Test 4 week 9 Flashcards
(412 cards)
1
Q
What are the functions of the kidney?
A
- Excretion of waste product and foreign chemicals
- Regulation of water and electrolyte balances
- Regulation of body fluid osmolarity and electrolyte concentration
- Regulation of BP
- Acid-base balance
- Regulation of RBC production
- Acts as an endocrine gland
- Gluconeogenesis
2
Q
What do electrolyte concentrations determine?
A
Electrolyte concentrations determines the body fluid osmolarity
3
Q
____ competes with the liver in terms of glucose production
A
Gluconeogenesis
4
Q
What is at the apex of the renal pyramid?
A
Papilla
5
Q
What are the 3 main regions of the kidney?
A
- Cortex
- Medulla
- Papilla
6
Q
What is the cortex of the kidney?
A
The outer region, just under the capsule
7
Q
What is the medulla of the kidney?
A
The central region. Divided into an outer and inner medulla
8
Q
What is the papilla of the kidney?
A
The innermost tip of the inner medulla
9
Q
____ is where you have nephrons and they would dump into the renal pelvis, therefore collecting ducts in the ureters
A
Renal pyramids
10
Q
Kidneys ____ regenerate new nephrons and after the age of 40, the number of functioning nephrons starts to decrease by 10% every 10 years
A
Kidneys cannot regenerate new nephrons and after the age of 40, the number of functioning nephrons starts to decrease by 10% every 10 years
11
Q
20-30% of nephrons have glomeruli deep in the renal cortex near the medulla and are called ____
A
20-30% of nephrons have glomeruli deep in the renal cortex near the medulla and are called juxtamedullary nephrons
12
Q
70-80% of nephrons have glomeruli located in the outer cortex and are called ___
A
70-80% of nephrons have glomeruli located in the outer cortex and are called cortical nephrons
13
Q
____ is important for the concentration of urine
A
Vasa recta
14
Q
What are the 4 processes that sum up the formation of urine?
A
- Glomerular filtration
- Reabsorption
- Secretion
- Excretion
15
Q
What happens in the glomerular filtration step of urine formation?
A
Blood that comes through the afferent arteriole is filtered and filters out of the glomerular capillaries into the Bowman’s capsule
16
Q
What happens in the reabsorption step of urine formation?
A
The substances the body wants will reabsorb back into the peritubular capillaries and then the body holds on to them
17
Q
What happens in the secretion step of urine formation?
A
Occasionally the body wants to excrete to further secrete some of the substances and then there’ll be some substances moving out from the peritubular capillaries into the collecting tubules
18
Q
How is urinary excretion rate determined?
A
Filtration - reabsorption + secretion
19
Q
How are the peritubular capillaries formed?
A
Blood comes in from the afferent arteriole which will move through the glomerulus and will come out from the efferent arteriole then it will go around the collecting tubules to form the peritubular capillaries
20
Q
How does the renal system handle creatinine?
A
It filters it only. There is no reabsorption or secretion
21
Q
How does the renal system handle Na and Cl?
A
It only filters it and partially reabsorbs. Reabsorbs some and excrete some
22
Q
How does the renal system handle AA and glucose?
A
It filters it and completely reabsorbs it
23
Q
How does the renal system handle organic acids and bases?
A
It filters it and secretes it. There is no reabsorption
24
Q
____ is the first step in urine formation
A
Glomerular filtration
25
In glomerular filtration, blood coming in from the ____ arteriole is filtered and exits via the ____ arteriole
In glomerular filtration, blood coming in from the *afferent* arteriole is filtered and exits via the *efferent* arteriole
26
Most of the filtrate that exits the glomerular filtration is _____
Reabsorbed
27
What is GFR and what does it depend on?
GFR: Glomerular Filtration Rate
Depends on the rate of blood flow
28
What is RPF?
Rate of plasma flow
29
Filtration fraction is equal to...?
GFR/RPF
30
____ are normally not filtered and if they are it indicates a sort of disease
Proteins
31
____ is filtered 60 times per day
Plasma volume
32
What is the difference between glomerular filtrate composition and plasma?
Large proteins
33
___ is an ultrafiltrate of plasma
Interstitial fluid
34
What are the 3 main layers of the glomerular capillary membrane?
- Endothelium
- Basement membrane
- Podocytes (epithelial cells)
35
Why is the process of filtration through the glomerular capillary much easier than all other capillaries?
The glomerular capillary membrane is much more permeable than other capillaries
36
What are fenestrations?
Openings which allow substances to be filtered
37
____ are unique in which they form foot process around the basement membrane and between each foot process and the next you have slit pores that allow for movement of substances through the membrane
*podocytes* are unique in which they form foot process around the basement membrane and between each foot process and the next you have slit pores that allow for movement of substances through the membrane
38
Two foot processes are held together by ____
Nephrins
39
What happens if a podocyte gets injured?
If they injured an detach and they take away part of the basement membrane proteins can start exiting the glomerular capillary resulting in protein in the urine which is a strong indicator of some type of disease
40
For any constant molecular size, negatively charged molecules are filtered ____ easily than positively charged molecules
For any constant molecular size, negatively charged molecules are filtered *less* easily than positively charged molecules
41
Why do negative charges filter less easily?
The negative charge from proteoglycans on the glycocalyx of the glomerular endothelium. (negative charges repel one another)
42
____ is a protein in the urine
Proteinuria
43
What is the clinical significance of proteinuria?
- Early detection of renal disease in at-risk patients
44
What are two main factors that determine GFR?
- Hydraulic conductance (Kf)
| - Net filtration pressure
45
Net filtration pressure is a sum of ____
Hydrostatic and colloid osmotic forces across the glomerular membrane
46
____ a measure of the product of the hydraulic conductivity and surface area of glomerular capillaries
Hydraulic conductance (Kf)
47
What is the value of the hydraulic conductance?
4.2 ml/min/100g
48
Diseases such as uncontrolled HTN and DM gradually reduce Kf by increasing the ____
Diseases such as uncontrolled HTN and DM gradually reduce Kf by increasing the *thickness of the glomerular capillary basement membrane*
49
The colloid osmotic pressure in the Bowman's capsule is generated by the presence of ____
Proteins
50
Increased bowman's capsule hydrostatic pressure ____ GFR
Increased bowman's capsule hydrostatic pressure *decreases* GFR
51
What happens if there is a further increase of Bowman's capsule hydrostatic pressure?
It will stop the filtration of the substances of our capillary to the outside
52
What is hydronephrotic kidney ureteral obstruction?
The back up of the urine that will cause a back up of pressure to the bowman's capsule.
53
The high pressure in the Bowman's capsule will prevent and significantly decrease GFR and can result in ____
The high pressure in the Bowman's capsule will prevent and significantly decrease GFR and can result in *inability to excrete metabolic waste products and swelling of the kidney that may rupture or damage it*
54
Increased glomerular capillary colloid osmotic pressure ___ GFR
Decreases
55
What are the two factors that influence glomerular capillary colloid osmotic pressure?
- Arterial plasma colloid osmotic pressure
| - Fraction of plasma filtered by the glomerular capillaries (filtration fraction)
56
Why does net filtration pressure decrease along the glomerulus?
Because the colloid pressure in the glomerulus is increasing because the concentration in the glomerular capillary is increasing
57
Increased glomerular capillary hydrostatic pressure ___ GFR
Increases
58
Changes in the ___ are the primary means for physiology regulation of GFR
Changes in the *glomerular capillary hydrostatic pressure* are the primary means for physiology regulation of GFR
59
What are the determinants of glomerular capillary hydrostatic pressure?
- Arterial pressure
- Afferent arteriolar resistance
- Efferent arteriolar resistance
60
What happens when you increase resistance in an artery in the glomerular capillary?
There will be an increase in the pressure on the end that is proximal to the area of constriction, then they'll be a decrease in pressure afterwards
61
When there is a decrease in hydrostatic pressure distal to the area of constriction, there will be a ___ in GFR
When there is a decrease in hydrostatic pressure distal to the area of constriction, there will be a *decrease* in GFR
62
What happens when you have an increases in resistance at the efferent end of the glomerular capillary?
