1
Q
Define osmolarity
A
- concentration of osmotically active particles present in a solution
- mosmol/l
2
Q
Calculate the osmolarity of 150mM of NaCl
A
- molar conc = 150
- 2 active particles
2x150 = 300
3
Q
What is the rough body fluid osmolarity?
A
- 300mosmol/l
4
Q
Unit for osmolality?
A
- osmol/kg water
5
Q
Unit of osmolarity?
A
- mosmol/l
6
Q
Define tonicity
A
- the effect a solution has on a cell volume
7
Q
Describe isotonic
A
- no change in cell volume
8
Q
Describe hypotonic
A
- cells swell
- number of particles is less in the plasma
9
Q
Describe hypertonic
A
- cells shrink
- number of particles in plasma is more
10
Q
Effect of RBC in urea solution?
A
- urea moves into RBC due to receptors
- water follows
- cells swell
11
Q
Effect of RBC in sucrose solution?
A
- no affect - isotonic
- no direct receptors
12
Q
What is the intracellular percentage of total body water?
A
- 2/3rds
13
Q
What is the extracellular percentage of total body water?
A
- 1/3rd
14
Q
What is extracellular compartment composed of?
A
- plasma
- interstitial fluid
15
Q
What tracer can be used for ECF?
A
- inulin
16
Q
What tracer can be used for plasma volume
A
- labelled albumin
17
Q
What ions are in higher concentration in the extracellular compartment?
A
- Na
- Cl
- HCO3
18
Q
What ions are in higher concentration in the intracellular compartment?
A
- k+
19
Q
What separates the intracellular and extracellular components?
A
- plasma membrane
- cell membrane
20
Q
What separates the plasma and interstitial fluid
A
- capillary wall
21
Q
How can plasma osmolarity be estimated?
A
- doubling Na concentration
22
Q
Increase in NaCl in ECF causes what to water concentrations in ECF and ICF
A
- ECF = Increase water
- ICF = decrease water
23
Q
General rule for Na and water
A
- water follows sodium
24
Q
Why is it important to regulate electrolytes?
A
- directly affects water balance
- affects cell function
25
What are the most important electrolytes to balance?
- Na
| - K
26
Where is the majority of sodium found?
- ECF
27
Where is the majority of K+ found
- ICF
28
Loss of potassium balance can lead to?
- muscle weakness
| - cardiac irregularities
29
Name some functions of the kidneys?
- water and salt balance
- maintenance of plasma volume
- acid base balance
- endocrine gland
- vitamin d activation
30
What is the functional unit of the kidney
- the nephron
31
What are the 3 functional mechanisms of the nephron?
- filtration
- reabsorption
- section
32
Explain the blood supply to cortical nephron
- artery
- afferent arteriole
- glomerulus
- efferent arterole
- peritubular capillaries
- vein
33
What is the blood supply to the juxtamedullary nephron?
- vasa recta
34
Differences between juxtamedullary nephron and the cortical nephron?
- Loop of henle much longer in juxtamedullary nephron
- vasa recta
- concentrated
35
What lines the inner aspect of Bowman's capsule?
- podocytes
36
Explain the juxtaglomerular apparatus
- distal tubule passes between afferent and efferent arterioles
37
What cell releases renin
- granular cells
38
What is responsible for sensing sodium concentrations
- macula densa cells
| - sense sodium and signal smooth muscle in afferent arteriole to control blood flow into glomerular capillaries
39
The __efferent/afferent___ arteriole goes into the glomerulus?
- afferent
40
What percentage of the plasma that goes through the kidneys is not filtered?
- 80%
41
Define rate of filtration
= Xplasma conc x GFR
| - Mass of X filtered into bowman's capsule per unit time
42
Normal GFR for healthy adult
125ml/min
43
Rate of excretion calculation?
= X urine conc x urinary flow
| - mass of x excreted per unit time
44
Rate of absorption calculation
= rate of filtration of X - rate of excretion of X
45
Which has a larger diameter the afferent or efferent arteriole?
- the afferent arteriole has a larger diameter
46
What are the 3 barriers to filtration in the glomerulus?
- glomerular capillary endothelium
- basement membrane
- slit processes of podocytes
47
What does the glomerular capillary endothelium barrier against?
- RBC
48
What does the basement membrane and slit processes of podocytes barrier against?
- plasma proteins
49
Glomerular filtration is a ___ process?
- passive
50
What are the 4 glomerular pressures in glomerular filtration?
- Glomerular capillary blood pressure
- bowman's capsule hydrostatic pressure
- capillary oncotic pressure
- bowman's capsule oncotic pressure
51
What is the net filtration?
