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Renal Flashcards

(107 cards)

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1
Q

What is the glomerular filtration rate?

A

The volume of fluid filtered from the renal glomerular capillaries into bowman’s capsule per unit time

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2
Q

How do the kidneys regulate body fluid composition?

A

By producing urine tailored to the body’s requirements at any time

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3
Q

How do reabsorption and secretion occur at a normal rate?

A

Renal blood flow and GFR are controlled to maintain fairly constant over moderate changes in arterial BP

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4
Q

What is clearance?

A

The removal of substances from the plasma and their excretion in urine

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5
Q

Give an example of something that is never cleared and something that is fully cleared from the body

A

Glucose - zero clearance
Para-aminohippuric acid - fully cleared

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6
Q

What is the clearance equation?

A

Cx = Ux . V / Px
Cx - clearance of x
Ux - conc of x in urine
V - urine flow rate
Px - conc if x in plasma

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7
Q

What happens when a solute is fully cleared?

A

The volume of plasma which flow into the kidneys is the same as the clearance of that solute

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8
Q

How is PAH used to test the body’s ability to clear substances?

A

It is injected into the plasma
Wait one hour
Measure the conc in arterial plasma and urine and the urine flow rate of the hour
Then use the equation

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9
Q

Why is renal blood flow not measured?

A

RBCs are not present in the plasma or the urine and the Ppah and Upah already omit these

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10
Q

How would you calculate renal blood flow?

A

RBF = RPF x (1 / 1- Hct)
RBF - renal blood flow
RPF - renal plasma flow
Hct - haematocrit

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11
Q

What criteria must be met in order to test the clearance function of the kidneys?

A

1) substance must be freely filtersble in the glomeruli
2) substance must be neither reabsorbed nor secreted by the tubules
3) substance must not be synthesised, broken down, nor accumulated by the kidney
4) substance must be physiologically inert

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12
Q

What two substances are routinely used to test clearance?

A

Insulin
Creatinine

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13
Q

How do you determine clearance when using inulin or creatinine?

A

Urine is collected over a 24hr period to determine flow rate
The conc of inulin/creatinine is taken from the urine
The conc of inulin/creatinine is taken from a blood sample

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14
Q

What is a normal GFR for men?

A

90-140 mL/min

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15
Q

What is a normal GFR for women?

A

80-125 mL/min

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16
Q

Why is determining GFR using clearance important?

A

It helps diagnose and monitor renal disease
Can help determine how the kidneys handles particular solutes - are they reabsorbed or secreted etc
Is important in the design of clinically useful drugs

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17
Q

How do you calculate the filtered load?

A

Fx = GFR x Px

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18
Q

What is the transport rate?

A

The difference between what was filtered and what was in urine

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19
Q

Why is transport rate significant?

A

Whether it has a positive or negative sign allows you to determine whether a substance was reabsorbed or secreted

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20
Q

How is creatinine concentration determined in a urine sample?

A

1mL or urine sample
1mL of creatinine standard
To both add 1mL of picuric acid and 1mL of NaOh
Wait ten minutes
Use colorimeter on both

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21
Q

Du is the optical density of the urine sample
Ds is the optical density if the standard what calculation do you use to find the creatinine conc in the 200mL urine sample?

A

(Du x Ds) x 0.1 x 200 / 15
= 1.33 (Du x Ds)

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22
Q

Why do you get a diuresis with 700mLs of water?

A

…

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23
Q

What is pharmacodynamics?

A

What drugs do to our bodies

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24
Q

What is pharmacokinetics?