There is going to be an increase in the pressure on the proximal end and a decrease on the distal end
63
When there is an increase in efferent arteriolar resistance, there will be a ____ in renal blood flow which will decrease GFR
When there is an increase in efferent arteriolar resistance, there will be a *decrease* in renal blood flow which will decrease GFR
64
Why is efferent constriction severe?
It reduces renal blood flow, filtration fraction and glomerular colloid osmotic pressure
65
Moderate constriction of efferent arterioles ____ GFR
Moderate constriction of efferent arterioles *increases* GFR
66
Severe constriction of efferent arterioles ____ GFR
Severe constriction of efferent arterioles *decreases* GFR
67
Constriction of afferents ___ GFR
Constriction of afferents *decreases* GFR
68
The more increase in resistance in the afferent arteriole, the ____ the decrease in GFR
The more increase in resistance in the afferent arteriole, the *greater* the decrease in GFR
69
What are the determinants of renal blood flow (RBF)?
- The difference between renal artery pressure an renal vein pressure
* Divided by*
- Total renal vascular resistance
70
How is the total renal vascular resistance calculated?
The sum of afferent arteriole, efferent arteriole, in the vein
71
As sodium reabsorption increases ____ consumption also increases due to active transport
As sodium reabsorption increases *O2* consumption also increases due to active transport
72
___ uses the most oxygen than any other organ in the body including the brain, but they receive more than they need, because they're receiving more blood
*Kidney* uses the most oxygen than any other organ in the body including the brain, but they receive more than they need, because they're receiving more blood
73
What does the kidney need to be able to reabsorb sodium efficiently?
ATP, this is why they use so much oxygen
74
How does the sympathetic nervous system/catecholamines decrease GFR and RBF?
By increasing the resistance of renal afferent and efferent arterioles
75
How does Angiotensin II maintains GFR(preventing a decrease) and decrease RBF?
By increasing the resistance of renal efferent arterioles
76
____ decreases flow through peritubular capillaries which allows more time for reabsorption thus increases sodium and water
Angiotensin II
77
____, ____ and ____ are vasoconstrictors
Angiotensin II, endothelin and sympathetic nervous system/catecholamine
78
All vasoconstrictors _____ GFR (except Angiotensin II) and RBF
All vasoconstrictors *decrease* GFR (except Angiotensin II) and RBF
79
_____ is a vasodilator which increases GFR and RBF by ____
*prostaglandins* is a vasodilator which increases GFR and RBF by *decreasing the resistance of renal efferent and afferent arterioles*
80
Blockade of prostaglandin synthesis ____ GFR. This occurs with aspirin intake or any other kind of anti-inflammatory drugs
Blockade of prostaglandin synthesis *decrease* GFR
81
When is the blockade of prostaglandin synthesis important?
When there are other disturbances that are already tending to lower GFR
82
Volume depleted patient have ___ GFR
Volume depleted patient have *decreased* GFR
83
_____ is a vasodilator which increases GFR and RBF by ____. It also protects against excessive vasoconstriction
*Endothelial-derived nitric oxide (EDRF)* is a vasodilator which increases GFR and RBF by *decreasing the resistance of renal efferent and afferent arterioles*. It also protects against excessive vasoconstriction
84
Patient with ____ may have greater risk for excessive decrease in GFR in response to stimuli such as volume depletion
Patient with *endothelial dysfunction* may have greater risk for excessive decrease in GFR in response to stimuli such as volume depletion
85
____ is the hallmark of endothelium dysfunction
*The inability to produce sufficient amounts of nitric oxide* is the hallmark of endothelium dysfunction
86
____ is a vasoconstrictor which increases the resistance of renal efferent and afferent arterioles, resulting in _____
*Endothelin* is a vasoconstrictor which increases the resistance of renal efferent and afferent arterioles, resulting in *a decrease in GFR and RBF*
87
What are examples of sympathetic nervous system/catecholamines?
Epinephrine and norepinephrine
88
What are the neurohormonal control of GFR and RBF?
- Sympathetic activity/catecholamines
- Angiotensin II
- EDRF (nitric oxide)
- Endothelin
- Prostaglandins
89
Auto-regulation of ___ is more precise than the auto-regulation of ____
Auto-regulation of *GFR* is more precise than the auto-regulation of *RBF*
90
What are the 3 autoregulators of GFR and RBF?
- Myogenic mechanism
- Macula densa (tubuloglomerular) feedback
- Angiotensin II (contributes to GFR but not RBF auto-regulation)
91
What happens if you have poor auto-regulation with no change in tubular reabsorption?
Your GFR will increase significantly, and the person will urinate all of their plasma volume
92
What are the 2 things that go hand in hand to regulate GFR?
Auto-regulation and tubular reabsorption
93
How does myogenic auto-regulation decrease blood flow and GFR?
- Increases arterial pressure
- Which leads to an increase in stretch of blood vessel
- Which leads to an increase in cell calcium entry
- Which leads to an increase in intracellular Ca levels (which contracts the vessels)
- Which leads to an increase in vascular resistance
- Which leads to a decrease in Blood flow and GFR
94
Increase in arterial pressure ___ blood flow and GFR
Increase in arterial pressure *increases* blood flow and GFR
95
____ is a specialized group of cells found in the distal tubule
*Macula densa* is a specialized group of cells found in the distal tubule
96
What role of macula densa in tubuloglomerular feedback?
- When renal artery BP increases, both RBF and GFR increase
- Increase GFR results in an increase in delivery of water and solute to the macula densa
- The macula densa is part of the juxtaglomerular apparatus, which responds to the delivery load by secreting a vasoactive substance that constricts afferent arterioles via a paracrine mechanism
- This constriction decreases RBF and GFR back to normal
97
Fever, pyrogens ___ GFR
Increases
98
Glucocorticoids ___ GFR
Increases
99
Aging ___ GFR
Decreases GFR 10% per decade after 40 years through the decrease of nephron
100
Hyperglycemia ___ GFR (diabetes mellitus)
Increased
101
High dietary protein ____ GFR, while low dietary protein ____ GFR.
High dietary protein *increases* GFR, while low dietary protein *decreases* GFR.
102
How does protein ingestion increase GFR?
- Protein ingestion increases amino acid concentrations
- Which increases proximal tubular amino acid reabsorption
- Which increases proximal tubular NaCl reabsorption
- Which decreases macula densa NaCl
- Which decreases afferent arteriolar resistance
- Which increases GFR
103
What are the things that regulate tubular reabsorption?
- Glomerulotubular balance
- Peritubular physical forces
- Hormones
- Sympathetic nervous system
- Arterial pressure (pressure natriuresis)
- Osmotic factors
104
What are the hormones that regulate tubular reabsorption?
- Aldosterone
- Angiotensin II
- Antidiuretic hormone (ADH)
- Natriuretic hormone (ANP)
- Parathyroid hormone
105
What does glomerulotubular balance refer to?
Refers to the fact that the total rate of reabsorption increases as the filtered load increases, even though the percentage of GFR reabsorbed in the proximal tubule remains relatively constant at about 65%
106
What are the segments of the GI tract?
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large intestine
- Sphincters between segments
107
What are the layer of the GI tract?
1. Serosa (outermost layer)
2. Longitudinal muscle
3. Myenteric (Auerbach's) nerve plexus
4. Circular muscle
5. Submucosa
6. Submucosal (Meissner's) nerve plexus
7. Muscularis mucosae
8. Mucosa
9. Epithelial lining
108
What are the neural control of the GI tract?
