Renal Flashcards
1
Q
True/False - Urine flows from the major calyces to the minor calyces to the renal pelvis
A
False - Urine flows from the minor calyces to the major calyces to the renal pelvis
2
Q
Draw out a flow diagram of blood flow through the kidney
A
Renal artery - segmental artery - interlobar artery - actuate artery - interlobular artery - afferent arteriole - glomerulus (capillaries) - efferent arteriole - vasa recta - peritubular capillaries - interlobular vein - arcuate vein - interlobar vein - renal vein
3
Q
Where does the interlobar artery carry blood from and to
A
From the renal artery to the afferent arterioles
4
Q
Label the regions of the nephron
A
Renal corpuscle, proximal convoluted tubule, distal convoluted tube, distal limb of nephron loop, ascending limb of nephron loop, collecting duct
5
Q
Label the renal corpuscle
A
Proximal convoluted tubule, podocyte, capsular/urinary space, parietal layer of glomerular capsule, efferent arteriole, distal convoluted tubule, afferent arteriole, endothelial cell
6
Q
What are 7 functions of the kidney
A
- Regulation of water and electrolyte balance
- Regulation of blood pressure
- Excretion of waste products
- Hormone production
- Regulating glucose
- Regulating blood pH
- Regulation of RBC production
7
Q
In a 100 kg male, how much approximate mass is solids?
A
40 kg
8
Q
In a 100 kg male, how much approximate mass is fluids?
A
60 kg
9
Q
In a 100 kg male, how much approximate body fluid is intracellular?
A
40l
10
Q
In a 100 kg male, how much approximate body fluid is extra cellular?
A
20l
11
Q
In a 100 kg male, how much approximate body fluid is interstitial fluid?
A
16l
12
Q
In a 100 kg male, how much approximate body fluid is plasma?
A
4l
13
Q
Osmolality assumes that …
A
The solute is completely impermeant (cannot cross the membrane)
14
Q
Define osmolality
A
The count of dissolved particles in a volume of solution
15
Q
Tonicity accounts for …
A
The ability of the solute to cross a semipermeable membrane
16
Q
Define Tonicity
A
The tendency of a solute to resist expansion of the intracellular volume
17
Q
As a result of water intake, intracellular volume will …
A
Increase - ingestion of a hyposmotic solution will abuse cells to swell and increase in volume
18
Q
After a 100 kg man ingests water, estimate his extra cellular fluid volume …
A
21l
Total weight = 100 kg, Water ~60% = 60kg + 3 = 63kg = 63 L ECF is 1/3 total fluid = 21 L
19
Q
Compared to a 100 kg man’s state prior to water ingestion, you would describe his plasma osmolarity after water ingestion as being …
A
Hypo-osmotic
The water consumed will dilute fluid in the body, meaning the osmolarity of all fluid including plasma is decreased compared to its osmolarity before the water consumption
20
Q
What is the concentration of cl- in the ECF vs. ICF
A
ECF - 117 mM
ICF - 3mM
21
Q
What is the equation used to calculate the amount of a substance (X) excreted in the urine?
A
Excreted (X) in urine = Filtered (X) - reabsorbed (X) + secreted (X)
22
Q
Where does filtration occur?
A
Glomerular capsule
23
Q
Where does reabsorption into the blood (peritubular capillaries) stream occur
A
Renal tubule and collecting duct
24
Q
Where does secretion occur
A
In the renal tubule and collecting duct from the blood (peritubular capillaries)
25
Is water primarily reabsorbed or secreted ?
Reabsorbed
26
Is sodium primarily reabsorbed or secreted
Reabsorbed
27
Is glucose primarily reabsorbed or secreted
Reabsorbed
28
Is creatinine primarily reabsorbed or secreted
Secreted
29
An increase is renal sympathetic nerve activity can lead to --- in GFR. This is a consequence of --- arteriole ---- which --- the --- hydrostatic pressure. This pressure, minus the --- hydrostatic pressure, minus the. --- osmotic pressure, gives us the net flitration pressure, which determines glomerular filtration
decrease, afferent, constriction, decreases, glomerula blood, capsular, bloof colloid
30
Is the renal capsule located in the cortex or medulla
cortex
31
What can be found in the renal capsule?
Glomerulus
32
What two blood vessels connect directlty to the glomerulus?
afferent arteriole and efferent arteriole
33
does an increase in hydrostatic pressure in the renal capsule result in a decrease in glomerular filtration?
