PHYSIOLOGY: RENAL system Flashcards by Grace Johnson

Role of kidneys

–blood filtration

–excretion of metabolic waste, endogenous and exogenous (drugs & toxins) compounds

–producing hormones (Calcitriol and erythropoietin)

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Kidneys are the primary regulators of?

fluid, blood volume and pressure
ph
electrolyte balance

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Cell types:

Intercalated cells

Principal cells

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How is blood filtered in the glomerulus?

Under pressure

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Anything that has a lower molecular mass than ……can pass through the filtration membrane

68 KDa

Proteins >68 KDa

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Forces in favour of filtration

Glomerular blood hydrostatic pressure (GBHP)

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How much is the Glomerular blood hydrostatic pressure (GBHP)?

60 mmHg

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Why is the Glomerular blood hydrostatic pressure (GBHP) high?

Due to resistance of efferent arteriole

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Forces opposing filtration

Capsular hydrostatic pressure (CHP)

Blood colloid osmotic pressure (BCOP)

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How much is the Capsular Hydrostatic pressure (CHP)?why is the Capsular Hydrostatic pressure (CHP) 15 mmHg?

15 mmHg due to accumulated fluid in the capsule

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How much is the Blood Colloid Osmotic Pressure (BCOP)?

30 mmHg

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What is the Blood Colloid Osmotic Pressure (BCOP)30 mmHg?

Due to the presence of proteins such as albumin and fibrinogen in the plasma

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Glomerular filtration rate is maintained at a relatively constant rate between MAP of?

80-180 mmHg

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Three main regulatory mechanisms of ultrafiltration

Auto regulation

Neural regulation

Hormonal regulation

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Glomerular filtration (GFR) in males?

125 ml.min -1

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GFR in female

115 ml.min -1

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Increased stretch of smooth muscle in afferent arteriole walls - reflex constriction of arteriolar smooth muscle is auto regulation is ?

Myogenic

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Renin secretion increase when arteriolar pressure falls – increase vasoconstriction in auto regulation is due to?

Intra-renal baroreceptor mechanism

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Renin secretion is inversely proportional to the amount of Na+ and Cl− entering the distal renal tubules from the loop of Henle in autoregulation is due to?

Macula dense sensor

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Both afferent and efferent arterioles are supplied by ……………….. causing vasoconstriction, effect predominates in the afferent arteriole

Sympathetic neurons

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In neural regulation, sympathetic activity is low and both afferent and efferent arterioles are dilated – autoregulation is the prevalent control mechanism

When?

At rest

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In neural regulation, both arterioles constrict to the same degree with little effect on GFR when?

During increased sympathetic activity (e.g. movement, stress)

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In neural regulation, when sympathetic activity increases: effect on afferent arteriole is greater, resulting in reduced blood flow, reduced GFR and reduced urine volume

When?

During exercise or significant MAP drop (e.g. haemorrhage )

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In hormonal regulation, reduction in BP or reduction in delivery of NaCl causes release of

Renin

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In hormonal regulation, Renin causes the conversion of circulating angiotensinogen to..........., which is then converted to ..........in the lungs

Angiotensin I Angiotensin II

In hormonal regulation, Angiotensin II is a potent vasoconstrictor and constricts both

Afferent and efferent arterioles

In hormonal regulation, Increased blood volume causes stretching of the atria. Atrial muscle releases

ANP= Atrial Natriuretic Peptide

In hormonal regulation, ANP causes ?

Relaxation of the glomerular mesangial cells

Relaxation of the the glomerular mesangial cells is caused by?

ANP

Relaxation of the glomerular mesangial cells increases what ?

Surface area of filtration - increases GFR

The amount of blood filtered per unit time (usually a minute). The amount of liquid filtered out of the blood (GFR) that gets processed by the kidneys Is called?

Renal clearance

High clearance values indicate?

Effective excretion

Low clearance values indicate

Ineffective excretion

What is used to estimate Renal clearance = GFR?

Creatinine

What is Responsible for the medullary osmotic gradient?

Juxtamedullary nephron

Most numerous nephron ?

Cortical nephron

Nephron that make short loop of Henle

Cortical nephron

Nephron that makes long loop of Henle and extends into medulla

Juxtamedullary nephron

What nephrons produce urine?

BOTH: Cortical nephron & Juxtamedullary nephron

The thick ascending loop has...... permeability to water

LOW

The descending loop has........... to ions, but is permeable to .......