- Intrinsic control
| - Extrinsic control
109
Intrinsic control is the ____ nervous system. Including the ___ and ____ plexus
Intrinsic control is the *enteric* nervous system. Including the *myenteric (auerbach's ) and submucosal (meissner's) plexus*
110
Extrinsic control is the ____ nervous system. Including ___ and ____
Extrinsic control is the *autonomic* nervous system. Including *parasympathetic* and *sympathetic*
111
Parasympathetic extrinsic control mainly stimulates ____
Acetylcholine
112
Sympathetic extrinsic control mainly inhibits ____
Norepinephrine
113
Where is the enteric nervous system- myenteric plexus located?
- Esophagus to anus
| - Between longitudinal and circular SM layers
114
What is the function of the enteric nervous system- myenteric plexus?
Controls GI motility
115
What are the stimulatory influences of the enteric nervous system- myenteric plexus?
- Increases tonic contraction (tone)
| - Increases contraction frequency/ intensity (increased propulsion)
116
What are the inhibitory influences of the enteric nervous system- myenteric plexus?
- Decreased sphincter tone (relax)- pyloric sphincter, ileocecal sphincter, LES
117
Where is the enteric nervous system- submucosal plexus located?
Mucosal layer from the esopphagus to the anus
118
What is the function of the enteric nervous system- submucosal plexus?
- Secretion
- Absorption
- Contraction of muscularis mucosa
119
A decrease in GFR is going to cause a ____ in distal NaCl delivery to the macula densa
A decrease in GFR is going to cause a *decrease* in distal NaCl delivery to the macula densa
120
As a result of the decrease off NaCl delivery to the macula densa, there will be a ____ macula densa NaCl reabsorption, therefore the macula densa will not release the substances that causes ____ and as a result, the afferent arteriolar resistance will ___
As a result of the decrease off NaCl delivery to the macula densa, there will be a *decrease* macula densa NaCl reabsorption, therefore the macula densa will not release the substances that causes *vasoconstriction* and as a result, the afferent arteriolar resistance will *decrease*
121
The decrease in the afferent arteriolar resistance causes a ___ in blood flow, therefore ____ NaCl delivery
The decrease in the afferent arteriolar resistance causes a *increase* in blood flow, therefore *increasing* NaCl delivery
122
What happens if there is an increase in NaCl reabsorption proximally?
- Less NaCl will reach the distal tubule resulting in
- Less NaCl reaching the macula densa, which results in
- A decrease in afferent arteriolar resistance and therefore
- An increase in GFR, which will increase Na delivery to the macula densa
123
___ does its job by two arms, one that is going to affect the afferent and efferent arterioles and one that is mainly going to affect the efferent arterioles
The macula densa
124
How is GFR regulated by Ang II
- There is a decrease in GFR
- Leads to less NaCl being delivered to the macula densa
- Leading to the macula densa secreting renin
- Renin will give Ang II
- Ang II increases the resistance of efferent arterioles
- Which will ultimately increase GFR
125
How is glomerular filtration of a substance calculated?
GFR x The concentration of the substance in the plasma
126
How is excretion of a substance calculated?
Urine flow rate x the concentration of the substance in the urine
127
How is secretion of a substance calculated?
- If excretion is less than filtration, then there is no secretion
- If excretion is more than filtration then secretion = excretion - filtration
128
What are the two mechanisms that tubular reabsorption employs?
Passive and active mechanisms
129
What passive mechanisms do tubular reabsorption employ?
Simple diffusion and facilitated diffusion
130
What active mechanisms do tubular reabsorption employ?
Primary and secondary active transport
131
___ is where the urine flows until it reaches the bladder
The lumen
132
For a substance to be reabsorbed, it needs to be ____
1. Transported across the tubular epithelium into the renal interstitial fluid
2. Transported through the peritubular capillary membrane into the blood
133
What does the paracellular path mean?
It means that the substances in the lumen are not going to enter the tubular cells, rather they're going to diffuse between them. Even though they are joined by tight junctions, they are still permeable
134
What does the paracellular path mean?
Means that substances in the lumen need to enter the cell and then exit the cell
135
The primary active transport through the tubular lumen include?
- Sodium-potassium ATPase
- Hydrogen ATPase
- Hydrogen- potassium ATPase
- Calcium ATPase
136
What are the additional provisions for Na transport?
- Brush border
| - Carrier proteins on the luminal surface that provide facilitated diffusion
137
What does a brush border do?
It increases the chance of sodium reabsorption significantly
138
The _____ creates chemical and electrical gradient which facilitates the diffusion of sodium into the cell membrane
The *sodium potassium ATPase* creates chemical and electrical gradient which facilitates the diffusion of sodium into the cell membrane
139
What are the 3 steps involved in the net reabsorption of Na?
- Na is transported across the basolateral membrane against its electrochemical gradient by the NaK ATPase
- Diffusion across the luminal membrane- driven by the electrochemical gradient established by the Na-K ATPase
- Na and other solutes are reabsorbed from the interstitial fluid into the peritubular capillaries by ultrafiltration
140
What is ultrafiltration?
A passive process driven by starling forces
141
Secondary active transport is essential for the reabsorption of ___ and ____
Secondary active transport is essential for the reabsorption of *glucose and amino acids*
142
___ allows for the reabsorption of solute from the tubular lumen to move against the concentration gradient. This also allows some substances to the secreted into the tubular lumen
Secondary active transport
143
Glucose and amino acids use the ___ gradient
The sodium gradient
144
_____ is essential for the reabsorption of glucose and amino acids
Secondary active transport
145
_____ a feature of facilitated diffusion, is a movement that requires carrier proteins
Transport maximum
146
Some substances have a maximum rate of tubular transport due to _____ and ____
Some substances have a maximum rate of tubular transport due to *saturation of carrier proteins* and *limited ATP*
147
What happens once the transport maximum is reached for all nephrons?
Further increases in tubular load are not reabsorbed and are excreted
148
What is threshold?
The tubular load at which transport maximum is exceeded in some nephrons.
149
Substances that are passively transported do not exhibit a ___, rather they show characteristics of gradient-time transport (obey the laws of simple diffusion)
Substances that are passively transported do not exhibit a *Tmax*, rather they show characteristics of gradient-time transport (obey the laws of simple diffusion)
150
What is the rate of transport of substances that show the characteristics of gradient-time transport dependent upon?
- Electrochemical gradient
- Permeability of the membrane
- Time that the fluid containing the substance remains in contact with the luminal membrane. (the more time they remain in contact, the greater the possibility of transport)
151
In the proximal tubule, Na transport obeys _____ rather than ____, like it does int he distal parts of the nephron
In the proximal tubule, Na transport obeys *gradient time transport* rather than *Tmax*, like it does int he distal parts of the nephron
152
Na Tmax can be increased by ____
Aldosterone
153
What is solvent drag?
The movement of other solutes along with water
154
The reabsorption of water and other solutes is dependent on ____
The reabsorption of water and other solutes is dependent on *the body's ability to reabsorb sodium*
155
What is the mechanism of coupling water, chloride and urea reabsorption with sodium reabsorption?
- Na reabsorption will do two things
1. lead to an increase in lumen negative potential, which leads to a passive Cl reabsorption
2. Lead to H20 reabsorption by osmosis, which will lead to an increase in luminal Cl concentration and Luminal urea concentration which will then lead to a passive Cl reabsorption and a passive urea reabsorption respectively
156
65% of filtered load of Na and water are reabsorbed by the ___
Proximal tubule
157
Since the proximal tubule epithelial cells have a high capacity for active and passive transport, they are ___
- Highly metabolic with large number of mitochondria, meaning that they can produce tons of ATP and use then for active and secondary transport mechanisms
- Have extensive brush border on the luminal side of the membrane which increases the surface are and carrier molecules
- Have extensive intracellular and basal channels for the movement of the solutes
158
___ is reabsorbed by co-transport with glucose, AA and other solutes in the first half of the proximal tubule
*Na* is reabsorbed by co-transport with glucose, AA and other solutes in the first half of the proximal tubule
159
What happens in the 2nd half of the proximal tubule?
Little glucose and amino acids remain. Na is now reabsorbed with Cl
160
The ___ of Na decreases along the proximal tubule, but the ___ remains constant
The *amount* of Na decreases along the proximal tubule, but the *concentration* remains constant
161
What are the characteristics of the thin descending and ascending segment in the loop of henle?
