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Physiology > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

what is required for fluid to flow through a tube

A

pressure gradient

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2
Q

what is pressure in the cardiovascular system produced by

A

the heart

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3
Q

what is fluid flow through a tube influenced by

A

resistance

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4
Q

what is flow proportional to

A

1/R (inversely proportional to resistance)
deltaP/R

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5
Q

what is delta P and what is it directly proportional to

A

pressure gradient
proportional to flow

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6
Q

what is the relationship between resistance and radius

A

resistance depends on radius
R (directly proportional to) 1/radius^4

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7
Q

in the cardiovascular system, changes in resistance result from what two things

A

vasoconstriction
vasodilation

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8
Q

what happens to pressure as fluid travels along a tube? why?

A

pressure decreases due to friction with the wall of the tube

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9
Q

does each side of the heart function independently

A

yes, each side functions as an independent pump

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10
Q

what serves as a pressure reservoir in the heart

A

elastic arteries

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11
Q

what do arterioles have a high proportion of

A

muscle

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12
Q

what is the site of variable resistance

A

arterioles

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13
Q

what happens at capillaries? why?

A

site of exchange because they are very thin

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14
Q

what part of the cardiovascular system serves as a volume reservoir? why?

A

systemic veins because they have high compliance and are not very elastic

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15
Q

what is allocation of blood flow to body structures determined by

A

changes in arteriolar resistance

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16
Q

what are three changes that can affect arteriolar resistance

A

arranged in parallel
controlled individually
smooth muscle changes

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17
Q

what are two types of smooth muscle changes that can happen in arterioles

A

vasoconstriction and vasodilation

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18
Q

what two things does vasoconstriction result in

A

decrease in pressure downstream
increase in pressure upstream

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19
Q

where is the velocity of blood flow the lowest

A

in capillaries

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20
Q

what does velocity of blood flow depend on

A

total cross-sectional area of vessels

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21
Q

do capillaries have a small or large cross-sectional area

A

large
(lowest velocity)

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22
Q

what does the low velocity in capillaries allow

A

time for diffusion

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23
Q

what are the three mechanisms of exchange at capillaries

A

diffusion (simple, facilitated)
vesicular transport
bulk flow (water and solutes)

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24
Q

what type of exchange uses diffusion

A

exchange of small solutes

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25
Q

what type of exchange uses vesicular transport

A

larger solutes and proteins

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26
Q

what is transcytosis

A

combination of endocytosis, vesicular transport, and exocytosis

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27
Q

what type of exchange uses bulk flow

A

water and solutes

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28
Q

what are the two possibilities with bulk flow

A

filtration
absorption

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29
Q

what is filtration

A

from plasma –> interstitial fluid

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30
Q

what is absorption

A

from interstitial fluid –> plasma

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31
Q

what three things are bulk flow determined by

A

hydrostatic pressure (PH)
colloid osmotic pressure (pi)
net filtration pressure (NFP)

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32
Q

where is the hydrostatic pressure lowest

A

at venous end due to friction

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33
Q

what is the osmotic pressure a result of

A

proteins restricted to plasma

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34
Q

is colloid osmotic pressure the same as total osmotic pressure? what is the difference?

A

no
colloid osmotic pressure does not vary across capillary bed

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35
Q

what is the net filtration pressure (NFP)

A

hydrostatic pressure (PH) - colloid osmotic pressure (pi)

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36
Q

if the NFP is greater than 0 is there net filtration or net absorption

A

net filtration

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37
Q

if the NFP is less than 0 is there net filtration or net absorption

A

net absorption

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38
Q

where does net filtration occur

A

arterial end

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39
Q

where does net absorption occur

A

venous end

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40
Q

is the filtration at the arterial end or the absorption at the venous end bigger

A

filtration at arterial end usually exceeds absorption at the venous end

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41
Q

how many L of fluid is lost from plasma per day

A

~3L

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42
Q

what is the lymphatic system made up of

A

vessels and nodes

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43
Q

what are the four functions of the lymphatic system

A
  1. returns excess interstitial fluid (as lymph) to the blood
  2. returns any filtered protein to the blood
  3. filters out pathogens (at lymph nodes)
  4. absorbs fats in small intestine
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44
Q

what is the driving pressure of blood pressure

A

pressure created in ventricles, transferred to arteries

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45
Q

as blood travels through arteries –> capillaries –> veins, what happens to the pressure

