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KCUMB Physiology - Erin > EXAM III > Flashcards

EXAM III Flashcards

1
Q

What are the components of glomerular filtration and what is the fraction of renal plasma flow that’s filtered?

A

Water

Ions

Glucose

Urea

0.2 ~ 20%

Filtration fraction = GFR/Renal plasma flow

Molecules w/ (+) charge gets filtered while (-) is repelled and stays in blood; hence why Na+ is mainly the driving force

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2
Q

What are the components that make up the glomerulus?

A

Podocytes = filtration slits

Pedicelles

Basement membrane

Fenestrated capillaries

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3
Q

What are the layers of the filtration barrier?

A

Endothelium - w/ fenestrae & (-) charges

Basement membrane - w/ collagen & proteoglycan fibers and strong (-) charges

Podocytes - with (-) charges

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4
Q

What is GFR determined by?

A

The balance of hydrostatic and colloid osmotic forces acting across capillary membrane (i.e. Starling forces)

The capillary filtration coefficient (which depends on the leakiness of the capillaries and the number and size of pores) K1 - product of permeability and filtering SA of capillaries

Albumin is slightly smaller than filtration pores but have (-) charges

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5
Q

What is the normal GFR?

A

125 ml/min = 180 L/day

(water has a filterability o = 1.0)

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6
Q

What are the active forces in GFR?

A

Pg - glomerular hydrostatic pressure

Pb - Bowman’s capsule hydrostatic pressure

πg - glomerular capillary colloid osmotic pressure

πb - Bowman’s capsule colloid osmotic pressure

GFR = K1 x (Pg - Pb - πg + πb)

GFR = K1 x Net filtration pressure

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7
Q

What is K1 and describe how this value alters GFR

A

Capillary filtration coefficient - product of permeability and filtering SA of capillaries

Hight K1 = high GFR

Low K1 = lower GFR

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8
Q

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

A

Arterial plasma colloid osmotic pressure

Filtration fraction (how much blood is actually being filtered)

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9
Q

What are factors that increase glomerular colloid osmotic pressure?

A

Increasing the filtration fraction

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10
Q

What are the variables that determine glomerular hydrostatic pressure? (3)

A

Arterial Pressure (pressure going to the glomerulus)

Increases = greater Pg –> increase GFR

Afferent arteriolar resistance

Increase –> less PG –> less GFR

Efferent arteriolar resistance

Increase –> greater PG –> slightly greater GFR

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11
Q

What are the factors that determine renal blood flow?

A

Renal artery pressure

Renal vein pressure

Total vascular resistance

Renal blood flow = renal art. p-renal vein p./total vasc. resistance

Contains a high rate of Na+ reabsorption, which is related to GFR and rate of Na+ filtered, related to active transport

Kidneys ahve 7x the blood flow of the brain but only 2x O2 consumption

Kidney O2 consumption related to high rate of active Na+ reabsorption

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12
Q

What are the effects of the sympathetic NS on kidneys?

A

Strong activation:

Constrict renal arterioles

Decrease renal blood flow and GFR

Moderate activation: little effect

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13
Q

What hormones are involved in controlling GFR consistency?

A

NEpi and Epi (adrenal medulla)

Endothelin

Angiotensin II

Endothelial-derived NO

Prostaglandin and Bradykinin

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14
Q

How does Endothelin work to help control GFR consistency and when is it released?

A

Released by damaged vascular endothelial cells of the kidneys and other tissues

May contribute to renal vasoconstriction = reduced GFR

May contribute to hemostasis

Plasma levels may increase in toxemia of pregnancy, acute renal failure, and chronic uremia

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15
Q

How does Angiotensin II work to help control GFR consistency?

A

Increases GFR by constricting efferent arterioles

Usually formed during decreased arterial pressure or volume depleting

Afferent arterioles seem to be protected against the effects of angiotensin II due to NO and prostaglandin release (vasodilators)

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16
Q

How does Nitric Oxide work to help control GFR consistency?