- Thin epithelial membranes
- No brush borders
- Few mitochondria
- Minimal levels of metabolic activity
162
What are the characteristics of the thick segment in the loop of henle?
o Thick epithelial membrane
o High metabolic activity
o Capable of active reabsorption of Na+, Cl-, and K+
o About 25% of the filtered load of Na+, Cl-, and K+ is reabsorbed here
163
What part of the loop of henle is very permeable to water?
thin descending loop
164
What part of the loop of henle is not permeable to water?
The thin ascending loop and the thick loop
165
Movement of Na across the luminal membrane in the thick ascending loop of henle is mediated primarily by ____, which all move together
Movement of Na across the luminal membrane in the thick ascending loop of henle is mediated primarily by *1-sodium, 2-chloride, 1-potassium co-transporter* which all move together
166
The 1-sodium, 2-chloride, 1-potassium co-transporter is the site of action of the _____
The 1-sodium, 2-chloride, 1-potassium co-transporter is the site of action of the *powerful "loop" diuretics*
167
By inhibiting the 1-sodium, 2-chloride, 1-potassium co-transporter which is the site of action of the loop diuretics, you are also inhibiting ____
By inhibiting the 1-sodium, 2-chloride, 1-potassium co-transporter which is the site of action of the loop diuretics, you are also inhibiting *the reabsorption of H2O, therefore excreting more H2O*
168
Why are cations forced to diffuse through the paracellular spaces in the thick ascending loop of henle?
Because there is a back leak of K+ into the lumen which
| creates a slight positive charge of +8mV in the tubular lumen
169
____ is functionally similar to the thick ascending loop, contains macula densa, is not permeable to water, is called the diluting segment meaning that it dilutes urine by reabsorbing solutes and not reabsorbing any water
*Early distal tubule* is functionally similar to the thick ascending loop, contains macula densa, is not permeable to water, is called the diluting segment meaning that it dilutes urine by reabsorbing solutes and not reabsorbing any water
170
Where does the active reabsorption of Na, Cl, K and Mg occur? This is also where 5% of the filtered load of NaCl is reasbsorbed?
In the early distal tubule
171
____ is where the thiazide diuretics work by inhibiting the sodium-chloride cotransporter
*Early distal tubule* is where the thiazide diuretics work by inhibiting the sodium-chloride cotransporter
172
____ is not permeable to water and is not very permeable to urea
*the early distal tubule* is not permeable to water and is not very permeable to urea
173
_____ has a permeability to water that depends on ADH and is not very permeable to urea
*The late distal tubule and collecting tubule* has a permeability to water that depends on ADH and is not very permeable to urea
174
What are the two different cell types in the late distal tubule and collecting tubule?
Principle cells and intercalated cells (type A or B)
175
____ cells reabsorb Na and secrete K
Principle cells
176
What are the two steps involved in the secretion of K?
1. K enters the cells because of the NaK ATPase
| 2. K then diffuses down its concentration gradient across the luminal membrane
177
_____ are the primary site of action of the potassium-sparing diuretics
*Principle cells* are the primary site of action of the potassium-sparing diuretics
178
What are the two main types of potassium sparing diuretics?
- Aldosterone antagonists: spironolactone and eplerenone
| - Na channel blockers: amiloride, and triamterene
179
How do the potassium sparing diuretics work?
They work by stopping Na reabsorption also stopping water reabsorption therefore enhancing water excretion but also sparing your K and not excreting it.
180
____ cells secrete or reabsorb H, HCO3 and K. They also play a major role in acid-base regulation. They make 30-40% cells in the collecting tubules and ducts.
*Intercalated cells* secrete or reabsorb H, HCO3 and K. They also play a major role in acid-base regulation. They make 30-40% cells in the collecting tubules and ducts.
181
____ intercalated cells secrete H by a H-K ATPase and are thus important in acidosis to secrete H and reabsorb HCO3, because you want to get rid of extra H ions so you do so by dumping them in the urine
*Type A* intercalated cells secrete H by a H-K ATPase and are thus important in acidosis to secrete H and reabsorb HCO3, because you want to get rid of extra H ions so you do so by dumping them in the urine
182
____ intercalated cells secrete HCO3 and reabsorb H and are important in alkalosis
*Type B* intercalated cells secrete HCO3 and reabsorb H and are important in alkalosis
183
What are the functional characteristics of the late distal tubule and cortical collecting tubule?
• Both segments are impermeable to urea
• Both segments reabsorb Na+ and the rate of reabsorption is
controlled by hormones – especially aldosterone and Ang II
• Type A intercalated cells secrete H+ and reabsorb HCO3 – important in
acidosis
• Type B intercalated cells secrete HCO3 and reabsorb H+ - important in alkalosis
• Permeability of these segments to water is controlled by ADH
184
What are the transport characteristic of the medullary collecting duct?
• Permeability to water is
controlled by ADH
• Is permeable to urea (unlike the cortical collecting tubule)
• Capable of secreting H+ against a large concentration gradient by active transports mechanism
185
What happens to tubular reabsorption as tubular load increases?
It increases as well
186
The higher the GFR is, the ___ the tubular load
The higher the GFR is, the *higher* the tubular load
187
What is the determinant of capillary hydrostatic pressure?
Changes in arterial pressure
188
What happens when arterial pressure is increased as it relates to capillary hydrostatic pressure and net reabsorption?
There will be an increase in capillary hydrostatic pressure, which will cause a decrease in net reabsoprtion
189
What does an increase in the afferent and efferent resistance going to cause in terms of capillary hydrostatic pressure and net reabsorption?
There will be a decrease in capillary hydrostatic pressure, which will cause an increase in net reabsoprtion
190
What are the factors that can influence capillary reabsorption and what do they do?
- Increase in hydrostatic pressure will decrease reabsorption
- Increase in colloid osmotic pressure, will increase reabsoprtion
- Increase in the filtration coefficient increases reabsoprtion
191
What are the factors that can increase colloid pressure?
- increase in filtration fraction increases colloid pressure
| - Increasein arterial plasma colloid osmotic pressure increases colloid pressure
192
____ increases Na reabsorption and K secretion
Aldosterone
193
What are the factors that increase aldosterone secretion?
- Angiotensin II
- Increased K
- ACTH
194
What are the factors that decrease aldosterone secretion?
- Atrial natriuretic peptide (ANP)
| - Increased Na concentration (osmolality)
195
How does aldosterone increase Na reabsorption?
It creates Na channels and insert them at the luminal membrane and they absorb Na
196
___ increases Na and water reabsorption?
Ang II
197
How does Ang II increase Na reabsorption?
It binds to specific receptors in the tubular cells and they increase the activity of the NaH exchanger at the luminal membrane, thereby increasing Na reabsorption
198
In what parts of the nephron does Ang II directly increase Na reabsorption?
In all parts of the nephron
199
____ constricts efferent arterioles?
Ang II
200
By constricting efferent arterioles, what does Ang II do?
- Decreases peritubular capillary hydrostatic pressure
| - Increases filtration fraction, which increases peritubular colloid osmotic pressure
201
How does Ang II increases filtration fraction?
By decreasing renal blood flow
202
What does Ang II do to GFR?
Either increases it or maintains it
203
ADH is secreted by ____
Posterior pituitary
204
What is the function of ADH?
To increase water permeability and reabsorption in distal and collecting tubes. It also allows differential control of water and solute excretion
205
____ is an important controller of extracellular fluid osmolarity
ADH
206
____ wants to get rid of Na and water, because it wants to reduce blood volume
ANP
207
How does ADH work?
- ADH binds to it receptors through a Gs pathway
- Get cAMP, which leads to protein kinase A
- Then protein phosphorylation of the vesicles, which then express aquaporins on the tubular lumen
- Aquaporins then increase water permeability
- Increase permeability of water, increases reabsorption
208
What causes the secretion of ANP?
