Renal Physiology Flashcards

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1
Q

Describe the general functions of the urinary system.

A

1)Fluid, electrolyte, and pH balance:
-Adjusting blood volume and blood pressure
(By regulating the amount of water that gets excreted vs. reabsorbed)
2)-Regulation of several blood components:
(Plasma conc. of Na+, K+, Cl-, other ions Blood pH)
3) Removing drugs, toxins, and nitrogenous wastes (urea)from the blood/body
-Breakdown of proteins/ amino acids produces ammonia, which can be toxic! So, we convert ammonia to urea – a “safer” nitrogenous waste product.
4) produce and/or activate various hormones

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2
Q

Describe the process of glomerular filtration, including where it occurs, how it occurs, and why it occurs.

A
  • Happens in the glomerulus (nephron)
  • Blood flows down afferent arteriole to the glomerulus
  • Filtrate/ fluid (waste) escapes and is collected in bowman’s capsule/ glomerular capsule
  • Only small particles can get through the 3 membranes (endothelial cells, basement membrane, tubular cells)
  • Proteins are too large and too negative to get past the basement membrane
  • H20, glucose, amino acids, Na+ are all small enough to get through
  • Everything that cannot be filtrated leaves the glomerulus through the efferent arteriole
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3
Q

Describe the relationship between osmotic pressure, and how it affects glomerular filtration.

A

Pulls water out of filtrate into plasma through osmosis which decreases GFR

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4
Q

Describe how increasing or decreasing the diameter of the afferent arterioles can change the glomerular hydrostatic pressure (and how this will affect filtration)

A
  • ↓ diameter of afferent arteriole will decrease GHP decrease GFR
  • ↑ diameter of afferent arteriole will increase GHP
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5
Q

Describe how increasing or decreasing the diameter of the efferent arterioles can change the glomerular hydrostatic pressure (and how this will affect filtration)

A

↓ diameter of efferent arteriole will increase GHP

↑ diameter of efferent arteriole will decrease GHP

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6
Q

Define “GFR” (what does it stand for, and what does it mean)

A

Glomerular filtration rate (GFR) = amount of

filtrate produced by the kidneys each minute

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7
Q

How is GFR controller by autoregulation

A

Accomplished by changing diameters afferent arterioles, efferent arterioles, and glomerular capillaries

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8
Q

How is GFR controller by the autonomic nervous system.

A

Sympathetic nerve fibers cause vasoconstriction of afferent arterioles of glomerulus, decrease GFR (override the local effects, in case of an “emergency”)

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9
Q

Describe the reabsorption that occurs in the proximal convoluted tubule (which solutes are normally reabsorbed, a general description of the transport mechanisms involved, and the significance of this).

A

1)Reabsorption of organic nutrients m
-99% of glucose, amino acids, etc.
-Facilitated diffusion and cotransport (Na+ dependent
secondary active transport)
-*transport maximum

2)Active reabsorption of ions
-Cotransport, countertransport
(Part of the process is active transport, to establish a gradient so that the other steps can occur by diffusion )

3) Reabsorption of water
- By osmosis (driven by high osmotic pressure and low
hydrostatic pressure of peritubular capillaries)
-Active transport of solutes creates concentration gradient

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10
Q

Describe the functions of the loop of Henle

A

1)Loop of Henle reabsorbs:
~50% of the water
~66% of the Na+ and Cl- ions
2)The filtrate at the end of the PCT is still isotonic to ECF…
needs to get concentrated! Therefore The loop of Henle generates a salinity gradient (to help with
concentration of urine, in the collecting ducts!) =Countercurrent multiplication!

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11
Q

Describe how the thin descending limb has a different function than the thick ascending limb, and how this relates to countercurrent multiplication

A

-Between the thin descending limb and thick ascending limb
A)Thin descending limb:
-Loses water by osmosis (lots of
water channels, always open)
-Conc. in tubule increases as you descend
-This speeds up the active transport in the thick ascending limb…!

B)Thick ascending limb:

  • Pumps out Na+, K+, & Cl- (but no water loss!)
  • Maintains conc. gradient in tissue fluid surrounding the tubule **
  • Conc. in tubule decreases as you ascend
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12
Q

Describe the general functions of the distal convoluted tubule

A

Final adjustments” in composition of filtrate
occur here
-Some more Na+ and some Ca2+ reabsorption
-Plus Secretion (Of: K+, H+, some hormones, foreign chemicals,drugs, etc… )

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13
Q

Describe the general functions of the collecting duct

A

-Some more reabsorption of water and solutes
(Under control of aldosterone and ADH and Depends on osmotic gradient (between the CD and the surrounding tissue fluid)
- Some more secretion can also occur
-Can exchange H+ and bicarbonate ions to regulate pH of fluid around the collecting duct

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14
Q

A)Describe the micturition reflex,

B)and the voluntary control that we (normally) have to “override” this reflex.

A

A)Stretching of the bladder stimulates contraction of the bladder, leads to opening of internal urethral sphincter

B)Voluntary control:
-Can “override” the micturition reflex, letting you control
when to open the external urethral sphincter
-Can also change the bladder to allow you to empty the
bladder even if it isn’t full yet

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15
Q
  • Describe how blood pressure can be regulated by hormones : erythropoietin
A
  • increases blood pressure

- decreases blood volume

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16
Q

What is the effect of ADH on the kidney, and how does this affect renal function and ultimately blood volume and blood pressure?

A

hormone regulating ability of kidney to form dilute /concentrated urine.
ADH (antidiuretic hormone), causes water reabsorption to increase by increasing the permeability of the linings of the distal convoluted tubules and collecting ducts. This occurs in response to decreasing blood volume and pressure or decreasing concentrations of water in the blood.

17
Q

Describe the relationship between net filtration pressure, and how it affects glomerular filtration

A

It is the pressure that helps to move filtrate from the glomerulus into Bowman’s capsule. It is a combination of glomerular hydrostatic pressure. Capsular hydrostatic pressure and osmotic colloid pressure. Glomerular hydrostatic pressure helps in out flow of filtrate into the bowman’s capsule and the two other pressure opposes it, so they are moving the filtrate in opposite direction back into glomerulus but since the net filtration pressure is the subtraction of all the forces it is always positive and in favor of glomerular hydrostatic pressure.

18
Q

Describe the relationship between hydrostatic pressure,and how it affects glomerular filtration

A

The hydrostatic pressure in the glomerular capsule opposes the hydrostatic pressure in the glomerulus. If the glomerular capsule pressure pressure is too great, as with an obstruction filtration will decrease.

19
Q
  • Describe how blood pressure can be regulated by hormones : natriuretic peptides,
A

decreases peripheral resistance therefore vasodilation which

  • increases blood volume
  • decreases blood pressure
20
Q
  • Describe how blood pressure can be regulated by hormones :antidiuretic hormone(ADH)
A
  • A peptide hormone that:
  • increases peripheral resistance causing vasoconstriction (increasing blood pressure)
  • increases blood volume by decreasing water loss
21
Q
  • Describe how blood pressure can be regulated by hormones : aldosterone
A
  • increases blood pressure

- by increasing blood volume(decreases water and salt loss)

22
Q
  • Describe how blood pressure can be regulated by hormones : angiotensin
A
  • A peptide hormone that causes
  • increases peripheral resistance therefore causing vasoconstriction and a subsequent increase in blood pressure and decrease in blood volume
23
Q

How is GFR controller by hormones especially the hormones of the RAAS and natriuretic peptides

A

(1) decline in BP at the glomerulus as the result of a decrease in blood volume
(2) decline in the osmotic concentration of the tubular fluid at the macula densa.