H+ and remove it from solution
230
Where does most H+ in the body come from?
Metabolic activities
231
What is acidosis?
When the body pH is between 6.8 - 7.35
232
What is alkalosis?
When the body pH is between 7.45 - 8
233
What are 3 sources of H+ in the body?
1) Carbonic acid formation
2) Inorganic acids produced during breakdown of nutrients
3) Organic acids resulting from intermediary metabolism
234
How is carbonic acid formed?
CO2 + H2O
235
What is an example of an inorganic acid that is produced during breakdown of nutrients?
Sulphuric and phosphoric acids are produced when sulphur and phosphorus from dietary proteins are broken down
236
What are 3 examples of organic acids resulting from intermediary metabolism?
1) Fatty acids
2) Amino acids
3) Lactic acid
237
What are 3 consequences of H+ fluctuations in the body?
1) Changes in excitability of nerve and muscle cells
2) Marked influence on enzyme activity
3) Influence on K+ levels in body
238
What does acidosis cause to the CNS?
Depression of CNS
239
What does alkalosis cause to the PNS?
Overexcitability to PNS and later to the CNS
240
Why do H+ fluctuations have an influence on enzyme activity?
Enzymes have a narrow range of temperature and pH where their activity can be maximal, and H+ is a factor in the enzyme staying within these ranges
241
Why do H+ fluctuations have an influence on K+ levels in the body?
- When reabsorbing Na from filtrate, tubular cells secrete either K+ or H+ in exchange
- An increased rate of one decreases the rate of the other
242
What are the 3 lines of defense against changes in H+ concentration?
1) Chemical buffer systems
2) Respiratory mechanism of pH control
3) Renal mechanism of pH control
243
How do chemical buffer system prevent changes in H+ concentration?
- Minimize changes in pH by binding with or yielding free H+
| - Act within fractions of a second
244
True or false: chemical buffer systems eliminate H+ from the body
False, they are removed from solution by being incorporated within one member of the buffer pair
245
What is the first line of defense for acid-base balance?
Chemical buffer systems
246
What are the 4 buffer systems of the body?
1) Carbonic acid/bicarbonate
2) Protein buffer system
3) Hemoglobin buffer system
4) Phosphate buffer system
247
How do carbonic acid and bicarbonate work as a buffer system?
Carbonic acid and bicarbonate are abundant in the ECF with the kidneys regulating bicarbonate and CO2 in the lungs (generating carbonic acid)
248
What is unique about the carbonic acid/bicarbonate buffer system?
Is the primary ECF buffer for noncarbonic acids
249
What is the most plentiful buffer system in the body?
Protein buffer system
250
What is the primary ICF buffer?
Protein buffer system
251
True or false: protein buffer systems contain body acidic and basic groups
True
252
What is unique about the hemoglobin buffer system?
Primary buffer against carbonic acid changes
253
What is unique about the phosphate buffer system?
Can switch Na for H+
254
The phosphate buffer system has a low concentration in ______
ECF
255
What is the most important urinary buffer and why?
- Phosphate buffer system
- There is normally excess phosphate in diet, so it remains in tubular fluid to be excreted and buffers urine as it is being formed by removing H+
256
True or false: there are no buffer systems present in tubular fluid
True
257
True or false: little to none bicarbonate and CO2 are reabsorbed
False, most or all of the filtered bicarbonate and CO2 are reabsorbed
258
Why must H+ be removed from the body if buffer systems exist?
Because each buffer system has a limited capacity to soak up H+
259
What would happen if H+ was never removed from the body?
All the body-fluid buffers would already be bound with H+ and there would be no further buffering ability
260
What is the second line of defense in acid-base balance?
Respiratory system
261
How does the respiratory system work to balance acids and bases?
Removes CO2, therefore also removing H+
262
What will the respiratory system do when H+ is too high?
Hyperventilate
263
What will the respiratory system do when H+ is too low?
