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Human Physiology 1 -- Zach H. > Lecture #15: Micturition and Glomerular Filtration > Flashcards

Lecture #15: Micturition and Glomerular Filtration Flashcards

1
Q

What are the 2 different conduction paths of sensory signals from bladder stretch receptors?

A

1) conducted to sacral region of spinal cord via pelvic nerves.
2) conducted reflexively back to bladder via parasympathetic nerves.

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2
Q

As the bladder continues to fill, micturition reflexes occur more often and are more powerful. Once the micturition reflex is powerful enough, it causes a second reflex. What is the second reflex and what does it do?

A

The second reflex passes through the pudendal nerves to inhibit the external sphincter.

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3
Q

The nephrons function to get rid of waste materials. What are the 4 waste products secreted?

A

Urea
Creatinine
Uric Acid
Bilirubin

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4
Q

How does the nephrons function to regulate arterial pressure long term?

A

By excreting variable amounts of sodium ion and water.

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5
Q

How does nephrons function to regulate arterial pressure short term?

A

Secrete hormones and vasoactive factors such as renin.

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6
Q

What do all of the many functions of nephrons regulate within the body?

A

> Get rid of waste materials
- urea, creatinine, uric acid, bilirubin

> Regulate water and electrolyte balance

> Regulate body fluid osmolarity

> Regulate arterial pressure

 - Long Term
      * excrete variable amounts of sodium ion and water
 - Short Term 
      * Secrete hormones and vasoactive factors such as renin

> Regulate acid-base balance

 - excrete acids and regulate body fluid buffer stores 
 - eliminate sulfuric and phosphoric acids

> Secretion, Metabolism, and Excretion of Hormones

 - erythropoietin 
 - active form of vitamin D

> Gluconeogenesis

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7
Q

What is the formula to calculate urinary excretion rate?

A

UER =

Filtration Rate - Reabsorption Rate + Secretion Rate

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8
Q

What is the first step in urine formation?

A

Filtration

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9
Q

What components make up the glomerular filtrate?

A

Water

Ions

Glucose

Urea

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10
Q

What formula is used to calculate filtration fraction?

A

Filtration Fraction = GFR/Renal Plasma Flow

  • fraction of renal plasma flow that is filtered = 0.2
    (i. e., 20% of plasma flowing through kidney is filtered).
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11
Q

True or False:

The concentration of most substances except for proteins is the same in the filtrate and the plasma.

A

TRUE

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12
Q

What forms the slit filtration barrier?

A

Podocytes

  • with negative charges
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13
Q

True or False:

The endothelium and basement membrane layers of the filtration barrier have a negative charge and the podocytes of the filtration barrier have a neutral charge.

A

False - The endothelium, basement membrane, and podocytes of the filtration barrier all have a negative charge.

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14
Q

Albumin is smaller in size then the slit pores made by the podocytes, but why does it not freely pass through?

A

Because of the negative charge.

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15
Q

In which portion of the filtration barrier are fenestre found?

A

Endothelium

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16
Q

Does the endothelium, basement membrane, or podocytes of the filtration barrier have the strongest negative charge?

A

Basement Membrane

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17
Q

What determines the glomerular filtration rate (GFR)?

A

> the balance of hydrostatic and colloid osmotic forces acting across the capillary membrane

> capillary filtration coefficient
- product of permeability and filtering surface area of capillaries

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18
Q

What are 2 diseases that can lower glomerular capillary filtration coefficient?

A

> Chronic un-controlled hypertension

> Diabetes mellitus

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19
Q

What is the definition of minimal change nephropathy?

A

When the basement membrane losses negative charges.

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20
Q

What is hydronephrosis?

A

Distension and Dilation of Renal Pelvis and Calyces.

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21
Q

True or False:

Reflex contractions relax spontaneously when the bladder is only partially filled.

A

True

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22
Q

How do you calculate glomerular filtration rate (GFR)?

A

GFR = (K1) x (Net Filtration Pressure)

*Net Filtration Pressure is the Starling Forces

(Pg - Pb - PIEg + PIEb)

(60 - 18 - 32 + 0) = 10 mmHg

K1 = GFR/Net filtration pressure
= 125 ml/min / 10 mmHg = 12.5 mmHg

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23
Q

What effect does increase the K1 have on GFR?

A

It raises GFR

24
Q

What effect does lowering K1 have on the GFR?

A

It reduces GFR

25
Q

True of False:

Some low-molecular weight substances are not freely filtered because they are partially bound to proteins.

A

True

26
Q

What is the K1?

A

K1 = capillary filtration coefficient

*product of permeability and filtering surface area of capillaries.

27
Q

What are 2 factors that influence glomerular capillary colloid osmotic pressure?

A

1) arterial plasma colloid osmotic pressure

2) filtration fraction

28
Q

What is a factor that increase glomerular colloid osmotic pressure?

A

Increasing Filtration Fraction

29
Q

What effect does increasing arterial pressure have on glomerular hydrostatic pressure and thus, GFR?

A

An increase in arterial pressure will increase the Pg (glomerular hydrostatic pressure), and thus, will increase the GFR.