A

Basic levels helps maintain renal vasodilation

Dervied from endothelial cells

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17
Q

How does Prostaglandins and Bradykinin work to help control GFR consistency?

A

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

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18
Q

Define autoregulation and state its primary function

A

The relative constancy of GFR and renal blood flow

Primary function = Maintain a relatively constant GFR

Allow precise control of renal excretion of H2o & solutes

Prevent relatively large changes in GFR & renal excretion that would otherwise occur w/ changes in BP

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19
Q

If no autoregulation were to occur in the kidneys, how high can GFR and urine flow increase?

A

GFR up to 225 L/day (normal 180 L/day)

Urine flow = 46.5 L/day (normal 1.5 L/day)

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20
Q

What is the tubuloglomerular feedback mechanism for autoregulation? What are the components?

A

Afferent arteriolar feedback mechanism

Efferent arteriolar feedback mechanism

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21
Q

What is the juxtaglomerular complex and where is it?

A

Next to the glomerulus

Macula dense in distal tubule

Juxtaglomerular cells in afferent & efferent arterioles

(involved in autoregulation)

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22
Q

What is occurring during autoregulation when there is a decrease in GFR, causing a slow rate in loop of Henle? (macula densa)

A

Increase reabsorption of Na+ and Cl- ions in ascending limb

Decrease NaCl at macula densa

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23
Q

What mechanism occurs during autoregulation when there is a decrease in [NaCl], resulting in a signal from macula densa?

A

Decrease resistance to blood in afferent arterioles

Increase renin release from JG cells (major storage site of renin)

Increase in angiotensin II

Increase in efferent arteriolr resistance

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24
Q

How must a substance be reabsorbed? What 2 routes can they undergo?

A

Across tubular epithelial membrane –> renal interstitial fluid –> thru peritubular capillary membrane –> blood

via

Paracelluar (b/w cells) or Transcellular (thru cells) routes via osmosis

Paracellular transport via Ca2+/Mg2+ due to lumen being (+) charged

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25
Q

What are the 3 aquaporins that transport water?

Which one is controlled by ADH? What are their locations

A

AQP:

Aquaporin-1 = widespread including renal tubules

**Aquaporin-2 - apical membranes of collecting tubule cells; controlled by ADH

Aquaporin-3 - basolateral membranes of collecting tubule cells

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26
Q

What substance should NOT be filtered into the filtrate?

A

Proteins

also Albumin; albumin is small but carries a (-) charge

Other small substances are not freely filtered because they are partially bound to proteins

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27
Q

What are the channels that are found in nephrons?

A

ENaC channel (NaCl channel)

found in apical membrane of nephron cells

CFTR (Cl-) and K+ channels found in apical membranes of some nephron segments

Uniporters - driven by [gradient] of [substance]

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28
Q

What type of transport involves the movement of glucose transport?

A

Facilitated transport

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29
Q

What are the primary active transporters that are involved in the nephron?

A

Na+K+ATPase

H+ATPase

H+K+ATPase

Ca2++ATPase

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30
Q

What type of channels are involved in secondary active transport?

A

Na+-glucose co-transporters on brush border of proximal tubule cells

SGLT1 - reabsorbs 10% of glucose in late PCT

SGLT2 - reabsorbs 90% glucose in early PCT

Aminio acids are also involved in secondary active transport

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31
Q

List the main substances that the proximal tubule reabsorbs

A

65% of filtered Na+, Cl-, bicarbonate, K+

Gluocose

Amino acids

(great amount of [H+} in lumen via Na+ antiport transport; forming carbonic acid w/ luminal bicarbonate via carbonic anhydrase)

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32
Q

List characterstics of the thin descending segment of the LOH

A

Highly permeable to water; reabsorbs ~20% of filtered H2o

Moderately permeable to most solutes; urea and Na+

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33
Q

What are the characteristics of the thick ascending LOH?

