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53 Cards in this Set
- Front
- Back
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What is the normal Osmolarity for the Extracellular Fluid? |
285 mOsm/L |
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What is the normal concentration of: - Sodium - Chloride In the ECF? |
142 mOsm/L 102 mOsm/L |
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What Nitrogenous Waste products are the kidneys responsible for clearing? |
Urea, Ammonia, Creatinine, Uric Acid |
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What are the two main routes through the cells of the PCT? |
Paracellular: Between the Cells Transcellular: Through the Cells |
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Describe the structure of the proximal convoluted tubule |
Cuboidal epithelium, Brush Border, many mitochondria |
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Describe the structure of the descending limb of the loop of henle |
Squamous epithelium, few mitochondria present |
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Describe the structure of the ascending limb of the loop of henle |
Cuboidal epithelium, many mitochondria |
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Describe the structure of the Distal Convoluted Tubule |
Cuboidal epithelium, many mitochondria |
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Describe the structure of the Collecting Ducts |
Columnar Epithelium, many mitochondria |
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Where is the Macula Densor, and what does it do? |
The Macula Densor is in the wall of the Distal Convoluted Tubule as it passes close to the afferent arteriole of the Nephron. Suspected to be an Na+ Sensor |
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What percentage of the Glomerular Filtrate is reabsorbed before reaching the collecting duct? |
Approximately 99% |
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What three factors affect the rate of Filtration of a substance? |
1. Molecular Weight 2. Shape of the molecule 3. Charge of the molecule |
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Where does the energy for glomerular filtration come from? |
Hydrostatic pressure within the afferent arteriole of the nephron, imparted by the beating of the heart |
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What is the Equation for calculating the GFR of a substance? |
GFR = KS [(Pgc - Pt) - (Ogc - Ot)] |
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GFR = KS [(Pgc- Pt) - (Ogc - Ot)] What is each component of this equation? |
- K = Permeability of the Glomerular Capillary - S = Surface Area of the Capillary - Pgc = Hydrostatic pressure within capillary - Pt = Hydrostatic pressure within tubule - Ogc = Oncotic Pressure within glomerular capillary - Ot = Oncotic Pressure within tubule |
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Define Colloid Osmotic (Oncotic) Pressure |
Oncotic pressure, or colloid osmotic pressure, is a form of osmotic pressure exerted by proteins, notably albumin, in a blood vessel's plasma (blood/liquid) that usually tends to pull water into the circulatory system. |
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At what point in the Nephron does the Oncotic Pressure rise above the Hydrostatic Pressure? |
Midway through the Glomerular Capillary, and remains above for the remainder of the nephron vasculature |
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Pathology of GFR: K S |
K= Becomes increased in nephrotic syndrome, leading to GFR S= Decreased by Kidney transplant, or by blockage of a renal artery |
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Pathology of GFR: Pgc Pt |
Pgc = This is affected by blood pressure. A drop will decrease GFR, and vice versa Pt = This is affected if a blockage exists in the renal tubule, e.g.. kidney stones. Decreases GFR due to back pressure |
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Pathology of GFR: Ogc Ot |
Ogc = Decreased in Nephrotic Syndrome, liver disease and malnutrition. All lead to increased GFR Ot = Increased in nephrotic syndrome. Leads to increased GFR |
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Measurement of Glomerular Filtration Rate using Inulin/ Creatinine. What is the equation? |
GFR = Ux X V / Px Ux = Urine concentration V = Urine output Px = Plasma concentration |
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What properties of the peritubular capillary blood favour reabsorption of salt and water? |
- Low Hydrostatic Pressure - High Colloid osmotic Pressure - High Haematocrit, making the blood highly viscous and slow moving |
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What is the Equation for calculating Renal Clearance of a substance? |
RC = Ux X V / Px (Same as calculating the Glomerular Filtration Rate IF NO TUBULAR TRANSPORT TAKES PLACE) |
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What percentage of GF is reabsorbed from the PCT? |
60-70% |
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Mechanism of Transport for Na+ in PCT? |
In: Na+ H+ Counter Transport Out: Na+ K+ ATPase |
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Mechanism of Transport for Glucose in PCT? |
In: Na+ Glucose Cotransporter Out: Facilitated Diffusion |
