Q2 Quiz #1 Flashcards
(184 cards)
1
Q
What makes up the GI system?
A
- GI tract
- salivary glands
- exocrine pancreas
- liver
- gallbladder
2
Q
GI fuction?
A
- motility
- secretion
- digestion
- absorption
3
Q
What are mixing movements?
A
mix food with digestive juices and helps with digestion and absorption
3
Q
What are dietary carbohydrates digested into?
A
monosaccharides (glucose)
3
Q
What are the two types of digestive motility?
A
- propulsive movements
- mixing movements
4
Q
What are propulsive movements?
A
push contents forward through digestive tract
5
Q
What are dietary proteins digested into?
A
amino acids
small polypeptides
6
Q
What are dietary fats digested into?
A
monoglycerides
free fatty acids
7
Q
Most absorption is completed where?
A
small intestine
8
Q
The intrisic nerve plexus is part of specifically what nervous system?
A
enteric nervous system
9
Q
What does the intrinsic nerve plexus effect?
A
- smooth muscle
- exocrine gland cells
- endocrine gland cells
10
Q
What does the extrinsic autonomic nerves effect?
A
- intrinsic nerve plexuses
- gastrointestinal hormones
- smooth muscle
- exocrine gland cells
- endocrine gland cells
11
Q
What are some external influences of the GI regulation?
A
feeling nervous
(change bowl movement because stimulus that changes CNS can change balance of autonomic system –> change digestive system)
12
Q
What is the swallowing reflex initiated by?
A
stimulus of pressure receptors in pharynx
12
Q
What is the swallowing reflex controlled by?
A
swallowing center in medulla
13
Q
What is inhibited during swallowing?
A
respiration
13
Q
What are the two stages of swallowing
A
- oropharyngeal stage
- esophageal stage
14
Q
What is the oropharyngeal stage?
A
moves bolus from mouth –> pharynx –> esophagus
15
Q
What is the esophageal stage?
A
moves bolus by peristalsis through esophagus –> stomach
16
Q
What is the peristalsis movement?
A
muscle “behind” contracts
muscle “ahead” relaxes
17
Q
Describe gastric emptying and mixing
A
- peristaltic contration originates in fundus –> pyloric sphincter
- becomes vigorous when reach antrum
- strong contraction propels chyme forward
- small portion of chyme pushes through partially open sphincter in duodenum
- when peristaltic contraction reaches sphincter, it will CLOSE (no more leakage)
- chyme will be tossed back into antrum and will continue with each peristaltic contraction (mixing)
18
Q
When fat is in the duodenum, what is released?
A
CCK
18
Q
The presence of fat, acid, hypertonicity, or distension within the duodenum triggers what?
A
enterogastric reflex
release of enterogastrones
secretin, cholecytokinin
inhibit further gastric motility and emptying until duodenum has coped with factors alr present
SLOW DOWN MOTILITY (slow down the stomach for duodenum to catch up)
19
Q
Where is the stimulation of the enterogastric reflex?
A
the small intestine
20
When acid is in the duodenum, what is released?
secretin
21
Which would have a higher frequency? A pacemaker at the beginning of the small intestine or a pacemaker at the end of the small intestine?
pacemaker at BEGINNING of small intestine
each successive pacemaker has a slightly lower frequency
22
Where does the effect of the enterogastric reflex take place?
in the stomach
(inhibit motility and secretion)
23
What is within the walls of the small intestine?
series of pacemakers
24
What is the function of the frequency "gradient"?
pushes chyme towards the large intestine (peristalsis)
25
What separates the large and small intestine?
1. ileocecal sphincter
2. ileocecal valve
separation is IMPORTANT bc large intestine has a lot of bacteria
25
What are the types of movement in the small intestine?
1. peristalsis (push towards large intestine)
2. segmentation (mixing back and forth with secretions throughout the intestine)
26
Where is the appendix located?