A

Impermeable to water

Na+K+ATPase pump in basolateral membranes (driving K+ reabsorption against [gradient])

Na+,K+, 2Cl- co-transporter

K+ leak into lumen

Paracellular transport = Mg2+, Ca2+ into interstitial fluid due to K+ leak causing a (+) charge

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34
Q

Where along the nephron does the macula densa begin to form?

A

Early distal tubule

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35
Q

What are the characteristics of the distal tubule (channels)?

A

Na+Cl- co-transporter (luminal membrane)

Na+K+ATPase pump (basolateral membrane)

Impermeable to H2o and urea

Diluting segment

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36
Q

What are the basic functions of the principal cells?

A

Reabsorb Na+ and H2o from tubular lumen

Secrete K+ into tubular lumen

Na+K+ATPase pump

Primary site of K+ sparing diuretics

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37
Q

What are the functions of the alpha-intercalated cells of the late distal tubule/cortical collecting tubule?

A

Reabsorb K+ from tubular lumen

Secrete H+ into tubular lumen via H+ATPase transporter; H+ generated via carbonic anhydrase

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38
Q

Characteristics of the medullary collecting duct

A

Cuboidal epithelial cells w/ few mito

Controlled by ADH (which insert aquaporins 2)

Permeable to urea; Urea transporters

Capable of secreting H+ against a large [gradient]

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39
Q

Where is the site of action for aldosterone?

A

Principle cells of cortical collecting ducts

Increases Na+ reabsorption and K+ secretion

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40
Q

Which hormone is involved with Addison’s disease? What is the problem?

A

Aldosterone

Loss of Na+ and accumulation of K+

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41
Q

What hormone is Conn’s syndrome related to?

A

Aldosterone

Hypersecretion of aldosterone

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42
Q

Which hormone is released due to an increase in extracellular potassium and increased levels of angiotensin II?

A

Aldosterone

via adrenal cortex

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43
Q

What is the function of Angiotensin II?

A

Increases Na+ and water reabsorption and returns BP and extracellular volume toward normal

44
Q

What are the effects of angiotensin II?

A

Stimulates alderosterone secretion

Constricts efferent secretion

Directly stimulates reabsorption in proximal tubules, LOHs, distal tubules, and collecting tubules

45
Q

What are the effects of ADH?

A

Binds V2 receptors in late distal tubules, collecting tubules, and collecting ducts

Increases formation of cAMP by stimulating movement of aquaporin-2 proteins to luminal side of cell membranes

46
Q

What is the source of ANP and what response causes its release?

A

Cardiac atrial cells

In response to distention

Function: Inhibits reabsorption of Na+ and H2o

47
Q

What is the source of parathyroid hormone and what is its function?

A

Parathyroid gland

Increases Ca2+ reabsorption

48
Q

What are the 2 circulations of the lungs? List the pathway

A

High pressure; Low flow

Thoracic aorta -> bronchial arteries -> trachea, bronchial tree, adventitia, CT

Low pressure; High flow

Pulmonary artery & branches -> alveoli

pulmonary arteries 1/3 thickness or aorta = larger compliance; 7mmHg (accommodates SV output of right ventricle)

49
Q

What is the result when you have failure of left side of the heart?

A

Pressure build up in pulmonary circulation

Increases blood volume as much as 100%

Increases blood pressure

Mild systemic affect bc systemic blood volume is 9x that of the pulmonary system

50
Q

What is the physiologic shunt? What does it result in?

A

Also called venous admixture/wasted blood flow

Blood entering the arterial system without passing through ventilated areas of lung causing the PO2 of arterial blood to be less than that of alveolar PO2.

Blood from LA wall that dumps directly into LA

About 2% of blood in systemic arteries is blood that’s bypassed pulmonary capillaries

51
Q

What are the 3 zones of the lungs?

