Exam 3 Flashcards
1
Q
what is required for fluid to flow through a tube
A
pressure gradient
2
Q
what is pressure in the cardiovascular system produced by
A
the heart
3
Q
what is fluid flow through a tube influenced by
A
resistance
4
Q
what is flow proportional to
A
1/R (inversely proportional to resistance)
deltaP/R
5
Q
what is delta P and what is it directly proportional to
A
pressure gradient
proportional to flow
6
Q
what is the relationship between resistance and radius
A
resistance depends on radius
R (directly proportional to) 1/radius^4
7
Q
in the cardiovascular system, changes in resistance result from what two things
A
vasoconstriction
vasodilation
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
9
Q
does each side of the heart function independently
A
yes, each side functions as an independent pump
10
Q
what serves as a pressure reservoir in the heart
A
elastic arteries
11
Q
what do arterioles have a high proportion of
A
muscle
12
Q
what is the site of variable resistance
A
arterioles
13
Q
what happens at capillaries? why?
A
site of exchange because they are very thin
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
15
Q
what is allocation of blood flow to body structures determined by
A
changes in arteriolar resistance
16
Q
what are three changes that can affect arteriolar resistance
A
arranged in parallel
controlled individually
smooth muscle changes
17
Q
what are two types of smooth muscle changes that can happen in arterioles
A
vasoconstriction and vasodilation
18
Q
what two things does vasoconstriction result in
A
decrease in pressure downstream
increase in pressure upstream
19
Q
where is the velocity of blood flow the lowest
A
in capillaries
20
Q
what does velocity of blood flow depend on
A
total cross-sectional area of vessels
21
Q
do capillaries have a small or large cross-sectional area
A
large
(lowest velocity)
22
Q
what does the low velocity in capillaries allow
A
time for diffusion
23
Q
what are the three mechanisms of exchange at capillaries
A
diffusion (simple, facilitated)
vesicular transport
bulk flow (water and solutes)
24
Q
what type of exchange uses diffusion
A
exchange of small solutes
25
what type of exchange uses vesicular transport
larger solutes and proteins
26
what is transcytosis
combination of endocytosis, vesicular transport, and exocytosis
27
what type of exchange uses bulk flow
water and solutes
28
what are the two possibilities with bulk flow
filtration
absorption
29
what is filtration
from plasma --> interstitial fluid
30
what is absorption
from interstitial fluid --> plasma
31
what three things are bulk flow determined by
hydrostatic pressure (PH)
colloid osmotic pressure (pi)
net filtration pressure (NFP)
32
where is the hydrostatic pressure lowest
at venous end due to friction
33
what is the osmotic pressure a result of
proteins restricted to plasma
34
is colloid osmotic pressure the same as total osmotic pressure? what is the difference?