Lower right quadrant
27
What is the gastrocolic reflex?
stimulation in the stomach
effect in the colon
SIGNAL FROM STOMACH TO FORCE UNABSORBED MATERIAL THROUGH COLON TO MAKE SPACE FOR NEW MATERIAL
28
What is the duodenocolic reflex?
stimulate in the duodenum
effect in the colon
SIGNAL FROM THE DUODENUM TO CLEAR THE LUMEN OF THE COLON TO GET READ FOR THE FRESH CONTENT
29
What is the defecation reflex?
regulation of internal anal sphincter to relax
30
What type of muscle is the internal anal sphincter and is it voluntary or involuntary?
smooth muscle
involuntary
31
What type of muscle is the external anal sphincter and is it voluntary or involuntary?
skeletal
voluntary
32
The organs ____________ (upstream/downstream) in the GI tract ___________ (promote/inhibit) motility of organs ________________ (upstream/downstream) in the GI tract
upstream | promote | downstream
OR
downstream | inhibit | upstream
33
Is the gastro/colic reflex excitatory or inhibitory?
EXCITATORY
STIMULATE IN STOMACH
EFFECT IN LARGE INTESTINE
stomach sends signals that new fresh content is coming to accelerate motility of the colon
34
Is the gastro/gastric reflex excitatory or inhibitory?
EXCITATORY
LOCAL STIMULATION
35
Is the gastro/enteric reflex excitatory or inhibitory?
EXCITATORY
STIMULATE IN STOMACH
EFFECT IN INTESTINES
stomach sends signals that new fresh content is coming and promotes intestinal motility
36
Is the duodeno/colic reflex excitatory or inhibitory?
EXCITATORY
36
Is the gastro/ilieal reflex excitatory or inhibitory?
EXCITATORY
37
Is the entero/gastric reflex excitatory or inhibitory?
INHIBITORY
STIMULATE IN INTESTINES
EFFECT IN STOMACH
intestines stimulate that there is content in the intestines and need stomach to slow down so will decrease motility of stomach
38
What is is the secretion, major content, and digestion of the salivary gland?
saliva
amylase
carbohydrates
38
What is is the secretion, major content, and digestion of the esophagus?
N/A (secretes nothing)
mucus
N/A (digests nothing)
39
What is is the secretion, major content, and digestion of the stomach?
gastric juice
HCl, pepsin, intrinsic factor (IF), gastrin
proteins and lipids
40
What is is the secretion, major content, and digestion of the small intestine?
intestinal juice
secretin, CCK, GIP
N/A (nothing is digested)
41
What is is the secretion, major content, and digestion of the liver?
bile
bile salts, bilirubin
lipid
41
What is is the secretion, major content, and digestion of the pancreas?
pancreatic juice
NaHCO3, major digestive enzymes
carbohydrates, protein, lipids
42
What is is the secretion, major content, and digestion of the large intestine?
N/A (secretes nothing)
NaHCO3, mucus
N/A (digests nothing)
42
What are cells of the stomach involved in exocrine secretment?
1. mucous cells (mucus)
2. chief cells (pepsinogen)
3. parietal cells (HCl/IF)
43
What are cells of the stomach involved in endocrine secretment?
1. Enterochromaffin cells (histamine)
2. G cells (gastrin)
3. D cells (somatostatin)
44
What are mucous cells activated by?
mechanical stimulation/force by the stomach
create barrier to protect gastric mucosa
45
What are chief cells activated by?
ACh and gastrin
46
What are the four layers of barrier to protect the gastric mucosa?
1. luminal membrane of gastric mucosal cells are impermeable to H+ (STOMACH IS HIGHLY ACIDIC)
2. tight junction to prevent HCl penetration
3. mucous barrier to protect gastric mucosa
4. HCO3- rich mucus to neutralize acid
47
Where is pepsinogen stored?
in chief cells as zymogen granules (inactivated enyzmes)
48
What is pepsinogen activated by and what does it do?
HCl in lumen
digest protein into polypeptides
49
What is the function of parietal cells?
Secretion of HCl aka GASTRIC ACID
Secrete intrinsic factor (IF)
50
What are parietal cells activated by?
ACh
gastrin
histamines
51
What is the autocatalytic function of pepsinogen/pepsin?
POSITIVE FEEDBACK
pepsin can promote the conversion of pepsin --> pepsinogen
52
What is pH in stomach?
2
53
How do parietal cells produce HCl?