LOW Permeable

Urea is reabsorbed from the loop True or false?

False | It’s not

Where the nephron is permeable to water, water follows by

Osmosis

GFR rate

105–125 mL/min of fluid that is isotonic to blood

Filtered substances in GFR

Water and all solutes present in blood (except proteins) including ions, glucose, amino acids, creatinine, uric acid

GFR is regulated by

RAS

Secretion & reabsorption takes place in ?

Proximal convoluted tubule PCT

Which tubules: –Make the largest contribution to the process –Solutes (Na+, glucose) and water reabsorbed by active and passive processes –H+ secretion to maintain blood pH –K+, NH3 and certain drugs secreted to eliminate –HCO3- reabsorption to conserve an important buffer –Water reabsorbed by osmosis

Proximal convoluted tubule

Angiotensin II simulates reabsorption of Na⁺, Cl⁻ and H2O in

Proximal tubule

Where does ONLY reabsorption take place?

Loop of Henle | Distal convoluted tubule - DCT

Where in the Loop of Henle does water continues to be reabsorbed because of the osmotic gradient in the medulla?

Descending limb

Where in the Loop of Henle is virtually impermeable to water?

Ascending Limb

In the ascending limb of the Loop of Henle Cations follow because?

Of the potential difference created between the tubule and capillary

Where does: –reabsorption of Na+ and Cl- continues. –Parathyroid hormone stimulates the reabsorption of Ca2+ by activating a Ca channel on the apical surface

Distal convoluted tubule DCT

Parathyroid hormone stimulates the reabsorption of Ca2+ by activating?

A Calcium channel on the apical surface

Reabsorption & excretion takes place in the ?

Late DCT and Collecting duct

Where do: –Principal cells reabsorb Na+ and secrete K+ - Aldosterone stimulates principal cells – stimulates Na+ reabsorption - Antidiuretic hormone - insertion of aquaporins into the apical (luminal) membranes of the principal cells - Excreting less water – increasing blood volume –Intercalated cells reabsorb K+ and HCO3- and secrete H+ –Final adjustment of solutes and water

Late DCT & Collecting duct

In Kate DCT & Collecting duct, aldosterone stimulates principal cells which stimulates?

Reabsorption of Na+

In late DCT & Collecting duct, Antidiuretic hormone (ADH) causes?

Insertion of aquaporins into the apical (luminal) membranes of the cells

Excreting less water, increases?

Blood volume

Intercalated cells in late CDT & collecting duct reabsorb.......and secrete.....?

K+ and HCO3- H+

Regulation of reabsorption and secretion hormones

Renin-Angiotensin-Aldosterone System (RAAS) Antidiuretic Hormone (ADH) Atrial Natriuretic Peptide (ANP) Parathyroid Hormone (PTH)

low blood pressure - Intra-renal baroreceptors Sympathetic innervation low Cl- levels - Macula densa cells They all stimulate?

Renin release

Renin produces

Angiotensin II

Effects of production of angiotensin II by renin

Salt conservation Water conservation Maintainance of blood pressure

Renin stimulates the release of which hormone from the adrenal cortex to complement the action of angiotensin?

Aldosterone

Which hormone is released by increase in blood volume or blood pressure?

Atrial Natriuretic peptide - ANP

ANP is secreted from the?

Cardiac atria

Tissues affected by ANP

* Hypothalamus - ADH * Adrenal Cortex - Aldosterone * Kidney - Renin release * Medulla Oblongata - (Blood pressure)

Action of ANP

Reduces Na+ and water absorption in the PCT and collecting duct.

Which hormone reduces Na+ and water absorption in the PCT and collecting duct.

ANP

What are the main organs that regulate acid-base status/ph?

Kidneys and respiratory system main organs

Key processes of kidneys to regulate ph

* match excretion of acid/base to intake, and | * produce physiological buffers to minimise changes

Urine pH can be altered from around

5 to 9

* Reabsorption of bicarbonate mainly in PCT * Free acid excretion (minimal) – proton pumps in intercalated cells enable urine to be more acidic than serum * Ammonium (major) – renal ammonia produced by glutamine metabolism in PCT. Binds with H ions to make NH4+ which is excreted in urine. * Titratable acidity (phosphate, sulphate – ie: H2PO4) They all cause

Urine oh to alter from 5 to 9

Distribution of water in the body is defined as

Fluid balance