no
colloid osmotic pressure does not vary across capillary bed
35
what is the net filtration pressure (NFP)
hydrostatic pressure (PH) - colloid osmotic pressure (pi)
36
if the NFP is greater than 0 is there net filtration or net absorption
net filtration
37
if the NFP is less than 0 is there net filtration or net absorption
net absorption
38
where does net filtration occur
arterial end
39
where does net absorption occur
venous end
40
is the filtration at the arterial end or the absorption at the venous end bigger
filtration at arterial end usually exceeds absorption at the venous end
41
how many L of fluid is lost from plasma per day
~3L
42
what is the lymphatic system made up of
vessels and nodes
43
what are the four functions of the lymphatic system
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
44
what is the driving pressure of blood pressure
pressure created in ventricles, transferred to arteries
45
as blood travels through arteries --> capillaries --> veins, what happens to the pressure
pressure decreases
46
what kind of arteries serve as a pressure reservoir
elastic arteries
47
how do elastic arteries serve as a pressure reservoir (3)
1. stretch during systole
2. elastic recoil maintains driving pressure during diastole
3. backward flow during diastole prevented by semilunar valves
48
what are the two measures of blood pressure
1. systolic (sBP)
2. diastolic (dBP)
49
when is systolic pressure measured
during ventricular systole
50
when is diastolic pressure measured
during ventricular diastole
51
what is the pulse pressure (PP)
sBP - dBP
52
what is the mean arterial pressure (MAP)
dBP + PP/3
53
what does the MAP reflect
driving pressure for blood flow to tissues
54
what indicates whether there is enough pressure to perfuse all organs
mean arterial pressure (MAP)
55
what is the MAP equal to
MAP = CO x TPR
56
what is TPR
total peripheral resistance = resistance to flow, due to arterioles
57
what is the driving pressure
MAP
58
what does MAP depend on
flow in vs. flow out
59
what are the 4 factors that can influence MAP
1. cardiac output
2. diameter of arterioles
3. blood volume
4. diameter of veins
60
what happens to MAP with increased cardiac output
MAP increases
61
what happens to MAP when the diameter of arterioles decreases
the TPR (arteriolar resistance increases) so the MAP increases
62
what are most systemic arterioles innervated by
sympathetic nervous system neurons
63
what so SNS neurons release
norepinephrine
64
what happens to the systemic arterioles when NE is released
vasoconstriction
65
how does NE cause vasoconstriction (3)
1. alpha adrenergic receptors
2. tonic control
3. maintain vascular tone
66
what happens with epinephrine release
vasoconstriction due to epi acting on alpha-adrenergic receptors
67
what happens to MAP when blood volume increases
MAP increases
68
does the cardiovascular system respond to changes in blood volume quickly or slowly
quickly
69
do the kidneys respond to changes in blood volume quickly or slowly
slowly
70
what kind of innervation of smooth muscle causes vasoconstriction
sympathetic innervation of smooth muscle using alpha-adrenergic receptors
71
what happens to MAP if blood is redistributed to the arteries using smooth muscle
increased MAP
72
what is the chain of events causing increased MAP starting at increased venous return (4 steps total)
1. increased venous return
2. increased EDV (end diastolic volume)
3. increased SV (stroke volume)
4. increased MAP
73
what region of the brain controls the cardiovascular system
cardiovascular control center (CVCC) in medulla oblongata
74
what does the CVCC in medulla control specifically
blood pressure and distribution of blood to tissues
75
what is the baroreceptor reflex
primary reflex pathway for homeostatic control of MAP
76
what do baroreceptors respond to
stretch-sensitive
respond to pressure
77
where are baroreceptors located
in carotid arteries and aorta
78
is the baroreceptor reflex slow or quick
rapid response
79
does the baroreceptor reflex ever turn off
no it is functioning all the time
80
what kind of output does the CVCC control to specific regions of the body
sympathetic to regulate blood distribution
81
what happens to blood flow during a fight or flight response
increased blood flow
82
what happens when NE and epi bind to alpha adrenergic receptors
widespread vasoconstriction
83
what happens when NE and epi bind to beta2 adrenergic receptors
vasodilation in skeletal muscle, heart, and liver
84
what is active hyperemia
