Urinary systems Flashcards
1
Q
What separates intracellular and interstitial fluid
A
cell membrane
2
Q
hat separates interstitial fluid and blood plasma
A
endothelial cells in the capillary wall
3
Q
Why is pH effected when you try and regulate electrolyte balance
A
due to the movement of H+
4
Q
What are the 2 components of extracellular fluid
A
interstitial fluid (found between cells in ordinary tissues) and blood plasma (part of the blood apart from the red blood cells and white blood cells).
5
Q
How much of a 70kg human is water
A
60%
6
Q
How much water does ICF and ECF contain
A
ICF - 2/3 of total
ECF - 1/3 total
7
Q
how much of the total volume of ECF does the interstitial fluid account for
A
3/4
8
Q
What causes the total water % to vary
A
the amount of adipose tissues (lipid rich cells) present because it has a low water content
9
Q
how is osmotic equilibrium between ICF and ECF maintained
A
movement of water between the 2
10
Q
what is the movement of water between IF and plasma
A
isosmotic - water moves freely
11
Q
How can capillaries achieve filtration or reabsorption
A
if the correct hydrostatic and osmotic pressure is present to pass through their thin walls
12
Q
osmotic pressure in human plasma
A
300 mOsm
13
Q
difference in osmotic pressure between IF and plasma
A
plasma is 1.5 mOsm high than IF - does not disturb osmotic state
14
Q
can water move freely between ECF and ICF
A
no - osmolarity inside and outside cell is different so transporter is needed
15
Q
Concentration of surrounding in freshwater animals
A
surroundings have a low concentration of solutes - hyperosmotic
16
Q
where are the major sites of ion and water exchanges
A
skin (sweat), respiratory system (dry and wet during breathing), digestive tract (water and fluid absorption) and excretory system (urine, faecal matter).
17
Q
What is osmoregulation
A
the movement of water and solutes to maintain an isosmotic state
18
Q
How do sponges and cnidarians carry out osmoregulation
A
process with the lack of a circulatory system as they are in direct contact with water (bulk-flow), hence becomes easier for them to regulate and exchange.
19
Q
What does the wall of a sponge contain to help with osmoregulation
A
full of pores that propel water into the spongocoel and out through the osculum.
20
Q
What is the outer covering of a freshwater fish called
A
an integument
21
Q
Why does an integument cause issues for osmoregulation
A
integument is impermeable to water, therefore lack direct contact and exchange with the external environment
22
Q
Environment of freshwater fish
A
environment low in salt ions, however it has a higher concentration of salts in its body, and thus hyperosmotic to the environment
23
Q
What happens to the salts from the freshwater fish
A
eventually lost to environment and water enters, via gills
24
Q
How much water do goldfish take in a day
A
up to 30g/day, which is essentially 1/3rd of it body weight
25
Why do fish need to expel water
because they take up a lot, too much can dilute blood and cause other problems so energy is spent to expel water, salts are lost as a consequence
26
How do freshwater fish take up salts
via active transport. The transporters that are in place take up Na+ and Cl- and loose bicarbonate and H+ (electroneutral), with the help of ATP.
27
What are porins
similar to ion channels but permit the passage of large molecules.
28
What are aquaporins
Aquaporins are water channels in the plasma membrane, each aquaporin molecule transport 3 billion water molecules/second.
29
What happens if a membrane lacks aquaporins
water crosses the membrane 5-50 times slower.
30
Physiological roles of aquaporins
urine formation, production of aqueous humor of the eye, secretion of tears and sweat.
31
What are the 2 types of aquaporins
transcellular (through the cell membrane) or paracellular (across different compartments).
32
How do cells control their volume
transporting solutes across the plasma membrane, causing changes in osmotic pressure that induce movement of water.
33
What is the epithelium of a hummingbird
of a single layer of cells bearing microvilli on the apical membrane.
34
What must dissolved sugar molecules (e.g., glucose and fructose) do
cross the epithelium from the intestinal lumen to the blood.