1. protons are from water (H2O --> H+ + OH-)
2. H+ pumped into lumen by H+-K+ ATPase pump
3. OH- combine with CO2 --> HCO3- (carbonic anhydrase)
4. HCO3- enters plasma by Cl- - HCO3- antiporter (secondary active transport)
5. Cl- diffuse into lumen
NOW H+ AND Cl- ARE IN LUMEN TOGETHER
parietal cell is basically used as transporter between plasma and gastric lumen to construct HCl in lumen
54
What is pH of blood?
7.4
55
How to calculate [H+] in stomach relative to [H+] in blood?
[H+] stomach/[H+] blood
56
What are ways to reduce acid in stomach?
inhibit the proton pump (H+-ATPase pump)
antihistamines (to target hormones stimulating the production of acid)
56
What is the function of [H+] in stomach?
aids in breakdown of CT and muscle fibers
denatures proteins
kills most of microorganisms ingested with food
57
What is the main function of parietal cells releasing intrinsic factor (IF)?
Vitamin B12 absorption in the ileum
**only at the ileum because the only one that has the receptors for vitamin B12 absorption**
58
What are the gastric secretion phases?
1. cephalic phase: stimulation in the head region (sight/smell/taste/thoughts) --> PARASYMPATHETIC stimulation --> salivation, etc
2. gastric phase: food content is in the stomach, release of secretagogues (substances that promote secretion like ACh, gastrin, histamines) --> secretion of HCl, pepsinogen, and IF
3. intestinal phase: now content flows into the duodenum (chyme in duodenum --> duodenal secretions + enterogastric reflex --> inhibit stomach motility and secretions)
4. duodenal secretions: enterogastrones (secretin, CCK) enterokinase, and glucose-dependent insulinotropic peptide-GIP
58
What occurs when there is an absence of intrinsic factor?
decrease IF --> vitamin B12 deficiency --> pernicious anemia (fragile RBC = megaloblast)
59
What does gastrin do?
1. increase secretion of HCl and pepsinogen
2. enhance gastric motility and ileal motility
3. trophic (growth effect) to the stomach and intestine mucosa
59
What causes CCK to be released?
protein peptides, and fat in the duodenum
60
What causes the release of secretin in the small intestine?
When the duodenum pH < 4.5
61
What does secretin do?
1. inhibits HCl secretion in stomach
2. inhibit gastric emptying (motility)
3. stimulate NaHCO3 secretion to keep duodenal pH above 4.5
4. stimulate liver to secrete bile
5. stimulate pancreas
62
What does CCK do?
1. production of bile with the contraction of the gallbladder
2. pancreatic enzyme secretions
3. inhibiting gastric empty (motility) and gastric acid secretion (want to keep stomach full)
4. satiety (feeling full)
63
What is the process of the reabsorption of NaCl and water in the small intestine?
1. Cl- uptake through K-2Cl symporter into the epithelial cells in small intestine
2. Adenylyl cyclase activated --> generates cAMP --> activates CFTR (cystic fibrosis transmembrane)
3. Cl- diffuses through activated CFTR (epithelial cells --> lumen)
4. Na+ diffuses through leaking tight junctions
5. H2O enters lumen by osmosis
64
What cells in the pancreas secrete digestive enzymes?
acinar cells
65
What cells in the pancreas secrete NaHCO3?
Duct cells
66
What cells in the pancreas secrete insulin and glucagon?
Endocrine secretion Islets
67
What are some protein digesting enzymes in the pancreas?
1. trypsinogen
2. chymotrypsinogen
3. procarboxypeptidase
68
The protein digesting enzymes are inactive in the pancreas. Where and what activates them?
DUODENUM
enterokinase (enteropeptidase) or activated trypsin
69
Bile is _______________ (continuously/periodically) released by the ________ and diverted to the __________ between meals.
continuously
liver
gallbladder
69
What is the carbohydrate digestion enzyme?
pancreatic amylase
70
What is the process of NaHCO3 secretion in the pancreas and intestines?