local increase in blood flow due to an increase in metabolic activity
85
why is active hyperemia important
strategy for tissues to regulate their own blood supply
86
what (3) paracrines can cause local vasodilation
nitric oxide
adenosine
histamine
87
what happens with increased nitric oxide
decreased O2
88
what happens with increased adenosine
increased CO2
89
what happens with increased histamine
increased H+
90
what is cellular respiration
intracellular process using O2 to generate ATP + CO2 + H2O
91
what is external respiration
movement of gases between atmosphere and cells
92
what are the four types of external respiration
ventilation
gas exchange (pulmonary circuit)
gas transport
gas exchange (systemic circuit)
93
what is ventilation
exchange of air between atmosphere and lung alveoli
94
where does gas exchange in the pulmonary circuit occur
between lung alveoli and blood
95
where does gas transport occur
in the blood
96
where does gas exchange in the systemic circuit occur
between blood and tissues
97
how is pH regulated by the respiratory system
via retention or elimination of CO2
98
what gas is obtained for cells and what gas is removed
O2 to obtained
CO2 is removed
99
what is alveolar ventilation
Va
volume of fresh air that reaches alveoli per minute
100
what happens to Va with hyperventilation
increases
101
what happens to Va with hypoventilation
decreases
102
what two things can happen if ventilation is inadequate
hypoxia: insufficient O2 availability to cells
hypercapnia: elevated CO2 levels
103
what does the gas exchange at lungs and tissues require
a gradient in partial pressure
104
what does the partial pressure gradient apply to
each gas independently (ex. O2 will move from high PO2 to low PO2)
105
what is the partial pressure of a gas
the pressure of a single gas
Pgas = Patm x fractional concentration of gas in the atmosphere
106
what is Daltons Law
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))
107
what percentage of N2, O2, and CO2 are in the atmosphere
N2: 78%
O2: 21%
CO2: 0.04%
108
at sea level, what is the Patm
760 mm Hg
109
what changes at different altitudes
Pgas and Patm
110
what is constant at different altitudes
the percentage of gas in the atmosphere (fractional concentration)
111
in typical alveoli, what are the partial pressures of O2 and CO2
PO2: 100 mm Hg
PCO2: 40 mm Hg
112
what happens to PO2 and PCO2 with hypoventilation
PO2 decreases
PCO2 increases
113
what happens to PO2 and PCO2 with hyperventilation
PO2 increases
PCO2 decreases
114
what are the partial pressures of O2 and CO2 in typical peripheral tissues
PO2: 40 mm Hg
PCO2: 46 mmHg
115
what are three factors that can increase alveolar gas exchange (diffusion)
increase partial pressure gradient
increase surface area available for gas exchange
decrease diffusion distance (from air to/from blood)
116
what are three factors that can decrease alveolar gas exchange
decreased surface area
decreased partial pressure gradient
increased diffusion distance
117
what are two things that can decrease the partial pressure gradient
high altitude
hypoventilation
118
what is Henrys Law
movement of gas from air to liquid is proportional to solubility and pressure gradient
119
is O2 or CO2 more easily dissolved in plasma
CO2 is more soluble in water
very little O2 can be carried dissolved in plasma
120
how is most O2 found in blood
bound to hemoglobin in red blood cells
121
what is the law of mass action
higher plasma PO2 = more binding
lower plasma PO2 = less binding = release of O2
122
what two things does the amount of O2 bound to Hb depend on
% saturation of Hb due to PO2
number of O2 binding sites (# RBC and Hb content per RBC)
123
what does the oxyhemoglobin saturation dissociation curve show
the % of available binding sites occupied
(determined by plasma PO2)
124
what is the normal % of available binding sites occupied in the lungs
98%
125
what shape is the oxyhemoglobin saturation curve
sigmoidal
(important for delivering O2 to active tissues)
126
what happens to the oxyhemoglobin saturation dissociation curve if PO2 decreases
flat part - not much effect
steep part - larger release of O2 from Hb
127
what happens when the oxyhemoglobin curve shifts to the right
increases O2 delivery to cells - lower affinity
(occurs in active or hypoxic tissues)
128
what causes the oxyhemoglobin curve to shift to the right
higher PCO2
lower pH
higher temperature
higher 2,3 BPG
129
when is 2,3 BPG produced
during chronic hypoxia (ex high altitude)
130
what are the three ways CO2 is transported in blood? which is most %?