35
What is ingested preformed water
water where the sugar molecules have been dissolved in
36
When is metabolic water formed
when organic food molecules are aerobically catabolized (e.g., glucose oxidation).
37
How is water gained
eating, drinking and cells produce it
38
Air entering the nose
warmed and humidified by heat. The nasal passages are cooled by evaporative water loss, leading to a flow of cool air.
39
What happens during expiration
the air is cooled and leads to a loss of water, wetting the nasal passage.
40
How else can water be excreted
through the faecal route, food is ingested that contains preformed water, and is excreted through this route.
41
How are desert kangaroo rats adapted to conserve water
More concentrated urea, less water loss and drier faeces
42
Lab rats v desert kangaroo rats experiment
where these rats were given 0 preformed water and they were given barley grain. They made metabolic water to survive. Desert kangaroo rats had a net gain of metabolic water compared to the lab rats.
43
What is osmotic regulation of blood plasma
is the regulation of osmotic pressure of an organism’s body fluids, detected by specialized receptors to maintain homeostasis of the organism’s water content
44
What is ionic regulation of blood plasma
Maintenance of the concentration of various ions in the bod fluids relative to one another. The urinary system plays a key role in this process.
45
What is volume regulation of blood plasma
Cell volume regulation is an important homeostatic function, defining not only cell shape but balance between the ICF and ECF.
46
What do obligatory responses cover
responses of an animal to factors that are beyond their physiological control (physical factors)
47
What are related responses
physiologically controlled and required for maintaining the internal homeostasis.
48
What is the linear line on a blood osmotic pressure v ambient osmotic pressure graph
isosmotic line
49
How does an osmotic conformer and an osmotic regulator differ on a graph
A perfect regulatory won’t follow the trend of the isosmotic line. However, the osmotic conformer will follow the trend of the isosmotic line
50
Osmotic pressure of osmotic conformers
have the same osmotic pressure as the externa environment
51
Osmotic pressure of osmotic regulators
keep osmolarity constant regardless of changes in the external environment.
52
What is the disadvantage of osmotic conformers
the cells may not have the ideal solute concentration for metabolism.
53
What is the disadvantage of osmotic regulators
they utilize too much to keep the internal solute concentration constant.
54
How do animals display features of both an osmotic conformer and a regulator
the regulation is limited to ranges of external osmotic pressure
55
Example of an osmotic regulator
shrimp
56
example of an osmotic conformer
mussel
57
When do crabs regulate and conform
when FW animals face brackish waters, they regulate in FW but conform in SW.
58
What is the extracellular space in animals dominated by
Na+ and Cl-
59
What is the extracellular space in SW dominated by
Na+ and Cl-, followed by reduced levels of K+, Mg2+ and Ca2+.
60
What ions dominate ionconformers
high levels of Na+ and Cl- like in SW
61
Ions present in ionregulators
low levels of Na+ and Cl-
62
What do both SW and osmoconformers have
have the same osmolarity but different solute profile
63
What is hemolymph
the circulating fluid in an open circulatory system that flows through blood vessels
64
Hemolymph in FW crabs
crabs is hyperosmotic to the surrounding water. Osmosis allows water to move in which is eventually lost as urine
65
Stability of animals in open ocean
they live in environment that are uniform and stable in their water-salt composition
66
Salinity of water calculation
number of grams of dissolved inorganic matter in a Kg of water.
67
Salinity and osmotic pressure of SW
34g/Kg, and its osmotic pressure is nearly 1000 mOsm
68
Salinity and osmotic pressure of FW
salinity less than 0.5g/Kg, and has an osmotic pressure of 0.5-15 mOsm.
69
How is volume regulation a challenge for FW animals
because there is a constant influx of water into the organism due to an osmotic gradient.
70
How is osmotic regulation an issue for FW animals
The water that enters, dilutes the blood and reduced osmotic pressure within the ECF.