A

Zone 1 - no blood flow; local alveolar capillary pressure never rises higher than alveolar air pressure

Zone 2 - Intermittent blood flow (only during systole)

Zone 3 - Continuous blood flow

52
Q

The lung apices (apex) have which zone flow?

Zone 1

Zone 2

Zone 3

A

Zone 2; lower areas have zone 3 flow

In standing position, more blood flows to the base/bottom of lungs

53
Q

The base of the lungs have which zone flow?

Zone 1

Zone 2

Zone 3

A

Zone 3; while standing, as much as 5x more blood flows to the base of the lungs rather than the apex

54
Q

What is the normal effect of exercise on the apices of the lung?

A

Converts them from zone 2 to zone 3

55
Q

What are the agents that constrict pulmonary arteries?

A

NEAP - No Erin Acts Pretty (as me)

Epi

NEpi

Angiotensin II

Some Prostaglandins

56
Q

What occurs during heavy exercise leading to the increase in blood flow?

A

Increases # of open capillaries up to 3x

Distends all capillaries and increases flow rate up to 2x

Increases pulmonary arterial pressure

57
Q

Why doesn’t the pulmonary arterial presure rise durnig max exercise?

A

Due to an increase in opened capillaries and distended capillaries; increasing flow rate

This method converves energy of right side of the heart and prevents sig. rise in pulmonary capillary pressure

58
Q

What are the 4 things that occur during left-sided heart failure?

A

Blood begins to damn up in LA

LA pressure rises to 40-50mmHg

Increases above 8mmHg cause equal increases in pulmonary arterial pressure

Above 30mmHg = pulmonary edema likely to develop

59
Q

What are the most common causes of pulmonary edema and at what capillary pressure level does it occur?

A

Left-sided hearth failure or mitral valve disease

Damage to pulmonary blood capillary membrane via infections or breathing noxious substances

Lethal pulmonary edema can happen = minutes/hours

> 25 mmHg

60
Q

How does hypoxia effect blood flow in the pulmonary system?

A

Increases pressure in the pulmonary artery

Possibly due to release of a prostaglandin

61
Q

What are the results of bronchial obstruction in relation to blood flow? What are the causes?

A

Constriction of vessels supplying the poorly ventilated alveoli

Due locally to low alveolar PO2 effect on the vessels

pH drop due to CO2 accumulation

pH drop causes vasoconstriction in pulmonary vessels

pH drop produces vasodilation in other tissues

62
Q

What is the result of reduction of blood flow to a portion of the lung?

A

Lowers alveolar PCO2

Resulting in a constriction of the bronchi supplying that particular portion of the lung

63
Q

What are the major components in the air and what are their relative concentrations?

A

N = 78%

O2 = 20.95%

Ar = 0.93%

CO2 = 0.03%

64
Q

Define Dalton’s Law

A

The total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases

65
Q

Define Boyle’s Gas Law

A

For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional

P1V1 = P2V2

66
Q

Define Henry’s Gas Law

A

At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid

PP = [dissolved gas]/sol. coefficient

O2 solubility = 0.024

CO2 solubility = 0.57

67
Q

T/F

CO2 is more soluble in water than O2; explain this concept

A

True

Due to this, CO2 exerts a partial pressure (for a given []) that is less than 1/20th that of oxygen

68
Q

What are the factors that control oxygen concentration in the alveoli?

A

Rate of absorption of oxyen into the blood

Rate of new oxygen entry into the lungs (alveolar ventilation)

69
Q

What is normal GFR?

A

125 ml/min ~ 180 L/day

70
Q

What is the amount of daily normal fluid excretion?

A

1.5 L/day

71
Q

What would GFR be without autoregulation? How high would this increase urine flow?

A

225 L/day

Urine flow up to 46.5 L/day

72
Q

What percentage of filtered Na+, bicarbonate, K+, glucose, and aa is reabsorbed in the PCT?

