Module 4: Renal Physiology Flashcards
1
Q
What is intracellular fluid?
A
The fluid within cells
2
Q
What is extracellular fluid?
A
The fluid surrounding cells
3
Q
T/F
Interstitial fluid is a kind of ICF
A
False
It’s a kind of extracellular fluid
4
Q
What barriers are between the plasma and interstitial fluid?
A
Blood vessel walls
5
Q
How do the composition of plasma and interstitial fluid differ?
A
Plasma contains plasma proteins, but interstitial fluid does not. Other than that they are pretty much identical
6
Q
What barrier(s) are between the intracellular fluid and the ECF?
A
The plasma membrane of cells
7
Q
Is K+ concentration greater in the ICF or ECF?
A
In the ICF
8
Q
Is Na+ concentration greater in the ICF or ECF?
A
In the ECF
9
Q
Describe why ECF volume is tightly regulated
A
To maintain blood pressure
10
Q
Describe why ECF osmolarity is closely regulated
A
To prevent swelling or shrinking of cells
11
Q
Describe the affect of plasma volume and blood pressure if ECF volume increases
A
Both plasma volume and blood pressure will. increase
12
Q
What are two short-term control factors of ECF volume?
A
The baroreceptor reflex
Fluid shifts
13
Q
Where are baroreceptors located? What kind of receptor are they?
A
They are mechanoreceptors located in the carotid artery and the aortic arch
14
Q
Describe how baroreceptors return blood pressure back to normal from being too low
A
If BP falls too low, cardiac output and total peripheral resistance increases to raise BP
15
Q
How do fluid shifts return blood pressure back to normal from being too high
A
If there is increased plasma volume, a shift occurs from the plasma into the interstitial compartment
16
Q
How is blood pressure regulated in the long-term?
A
Via the kidneys through control of urine output and thirst mechanism
17
Q
T/F
To maintain salt balance, salt input must be equal to salt output
A
True
18
Q
How is salt input regulated?
A
Through diet
19
Q
What are the three ways salt can be eliminated?
A
Feces, sweat, the kidneys
20
Q
What is osmolarity?
A
The concentration of a particular solute in solution
21
Q
Describe a high osmolarity solution
A
There is more solute and less water in the solution
22
Q
Describe a low osmolarity solution
A
There is less solute and more water in solution
23
Q
If there is a decrease in water in the ECF, describe the osmolarity of the ECF
A
Hypertonic
24
Q
What is hypotonicity?
A
When there is excess water in the ECF
25
What are the three major causes of hypotonicity?
Renal failure
Rapid water ingestion
Oversecretion of vasopressin
26
What is vasopressin's role in water retention
It promotes water reternion
27
Describe the 3 major causes of hypertonicity
Insufficient water intake
Diabete insipdus
Excessive water loss due to heavy sweating, vomiting, or diarrhoea
28
Describe an isotonic fluid
A fluid with equal osmolarity to that of normal body fluids
29
If there is a loss of isotonic fluid, what would happen to the ICF volume
Nothing, bc there is no imbalance still in salt vs. water
30
Describe the pathway via the hypothalamus which would occur if there was an increase in osmolarity
Hypothalamic osmotic receptors would notice the change
They would increase vasopressin secretion and the thirst response
This would increase water intake, as well as water reabsorption and decrease osmolarity
31
T/F
The kidneys are controlled by neural inputs
False
They are controlled by both neural AND endocrine inputs
32
List the 10 major functions of the kidney (or at least try to get 5)
1. Maintain water balance in the body
2. Maintain body fluid osmolarity
3. Maintain proper plasma volume
4. Help maintain acid-base balance
5. Regulate ECF solutes
6. Excrete wastes of metabolism
7. Excrete foreign compounds ingested
8. Produce erythropoietin
9. Produce renin
10. Activate vitamin D
33
In what anatomical location does the urine empty and is channeled to the ureter?
The renal pelvis
34
What is the outside layer of the kidney called
the renal cortex
35
What is the inside layer of the kidney called?
The renal medulla
36
What is the functional unit of a kidney?
