Part 3 Flashcards
1
Q
Define homeostasis.
A
maintaining a constant volume and composition of body fluids
2
Q
What is the typical daily fluid intake?
A
2300mL/day
3
Q
How do we get fluid intake?
A
ingestion of food and fluid (2100mL) carbodydrate oxidation (200mL)
4
Q
How do we lose water?
A
insensible water loss (breathing, skin) (600-800mL/day)
sweating (100mL/day)
water lost in feces (100mL/day)
water excreted via kidneys (1400mL/day)
5
Q
Why is water excreted via kidneys so variable?
A
because it depends on the amount of fluid ingested
6
Q
What are the types of extracellular fluid?
A
interstitial fluid, blood plasma, transcellular fluid
7
Q
What kind of fluid is mostly in our body?
A
intracellular fluid
8
Q
How much of our body weight is from intracellular fluid?
A
40%
9
Q
What is intracellular fluid low or high in?
A
low: sodium, calcium, chloride
high: potassium, phosphate
10
Q
What kind of cells allow free exchange of water?
A
cells between intracellular and extracellular fluid
11
Q
The cells between intracellular and extracellular fluid do NOT allow what to pass freely?
A
most electrolytes
12
Q
Where is intracellular fluid located?
A
inside the cell
13
Q
Where is extracellular fluid located?
A
outside the cells (plasma, interstitial fluid)
14
Q
How much of our body weight is extracellular fluid?
A
20%
15
Q
What is extracellular fluid low or high in?
A
low in potassium, phosphate and protein
high in sodium, chloride and bicarbonate
16
Q
What are interstitial fluid and plasma separated by?
A
highly permeable capillary membranes (except proteins)
17
Q
What is osmosis?
A
net diffusion of water across a selectively permeable membrane from a region of high water concentration to low water concentration
18
Q
What is osmotic pressure?
A
equilibrium pressure between the hydrostatic pressure and the osmotic forces generated by the addition of a solute
19
Q
Hydrostatic pressure occurs because of what?
A
increase in water in a compartment, pushing water into the solute free compartment
20
Q
What are osmoles?
A
total number of particles in a solution
21
Q
What is 1 osmole equal to?
A
1 mole of solute particle
1 mole of gluocse/liter = 1 osmole/liter
22
Q
If a molecules can dissociate into ions the osmoles equal what?
A
the number of ions
23
Q
1 mole of sodium chloride dissociates into chloride. the sodium ions equal what?
A
2osmoles/liter
24
Q
Osmolality
A
Osmoles per kilogram of water
25
Osmolarity
Psmoles perliter of water
26
When is the ONLY time osmolarity and osmolality can be used interchangably?
Dilute body fluids
27
What is an isotonic solution?
Intercellular and extracellular fluids are in psmotic equilibrium
28
What will the cell do in an isotonic solution?
Nothing, no shrinking or swelling
29
What is a hypotonic solution?
Asolution that has a lower concentration of impermeant solutes
30
What will happen to the cells if they are placed in a hypotonic solution?
Cell will swell becuase there is less than .9% NaCl and less than 5% glucose
31
What is a hypertonic solution?
Solution with a higher concentration of impermeant solutes than the cell
32
What happens to the cell in a hypertonic solution?
Cell will shrink becauze there is more than .9% NaCl or more than 5%glucose in the solution
33
When would the cells swell?
Ingestion of water or intravenous fluids
34
When would cells shrink?
Not ingesting adequate fluids, loss of fluids from gastrointestinal tract, sweating, fluid loss from kidneys
35
Water will move acrlss a selectively permeable ,e,brane from a region of ___water concentration to one that has a ____water concentration
High to low
36
The most variable spurce of water loss from the human body is water lost via...?
Urine
37
What is the first step in forming urine?
Body has to remove wasterodjcts from the blood stream
| Blood arrives in the kidney via the renal artery, interlobular arteries are thr last major bramches before filtration
38
What is step two in forming urine?