71
How is ion regulation an issue for FW animals
Due to excretion of excess water ions are constantly lost to the external environment
72
Where do FW fish reabsorb ions and why
in their kidneys because the uptake of ions from a highly concentrated solution requires a lot of energy
73
What are freshwater animals to their environment
hyperosmotic to environment - gain of water, loss of ions
74
In FW, what are the consequences of rapid water uptake
the faster water is lost by diffusion and the more energy that is spent to counteract this
75
Wat 3 factors determine the rate of exchange
permeability, surface area to volume ratio and magnitude of gradient.
76
How do FW counteract that large water intake
by excreting copious amounts of urine
77
What does the rate of water influx in FW resemble
the rate of urinary excretion - because urine production balances osmotic water gain
78
What is the urine of FW fish compared to their blood
is hypoosmotic (low concentrations of Na+ and Cl-) to their blood. This is defined as the U:P ratio (Urine to plasma).
79
What does a U:P of less than 1 mean
that the blood osmotic pressure is high due to lots of urine production.
80
What does a U:P of less than 1 for an ion mean
that the large amounts of urine production tend to raise plasma concentrations for that particular ion
81
Function of the kidneys in FW animals
solve the problem of volume regulation by excreting urine but aid in ionic and osmotic regulation by maintaining high osmotic pressures and an increased ion concentration in the blood
82
Function of gills
active not only in gas exchange but also in ion transport, excretion of nitrogenous wastes, and maintenance of acid-base balance.
83
What does the epithelium which separates the blood from external water consist of
mucous cells, pavement cells and chloride cells
84
What does the epithelium of the lamella consist of
pavement cells and mitochondria - suited for respiratory exchange
85
What does the epithelium covering the gills contain
chloride cells, mitochondria and enzymes that assist with salt transport.
86
How do FW fish replenish lost Na+ and Cl-
active transport
87
Where does active ion transport occur and what does it require
the gills. Needs ATP
88
How does Cl- enter the blood from the environment FW fish
The Cl- pump typically exchanges HCO3 for Cl- (electroneutral).
89
How does Na+ enter the blood from the environment - FW fish
The Na+ pump exchanges H+ (protons) for Na+ or Nh4 (ammonium ions).
90
How are HCO3 and H+ produced in FW fish for ion exchange
produced by anaerobic catabolism, being formed by metabolically formed CO2 and H2O.
91
How is Na+ homeostasis maintained in mammals
through Na+ reabsorption via a variety of Na+ transport proteins with mutually compensating functions, which are expressed in the nephrons.
92
How is Na+ homeostasis achieve in FW fish
through the skin gill ionocytes, namely Na+/H+ exchangers. Expressing H+ ATPase rich cells and Na+ and Cl- Co-transporters.
93
What is the challenge in marine animals
osmotic gradient is higher, water moves in the opposite direction to fresh water fish
94
Movement of water in marine fish
sea water has a high salt concentration, causing high salt influx, when salt is expelled the water is lost so try to reabsorb as much water to maintain ICF osmotic pressure
95
movement of substances with respect to gills
substances can move in and out as they are permeable to water
96
How have organisms that live on land adapted to secrete salt
have glands e.g., sea birds have them in nasal passages
97
How have dogfish adapted
has a low conc of Na+ and Cl-, but urea and TMAO increase osmotic pressure causing influx of water from external environemnt. Salt lost through salt glands
98
Permeability of integuments
poorly penetrable to water
99
urine of marine fish
because they conserve water they form isosmotic urine
100
Role of kidneys in marine fish
get rid of excess salt
101
What are stenohaline animals
tolerate a narrow range of salt concentration
102
What are euryhaline animals
tolerate wide variation in osmolarities
103
What are the functions of the urinary system
1. Removal of waste products (produced by cellular metabolism)
2. Regulation of volume and solute concentration of blood plasma, blood volume; pH
3. Elimination of waste products into the environment
104
Kidney function
urinary production, excretion and regulation
105
Ureter function
urine transfer to bladder
106
bladder function
urine storage, elimination
107
urethra function
urine release, elimination
108
Location of the kidneys
on either side of the middle on the posterior wall of the abdomen. Lie behind the parietal peritoneum = retroperitoneal. Surrounded by fat (adipose tissue - protection)
109
Cortex of the kidney function
corticosteroids (aldosterone), sodium and water retention, increase blood pressure and volume.