Yes, and increase in the capsular hydrostatic pressure will result in a decrease in glomerular filtration becasue NFP = GBHP - CHP - BCOP
34
Where does the largest amount of solute and water reabsorbtion occur in the nephron?
proximal convoluted tubule.
35
How does the body reabsorb water when necessary?
Water reabsorption can occur via osmosis throughout the renal tubule when ADH is present, **except** in the **ascending loop of henle**
36
Is the osmolarity of the filtrate at the end of the Proximal convoluted tubule equal to that in the plasma?
Yes because both solutes and water are reabsorbed to a similar extent in the proximal convolute tubule, hence the osmolarity is unchanged
37
Explain what happens to the osmolarity from the end of the proximal convoluted tubule, through the descending and ascending loop of henle, to the collecting duct.
- descending loop of Henle, mainly water is reabsorbed thus filtrate becomes more concentrated (osmolartiy increases).
- thick ascending loop of Henle is impermeable to water but sodium and other ions are actively trasnported out. Therfore, the filtrate becomes more dilute (oslomartiy decreases).
- Consequently at the distal convoluted tubule, the osmolarity of the filtrate will have decreased back to a value lower than that or equal to that of the descending loop of Henle.
- The osmolarity of the filtrate gradually increases in the collecting duct
38
Where is the sodium/glucose symporter and the Sodium/Hydrogen antiporter found?
Proximal convoluted tubule
39
Where is there minimal sodium reabsorption?
In the descending loop of Henle
40
Where is the Sodium, potassium, chloride symporter found?
Thick ascending loop of Henle
41
Where can we find sodium channels?
Distal convoluted tubule and collecting duct
42
What is the function of the principal cells of the collecting duct?
Reabsorption of sodium, secretion of potassium
43
Label the collecting duct principal cell diagram
tubule lumen - na + into and out to interstitial fluid - atp to adp, potassium to lumen (na+ reabsorption and k + secretion)
44
What is the proximal convolted tubule responsible for?
The proximal convoluted tubule (PCT) has a high capacity for reabsorption. The function of the PCT is to reabsorb most of the filtered Na+ ions in order to deliver only a small quantity of Na+ ions to downstream sites.
- sodium reabsorbtion via sodium-glucose symporter
- sodium via sodium potassium pump to blood
- glucose to blood via facilitated diffusion
45
How does the shape of the proximal convolted tububles epithelial cells aid reabsorption?
he surface of the cells facing the lumen of the proximal convoluted tubule are covered in microvilli (tiny finger-like structures). This type of surface is called a brush border. The brush border and the extensive length of the proximal tubule dramatically increase the surface area available for reabsorption of substances into the blood enabling around 80% of the glomerular filtrate to be reabsorbed in this segment.
46
What substances are reabsorbed at the PCT? How is this achieved?
glucose, amino acids, lipid soluble substances.
- largest amount of solute and water reabsorption from filtered fluid occurs hre
- 60% glomerular filtrate, 60% NaCl and water, 100% glucose, amino acids, lipid soluble substances
- occurs via symporters (na, glucose symprter) and antiporters (na H+ antiporter)
- water moves via osmosis
47
Label the proximal tubule epithelial cell reasborption
tubule lumen (apical membrane): Glucose, amino acids, H2O trans, lipid soluble substances, H2O para.
Epithelial cell: Na+, ATP to ADP, K+
Interstial fluid
48
The hormone that has the greatest influence on water reabsorption is?
Antidiuretic hormone (ADH/vasopressin) - it does so by modulating the permeability of water in the epithelium of the nephron.
49
ADH acts on which area of the nephron?
Distal covoluted tubule and collecting duct
50
What are the stimuli for ADH secretion?
- osmolarity increase in plasma and interstitial fluid
- decrease in blood volume
## Footnote
Reduction in blood volume reduces the firing rate of the stretch receptors, thereby reducing the tonic inhibition and increasing ADH release, causing water retention by the kidney.
51
How does ADH increase H2O permeability in the DCT and collecting duct?
Insertion of aquaporin-2-channels to the apical membrane
aquaproin-2 containing vesciles are rapidly inserted via exocytois inot the apial membrane in response to and increase in ADH levels.
these aquaporins increase the permeability of water resulting in increased water reasborption via osmosis
52
What is the function of angiotensin II on adrenal cortex?
stimulates the release of aldotestosterone from the adrenal cortex
aldosterone acts on the collecting ducts to reabsorb more na+ and cl- and hence more h2o
53
What cells in the glomerulus secrete renin?
