Arteries, Veins & Renal Phys (Topic 19-28) Flashcards
(306 cards)
1
Q
Arterioles are mainly made of what?
A
smooth muscle
2
Q
Arterioles are made of 3 layers, which are what?
A
- Endothelium
- Smooth muscle
- Connective tissue - mainly collagen fibres
3
Q
Where are arterioles located?
A
Within individual organs
4
Q
True or False
Arterioles are part of the microcirculation, controlling blood in a given organ
A
True
5
Q
What is the greatest contributor to total peripheral resistance?
A
Arterioles
6
Q
Why do we have such a significant drop in pressure in the arterioles?
A
7
Q
How is resistance determined?
A
It is proportional to 1/radius^4
8
Q
What are 2 ways resistance can increase?
A
- Tube length
- Viscosity of blood
9
Q
Which factor is the determinant of total peripheral resistance?
A
radius
10
Q
If we increase the radius of a tube, would there be more or less resistance?
A
Less
11
Q
If we decrease the radius of a tube, would there be more or less resistance?
A
More
12
Q
Is blood flow even across every organ and bone?
A
No
13
Q
From Rest to Exercising
Why is there no change in blood flow to the brain?
A
There is no need for the brain to get “extra” blood
14
Q
Why can we not have a massive amount of blood going to the brain?
A
Because the brain is a restricted space
15
Q
Why can we not have a lesser amount of blood going to the brain?
A
We need a minimum amount of blood for the brain to function, and O2 delivery
16
Q
How do the arterioles distribute blood to each organ?
A
via increasing and decreasing resistance through the vasoconstriction and dilation of the smooth muscle in the arterioles
17
Q
What are the 3 functions of the smooth muscle cell layer in the arterioles?
A
- Maintain the shape of blood vessels
- Set blood vessel diameter
- Regulating local blood flow within the organ
18
Q
How does SMOOTH muscle contract?
A
calcium-induced calcium release
19
Q
Are smooth muscle cells straight?
A
No
20
Q
Do smooth muscle cells have Z-lines? If not, what do they have instead?
A
- No z-lines
- Dense bodies, anchors for myofilament
21
Q
Where are the thick and thin filaments located in smooth muscles?
A
between dense bodies, on diagonal lines
22
Q
True or False
There are signals in place that can increase and decrease the action-myosin cross-bridge formation to cause vasoconstriction and vasodilation
A
True
23
Q
Can smooth muscle stay contracted without constant activation?
A
yes
24
Q
What is myosin light chain phosphorylation?
A
process that allows smooth muscles to stay contracted
- There is no tropomyosin covering the actin filaments
- calcium binds to specific are on the myosin, inducing ATP, inducing the myosin head to be ready for attachment again
25
Can the smooth muscle contract in different directions?
yes
26
What are the 4 functions of the Endothelial cells?
1. Line the heart and blood vessels
2. Prevent blood cell and platelet adherence
3. Control the exchange of fluid and nutrients
4. Secret vasodilator (nitric oxide) and vasoconstrictor (endothelin) substance
27
True or False
The endothelial cells in organs can tell the smooth muscle cells to either vasodilate or vasoconstrict
True
28
What is the process of endothelial cells increasing blood flow through Nitric Oxide?
(i) Endothelial cells produce L-Arginine (protein, amino acid)
- Nitric Oxide synthase (enzyme) will convert it to nitric oxide
Nitric oxide then diffuses into the smooth muscle cell
(ii) In the smooth muscle cell, the nitric oxide will activate guanylate cyclase
- Guanylate cyclase will convert GTP to cGMP
This will lead to vasodilation, which means decreased resistance and Increased blood flow!
29
The more cGMP will mean what?
increase the blood flow
30
How can we regulate the cGMP in the smooth muscle cell?
via PDE = Phosphodiesterase
- breaks down cGMP to GMP
- GMP converts back to GTP
31
In addition to Nitroic Oxide, what are examples of other drugs that can mimic its affect and increase blood flow via cGMP?
1. Nitroglycerin
- increases production of cGMP
2. Viagra
- Inhibit PDE to prevent the breakdown of cGMP
32
What happens if we touch Nitroglycerin as a healthy individual?
All our blood vessels dilate, causing us to pass out
33
How can we increase the amount of NO in our body to increase blood flow?
Dietary nitrate supplement
- beet root juice
34
Dietary nitrate supplements can convert NO3-NO2-NO within a few hours via our saliva, which will cause what 3 positive outcomes?
1. Fatigue resistance
2. Exercise performance
3. Exercise efficiency
35
What are the 2 ways blood flow is regulated?
1. Locally
(i) Active and reactive hyperemia - metabolite-dependent
(ii) Flow autoregulation (stretch-dependent)
2. Systemically
(i) Neural (SNS via norepinephrine)
(ii) Hormonal (epinephrine)
36
Locally, active and reactive hyperemia is dependent on what?
metabolite-dependent
37
Locally, flow autoregulation is dependent on what?
stretch-dependent
38
Systemically, Neural regulation is dependent on what?