110
Medulla of the kidney function
adrenaline and noradrenaline. Fight or flight response
111
Left v right kidney function
(T12-L3): the left kidney is located slightly higher than the right because of the liver (L =lumbar, T = thoracic)
112
What protects the kidney
fat, fascia, ribs 11 and 12
113
When does Floating kidney (wandering kidney or nephroptosis) occur
when collagen fibres and suspensory fibres that are holding kidney are damaged.
114
What makes up the renal capsule and renal fascia
collagen
115
Shape of kidney
Indented ovoid – bean shaped
116
renal hilum structures (enter and exit site)
renal vein, renal artery and renal pelvis
117
Blood supply of kidneys
20-25% of cardiac out put
118
How are kidneys indented
small lobes have come together
119
What is an anomolie of kidneys
horseshoe kidney
120
Structures of the kidney
renal cortex, renal medulla, renal papilla, renal pyramids, renal column, renal artery/vein, renal pelvis
121
What does the renal lobe contain
the nephron
122
Structures of nephron in the cortex
Bowman's capsule, proximal convoluted tubule, distal convoluted tubule
123
Structures of nephron in the medulla
loop of henle, collecting duct, pelvis
124
What are the ureters
hollow muscular tubes, propel urine from the kidneys to the bladder
125
length of the ureters
25-30cm
126
Location of ureters
in both abdomen and pelvis
127
Anomolie of ureter
duplex ureter (bifid ureter) - 1 in 125 people
128
How do ureters enter the bladder
obliquely
129
Ureter when the bladder is full
prevents backflow of urine into the ureters. Compression closes off the ureters acting as a valve
130
Apex of the bladder
points towards the public symphysis
131
Fundus of the bladder
opposite the apex and formed by the posterior wall
132
Capcity of the bladder
0.75 l
133
Female urethra length
4-5cm
134
Location of the female urethra
Passes through the pelvic floor and opens anterior to the vagina
135
Male urethra length
20cm
136
Male urethra shape
S-shaped
137
Parts of the male urethra
pre-prostatic, prostatic, membranous, penile
138
Male urethra flow
Urine flows down through catheter to empty the baldder of urine
139
Internal male urethra sphincter
junction between the bladder urethra
140
Male internal urethra sphincter function
prevents reflux of semen into the bladder
141
Location of male urethral sphincter
inferior to the prostate
142
Female internal urethral sphincter
Junction between the baldder and urethra ‘Debate’
143
Female external urethral sphincter
immediately inferior to the internal urethra sphincter
144
Function of mammalian kidney
regulate the composition of body fluids (osmotic balance), excretion of waste in the form of urine, pH balance, hormone production (kidneys produce a hormone that stimulate RBC production) and regulate blood pressure.
145
What processes contribute to the formation of urine
filtration, reabsorption, secretion and excretion
146
What happens to the water/solutes once they have left the arterioles into the kidney
they enter lumen of bowmans capsule forming an ultrafiltrate
147
What are the renal tubes lined with
cells so ions and water can freely move, passing through this cell layer (reabsorbed)
148
Where are certain types of molecules secreted from and to
From the IF into the proximal tubule to be excreted as waste
149
What does the glomerular filtrate contain
contains all the constituents of the blood except blood cells and proteins.
150
What % of water and solutes are removed from the plasma
15-25%
151
At what rate is the filtrate produced
180L/day
152
Function of afferent arteriole
transports blood towards the glomerulus
153
Function of efferent arteriole
transports the blood away from the glomerulus
154
Network of capillaries inside the glomerulus
with thin walls allowing easy movement of substances. These loops are also referred to as glomerular tufts. The key here is the constant blood supply.
155
Layers of the glomerulus
Endothelial cells basement membrane and the podocytes. This is the filtration barrier.