A

65%

73
Q

How is Na+ reabsorbed in the first and second 1/2 of the PCT?

A

First 1/2 = Co-transporter; w/ glucose and amino acids

Second 1/2 = via Cl- ions

74
Q

What is the H+ and Bicarbonate ion association in the PCT? What is occurring?

A

Na+ and H+ are transported via antiporter mechanism

[H+] is increasing in the tubular lumen and combines with luminal bicarbonate to yield water and CO2

H+ + HCO3- –> H2CO3 –> CO2 + H2O

CO2 diffuses into tubular cell to combine with water and eventually forming H+ and new bicarbonate which is excreted

75
Q

What are the characteristics of the early distal tubule?

A

Na+Cl- ATPase symporter into the tubular cell; apical membrane

Basolateral membrane: Na+/K+ ATPase

(similar to thick ascending LOH)

76
Q

What are the events that are happening in the late distal tubule? Transporter types, cell types, etc.

A

Intercalated Cells (H2o impermeable)

Apical - H+/K+ ATPase (K+ reabsorbed, H+ excreted), H+ ATP pump (excreted)

H+ joins NH3 to form NH4, H+ is coming from bicarbonate CA system

Basolateral - Na/K ATPase, K+ leak

Principal Cells = ADH action, K+ sparing diuretics (H2o impermeable)

Apical - Aquaporins, Na+, K+ leaks

Basolateral - Na/K ATPase

77
Q

T/F

Collecting Duct is permeable to urea

Collecting duct contains many mitochondira

A

TRUE - permeable to urea

FALSE - contains few mitochondira

78
Q

What are the hydrostatic and osmotic forces involved in lung capillary fluid exchange? How is excess fluid carried away?

A

Outward Forces:

Pulmonary capillary pressure

Pulmonary Interstitial fluid colloid osmotic pressure

Pulmonary Interstitial fluid hydrostatic pressure

Inward Forces:

Pulmonary capillary osmotic pressure

Excess fluid is carried away via pul. lymphatics

79
Q

At what pressures do the lungs tend to collapse?

A

When pressure becomes more positive

i.e. greater than -7 mmHg

Can occur during pleural effusion = edema of pleural cavity

80
Q

Explain why alveolar ventilation cannot increase PO2 above 149 mmHg under normal conditions

A

Due to part pressure of oxygen in the atm

FRC of lungs = 2300ml

350 ml of new air is brought into alveoli w/ each normal inspiration and the same amount is expired

Multiple breaths are required to exchange most of alveolar air

Only 1/7 is replaced by new atm air

81
Q

What are the factors that control CO2 concentration in the alveoli?

A

Rate of CO2 excretion

Alveolar PCO2 increases in direct proportion to rate of excretion

Alveolar Ventilation

Alveolar PCO2 decreases in inverse proportion to alveolar ventilation

Graphs: Lines = rates of excretion

82
Q

What are the components of the respiratory membrane?

A

Basement membrane of the capillary

Basement membrane of the epithelium of the alveoli

(Interstitial space sometimes present)

83
Q

What does the Va/Q ratio refer to?

A

Ventilation-Perfusion Ratio

The ratio of alveolar ventilation and blood flow

Normal = 0.8

Normal Va/Q when both pulmonary and ventilation factors are normal (pulmonary = 5 L/min; ventilation = 4 L/min)

84
Q

What is the normal Va/Q ratio?

A

0.8

85
Q

What happens to the Va/Q ratio when there is an airway obstruction?

A

Va = 0; Perfusion still occurs

Gas levels equilibrate throughout system

Blood gas composition remains unchanged

86
Q

What happens to the Va/Q ratio when there is a vascular obstruction? What are the alveoli partial pressure values?

A

i.e. pulmonary embolism

Ventilation still occurs; No perfusion; Va = infiniti

No blood contact creating a physiologic shunt

PO2 = 149 mmHg; PCO2 = 0 mmHg

87
Q

Define Shunted Blood

A

Blood that does not become oxygenated due to having a Va/Q ratio below normal.