SNS via norepinephrine
39
Systemically, Hormonal regulation is dependent on what?
epinephrine
40
What is the Local's blood regulations goal?
To cause vasodilatation in specific organs to receive more blood flow
41
What is the systemic blood regulation goal?
To regulate the MAP
42
Is the local control of blood flow dependent on nerves or circulating hormones?
No, it is caused by signals within an organ, controlling the blood flow to sed organ
43
What does hyperemia refer to?
Increase in blood flow
44
What does active hyperemia look like?
- As tissue metabolic activity increases, the blood flow increases
- linear relationship
45
What are good examples of where Active hyperemia would occur during exercise?
- important in tissues with high but variable metabolic needs
ie, within the brain and skeletal muscle
46
What are the pathways of active Hyperemia?
Trigger = Metabolic activity increases (due to exercise)
-
Stimuli = decreased amounts of O2 in the (brain or skeletal muscles): this changes the metabolite concentrations, increases K+
-
Drives more NO production in the arterioles, causing smooth muscle to relax
-
causes vasodilation of arterioles, which leads to increased blood flow
47
Is active hyperemia a positive or negative feedback loop?
Negative
48
What are the pathways of REactive Hyperemia?
Trigger = Lack of blood flow (due to ischemia)
-
Stimulus = decreased O2 in the (brain or skeletal muscles): this changes the metabolite concentrations, increases K+
-
Drives more NO production in the arterioles, causing smooth muscle to relax
-
causes vasodilation of arterioles, which leads to increased blood flow
49
What is the difference between Active and Reactive hyperemia?
Trigger
50
What are good examples of where Reactive hyperemia would occur during exercise?
ie, Skeletal muscle and CARDIAC muscle (coronary artery), blood pressure cuff (at the doctor's)
When we contract our muscles, we pause blood flow for a brief period of time, and then we accumulate metabolites until the smooth muscle relaxes
51
What does Flow auto-regulation look like?
Blood flow to an organ is kept at a steady rate despite changes in blood pressure
- contact relationship with dips in extremely high and low pressures, aka flat line
52
Where would we see flow auto-regulation in the body?
kidney and brain
53
Does it matter if the pressure gradient changes in flow autoregulation?
No, it'll be kept steady no matter what
54
True or False
Flow regulation will change only in extremely high and low pressures
True
55
If blood flow is too high to the brain or the kidneys, what can happen to these organs?
damage the organs
56
Flow auto-regulation is controlled by what kind of response?
myogenic response
57
What is a myogenic response?
reflex response of arterioles to changes in blood pressure
- muscle response
58
In flow auto-regulation
if we increase arterial blood pressure, what is occurring?
leads to passive stretch of the arterial walls, which will increase arterial diameter to increase blood flow
59
What are the steps of the process of the myogenic response?
Arterial blood pressure increases
-
leads to passive distension of the arterial wall
-
stretch of smooth muscle cells
-
trigger an increase in cytosolic calcium inside the smooth muscle
-
cause contraction
-
Decreases blood flow
60
When we have flow auto-regulation due to myogenic response, we have 2 response outcomes which are what?
1. Passive response, of an immediate increase in blood flow
2. Active correction, delay of decreasing blood flow
61
Is flow auto-regulation via myogenic response a negative or positive feedback loop?
negative
62
True or False
Vasodilation is caused by the decreased stretch reflex activity
True
63
True or False
The systemic control of blood flow is regulated by neural and hormonal factors. If so, what are they?
True
- Neural: SNS
- Hormonal: Epinephrine, Angiotensin ll and Vasopressin
64
Is there any influence of the PNS on the blood vessels?
No
65
In the Systemic regulation of blood flow:
The SNS will produce what?
Norepinepherine
66
In the Systemic regulation of blood flow:
In the case of increased exercise, what is occurring?
Increased SNS activity
-
Many nerve action potentials stimulates the release of norepinephrine
-
Norepinephrine binds to α-adrenergic receptors on smooth muscle
-
Leading to vasoconstriction
67
In the Systemic regulation of blood flow:
In the case of decreased activity, what is occurring?
Decreased SNS activity
-
Few nerve action potentials stimulate the release of norepinephrine
-
Norepinephrine binds to β-adrenergic receptors on smooth muscle
-
Leading to vasodilation
68
Alpha adrenergic receptors are more prone to bind to what?
Norepinephrine
69
Beta adrenergic receptors are more prone to bind to what?
Epinerphrine
70
In the Systemic regulation of blood flow:
In the case of Increased Adrenal Medulla activity, what is occurring?
Release of epinephrine into plasma
-
Increased epinephrine binds to β-adrenergic receptors
-
causing vasodilation
71
Are there more β-adrenergic or α-adrenergic receptors?
α-adrenergic
72
True or False
By activating β-adrenergic receptors, there is less vasoconstriction than if only α-adrenergic receptors were active
True
73
β-adrenergic receptors lead to what kind of smooth muscle response?
Vasodilation
74
a-adrenergic receptors lead to what kind of smooth muscle response?