156
Function of filtration barrier
keep blood and protein into the body and allow the passage of small molecules into the urine
157
What are the podocytes
modified epithelial cells that provide structural support
158
Glomerulus size selectivity
molecules less than 1.8 nm can be easily filtered (water, sodium, insulin and glucose). Molecules more that 3.6 nm are not filtered (haemoglobin).
159
Glomerulus charge selectivity
negatively charged molecules cannot pass that easily, as all the three layers shown above contain negatively charged glycoproteins.
160
What does filtration of the blood depend on
hydrostatic and oncotic pressure
161
What is hydrostatic pressure
is the pressure that the fluid exerts on the walls of the compartment, either the walls of the capillary or the Bowmans capsule (pushing force).
162
What is oncotic presssure
is the pressure exerted by the plasma protein on the walls of the compartment in which they are contained (pulling force).
163
What is the clearance
The amount of fluid cleared completely of a certain substance.
164
What happens if the hydrostatic pressure is greater in the capillary than the Bowman's capsule
fluid is pushed out
165
Why does the blood have a greater osmotic pressure than the Bowman's capsule
due to the presence of proteins
166
Oncotic pressure present in capillaries
* The oncotic pressure present in the capillaries tend to pull fluids back in. The balance between the forces influences rate and direction of fluid movement.
167
What is the net filtration pressure
Pressure favouring filtration minus the pressures opposing filtration
168
What is the net hydrostatic pressure
the glomerular capillary pressure (hydrostatic pressure within the capillaries) minus the Intracapsular pressure (hydrostatic pressure within the lumen of the Bowmans capsule).
169
net filtration pressure formula
net hydrostatic pressure minus the colloid osmotic pressure (oncotic pressure). This will give you the net filtration pressure.
170
Why do we calculate the glomerular filtration pressure
to identify if an individual is suffering from kidney problems.
171
What is the juxtaglomerular apparatus (JGA)
a specialized region which is significant for sensing the blood pressure/flow into the kidney and producing hormones such as renin.
172
What is renin
is a hormone, significant in blood pressure regulation and fluid balance.
173
What comes into contact at the JGA
is a region where the afferent arterioles come into contact with the distal tubule.
174
What is present on the outside of the afferent arterioles
JG cells that can sense blood pressure.
175
What happens at the point of contact with the distal tubule
modified cells in the distal tubule, Macula densa cells sense changes in flow and an Na+ concentration of the intertubular fluid.
176
What happens when systemic blood pressure decreases
a decreased stretch of the JG cells which release renin, renin will increase blood pressure back to normal.
177
What happens when the filtrate has a decreased flow rate
the macula densa cells sense this, leading to vasodilation of the afferent arteriole and renin secretion by the JG cells. Renin will return flowrate back to normal
178
What is the purpose of the JGA
connection between, blood pressure, osmolarity, blood flow and Na+ concentration
179
Where does the filtrate go after the Bowman's capsule
proximal tubule
180
function of the proximal tubule
specialized for transport and is the area where most reabsorption occurs.
181
How are epithelial cells of the tubule unique
are not very permeable to lots of substances -> they have lots of transport mechanisms on either side of the cell to help regulate the movement of ions.
182
Function of the tight junctions in the tubule epithelial cells
prevent paracellular transport, and contain a certain polarity allowing certain substances to move across, such as proteins and pharmaceutical agents.
183
What do the epithelia in the PT contain for reabsorption
epithelia have microvilli, lots of mitochondria and a large surface area.
184
How much of the filtered fluid does the PT reabsorb
80%
185
How much of the filtered fluid does the loop of henle reclaim
5-10%
186
Loop of henle function
water conservation
187
What does reabsorption maintain
fluid and electrolyte balance in the system.
188
How else is urine modified
through secretion
189
what does secretion use
transporters found in the epithelial cells that line the lumen of the PT.
