Physiology Flashcards
1
Q
What is tonicity?
A
The effect a solution has on a cell.
2
Q
How much fluid in the body is intracellular and extracellular?
A
Intra- 67%
Extra- 33%
3
Q
What are the 4 compartments and percentages of extracellular body fluid?
A
Plasma- 20%
Interstitial fluid- 80%
Lymph- Negligible
Transcellular- Negligible
4
Q
What tracer can be used to measure total body water?
A
3H2O- Ditritrium oxide/T2O
5
Q
What tracer can be used to measure ECF?
A
Inulin
6
Q
What tracer can be used to measure plasma?
A
Labeled albumin
7
Q
What is the function of the kidneys?
A
Water and salt balance Acid base balance Excrete waste and drugs Maintain plasma volume and osmolarity Secrete renin and erythropoietin Activate VD
8
Q
What is the primary function of the kidney?
A
To regulate volume, composition and osmolarity of body fluids.
9
Q
What is the functional unit of the kidney?
A
Nephron
10
Q
What are the two types of nephron?
A
Juxtamedullary
Cortical
11
Q
What are some of the important parts of the nephron?
A
Blood vessels Glomerulus Proximal tubule Loop of Henle Distal tubule Collecting duct
12
Q
What are the two parts of the loop of Henle?
A
Descending and ascending limbs
13
Q
What is the glomerulus contained within?
A
Bowman’s capsule
14
Q
What is found next to the glomerulus between the afferent and efferent arterioles?
A
Juxtaglomerular apparatus
15
Q
What two special cell types are found in the juxtaglomerular apparatus?
A
Granular cells
Macula densa
16
Q
What percentage of the plasma that enters the glomerulus is filtered?
A
20%
17
Q
What two things can occur between the tubules and peritubular capillaries?
A
Tubular secretion and reabsorption
18
Q
How do you calculate the rate of filtration?
A
[X]plasam x GFR
19
Q
How do you calculate the rate of excretion of a substance?
A
[X] urine x Vu (urine flow rate)
20
Q
How do you calculate the rate of reabsorption of a substance?
A
Rate of filtration of X - rate of excretion of X
21
Q
How do you calculate the rate of secretion of a substance?
A
Rate of filtration of X - rate of excretion of X
22
Q
What are some barriers to filtration?
A
Endothelium
Basement membrane
Podocytes
23
Q
How do barriers to filtration work?
A
Physical barrier
Charge barrier
24
Q
What four forces control GFR?
A
Glomerular capillary blood pressure (BPgc)
Bowman’s capsule oncotic pressure (COPbc)
Capillary oncotic pressure (COPgc)
Bowman’s capsule hydrostatic pressure (HPbc)
25
Which two forces govern fluid leaving the capillaries into the bowman's capsule?
Glomerular capillary blood pressure (BPgc)
| Bowman's capsule oncotic pressure (COPbc)
26
Which two forces govern fluid leaving the bowman's capsule into the capillaries?
Capillary oncotic pressure (COPgc)
| Bowman's capsule hydrostatic pressure (HPbc)
27
Under normal conditions what are the values for the four forces governing GFR?
Glomerular capillary blood pressure- 55mmHg
Bowman's capsule oncotic pressure- 0mmHg
Capillary oncotic pressure- 30mmHg
Bowman's capsule hydrostatic pressure-15mmHg
28
What is the net filtration pressure normally?
10mmHg
29
What is another term for the forces governing GFR?
Starling forces
30
What is GFR?
Rate at which protein free plasma is filtered from glomerulus into bowman's capsule per unit time
31
How do you calculate GFR?
Kf (how holey the membrane is) x net filtration pressure
32
What is normal GFR?
125ml/min
33
What is an extrinsic method of regulating GFR?
Alter diameter of blood vessels to glomerulus
34
What are the two intrinsic/autoregulation mechanisms of regulating GFR?
Myogenic
| Tubuloglomerular feedback
35
What does myogenic autoregulation involve?
Vascular smooth muscle into kidneys increases then automatically constricts.
36
What does tubuloglomerular feedback autoregulation involve?
