Physiology Flashcards
1
Q
Osmolarity
A
Number of solute particles per litre
2
Q
Osmolarity of body fluids
A
300mosmol/L
3
Q
Specific gravity
A
Weight of particles
4
Q
Total body water exists as 2 major compartments
A
ECF
ICF
5
Q
ECF includes:
A
Plasma
IF
Lymph and transcellular fluid
6
Q
How are fluid compartments measured?
A
Tracers
7
Q
Useful tracers
A
TBW: water
ECF: Inulin
Plasma: albumin
8
Q
How to calculate volume
A
V = Dose/Concentration
9
Q
Main ions in ECF
A
Na
Cl
HCO3-
10
Q
Main ions in ICF
A
K
Mg
Negatively charged proteins
11
Q
Changes in ICF/ECF during gain/loss of water
A
Similar changes (both increase or decrease)
12
Q
Changes in ICF/ECF during gain/loss of NaCl
A
Opposite changes (one increases and other decreases)
13
Q
What happens in gain/loss of isotonic fluid?
A
No change in fluid osmolarity, change in ECF only
14
Q
Electrolyte
A
Any substance that dissolves to form free ions
15
Q
What ion plays a role in establishing membrane potential?
A
K
16
Q
Effects of hypokalaemia
A
Paralysis
Cardiac arrest
17
Q
How is salt imbalance manifested?
A
Changes in ECF volume
18
Q
2 types of nephron
A
Juxtamedullary
Cortical
19
Q
Juxtamedullary nephrons
A
Long loop of henle
Vasa recta
Concentrated urine
20
Q
Cortical nephrons
A
Short loop of henle
Peritubular capillaries
21
Q
Function of macula densa
A
Modified tubular cells
Sense NaCl content
22
Q
Granular/juxtamedullar cells
A
Secrete renin
23
Q
What % of plasma that enters glomerulus is filtered?
A
20%
24
Q
Rate of filtration
A
[X]plasma x GFR
25
Rate of excretion
[X]urine x urine flow rate (Vu)
26
Rate of reabsorption
Rate of filtration - Rate of excretion
| Filtration > Excretion
27
Rate of secretion
Rate of excretion - Rate of filtration
| Filtration
28
3 layers of filtration barrier/glomerular membrane
Glomerular capillary endothelium
Basement membrane
Slit processes of podocytes
29
Forces comprising net filtration pressure
Glomerular capillary hydrostatic pressure (55) BPgc
Bowman's capsule hydrostatic pressure (15) HPgc
Glomerular Capillary oncotic pressure (30) COPgc
Bowman's capsule oncotic pressure (0) COPbc
30
Net filtration pressure
10mmHg
31
Major determinant of net filtration pressure
Glomerular capillary hydrostatic pressure (BPgc)
| Constant along capillary (due to back pressure, smaller efferent)
32
GFR
Rate at which protein free plasma is filtered
| Kf x net filtration pressure
33
What happens to urine if GFR increases/decreases?
GFR increases = more urine
| GFR decreases = less urine
34
Extrinsic regulation of GFR
Sympathetic control - baroreceptor reflex
| BPgc controlled by vasoconstriction/dilation
35
Intrinsic autoregulation of GFR
Myogenic mechanism
| Tubuloglomerular feedback
36
Effect of vasoconstriction on GFR
Less blood flow = decreased BPgc = decreased GFR
37
Effect of vasodilation on GFR
More blood flow = increased BPgc = increased GFR
38
Autoregulation
Stops short term changes in BP affecting GFR
39
Myogenic mechanism of autoregulation
Increased BP = vascular smooth muscle stretched = vasoconstriction of afferent
40
Tubuloglomerular feedback mechanism of autoregulation
If GFR rises = more NaCl detected by JGA = vasoconstriction of afferent
41
Which type of control can override?
Extrinsic control, e.g. in haemorrhage
42
What pathology increases HPbc
Kidney stone
| Decreased GFR
43
What pathology increases COPgc
Diarrhoea
| Decreased GFR
44
What pathology decreases COPgc
Burns
| Increased GFR
45
What pathology decreases Kf
Physical damage
| Decreased GFR
46
Plasma clearance
Measure of how effectively plasma cleared of a substance ml/min
47
How to calculate clearance
Rate of excretion/Plasma concentration
48
Inulin and creatinine clearance
= GFR
| Filtered, not reasorbed or secreted
49
Glucose clearance
= 0
| Filtered, completely reabsorbed
50
Urea clearance
less than GFR, reabsorbed
51
H+ clearance
> GFR
| Filtered, secreted, not reabsorbed
52
What do you use to calculate RPF
PAH (filtered, secreted completely, not reabsorbed, completely cleared from plasma)
53
RPF
650ml/min
54
RBF
1200ml/min
55
Fluid reabsorbed in PCT is ________ with filtrate
Iso-osmotic
56
What is reabsorbed in PCT?
```
Sugars 100%
Amino acids 100%
Phosphate
Sulphate
Lactate
Na 67%
```
57
What is secreted in PCT?
```
H+
Hippurates
NTs
Bile pigments
Uric acid
Drugs
Toxins
```
58
Barriers to transcellular reabsorption
Apical membrane, tubular cell, basolateral membrane, interstitial fluid, capillary endothelium
59
Primary active transport
Energy directly required (hydrolysis of ATP) to move substance against concentration gradient, e.g. Na/K
60
Secondary active transport
Carrier molecule transported coupled to ion concentration gradient (Na) e.g. Na/glucose
61
Symport
Secondary AT in same direction
62
Antiport
Secondary AT in opposite directions
63
What is essential for Na reabsorption?