1. dissolved in plasma
2. bound to hemoglobin
3. converted to bicarbonate ion
(70% is converted to bicarbonate ion)
131
what does the bicarbonate ion buffer
metabolic acids
132
what is the bicarbonate buffering reaction
CO2 + H2O -><- H2CO3 -><- H+ + HCO3-
133
what is hypercapnia and what does it cause
high CO2
--> right shift of curve --> high H+ --> acidosis
134
what is hypocapnia and what does it cause
low CO2
--> left shift of curve --> low H+ --> alkalosis
135
what happens to CO2 in peripheral tissues
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
what happens to CO2 in the lungs
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
what kind of muscle does ventilation use and what is it controlled by
skeletal muscle controlled by the CNA via somatic motor neurons
(does not require a conscious effort)
138
what is the rhythmic pattern of ventilation generated by
the medulla oblongata
139
what are the pacemaker neurons of ventilation
pre-Botzinger complex
140
what are the inspiratory muscles? expiratory muscles?
inspiratory: dorsal respiratory group
expiratory: ventral respiratory group
141
what do the pontine respiratory groups do
smooth out rhythm
142
what four things are the output signals of ventilation modified by
voluntary input (cerebral cortex)
limbic system (emotions)
fever
chemoreceptors
143
what do chemoreceptors monitor
CO2, O2, and pH levels
144
where are the central chemoreceptors located and what do they sense
located in medulla oblongata and sense changes in PCO2
145
what are changes in PCO2 detected as
pH of the CSF (cerebrospinal fluid)
146
where are the peripheral chemoreceptors located and what do they sense
located in carotid arteries and aorta
sense changes in PCO2, pH, and PO2 in blood (plasma)
147
what is ventilation (rate and tidal volume) controlled by
pCO2 and pH
148
what does PO2 need to fall under before affecting ventilation
60 mmHg
149
where does air flow in relation to pressure
from high to low pressure
150
what is Boyles Law
P1V1=P2V2
151
what is pressure inversely related to
volume of the container
152
what happens to the diaphragm and lung tissue during inspiration
diaphragm contracts (flattens)
lung tissue is stretched (requires fluid bond between lung and chest wall)
- air moves into lungs
153
what happens to the diaphragm and lung tissue during expiration
diaphragm relaxes (unflattens)
elastic recoil of lung tissue
- air moves out of lungs
154
what happens to the thoracic volume, alveolar volume, and alveolar pressure with inspiration
thoracic volume: increases
alveolar volume: increases
alveolar pressure: decreases
155
what happens to the thoracic volume, alveolar volume, and alveolar pressure with expiration
thoracic volume: decreases
alveolar volume: decreases
alveolar pressure: increases
156
what determines airway resistance
airway diameter
157
what happens to smooth muscle with bronchoconstriction and bronchodilation
bronchoconstriction: narrowing
bronchodilation: widening
158
what are two factors that can cause dilation of bronchioles
high CO2 in expired air
sympathoadrenal pathway -> epi -> beta2 adrenergic receptors -> dilation
159
what are two factors that can cause constriction of bronchioles
histamine from mast cells
parasympathoadrenal pathway -> ACh -> mAChR -> constriction
160
what does compliance of the lungs mean
ability of lungs to stretch
161
what does elastance of the lungs mean
ability to recoil after stretch
162
what does low compliance cause in relation to ventilation
difficulty inspiring
163
what does low elastance cause in relation to ventilation
difficulty expiring due to decreased recoil
164
what happens to resistance when the airway is narrowed
increased resistance and difficulty expiring due to the collapse of the bronchioles
165
what is tidal volume
VT
volume of air that moves during a single inspiration or expiration
166
what is inspiratory reserve volume
IRV
additional volume you can inspire about VT
167
what is expiratory reserve volume
ERV
amount of air that can be forcefully exhaled after end of a normal expiration
168
what is residual volume
RV
volume of air remaining after maximal exhalation
169
what is vital capacity
VC
VT + IRV + ERV
170
what is total lung capacity
TLC
VC + RV
171
what is ventilation rate
VR
breaths / minute
172