1. Most HCO3- enter duct cell through the Na+-HCO3- symporter
2. Some HCO3- is generated in duct cell through carbonic anhydrase activity
3. HCO3- enter lumen by Cl- - HCO3- antiporter or CFTR channel
4. Na+ diffuse into lumen through leaky tight junctions
NOW Na+ AND HCO3- ARE IN THE LUMEN
71
What is the fat digesting enzyme?
Pancreatic lipase
72
What type of factor promotes the secretion of bile?
Choleretic factors (bile salts, CCK, secretin, and vagus nerve aka parasympathetic)
73
Bile salts are recycled through what?
enterohepatic circulation
74
What pigment causes jaundice?
bilirubin
75
Does the pH increase or decrease or fluctuate as we go through the GI tract?
DECREASE
(2 in stomach --> 5 in small intestine --> 8 in large intestine)
**numbers not important**
76
What is the enterohepatic circulation of bile salts?
1. bile salts are produced in the liver and temporarily stored in the gallbladder
2. local/hormonal/intrinsic factors stimulate the release of bile into the duodenum
3. after job is done, 95% of bile salts are reabsorbed at the ileum (the rest is lost in the feces)
4. reabsorbed bile salts go into the hepatic portal vein
5. goes back to liver to be reused and recycled
77
What is the pathway of absorption through the villi?
1. pass through epithelial cell
2. diffuse through interstitial fluid
3. enter into capillary (if small enough) or lymphatic vessel (if large, will eventually merge with blood circulation)
78
What are the different types of Na+ absorption?
1. passive diffusion through leaky tight junctions
2. passive diffusion through Na+ channels
3. active transport through Na+-Cl- symporter, Na+-H+ antiporter, Na+-glucose symporter OR Na+-amino aicd symporter
4. active transport powered by Na+-K+ ATPase pump at the basal lateral membrane
79
What type of dietary carbohydrate needs to be digested more?
starch
glycogen
80
When sodium is being absorbed, what is being created?
osmotic gradient
MEANS WATER WILL FOLLOW
81
What enzymes digest polysaccharides?
salivary amylase
pancreatic amylase
82
What converts disaccharides into monosaccharides (glucose/galactose/fructose)?
lactase
malatase
sucrase-isomaltase
83
What is the process of carbohydrate absorption?
1. Carbohydrates are broken down
2. monosaccharides glucose/galactose are absorbed into epithelial cells by SECONDARY ACTIVE TRANSPORT (SGLT)
4. fructose enters through passive facilitated diffusion (GLUT-5)
5. monosaccharides exit cell at BASAL MEMBRANE by GLUT-2 (passive facilitated diffusion)
84
What is the process of protein digestion?
1. proteins are broken down into amino acids
2. amino acids are absorbed by epithelial cells by SYMPORTER (secondary active transport)
3. small peptides are absorbed by SYMPORTER (tertiary active transport)
4. small peptides --> amino acids by intracellular peptidases
5. amino acids exit cell by PASSIVE CARRIERS
6. amino acids enter blood by SIMPLE DIFFUSION
85
What is the process of fat digestion?
1. triglycerides are emulsified by bile salts --> fat droplets
2. pancreatic lipase turn triglycerides --> monoglycerides and free fatty acids
3. water soluble micelles move to small intestine epithelial cells
4. monoglyceride and fatty acid PASSIVELY DIFFUSE through lipid bilyaer
5. resynthesized into triglycerides inside epithelial cells
6. triglycerides are coated with layer of lipoprotein to produce chylomicrons
7. chylomicrons are sent through basal membrane through EXOCYTOSIS
8. Chylomicrons enter lymphatic vessels
86
How is vitamin B12 absorbed?
Vitamin B12 bind to an intrinsic factor and is absorbed in the end of the ileum
87
How is calcium absorbed in the small intestine?
1. passively absorbed through IMCal
OR
2. Bind to Calbindin (calcium binding protein)
OR
3. actively transported through Ca2+ ATPase pump or Na+ - Ca2+ antioporter
88
What is the relationship between activated Vitamin D and calcium?
ACTIVATED VITAMIN D ENHANCES CALCIUM ABSORPTION
89
How do nutrients get to the rest of the body?
1. HEPATIC PORTAL CIRCULATION -->general circulation
2. absorbed fat enters lymphatic system --> blood circulation
90
What are the two types of nephrons?