Na/K on basolateral membrane
64
Water is reabsorbed via what route?
Paracellular route - follows Cl
65
After glucose transporters are saturated, what happens?
Glucose excretion
66
Transport maximum for glucose
2mmol/min
67
Tubular fluid is ________ when it leaves PCT
Iso-osmotic 300mosmol/L
68
Function of LOH
Generates concentration gradient to allow formation of concentrated urine
69
Opposing flow in 2 limbs of LOH is termed:
Countercurrent flow
70
The LOH and vasa recta establish a __________ medullary IF
Hyperosmotic
71
NaCl reabsorption in thin ascending limb
Passive
72
NaCl reabsorption in thick ascending limb
Active transport
73
Fluid entering ascending LOH is:
Hypertonic
74
Fluid leaving LOH and entering DCT is:
Hypotonic 100mosmol/L
75
What else contributes to medullary osmolarity?
Urea cycle
76
Where is urea recycled?
Between CD and ascending LOH
77
2 solute hypothesis contributing to medullary gradient
NaCl
| Urea
78
Range of urine production
0.3-25ml/min
79
What is the countercurrent exchanger?
Vasa recta
80
ANP functions
Decreases Na reabsorption
Vasodilation of afferent arteriole
Decreases BP
Decreases symp activity
81
PTH functions
Na reabsorption
| Phosphate excretion
82
Early DCT
Na/K/2Cl
83
Late DCT
Ca reabsorption
Na reabsorption
K reabsorption
H secretion
84
Where is ADH receptor?
Basolateral membrane of DCT and CD
85
Functions of ADH
Increases aquaporins at apical membrane
86
In presence and absence of ADH where is impermeable to water?
Absence: ascending LOH, DCT, CD
Presence: ascending LOH
87
At what bladder volume do stretch receptors initiate micturition reflex?
250-400ml
88
Stimuli for ADH release?
Hypothalamic osmoreceptors
Left atrial stretch receptors
Upper GIT = feedforward inhibition
Nicotine stimulates ADH, alcohol inhibits ADH
89
Stimuli for aldosterone release?
Increase in plasma K directly stimulates adrenal cortex
| Decrease in plasma Na = JGA = RAAS
90
Stimuli for renin release?
Reduced pressure in afferent arteriole
Reduced Na detected by macula densa
Reduced BP = increased symp activity = granular cells stimulated
91
Treatment for HF
Low Na diet
Loop diuretic
ACEI
92
Where is ANP produced?
Heart
93
Stimuli for ANP release
Stretch receptors in heart due to increased BP
94
Acidosis can lead to:
Depression of CNS
95
Alkalosis can lead to:
Overexcitability of PNS then CNS
96
Strong acids dissociate __________ in solution
Completely
97
The most important physiolgical buffer is:
CO2/HCO3-
98
What drives bicarbonate reabsorption?
H+ secretion
99
What drives H+ secretion?
CO2 retention
100
What happens when bicarbonate in tubular fluid is low?
Secreted H+ combines with phosphate = acid phosphate excreted (H2PO4)
101
Amount of H+ secreted as acid phosphate can be measured as:
titratable acid
102
What rids the body of buffer stores?
TA and ammonia
103
Compensation
Restoration of pH irrespective of what happens to bicarb and CO2
104
Correction
Resoration of pH and bicarb and CO2
105
Examples of respiratory acidosis
COPD - chronic bronchitis, chronic epmhysema, asthma, tumour
106
Respiratory acidosis on Davenport diagram
Left and up of normal
107
How is respiratory acidosis compensated?
Bicarb reabsorbed, H+ secreted as TA and ammonia
| New bicarb added to blood
108
Why does bicarb rise in respiratory acidosis?
As a result of the disease (equation to right)
| As a result of renal compensation (excreting acid, adding new bicarb)
109
How do you correct resiratory acidosis?
Restoring normal ventilation
110
Causes of respiratory alkalosis
Hyperventilation, fever, altitude
111
Respiratory alkalosis on Davenport diagram
Right and down of normal
112
Compensation in respiratory alkalosis
Excess removal of CO2 = decreased H+ secretion = can't reabsorb bicarb = bicarb excreted in urine
No TA or ammonia formed = no new bicarb
Renal compensation further lowers bicarb
113
How do you correct respiratory alkalosis?
Restore normal ventilation
114
Causes of metabolic acidosis
Excess H+ from sources other than CO2
Ingestion of acids, DKA, lactic acidosis during exercise
Excess loss of base (diarrhoea)
115
Why is bicarb depleted in metabolic acidosis?
Buffers excess H+
| Loss of bicarb (diarrhoea)
116
Respiratory compensation in metabolic acidosis
Decrease pH stimulates peripheral chemoreceptors = ventilation increases = CO2 blown off
H+ and bicarb lowered
117
Metabolic acidosis on Davenport diagram
Left and down of normal
118
Correction for metabolic acidosis
H+ secretion = TA and ammonia formed to generate more bicarb
| Acid load excreted
119
Metabolic alkalosis
Excess loss of H+ from the body
120
Causes of metabolic alkalosis
Vomiting, ingestion of alkali, aldosterone hypersecretion
121
Metabolic alkalosis on Davenport diagram
Right and up from normal
122
Respiratory compensation for metabolic alkalosis
Increased pH slows ventilation (peripheral chemoreceptors)
| CO2 retained = H+ rises, bicarb rises
123
Correction for metabolic alkalosis
Not all filtered bicarb reabsorbed
| No TA or ammonia = bicarb excreted