Hypoventilate
264
What is the third line of defense in acid-base balance?
Renal system
265
How does the renal system work to balance acids and bases?
Eliminates H+ from metabolically produced acids by secreting H+ into tubule
266
How does the majority of H+ enter urine?
Via tubular secretion
267
What parts of the nephron secrete H+?
Proximal convoluted tubule, distal convoluted tubule, and collecting tubules
268
When does the respiratory system begin to work with respect to acid-base balance?
Minutes
269
When does the renal system begin to work with respect to acid-base balance?
Hours to days
270
What can H+ energy-dependent carriers in tubular cells do?
Can secrete H+ against a concentration gradient until the tubular fluid is 800 times as acidic as the plasma
271
What is needed for H+ secretion to continue?
It must be buffered in the tubular fluid
272
What happens to make bicarbonate be considered "reabsorbed"?
One filtered bicarbonate disappears from the tubular fluid (through combination with H+), and one bicarbonate appears in the plasma (through combination of OH and CO2)
273
What occurs once all filtered bicarbonate has combined with secreted H+?
- Further secreted H+ is excreted in the urine, primarily in association with urinary buffers
- This is coupled with the appearance of new bicarbonate in plasma, which represent a new gain as opposed to a replacement of filtered bicarbonate
274
What happens once phosphate ions have soaked up H+?
The tubular cells secrete ammonia
275
What happens once ammonia is in the tubule?
It binds with H+ to form ammonium
276
True or false: ammonium is not very permeable so it remains in tubular fluid
True
277
What synthesizes ammonia?
The amino acid glutamate within tubular cells
278
What can cause acid-base inbalances?
Respiratory dysfunction of metabolic disturbances
279
What are the 4 general categories of acid-base imbalances?
1) Respiratory acidosis
2) Respiratory alkalosis
3) Metabolic acidosis
4) Metabolic alkalosis
280
What is respiratory acidosis?
Abnormal CO2 retention arising from hypoventilation
281
What are 4 possible causes of respiratory acidosis?
1) Lung disease
2) Depression of respiratory centre by drugs or disease
3) Nerve/muscle disorders that reduce respiratory muscle activity
4) Holding breath
282
What are 2 compensations to counteract respiratory acidosis?
1) Chemical buffers immediately take up additional H+
| 2) Kidneys
283
What is respiratory alkalosis?
Excessive loss of CO2 from body as a result of hyperventilation
284
What are 4 possible causes of respiratory alkalosis?
1) Fever
2) Anxiety
3) Aspirin poisoing (hyperstimulation of the respiratory centre)
4) Physiologic mechanisms at high altitude
285
What are 2 compensations to counteract respiratory alkalosis?
1) Chemical buffer systems liberate H+
| 2) Kidneys conserve H+ and excrete more bicarbonate
286
What is metabolic acidosis?
- Fall in bicarbonate concentration
| - Includes all types of acidosis other than those caused by excess CO2 in body fluids
287
What are 4 possible causes of metabolic acidosis?
1) Severe diarrhea
2) Diabetes (ketoacidosis from fatty acid breakdown)
3) Strenuous exercise
4) Uremic acidosis (renal failure)
288
What are 3 compensations to counteract metabolic acidosis?
1) Buffers take up extra H+
2) Lungs blow off additional H+ generating CO2
3) Kidneys excrete more H+ and conserve more bicarbonate
289
What is metabolic alkalosis?
- Elevation in bicarbonate concentration
| - Reduction in plasma pH caused by relative deficiency of noncarbonic acid
290
What are 2 possible causes of metabolic alkalosis?
1) Vomiting -- loss of acidic gastric juices
| 2) Ingestion of alkaline drugs -- extra is absorbed in the digestive system into blood plasma
291
What are 3 compensations to counteract metabolic alkalosis?
1) Chemical buffer systems immediately liberate H+
2) Ventilation is reduced
3) Kidneys conserve H+ and excrete excess bicarbonate in the urine
