Renal Physiology Flashcards
1
Q
What is osmolarity?
A
Concentration of osmoticaly active particles present in a solution
2
Q
Equation for osmolarty
A
Osmolarity = (molar conc) x (no. of osmotically active particles)
3
Q
What is tonicity?
A
The effect a solution has on cell volume
4
Q
What is used to measure body fluid compartments?
A
Tracers
5
Q
What is osmotic concentration of both ECF and ICF?
A
300 mosmol/l
6
Q
What is fluid shift?
A
Movement of water between the ICF and ECF in response to an osmotic gradient
7
Q
What alters the composition & volume of ECF?
A
The kidneys
8
Q
Where is Na+ mainly present ECF or ICF?
A
ECF
9
Q
What percentage of the body’s potassium is intracellular?
A
95%`
10
Q
How does salt imbalance manifest?
A
Changes in ECF volume
11
Q
What are the 3 functional mechanisms of the kidney?
A
Filtration
Reabsorption
Secretion
12
Q
Which is more superior efferent arteriole or afferent arteriole?
A
Efferent
13
Q
What are 2 different types of nephron?
A
Juxtamedullary (20%)
Cortical (80%)
14
Q
What makes up the inner layer of the Bowman’s capsule?
A
Podocytes
15
Q
What is urine?
A
Modified filtrate of the blood
16
Q
What is the function of macula densa cells?
A
Sense distal tubules flow and releae paracrines to alter afferent arteriole diameter
17
Q
What are the 3 filtration barriers within the glomerulus?
A
Glomerular Capillary Endothelium
Basement membrane
Slit processes of podocytes
18
Q
What forces comprise net filtration pressure?
A
Glomerular capillary blood pressure
Capillary oncotic pressure
Bowman’s capsule hydrostatic pressure
Bowmans capsule oncotic pressure
19
Q
What is GFR?
A
The rate at which protein free plasma is filtered from the glomeruli into the Bowman’s capsule per unit time
20
Q
What is a normal GFR?
A
approx. 125ml/min`
21
Q
What is the major determinant of GFR?
A
Glomerular capillary fluid (lood) pressure
22
Q
What is the extrinsic mechanism of controlling FR?
A
Sympathetic control via baroreceptor reflex
23
Q
What intrinsic mechanisms regulate GFR?
A
Tubuloglomerular feedback mechanism
Myogenic mechanism
24
Q
What affect doe increased arterial BP have on blood flow into the glomerulus?
A
Increased arterial BP increases blood flow into the glomerulus
25
What effects does increased blood flow have on the pressures within the glomerulus?
Increased glomerular capillary blood pressure
| increased net filtration pressure
26
What causes a decrease in glomerular capillary blood pressure? (physiologically)
Constriction of afferent arteriole
27
What effect does a decrease in blood flow have on GFR?
GFR decreases
28
How does a fall in blood volume result in reduced urine volume?
Fall in blood volume > decreased arterial BP > detected by aortic & carotid sinus baroreceptors > increased sympathetic activity > generalised arteriolar vasoconstriction > constriction of afferent arterioles
> decreased Glomerular BP > decreased GFR > Reduced urine volume
29
What is the myogenic mechanism?
If vascular smooth muscle is streatch (e.g. increase in arterial P) it contracts thus contricting the arteriole
30
What is tubuloglomerular feedback?
Involes JXGA
| If GFR rises, more NaCl flows through the tubules leading to constriction of afferent arterioles
31
What is plasma clearance a measure of?
Hoe effectively the kidneys can 'clean' the blood of a substance
32
What effect does decreased capillary oncotic pressure (e.g. severely burned patients) have on GFR?
Increased GFR
33
For which substance does clearance = GFR?
Inulin
34
What is more commonly used instead of inulin to measure GFR?
Creatinine
35
Example of a substance that is filtered and completely reabsrbed and therefore not secreted?
Glucose
36
What can be said about a subtance if the clearance is
Te substance is reabsorbed
37
What can be said about a substance if the clearance > GFR?
The substance is secreted into tubule
38
What is PAH used clinically to measure?
Renal plasma flow
39
What is reabsorbed in the proximal tubule?