Vasoconstriction
75
In exercising muscle what are the 2 factors influencing on the vasculature while the SNS is activated during exercise?
1. Beta-adrenergic receptors
- to help reduce vasoconstriction
2. Metabolites override
- sympathetic vasoconstriction
76
While exercising (increased metabolic activity) The skeletal muscle will under go what from rest to exercise state?
- local active hyperaemia which will cause an increase in metabolites
- SNS will increase vasodilation through Beta-adrenergic receptors
77
While exercising The kidneys, Liver and digestive tract will under go what from rest to exercise state?
- increases SNS activity leading to increased vasoconstriction via a-adrenergic receptors
78
In skeletal muscles during exercise does blood flow increase or decrease from rest to exercise?
Increase massively
79
In the liver, kidneys and digestive tract during exercise does blood flow increase or decrease from rest to exercise?
decreases
80
In the brain during exercise does blood flow increase or decrease from rest to exercise?
No change but smaller percentage looking at the percentage from cardiac output point of view
81
What causes the rested heart to increases during exercise?
due to reactive hyperaemia
- where this temporary ischemia happening in the heart
- the heart is also contracting like skeletal muscles which will activate active hyperaemia
82
What are the consequences of SNS and metabolic regulation in arterioles when we are stressed?
- Increased SNS causes the release of NE which will inhibit vasoconstriction
The consequences are:
low blood flow in our capillaries which will
- decreases gas and nutrient exchange
- favour fluid reabsorption more than fluid filtration
83
What are the consequences of SNS and metabolic regulation in arterioles when we are exercising?
absolute cardiac output and MAP are both increasing
- MAP will decrease
- increases blood flow to skeletal muscle
- Increased gas exchange and nutrients
- favouring fluid filtration over reabsorption
84
If we are dehydrated, is our blood viscosity going to be thinner or thicker?
Thicker
85
What is sheer stress?
friction of blood flow in the arterioles
86
Lots of sheer stress in the endothelial cell causes the production of what?
NO induces vasodilation
87
Heat will induce what, vasodilation or vasoconstriction?
vasodilation
88
Heat will induce what, vasodilation or vasoconstriction?
vasodilation
89
Histamine release occurs when?
- when we have an injury, a cut or a wound
- When we have an allergic response
- sends cells to the area of injury
90
What are the capillaries?
They are a network of branches from the smallest end of the arterioles
91
What are capillaries made of?
- single layer of endothelial cells
92
What occurs at the capillaries?
gas and nutrient exchange
93
What is the pressure in the capillaries?
20-40 mm Hg
94
If the pressure in the capillaries is very low what would happen?
We could not move blood into the venules, as blood flows via pressure gradients, we would need the capillaries to create a pressure, which is not possible
95
True or False
The blood flow rate is constant throughout the vascular system
True
96
When is the total sectional area the greatest?
at the capilaries
97
Is the velocity of the blood flow going to be high or low moving through the capillaries?
low, 0.5 mm/sec
98
How would we calculate flow given velocity?
Flow = cross-sectional area x velocity
99
Do we need diffusion gradients to exchange gas and nutrients across the ECF
yes
100
What are the 4 ways substances can move across the capillaries?
1. Lipid soluble
- O2 and CO2
2. Small water molecules will pass through only at the cell junctions
- glucose and amino acids
3. Large water-soluble molecules will be transported via vesicular transport
- proteins
4. Large plasma proteins hardly leave the plasma
- albumin
101
What is capillary filtration?
fluid exiting the capillary
102
What is another way to talk about a water-filled pore?
cell junctions
103
What is capillary absorption?
fluid entering the capillary
104
What is the primary function of filtration/absorption?
Regulates the distribution of the ECF between the plasma and interstitial fluid
105
Are gases dependent on the cell junctions?
No, because O2 and CO2 can diffuse through the cell walls
106
What is hydrostatic pressure?
pressure induced by the fluid in a confined space
107
True or False
In capillaries, the hydrostatic pressure will equal the blood pressure
True
108
What is the Osmotic pressure?
pressure dictated by solutes dissolved in a substance
109
What dictates osmotic forces?
plasma proteins, aka albumin
110
Why does albumin play such an important role in filtration/reabsorption?
albumin stays inside the capillary; it cannot leave it
- It drives liquid back into the capillary
111
What 2 pressures/forces are dictating fluid movement out of the capillary?
1. Capillary hydrostatic pressure
2. Osmotic force (interstitial fluid proteins)
112
What 2 pressures/forces are dictating fluid movement INTO the capillary?
1. Osmotic force via plasma proteisn
- mainly this one
2. Interstitial fluid hydropstatic pressures
113
If the Net filtration pressure is positive what does that mean?
outward movement of fluid from the capillary into the interstitial space
114
If the Net filtration pressure is negative what does that mean?
Inward movement of fluid from the interstitial space back into the capillary
115
What would the standard capillary pressure be for the arterial end of the capillary?
37
116
What would the standard capillary pressure be for the venous end of the capillary?
17
117
What value would the osmotic force generated by albumin be?