190
What substances move into the PT from the blood
H+, K+, toxins and pharmaceutical drugs. Requires energy
191
osmolarity of the fluid at the end of the PT
300 mOsm - isosmotic to the IF and plasma
192
How thick is the wall of the tubule
one cell layer thick
193
How are the epithelial cells in the tubule specialised
for transport, bearing a dense pile of microvilli on their luminal (apical) surfaces.
194
How are epithelial cells tied together
by leaky junctions
195
What occurs in all sections of the kidney tubule
, Na+ diffuses into the epithelial cells from the tubular fluid because there is an electrochemical gradient favouring this movement.
196
In the early PT how does most Na+ entry occur
occurs by means of co-transporters that bring about secondary active transport of glucose and amino acids because the fluid is rich in glucose and amino acids
197
Permeability of the descending limb
is very permeable to water because it doesn’t have tight junctions.
198
Epithelium cells of the descending limb
have no active transport of solutes, highly permeable to water and impermeable to ion and urea.
199
Ascending limb characteristics
, impermeable to water, permeable to ions and impermeable to urea. The thick segment of the AL has active transport of ions.
200
primary urine bicarbonate and proton concentration
urine concentration of bicarbonate is high but concentration of protons is low
201
Reabsorption of bicarbonate ions
around 80% of bicarbonate takes place in the proximal convoluting tubule and continues in downstream sections of the nephron
202
Movement of protons
moved in the opposite direction to bicarbonate ions, causing acidification of the intertubular fluid
203
Where does the final tuning of urine acidification occur
distal tubule and the collecting duct
204
What are alpha intercalated cells
acid-secreting
205
What are beta intercalated cells
base-secreting
206
What do alpha and beta secreted cells possess
various sensors for bicarbonate, CO2 or proton concentration
207
What do signals from the bicarbonate, CO2 and proton concentration sensors do
modulate expression, abundance in the plasma membrane or activity of transporters, pumps and channels in these cells. These processes are also under hormonal control (aldosterone, angiotensin II, etc.)
208
Purpose of counter current multiplication
to create concentrated urine with the loop of Henle (LOH).
209
Water reabsorption in the decending limb
the osmolarity (concentration of Na+) in the IF is high, water will move out from the DL into the IF, equilibrating the osmotic pressure.
210
Changes in the Na+ concentration in the descending limb
increases as water moves out
211
How did Na+ enter the IF
active transport
212
Movement of Na+ in the ascending limb
original high Na+ conc, Na+ pumped into IF
213
What is the osmolarity difference between IF and tubular fluid
200mOsm
214
Why is Na+ transported into the IF from the ascending limb
* Therefore Na+ is transported out from the AL into the IF creating a 200 mOsm difference. Due to the transport of Na+, the IF has an osmolarity of 400 mOsm and the filtrate in the AL has an osmolarity of 200 mOsm (200 mOsm difference).
215
Water movement out of the DL
Water will continuously move out of the DL until it equilibrates with the IF, this means that the osmolarity in the DL and IF will be the same (400 mOsm).
216
Why does the DL and IF equilibriate
because when water moves out into the IF, the filtrate in the DL gets more concentrated (increased osmolarity).
217
Effect on osmolarity of water reabsorption
no change in the IF
218
Why does the movement from the DL to the AL take place
due to new isosmotic filtrate entering the DL from the PT.
219
osmolarity of the filtrate in the DL and bottom of AL
is isosmotic to the IF, therefore there is no concentration gradient to transport Na+ passively so Na+ is transported to IF
220
What happens to the Na+ present at the top of the AL
be transported into the IF, to create that 200 mOsm difference, and whatever is remaining will get transported into the collecting duct (CD).
221
Osmolarity in the medulla
The osmolarity increases the deeper you move into the medulla, and this is because of counter current multiplication.
222
Why is it called counter current multiplication
Counter current because the filtrate moves in opposite directions, and multiplication because of the flow and mechanisms involved to concentrate urine (gradient is multiplied).
223
How does counter current multiplication aid water reabsorption in the collecting ducts
the IF will have an increased Na+ surrounding the CD, and thus water will move out into the IF due to a concentration gradient.