A

pressure decreases

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46
Q

what kind of arteries serve as a pressure reservoir

A

elastic arteries

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47
Q

how do elastic arteries serve as a pressure reservoir (3)

A
  1. stretch during systole
  2. elastic recoil maintains driving pressure during diastole
  3. backward flow during diastole prevented by semilunar valves
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48
Q

what are the two measures of blood pressure

A
  1. systolic (sBP)
  2. diastolic (dBP)
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49
Q

when is systolic pressure measured

A

during ventricular systole

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50
Q

when is diastolic pressure measured

A

during ventricular diastole

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51
Q

what is the pulse pressure (PP)

A

sBP - dBP

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52
Q

what is the mean arterial pressure (MAP)

A

dBP + PP/3

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53
Q

what does the MAP reflect

A

driving pressure for blood flow to tissues

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54
Q

what indicates whether there is enough pressure to perfuse all organs

A

mean arterial pressure (MAP)

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55
Q

what is the MAP equal to

A

MAP = CO x TPR

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56
Q

what is TPR

A

total peripheral resistance = resistance to flow, due to arterioles

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57
Q

what is the driving pressure

A

MAP

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58
Q

what does MAP depend on

A

flow in vs. flow out

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59
Q

what are the 4 factors that can influence MAP

A
  1. cardiac output
  2. diameter of arterioles
  3. blood volume
  4. diameter of veins
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60
Q

what happens to MAP with increased cardiac output

A

MAP increases

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61
Q

what happens to MAP when the diameter of arterioles decreases

A

the TPR (arteriolar resistance increases) so the MAP increases

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62
Q

what are most systemic arterioles innervated by

A

sympathetic nervous system neurons

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63
Q

what so SNS neurons release

A

norepinephrine

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64
Q

what happens to the systemic arterioles when NE is released

A

vasoconstriction

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65
Q

how does NE cause vasoconstriction (3)

A
  1. alpha adrenergic receptors
  2. tonic control
  3. maintain vascular tone
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66
Q

what happens with epinephrine release

A

vasoconstriction due to epi acting on alpha-adrenergic receptors

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67
Q

what happens to MAP when blood volume increases

A

MAP increases

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68
Q

does the cardiovascular system respond to changes in blood volume quickly or slowly

A

quickly

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69
Q

do the kidneys respond to changes in blood volume quickly or slowly

A

slowly

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70
Q

what kind of innervation of smooth muscle causes vasoconstriction

A

sympathetic innervation of smooth muscle using alpha-adrenergic receptors

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71
Q

what happens to MAP if blood is redistributed to the arteries using smooth muscle

A

increased MAP

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72
Q

what is the chain of events causing increased MAP starting at increased venous return (4 steps total)

A
  1. increased venous return
  2. increased EDV (end diastolic volume)
  3. increased SV (stroke volume)
  4. increased MAP
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73
Q