25 always
118
What would the standard hydrostatic pressure of the interstitial space fluid be?
1
119
What would the standard pressure of the osmotic force of the interstitial space fluid be?
0
120
While exercising, we increase MAP and vasodilation for skeletal muscles, which will do what to the capillary pressure?
- Increase the capillary pressure
- The majority of the length of the capillary is going to favour capillary filtration
121
Why would we want to favour filtration during exercise for our skeletal muscle?
During exercise, our muscles need lots of glucose
122
While exercising, we increase MAP and vasoconstriction to the bone, kidney, and digestive tract, which will do what to the capillary pressure?
- Decrease capillary pressure
- The majority of the length of the capillary is going to favour capillary reabsorption
123
Why would we want to favour reabsorption during exercise for our bones, kidneys, and digestive tract muscle?
- We don't need glucose for the bone and other organs, therefore, favouring reabsorption allows the preservation of glucose for skeletal muscle
124
When we are dehydrated, what will happen be favoured filtration or reabsorption?
When we are dehydrated, we reduce cardiac output because our total plasma volume is going to drop, and so MAP will drop as well
- Capillary pressure drops as well, so we will favour reabsorption because that will draw fluid from our organs back to our plasma volume
125
What happens to the fluid that is filtered and not absorbed?
It goes into our lymphatic system
126
In a rested state, there will always be a net filtration of fluid into the interstitial space over time. Why is that?
In a rested state
filtration out = 11
reabsoriotn in = 9
Overall, 2 leaves into the interstitial space
127
What is edema?
excessive fluid accumulation in the ECF or interstitial space
128
What are 2 scenarios where more serious edema occurs?
1. Trauma, injury
- blood flow to the point of injury to recovery
- swelling occurs
2. Elephantiasis
- due to a mosquito bite
- A mosquito delivers a roundworm parasite, and it lives in ur lymph system and blocks the drainage
- causes major swelling
129
What are the 3 important functions of the lymphatic system?
1. Fluid balance
2. Immune surveillance
3. Movement of immune cells
130
True or False
The lymph system connects to blood capillaries in your lungs in your pulmonary circulation and to the capillaries in your systemic circulation
True
131
Does our lymph system connect to our arterial side?
No
132
True or False
Our lymph system is parallel to the venous circulation
True
133
True or False
The lymphatic system is considered an "open circulation."
True
134
What determines the lymphatic system to move in one direction?
One-way valve to prevent backflow
135
What are the lymph nodes?
area where the interstitila fluid drains and gets detected on whether or not there is an infection and if there is the lymph nodes will release immune responses
136
Is there smooth muscle in the lymph capillaries?
No
137
Is there smooth muscle in the lymph vessels?
yes
138
What can the lymph node release as immune responses?
T and B cells
139
Generally, how much movement of fluid do we have going through capillary filtration per day?
20L/day
140
Of the 20L/day of fluid that is being infiltrated how much of it is being reabsorbed generally?
17L/day
141
True or False
In lymph capillaries, the endothelial cells overlap
True
142
True or False
Smooth muscle is in the lymph vessels to contract to ensure the fluid goes one way
True
143
What are the typical pressures in the veins?
17 and lower
144
True or False
The veins have the lowest pressure
True
145
Are veins very contractile?
No, miminal smooth muscle
146
What percentage of our blood is "sitting" in our veins
60%
147
How do the one-way valves work?
When nearby muscles contract, the one-way valves will ensure that blood only goes towards the heart, meaning the valves towards the heart will open and the other will remain closed
148
What is deep vein thrombosis?
This is when there is a pooling of blood in the veins
- leads to a blood clot (thrombosis)
- can lead to embolus (a moving blood clot)
149
What are the odds of having deep vein thrombosis?
1/300
150
True or False
Veins are more compliant than arteries
True
151
Can the SNS act on both arteries and veins?
Yes
152
Why are the veins more compliant than the arteries?
- thin-walled
- large diameter
- minimal maxtro proteins (poor recoil with low elastin)
153
In the venous system, what will occur when there is an increase in SNS?
- release of NE
- leads to vasoconstriction
154
What are the 2 factors of increasing pressure that will determine venous return?
1. Peripheral vein factors (diameter)
- increased SNS activity: vasoconstriction
- increased blood volume
- increase muscle pump
*All of these will increase venous pressure
2. Right arterial factors (want to reduce pressure)
- increased inspiration: leads to decreased pressure in the thoracic cavity and increased pressure in the abdomen
- reduces pressure in the atria
155
What is denoted at P1?
Peripheral vein factors (diameter)
156
What is the central regulator of MAP?
Baroreceptors?
157
Is the baroreceptor reflex determined by high or low blood pressure?
High blood pressure
158
Can low blood pressure ever activate the baroreceptor reflex?
No
159
How does the Baroreceptor reflex work?