30
Q

What effect does increasing the afferent arteriolar resistance have on glomerular hydrostatic pressure and thus, GFR?

A

Increasing the afferent arteriolar resistance would decrease the Pg (glomerular hydrostatic pressure) thus, decreasing the GFR.

31
Q

What effect would increasing the efferent arteriolar resistance have on the glomerular hydrostatic pressure and thus, the GFR?

A

Increasing the efferent arteriolar resistance would result in an increase in Pg (glomerular hydrostatic pressure) thus, slightly increasing the GFR.

32
Q

How do you calculate Renal Blood Flow?

A

RBF =

(renal artery pressure - renal vein pressure)/total vascular resist.

33
Q

What accounts for most of the oxygen consumed by the kidneys?

A

Much of the oxygen consumed by the kidneys is related to the high rate of active sodium reabsorption.

34
Q

Does strong activation of renal sympathetic nerves increase or decrease GFR and renal blood flow?

A

Decreases renal blood flow and GFR.

35
Q

Does strong activation of renal sympathetic nerves constrict or dilate renal arterioles?

A

Constricts renal arterioles.

36
Q

True or False:

All blood vessels of the kidneys are richly innervated by sympathetic system.

A

True

37
Q

True of False:

Moderate sympathetic activation has a large effect on arteriole constriction.

A

False - moderate sympathetic activation has little effect.

38
Q

What are the two mechanisms that control GFR consistency?

A

1) Sympathetic System
2) Hormones:
> norepinephrine and epinephrine (from adrenal medulla)
- parallel the sympathetic system
> endothelin
> angiotensin II
> endothelial-derived NO
> prostaglandins and bradykinin

39
Q

What is the role of endothelin (hormone) in controlling GFR?

A

Endothelin is released by damaged vascular endothelial cells of the kidneys and other tissues.
> it may contribute to renal vasoconstriction leading to reduced GFR
> it may contribute to hemostasis when a blood vessel is severed
> plasma levels increase in certain disease states associated with vascular injury
- toxemia of pregnancy
- acute renal failure
- chronic uremia

40
Q

What 3 diseases increase plasma levels of endothelin?

A

toxemia of pregnancy

acute renal failure

chronic uremia

41
Q

Why do afferent arterioles seem to be protected against the effects of angiotensin II?

A

Because afferent arterioles release prostaglandins and nitric oxide, which are vasodilators. Thus, they counter act the effects of angiotensin II by releasing vasodilators.

42
Q

What effect does angiotensin II have on efferent arterioles? Also, what does this do to GFR, increase or decrease?

A

Angiotensin II constricts the efferent arterioles, thus increasing the GFR.

43
Q

Why is angiotensin II usually released to act upon the efferent arterioles?

A

Formed usually in situations associated with decreased arterial pressure or volume depletion.

44
Q

Where is nitric oxide (NO) derived from and what does it do to renal arterioles?

A

Nitric Oxide is derived from endothelial cells and helps maintain renal vasodilation

45
Q

What role do prostaglandins and bradykinin play on renal arterioles?

A

Vasodilators that may offset effects of sympathetic and angiotensin II vasoconstrictor effects (especially on afferent arterioles).

46
Q

What does autoregulation refer to and what does it function to maintain and control within the kidney?

A

Autoregulation refers to the relative constancy of GFR and renal blood flow.

Primary Function is to:

 - maintain a relatively constant GFR
 - allow precise control of renal excretion of water and solutes 
 - prevent relatively large changes in GFR and renal excretion that would otherwise occur with changes in blood pressure
47
Q

True or False:

Autoregulation prevents relatively large changes in GFR and renal excretion that would otherwise occur with changes in blood pressure.

A

TRUE

48
Q

True or False:

Autoregulation allows precise control of renal excretion of water and solutes.

A

TRUE

49
Q

What is the normal GFR per day?

A

180 L/day

  • tubular reabsorption = 178.5 L/day
  • normal daily fluid excretion = 1.5 L/day
50
Q

What would happen without autoregulation of the kidneys?

A

Without autoregulation, a slight increase in blood pressure could increase GFR up to 225 L/day.

** This would increase urine flow to 46.5 L/day.

51
Q

In what structure is the macula densa located?

A

Distal Tubule

52
Q

In which arterioles are juxtaglomerular cells found?

A

Juxtaglomerular cells are in afferent and efferent arterioles.

53
Q

What are the two components of the tubuloglomerular feedback mechanism for autoregulation?

A

1) afferent arteriolar feedback mechanism

2) efferent arteriolar feedback mechanism

54
Q

What happens if autoregulation decreases GFR?

A

Decrease GFR = slow flow rate in loop of Henle =
>increase reabsorption of sodium and chloride ions in the ascending limb
>decrease in sodium chloride at macula densa

55
Q

If there is a decrease in NaCl, what will the resulting signal from the macula densa result in?

A

> decrease resistance to blood in afferent arterioles
increase renin release from JG cells
increase angiotensin II
increase efferent arteriolar resistance

56
Q

Look over slides 44 and 45 in the lecture 15 handout.

A

Figure 27-11 in the book

Human Physiology 1 -- Zach H. (12 decks)

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