Juxtaglomerular cells of the afferent arteriole.
54
What stimulus increases renin secretion?
decreased blood volume
55
What stimui decrease renin secretion?
increased blood pressure, increased plasma sodium, decreased sympathetic activity
56
An increase in renin --- the Na+ content in urine
decreases
57
The release of renin results in increased --- levels
angiotensin II
58
An increase in angiotensin II --- both Na+ reabsorption in the --- convoluted tubule and the release of aldosterone, which --- Na+ reabsorption in the collecting duct.
Consequently, the water content in urine is ---. This increases reabsorption of Na+ and Cl- in the collecting duct caused by --- has an osmotic effecr, --- water reabsorption.
increases, proximal, increases
decreased, aldosterone, increasing
59
Na+ and Cl- in the distal convolted tubule primarily affect which arteriole?
afferent
60
ANP (atrial natriuretic peptide) affects which arteriole primarily?
afferent
61
Angiotensin affects what arteriole primarily?
both afferent and efferent
62
How does an increase in ANP (atrial natriuretic peptide) affect glomerular filtration rate?
increases GFR
63
How does an increase in Angiotensin II affect glomerular filtration rate?
decreases GFR
64
How does an increase in Na+ and Cl- in the distal convoluted tubule affect glomerular filtration rate?
decreases GFR
65
How does an increase in sympathetic nerve activity affect glomerular filtration rate?
decreases GFR
66
A 70 kg male runner loses 2.0 kg of his bodyweight as a result of sweating. This sweat has a sodium content of 40 mM and and osmolarity of 120 mOsm/L. Which hormone is the most important in ensuring the runner is able to prevent further urinary water loss?
- antidiuretic hormone (ADH/vasopressin)
- the runner has mainly lost water through hyposmotic sweat. This will decrease the plasma volume and increase the plasma osmolartiy
- Increased plasma osmolarity will stimulate further realease of ADH from the posterior pituitary gland.
- This will result in increased water reabsorption to mantain water balance. It does this by making the collecting duct more pemeable to water.
Aldosterone and angiotensin II will also increase in response to the decreases plasma osmolarity, however their main function is to maintain salt balance.
ANP will decrease in response to decreased plasma volume. ANP incrases loss of water and Na+ in unrine.
67
Describe the external anotomy of the kidney
renal capsule, adipose capsule, renal fascia
68
What is the function of the renal capsule?
1. physical barrier
2. protection against trauma
3. maintains the shape of kidneys
69
What is the function of the adipose capsule?
1. padding
2. physical protection
3. maintains the position of the kidneys
70
What is the function of the renal fascia?
anchors the kidneys to surrounding structures
71
Label the internal anatomy of the kidey pg. 150
//
72
What is the functional unit of the kidney?
nephron
73
What are the two different classes of the nephrons?
cortical nephrons and medullary nephrons calles JUXTAMEDULLARY NEPHRON
74
What structures can be found in bowmans capsule?
visceral - podocytes (modified epithelium)
parietal - form the outer wall of the capsule (simple squamous epithelium)
75
Where does filtrate accumulate in the glomerulus?
capsular/urinary space
76
Describe how the structure of the filtration membrane in the glomerulus affects filtration
1. fenestrations (pore) of glomerular endothelial cells: prevents filtration of blood cells but allows all components of blood plasma to pass through
2. basal lamina of glomerulis: prevents filtration of larger proteins
3. slit membrane between pedicels: prevents filtration of medium sized proteins
77
Label the filtration membrane pg. 154
podocyte, filtration sit, pedicel, cytoplasm of capillaries
78
Draw the filtration membrane and describe what cells/proteins can pass through each barrier
Fenestrated endothelium - no RB cells, yes large,medium and small proteins
Basal lamina (secreted by podocytes) - no RB cells, no large proteins, yes medium and small proteins
Slit membrane/diaphragm between foot processes - no RB cells, no large proteins, no medium proteins, yes smll proteins
79
label the blood supply system of the kidney and nephron pg. 151
//
80
Where does filtration occur?
renal corpuscle
81
what is the blood component of the renal corpuscle?
glomerulus
82
label the renal corpuscle and surrounding structures pg 153
//
83
Define homeostasis
maintenance of the milieu interier in a steady state
84
define osmolality
is a measure of the effective gradient for water **assuming that all the osmotic solute is completely impermeant**. it is simply the count of the number of dissolved particles in a set of volume. measured in kg
85
define tonicity
a functional term that describes the tendency of a solution to resist expansion of the intracellular volume
86
when are two solutions isosmotic?