what is minute (total pulmonary) ventilation (VE)
volume of air inhaled or exhaled per minute (mL/min)
VR x VT
(breaths/min) x (mL/breath)
173
what are the normal (resting) values for VR VT and VE
VR: 12 breaths/min
VT: 500 mL/breath
VE: 6 L/min
174
what is the equation for alveolar ventilation
VA = VR x (VT - VD)
VD= anatomic dead space
175
what is the main function of the kidneys
filter the blood to:
retain vital substances
eliminate wastes
maintain homeostasis of water and ions (by retaining/eliminating as needed)
176
how do the kidneys play a role in hormonal regulation of blood pressure
by the renin-angiotension-aldostrone system (RAAS)
177
what does the urinary bladder do
storage and release (micturition) of urine
178
what are the four processes that occur in the kidneys
1. filtration
2. reabsorption
3. secretion
4. excretion
179
where does filtration occur
Bowmans capsule
180
what happens in the proximal tubule of the nephron
reabsorption and secretion of many specific substances
181
what happens in the loop of henle
reabsorption
countercurrent multiplier
182
what makes up the distal nephron and what function does it perform
distal tubule and collecting duct
reabsorption and secretion; final control of water, ions, pH
183
what is the pathway of blood supply in the renal portal system
afferent arteriole --> glomerulus --> efferent arteriole --> peritubular capillaries
184
what is filtration
passive leakage of plasma
185
what does filtration produce
filtrate = filtered plasma that is nearly isosmotic with plasma with no proteins or blood cells
186
what makes up the renal corpuscle
glomerulus and bowmans capsule
187
what is the filtration fraction
percentage of plasma passing through glomerulus that is filtered = 20%
188
what is the glomerular filtration rate
GFR
volume filtered/time
GFR= net filtration pressure (NFP) x filtration coefficient
189
what three filtration barriers must substances leaving the plasma pass through
fenestrated capillary endothelium
basement membrane
podocytes of epithelium of Bowmans capsule (filtration slits/gaps)
190
what two factors increase the filtration coefficient
increased surface area of glomerular capillaries
increased permeability of filtration slits
191
what three things does the net filtration pressure in the renal corpuscle depend on
1. glomerular hydrostatic pressure (PH)
2. colloid osmotic pressure (pi)
3. capsule fluid pressure (Pfluid)
192
what is the glomerular hydrostatic pressure
blood pressure
193
what is the colloid osmotic pressure due to and what does it oppose
due to plasma proteins
opposes filtration
194
what is the capsule fluid pressure due to and what does it oppose
due to bowmans capsule
opposes filtration
195
what is the equation for net filtration pressure and what is the normal value
PH - pi - Pfluid
10mmHg
196
what two local controls by the kidney cause GFR to be fairly constant over a range of MAPs
1. autoregulation by myogenic response
2. autoregulation by juxtaglomular response
197
in MAP increases (GFR increases) what happens to the afferent arteriole
smooth muscle of the afferent arteriole stretches
198
what are the 4 steps that lead to vasoconstriction of the afferent arteriole after MAP increases
1. stretch-sensitive ion channels open
2. muscle cells depolarize
3. Ca2+ channels open
4. vascular smooth muscle contracts
5. vasoconstriction
199
what three things happen after the afferent arteriole is constricted
1. decreased blood flow through afferent arteriole
2. decreased NFP through renal corpuscle
3. decreased GFR (GFR=NFP x filtration coefficient)
200
what is the juxtaglomerular apparatus
specialized region where distal tubule and afferent arteriole meet for regulation of GFR and MAP
201
where is the macula densa located
wall of tubule
202
where are the granular cells located
in wall of arteriole
203
if GFR increases, what happens to the fluid flow through tubules
increased GFR = faster flow
204
what happens when macula densa cells detect a higher NaCl concentration flowing through the tubules
1. release paracrine signals
2. vasoconstriction of afferent arteriole
3. decreased GFR
205
at rest, what kind of autoregulation dominates
renal autoregulation
206
under sympathetic input (ex. intense exercise) what happens to the afferent arteriole