1. cortical nephron (short)
2. juxtamedullary nephron (long)
91
What are the two components of a nephron?
1. vascular component
2. tubular component
92
What is the vascular component of the nephron and their functions?
1. afferent arteriole (blood to glomerulus)
2. efferent arteriole (blood from glomerulus)
3. glomerulus (capillaries that filter a PROTEIN-FREE plasma into tubular component)
4. peritubular capillaries (exchange of ions/fluids)
93
What is included in the tubular component of the nephron?
1. bowman's capsule
2. proximal convoluted tubule
3. loop of Henle
4. distal convoluted tuule
5. collecting duct
94
What occurs in the Bowman's capsule?
collects the glomerular filtrate
WHERE THE TUBULAR COMPONENT STARTS
95
What does the proximal convoluted tubule do?
UNCONTROLLED reabsorption and secretion of selected substances
96
What does the distal convoluted tubule and collecting duct do?
VARIABLE, CONTROLLED reabsorption of Na+ and H2O
secretion of K+ and H+
fluid leaving collecting duct is urine
97
What are the characteristics of the cortical nephron?
1. outer layer of the cortex
2. SHORT Loop of Henle
MAJORITY OF NEPHRONS
97
What does the juxtaglomerular apparatus do?
produces substances involved in control of kidney function
97
What is the combined vascular/tubular component?
juxtaglomerular apparatus
98
What are the characteristics of the juxtamedullary nephron?
1. inner layer of cortex
2. LONG loop of Henle
3. Vasa recta
99
Where does majority of the plasma that enters the glomerulus go?
EFFERENT ARTERIOLE (80%)
majority is NOT filtered and leaves through efferent arteriole
20% is filtered into PCT
100
What are the three major functions of the nephron?
1. glomerular filtration (PROTEIN-FREE PLASMA --> tubular component)
2. tubular reabsorption (tubular lumen --> peritubular capillary blood)
3. tubular secretion (peritubular capillary blood --> tubular lumen)
101
How to calculate urine excretion?
Urine = GF - TR + TS
GF = GLOMERULAR FILTRATION
the total volume entering in for filtration
TR = TUBULAR RESORPTION
the volume that is reabsorbed from the tubular lumen --> peritubular capillary blood
TS = TUBULAR SECRETION
the volume that is excreted from the peritubular capillary blood (filtered through the SECOND time)
102
How is glomerular filtrate produced?
When plasma is passively forced through the glomerular membrane --> Bowman's capsule
ONLY A MINORITY GETS THROUGH
103
What layers must the fluid be filtered through to get from the glomerular membrane --> Bowman's capsule?
1. endothelial cells of glomerular capillary
2. acellular basement membrane
3. podocytes of visceral layer of Bowman's capsule (foot protrusions)
103
What can NOT pass through the triple-layer capillary wall of the glomerulus?
1. small proteins (usually filtered back into PCT by endocytosis, ex: myoglobin)
2. large proteins (albumin/hemoglobin)
3. negatively charged ions (basement membrane is negatively charged; WILL REPEL)
104
What is the difference between the filtered fluid in the Bowman's capsule and plasma?
LITTLE TO NO PLASMA PROTEINS AND NO RBC in filtered fluid
105
What can get through the triple-layer capillary wall of the glomerulus?
1. water
2. small solutes (Na+, K+, amino acids, glucose, urea, etc)
106
What physical forces are involved in filtration?
1. glomerular capillary blood pressure (blood in glomerulus will drive filtration) (+ favor filtration)
2. plasma-colloid osmotic pressure (proteins within capillaries will try to hold water around those proteins) (- oppose filtration)
3. Bowman's capsule hydrostatic pressure (tries to push fluid back into the capillaries) (- oppose filtration)
107
How to calculate the net filtration pressure?
Glomerular capillary blood pressure - plasma-colloid osmotic pressure - Bowman's capsule hydrostatic pressure
108
Describe the glomerular capillary blood pressure.
Diameter of afferent is LARGER than efferent
BECAUSE EFFERENT IS SO SMALL, THE BLOOD BUILDS UP BEHIND IT (within the glomerulus)
Therefore, the blood pressure IN THE GLOMERULUS is higher than other capillaries
109
What is the main force for glomerular filtration?