Juxtaglomerular apparatus- mechanism unknown.
| Rise in GFR leads to more NaCl in tubules causing constriction.
37
What do the macula densa cells in the juxtaglomerular apparatus do?
Sense NaCl
38
What can raise the Bowman's capsule hydrostatic pressure (HPbc) and what effect does this have of GFR?
Renal stones. Decrease GFR.
39
What can raise the Capillary oncotic pressure (COPgc) and what effect does this have on GFR?
Diarrhoea. Decrease GFR.
40
What can drop the Capillary oncotic pressure (COPgc) and what effect does this have on GFR?
Severe burns. Increase GFR
41
What is plasma clearance?
How effectively the kidneys can clear the blood of a substance.
42
How do you calculate plasma clearance?
[X]urine x Vurine/[X]plasma
43
What are the units for plasma clearance?
ml/min
44
Clearance of what substance is GFR based on?
Inulin
45
Why is inulin good for calculating GFR?
```
Freely filtered
Not reabsorbed or secreted
Not metabolised my kidney
Not toxic
Easy to measure
```
46
What is normal clearance of inulin?
125ml/min
47
is glucose filtered?
Yes
48
If it is filtered why is glucose not normally seen in the urine?
Completely reabsorbed.
49
Why does urea have a clearance lower then GFR?
Freely filtered and partly reabsorbed
50
Why does H+ have a clearance higher than GFR?
Filtered and secreted
51
What is renal plasma flow?
Amount of blood flowing through the kidneys
52
What can be used to calculate renal plasma flow?
PAH
53
How can PAH be used to calculate renal plasma flow?
Because it is freely filtered and the molecules that don't get filtered get secreted out.
54
What is normal renal plasma flow?
650ml/min
55
What is the filtration fraction?
Fraction of plasma passing through kidneys that is filtered.
56
What is the normal filtration fraction?
20%
57
How much of the GFR is normally reabsorbed in the proximal tubule?
80ml/min
58
How much fluid normally enters the loop of Henle?
45ml/min
59
How does the fluid reabsorbed from the proximal tubule compare to the osmolarity of the filtrate?
Iso-osmotic
60
What is reabsorbed in the proximal tubule?
```
Sugars
AA
Phosphate
Sulphate
Lactate
```
61
What is secreted in the proximal tubule?
```
H+
PAH
NTs
Bile pigments
Uric acid
Drugs/toxins
```
62
What are the two forms of reabsorption?
Transcellular
| Paracellular
63
How does Na cross the luminal membrane of the proximal tubule?
Passive diffusion through channels
64
How does Na cross the basolateral membrane of the proximal tubule?
NaKATPase
65
Is NaKATPase a primary or secondary active transporter?
Primary
66
What two substances can Na conc gradient be used to reabsorb in the proximal tubule?
Glucose
| AA
67
What substance can Ns conc gradient be used to secrete in the proximal tubule?
H+
68
How does H2O and Cl get reabsorbed?
Paracellular following Na
69
How does glucose cross the luminal membrane?
NaGlucose transporter
70
How does glucose cross the basolateral membrane?
Facilitate transport down conc gradient
71
At what conc does glucose reabsorption get saturated?
2mmol/min
72
What is the point of the loop of Henle?
To generate a conc gradient to form hypertonic urine
73
What is flow in the loop of Henle called?
Countercurrent
74
What is absorbed in the ascending loop of Henle?
Na and Cl but no water
75
What is absorbed in the descending loop of Henle?
Water
76
How does the countercurrent system in the loop of Henle work?
NaCl absorbed in the ascending loop increases osmolarity of blood in vessels between ascending and descending thus drawing water out of descending.
77
What allows for Na and Cl reabsorption at the luminal membrane of the ascending loop of Henle?
NaKCl triple transporter
78
What drug blocks the NaKCl tripler transporter?
Loop diuretics
79
What is the point of the countercurrent mechanism?
To allow for the production of different conc and volume of urine depending on ADH levels
80
What is the normal urine flow rate?
1ml/min
81
What runs alongside the loop of Henle in juxtamedullary nephrons?
Vasa recta
82
What does vasa recta mean?
Straight vessels
83
What do the vasa recta do?