Blood is delivered to the renal corpjscle via the afferent areriole
39
What forms the renal corpuscle?
Glomerulus and bowman's capsule
40
What is step three in forming urine?
electrolytes, nutrients and waste products and water are all filtered out
red blood cells and plasma proteins should not filter out under normal conditions
41
How are renal capillary membranes different than other capillaries in the body?
they have three layers instead of two
endothelium
basement membrane
epithelial cell layer (podocytes)
42
How much more water and solutes do the glomerular capillaries filter than regular capillaries?
several hundreds of times more water
43
Why do some things filter and others don't?
because there are different pore sizes
44
What are big pores called?
fenestrae
45
What are smaller pores called?
slit pores
46
What are slit pores made of?
pedicles and podocytes
47
Describe the fenestrae in the endothelium of the glomerular capillary membrane?
thousands of relatively large fenestrae
| negatively charged to prevent passage of plasma proteins
48
Describe the basement membrane.
meshwork of proteoglycan fibrillae and collagen, which allows for the flow of a lot of water and small solutes to pass and inhibit passage of proteins
49
Describe the epiethelium of a glomerular capillary membrane.
non-continuous layer and the podocytes line the outer surface of the glomerulus
there are long foot-like projections that encircle the capillaries
50
What should never happen with the epithelium of the glomerular capillary membrane?
proteins should never leak
51
What do the long foot-like projections of the epithelium of the glomerular capillary membrane do?
allow water and solutes to be filtered through the gaps between the foot-like projections (slit pores)
52
The membranes of the glomerulus carry a negative charge to help prevent the passage of what?
proteins
53
How many layers are present at the glomerular capillary membrane?
3
54
What kinds of things are reabsorbed later in the nephron?
glucose, water, ions, amino acids, bicarbonate, phosphate
55
How does filtration work?
pressure differentials between the fluid in the glomerulus and the fluid in the bowman's capsule
56
How does the body manage pressures?
control of smooth muscle of the afferent and efferent arteriole
57
Changes in blood pressure have a significant and direct impact on what?
glomerular filtration rate
58
Colloid osmotic pressure is also called what?
oncotic pressure
59
Define renal plasma flow.
the volume of blood plasma delivered to the kidneys per unit time, usually expressed in mL/min
60
Define filtration fraction.
proportion of the fluid reaching the kidneys which passes into the renal tubules
61
How do you calculate the GFR?
GFR= RPF x FF
62
What is the typical filtration fraction?
20%
63
What is the typical renal plasma flow?
550mL/min
64
How much do you filter from plasma per day?
160 liters
65
How does the body increase glomerular filtration rate?
altering renal plasma flow or filtration fraction
66
How do you alter renal plasma flow?
increase overall cardiac output and dilate afferent arterioles in the kidneys
67
How do you alter the filtration fraction?
contract efferent arteriole, increasing glomerular pressure
68
How else can glomerular filtration rate be determined?
balance of hydrostatic and colloid osmotic forces across the capillary membrane
69
What is the capillary filtration coefficient?
permeability of the capillary and surface area of the capillary
70
In a normal adult, what is the normal function of glomerular filtration rate?
high glomerular hydrostatic pressure and large filtration coefficient
71
What does a large filtration coefficient have?
large filtering surface area, high permeability of the glomerular capillary
72
What are the things that add up the net filtration pressure?
hydrostatic pressure inside glomerular capillaries (55mmHg)
hydrostatic pressure inside bowman's capsule (15mmHg)
colloid osmotic pressure of glomerular capillary plasma proteins (30mmHg)
colloid osmotic pressure of the proteins in bowman's pressure (0 mmHg)
you subtract the first three and add the last one
73
What are the forces that favor filtration?
glomerular hydrostatic pressure (60 mmHg)
| bowman's capsule colloid osmotic pressure (0mmHg)
74
What are the forces that inhibit filtration?
bowman's capsule hydrostatic pressure (18mmHg)
| glomerular capillary colloid osmotic pressure (32mmHg)
75
How are the capillaries of nephrons different from others in the body?
they are 3 layers of material
76
Which of the following is the correct equation for calculating the filtration fraction?
