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Physiology Exam III Material > Micturition and glomerular filtration > Flashcards

Micturition and glomerular filtration Flashcards

1
Q

Superimposed micturition contractions begin to appear as

A

The bladder fills

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2
Q

During the micturition reflex sensory signals form bladder stretch receptors

A

Conduct sensory signals to sacral region of spinal cord via pelvic nerves
- conducted sensory signal then go reflexively back to bladder via the parasympathetic nerves

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3
Q

Once initiated, the micturition is

A

self-regenerative

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4
Q

Reflex contractions relax spontaneously when

A

bladder is only partially filled

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5
Q

The self-regenerative micturition reflex fatigues after

A

a few seconds and the bladder relaxes

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6
Q

As the bladder continues to fill, micturition reflexes occur

A

more often and are more powerful

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7
Q

When the micturition reflex is powerful enough it

A

causes a second reflex: passing through the pudenal nerves to inhibit the external sphincter

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8
Q

Higher bring center (in ____) keep micturition partially inhibited expect when micturition is desired

A

pons

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9
Q

When it is time to urinate, the cortical centers can facilitate the sacral micturition centers to help initiate a micturition reflex and at the same time inhibit ______ so that urination can occur

A

The external urinary sphincter

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10
Q

The sympathetics to the bladder originate from what spinal region

A

L2

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11
Q

The pelvic nerves to the bladder are connected with the spinal cord through the sacral plexus, mainly connecting with cord segments

A

S2 and S3

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12
Q

Explain the 3 steps in the single cycle of the micturition reflex

A
  1. ) Progressive and rapid increase of pressure
  2. ) a period of sustained pressure
  3. ) return of the pressure to the basal tone of the bladder
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13
Q

Functions of nephrons

A
  • Get rid of waste material (urea, creatinine, uric acid, bilirubin)
  • Regulate water and electrolyte balance
  • Regulate body fluid osmolarity
  • Regulate arterial pressure
  • Regulate acid-base balance
  • Secretion, metabolism, and exertion of hormones
  • Gluconeogenesis
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14
Q

What is the long term way that nephrons regulate arterial pressure

A

excrete variable amounts of sodium and water

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15
Q

What is the short term way that nephrons regulate arterial pressure

A

secrete hormones and vasoactive factors such as renin

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16
Q

How do Nephrons regulate acid-base balance

A
  • Excrete acids and regulate body fluid buffer stores

- Eliminate sulfuric and phosphoric acids (from protein metabolism)

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17
Q

What do nephrons secrete

A

Erythropoietin and Active form of Vitamin D

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18
Q

What are the three processes that determine the rates at which different substances are excreted in the urine

A
  • Filtration
  • Reabsorption
  • Secretion
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19
Q

Formula for urinary excretion rate

A

urinary excretion rate=Filtration rate - Reabsorption Rate + Secretion Rate

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20
Q

What is the first step in urine formation

A

Filtration

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21
Q

What are the components of the glomerular filtrate

A

Water
Ions
Glucose
Urea

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22
Q

Filtration rate=

A

GFR/Renal Plasma Flow

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23
Q

Urinary excretion rate=

A

Urinary excretion rate= Filtration rate - Reabsorption rate + Secretion Rate

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24
Q

Concentration for most substances except for ____ is the same in the filtrate and the plasma

A

Proteins

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25
Q

Some low-molecular weight substances are not freely filtered through the glomerulus because

A

they are partially bound to proteins

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26
Q

Endothelium of the glomerulus

A

Fenestrated with negative charge

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27
Q

Layers of the filtration barrier

A

Endothelium, Basement membrane, Podocytes

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28
Q

What is the basement membrane of the glomerulus (filtration barrier) composed of

A

collagen and proteoglycan fibers and strong negative charges

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29
Q

Do the Podocytes of the filtration barrier have a negative charge

A

yes

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30
Q

Glomerular filtration rate (GFR) is determined by

A
  • Balance of hydrostatic and colloid osmotic forces acting across capillary membrane
  • Capillary filtration coefficient
    • Product of permeability and filtering surface area of capillaries (K1)
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31
Q

What is the GFR per min

A

125 mL/min

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32
Q

What is the GFR per day

A

180 L/day

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33
Q

Water has a filterability in the glomerulus of

A

1.0

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34
Q

Why does albumin not go through the glomerulus

A

Albumin molecule (6nm) are slightly smaller than the filtration pores (8nm) but have a negative charges

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35
Q

What are some of the diseases that lower glomerular capillary filtration coefficient

A

-Chronic uncontrolled hypertension and diabetes mellitus

36
Q

Define minimal change nephropathy

A

Loss of negative charges on the basement membrane

37
Q

Define hydronephrosis

A

Distension and dilation of renal pelvis and calyces

38
Q

GFR=

A

K1 x net filtration pressure

39
Q

net filtration pressure is equal to

A

glomerular hydrostatic pressure (60mm Hg) - Bowman’s capsule hydrostatic pressure (18mm Hg) - glomerular capillary colloid osmotic pressure (32mm Hg) + colloid osmotic pressure of bowman’s capsule (0 mm Hg)

40
Q

What is K1

A
  • capillary filtration coefficient

- product of permeability and filtering surface area of capillaries

41
Q

increase in K1 has what effect on GFR

42
Q

K1=

A

GFR/Net filtration pressure

43
Q

What are two factors that influence glomerular capillary colloid osmotic pressure