The nephron
37
What is the general function of the vascular component of the nephron?
To supply blood to the nephron
38
What is the general function of the tubular component of the nephron?
To carry filtrate throughout the nephron
39
What are the structures associated with the vascular component of the nephron?
The glomerulus
The renal artery
The afferent arterioles
The efferent arterioles
The peritubular capillaries
40
What is the function of the glomerulus?
To filter water and solutes from the plasma
41
Where does blood enter the kidneys?
Through the renal artery
42
T/F
The efferent arterioles are subdivisions of the renal artery and each supply a nephron
False!
The afferent arterioles do that
43
What is the function of the efferent arterioeles?
To transport unfiltered blood from the glomerulus out of the nephron
44
What are the peritubular capillaries?
Subdivisons of the efferent arterioles that deliver oxygen to the renal tissues
45
Describe the structures contributing to the tubular component of the nephron
Bowman's capsule
Proximal tubule
Loop of Henle
Juxtaglomular apparatus
Distal tubule
Collecting duct
Renal pelvis
46
Describe the function of Bowman's capsule
Collects the fluid filtered from the glomerular capillaries
47
What are the two types of nephrons? Which is most common?
Cortical nephrons - most common
Juxtamedullary nephrons
48
Describe cortical nephrons
The glomeri lie in the outer layer of the cortex
Primarily serve secretory and regulatory functions
Loop of Henle only slightly dips into the renal medulla
The peritubular capillaries wrap around the short loops of henle
49
Describe juxtamedullary nephrons
Found in the inner layer of the cortex
Responsible for the concentration and dilution of urine
The peritubular capillares form hairpin loops of vasculatura, called the vasa recta, that are in close proximity to the long loop of henle
50
Describe in order the flow of blood through the nephron
Renal artery
Afferent arteriole
Glomerulus
Efferent arteriole
Peritubular capillaries
Renal vein
51
Describe in order the flow of solutes through the nephron
Bowman's capsule
Proximal tubule
Loop of Henle
Distal tubule
Collecting duct
Renal pelvis
52
Describe glomerular filtration
Filtration of blood through the glomerular capillaries through into Bowman's capsule
53
Describe tubular reabsorption
The process of returning substances in the filtrate to the peritubular capillaries
54
Describe tubular secretion
Allows substances to enter the tubules from the peritubular capillaries
55
T/F
Only 20% of blood that is in the glomerular capillaries is not filtered into Bowman's capsule
True!
56
What is the glomerular filtration rate?
The rate at which blood is filtered through all of the glomeruli
57
Name the three layers that make up the glomerular membrane
The glomerular capillary wall
The basement membrane
The inner layer of Bowman's capsule
58
Describe the structure of the glomerular capillary wall
Consists of a single layer of endothelial cells
Contains large pores that some proteins can pass through, ex. albumin
59
Describe the structure of the basement membrane
Composed of collagen to provide structural strength and glycoproteins to discourage the filtration of plasma proteins
60
Describe the structure of the inner layer of Bowman's capsule
Composed of podocytes, which form narrow filtration slits allowing fluid to pass into Bowman's capsule
61
What is glomerular capillary blood pressure?
The pressure exerted by the blood in the glomerular capillaries
62
What is the average glomerular capillary pressure? Why is it so high?
55mmHg
Due to the afferent arteriole diameter being larger than the efferent arterioles; also prevents glomerular capillary pressure from decreasing along its length
63
What is plasma-colloid oncotic pressure?
The presence of large proteins in the plasma that cannot be filtered, which produces an oncotic force that resists movement of water into Bowman's capsule
64
What is the mmHg of plasma-colloid oncotic pressure?
30mmHg
65
What is Bowman's capsule hydrostatic pressure?
The pressure of fluid in Bowman's capsule
It resists the movement of water out of the glomerular capillaries
66
What is the mmHg of Bowman's capsule hydrostatic pressure?