FF= GFR/RBF
77
Colloid osmotic pressure in the glomerulus is proportional to the concentration of...?
proteins in the blood stream
78
What happens if we decrease the amount of functional glomerular capillaries (with age or disease)?
decreases surface area for filtration= decrease in Kf
79
What if we increase the thickness of capillary membrane (hypertension or diabetes)?
decreases the permeability of the capillary membrane= decrease in Kf
80
What about changes in bowman's capsule pressure?
bowman's capsule pressure = decreased GFR
81
What happens if we increase glomerular capillary colloid osmotic pressure?
arterial plasma colloid osmotic pressure and increase in renal blood flow (lower fraction of the plasma is initially filtered out)
increase in glomerular colloid osmotic pressure= decreased GFR
82
increase in glomerular hydrostatic pressure equals what?
increase GFR
83
decrease in glomerular hydrostatic pressure equals what?
decrease GFR
84
What is the most common physiological regulation of GFR?
glomerular hydrostatic pressure
85
What changes glomerular capillary hydrostatic pressure?
arterial pressure, afferent arteriolar resistance, efferent arteriole resistance
86
If arterial pressure increases, what happens to glomerular capillary hydrostatic pressure?
increases
87
What is the increase in glomerular capillary hydrostatic pressure buffered by?
auto regulatory processes (there is very little increase in GFR as blood pressure increases)
88
If you constrict afferent arterioles, what happens to glomerular capillary hydrostatic pressure?
decreases
89
What happens when there is an increase in glomerular capillary hydrostatic pressure?
slight increase in GFR
90
Renal blood flow is what percent of cardiac output?
22%
91
Kidneys consume how much more oxygen than the brain?
2 times
92
Why do the kidneys consume more oxygen than the brain?
due to the higher rate of active sodium reabsorption in the renal tubules
93
How much more blood flow do the kidneys have than the brain?
7 times
94
What does the blood going to the kidney do for it?
supplies it with nutrients/remove waste products
| supplies kidney with plasma for the high rate of glomerular filtration
95
What is the renal blood flow equation?
[renal artery pressure - renal vein pressure] / total vascular resistance
96
Renal arterial pressure is equal to what other pressure?
systemic arterial pressure
97
The kidneys maintain a fairly constant blood flow and GFR over what range?
80-170mmHg
98
What is renal vein pressure?
3-4mmHg
99
Where does renal vascular resistance occur?
interlobular arteries, afferent arterioles, efferent arterioles
100
What is renal vascular resistance controlled by?
SNS, hormones, internal renal control mechanisms
101
Increase in renal vascular resistance does what to blood flow?
reduces blood flow (vice versa can happen as well)
102
Renal medulla accounts for how much renal blood flow?
1-2%
103
What is the renal medulla supplied by?
vasa recta that descend into the medulla with loops of Henle of the juxtamedullary nephrons
104
What part of the kidney receives the most renal blood flow?
renal cortex
105
Does mild, moderate or strong sympathetic activation decrease GFR?
strong
106
When would one experience a strong sympathetic activation to decrease GFR?
during severe acute situations (defense reaction, brain ischemia, severe hemorrhage)
107
What does autacoid mean?
local hormone influence
108
What does epinephrine and norepinephrine do?
constrict afferent and efferent arterioles, which decrease GFR
This is parallel sympathetic activity, GFR is only decreased in extreme circumstances
109
When is endothelin released?
when there is damaged vascular endothelial cells of the kidney and other tissues
110
Endothelin causes constriction or dilation?