10 mmHg favouring filtration
52
Define the glomerular filtration rate
- the rate at which protein free plasma is filtered from the glomeruli into the bowman's capsule per unit time
53
Normal GFR
125
54
What is the major determinant of GFR?
- Glomerular capillary fluid pressure
55
What are some extrinsic regulations of GFR?
- Vasocontriction of afferent arterioles
| - vasodilation of afferent arterioles
56
What are the 2 processes of autoregulation of GFR?
- Myogenic
| - Tubuloglomerular
57
Increase in BP causes and increase in ____
- GFR
58
Describe myogenic autoregulation of GFR?
- Smooth muscle of afferent arteriole
- - if vascular smooth muscle stretched
- contracts to reduce flow
59
Explain tubuloglomerular feedback?
- increase in GFR
- more salt present
- picked up by macula densa cells
- constriction of afferent arterioles
- reducing GFR
60
Where does tubuloglomerular feedback occur?
- juxtaglomerular apparatus
61
Describe plasma clearance
- measure of how effectively the kidneys can clean the blood of a substance
- the volume of plasma cleared per minute
62
What is the gold standard for GFR?
- Inulin
| - Inulin clearance = GFR
63
What can be used as a close approximation of GFR?-
- Creatinine clearance
64
What is the usual glucose clearance?
- 0ml/min
65
Urea clearance is what compared to GFR?
Clearance < GFR
| - Reabsorbed
66
H+ clearance is what compared to GFR?
- Clearance > GFR
| - Secreted
67
What can be used as a marker of renal plasma flow?
- para-amino hippuric acid
68
para-amino hippuric acid is __endogenous/exogenous__
- exogenous
69
Calculation of filtration fraction
- the fraction of the plasma flowing through the glomeruli that is filtered into the tubule
70
What percentage of plasma that enters the glomeruli is filtered?
- 20%
71
What is the equation for plasma clearance?
clearance of substance x = x conc in urine x urinary flow / x conc in plasma
72
What is the normal renal plasma flow rate?
650ml/min
73
If clearance > GFR that shows the substance was ___reabsorbed/secreted___
- secreted
74
How is filtration fraction calculated?
GFR/Renal plasma flow
75
Describe glomerular filtrate compared to blood?
- modified version
- contains ions and solutes at plasma concentrations
- lacks RBCs and large plasma proteins
76
Describe transcellular reabsorption
- directly across the wall of the nephron
77
Describe paracellular reabsorption
- dependant on how leaky or tight the cell junctions are
78
Describe primary active transport
- energy dependant
| - move substances against their concentration gradient
79
Describe secondary active transport
- carrier molecule transported coupled to an ion gradient
| - e.g. Na+
80
Describe facilitated diffusion
- passive carrier mediated transport
| - down concentration gradient
81
Glucose crosses the nephron wall by what type of transport?
- facilitated diffusion
82
Where is the majority of sodium reabsorbed?
- proximal convoluted tubule
83
Where is sodium not reabsorbed?
- in the descending limb of the loop of henle
84
What are some examples of the apical membrane transporters for sodium
- na+/glucose
- na+/amino acid
- na+/h+
85
What is the net movement of sodium in the primary convoluted tubule?
- from the filtrate into the interstitial fluid
86
Sodium net movement creates an electrical chemical gradient for what substance?
- chloride
87
Sodium net movement creates an osmotic gradient for what substance?
- water
88
Where is the majority of glucose reabsorbed in the nephron?
- proximal convoluted tubule
89
What is the transporter for glucose from the filtrate into the cells of the nephron?
- Na+/glucose transporter
90
Describe the renal threshold for glucose?
- saturation of glucose transporters
- usually around 10-12mmol/l
- excess glucose will be excreted
91
What is the function of the loop of Henle?
- creation of a portico-medullary solute concentration gradient
92
What is the aim of the loop of henle?
- to greater a hypertonic urine formation
93
What is the name process that occurs to produce a hypertonic urine solution?
- countercurrent multiplication
94
The flow through the loop of henle is described as?
- countercurrent flow
95
The descending limb of the loop of henle is responsible for what?
- water reabsorption
- no NaCl- reabsorption
- causes tubular fluid to become hyperosmotic
96
The ascending limb of the loop of henle is responsible for what?
- NaCl- reabsorption
| - no water reabsorption
97
The triple co transporter is found where and what is its function?
- ascending limb of the loop of henle
- Na+
- K+
- Cl-
98
Loop diuretics block what process?