Form the blood component of countercurrent mechanism.
84
How does the osmolarity of the fluid in the distal tubule compare to that of plasma?
Hypo-osmotic
85
What is reabsorbed in the distal tubule?
NaCl and water
86
What controls reabsorption in the distal tubule?
Hormones
87
What hormones act on the distal tubule?
ADH
Aldosterone
ANH
Parathyroid hormone
88
What effect does ADH have on the distal tubule?
Increase H2O reabsorption by increasing aquaporins
89
What effect does aldosterone have on the distal tubule?
Increase Na reabsorption
| Increase K and H+ secretion
90
What effect does ANH have on the distal tubule?
Decrease Na reabsorption
91
What effect does parathyroid hormone have of the distal tubule?
Increase Ca reabsorption
| Decrease PO reabsorption
92
Is the distal tubule permeable to urea?
Not really
93
What happens to urea in the distal tubule?
Concentrated
94
What happens in the early distal tubule?
NaCl reabsorption through NaKCl triple transporter
95
What happens in the late distal tubule?
Ca, Na, Cl and H2O reabsorption
| K and H+ secretion
96
What happens in the early collecting duct?
Ca, Na, Cl and H2O reabsorption
| K and H+ secretion
97
What happens in the late collecting duct?
Low ion permeability
| Permeability to urea and H2O through ADH/aquaporins
98
What is the HL of ADH?
15 minutes
99
Where is ADH released from?
Posterior pit
100
How does ADH work?
Increases aquaporin numbers
101
What do high levels of ADH do?
Increase reabsorption of H2O leading to conc urine
102
What do low levels of ADH do?
Decrease reabsorption of H2O leading to dilute urine
103
What disease is caused by a lack of ADH?
Diabetes insipidus
104
What stimulates ADH release?
Decreased atrial pressure and nicotine
105
What inhibits ADH release?
Feeding and alcohol
106
Where is aldosterone released from?
Adrenal cortex
107
What stimulate aldosterone secretion?
Rising K (directly) or falling Na (vis juxtaglomerular apparatus)
108
How does aldosterone increase Na reabsorption?
Na reduction sensed by macula densa.
Macula dense stim renin release from granular cells
RAAS activated
109
Where does aldosterone act?
Distal tubule and collecting duct
110
How can aldosterone cause hypertension?
Failing heart decreases output leading to a perceived low BP which stims RAAS and increased Na levels
111
Where is ANP made?
Atrial cells
112
What causes ANP release?
Stretching of atria cells due to increased volume
113
What does ANP do?
Increases secretion of Na
114
What are three potential markers of GFR?
Inulin
Urea
Creatinine
115
Give some advantages of inulin for measuring GFR?
Appears at constant rate
Freely filtered
Not reabsorbed or secreted
No extra-renal elemination
116
Give some disadvantages of inulin for measuring GFR?
Not endogenous
| Not easy to measure
117
Give some advantages of urea for measuring GFR?
Endogenous
Easy to measure
Freely filtered
Not secreted
118
Give some disadvantages of urea for measuring GFR?
Does not appear at constant rate
Reabsorbed
Extra-renal elimination
119
Give some advantages of creatinine for measuring GFR?
```
Endogenous
Easy to measure
Freely filtered
Constant rate
Nor reabsorbed
No extra-renal met
```
120
Give some disadvantages of creatinine for measuring GFR?
Secreted
121
What can confuse creatinine readings?
Age
Sex
Muscle mass
Diet
122
Are plasma proteins normally filtered out?
No
123
How do you estimate protein in the urine?
Dipstick then 24h urine collection
124
What level of protein in the urine indicates significant glomerular damage?
>150mg/day
125
How does nephrotic syndrome work?
Loss of albumin results in fluid leaking out of vessels to cause oedema.
126
What are the 4 categories of protein in the urine?
Normal
Microalbuminuria
Clinical proteinuria
Nephrotic
127
What is microalbuminuria?
Abnormal quantities of albumin being secreted but not enough to give a dipstick reading.
128
Is microalbuminuria seen in diabetes?
Yes, earliest sign of diabetic nephropathy.