A
  • Arterial plasma colloid osmotic pressure

- Filtration fraction

44
Q

Factors that increase glomerular colloid osmotic pressure

A

Increasing filtration fraction

45
Q

Variables that determine glomerular hydrostatic pressure

A
  • Arterial pressure
  • Afferent Arteriolar resistance
  • Efferent arteriolar resistance
46
Q

increase in Arterial pressure has what effect on Glomerular hydrostatic pressure and GFR

A

Increase in glomerular hydrostatic pressure

increase in GFR

47
Q

increase in Afferent arteriolar resistance has what effect on Glomerular hydrostatic pressure and GFR

A
  • Decrease in glomerular hydrostatic pressure

- Decrease in GFR

48
Q

increase in Efferent arteriolar pressure has what effect on Glomerular hydrostatic pressure and GFR

A
  • increases in glomerular hydrostatic pressure

- slight increase in GFR

49
Q

What is the fraction of renal plasma that is filtered

A

0.2 (about 20%)

50
Q

The kidneys have ____x the blood flow of the brain but only ____ the oxygen consumption of the brain

51
Q

Most of the oxygen consumed by the kidneys is related to

A

the high rate of active sodium reabsorption

52
Q

Tubular sodium reabsorption is closely related to _____ and ____

A

GFR and rate of sodium filtered

53
Q

Renal blood flow equal

A

Renal blood flow= (Renal artery pressure - Renal vein pressure) / (total vascular resistance)

54
Q

all blood vessels of the kidney are richly innervated by

A

The Sympathetic system

55
Q

Strong activation of renal sympathetic nerves has what effects

A
  • Constricts renal arterioles

- Decreases renal blood flow and GFR

56
Q

Moderate sympathetic activation has _____ effect

57
Q

Hormones that control GFR consistency

A
  • Norepinephrine and epinephrine (from the adrenal medulla)
  • Endothelin
  • Angiotensin II
  • Endothelial-derived NO
  • Prostaglandins and Bradykinin
58
Q

Mechanisms controlling GFR consistency include

A
  • Sympathetic system

- Hormones

59
Q

What is released by damaged vascular endothelial cells of the kidneys and other tissues

A

Endothelin

60
Q

What is endothelin

A

-Hormone released by damaged vascular endothelial cells of the kidneys and other tissues

61
Q

Endothelia may contribute to _______ leading to ____ in the kidneys

A

-Renal vasoconstriction leading to reduced GFR

62
Q

Endothelin may contribute to ____ when a blood vessel is severed

A

hemostasis

63
Q

When do Endothelin plasma levels increase in

A

in certain disease states associated with vascular injury:

  - Toxemia of pregnancy
  - Acute renal failure 
  - Chronic Uremia
64
Q

Effects of Angiotensin II on GFR

A
  • Constricts efferent arterioles

- this leads to an increase in GFR

65
Q

How do afferent arterioles protect themselves agains angiotensin II

A
  • They release prostaglandins and Nitric oxide which are vasodilators
66
Q

When is angiotensin II formed

A

in situations associated with decreased arterial pressure or volume depletion

67
Q

Nitric oxide is derived from

A

endothelial cells

68
Q

Basic levels of nitric oxide help maintain renal

A

vasodilation

69
Q

Prostaglandins and bradykinin are _______ that may offset effects of ______ and ______ vasoconstrictor effects (especially on afferent arterioles)

A

Vasodilators, sympathetic and angiotensin II

70
Q

_____ refers to the relative constancy of GFR and renal blood flow

A

Autoregulation

71
Q

What is the primary function of autoregulation in the kidneys

A
  • 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
72
Q

What is Normal GFR/Day

73
Q

What is normal Tubular Reabsorption/Day

A

178.5 L/Day

74
Q

What is normal daily fluid excretion

75
Q

Without auto regulation, a slight increase in blood pressure could increase GFR to

76
Q

An increase of GFR to 225 L/Day would increase urine flow to

A

46.5 L/Day

77
Q

A filterability of 0.75 means what

A

That a substance is filtered only 75% as rapidly as water

78
Q

Tubuloglomerular feedback mechanism for autoregulation has two components what are they

A
  • An afferent arteriolar feedback mechanism

- An efferent arteriolar feedback mechanism

79
Q

Components of the juxtaglomerular complex

A
  • Macula densa in distal tubule

- Juxtaglomerular cells in the walls of afferent and efferent arterioles

80
Q

Decrease GFR has what effect on the flow rate in the loop of hence and concentration of Sodium chloride at macula densa

A

Decrease in GFR leads to slow flow rate in loop of Henle, thus leading to increased reabsorption of sodium and chloride ions in ascending limb, this means decreased levels of sodium chloride at macula densa

81
Q

A decrease in _____ results in a signal from the macula densa

82
Q

What signals does the macula densa send out when it has decreased levels of NaCl

A
  • to decrease resistance to blood in afferent arterioles
  • increase renin release from juxtaglomerular cells, thus leading to an increase in angiotensin II, thus leading to increased efferent arteriolar resistance and increase GFR
83
Q

What cells are a major storage site of renin

A

Juxtaglomerular cells

84
Q

what is the definition of renal clearance of a substance

A

volume of plasma that is completely cleared of the substance by the kidneys per unit of time.

85
Q

The clearance rate of a substance is equal to

A

( urine concentration X Urine flow rate) / (Plasma Concentration)

Physiology Exam III Material (13 decks)

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