- triple co transporter
99
Function of the triple co transporter
- to allow solute reabsorption in the ascending limb of the loop of henle
- subsequent creation of a hyperosmotic interstitial fluid
- passive movement of water in the descending limb
100
What forms the countercurrent system?
- loop of henle and the vasa recta
101
What hormones are involved in water and solute balance in the renal system?
- ADH
- Aldosterone
- atrial naturitic hormone
- parathyroid hormone
102
ADH aim?
- increasing water reabsorption
- concentrated urine
- increase blood volume and pressure
103
Where is ADH made and by what?
- hypothalamus
| - supraoptic and paraventricular nuclei
104
Where is ADH stored and what releases it?
- stored in posterior pituitary
| - calcium dependant exocytosis
105
What acts as a stimulus to release ADH?-
- Dehydration
| - increase osmolarity
106
What detects an increase in plasma osmolarity?
- hypothalamic osmoreceptors
107
What is the effect of ADH?
- Binds to vasopressin 2 receptor
- increase in cAMP
- Increase in aquaporins
- water absorption
108
Where does ADH target?
- distal convoluted tubule
| - collecting duct
109
Low ADH creates a what urine?
- hypotonic
| - dilute
110
High ADH creates a what urine?
- hypertonic
| - concentrates
111
Other than on aquaporin formation what does ADH also do?
- arterial vasoconstriction
112
Describe central diabetes insipidus?
- failure to produce ADH
113
Describe nephrogenic diabetes insipidus?
- failure to respond to ADH
114
Symptoms of diabetes insipidus?
- large volume dilute urine
| - thirst
115
What are other factors that may cause ADH release?
- high osmolarity of plasma
- atrial stretch receptors
- stretch receptors in GI tract
- alcohol inhibits
- nicotine stimulates
116
Aldosterone is what type of hormone?
- steroid
117
Where is aldosterone secreted from?
- adrenal cortex
118
When is aldosterone secreted?
- low Na+
- low ECF volume
- High k+
119
Renin is released from what cells?
- granular cells
120
Aldosterone effect?
- Na+ reabsorption
121
3 factors that stimulate renin release?
- reduced afferent arteriole pressure
- Less NaCl in macula densa
- increased sympathetic activity
122
Treatment of an abnormal RAAS system?
- ACEi
| - Loop diuretic
123
Where is ANP stored?
- atrial muscle cells
124
When is ANP released?
- mechanical stretching of the atria
125
ANP effect
- excretion of Na+
| - diuresis
126
What are the 2 controls of bladder excretion?
- micturition reflex (involuntary)
| - voluntary
127
Describe water diuresis?
- increased urine flow but no increased solute excretion
128
Describe osmotic diuresis?
- increased urine flow because of a primary increase in salt excretion
129
What is the pH of arterial blood
- 7.45
130
What is the pH of venous blood
- 7.35
131
Acidosis is described a pH of what?
- less than 7.35
132
Alkalosis is defined as a pH of what?
- more than 7.45
133
Define a strong acid
- completely dissociates in solution
134
Define a weak acid
- partially dissociates in solution
135
The dissociation constant is equal to what?
- the pH at which equilibrium is achieved
136
What catalyses H2CO3 --> HCO3- + H+
- Carbonic anhydrase
137
Role of the kidney in control of HCO3-
- Variable reabsorption of filtered HCO3-
- Kidneys can add new HCO3- to blood
- dependant on H+ secretion
138
Explain bicarbonate reabsorption in the kidney?
- cannot be transported directly
- combines with H+
- Broken down to CO2 + H20
- Transported into cell
- reformed into HCO3-
139
What are the 2 buffering systems important in H+ concentraion
- phosphate
| - ammonia
140
If HCO3- is low in tubular fluid what does the H+ bind to?
- ammonia
- phosphate
- for excretion
141
Define compensation
- restoration of pH
| - irrespective of pCO2 and HCO3-
142
Define correction
- restoration of pH
| - restoration of pCO2 and HCO3-
143
What diagram shows the distribution of acid base balance
- Davenport
144
Causes of respiratory acidosis
- retention of CO2
- Chronic bronchitis
- hypoventilation
145
Compensatory affect of respiratory acidosis?
- further increase in HCO3-
146
Causes of respiratory alkalosis
- hyperventerlation
| - hypoxia
147
Compensation affect of respiratory acidosis?
- further lowering of HCO3-
148
Causes of metabolic acidosis
- ingestion of acids
| - excessive loss of base e.g. diarrhoea
149
Causes of metabolic acidosis
- loss of HCl through vomit
150
Compensation affect for metabolic alkalosis
- further HCO3- increase
Renal
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