224
How is the LOH show an increase in osmolarity
by the observing the size difference between juxtamedullary nephrons (JMN) and cortical. , where desert animals have a longer LOH than a lab rats, as evolution within than environment has favoured water conservation leading to more water reabsorption
225
What are vasa recta
are specialized capillaries found around the JMN
226
What do the capillaries in the vasa recta specialize in
creating this hyperosmotic environment to draw water out.
227
Descending vasa recta
Blood coming down from the cortex into the medulla is in contact with increased osmolarity IF. The Na+ will diffuse from the surrounding IF into the vasa recta.
228
Ascending vasa recta
concentrated blood (increased osmolarity) will move towards the AL and will lose that concentrated Na+ to the diluted IF
229
Descending vasa recta - H2O
Dilute blood flowing from the cortex into the medulla will lose water to the concentrated IF (increased osmolarity).
230
Ascending vasa recta - H2O
Concentrated blood flowing towards the AL will gain water from the IF due to its increased osmolarity in the capillary
231
What does the increased concentration gradient across the nephron create
there is constant water reabsorption, which creates concentrated urine. benefits the CD, which promotes water reabsorption from the CD.
232
Movement of urea
move freely across the membranes. Urea can move across the AL, CD and the IF. Due to this movement and the constant influx of newly filtered urea, creates a concentration gradient, promoting water reabsorption from the DL.
233
Transport proteins in the collecting ducts
. UT-A1 and UT-A3, expressed by epithelial cells of the CD, aid in transport of urea from the CD to the IF.
234
Affect of vasopressin
upregulates expression of UT-A1 and UT-A3, increasing the rate of urea transport.
235
What does increased osmolarity detected by osmoreceptors cause
release of vasopressin
236
Angiotensin II effects
acts on receptors in the hypothalamus, causing vasopressin release
237
How does a decreased water content in the blood effect the heart
reduced venus return detected by baroreceptors leading to vasopressin release
238
Mechanism of vasopressin
Vasopressin upregulates translocation of aquaporin (AQP-2) receptors on the apical side of the plasma membrane in the distal convoluted tubule and CD. On the basolateral side of the membrane, you always have presence of aquaporin-3 and 4. When osmolarity in the IF increases (decrease in water content), Vasopressin is released and upregulates translocation of AQP-2, leading to increased water reabsorption in the IF.
239
What is renin
an enzyme secreted by JGA cells
240
What cells are present when the Bowmans capsule meets the distal convoluted tubule
specialized cells e.g., JGA cells and macula densa
241
Renin secretion - baroreceptor mechanisms
Baroreceptors can detect a change in pressure within your afferent arterioles. If the bp in the afferent arterioles decrease, the baroreceptors will send a signal to the JGA cells to release renin. Renin will carry out its function an increase blood pressure
242
Renin secretion - sympathetic nervous system
There are certain nerves that stimulate renin release during sympathetic activity (fight/flight). Metabolism increases and hence renin is released.
243
What do macula densa cells do
sense Na+ in the distal convoluted tubule
244
What does increased Na+ mean about blood pressure
increased blood pressure
245
Decreased Na+ - macula densa cells
Macula densa cells will stimulate the JGA cells to release renin, which will increase your blood pressure. The increase in blood pressure, will increase your GFR and net filtration, leading to an increase in Na+ reabsorption.
246
How does renin work
Renin is an enzyme, which works on a substrate known as angiotensinogen, produced by the liver. Angiotensinogen gets into your blood stream. Renin breaks down angiotensinogen to angiotensin 1 which is converted by an enzyme (angiotensin converting enzyme) to angiotensin 2.
247
What does angiotensin stimulate
aldosterone
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What does aldosterone do
Aldosterone increases sodium reabsorption and potassium secretion in the distal convoluting tubule and the collecting duct.Intensified sodium reabsorption followed by Intensified water reabsorption, which increases the volume of blood and consequently, further raise of blood pressure.