Activated by high blood pressure
- baroreceptors will then activate the PNS to inhibit the SNS
- lowering the MAP
160
True or False
The baroreceptor is a negative feedback response
True
161
True or False
If we have low blood pressure, it will decrease the baroreceptor reflex, which will increase the SNS activation, which will take over and then increase the MAP
True
162
What are the 2 places where the baroreceptors are located?
1. Aortic bodies
- Detecting blood pressure going to the systemic circulation
2. Carotid bodies
- Controlling blood flow to our brain and head
163
How are baroreceptors activated?
similar to mechanoreceptors
- activated by stretch
- MAP (high or low blood pressure)
- increased the firing rate of the afferent nerves
- Information goes to the Cardiovascular Control Center (medulla oblongata) to send the signal for changes to occur
164
What happens if we have to much MAP going up to our brain? High blood pressure
- cause a stroke
- long term: dementia
165
What happens if we have too little MAP going up to our brain? Low blood pressure
- faint
166
How many kidneys do we have?
2
167
The kidney is attached to what?
ureter
168
What are the 5 functions of the Kidney?
1. Fluid and ion homeostasis
- ECF volume and blood pressure
- osmolarity
- ion balance
- pH
2. Waste excretion
3. Drug removal
4. Hormone production
- Epo
- Renin : Angiotensin 2
- Vitamin D activation
5. Glucose Synthesis
- can produce glucose as well
- while fasting
169
What is the total volume of the fluid in our bodies?
40L
170
If our total body fluid volume is 40 L, how much of it is blood?
blood: 5 L
171
If your total circulating blood volume is 5 L, how much is plasma?
3 L, 60% of the blood is plasma
172
What is the main functional unit of the kidney?
The nephron
173
Where does filtration happen?
In the glomerulus of the nephron
174
Where does the glomerulus lead to?
Bowmans capsule
175
Can secretion happen after the glomerulus from the peritubular capillary back into the kidney tubule?
Yes, a very small percentage
176
What is the process of blood flow and plasma through the nephron?
1. Blood flow is in the afferent arteriole going into the glomerulus
- 80% goes to the efferent arteriole, then to your peritubular capillaries back into the veins
- 20 % gets filtered through the glomerulus into the Bowman's capsule in the nephron
2. That 20% of plasma leaves Bowman's capsule and enters the proximal tubule
3. The proximal tubule leads to the loop of Henle
- descending loop
- ascending loop
4. After the loop of Henle follows the distal tubule follows
5. The distal tubule will dump everything in the collecting duct
177
Where are your peritubular capillaries?
begins at the efferent arterioles and surrounds the nephron for reabsorption
178
Why are there multiple ducts on the collecting duct?
All the nephrons attach to it to excrete waste into the collecting duct
179
What are the 11 names of the structures within the nephron?
1. Glomerulus
2. Bowman's capsule
3. Proximal convoluted tube
4. Descending thin loop of Henle
5. Ascending thin loop of Henle
6. Ascending thick loop of Henle
7. Distal convoluted tubule
8. Cortical collecting duct
9. Medullary collecting duct
10. Renal Pelvis
180
True or False
The glomerulus is considered a capillary
True
181
What are the 7 names of the BLOOD flow from the renal artery to the renal vein?
1. Renal artery
2. Afferent arteriole
3. Glomerulus, capillary
4. Efferent arteriole
5. Peritubular capillaries/vasa recta
6. Venules
7. Renal veins
182
What are the 2 different types of nephrons?
1. Cortical
2. Juxamedullary
183
Where is the renal corpuscle of any kind of nephron located? (glomerulus)
In the cortex
184
What are the 4 unique characteristics of the juxtamedullary nephron?
1. Glomeruli are in the inner layer of the cortex
2. Makes up about 20% of all nephrons
3. Longer loop of Henle
4. Produces concentrated urine
185
What is a vasa recta?
continuation of the efferent arteriole following the loop of Henle, allowing for very concentrated urine as it allows for reabsorption
185
What are the 3 unique characteristics of the juxtamedullary nephron?
1. Glomeruli are in the outer layer of the cortex
2. Makes up 80% of all nephrons
3. A lot more of excretory and regulatory functions
- water, solute and ion absorption
186
Which kind of nephron contains a vasa recta?
Juxtamedullary nephrons
187
At glomerular filtration, what cannot pass through the pores?
large proteins
188
When plasma enters the glomerulus it is referred to as what now?
filtrate
189
True or False
Capillaries have endothelial cells, and tubules have epithelial cells
True
190
What are podocytes, and where are they found?
found - in the walls of the glomelrus
- in between podocytes lies filtration slits to allow the movement of filtrates
191
How does filtrate move from the glomerulus into the lumen of the Bowman's capsule?
- moves through the pores between endothelial cells
- through the basement membrane
- through the podocytes filtration slits
192
How do we determine glomerular filtration rate?
- hydrostatic pressures
- osmotic pressures
193
In the glomerulus, is there filtration and absorption happening? Why or why not?
No, only filtrations
- A small surface area does not allow for a section of reabsorption
194
What are the 3 pressures of the Glomerular filtration
1. Glomerular capillary blood pressure
2. Bowman's space fluid pressure
3. Plasma protein osmotic pressure
195
What is the pressure of the Glomerular capillary blood and which way does it move?