A

What our bodies do to the drug

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25
What does pharmacokinetics depend on?
Absorption Distribution Metabolism Excretion
26
What is the therapeutic window?
A dose between what is toxic and the minimal does at which there is a therapeutic effect
27
What is absorption?
The journey of a drug from where it administered to the blood plasma
28
Where are drugs absorbed?
The gut Skin Muscle CSF Lungs
29
What is distribution?
It’s presence in body fluid compartments and fat
30
What are the two forms of drugs?
Bound and unbound (free in solution)
31
Which form of drug achieves the clinically useful effect?
The unbound form
32
How is drug distribution achieved?
Through the circulatory system Highly vascular areas allow rapid distribution: the heart, liver, kidneys Less vascular areas have a slower distribution: peripheral tissues like fat and skeletal muscle
33
Do drugs distribute equally around the body?
No, some drugs are water soluble (atenolol) and stay the blood and interstitial fluid, while others are fat soluble (fentanyl) and will concentrate in fats
34
Where can drugs be metabolised?
GI tract Kidneys Lungs *Liver*
35
How are drugs metabolised by the liver?
Must enter a hepatocyte (cross the plasma membrane), liver enzymes will then make them inactive Hydrophobic drugs are more easily metabolised by the liver because of this
36
How are hydrophilic drugs metabolised?
They require specific transport proteins to enter the liver But these drugs are at least partly excreted unchanged
37
What are prodrugs?
These are modified by the liver to for the pharmacologically active molecule E.G perindopril to perindoprilat
38
What are the two phases of metabolism?
Phase 1: catabolic Phase 2: anabolic
39
Where are liver metabolising enzymes found?
Embedded in the smooth endoplasmic reticulum
40
What is the important system for drug metabolism?
The cytochrome P450 (CYP) system
41
How are drugs excreted?
Biliary excretion Faeces Respiration *Kidneys*
42
How does clearance determine the dosage of a drug?
The higher the rate of clearance the higher the dosage must be The slower the clearance rate the lower a dosage can be and still maintain a therapeutic concentration
43
What is the rate of excretion in the kidneys determined by?
Drug filtration Secretion Reabsorption
44
What part of the drug will be filtered by the glomerulus?
Only the unbound drug
45
What are two examples of drugs that even when unbound will not be filtered at the glomerulus?
Warfarin and Heparin They are too big even when unbound
46
What is secretion?
When a substance is secreted from the blood into the renal tubules
47
How are organic acids secreted?
They are transported in their anionic form against the electrochemical gradient by OAT family proteins
48
How are organic bases secreted?
They are transported in their cationic by OCT family proteins
49
Give an example of a drug that is transported by OAT
Penicillin
50
Give an example of a drug that is transported by OCT
Morphine
51
How can the therapeutic effect of a drug be prolonged
By taking agents that block tubular secretion alongside the drug
52
Does reabsorption increase or decrease the concentration of drug in the tubular lumen?
It decreases it as the drug is reabsorbed back into the bloodstream
53
What factors affect drug reabsorption?
Urine flow rate Lipid solubility Ionisation of the drug
54
Can lipid soluble drugs be excreted by the kidneys?
Not well as they cross the tubular membrane
55
Why are polar drugs excreted well?
They cannot cross the tubular membrane
56
Will ionisation if drug increase or decrease it’s reabsorption?
It will decrease it
57
What happens to drugs that are weak acids?
In alkaline urine they will become anionic and their excretion will increase
58
What happens to drugs that are weak bases?
In an acidic urine they will become cationic and their excretion will increase
59
What is ion trapping?
The charged form of the drug remains in the tubules and more it is excreted
60
How can pH of urine be changed to favour certain drug excretion?
Antacids are a good way of changing urine pH to become more alkaline and favour the excretion of acids
61
What is the Henderson-Hasselbalch equation?
PH = pKa + Log10 [A-] / [HA]
62
What is the defence of H+ concentration?
Buffers Respiratory regulation Renal regulation
63
Describe the buffer graph
pH is the y-axis Acid added is LHS Alkali added is RHS pH = pKa where the line crosses the y-axis It is a sigmoidal curve
64
Give two examples of buffers for respiratory regulation of pH
Carbonic acid Haemoglobin
65
Give the steps of respiratory regulation of pH
Decrease in pH Chemoreceptors detect this Signal to respiratory centre Increase minute volume Decrease PaCO2 (breathing out) There’ll be an increase of pH
66
Give the steps of renal regulation of pH
Increase in H+ Kidneys will: - increase H+ secretion and excretion - increase HCO3- reabsorption and decreased excretion These will decrease H+
67
At what point is reabsorption highest in the nephron?
PCT - massive reabsorption DCT - fine adjusted reabsorption and secretion Collecting duct - adjusted water reabsorption
68
What are important pH values to know?
Normal - 7.4 Acidosis - <7.35 Alkalosis - >7.45
69
What is respiratory acidosis?
The retention of carbonic acid, increased PCO2
70
What is metabolic acidosis?
Increased non-carbonic acids, decreased PCO2 and decreased HCO3-
71
What do diuretics do and how do they work?