when they have the same number of dissolved particles per unit, regardless of how much water would flow across a given membrane barrier
87
when are two solutions isotonic?
when they would cause no water movement across a membrane barrier, regardless of how many particles are dissolved
88
What is meant by a hyperosmotic solution? give an example
a solution with a higher osmolarity than another
a 300 millimolar solution of NaCl vs a 300 millimolar solution of Urea
89
What is meant by a hyposmotic solution? give and example
a solution with a lower smolarity than another
a 150 milimolar solution of Urea vs a 150 milimolar solution of NaCl
90
What is meant by a isosmotic solution? give an example
solutions with the same osmolarity
150 milimolar of NaCl and 300 milimolar of Urea
91
What effect will a hypertonic solution have on cell size?
hypertonic - solution has higher osmolarity (concentration of particles) than cell
causes **cell shrinkage as water leaves the cell**
92
What effect will an isotonic solution have on cell size?
cell neither shrinks nor swells
93
What effect will a hypotonic solution have on cell size?
hypotonic - solution has lower osmolarity than the cell
water will enter the cell causing cell to swell
94
Define osmosis
the diffusion of water through a selectively permeable membrane from an area of low solute concentration to an area of higher solute concentration
95
How much percent of body weight is water in male,s females and infants?
m- 50%
f- 60%
infants - 65 -75%
96
What is meant by intracellular fluid?
fluid found inside the cell and accounts for about 2/3 of the body fluid
97
What is meant by extracellular fluid?
all the fluid outside the cell and accounts for the other 1/3 of the bodys fluid. approximately 20% of the ECF is blood plasma and the other 80% interstitial fluid (between cells)
98
List the sources of water gain and their relative amounts under normal conditions
1. metabolic water - 200ml or 8%
2. Ingested foods - 700 ml or 28%
3. Ingested liquids - 1600 ml or 64%
99
List the sources of water loss and their relative amounts under normal conditions
1. GI tract - 100 ml or 4%
2. lungs - 300 ml or 12%
3. Skin - 600 ml or 24%
4. Urine/Kidneys - 1500 ml or 60%
100
What are the main electrolytes in the human body?
sodium, chloride, potassium, magnesium, calcium, hydrogen phopshate and hydrogen carbonate
101
What electrolytes have higher ECF conc.
sodium, calcium and chloride
102
What electrolytes have higher ICF conc.
potassium
103
Why are the ion gradients so important?
responsible for setting the membrane potential, generating electrical actvity in nerve and muscle, providing energy for the uptake of nutrients and the expulsion of waste products
104
What are the two components of ECF?
blood plasma and interstitial fluid
105
What are the three stages of urine production?
1. filtration at the glomerulus
2. tubular reabsorption
3. tubular secretion
106
briely explain the production of urine
1. afferent arteriole carries blood from the renal artery to the glomerulus
2. filtration from blood into nephron
3. efferent arteriole carriers blood to renal vein passing throigh the peritubular capillaries and vasa recta first
4. tubular reabsorption from tubular fluid into the blood
5. tubular secretion from blood into tubular fluid
6. urine in renal tubule excreted
107
How much water is filtered in the body each day?
180 L
108
How much water is reabsrobed in the body each day?
178.6 L
109
How much water is excreted from the body each day?
1.4 L
110
How much sodium is excreted a day?
150 mmol (about a teaspoon)
111
How much glucose if filtered a day?
180 g
112
How much glucose is reabsorbed and excreted a day?
180 reabsorbed thus none excreted
113
How much vreatine is filtered each day?
1.8 g
114
How much creatine is reabsorbed a day?
0 g
115
How much creatine is excreted a day
1.8 g
116
define glomerular filtration
the process that your kidneys use to filter excess fluid and waste products out of the blood into the urine collecting tubules of the kidney, so they may be eliminated from your body.
117
What two substances does glomerular filtrate lack?
proteins and high molecular weight compounds, and is free from blood cells
118
glomerular filtration is how much percent of total renal blood flow?