55 mmHg
- moves into the bowman's capsule
196
What is the pressure of Bowman's space fluid, and which way does it move?
15 mm Hg
- moves towards the glomerulus
197
What is the pressure of Plasma protein osmotic, and which way does it move?
30 mm Hg
- moves towards the glomerulus
198
What does the Kf refer to?
The surface area of the capillaries (glomerulus) and the permeability (number of pores)
199
Is the Kf always constant?
Typically, yes, unless there is a kidney disease present
200
How does increased arterial blood pressure affect GFR?
increases arterial bp
-
increases g bp
-
increases net filtration pressure
-
Overall increases GFR
200
What is the equation for GFR?
net filtration pressure x Kf
201
Is increasing the arterial bp a direct or indirect cause of increasing the GFR?
direct
202
What is an indirect way we can alter the GFR without manipulating the MAP?
Through the SNS of vasoconstriction and vasodilation
203
What would the vasoconstriction of the afferent arterial lead to in terms of GFR?
vasoconstriction of the afferent arteriole
-
Decrease glomerular capillary bp
-
Decrease net filtration pressure
-
Overall, decrease the GFR
204
What would the vasodilation of the afferent arterial lead to in terms of GFR?
vasodilation of the afferent arteriole
-
increases glomerular capillary bp
-
increases net filtration pressure
-
Overall, increases the GFR
205
What would the vasoconstriction of the EFFERENT arterial lead to in terms of GFR?
vasodilation of the efferent arteriole
-
increases glomerular capillary bp
-
increases net filtration pressure
-
Overall, increases the GFR
206
What would the vasodilation of the EFFERNT arterial lead to in terms of GFR?
vasoconstriction of the afferent arteriole
-
Decrease glomerular capillary bp
-
Decrease net filtration pressure
-
Overall, decrease the GFR
207
Can the efferent and afferent arterioles act independently of each other, meaning one dilates and one constricts?
Yes
208
Does GFR always vary with changes in MAP?
Yes, increasing the MAP will increase the G-capillary pressure, overall increasing the GFR
209
What are the dangers of having too high a GFR?
- Dangerous imbalance of fluids, electrolytes and wastes
210
What are 2 ways we can maintain the GFR when the MAP changes?
1. Local regulatory mechanisms
- myogenic mechanism
- flow autoregulation
2. Juxtaglomerular feedback
- based on the amounts of NaCl through the tubule
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Where does Juxtaglomerular feedback occur?
Juxtaglomerular apparatus
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Where is the Juxtaglomerular apparatus
The intersection between the afferent arteriole and the efferent arteriole meets
213
What is the macula densa?
Specialized epithelium that senses the distal tubule flow in the concentration of NaCl
- sensors for NaCl
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Where is the macula densa?
In the distal tubule
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What can the macula densa do in terms of NaCl?
It can sense changes in NaCl, and whether it is too high or too low, it can secrete paracrine factors that affect the afferent arteriole diameter
216
What are granular cells?
Specialized endothelium cells within the afferent arterioles
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What do granular cells do?
- Take feedback from other places, like SNS or the macula densa cells
- The granular cell can then signal the afferent arteriole to vasoconstrict or vasodilate
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How does Juxtaglomerular feedback work?
Scenario 1 = Too much NaCl is being excreted in the urine
Increased con of NaCl in the tubule
-
sensed by the macula densa
-
macula densa will secrete Adenosine
-
Adenosine causes vasoconstriction of the afferent arteriole
-
Decrease glomerular capillary pressure
-
Decrease GFR, which helps retain NaCl + water in the body
219
True or False
If we have a low GFR, that helps us retain NaCl and water in the body
True
220
True or False
If we have a high GFR, that helps us retain NaCl and water in the body by increasing tubular reabsorption
True
221
How does Juxtaglomerular feedback work?
Scenario 2 = Low NaCl, indicates low blood volume or low blood pressure (dehydration)
Decreased con of NaCl in the tubule
-
sensed by the macula densa
-
macula densa will secrete Prostaglandin
-
Prostaglandin causes vasodilation of the afferent arteriole
-
Increase glomerular capillary pressure
-
Increase GFR, which helps retain NaCl + water in the body by increasing tubular reabsorption
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Generally, how much filtrate do we have in our body?
125 ml/min
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Is trans-epithelial transport selective and variable?
Yes, highly selective process and variable along the length of the nephron
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What is renal plasma flow?
Volume of the plasma that passes through the kidneys per unit of time
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What is renal clearance?
volume of plasma that is completely removed of a substance per unit of time
- aka selective reabsorption
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What are examples of substances that will not undergo reabsorption?
- Inulin: soluble fibre
- Creatinine: byproduct of creatine phosphate in the muscles
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What is Inulin, and why is it important?
Clinically important
- If we have to give someone inulin, we can determine what is happening with GFR
- We can measure how much inulin is in their urine
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What are examples of a substances that will be completely reabsorbed?