what region of the brain controls the cardiovascular system

A

cardiovascular control center (CVCC) in medulla oblongata

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74
Q

what does the CVCC in medulla control specifically

A

blood pressure and distribution of blood to tissues

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75
Q

what is the baroreceptor reflex

A

primary reflex pathway for homeostatic control of MAP

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76
Q

what do baroreceptors respond to

A

stretch-sensitive
respond to pressure

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77
Q

where are baroreceptors located

A

in carotid arteries and aorta

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78
Q

is the baroreceptor reflex slow or quick

A

rapid response

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79
Q

does the baroreceptor reflex ever turn off

A

no it is functioning all the time

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80
Q

what kind of output does the CVCC control to specific regions of the body

A

sympathetic to regulate blood distribution

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81
Q

what happens to blood flow during a fight or flight response

A

increased blood flow

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82
Q

what happens when NE and epi bind to alpha adrenergic receptors

A

widespread vasoconstriction

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83
Q

what happens when NE and epi bind to beta2 adrenergic receptors

A

vasodilation in skeletal muscle, heart, and liver

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84
Q

what is active hyperemia

A

local increase in blood flow due to an increase in metabolic activity

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85
Q

why is active hyperemia important

A

strategy for tissues to regulate their own blood supply

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86
Q

what (3) paracrines can cause local vasodilation

A

nitric oxide
adenosine
histamine

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87
Q

what happens with increased nitric oxide

A

decreased O2

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88
Q

what happens with increased adenosine

A

increased CO2

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89
Q

what happens with increased histamine

A

increased H+

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90
Q

what is cellular respiration

A

intracellular process using O2 to generate ATP + CO2 + H2O

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91
Q

what is external respiration

A

movement of gases between atmosphere and cells

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92
Q

what are the four types of external respiration

A

ventilation
gas exchange (pulmonary circuit)
gas transport
gas exchange (systemic circuit)

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93
Q

what is ventilation

A

exchange of air between atmosphere and lung alveoli

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94
Q

where does gas exchange in the pulmonary circuit occur

A

between lung alveoli and blood

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95
Q

where does gas transport occur

A

in the blood

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96
Q

where does gas exchange in the systemic circuit occur

A

between blood and tissues

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97
Q

how is pH regulated by the respiratory system

A

via retention or elimination of CO2

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98
Q

what gas is obtained for cells and what gas is removed

A

O2 to obtained
CO2 is removed

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99
Q

what is alveolar ventilation

A

Va
volume of fresh air that reaches alveoli per minute

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100
Q

what happens to Va with hyperventilation

A

increases

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101
Q

what happens to Va with hypoventilation

A

decreases

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102
Q

what two things can happen if ventilation is inadequate

A

hypoxia: insufficient O2 availability to cells
hypercapnia: elevated CO2 levels

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103
Q

what does the gas exchange at lungs and tissues require

A

a gradient in partial pressure

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104
Q

what does the partial pressure gradient apply to

A

each gas independently (ex. O2 will move from high PO2 to low PO2)

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105
Q

what is the partial pressure of a gas

A

the pressure of a single gas
Pgas = Patm x fractional concentration of gas in the atmosphere

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106
Q

what is Daltons Law

A

total pressure exerted by mixture of gases is equal to the sum of pressures exerted by individual gases
Patm = PN2 + PO2 + PCO2 (+ PH2O (water vapor))

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107
Q

what percentage of N2, O2, and CO2 are in the atmosphere

A

N2: 78%
O2: 21%
CO2: 0.04%

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108
Q

at sea level, what is the Patm

A

760 mm Hg

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109
Q

what changes at different altitudes

A

Pgas and Patm

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110
Q

what is constant at different altitudes

A

the percentage of gas in the atmosphere (fractional concentration)

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111
Q

in typical alveoli, what are the partial pressures of O2 and CO2

A

PO2: 100 mm Hg
PCO2: 40 mm Hg

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112
Q

what happens to PO2 and PCO2 with hypoventilation

A

PO2 decreases
PCO2 increases

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113
Q

what happens to PO2 and PCO2 with hyperventilation

A

PO2 increases
PCO2 decreases

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114
Q

what are the partial pressures of O2 and CO2 in typical peripheral tissues

A

PO2: 40 mm Hg
PCO2: 46 mmHg

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115
Q

what are three factors that can increase alveolar gas exchange (diffusion)

A

increase partial pressure gradient
increase surface area available for gas exchange
decrease diffusion distance (from air to/from blood)

116
Q

what are three factors that can decrease alveolar gas exchange

A

decreased surface area
decreased partial pressure gradient
increased diffusion distance

117
Q

what are two things that can decrease the partial pressure gradient

A

high altitude
hypoventilation

118
Q

what is Henrys Law

A

movement of gas from air to liquid is proportional to solubility and pressure gradient

119
Q

is O2 or CO2 more easily dissolved in plasma

A

CO2 is more soluble in water
very little O2 can be carried dissolved in plasma

120
Q

how is most O2 found in blood

A

bound to hemoglobin in red blood cells

121
Q

what is the law of mass action

A

higher plasma PO2 = more binding
lower plasma PO2 = less binding = release of O2

122
Q

what two things does the amount of O2 bound to Hb depend on

A

% saturation of Hb due to PO2
number of O2 binding sites (# RBC and Hb content per RBC)