vasoconstriction to decrease blood loss
111
What kind of diseases have endothelin activated?
toxemia of pregnancy, acute renal failure, uremia
112
Which hormone is a powerful vasoconstrictor?
angiotensin II
113
When is angiotensin released?
due to decreased arterial pressure or volume depletion
114
Which arteriole is usually vasodilated and which can constrict?
afferent typically stays dilated, but efferents are highly sensitive and can constrict
115
What is the purpose of angiotensin II in the kidney?
to maintain GFR and decrease flow through the peritubular capillaries
116
Why would we need to decrease flow through the peritubular capillaries?
to increase reabsorption of sodium and water in the renal tubules
117
What are the types of autacoid hormones?
angiotensin II, endothelial-derived nitric oxide, prostaglandins, bradykinin
118
What does endothelial-derived nitric oxide do?
maintains vasodilation of the kidneys, allows the normal excretion of sodium and water
119
What does atherosclerosis and damage to the endothelium do to endothelial-derived nitric oxide?
decreases it, which increases renal vasoconstriction and increases blood pressure
120
What do prostaglandins and bradykinin do?
they are vasodilators, increase renal blood flow and GFR
| counteract the vasoconstrictors of afferent arterioles
121
Giving what kind of medicine after surgery can decrease GFR drastically?
nSAIDs (aspirin)
122
Overall, what does each hormone do to the GFR?
NE, epinephrine, endothelin decrease GFR
endothelial-derived nitric oxide, prostaglandins and bradykinin increase GFR
angiotensin II prevents decrease in GFR
123
What is autoregulation for the kidneys?
an intrinsic mechanism of the kidneys that keeps blood flow and GFR relatively constant
124
Arterial pressure can range from 75-160mmHg with only how much increase in GFR?
10%
125
What would happen if we didn't have autoregulation of the kidneys?
any increase in blood pressure would quickly deplete blood volume
126
What is tubuloglomerular feedback?
feedback mechanism linking sodium concentration with renal artery resistance
this ensures a constant delivery of salt to the distal tubule
127
What happens when the renal cells sense a decrease in sodium concentration?
initiates a signal that decreases resistance to blood flow in the afferent arterioles and renin is released
128
What does a decrease in resistance to blood flow in the afferent arterioles do when there is low sodium?
increases glomerular hydrostatic pressure and increases GFR
129
What does renin do when there is a decrease in sodium?
increases the formation of angiotensin II, which constricts the efferent arterioles and increases glomerular hydrostatic pressure and increases GFR
130
What is the myogenic mechanism?
the ability of the individual blood vessels in the body to resist stretching during increased arterial pressure
131
Does the myogenic mechanism have a direct effect on GFR?
likely, and renal blood flow regulation as well
132
What is the myogenic mechanism thought to do?
protect kidneys from damage during an increase in blood pressure
133
Which is higher, filtration and reabsorption or excretion?
filtration and absorption
134
What does high GFR allow us to do?
rapidly excrete waste products from the body
135
GFR allows us to filer how many liters of blood per day?
180L/day
136
The entire plasma can be filtered how many times per day?
60 times per day
137
Which solutes have an excretion rate equal to or less than the filtration rate-reabsorption?
electrolytes (sodium, bicarbonate ions, chloride ions)
138
Which solutes have an excretion rate of nearly zero?
nutritional substances in the blood (amino acids and glucose)
139
If the body is under normal conditions, how much glucose and blood should be in the urine?
none
140
Which solutes have an excretion rate that is equal to filtration rate+secretion rate?
organic acids and bases, foreign substances and drugs
141
When a solute has an excretion rate= filtration rate + secretion rate, what does this allow?
rapid clearing of substance from the system, excreted in large amounts in the urine
142
What happens when the negative charge is compromised?
basement membrane loses its electrical charge
| albumin is filtered and will appear in the urine
143
What does urine look like if there is protein?
frothy appearance