Glucose
228
If we are undergoing too much muscle loss, what will we have a lot of in our urine?
creatinine
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If you have diabetes, will your Renal clearance for glucose be 0
typically not
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What are examples of substances that undergo partial reabsorption?
- Na+
- Urea: waste byproduct and contains Nitrogen
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Can the reabsorption of Urea help concentrate our urine?
Yes
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What is the range of renal clearance for partial reabsorption?
1-124 mlmin
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What are examples of substances that will not undergo reabsorption, but there will be secretion occurring?
- H+
- K+
- Penicillin (can also be secreted back into the nephron from the peritubular capillaries)
234
True or False
During exercise, we produce lots of H+ and K+ ions, and they can lead to exercise-induced fatigue, which we want to clear out
True
235
What would be the range of Renal clearance for no reabsorption + secretion?
126-625 ml/min
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Tubular reabsorption starts with which ion and how?
Na+
- via active transport
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What are the 4 main steps of the tubular reabsorption process?
1. Na+ is absorbed by active transport
2. This creates an electrochemical gradient
- that allows for anion reabsorption
3. Build-up of ions in the interstitial fluid
- This creates an osmotic gradient
4. Water moves by osmosis after solute reabsorption
- moves water into the peritubular capillary for reabsorption
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Tight junctions are found where?
In the space between the tubular epithelial cells
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The tubular epithelial cells have two sides of the membrane, which are called what?
1. Luminal cell membrane
- facing inside the lumen
2. Basolateral cell membrane
- facing the lateral space, aka the interstitial fluid between a tubule and the peritubular capillary
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How do we move the filtrate from the tubular lumen into the plasma of the Peritubular capillary?
5 Steps for the process of Transepithelial transport
1. Enters the luminal cell membrane
2. The cytosol
3. Crosses basolateral membrane
4. The interstitial fluid
5. Capillary wall
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When talking about the 5 steps of the process of Transepithelial transport, all the areas the ion has to cross are technically what?
barriers
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What is the process of Sodium reabsorption?
1. Na+ passively moves into the tubular cell
- via a sodium channel
- concentration gradient
- electrochemical gradient
2. Na+ is actively pumped to the basolateral side of the cell by the Basolateral sodium-potassium ATPase carrier
3. Na+ diffuses into the peritubular capillary
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How do we create an electrochemical gradient for Na+ in the tubular cell?
Basolateral sodium-potassium ATPase carrier
244
Where does the Basolateral sodium-potassium ATPase carrier reside?
In the basolateral cell membrane
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What is causing the concentration gradient of Na+ in the tubular cell?
Because we actively transporting sodium out of the tubular cell
246
What is the net change of ions in the tubular cell, and why?
- Net change is negaitve
- Electrochemical gradient is negaitve
It's Overall negative because ultimately we are moving 3 Na+ out and 2 K+ in!
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Normally, how much filtered Na+ is reabsorbed?
99.5%
248
What percentage of the kidneys' total energy needs is used to transport sodium?
80%
248
True or False
We want to retain our Sodium
True
249
Where along the nephron is the largest amount of Na+ being absorbed?
Proximal tubule
250
At the proximal tubule, what % of sodium is being reabsorbed?
67%
251
Why is it important for the reabsorption of Na+ at the proximal tubules? What else does it help get reabsorbed?
Plays a role in the reabsorption of:
- glucose
- urea
- amino acids
- water
- Cl-
252
At the ascending limb of the loop of Henle, what % of sodium is being reabsorbed?
25%
253
Why is it important for the reabsorption of Na+ at the ascending limb of the loop of Henle? What else does it help get reabsorbed?
Plays a role in the:
- concentrating the urine
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At the distal and collecting tubules, what % of sodium is being reabsorbed?
8%
255
Why is it important for the reabsorption of Na+ at the distal and collecting tubules? What else does it help get reabsorbed?
Plays a role in:
- Hormonal control
- Regulating ECF volume
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What is the process of water reabsorption?
1. Water moves through a selective water channel called aquaporins
- can also go through the tight junction
2. Water moves out of the tubular cell via osmosis
- due to the high concentration of Na+ in the lateral space
- follows the osmotic gradient
3. Water moves into the peritubular capillary due to hydrostatic pressure and osmosis
- The hydrostatic pressure gradient helps move water into the peritubular capillary
- Through osmosis, as there is Na+ in the peritubular capillary that can draw water into the peritubular capillary as well
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How do we create a hydropstatic pressure gradient in the interstitial space
Interstitial fluid is a tight space
- When we draw lots of water into it creates a pressure gradient
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Are any of the steps of water reabsorption active?
No, they are all passive processes
259
What is the process of Glucose Reabsorption?
1. Na+ enters the cell down an electrochemical gradient using the SGLT-2
- Glucose is moving against its concentration gradient
2. Na+ is pumped to the basolateral side of the cell via the basolateral Sodium-Potassium pump
3. Glucose passively diffuse out of the cell
- via GLUT2 down its concentration gradient
4. Glucose passively diffuses into the peritubular capillaries
- via GLUT1 down its concentration gradient
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What is the SGLT-2?