```
Sugars
Amino acids
Phosphate
Sulphate
Lactate
```
40
What is secreted in the proximal tubules?
```
H+
Hippurates
Neurotransmitters
Bile pigments
Uric acid
Drugs toxins
```
41
What 3 mechanism allow resorption in the proximal tubules?
Primary active transport
Secondary active transport
Facilitated diffusion
42
Which transport mechanism at the basolateral membrane is essential for Na+ resorption?
Na-K-ATPase
43
What is Na co-transported with into the tubular cells fcrom the lumen?
Glucose
44
What percentage of salt & water is reabsorbed in the proximal tubule?
~67%
45
What other electrolyte reabsorption deos Na+ drive through the paracellular pathway?
Cl-
46
What tonicity is the tubular fluid as it leaves the proximal tubule?
Iso-osmotic
47
What is the function of the loop of Henle?
Generates a cortico-medullary concentration gradient
| 'countercurrent multiplier'
48
What is being reabsorbed in the ascending limb of the loop of Henle?
Na + & Cl-
49
Hoe permeable is the ascending limb to water?
Relatively impermeable
50
How permeable is the descending lim to water?
Highly permeable
51
Which 3 ions are involved in the triple co-transporter?
Na
K
Cl
52
Which drugs block the triple co-transporter?
Loop diuretics
53
Does water enter or leave the descending limb?
Leaves my osmosis
54
What is the osmolarity of fluid in the descending limb?
400 mosmol/L
55
What is the osmolarity of the fluid in the thick ascending limb?
200 mosmol/L
56
Is the fluid more concentrated in the ascending or descending limb?
Desending
57
What contribues to approx. half of the medullary osmolarity?
The urea cycle
58
What promotes urea absorption in the collecting duct?
ADH
59
Where is 50% of urea reabsorbed?
Collecting duct
60
Which part of the nephron is impermeable to urea?
Distal tubule
61
Which type of nephron has vasa recta which run alongsid ethe long loop of henle?
Juxtamedullary nephrons
62
What happens to blood osmolarity as it dips down into the medulla?
Blood osmolarity rises (water loss, solute gained)
63
What happens to blood osmolarity as it rises back up into the cortex?
Blood osmolarity falls (water gained, solute lost)
64
What are vasa recta capillaries freely permeable to?
NaCl & water (picks up water leaked out by DL)
65
What effect does ADH have on water reabsorption?
Increases water reabsorption (DT & CD become more permeable)
66
Which areas of the nephrons are affected by hormones?
Distal tubule & collecting duct (not proximal tubule & loop of Henle)
67
What affect does aldosterone have on electrolytes in the kidneys?
Increased Na reabsorption
| increased H+/K+ secretion
68
What effect does atrial natriuretic hormone have on Na+ reabsorption?
ANH decreases Na reabsorption
69
What effect does PTH have on electrolytes in the kidneys?
Increased calcium reabsorption
| Decreased phosphate reabsorption
70
What electrolytes are reabsorbed in the early distal tubule?
NaCl
71
What electrolytes are reabsorbed in the late disal tubule?
Ca2+
Na+
K+
72
What is secreted in the late distal tubule?
H+
73
What influences the collecting ducts permeability to water & urea?
ADH
74
Where in the hypothalamus is ADH synthesised?
Supraoptic & paraventricular nuclei
75
Where is ADH stored?
Posterior pituitary
76
When is ADH released?
When action potential down the nerves leads to calcium dependent exocytosis
77
What receptor does ADH bind to?
Type 2 vasopressin receptor
78
What is increased when ADH bind to vasopressin type 2 receptor?
intracellular cAMP
79
Where are aquaporins found?
Apical membrane
80
What are circulating levels of ADH dependent on?
The body's hydration status
81
Does an increase in ADH lead to more concentrated or dilutre urine?
Concentrated
82
Does ADH affect the salt or solute concentration of urine?
No
83
What are the 2 different types of diabetes insipidus?
Central diabetes insipidus
| Nephrogenic diabetes insipidus
84
What is central diabetes inspidus?
Unable to produce or secrete ADH
85
What is nephrogenic diabetes insipidus?