- An increase in blood volume causes a stretch on the atria which as a result releases ANP
209
What are the things that ANP does?
1. Decreases aldosterone secretion, which will decrease Na and water retention.
2. Decreases renin release, which decreases Ang II, which will decrease Na and water retention
3. Increases GFR, which will increase Na and water retention
210
____ creates a negative feedback when blood volume starts to drop as a result of ANP, to inhibit further release of ANP
Increased GFR, which results in increased Na and water retention
211
What is the combined effect of a decrease in Na intake, decrease in ECF volume and decrease in blood volume on sympathetic activity and what does it do in s long run?
- increase of sympathetic activity
- Constriction of afferent arterioles (decrease GFR)
- Increase of Na reabsorption in the proximal tubule
- Decreased Na excretion and increased Na retention
212
What is the combined effect of a decrease in Na intake, decrease in ECF volume and decrease in blood volume on ANP and what does it do in s long run?
- Decrease ANP
- Dilation of efferent arterioles (decrease GFR)
- Increase of Na reabsorption in the collecting ducts
- Decreased Na excretion and increased Na retention
213
What is the combined effect of a decrease in Na intake, decrease in ECF volume and decrease in blood volume on tubular colloid pressure and what does it do in s long run?
- Increase of tubular colloid pressure
- Increase of Na reabsorption in the proximal tubule
- Decreased Na excretion and increased Na retention
214
What is the combined effect of a decrease in Na intake, decrease in ECF volume and decrease in blood volume on renin-Ang II-aldosterone(RAAS system) and what does it do in s long run?
- Increase renin-Ang II-aldosterone (RAAS system)
- Increase of Na reabsorption in the collecting ducts and proximal tubule
- Decreased Na excretion and increased Na retention
215
What is the body fluid osmolarity?
290/300 mOsm/L
216
What is osmoregulation?
The control of body fluid osmolarity
217
Control of water balance is exerted at the level of the ____, by function of hormone ____
Late distal tubule and collecting duct by function of hormone *ADH*
218
What is the body's response to water deprivation?
1. increase in plasma osmolarity
2. Stimulation of osmoreceptors in anterior hypothalamus
3. Increased thirst, leading to increased water drinking, which will then decrease plasma osmolarity towards normal OR there will be an increase in ADH secretion from the posterior pituitary
4. increased water permeability of principal cells (late distal tubule and collecting duct)
5a. increased water reabsorption
5b. Increased urine osmolarity and decreased urine volume
6. Decreased plasma osmolarity towards normal
219
What is the corticopapillary osmotic gradient?
It is the gradient of osmolarity in the interstitial fluid of the kidney from the cortex to the papilla, through the medulla
220
What is the osmolarity of the interstitial fluid of the kidney at the cortex?
300 mOsmlL
221
What is the osmolarity of the interstitial fluid of the kidney at the papilla?
1200 mOsm/l
222
What solutes and mechanisms contribute to the corticopapillary osmotic gradient?
1. The countercurrent multiplier
| 2. Urea recycling
223
What are the physiological effects of countercurrent multiplication?
- SIngle effect
| - Flow of tubular fluid
224
What is a single effect?
Decrease osmolarity in ascending limb of the loop of henle and increase osmolarity in the interstitial space
225
What is the flow of tubular fluid?
New fluid will come in with its new osmolarity and it will start pushing the rest of the fluid down
226
Why is urea recycling important?
Because it contributes to the countercurrent multiplier system, so that it can maintain a good osmotic gradient in the interstitial space.
227
What does ADH do in the cortico-collecting tubule?
It increases water permeability, but not urea permeability. So water will move out and urea will stay in
228
What happens as a result of the effect of ADH on urea and water permeability in the cortico-collecting tubule?
The concentration of urea in the tubular fluid increases.
229
What does ADH do in the inner-medullary collecting tubules?
It increases water permeability and urea transport (UT1).
230
What does the increase of the concentration of urea the tubular fluid cause in the inner medulla?
It causes urea to diffuse from the tubular fluid into the interstitial fluid of the inner medulla, where the osmolarity is already a little higher, allowing more water to be reabsorbed from the descending limb of the loop of henle
231
How does countercurrent exchange in the vasa recta preserve the corticopapillary osmotic gradient?
As blood flows down to the interstitial spaces, it equilibrates with the osmolarity in them. The further down it goes, the higher it gets. Solutes diffuses into the capillaries and water diffuses out, until an osmolarity of 1200 has been reached. The opposite occurs as blood moves up and out, but the osmolarity will be a bit higher than what was started with
232
What is the job of the countercurrent exchange int he vasa recta?
To maintain the osmotic gradient in the interstitial spaces of the kidney. This is a passive process.
233
What is the rate of blood flow in the vasa recta?
Slow
234
What does the contraction of the muscularis mucosa layer of the GI tract help control?
Helps control surface area of the epithelium which is important for absorption.
235
What segment does the parasympathetic extrinsic nervous system mainly work through?
The cranial and sacral segments
236
In the parasympathetic extrinsic nervous system, ___ nerves do most of the work, except in the lower parts of the large intestine where the pelvic nerves assume the role of the parasympathetic nervous system
In the parasympathetic extrinsic nervous system, *vagal* nerves do most of the work, except in the lower parts of the large intestine where the pelvic nerves assume the role of the parasympathetic nervous system
237
What are the 4 major ganglia that controls function in the sympathetic extrinsic nervous system?
- Superior cervical ganglion
- Celiac ganglion
- Superior mesenteric ganglion
- Inferior mesenteric ganglion
238
What does the splanchnic circulation do?
It dumps blood through the liver before taking it back into the systemic circulation
239
Blood that courses through the gut, spleen and pancreas flows to the liver via the ____
Blood that courses through the gut, spleen and pancreas flows to the liver via the *portal vein*
240
In the liver, blood passes through millions of minute liver sinusoids and finally leave the liver via the _____
In the liver, blood passes through millions of minute liver sinusoids and finally leave the liver via the *hepatic veins*
241
Blood flow through the liver allows the ______ to remove bacteria and other particulate matter
Blood flow through the liver allows the *reticuloendothelial cells* to remove bacteria and other particulate matter
242
Blood flow in the GI is proportional to...?
Proportional to local activity
243
What does eating to do blood flow?
It increases blood flow to the GI tract, which is why a person feel cold after eating, because blood is shunting towards the gut, therefore away from the skin
244
What are the causes of activity induced blood flow?
- The secretion of vasodilator hormones: gastrin, secretin and CCK
- Vasodilator kinins
- Low oxygen(high adenosine)
245
How does the parasympathetic nervous system control blood flow?
- By increasing gut activity, which increases blood flow
246
How does the sympathetic nervous system control blood flow?
Causes vasoconstriction which directly decreases blood flow to the intestines.
247
In what direction is the arterial and venous flow in the villi?
In opposite direction
248
What does the direction of the arterial and venous flow in the villi cause?
It causes much of the blood's oxygen to diffuse out of the arterioles directly into adjacent venules without oxygen being carried to the tips of the villi
249
What percent of oxygen in the villi is diffused in its normal manner under normal conditions?
80%
250
What happens to blood in the villi in diseased conditions?
Blood flow to the gut becomes curtailed and oxygen deficiency in the tips of the villi develops leading to ischemic death and disintegration, which will eventually lead to greatly diminished absorptive capacity
251
What are the 3 main types of GI regulatory substances?
- Endocrines (hormones)
- Neurocrines (neurotransmitters)
- Paracrines
252
What is an endocrine and how is it released?
A peptide hormone that is released into the blood through systemic circulation and acts on a distant target cell
253
What is an important feature for any peptide to be called an endocrine hormone?
Being released through systemic circulation
254
____ are released through terminal nerve endings and are released to their target cells
Neurocrines
255
____ are sometimes peptides and sometimes not, that are released through endocrine cells and diffuse to local target cells, but not to the systemic circulation
*paracrine* are sometimes peptides and sometimes not, that are released through endocrine cells and diffuse to local target cells, but not to the systemic circulation
256
What features does a molecule need to have to be classified as a GI hormone?