They increase urine volume By increasing water excretion, by excreting more sodium
72
What diuretics work by causing a natriuresis?
Thiazides Loop Potassium sparing
73
Where do thiazide diuretics work?
The DCT
74
How do thiazide diuretics work?
By binding to the Cl binding site of the Na+/Cl- cotransporter Inhibiting it’s activity and increasing excretion if Na+ and Cl-
75
What sort of effect do thiazide diuretics have on BP?
They have a hypotensive effect Due to the decrease in blood volume
76
Give an example of a thiazide diuretic
Hydrochlorothiazide
77
Give two example of loop diuretics
Furosemide Bumetanide
78
How do loop diuretics work?
They inhibit the Na+/2Cl-/K+ cotransporter by binding to the Cl- site
79
What effect do loop diuretics have?
They reduce blood pressure by reducing blood volume and have a vasodilators effect
80
What is a side effect of both thiazide and loop diuretics?
The loss of potassium Na+ reabsorption and K+ secretion are linked Creates an electrochemical gradient favouring K+ secretion
81
Give examples of potassium sparing diuretics
Amiloride Triamterene Spironolactone
82
How do amiloride and triamterene work?
They block Na+ channels that normally facilitate the passive diffusion of Na+
83
How does spironolactone work?
It is an aldosterone antagonist It competes with aldosterone for its intracellular receptors
84
Rank the order of diuretics from most useful to least
Loop Thiazide Potassium sparing
85
How do osmotic diuretics work?
They reduce water reabsorption along the nephron
86
What are osmotic diuretics used to treat and why?
Emergency treatment of cerebral oedema Increased intraoccular pressure By increasing plasma osmolarity but do not enter the eye or brain allowing water to be drawn out
87
What type of hypertension are thiazide diuretics used to treat?
Uncomplicated hypertension They are better tolerated while also reducing the risk of stroke or heart attack
88
When are loop diuretics used to treat hypertension?
When dealing with resistant hypertension alongside other hypertension drugs
89
How does the distribution of cardiac output change as a result of heavy exercise?
Increased blood flow to skeletal muscle Decreased blood flow to renal and splanchnic circulations
90
Account for the increase in skeletal muscle blood flow in response to exercise
Sympathetic vasodilator fibres Changes as a result of increased metabolism: - increased H+, CO2, and temperature - low PO2
91
What are the mechanisms behind the change in blood supply to the kidneys?
Renal arteries and arterioles are innervated by sympathetic nerve fibres which elicit vasoconstriction RAS - renin-angiotensin system
92
What happens during the renin-angiotensin system?
Liver - Angiotensinogen + Kidney - Renin = Angiotensin l + Lungs - Angiotensin converting enzyme = Angiotensin ll
93
What does angiotensin ll do?
Vasoconstriction Increased aldosterone secretion Increased ADH secretion Increased thirst
94
How does the GFR change as a result of exercise?
During heavy exercise GFR is reduced There is sympathetic nervous innervation
95
How would you measure the GFR change as a result of exercise?
Clearance of inulin/creatinine
96
What is proteinuria?
Increased rate of protein excretion Usually 20-30 mins after stopping exercise - 70-80% VO2 max
97
What is proteinuria caused by?
Increased permeability of filtration membrane Reduced elastic charge Reduced reabsorption of proteins by renal tubules
98
What is haematuria?
Increased excretion of RBC Caused by mechanical trauma to the glomerulus
99
What are the benefits of increased ADH release during exercising?
Increased water reabsorption Vasoconstriction Glycogenolysis is increased - releasing more glucose
100
The renin angiotensin system and exercise
1) muscular activity - sweating 2) reduces plasma volume and blood flow to kidneys 3) this stimulates renin release from the kidneys then l converts to ll 4) angiotensin ll stimulates release of aldosterone from adrenal cortex 5) this increase Na+ and H2O reabsorption 6) plasma volume increases and urine production decreases *after several days of exercise*
101
Why is plasma lost to the interstitial fluid?
As BP increases so does capillary hydrostatic pressure As active muscle produces metabolic waste products these increase intramuscular osmotic pressure and attract fluid Sweat is formed from interstitial fluid, as it decreases in volume more plasma fluid will move into tissues
102
Why is haemoconcentration a good thing?
Increasing the concentration of electrolytes and blood proteins will increase haematocrit and increase of the Hb content per mL of blood
103
How does the plasma volume stay constant after the init drop while exercising?
ADH and Aldosterone Oxidative metabolic processes in active muscle produce water
104
Why is it the respiratory system that responds to acidosis during exercise?
The respiratory system responds in seconds, the renal system would take hours or even a day to have a significant effect There is also an increased respiratory rate
105
Give three methods that are used to increase RBC
Erythropoietin Blood doping Hypoxic tent
106
Why is advantageous to train athletes at high altitudes?
Increased Hb and haematocrit Increased VO2 max Increased time to exhaustion
107
Why would athletes consider taking diuretics?
To lose weight to meet a certain category As a masking agent - will dilute the presence of a different banned substance in their urine

Physiology (9 decks)

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