123
Q

what does the oxyhemoglobin saturation dissociation curve show

A

the % of available binding sites occupied
(determined by plasma PO2)

124
Q

what is the normal % of available binding sites occupied in the lungs

A

98%

125
Q

what shape is the oxyhemoglobin saturation curve

A

sigmoidal
(important for delivering O2 to active tissues)

126
Q

what happens to the oxyhemoglobin saturation dissociation curve if PO2 decreases

A

flat part - not much effect
steep part - larger release of O2 from Hb

127
Q

what happens when the oxyhemoglobin curve shifts to the right

A

increases O2 delivery to cells - lower affinity
(occurs in active or hypoxic tissues)

128
Q

what causes the oxyhemoglobin curve to shift to the right

A

higher PCO2
lower pH
higher temperature
higher 2,3 BPG

129
Q

when is 2,3 BPG produced

A

during chronic hypoxia (ex high altitude)

130
Q

what are the three ways CO2 is transported in blood? which is most %?

A
  1. dissolved in plasma
  2. bound to hemoglobin
  3. converted to bicarbonate ion
    (70% is converted to bicarbonate ion)
131
Q

what does the bicarbonate ion buffer

A

metabolic acids

132
Q

what is the bicarbonate buffering reaction

A

CO2 + H2O -><- H2CO3 -><- H+ + HCO3-

133
Q

what is hypercapnia and what does it cause

A

high CO2
–> right shift of curve –> high H+ –> acidosis

134
Q

what is hypocapnia and what does it cause

A

low CO2
–> left shift of curve –> low H+ –> alkalosis

135
Q

what happens to CO2 in peripheral tissues

A
  1. CO2 enters RBC
  2. CO2 is converted to HCO3- and H+
  3. hemoglobin buffers H+ (H+ +Hb –> HbH)
  4. HCO3- enters plasma (leaves RBC) via antiporter and chloride shift

(emphasis on CO2 entering plasma at the tissues)

136
Q

what happens to CO2 in the lungs

A
  1. HCO3- leaves plasma and enters RBC via antiporter
  2. HbH –> Hb + H+
  3. HCO3- + H+ –> CO2
  4. CO2 leaves the cell, dissolves in plasma, and is transferred into the lungs to be released back into the atmosphere
137
Q

what kind of muscle does ventilation use and what is it controlled by

A

skeletal muscle controlled by the CNA via somatic motor neurons
(does not require a conscious effort)

138
Q

what is the rhythmic pattern of ventilation generated by

A

the medulla oblongata

139
Q

what are the pacemaker neurons of ventilation

A

pre-Botzinger complex

140
Q

what are the inspiratory muscles? expiratory muscles?

A

inspiratory: dorsal respiratory group
expiratory: ventral respiratory group

141
Q

what do the pontine respiratory groups do

A

smooth out rhythm

142
Q

what four things are the output signals of ventilation modified by

A

voluntary input (cerebral cortex)
limbic system (emotions)
fever
chemoreceptors

143
Q

what do chemoreceptors monitor

A

CO2, O2, and pH levels

144
Q

where are the central chemoreceptors located and what do they sense

A

located in medulla oblongata and sense changes in PCO2

145
Q

what are changes in PCO2 detected as

A

pH of the CSF (cerebrospinal fluid)

146
Q

where are the peripheral chemoreceptors located and what do they sense

A

located in carotid arteries and aorta
sense changes in PCO2, pH, and PO2 in blood (plasma)

147
Q

what is ventilation (rate and tidal volume) controlled by

A

pCO2 and pH

148
Q

what does PO2 need to fall under before affecting ventilation

A

60 mmHg

149
Q

where does air flow in relation to pressure

A

from high to low pressure

150
Q

what is Boyles Law

A

P1V1=P2V2

151
Q

what is pressure inversely related to

A

volume of the container

152
Q

what happens to the diaphragm and lung tissue during inspiration

A

diaphragm contracts (flattens)
lung tissue is stretched (requires fluid bond between lung and chest wall)
- air moves into lungs