- To be released into the blood stream
- Act on a distant cell
- Be isolated and what they are and what they do needs to be known
257
What are the 4 molecules that are classified as hormones in the GI tract?
- CCK
- Gastrin
- Secretin
- GIP
258
What are the hormones that form the 2 families in the GI tract?
- Gastrin and CCK form a family
| - Secretin, GIP, VIP and glucagon form another family
259
What is gastrin responsible for?
Gastric acid secretion from the g cells in the stomach
| - Promotes H secretion by gastric parietal cells
260
What is the trophic activity of gastrin?
- Stimulates growth of oxyntic mucosa of stomach, duodenal mucosa, and colon mucosa
- Surgical removal of antrum causes atrophy of the stomach and other parts of the GI tract
- Patients with gastrin secreting tumors have mucosal hyperplasia and hypertrophy
261
What is antrum?
The location of G cells
262
Where is gastrin released from?
Released from G cells in the antrum and duodenum
263
What are the main stimulis of gastrin?
- protein digestion products (small peptides and AA)
- nervous, local physical distention
- calcium, decaf coffee, and wine
264
What inhibits gastrin?
- Acidification of antrum
265
How is the inhibition of gastrin a form of negative feedback?
G-cells are stimulated by high pH to release gastrin, which in turn is going to release H in order to lower the pH, which will then provide negative feedback to g cells to stop releasing gastrin
266
What are the 2 types of gastrin
- G-17
| - G-34
267
What is gastrin's response to a meal?
- Large amounts of G-17 released from antrum (“small” gastrin)
- Small amounts of G-34 released from duodenum (“big” gastrin –secreted between meals)
268
Which gastrin is released within a meal and which is released between a meal?
- G-17 is released within a meal
| - G-34 is released between a meal
269
What is gastrinoma(Zollinger-Ellison syndrome) and where does it occur?
A gastrin secreting tumor that can occur in Non-β-cell tumor of pancreas (80%) or G-cell tumors in duodenum (10-15%)
270
What does gastrinoma do?
Continually secretes gastrin into blood which will lead to hypergastrinemia
271
What does hypergastrinemia do?
Caused hypersecretion of acid
272
What does hypersecretion of acid lead to?
- Increased parietal cell mass
- Constant stimulation of hyperplastic mucosa
- Increased H+secretion by parietal cells and hypertrophy of the gastric mucosa
273
What are the symptoms of gastrinoma due to high amount of acid?
-Duodenal ulcers, diarrhea, steatorrhea, hypokalemia
274
____ is a result of loss of GI secretions in stool
Hypokalemia
275
What causes steatorrhea?
The low pH that inactivates pancreatic lipase and causes bile salts to precipitate
276
____ promotes fat digestion and absorption
CCK
277
Where is CCK released from and in response to what?
Released from I-cells in duodenum and jejunum in response to:
- Fatty acids or monoglycerides (not triglycerides)
- peptides and single AA
- Acid (weak)
278
What are the main actions of CCK?
- Emptying the gallbladder
- Secretion of pancreatic enzymes and HCO3
- Inhibits gastric emptying
279
How does CCK empty the gallbladder?
By contracting the gallbladder and relaxing the sphincter of Oddi which is at the common bile duct
280
Where are the trophic effects of CCK?
Exocrine pancreas and gallbladder mucosa
281
_____ is the principle stimulus for delivery of pancreatic
enzymes and bile into small
intestine.
*CCK* is the principle stimulus for delivery of pancreatic
enzymes and bile into small
intestine.
282
What are the physiological effects of CCK?
- Fats, peptides, and amino acids stimulate CCK secretion, which works on the pancreas to release the secretions and the gallbladder
283
____ is released from S-cells of the duodenal mucosa
*secretin* is released from S-cells of the duodenal mucosa
284
What is the stimuli for release of secretin?
- Acid in duodenum (pH < 4.5)
| - Fatty acids in duodenum
285
What are the physiological effects of secretin?
- Nature's antacid (counteracts the acidity)
- Inhibits gastric acid secretion (enterogastrone)
- Stimulates pancreatic and bile bicarbonate secretion – essential for fat digestion
- Trophic effect on exocrine pancreas
286
What is the stimuli for release of GIP?
- Released from K-cells of duodenum and proximal jejunum
- Only GI hormone that is released in response to all major nutrients(CHO, proteins, AA, and fats)
- Oral glucose but not I.V. glucose (incretin)
287
What is the physiological effects of GIP?
- Stimulates insulin release (also called gastric inhibitory peptide)
- Inhibits gastric acid secretion
288
What are the 4 molecules that are considered candidate hormones, because they don't meet all the requirements to be GI hormones?
- Motilin
- Pancreatic polypeptide
- Enteroglucagon
- Glucagon-like peptide 1 (GLP-1)
289
Where is motilin secreted from and what is its function?
* Secreted from the upper duodenum during fasting states
| * Increases GI motility – initiates the interdigestive myoelectric complexes that occur at 90-minute intervals
290
Where is pancreatic polypeptide secreted from and what is its function?
* Secreted by the pancreas in response to ingestion of CHO, proteins, or lipids
* Inhibits pancreatic secretion of HCO3 and enzymes
291
Where is enteroglucagon secreted from and what is its function?
* Released from intestinal cells in response to a decrease in blood glucose concentration
* Stimulates the liver to increase glycogenolysis and gluconeogenesis
292
Where is GLP-1 secreted produced from?
* Produced from proglucagon
* Secreted by the L-cells of the small intestine
* Incretin
293
____ are synthesized in endocrine cells of the GI tract, but do not enter the systemic circulation but act locally, which is why they are not hormones
*Paracrine* are synthesized in endocrine cells of the GI tract, but do not enter the systemic circulation but act locally, which is why they are not hormones
294
What are the 2 main paracrines?
- Somatostatin
| - Histamine
295
Where is somatostatin secreted from and what is its function?
* Secreted by D cells of the GI mucosa in response to ↓pH
* Inhibits secretion of other GI hormones
* Inhibits gastric H+ secretion
* Also secreted by the hypothalamus and the delta cells of the endocrine pancreas
296
Where is histamine secreted from and what is its function?
* Secreted by endocrine cells of the GI mucosa
| * Histamine, along with gastrin and ACh, stimulate H+ secretion by gastric parietal cells
297
Neurocrine: Ach is stimulated by ___ and it ___ GI tract
Neurocrine: Ach is stimulated by *parasympathetic nervous system* and it *activates* GI tract
298
Neurocrine: norepinephrine is stimulated by ___ and it ___ GI tract
Neurocrine: norepinephrine is stimulated by *sympathetic nervous system* and it *inhibits* GI tract
299
What are the actions of neurocrine: Ach
- Contraction of smooth muscle in wall
- Relaxation of sphincters
- Inc salivary secretion
- Inc gastric secretion
- Inc pancreatic secretion
300
What are the actions of neurocrine: norepinephrine
- Relaxation of smooth muscles in wall
- Contraction of sphincters
- Inc salivary secretion
301
_____ functions as a syncytium which is a unitary muscle
GI smooth musle
302
____ connects the cytoplasm of the GI smooth muscle
Gap junctions
303
What is the effect of gap junctions being an electrical synapse?
If one cell becomes depolarized/active, then all the other cells will too
304
What does the contraction of circular muscle do in the GI?
It shortens the ring(diameter) of the smooth muscle
305
What does the contraction of longitudinal muscle do in the GI?
It shortens the smooth muscle in the longitudinal direction, decreasing the length of that segment
306
Smooth muscle contractions are either ____ or ____
Smooth muscle contractions are either *phasic* or *tonic*
307
What are phasic contractions?
Periodic contractions that are followed by relaxations
308
What are tonic contractions?