25% apprx. 125ml/min is approx 180 L/day
119
What ensures renal blood flow and thus glomerual filtration, remains constant?
autoregulation
120
Explain how autoregulation occurs
The ability of the kidney to maintain relatively constant blood flow, glomerular filtration rate (GFR) and glomerular capillary pressure is mediated by the myogenic response of afferent arterioles working in concert with tubuloglomerular feedback that adjusts the tone of the afferent arteriole in response to changes in the delivery of sodium chloride to the macula densa
121
urine output is directly proprtional to?
renal pressure
122
What is glomerular blood hydrostatic pressure (GBHP)
- GBHP is the mechanical pressure between the afferent and efferent arterioles
- pushes water and solutes in blood plasma (plasma filtrate) through the glomerular filter (from capillaries into capsular space).
- approx 55 mmHg
123
What is special about glomerular cappilaries and how does this influence filtration?
it is the only capillary bed that has arterioles before. andafter it, thus allowing for tight regulation of pressure gradients to maintain near constant glomerular filtration rate
124
What happens in the glomerulus in response to increased arterial pressure?
vasoconstriction of the afferent arteriole decreases blood flow to the glomerulus thus decreasing glomerular pressure and filtration rate
125
What happens in the glomerulus in response to decreased arterial pressure?
vasoconstriction of the efferent arteriole decreases blood flow and increases glomerular pressure and filtration rate
126
What is the normal pressure of the afferent arteriole ?
60 mmHg
127
State the normal pressures in the glomerulus
afferent arteriole - 60 mmHg
efferent arteriole - 50 mmHg
glomerulus - 55 mmHg
128
State the pressures in the glomerulus during vasoconstriction of the afferent arteriole
afferent arteriole - 55 mmHg
efferent arteriole - 50 mmHg
golmerulus - 52.5 mmHg
129
State the pressures in the glomerulus during vasoconstriction of the efferent arteriole
afferent arteriole. -60 mmHg
efferent arteriole - 55 mmHg
glomerulus - 57.5 mmHg
130
Glomerular filtration is dependent on?
pressure gradients
131
What is net filtration pressure?
determines how much water and small dissolved solutes leave the blood (approx 10 mmHg)
132
What is capsular hydrostatic pressure
the pressure exerted on the plasma filtrate by the elastic recoil of the glomerular capsule (approx 15 mmHg)
133
What is blood colloid osmotic pressure (BCOP)
the osmotic force of the proteins left in the plasma (pull on water in the plasma filtrate) approx 30 mmHg
134
What are the two opposing forces that decrease filtration
CHP and BCOP
135
Glomerular filtration is favoured by what pressure?
GBHP
136
What is the equation for NFP?
NFP = GBHP - CHP - BCOP
| normal approx 10 mmHg
137
What are the three factors that regulate glomerular filtration?
autoregulation
neural
hormonal
138
What is autoregulation?
1. Myogenic autorgeulation - Myogenic response refers to a contraction initiated by the smooth muscl ein the arterioles in respond to chnages in pressure
2. tubuloglomerular feedback - mechanism that links the rate of glomerular filtration to the concentration of salt in the tubule fluid at the macula densa
139
How does nerual regulation influence glomerular filtration
increased sympathetic activity leads to vasoconstriction and deacreased GFR
140
What hormones influence GFR?
Angiotensin II via vasoconstriction of afferent. andefferent arterioles
Atrial Natriuretic Peptide via relaxation of mesnagial cells, increasing surface area availbale for filtratoin
141
What does Atrial Natriuretic peptide do?
increases sodium and water excretion by
1. inhibiting the renin-angiotensin-aldosterone system (RAAS)
2. increasing GFR
3. renal SNS inhibiton
| wants to get rid of H2O and sodium
142
What two factors (broad) determine glomerular filtration
1. anything that alterns GHBP
2. anything that alters. thesurface area available for filtration
143
What cells sense the amount of sodium?
macula densa
144
Where are the macula densa cells located?
distalcovoluted tubule - adjacent to the afferent and efferent arterioles
145
What is the function of macula densa cells?
sense distal tubule flow and release paracrines that affecr afferent arteriole diameter
Macula densa cells produce prostaglandins as long as sodium levels are low. These prostaglandins stimulate the release of renin from juxtaglomerular cells.
146
What is the function of the juxtaglomerular apparatus
- maintain blood pressure
- quality control mechanism to ensure proper glomerular flow rate and efficient sodium reabsorption.
147
In terms of tubuloglomerular feedback, explain what happens when there is increased GFR?
Increased GFR - Increased tubular flow rate (ascending limb) - Increased tubular na+, Cl -, water content sensed by macula densa cells - juxtaglomerular appartus NO release decreased, afferent arteriole vasocostriction
| NO (nitric oxide) is a vasodilator
148
What do cortical nephrons produce?
dilute urine
149
What do juxtamedullary nephrons produce?
concentrated urine
150
Describe the structure of proximal convoluted tubule cells and how these relate to its function
- a high capacity for reabsorption
- simple cuboidal epithelial cells which have a brush border to increase surface area on the apical side.