153
Q

what happens to the diaphragm and lung tissue during expiration

A

diaphragm relaxes (unflattens)
elastic recoil of lung tissue
- air moves out of lungs

154
Q

what happens to the thoracic volume, alveolar volume, and alveolar pressure with inspiration

A

thoracic volume: increases
alveolar volume: increases
alveolar pressure: decreases

155
Q

what happens to the thoracic volume, alveolar volume, and alveolar pressure with expiration

A

thoracic volume: decreases
alveolar volume: decreases
alveolar pressure: increases

156
Q

what determines airway resistance

A

airway diameter

157
Q

what happens to smooth muscle with bronchoconstriction and bronchodilation

A

bronchoconstriction: narrowing
bronchodilation: widening

158
Q

what are two factors that can cause dilation of bronchioles

A

high CO2 in expired air
sympathoadrenal pathway -> epi -> beta2 adrenergic receptors -> dilation

159
Q

what are two factors that can cause constriction of bronchioles

A

histamine from mast cells
parasympathoadrenal pathway -> ACh -> mAChR -> constriction

160
Q

what does compliance of the lungs mean

A

ability of lungs to stretch

161
Q

what does elastance of the lungs mean

A

ability to recoil after stretch

162
Q

what does low compliance cause in relation to ventilation

A

difficulty inspiring

163
Q

what does low elastance cause in relation to ventilation

A

difficulty expiring due to decreased recoil

164
Q

what happens to resistance when the airway is narrowed

A

increased resistance and difficulty expiring due to the collapse of the bronchioles

165
Q

what is tidal volume

A

VT
volume of air that moves during a single inspiration or expiration

166
Q

what is inspiratory reserve volume

A

IRV
additional volume you can inspire about VT

167
Q

what is expiratory reserve volume

A

ERV
amount of air that can be forcefully exhaled after end of a normal expiration

168
Q

what is residual volume

A

RV
volume of air remaining after maximal exhalation

169
Q

what is vital capacity

A

VC
VT + IRV + ERV

170
Q

what is total lung capacity

A

TLC
VC + RV

171
Q

what is ventilation rate

A

VR
breaths / minute

172
Q

what is minute (total pulmonary) ventilation (VE)

A

volume of air inhaled or exhaled per minute (mL/min)
VR x VT
(breaths/min) x (mL/breath)

173
Q

what are the normal (resting) values for VR VT and VE

A

VR: 12 breaths/min
VT: 500 mL/breath
VE: 6 L/min

174
Q

what is the equation for alveolar ventilation

A

VA = VR x (VT - VD)
VD= anatomic dead space

175
Q

what is the main function of the kidneys

A

filter the blood to:
retain vital substances
eliminate wastes
maintain homeostasis of water and ions (by retaining/eliminating as needed)

176
Q

how do the kidneys play a role in hormonal regulation of blood pressure

A

by the renin-angiotension-aldostrone system (RAAS)

177
Q

what does the urinary bladder do

A

storage and release (micturition) of urine

178
Q

what are the four processes that occur in the kidneys

A
  1. filtration
  2. reabsorption
  3. secretion
  4. excretion
179
Q

where does filtration occur

A

Bowmans capsule

180
Q

what happens in the proximal tubule of the nephron

A

reabsorption and secretion of many specific substances

181
Q

what happens in the loop of henle

A

reabsorption
countercurrent multiplier

182
Q

what makes up the distal nephron and what function does it perform

A

distal tubule and collecting duct
reabsorption and secretion; final control of water, ions, pH

183
Q

what is the pathway of blood supply in the renal portal system

A

afferent arteriole –> glomerulus –> efferent arteriole –> peritubular capillaries

184
Q

what is filtration

A

passive leakage of plasma

185
Q

what does filtration produce

A

filtrate = filtered plasma that is nearly isosmotic with plasma with no proteins or blood cells

186
Q

what makes up the renal corpuscle

A

glomerulus and bowmans capsule

187
Q

what is the filtration fraction

A

percentage of plasma passing through glomerulus that is filtered = 20%

188
Q

what is the glomerular filtration rate

A

GFR
volume filtered/time
GFR= net filtration pressure (NFP) x filtration coefficient