Contractions that maintain a constant tone without regular periods of relaxations. Strength depends on stimulatory factors
309
The contraction of the circular and longitudinal muscles is essential for ____
The contraction of the circular and longitudinal muscles is essential for *peristalsis*
310
What happens when there is a bolus of food stretching the smooth GI muscle?
1. There will be a contraction of the circular smooth muscle that is behind the bolus of food. The contraction will cause a reciprocal inhibition of the area that is distal/after the bolus of food, causing it to relax
2. The longitudinal muscle after the bolus of food is going to contract followed by the inhibition of the circular muscle behind the bolus
311
What is food called in different parts of the GIT?
- Mouth: Bolus
- Small intestine: Chyme
- Large intestine: Feces
312
What are the two main types of membrane potentials in the GI smooth muscle?
- Slow waves
| - Spike potential
313
What are slow wave membrane potentials?
Rhythmical changes in membrane potential caused by variations in sodium conductance- oscillating depolarization
314
Slow waves occur at a ____ frequency and a _____ amplitude
Slow waves occur at a *fixed* frequency and a *variable* amplitude
315
____ play the role of pacemaker cells of the GIT. They are abundant in the myenteric plexus and they play the role of producing the slow waves membrane potential
*Interstitial cells of cajal* play the role of pacemaker cells of the GIT. They are abundant in the myenteric plexus and they play the role of producing the slow waves membrane potential
316
_____ dictates the max frequency of smooth muscle contraction and are independent of nervous/hormonal stimuli
*Slow waves* dictates the max frequency of smooth muscle contraction and are independent of nervous/hormonal stimuli
317
The variation of amplitude is affected by ____
The variation of amplitude is affected by *nervous/hormonal stimuli*
318
What happens as the amplitude of slow waves increase?
- Spike potential frequency increases which leads to the increase of the strength of contraction
319
Slow waves _____ action potentials
Slow waves *are not* action potentials
320
____ are changes in membrane potential either close to 0 (depolarization) or more negative (hyperpolarization)
*Slow waves* are changes in membrane potential either close to 0 (depolarization) or more negative (hyperpolarization)
321
___ is a true action potential in the GIT, that occurs when you reach the threshold of -40 and cause smooth muscle contraction
*A spike wave* is a true action potential in the GIT, that occurs when you reach the threshold of -40 and cause smooth muscle contraction
322
Spike waves are dependent on ____ channels
Spike waves are dependent on *calcium* channels
323
The frequency of spike waves are affected by ____
The frequency of spike waves are affected by *nervous/hormonal stimuli*
324
Increased frequency does not ___ max. frequency of contraction
Increased frequency does not *increase* max. frequency of contraction
325
What stimulates an increase in the resting membrane potential?
- Stretch in the muscles
- Acethylcholine
- Parasympathetics
326
What stimulates a decrease in resting membrane potential to hyperpolarization?
- Norepinephrine
| - Sympathetics
327
What is the relationship between the electrical and mechanical activity of the GIT membrane potential?
Mechanical activity slowly follows behind the electrical activity
328
____ represents the 1st step in the process of ingesting food
Chewing and swallowing
329
What is the purpose of chewing?
- Break cells: breaks apart indigestible cellulose
- Increases surface area: decreases particle size
- Mixes food with saliva: begins digestion of starches and lubricates food for swallowing
330
____ is initiated voluntarily in the mouth, but then it is under involuntary reflex control
Swallowing
331
Where is the swallowing center located?
The medulla
332
What are the 3 stages of swallowing?
- Oral phase (voluntary)
- Pharyngeal phase (involuntary)
- Esophageal phase (involuntary)
333
What happens in the oral phase of swallowing?
It initiates the swallowing process
334
What happens in the pharyngeal phase of swallowing?
Passage of food through the pharynx into the esophagus
335
What happens in the esophageal phase of swallowing?
Passage of food from pharynx to stomach
336
What are the different phases composed in the esophageal phase?
- Upper esophageal sphincter opens
- Primary peristaltic contraction
- Lower esophageal sphincter opens
- Secondary peristaltic wave
337
What happens when the upper esophageal sphincter(UES) opens?
Opened by the swallowing reflex, allowing the bolus of food to travel from the pharynx to the esophagus.
The UES then closes to prevent reflux
338
What is the primary peristaltic contraction?
Swallowing reflex, that allows food to travel down the esophagus
339
What happens when the lower esophageal sphincter(LES) opens?
The orad region of the stomach relaxes(receptive relaxation) to facilitate movement of the bolus into the stomach
340
What happens in the secondary peristaltic contraction?
If the primary peristaltic contraction does not clear the bolus a secondary peristaltic wave is initiated
341
____ is the continuation of pharyngeal peristalsis, is coordinated by the swallowing center and cannot occur after vagotomy (striated muscle)
*Primary peristalsis* is the continuation of pharyngeal peristalsis, is coordinated by the swallowing center and cannot occur after vagotomy (striated muscle)
342
____ initiates by stretch related afferent sensory input to ENS and swallowing center are both involved. This can and does occur after vagotomy
*secondary peristalsis* initiates by stretch related afferent sensory input to ENS and swallowing center are both involved. This can and does occur after vagotomy
343
What are the things that can cause a disorder of swallowing (dysphagia)?
- CVA(stroke)/cranial nerves damage
- Muscular diseases like myasthenia gravis, polio, and botulism
- Anesthesia
344
What happens in the case of CVA(stroke)/cranial nerves damage caused dysphagia?
- Aspiration - UES and pharyngeal contractions are not coordinated (getting the person to initiate swallowing is problematic)
- Secondary peristalsis is still functional
345
What happens in the case of Anesthesia caused dysphagia?
Aspiration of stomach contents, because of the relaxation of the sphincters
346
What are the 2 regions of the stomach?
- Orad region (towards the mouth)
| - Caudad region (more distal)
347
The contraction of ___ prevents the emptying of the gastric juices into the duodenum. This relaxes when we want
The contraction of *pylorus* prevents the emptying of the gastric juices into the duodenum. This relaxes when we want
348
What are the functions of the gastric smooth muscle?
- Relaxes to accommodate food- orad area (receptive relaxation)
- Mixes food with gastric juice- caudad area (retropulsion)
- Propels chyme into duodenum- caudad area (antral pump)
349
What is the contractile activity of the motility of the orad region?
Low amplitude contractions occur as meal empties
350
What is the receptive relaxation of the motility of the orad region?
Vagpvagal reflex:
- vagal afferent carry impulses to the CNS
- vagal efferent carry impulses from CNS to the stomach.
Vagotomy abolishes reflex
351
What is the gastric distensibility of the motility of the orad region?
CCK increases, decreasing gastric emptying
352
What are the factors that increase gastric emptying?
1. Increased tone of orad stomach
2. Forceful peristaltic contractions
3. Decreased tone of pylorus
4. Absence of segmental contractions in intestine
353
What are the factors that decrease gastric emptying?
• Activation of receptors in intestinal mucosa initiates enterogastric reflexes.
• This can decreases gastric emptying by:
1. Relaxation of orad stomach
2. Decreased force of peristaltic contractions
3. Increased tone of pyloric sphincter
4. Segmentation contractions in
intestine
354
Activation of intestinal receptors ____ gastric emptying
Activation of intestinal receptors *decreases* gastric emptying
355
What stimulates intestinal mucosa receptors?
High or low osmolarity, acid, fat, and protein
356
Examples of receptors that trigger enterogastric reflexes...?
- Fat/proteins - CCK release increases gastric distensibility
which decreases gastric emptying
- Acid - decreases gastric emptying (in 20-40s) via intrinsic neural reflex
- Involvement of other hormones - probably not
physiologic.
357
Hows does small intestine motility contribute to digestion and absorption?
- Mixing chyme with digestive enzymes and other secretions
- Circulation of chyme to achieve optimal exposure to mucosa
- Propulsion of chyme
358
Slow waves are more frequent in the ____ compared to the stomach
Slow waves are more frequent in the *small intestine* compared to the stomach
359
What are the two types of contraction that occurs in the small intestine and what do they do?