15mmHg
67
Describe the net filtration pressure equation
The glomerular capillary BP - (plasma-colloid oncotic pressure + Bowman's capsule hydrostatic pressure)
68
Describe the equation for the glomerular filtration rate
GFR = (filtration coefficient) (Filtration pressure)
69
What makes up the filtration coefficient (kf)
The glomerular surface area and membrane permeability
70
If the afferent arterioles are constricted, what would happen to glomerular capillary blood pressure?
It would decrease
71
What are the two autoregulation mechanisms to prevent swings in GFR
Myogenic activity and tubuloglomerular feedback (TFG)
72
Describe myogenic activity
When there is increased/decreased pressure that stretches afferent arteriole walls, there is automatic restriction/dilation to reduce/increase blood flow to the glomerular capillaries to prevent increases/decreases
73
What are the macula densa?
Specialized tubular cells in the juxtaglomerular apparatus that can sense changes in tubular fluid salt levels
74
Describe tubuloglomerular feedback
The macula densa releases ATP, which degrades into adenosine, which acts on the afferent arterioles to cause constriction and reduce GFR. or opposite
75
Describe how the sympathetic system would act to save GFR in case of sudden loss of blood volume and arterial pressure
The baroreceptors would sense the decrease, which would increase sympathetic activity
This would lead to restricting afferent arterioles, which would decrease GFR and urine volume
This increased conservation of fluid and salt would increase arterial blood pressure
76
T/F
The glomerular filtrate that enters the tubules is identical to plasma
False
The filtrate is absent of plasma proteins
77
T/F
There is no selectivity to glomerular filtration
True
78
Briefly describe tubular reabsorption
Processes by which water and needed solutes are returned to the plasma
79
T/F
Tubular reabsorption is highly selective
True
80
Describe the luminal membrane
The area in which epithelial cells of the tubule are in contact with the tubule lumen
81
What is the area that the epithelial cells are in contact with the interstitial fluid called?
The basolateral membrane
82
What is transepithelial transport
The movement of solutes across an epithelial cell layer
83
T/F
In the kidneys, substances can cross from epithelial cell to epithelial cell
False
They have to exit the cell, enter the interstitial space, then enter the desired cell
84
List the 5 steps of transepithelial transport
1) The substance crosses the luminal membrane
2) The substance passes through the cytosol
3) The substance crosses the basolateral membrane
4) Substance diffuses through the interstitial fluid
5) Substance crosses capillary wall to enter the plasma
85
In what locations is sodium reabsorbed?
The proximal tubule
The ascending limb of the loop of henle
The distal and collecting tubules
86
In what location does the most sodium reabsorption occur?
The proximal tubule
87
T/F
The reabsorption of sodium is both active and passive
True
88
T/F
Sodium moves across the luminal membrane passively, but moves across the basolateral membrane by active transport
True
89
How does Na+ cross in the proximal tubule?
Via a cotransport carrier that moves with organic nutrients
90
How does Na+ cross in the collecting duct?
Passively through an Na+ channel
91
How is the reabsorption of Na+ regulated in the distal tubule?
Via hormonal control
92
What is the renin-angiotensin-aldosterone system?
A hormonal system involved in the regulation of sodium
93
What are three triggers for renin secretion?
1) When the granular cells detect a drop in blood pressure
2) When sympathetic activity increases
3) When there is a decrease in luminal Na+, the macula densa cells will trigger granular cells
94
What is the function of granular cells? Where are they located?
They secrete renin and are located within the juxtaglomerular apparatus
95
Describe the secretion of aldosterone
Renin converts agiotensinogen into angiotensin I, which when passes through the lungs, is converted to angiotensin II by angiotensin-converting enzyme. Angiotensin II stimulates the adrenal cortex to release aldosterone
96
What is the function of aldosterone?
It causes an increase in sodium reabsorption in the distal and collecting tubules
97
What is atrial natriuretic peptide?
A hormone that reduces Na+ secretion and blood pressure
98
What are the three main actions of ANP?
Inhibits Na+ reabsorption in the distal tubules
Inhibits renin and aldosterone secretion
Dilates the afferent arterioles to increase GFR
99
What is the Tubular/transport maximum (Tm)
The maximum amount of a substance that can be reabsorbed
100
What is the renal threshold?