189
Q

what three filtration barriers must substances leaving the plasma pass through

A

fenestrated capillary endothelium
basement membrane
podocytes of epithelium of Bowmans capsule (filtration slits/gaps)

190
Q

what two factors increase the filtration coefficient

A

increased surface area of glomerular capillaries
increased permeability of filtration slits

191
Q

what three things does the net filtration pressure in the renal corpuscle depend on

A
  1. glomerular hydrostatic pressure (PH)
  2. colloid osmotic pressure (pi)
  3. capsule fluid pressure (Pfluid)
192
Q

what is the glomerular hydrostatic pressure

A

blood pressure

193
Q

what is the colloid osmotic pressure due to and what does it oppose

A

due to plasma proteins
opposes filtration

194
Q

what is the capsule fluid pressure due to and what does it oppose

A

due to bowmans capsule
opposes filtration

195
Q

what is the equation for net filtration pressure and what is the normal value

A

PH - pi - Pfluid
10mmHg

196
Q

what two local controls by the kidney cause GFR to be fairly constant over a range of MAPs

A
  1. autoregulation by myogenic response
  2. autoregulation by juxtaglomular response
197
Q

in MAP increases (GFR increases) what happens to the afferent arteriole

A

smooth muscle of the afferent arteriole stretches

198
Q

what are the 4 steps that lead to vasoconstriction of the afferent arteriole after MAP increases

A
  1. stretch-sensitive ion channels open
  2. muscle cells depolarize
  3. Ca2+ channels open
  4. vascular smooth muscle contracts
  5. vasoconstriction
199
Q

what three things happen after the afferent arteriole is constricted

A
  1. decreased blood flow through afferent arteriole
  2. decreased NFP through renal corpuscle
  3. decreased GFR (GFR=NFP x filtration coefficient)
200
Q

what is the juxtaglomerular apparatus

A

specialized region where distal tubule and afferent arteriole meet for regulation of GFR and MAP

201
Q

where is the macula densa located

A

wall of tubule

202
Q

where are the granular cells located

A

in wall of arteriole

203
Q

if GFR increases, what happens to the fluid flow through tubules

A

increased GFR = faster flow

204
Q

what happens when macula densa cells detect a higher NaCl concentration flowing through the tubules

A
  1. release paracrine signals
  2. vasoconstriction of afferent arteriole
  3. decreased GFR
205
Q

at rest, what kind of autoregulation dominates

A

renal autoregulation

206
Q

under sympathetic input (ex. intense exercise) what happens to the afferent arteriole

A

increased epi, NR, and angiotension II constrict afferent arteriole to help maintain increased MAP

207
Q

what happens to urine production with decreased GFR

A

decreased urine production to maintain blood volume

208
Q

what percentage of filtrate is reabsorbed and where

A

99% in proximal tubule

209
Q

what is the pathway from filtrate to blood

A

filtrate –> interstitial fluid –> blood

210
Q

how is Na+ reabsorbed

A

active transport
1.diffused passively from filtrate into tubule cell via carriers
2. actively transported into interstitial fluid to be reabsorbed
(low sodium concentration inside the cell allows for the passive diffusion)

211
Q

what is the primary driving force for most reabsorption and why

A

Na+
-anions follow Na+ to even out charges
- water follows solutes by osmosis to even out concentration on both sides of cell

212
Q

what happens if there is a high concentration of other solutes in the filtrate

A

they are reabsorbed passively using diffusion (using their concentration gradient)

213
Q

what is Na+-linked (secondary active) transport used for

A

reabsorption of other substances (AA, glucose, etc) driven by Na+ concentration gradient

214
Q

how is glucose reabsorbed

A

using the SGLT transporter to move glucose against its concentration gradient (Na+ moving down gradient)

215
Q

what is the transport maximum

A

Tm
transport rate at saturation

216
Q

what is the renal threshold

A

plasma concentration at which saturation occurs

217
Q

what is the filtration of glucose proportional to

A

plasma concentration
-doesnt saturate because it just goes through the filtration slits