88
Q

Define Physiological Shunt

A

Wasted Blood Flow

Due to blood entering arterial system that does not pass through ventilated areas, causing PO2 of arterial blood to be less than alveolar PO2

89
Q

Define Physiological Dead Space

A

The sum of wasted ventilation plus anatomic dead space

Wasted ventilation

Due to having a greater amount of ventilation with low perfusion

90
Q

How much water can be excreted by the kidneys per day when there is a large excess of water in the body?

A

Forms dilute urine

20 L/day w/ 50 mOsm/L

Kidney reabsorbs solutes and NOT water

Ascending LOH reabsorbs Na+, K+, Cl-

Late DCT reabsorbs Cl-

91
Q

What is required by the kidney tubules for the formation of concentrated urine?

A

Requires ADH

and high osmolarity of renal medullary interstitial that creates an established gradient

92
Q

What is the max urine concentration that the kidneys can produce? What’s required by the kidney tubules for this to occur?

A

1200-1400 mOsm/L

ADH must be present so that you can keep the water and make urine concentrated

High osmolarity or the renal medullary interstitial tubule which establishes an osmotic gradient that’s necessary for water reabsorption to occur

93
Q

How much volume of solute must be excreted per day and why must this occur?

A

~600 mOsm

To rid of waste products of metabolism and ions that are ingested

94
Q

Where in the kidney tubule are most of the filtered electrolytes reabsorbed?

A

PCT

95
Q

What is the role of the osmoreceptor-ADH feedback mechanism? What is happening during this mechanism?

A

Controls extracellular fluid [Na+] and osmolarity

An increase in [Extracellular-fluid osmolarity] causes a shrinkage of osmoreceptor cells in anterior hypothalamus which creates an Action potential which releases ADH = increases water permeability in distal nephron segments

96
Q

Where specifically is ADH formed?

A

Magnocellular neurons in the

Supraoptic nuclei

Paraventricular nuclei

Osmoreceptor cells

97
Q

What is the normal [extracellular K+ ion]? What is the clinical significance of excess extracellular K+?

A

normal = 4.2 mEq/L

An increase can can cardiac arrhythmias (3-4 mEq/L)

An even greater increase can cause cardiac arrest or fibrillation

98
Q

What is the overall affect of aldosterone on potassium excretion?

A

Levels increase potassium secretion

99
Q

What factors stimulate principal cells to secrete K+?

A

Increase in extracellular K+ levels

Aldosterone effects

100
Q

What effects do insulin and catecholamines have on extracellular K+ levels?

A

Insulin - stimulates K+ uptake/reab. which increases intracellular K+ and decreases extracellular K+

This in turn causes Aldosterone to increase which will increase K+ secretion to reduce the intracellular levels of K+ (via increased function of Na+/K+ ATPase pumps and luminal membrane permeability)

Catecholamines i.e. Epi (beta-adrenergic) = stimulates cellular K+ uptake

Beta-adrenergic blockers = hyperkalemia (extracellularly)

101
Q

Which buffer system is most important in extracellular space? Intracellularly?

A

Bicarbonate buffer system = weak acid and bicarbonate salt

Intracellularly = Phosphate buffer system = major flow in renal tubular flow

102
Q

Define buffer

A

A substance that can reversibly bind H+ that contains a weak acid

103
Q

What organ primarily regulates the bicarbonate buffer system?

A

Kidneys

Excretes HCO3-

104
Q

What is the primary method for removing nonvolatile acids?

A

Renal excretion

105
Q

What must happen before filtered bicarbonate is reabsorbed?

A

Reacts with secreted H+ ions to form carbonic acid

106
Q

What is the lower limit of pH that can be achieved in normal kidneys?

A

4.5

KCUMB Physiology - Erin (11 decks)

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