* Segmental contractions: mix the chyme
| * Peristaltic contractions: propel the chyme into the large intestine
360
Material that is not absorbed in the small intestine enters the ____ and is now called feces
Material that is not absorbed in the small intestine enters the *large intestine* and is now called feces
361
What are the function of the large intestine smooth muscle?
- Mixes feces: enhances fluid/electrolyte absorption (haustral contractions)
- Propels fecal material (mass movements)
362
____ occurs in the colon and function to move
| feces over long distances such as from the transverse colon to the sigmoid. This occurs 1-3x/day
*mass movements* occurs in the colon and function to move
| feces over long distances such as from the transverse colon to the sigmoid. This occurs 1-3x/day
363
Water absorption occurs in the ___ making the fecal contents semisolid and increasingly difficult to move
Water absorption occurs in the *distal colon* making the fecal contents semisolid and increasingly difficult to move
364
_____ leads to bowel movements
*mass movements* leads to bowel movements
365
What is rectosphincteric reflex?
As the rectum fills with feces the smooth muscle wall of the rectum contracts and the internal anal sphincter relaxes (involuntary control)
366
_____ will not occur until the external anal sphincter (voluntary control) relaxes
*Defecation* will not occur until the external anal sphincter (voluntary control) relaxes
367
When does the urge to defecate arise?
Once the rectum fills to 25%
368
What is gastrocolic reflex?
Distention of the stomach by food ingestion increases the motility of the colon and frequency of mass movements
369
Salivary secretion is produced by ___ at a rate of 1L/day
Salivary secretion is produced by *salivary glands* at a rate of 1L/day
370
____ is stimulated by both branches of ANS, few responses with PNS and SNS response
*Salivary secretion* is stimulated by both branches of ANS, few responses with PNS and SNS response
371
_____ produce primary secretion, similar to plasma
*Acinar cells* produce primary secretion, similar to plasma
372
____ cells modify the primary secretion
*Ductal* cells modify the primary secretion
373
What are the two main types of cells in salivary secretion?
- Acinar cells
| - Ductal cells
374
The faster the rate of salivary secretion, the ___ time ductal cells have to perform their actions
The faster the rate of salivary secretion, the *less* time ductal cells have to perform their actions
375
What are the actions of ductal cells?
- Na active absorption
- Cl passive absorption
- K active secretion
- HCO3 secretion
376
Acinar cells secrete ____ secretions
Isotonic secretions
377
What are the factors that stimulate the parasympathetic secretion of saliva?
- Conditioning
- Food
- Nausea
- Smell
378
What are the factors that inhibit the parasympathetic secretion of saliva?
- Dehydration
- Fear
- Sleep
379
What are the two types of glands in the stomach?
- Oxyntic glands
| - Pyloric glands
380
Where is the oxyntic glands and what do they contain?
The body of the stomach.
Contains parietal cells and chief cells
381
Parietal cells secrete ___ and ___
Parietal cells secrete *HCL* and *intrinsic factor (IF)*
382
Chief cells secrete ____, which becomes pepsin when there is low pH, starting the digesting proteins
Chief cells secrete *pepsinogen*, which becomes pepsin when there is low pH, starting the digesting proteins
383
Where is the pyloric glands and what do they contain?
In the antrum of the stomach
- G cells
- Mucus neck cells
384
G cells secrete ___
G cells secrete *gastrin*
385
Mucus neck cells secrete ____, ___ and ____
Mucus neck cells secrete *mucus, HCO3 and pepsinogen*
386
Cells of the gastric mucosa secrete ____
Cells of the gastric mucosa secrete *gastric juice*
387
What are the min components of gastric juice?
- HCL
- Pepsinogen
- Intrinsic factor
- Mucus
388
What are the 3 phases of gastric secretion?
- Cephalic phase
- Gastric phase
- Intestinal phase
389
______ is responsible for vitamin B12 absorption
*Intrinsic factor* is responsible for vitamin B12 absorption
390
____ phase happen via vagus nerves, meaning that they have the anticipatory response before you eat
*Cephalic* phase happen via vagus nerves, meaning that they have the anticipatory response before you eat
391
____ excite pepsin and acid production
*Parasympathetics* excite pepsin and acid production
392
____ is controlled by the local nervous secretory reflexes, vagal reflexes, and gastrin-histamine stimulation
*Gastric phase* is controlled by the local nervous secretory reflexes, vagal reflexes, and gastrin-histamine stimulation
393
______ phase work through nervous and hormonal mechanisms. When chyme reaches the intestine, it releases hormones
*intestinal* phase work through nervous and hormonal mechanisms. When chyme reaches the intestine, it releases hormones
394
What are the agents that stimulate H secretion by gastric parietal cells?
- Ach
- Gastrin
- Histamine
395
What pathway does Ach and gastrin work through?
A Gq pathway to activate the H-K ATPase pump
396
Histamine work through ___ mechanism on the H2 receptor, through ___ stimulatory pathways, increasing hydrogen ions secretion
Histamine work through *paracrine* mechanism on the H2 receptor, through *Gs* stimulatory pathways, increasing hydrogen ions secretion
397
What are the agents that inhibit H secretion by gastric parietal cells?
- Somatostatin
| - Prostaglandins
398
____ inhibit the ECL cells from releasing histamine and inhibit G cells
*Somatostatin* inhibit the ECL cells from releasing histamine and inhibit G cells
399
____ inhibits hydrogen ion secretion through the Gi pathway and the ECL cells from releasing histamine
*Prostaglandins* inhibits hydrogen ion secretion through the Gi pathway and the ECL cells from releasing histamine
400
Disorders of gastric H secretion leads to ___
Disorders of gastric H secretion leads to *ulcers*
401
Gastric ulcers and duodenal ulcers are ___ ulcers
Gastric ulcers and duodenal ulcers are *peptic* ulcers
402
What happens in a gastric ulcer?
- Decreased hydrogen secretion
- Increased gastrin levels, because of decreased hydrogen secretion
- Causes damage to protective barrier of gastric mucosa
403
What happens in a duodenal ulcer?
- Increased hydrogen secretion
- Increased gastrin levels in response to ingestion of food
- Increased parietal cell mass due to increased gastrin levels
404
What happens in the zollinger-ellison syndrome?
- Increased H secretion
- Increased gastrin levels
- Gastrin is secreted by pancreatic tumor
- Increased parietal cell mass due to trophic effect of increased gastrin levels
405
What are the protective factors of the protective barrier of the stomach?
- HCO3 and mucus
- Prostaglandins
- Mucosal blood flow
- Growth factors
406
What are the damaging factors of the protective barrier of the stomach?
- H and pepsin
- H. pylori (tested through the breath)
- NSAIDs
- Stress
- Smoking
- Alcohol
407
How does pancreatic secretion work?
- Acid from the stomach releases secretin from the wall of the duodenum; fats and amino acids cause release of CCK
- Secretin and CCK is absorbed into the blood stream
- Secretin causes copious secretion of pancreatic fluid and bicarbonate; CCK causes secretion of enzymes
408
____ works on pancreatic fluids and bicarbonate
*secretin* works on pancreatic fluids and bicarbonate
409
___ stimulates the release of enzymes
*CCK* stimulates the release of enzymes
410
How does bile secretion work?
1. Bile salts are formed in the liver
2. Bile salts are stored in the gallbladder which causes ions and water to be reabsorbed from them
3. CCK will cause contraction of the gallbladder and relaxation of the sphincter of oddi, causing the contents of the gall bladder to travel down the bile ducts, into the duodenum
4. At the ileum, bile salts get reabsorbed through the portal circulation, to the liver, and then recycled
411
What happens if you have too much bile salts or if it stays in the gallbladder too long?
It will solidify, which is how gall stones are created
412
What are the causes of gallstones?
- Too much absorption of water from the bile
- Too much absorption of bile acids from bile
- Too much cholesterol in the bile
- Inflammation of epithelium (reduced reabsorption/ obstruction of bile duct)