218
Q

what is reabsorption of glucose proportional to

A

plasma concentration unless the Tm is reached (saturation)

219
Q

what is glucose secretion

A

zero unless the renal threshold is reached

220
Q

what is secretion

A

active transport from blood to filtrate

221
Q

how is secretion selective

A

via transporters

222
Q

what two main things is secretion important for

A

K+ and H+ homeostasis in the collecting duct
organic anion and cation elimination in proximal tubule

223
Q

what happens to the secretion of a molecule when molecules are competing for carriers

A

secretion decreases

224
Q

what is excretion

A

removal from body

225
Q

what is filtrate called when it leaves the collecting duct

A

urine
-no change in composition

226
Q

what is excretion equal to

A

excretion = filtration - reabsorption + secretion

227
Q

what is renal handling of a substance

A

an accounting of how much reabsorption and/or secretion of that substance occurs

228
Q

what is the clearance of a substance

A

volume of plasma cleared of that substance per minute

229
Q

what happens to the substance if it is equal to GFR

A

the substance is neither reabsorbed nor secreted

230
Q

what happens to the substance if it is less than GFR

A

net reabsorption of the substance

231
Q

what happens to the substance if it is greater than GFR

A

net secretion of the substance

232
Q

what type of control is micturition (urination) under

A

both spinal reflex and voluntary control

233
Q

what is tonically active at rest in the bladder

A

somatic motor neurons to external sphincter tonically active

234
Q

what is passively closed at rest in the bladder

A

internal sphincter (smooth muscle)

235
Q

what two things activate micturition reflex in the bladder

A

stretch receptors activate
1. parasympathetic neurons cause contraction of smooth muscle in bladder wall which mechanically opens internal sphincter
2. somatic motor neurons to external sphincter are inhibited (inhibits contraction so sphincter opens)

236
Q

what provides the voluntary inhibition of micturition

A

cerebral cortex: excitatory input to somatic motor neurons overrides reflex inhibition (makes sphincter contract)

237
Q

what three things need to be regulated in order to survive (in regards to the urinary system)

A

ECF osmolarity
ECF volume
concentrations of electrolytes (ion species)

238
Q

what is the most important ECF solute and why

A

Na+
primary determinant of ECF volume

239
Q

what is Na+ controlled by (3)

A

aldosterone
ANP
angiotensin II

240
Q

what is the main determinant of resting Vm and why

A

K+ because dysregulation affects excitable tissues

241
Q

what is K+ controlled by

A

aldosterone

242
Q

can ECF volume and osmolarity change independently

A

yes

243
Q

what is blood osmolarity maintained at

A

300 mOsM

244
Q

what does dysregulation of blood osmolarity cause

A

hypo/hypertonic environment –> cells swell or shrink
hypo=swell
hyper=shrink

245
Q

what is blood osmolarity controlled by

A

vasopressin and thirst

246
Q

what does dysregulation of ECF volume alter

A

MAP
hypertension (high BP)
hypotension (low BP)

247
Q

what is ECF volume controlled by

A

regulating Na+

248
Q

what three response systems integrate fluid and electrolyte balance by responding to changes in blood volume

A

cardiovascular responses
renal/kidney responses
behavioral responses

249
Q

what are the characteristics of the cardiovascular responses to changes in blood volume

A

fast-neural control
cant be sustained
cant add/remove fluid

250
Q

what are the characteristics of the renal/kidney responses to changes in blood volume

A

slow-mainly endocrine control
can remove fluid

251
Q

what are the characteristics of the behavioral responses to changes in blood volume

A

slow
can add fluid (thirst/drinking)

252
Q

how is ECF osmolarity maintained (in regards to urine)

A

high ECF osmolarity increases thirst intake to vary urine concentration

253
Q

what is the osmolarity of the filtrate entering the collecting duct

A

dilute (~100mOsM)

254
Q

what is the collecting duct surrounded by

A

medullary interstitial fluid with osmotic gradient
superficial ~300 mOsM
deep ~ 1200 mOsM

255
Q

what is the purpose of the medullary interstitial fluid with the osmotic gradient