increased epi, NR, and angiotension II constrict afferent arteriole to help maintain increased MAP
207
what happens to urine production with decreased GFR
decreased urine production to maintain blood volume
208
what percentage of filtrate is reabsorbed and where
99% in proximal tubule
209
what is the pathway from filtrate to blood
filtrate --> interstitial fluid --> blood
210
how is Na+ reabsorbed
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
what is the primary driving force for most reabsorption and why
Na+
-anions follow Na+ to even out charges
- water follows solutes by osmosis to even out concentration on both sides of cell
212
what happens if there is a high concentration of other solutes in the filtrate
they are reabsorbed passively using diffusion (using their concentration gradient)
213
what is Na+-linked (secondary active) transport used for
reabsorption of other substances (AA, glucose, etc) driven by Na+ concentration gradient
214
how is glucose reabsorbed
using the SGLT transporter to move glucose against its concentration gradient (Na+ moving down gradient)
215
what is the transport maximum
Tm
transport rate at saturation
216
what is the renal threshold
plasma concentration at which saturation occurs
217
what is the filtration of glucose proportional to
plasma concentration
-doesnt saturate because it just goes through the filtration slits
218
what is reabsorption of glucose proportional to
plasma concentration unless the Tm is reached (saturation)
219
what is glucose secretion
zero unless the renal threshold is reached
220
what is secretion
active transport from blood to filtrate
221
how is secretion selective
via transporters
222
what two main things is secretion important for
K+ and H+ homeostasis in the collecting duct
organic anion and cation elimination in proximal tubule
223
what happens to the secretion of a molecule when molecules are competing for carriers
secretion decreases
224
what is excretion
removal from body
225
what is filtrate called when it leaves the collecting duct
urine
-no change in composition
226
what is excretion equal to
excretion = filtration - reabsorption + secretion
227
what is renal handling of a substance
an accounting of how much reabsorption and/or secretion of that substance occurs
228
what is the clearance of a substance
volume of plasma cleared of that substance per minute
229
what happens to the substance if it is equal to GFR
the substance is neither reabsorbed nor secreted
230
what happens to the substance if it is less than GFR
net reabsorption of the substance
231
what happens to the substance if it is greater than GFR
net secretion of the substance
232
what type of control is micturition (urination) under
both spinal reflex and voluntary control
233
what is tonically active at rest in the bladder
somatic motor neurons to external sphincter tonically active
234
what is passively closed at rest in the bladder
internal sphincter (smooth muscle)
235
what two things activate micturition reflex in the bladder
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
what provides the voluntary inhibition of micturition
cerebral cortex: excitatory input to somatic motor neurons overrides reflex inhibition (makes sphincter contract)
237
what three things need to be regulated in order to survive (in regards to the urinary system)
ECF osmolarity
ECF volume
concentrations of electrolytes (ion species)
238
what is the most important ECF solute and why
Na+
primary determinant of ECF volume
239
what is Na+ controlled by (3)
aldosterone
ANP
angiotensin II
240
what is the main determinant of resting Vm and why
K+ because dysregulation affects excitable tissues
241
what is K+ controlled by
aldosterone
242
can ECF volume and osmolarity change independently
yes
243
what is blood osmolarity maintained at
300 mOsM
244
what does dysregulation of blood osmolarity cause
hypo/hypertonic environment --> cells swell or shrink
hypo=swell
hyper=shrink
245
what is blood osmolarity controlled by
vasopressin and thirst
246
what does dysregulation of ECF volume alter
MAP
hypertension (high BP)
hypotension (low BP)
247
what is ECF volume controlled by
regulating Na+
248
what three response systems integrate fluid and electrolyte balance by responding to changes in blood volume
cardiovascular responses
renal/kidney responses