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Mechanism of Transport for Amino Acids in PCT? |
In: Na+ AA Cotransporter Out: Facilitated Diffusion |
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Mechanism of Transport for Phosphate in PCT? |
In: Na+ Phosphate Cotransporter Out: Facilitated Diffusion |
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Mechanism of Transport of Water in PCT? |
Both: Osmotic Gradient |
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Mechanism of Transport of Potassium in PCT? |
In: ATP Dependent Out: Electrical/ concentration gradient |
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Mechanism of Transport of Protein in PCT? |
In: Endocytosis Out: Broken down into Amino acids and travels by Facilitated Diffusion |
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Describe the permeability of the loop of Henle to Salt and Water |
Descending limb: Freely permeable to both salt and water Ascending Limb: Permeable to salt but impermeable to water |
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What percentage of filtrate is reabsorbed from the Loop of Henle? |
20-25% |
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Describe transport of salt and water within the Vasa Recta |
In descending limb, salt enters and water leaves. In the ascending, it is the other way around |
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What are the two types of cell within the DCT, and what are their effects on Potassium concentration? |
- Principal Cells, secrete Potassium - Intercalated Cells, reabsorb Potassium |
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Mechanism of Transport of K+ in Principal Cells |
Taken into cell through action of Na+ K+ ATPase, excreted into tubule via facilitated diffusion |
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Mechanism of Transport of K+ in Intercalated Cells |
Taken into cell through action of H+K+ Countertransporter, and reabsorbed into blood via facilitated diffusion |
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What effect does ADH have on the Distal Nephron? |
Increased water permeability |
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What effect does Aldosterone have on the Distal Nephron? |
- Increased H+ secretion - Increased K+ secretion - Increased Na+ reabsorption - Increased Cl- reabsorption - Increased H20 reabsorption |
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Define Osmolarity |
The concentration of a solution expressed as (m)osmoles of solute per litre of solution |
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Define Osmolality |
The concentration of a solution expressed as (m)osmoles of solute per kg of solution |
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What does increasing ECF osmolarity do to cells? |
Causes water to exit the cells, leading to crenellation |
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What does decreasing ECF osmolarity do to cells? |
Causes water to enter the cells, leading to lysis |
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Describe control of water excretion by ADH |
- ADH is synthesised in the hypothalamus - Changes in ECF detected by osmoreceptor in hypothalamus - Increases ADH release from posterior pituitary gland - ADH binds to V2 receptors in Principal cells, causing an increase in aquaporins and so an increase in permeability |
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What does an increase in ADH cause? |
Causes an increased water permeability of collecting ducts, and increases water reabsorption back into the blood |
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What will increase ADH output? |
Fall in blood volume ie. haemorrhage Exercise, fright, sleep Rise in ECF osmolarity |
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What will decrease ADH output? |
Increase in blood volume Alcohol |
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What does reduced effectiveness of ADH cause? |
Diabetes Insipidus Primary = Reduced release of ADH Secondary = Reduced reaction of the nephron to ADH |
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What effects does an overproduction of ADH cause? |
- Increased blood volume - Increased blood pressure - Dliutes ECF causing hyponatraemia - Water intoxication |
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Describe the R-A-A System |
1. Decreased blood pressure 2. Increased Renin 3. Increased Angiotensinogen 4. Increased Angiotensin 1 + 2 5. Increased Aldosterone 6. Increased Na+ and h20 reabsorption 7. Increased ECF volume |
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How does potassium affect the release of aldosterone? |
1. Increased Potassium in the blood 2. Increased release of Aldosterone 3. Increased exchange of Na and K exchange in the principal cells of the distal nephrons 4. Increased excretion of potassium |
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What effect does ANP have on the R-A-A system? |
Inhibits it |
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Describe synthesis of Erythropoietin |
1. Decreased oxygen delivery to renal cortex detected by O2 receptors 2. Increased HIF 3. Increased expression of EPO gene 4. Increased Erythropoietin synthesis, leading to increased numbers of erythrocytes. |