Sodium-Glucose co-transporter 2
260
Why is the SGLT-2 labeled as an active transporter?
Because glucose is being actively transported against it's concentration gradient
- NOT DUE TO THE USE OF ATP, AS IT IS NOT REQUIRED
261
What are the GLUT2 and GLUT1?
Facilitated diffusion transporters
- speeds up the movement of glucose
262
True or False
The amount of glucose entering the filtrate is proportional to plasma glucose concentration
True
263
What determines the maximum rate of reabsorption of glucose?
SGLT-2
264
Transport Maximum refers to what?
The maximum rate of reabsorption of glucose in the tubule
265
If we increase blood glucose, what will occur to our glucose filtration?
Increases
266
What is the value of our tubular maximum?
370 mg/min of glucose
267
True or False
The maximum amount of glucose that can be reabsorbed at the tubule is 370, and it is determined by the SGLT-2
True
268
True or False
The more SGLT-2 transporters we have, the more it can be reabsorbed in the tubule
True
269
How can the SNS and insulin affect the SGLT-2 transporters?
It can make them move faster!
270
What is the Renal threshold?
The plasma concentration of glucose that results in saturation of the SGLT-2 transporters is detected as a spillover of glucose into the urine
271
If our plasma concentration of glucose exceeds 300 mg/100ml what happens to our SGLT-2 function?
Will not be able to reabsorb the glucose
- Glucose will be excreted in our urine
272
If glucose shows up in our urine what does that mean?
predisposed to diabetes or has diabetes
273
What are the 2 factors that affect the tubular maximum?
1. Number of SGLT-2 transporters
2. Rate of action
273
What is the typical range of glucose concentration in the plasma for a healthy individual?
less than 100 mg for 100 ml
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What are 3 features of the proximal tubule?
1. Very permeable to water
2. Na+, Cl- and H2O reasbsorbed at similar rates
3. Reabsorption of glucose and amino acids
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What are 2 features of the descending loop of Henle?
1. Permeable to water
2. NO Na+ reabsorption
276
What are 2 features of the ascending loop of Henle?
1. Impermeable to water
2. Na+ reabsorption occurs
- via sodium-chloride-potassium co transporter
277
What is the main feature of the collecting duct?
permeable to H2O, controlled by vasopressin (a hormone in the kidneys)
278
What is the main purpose of the loop of Henle?
To reabsorb water by generating hyper-osmotic interstitial fluid within the medulla
279
What is osmolarity?
Number of solutes per Liter
(For a given volume of liquid, we are using Liters)
280
True or False
The interstitial fluid in the cortex is iso-osmotic
True
281
What does it mean to be iso-osmotic?
The number of solutes in one area compared to another area is equal
282
What is the iso-osmotic value of the solutes in the interstitial fluid in the cortex?
300 mosm/L
283
As we get deeper in the medulla what is happening to the osmolarity?
increases
284
True or False
The medulla is hyper-osmotic
True
285
What is hyper-osmolarity?
high concentration of solutes for a given volume of liquid
286
What is the hyper-osmotic value of the solutes in the interstitial fluid in the medulla?
1200 mosm/L
287
True or False
The descending loop of Henle contains aquaporins
True
288
Does the ascending loop of Henle have aquaporins?
No, water cannot get out
289
True or False
The loop of Henle is a hairpin loop, so the actions on one side of the loop will affect the other side
True
290
What is the process of the osmotic gradient?
1. In the ascending loop, Na+-CL-K+ pumps move salts into the interstitial space
2. This increases the osmolarity of the interstitial fluid and reduces the osmolality of the tubular fluid
3. In the descending loop, water diffuses out of the tubule into the interstitial space
- follows osmotic gradeint
- which will equilibrate with the osmolarity of the interstitial space
Cycle continues...
291
Where is the highest osmolarity in the loop of Henle?
At the base of the loop of Henle
292
True or False
The sodium-chloride-potassium pump can achieve approximately a 200 mosm/L difference between the interstitial space and tubular filtrate
True
293
Why is the movement of filtrate in the Loop of Henle called a countercurrent multiplication?
countercurrent: creates a high osmolality in the loop of Henle, which increases the transportation of NaCl in the ascending limb, which will then increase the water reabsorption in the descending limb
- leading to concentrated urine
Multiplication: flitrate gets more and more concentrated
294
Why would we want a long loop of Henle?
To allow for maximum reabsorption of water
295
What does the Vasa Recta do?
It's a capillary
- extension of effernt arteriole
- Reabsorbs water and NaCl
296
True or False
The Vasa recta flows in the opposite direction direction of the filtrate
True
297
The hydropstatic pressure in the Vasa Recta is very low, which favours what?
Movement of fluid into the capillary
298
Is the blood flow slow or fast in the Vasa Recta?
Slow
299
True or False
The removal of water from the interstitial space is a key function of the Vasa recta
True
300
Is the flow of Vasa Recta countercurrent with respect to tubular flow?
Yes