151
What occurs at the PCT
| proximal convoluted tubule
the largest amount of solute and water reabsorption from filtered fluid occurs here
- 60% glomerular filtrate
- 60% NaCl and water
- 100% glucose
152
Explain the process of reabsorption at the PCT
- Na+ is pumped into the interstitial space by Na+ - K+ ATPase on basal surface of epithelial cells
- The active ba+ transport creates the concentration gradient
- Na+ movement into tubule cells occurs via symporters (sodium-glucose transporter) and antiporters (Na+/H+ allowing H+ to be secreted
- glucose and other solutes diffuse down their concentration gradient
- Na+ movement allows water movement via osmosis
--> thus water and Na+ and glucose reabsorbed while H+ is secreted
153
What is the osmolarity in the proximal convoluted tubule?
similar to plasma 290 mOsmol/L
154
what happens in the descending loop of henle?
- contains AQP1 and is therefore permeable to water but impermeable to ions and urea
- water drawn out of the filtrate down its osmotic gradient (high interstitial solute concentration osmotically draws water out and concentrates salt within the lumen.)
- interstitial fluid in renal medulla is 2-4x more concentrated than glomerular filtrate
| water is drawn out the dilute interstitial fluid
155
Filtrate entering the descending loop of henle is ____osmotic?
isosmotic to both blood plasma and cortical interstitial fluid
| same composition as plasma but does not contain plasma proteins
156
Filtrate entering the descending loop of henle is ____osmotic?
isosmotic to both blood plasma and cortical interstitial fluid
157
What is the concentration of the filtrate at the bottom of the loop of henle?
1200 mOsmol/L - very concentrated
158
What happens in the thick ascending limb of Henle's loop?
- actively reabsorbs sodium chloride (NaCl) and K+ but is impermeable to water.
- sodium potassium chloride symporters
- leak channels in apical (k) and basal (cl) membrane
- sodium potassium pump on basal membrane
| reabsorb to blood - less concentrated, get rid of ions but not H20
159
What is the concentration of filtrate once it gets to the top of the ascending limb
100 mOsmol/L - very dilute
160
Filtrate at the top of the ascending loop of henle is ____ to the interstitial fluid
hypo-osmotic
161
Down the medulla osmolarity gets ____ ?
higher bc. descending loop is permeable to H2O but not NaCl and ascending loop impermeable to H2O
162
Describe how the vasa recta is involved in the filtering in the loop of Henle
- Blood in the vasa recta (veins) removes water leaving the descending loop of henle
- Sodium from the ascending loop of henle is taken up by the artery
163
As the ascending limb pumps out ions, the filtrate becomes ____?
hyposmotic
164
What is the funtion of the distal convoluted tubule and the collecting duct?
- additional reabsorption of NaCl
- sodium/potassium ATPase that drives reabsorption
- Sodium reabsorption s regulated by hormones, which stimulate or inhibit sodium reabsorption as necessary.
165
In the collecting duct, water permeabiity is dependent on?
ADH - in the absence of ADh urine is dilute
166
What hormone is capable of producing concentrated urine?
Antiduretic hormone / Vasopressin
167
anything that constricts the afferent arteriole will ____ flow into the glomerulus and thus the GBHP, anything that constricts the efferent arteriole alone wil ____ GBHP
reduce, increase
168
what is the major stimulus for myogenic autoregulation?
increased stretching of smooth muscle fibres in afferent arteriole walls due to increased blood pressure
169
What happens in resonse to myogenic autoregulation?
stretched smooth muscle fibres contract thereby narrowing lumen of afferent arterioles
170
What effect does myogenic autoregulation have GFR?
decreases GFR
171
What is the major stimulus for tubuloglomerular feedback?
rapid delivery of Na+ and Cl- to the macula densa due to high systemic blood pressure
172
What happens in response to tubuloglomerular feedback?
decreased releae of Nitric oxide by juxtaglomerular apparatus causes constriction of afferent arterioles
173
What effect does tubuloglomerular feedback on GFR?
decreases GFR
174
What is the major stimulus for neural regulation?
increase in activity level of sympathetic nerves releases norepinephrine
175
What happens in response to neural regulation?
constriction of afferent arterioles through activation of alpha 1 receptors and increased release of renin
176
What effect does neural regulation have on GFR?