Produce ADH as normal but does not affect target cells
86
Symptoms of diabetes inspidus
Large volume of dilute urine
| Constant thirst
87
Treatment of central diabetes inspidus?
ADH replacement
88
Treatment of nephrogenic diabetes inspidus
Drugs to reduce urine production
89
What can diabetes insipidus be a side effect of?
Long term lithium therapy
90
Which receptors sense the need for ADH release?
Hypothalamic osmoreceptors
| Left atrial stretch receptors
91
Does alcohol inhibit or stimulate ADH release?
Inhibit
92
Does nicotine stimulate or inhibit ADH release?
Stimulates
93
Where is aldosterone secreted from?
Adrenal cortex
94
What does aldosterone do?
Stimulate Na+ reabsorption & K+ secretion
95
Where is majority of K+ normally reabsorbed?
Proximal tubule (~90%)
96
True/False? An increase in plasma K+ directly stimulates the adrenal cortex?
True
97
Does a decrease in plasma Na+ promote secretion of aldosterone directly or indirectly?
Indirectly (via juxtoglomerular apparatus)
98
Where is angiotensinogen produceed?
Liver
99
Where is renin produced?
Kidney
100
Where is ACE produced?
Lungs
101
What is the action of renin?
Convert angiotensinogen to angiotensin I
102
What is the action of ACE?
Convert angiotensin I to angiotensin II
103
What effect does angiotensin II have on the adrenal cortex?
Stimulates release of aldosterone
104
Actions of angiotensin II outside the kidneys?
Stimulates ADH release
Increases thirst
Causes arteriolar vasocontriction
105
What role do macula dense cells play in RAAS system?
Sense reduced NaCl in the distal tubules and promote renin release
106
What factors control renin release from granular cells in JXGA?
Reduced pressure in afferent arteriole
Macula densa cells
Increased sympathetic activity as a result of reduced BP
107
What condition can be caused by abnormal increases in RAAS?
Hypertension
108
How does congestive heart failure cause increased salt (& water) retention?
Failing heart > decreased CO & BP > low BP stimulates RAAS > increased salt retention
109
Where is ANP/H produced?
The heart
110
Where is ANP/H stored?
Atrial muscle cells
111
What stimulates the release of ANP/H?
When atrial muscle cells are mechanically stretched due to an increase in the circulating plasma volume
112
What are the actions of ANP/H?
Excretion of Na+ and diuresis (thus decreasing plasma volume > lower BP)
113
How does an increased in ANP/H lead to an increase in the Na + and H2O filtered?
ANP/H has a negative effect on smooth muscle of afferent arterioles > vasodilation > increased GFR > increase in Na+ and H2O filtered
114
What 2 mechanisms govern micturition?
The micturition reflex
| Voluntary control
115
Which receptors detect a full bladder?
Stretch receptors
116
What is the pH of arterial blood?
7.45
117
What is the pH of venous blood?
7.35
118
What effect does acidosis have on the CNS?
Depression of the CNS
119
Which dissociates completely strong or weak acids?
Strong acids
120
What is the Henderson-Hasselbach equation used for?
Buffers
121
What catalyses the conversion of carbon dioxide and water to carbonic acid?
Carbonic anhydrase
122
Which organs controls the bicarbonate concentration?
Kidneys
123
Which organ controls the carbon dioxide concentration?
Lungs
124
How is bicarbonate reabsorbed in the proximal tubule?
Indirectly
125
Why would the kidneys need to generate new bicarbonate?
To regenrate buffer stores depleted by an acid load
126
When bicarbonate is low what does secreted H+ bind with?
Phosphate
127
How can the amount of H+ excreted be measured?
As "titratable" acid
128
How is ammonia made?
Glutamine breakdown by glutaminase
129
Why gas ammonia diffuse across the apical membrane?
Because it is a gas
130
What are the 3 effects of H+ secretion by the tubule?
Drives reabsoprtion of bicarbonate
Forms "acid-phosphate" - titratable acid
Forms ammonium ion
131
Why is the vast majority of H+ secretion used for bicarb reabsorption?
To prevent generation of acidoses