A

reabsorbs water from the collecting duct via osmosis

256
Q

what happens to filtrate traveling through the medulla

A

it becomes progressively more concentrated and becomes urine

257
Q

what is the amount of reabsorption in the collecting duct regulated by

A

altering the permeability

258
Q

what does the loop of henle function as

A

countercurrent multiplier that produces interstitial osmotic gradient

259
Q

what does the thick portion of the ascending limb reabsorb

A

actively reabsorbs Na+ and Cl- into interstitial fluid
not permeable to water

260
Q

what does the thick portion of the ascending limb increase the osmolarity of

A

interstitial fluid

261
Q

what does the thick portion of the ascending limb decrease osmolarity of

A

filtrate as it ascends toward the cortex

262
Q

what is the filtrate initially isosmotic with

A

blood (~300)

263
Q

what reabsorption happens in the descending limb

A

passive reabsorption of water (osmosis) into interstitial fluid
impermeable to solutes

264
Q

what does the descending limb decrease osmolarity of

A

interstitial fluid

265
Q

what does the descending limb increase osmolarity of

A

filtrate progressively as it descends into medulla

266
Q

what does the interstitial osmotic gradient result from

A

interaction between ascending and descending limbs

267
Q

what is the vasa recta

A

peritubular capillaries associated with loop of henle

268
Q

what are the functions of the vasa recta

A

removes water and solutes reabsorbed by the loop of henle
has similar osmotic gradient

269
Q

what is vasopressin and where is it secreted from

A

antidiuretic hormone (helps retain water)
secreted from posterior pituitary

270
Q

how does vasopressin increase the collecting ducts permeability to water

A

causes collecting duct cells to insert aquaporin channels in membrane

271
Q

when is concentrated urine (up to 1200) produced and how

A

if ECF osmolarity too high
1. increased vasopressin
2. increased permeability

272
Q

when is dilute urine (to 50) produced and how

A

if ECF osmolarity too low
1. decreased vasopressin
2. decreased permeability

273
Q

what four stimuli causes vasopressin secretion

A

increased ECF osmolarity
decreased blood pressure
decreased blood volume (less arterial stretch)
angiotensin II

274
Q

what is aldosterone secreted by and what does it act on

A

secreted by: adrenal cortex
acts on: principal (P) cells of distal nephron

275
Q

what does aldosterone do to Na+ and K+

A

causes increased Na+ reabsorption and increased K+ secretion

276
Q

what two things is aldosterone stimulated by

A

low blood pressure (via RAAS pathway)
increased K+

277
Q

what is the renin-angiotensin-aldosterone system (RAAS)

A

endocrine pathway promoting increased MAP

278
Q

what is angiotensinogen

A

inactive plasma protein

279
Q

what is renin

A

enzyme secreted by granular cells

280
Q

what is renin secreted in response to

A

decreased MAP

281
Q

what are the three ways the body can sense a decrease in MAP

A
  1. sensed directly by granular cells
  2. decreased MAP means decreased GFR which means decreased NaCl which is detected by macula densa and paracrine signals are released
  3. sensed by the cardiovascular control center which increases sympathetic input
282
Q

what does renin do to angiotensinogen

A

convert it to angiotensin I (ANG I)

283
Q

what converts angiotensin I to angiotensin II

A

angiotensin converting enzyme (ACE)

284
Q

how does ANG II raise MAP (6 ways)

A
  1. increase aldosterone secretion –> increased Na+ reabsorption –> increased ECF volume
  2. increased vasopressin secretion –> increased H2O reabsorption –> increased ECF volume
  3. increased thirst –> increased ECF volume
  4. CVCC increases HR, SV, TPR
  5. increase vasoconstriction
  6. increased Na+ absorption directly
285
Q

where is the atrial natriuretic peptide secreted from and why

A

the atria in response to increased stretch of the atria (indicates increased blood volume)

286
Q

how does ANP (atrial natriuretic peptide) decreased blood volume and MAP (4 ways)

A
  1. decrease vasopressin, renin, and aldosterone
  2. CCVC decreases HR, SV, TPR
  3. vasodilate afferent arteriole directly to increase GFR
  4. decrease Na+ reabsorption directly

Physiology (5 decks)

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