decreases GFR
177
What is the major stimulus for hormone regulation, angiotensin II
decreased blood volume or blood pressure stimulates production of angiotensin II
178
What happens in response to angiotensin II
constriction of afferent and efferent arterioles
179
What effect does angiotensin II have on GFR?
decreases
180
is the major stimulus for hormonal regulaton, Atrail Natriuretic peptide (ANP)
stretching of atria of heart stimulates ANP
181
What happens in response to Atrial Natriuretic peptide
Relaxation of mesangial cells in glomerulus increases capillary surface area available for filtration
182
What effect does Atrial Natriuretic Peptide have on GFR?
increases GFR
183
Explain the tonicity at the PCT
the active removal of ions and organic nutrients produces a continuous osmotic flow of water out of the tubular fluid. This reduces the volume of filtrate but keeps the solutions inside and outisde the tubule isotonic
184
the vasa recta maintaisn the ____ of the renal medulla?
concentration gradient
185
Explain the fluid dynamics of an isotonic solution
will remain in the ECF, has no effect on plasma osmolarity (wont go into cell, no gradient fro H2O to move). -increase blood volume but cell volume wont increase
186
Where is the precursor for ADH located?
made in the hypothalamus and stored in vesciles in the posterior pituitary
187
____ in the hypothalamus regulate the amount of ADH released in response to changes in the osmotic pressure of plasma.
Osmoreceptors
188
What do osmoreceptors sense?
- increase in Na+ concentration in ECF
- increase in osmolarity
| remember plasma is "onderdell" of ECF
189
Explain how osmoreceptros generate action potential to trigger the release of ADH
- osmoreceptors have "stretch -inhibited" or shrink activated cation channels
- Hypertonic stimulation provokes cell shrinking and increases the proportion of active cation channels. The resulting increase in positive charge influx depolarizes the membrane and increases neuronal action potential firing frequency.
| shrink becasue H2O is coming out of them due to high osmolarity in ECF
190
from the mechanism of osmoreceptros we understand that as osmolarity increases, ADH release ____
increases
191
Where does ADH act?
on the last part of the convoluted distal tubule and the collecting duct
192
What does ADH do at the DCT and collecting tubule
stimulates the insertion of aquaprin 2 containing vesicles into the apical membrane of the principle cells
193
What does the insertion of aquaporin 2 channels allow?
water can move from the tubule into the collecting duct cell. The basolateral membrane is always relateively permeable to water,thus water can now move via osmosis back into the blood
194
describe the signalling pathway of ADH
1. ADH/vasopressin binds to membrane receptor
2. Receptor activates cAMP second messenger
3. Cell inserts AQP2 water pores into apical membrane
4. water is absorbed by osmosis into the blood
195
What is the osmolarity of urine when ADH is present
very concentrated approx 1200 mOsmol. -same as at the lower medulla of descending loop of Henle
196
What other factors besides osmoreceptors can cause a release of ADH?
a decrease in blood pressure / blood volume
197
Explain how a decrease in blood pressure or volume stimulus leads to increased ADH release
- decreased blood pressure or volume inhibits baroreceptor activity in atrium and large vessels
- this stimulates ADH release
198
If water is reabsorbed due to ADH what does this do to osmolarit and plasma volume
decreases osmolarity, increases plasma volume
199
Explain the body’s response to high plasma osmolarity
- high plasma osmolarity | Low effective circulating volume
- thirst increases
- increased ADH release
- water is ingested
- increase in water reabsorption
- water is retained
- normal plasma osmolarity | normal effective circulating volume
200
Explain the body’s response to low plasma osmolarity
- low plasma osmolarity | high effective circulating volume
- thirst decreases
- decreased ADH release
- decrease in water reabsorption
- water is lost
- normal plasma osmolarity | normal effective circulating volume
201
What is the renin angiotensin system responsible for?
- important in maintaining sodium balance
- Also important in blood pressure regulation
202
Where is the juxtaglomerular apparatus found
Where the distal tubule abuts the glomerulus
203
Explain what the juxtaglomerular apparatus consist of and what their functions are
1. Macula densa cells - respond to a decrease in NaCl content by increasing prostaglandins
2. Juxtaglomerular (granular) cells in the afferent arteriole release RENIN
3. A decrease in pressure in afferent arteriole also acts on the juxtaglomerular cells cause the release of renin
204
What do the macula densa cells do when they detect high sodium content
Construct afferent arteriole
205
What are the triggers for renin release?