The plasma concentration at which the Tm is exceeded
101
T/F
The reabsorption of phosphate and calcium is under hormonal control
True
102
What hormone can alter the renal thresholds for phosphate and calcium for the body's needs
The parathyroid hormone
103
Describe how the body compensates for a fall in plasma phosphate concentration via the PTH path
An increase of calcium occurs, which activates the parathyroid glands to decrease PTH secretion, which increases phosphate reabsorption in the kidneys, ultimately increasing plasma phosphate concentration
104
Describe how the body compensates for a fall in plasma phosphate concentration via the Vitamin D pathway
A fall in phosphate activates the kidneys to activate vitamin D, which promotes phosphate reabsorption in the intestine, ultimately increasing plasma phosphate concentration
105
The amount of chloride reabsorbed is dependent by the amount of ____ reabsorbed?
sodium
106
T/F
All urea product is excreted in the urine
False
A large amount of urea is reabsorbed
107
What is tubular secretion?
The movement of substances from the peritubular capillaries into the tubule lumen
108
Name some of the substances that undergo tubular secretion
Hydrogen ions, potassium ions, organic anions and cations
109
In what locations is hydrogen ion secreted?
In the proximal, distal, and collecting tubules
110
T/F
Potassium is actively filtered at the glomerulus but passively reabsorbed in the proximal tubule
False
It is passively filtered at the glomerulus, but actively reabsorbed in the proximal tubule
111
What happens to sodium when there is a rise in plasma potassium?
If there is a rise in K+, aldosterone is released, which will increase Na+ reabsorption
112
What is plasma clearance?
The volume of plasma cleared of that substance by the kidneys per minute
113
T/F
Plasma clearance rate is the same for every substance
False
It is different for different substances, and depends on how the kidneys handle each substance
114
Provide an example for a substance that is filtered but not reabsorbed. What is its plasma clearance?
Inulin
Plasma clearance: 125 bc the volume cleared per minute equals the volume filtered per minute
p.s. its plasma clearance is used to estimate GFR
115
Provide an example for a substance that is filtered and reabsorbed. What is its plasma clearance?
Glucose
Urea
Plasma clearance is 0, and 62.5, respectively bc all glucose is reabsorbed, but only about half of urea is reabsorbed
116
Provide an example of a substance that is filtered and secreted, but not reabsorbed
H+
It's plasma clearance is 150, because the plasma filtration rate is greater than GFR
117
The ability to concentrate urine occurs because there is _____?
a vertical osmotic gradient in the interstitial fluid in the medulla
118
LOok into medually vertical osmotic gradient in ur notes
also, mechanism of countercurrent multiplication
119
What is the purpose of countercurrent multiplication?
To establish a vertical osmotic gradient, allowing the collecting ducts to form more concentrated/diluted urine
120
Look at vasopressin controlled water reabsorption
and countercurrent exchange
121
What is the vasa recta
The blood supply to the renal medulla
122
How does the vasa recta support the countercurrent multiplier mechanism
- Closely related to the loop of henle
- Highly permeable to NaCl and H2O
- Travels through the medulla
123
Describe osmotic diuresis
Increased excretion of water and solute
124
Describe water diuresis
The increased excretion of water when there is little or no change in the excretion of solutes
125
Describe the structure of the bladder
Composed of smooth muscle with a transitional epithelial lining, which allows it to be able to expand
126
T/F
The bladder is innervated by the parasympathetic nervous system AND its stimulation causes bladder contraction
True
127
Describe the internal urethral sphincter
Under involuntary control
Not a true sphincter
When the bladder is relaxed, the internal urethral sphincter closes the outlet to the urethra
128
Describe the external urethral sphincter
Encircles the urethra
Supported by the pelvic diaphragm
Kept close by a constant firing of motor neurons
Made of skeletal muscle
Under voluntary control
129
What is micturition?
Urinating
130
Describe the micturition reflex
The stretch on the bladder activating afferent fibres to the spinal cord, where interneurons activate the parasympathetic system to stimulate bladder contraction and relaxation of the external sphincter