behavioral responses
249
what are the characteristics of the cardiovascular responses to changes in blood volume
fast-neural control
cant be sustained
cant add/remove fluid
250
what are the characteristics of the renal/kidney responses to changes in blood volume
slow-mainly endocrine control
can remove fluid
251
what are the characteristics of the behavioral responses to changes in blood volume
slow
can add fluid (thirst/drinking)
252
how is ECF osmolarity maintained (in regards to urine)
high ECF osmolarity increases thirst intake to vary urine concentration
253
what is the osmolarity of the filtrate entering the collecting duct
dilute (~100mOsM)
254
what is the collecting duct surrounded by
medullary interstitial fluid with osmotic gradient
superficial ~300 mOsM
deep ~ 1200 mOsM
255
what is the purpose of the medullary interstitial fluid with the osmotic gradient
reabsorbs water from the collecting duct via osmosis
256
what happens to filtrate traveling through the medulla
it becomes progressively more concentrated and becomes urine
257
what is the amount of reabsorption in the collecting duct regulated by
altering the permeability
258
what does the loop of henle function as
countercurrent multiplier that produces interstitial osmotic gradient
259
what does the thick portion of the ascending limb reabsorb
actively reabsorbs Na+ and Cl- into interstitial fluid
not permeable to water
260
what does the thick portion of the ascending limb increase the osmolarity of
interstitial fluid
261
what does the thick portion of the ascending limb decrease osmolarity of
filtrate as it ascends toward the cortex
262
what is the filtrate initially isosmotic with
blood (~300)
263
what reabsorption happens in the descending limb
passive reabsorption of water (osmosis) into interstitial fluid
impermeable to solutes
264
what does the descending limb decrease osmolarity of
interstitial fluid
265
what does the descending limb increase osmolarity of
filtrate progressively as it descends into medulla
266
what does the interstitial osmotic gradient result from
interaction between ascending and descending limbs
267
what is the vasa recta
peritubular capillaries associated with loop of henle
268
what are the functions of the vasa recta
removes water and solutes reabsorbed by the loop of henle
has similar osmotic gradient
269
what is vasopressin and where is it secreted from
antidiuretic hormone (helps retain water)
secreted from posterior pituitary
270
how does vasopressin increase the collecting ducts permeability to water
causes collecting duct cells to insert aquaporin channels in membrane
271
when is concentrated urine (up to 1200) produced and how
if ECF osmolarity too high
1. increased vasopressin
2. increased permeability
272
when is dilute urine (to 50) produced and how
if ECF osmolarity too low
1. decreased vasopressin
2. decreased permeability
273
what four stimuli causes vasopressin secretion
increased ECF osmolarity
decreased blood pressure
decreased blood volume (less arterial stretch)
angiotensin II
274
what is aldosterone secreted by and what does it act on
secreted by: adrenal cortex
acts on: principal (P) cells of distal nephron
275
what does aldosterone do to Na+ and K+
causes increased Na+ reabsorption and increased K+ secretion
276
what two things is aldosterone stimulated by
low blood pressure (via RAAS pathway)
increased K+
277
what is the renin-angiotensin-aldosterone system (RAAS)
endocrine pathway promoting increased MAP
278
what is angiotensinogen
inactive plasma protein
279
what is renin
enzyme secreted by granular cells
280
what is renin secreted in response to
decreased MAP
281
what are the three ways the body can sense a decrease in MAP
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
what does renin do to angiotensinogen
convert it to angiotensin I (ANG I)
283
what converts angiotensin I to angiotensin II
angiotensin converting enzyme (ACE)
284
how does ANG II raise MAP (6 ways)
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
where is the atrial natriuretic peptide secreted from and why
the atria in response to increased stretch of the atria (indicates increased blood volume)
286
how does ANP (atrial natriuretic peptide) decreased blood volume and MAP (4 ways)
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