- low NaCl concentration in the distal tubule (Na+ depletion)
- decreased perfusion pressure (by granular cells themselves)
- increased sympathetic activity (e.g. via baroreflex)
I.e low blood pressure, low blood volume or low Na- content
206
What is the main purpose of the renin angiotensin system?
Retain Na+ in the body
207
Explain the signaling pathway once renin is released by the JC
Angiotensin is broken down by renin to angiotensin 1
Angiotensin converting enzyme (ACE) breaks down angiotensin 1 to angiotensin 2
Angiotensin two causes vasoconstriction, aldosterone release
This results in na+ retention ( increased sodium and water reabsorption in proximal and distal convoluted tubules )
It also stimulates thirst and salt intake
208
Where is aldosterone related from
Adrenal cortex in response to angiotensin 2
209
Where does aldosterone act on?
On distal tubule and collecting ducts to increase transcription of sodium potassium atpase
210
If aldosterone acts to transcribe more na/k Atpase what effect does this have on reabsorption and secretion?
Increased sodium reabsorption and potassium excretion
(Hence water reabsorption may also increase via osmosis so long there is some ADH present)
211
List the steps of the renin- angiotensin aldosterone system
1. Dehydration, na+ deficiency or hemorrhage
2. Decreased blood volume
3. Decrease in blood pressure
4. Juxtaglomerular cells of kidneys active
5. Increased renin
6. Angiotensinogen from liver broken down by renin
7. Increased angiotensin 1
8. ACE from lungs breaks down angiotensin 1
9. Increased angiotensin 2 - 10. Vasoconstriction of arteriole - 14. Blood pressure increases until it returns to normal
10. Adrenal cortex active
11. Increased aldosterone
12. Kidneys increased Na+ and water reabsorption
13. Increased blood volume
14. Blood pressure increases until it returns to normal
212
Explain the body’s response to an increased intake of NaCl
1. Increased intake of NaCl
2. increased plasma concentrations of Na+ and Cl-
3. Increased osmosis of water from intracellular fluid to interstitial fluid to plasma
4. Increased blood volume
5. Increased stretching of atria of heart
6. Increased release of atrial natriuretic peptide
5. Decreased release of renin by juxtaglomerular cells
6. Decreased formation of angiotensin 2
7. Increased glomerular filtration rate and decreased release of aldosterone
8. Reduced reabsorption of NaCl by kidneys
9. Increased loss of Na+ and Cl- in urine (natriuresis)
10. Increased loss of water in urine by osmosis
11. Decreased blood volume
213
How do ACE inhibitors work?
decreasing Na+ and H20 reabsorption, reducing blood volume - can lead to edema
214
Salt vs water balance, which system controls what?
- ADH important in maintaining WATER balance
- Renin-Angiotensin-Aldosterone system (RAA) - important in maintaining SALT balance
!!! The two systems allow for independent control of water and salt levels in the body
215
Fluid loss is ___ motic
Isosmotic
216
Blood loss is sensed by what cells?
Sensed by juxtaglomerular cells and atrial baroreceptors
217
What do the kidneys do in response to blood loss
Increased release of renin - angiotensinogen in blood increases angiotensin 2 in blood - adrenal cortex liberates aldosterone which increases blood volume AND/OR angiotensin 2 causes blood vessels to constrict causing increased systemic vascular resistance - increased blood volume and resistance causes increased blood pressure
218
What response do the baroreceptors in the heart elect in response to blood loss
1. decreased stretch causes decrease in nerve activity to Hypothalamus and posterior pituitary
2. Increased ADH in blood
3. Kidneys conserve salt and water, blood vessels constrict
4. Increase systemic vascular resistance leading to increased blood pressure
1. Decreases rate of nerve impulses to CV central in medulla
2. Increases sympathetic stimulation and hormones from adrenal medulla
3. Heart rate and contractility increases, blood vessels constrict
4. Increased blood pressure and increases resistance leads to increased blood pressure
219
What is atrial natriuretic Peptide responsible for?
Rid Na+ and H2O, opposite to RAAS
220
When is ANP releasesd?
In response to atrial stretch of heart to due increase blood pressure
221
ANP acts to reduce?
Reduce renin, ADH, aldosterone release, increase GFR
Reduces Na+ and water reabsorption
222
In response to a hemorrhage, list the bodies response signals/regulation from most rapid to least.
1. Blood pressure
2. Osmolarity
3. Restore blood volume
4. Blood cells