GLOMERULAR CAPILLARY BLOOD PRESSURE
110
What does the glomerular filtration rate (GFR) depend on?
1. net filtration pressure
2. glomerular surface area
3. permeability
111
What is the Kf?
takes into account glomerular SA and permeability
112
When podocytes _______________ (relax/contract), the Kf _______________ (increases/decreases). This means ______________ (more/less) filtration
relax/increases/more
OR
contract/decreases/less
**IMAGINE A HAND PRESSING AGAINST THE MOUTH; IF TOO LOOSE, SOUND WILL STILL COME OUT; IF PLACED TIGHTER PRESSING DOWN MORE, SOUND WILL NO LONGER COME OUT**
113
What regulates GFR (glomerular filtration rate) and what exactly is regulated?
1. autoregulation (kidney tries to control itself)
a. myogenic mechanism (respond to pressure in vascular component)
b. tubuloglomerular feedback (respond to salt level in filtrate)
2. sympathetic control (control how much blood flows to the kidneys)
BOTH CONTROL GFR BY REGULATING RADIUS OF AFFERENT ARTERIOLE (how much blood flows into the glomerulus)
114
What is the effect on GFR if arterial blood pressure increases WITHOUT REGULATION?
1. increase arterial blood pressure
2. increase blood flow into afferent arteriole --> glomerulus
3. increase glomerular capillary blood pressure
3. increase net filtration pressure (GCBP - PCOP - BCHP)
4. increase GFR
**WITHOUT REGULATION, INCREASING BLOOD PRESSURE WILL INCREASE GFR**
115
What is the myogenic mechanism effect during increased arterial blood pressure?
1. increase arterial blood pressure
2. smooth muscle stretches due to increased blood pressure
3. VASOCONTRICTION
4. decreases blood flow into glomerulus
5. decrease glomerular capillary blood pressure
6. decrease net filtration pressure
7. decrease GFR
**DURING THE MYOGENIC MECHANISM, THE SMOOTH MUSCLE STRETCH IS DETECTED AND VASOCONTRICTION TO PUSH AGAINST THAT STRETCH IS EMPLOYED = DECREASE AMOUNT OF BLOOD FLOWING THROUGH THE AFFERENT ARTERIOLE**
115
What occurs during tubuloglomerular feedback if there is an increase in GFR?
1. Increased GFR
2. more water/NaCl filtered into Bowman's capsule
3. travels to juxtaglomerular apparatus
4. macula densa cells sense increased flow and NaCl
5. MACULA DENSA CELLS RELEASE VASOCONSTRICTORS (ATP/adenosine)
6. afferent arterioles constrict
7. decrease blood flow through kidney/glomerulus and GFR
**INCREASE GFR = INCREASED WATER/NaCl THAT GETS THROUGH TO THE BOWMAN'S CAPSULE; MACULA DENSA IN THE JUXTAGLOMERULUS APPARATUS SENSE THE INCREASE IN THOSE AND SENDS OUT VASOCONSTRICTORS; DECREASES AA --> DECREASE BLOOD FLOW THROUGH GLOMERULUS --> DECREASE GFR**
116
What is the myogenic mechanism effect during decreased arterial blood pressure?
1. decreased arterial blood pressure
2. smooth muscle relaxes due to decreased blood pressure within
3. VASODILATION
4. increase blood flow into glomerulus
5. increases glomerular capillary blood pressure
6. increases net filtration pressure
7. increases GFR
**THE GOAL IS TO RAISE BACK UP THE BLOOD PRESSURE SO IT VASODILATES THE AFFERENT ARTERIOLE TO INCREASE BLOOD FLOW INTO THE GLOMERULUS**
117
What is the difference between blood pressure changes and renal blood flow/GFR in terms of stability?
though blood pressure fluctuates constantly throughout the day, renal blood flow/GFR remain relatively stable though depending on the blood pressure as the blood supply
**SHOWS THE IMPORTANCE AND CONSTANT AUTOGENIC REGULATION**
117
What occurs during tubuloglomerular feedback if there is a decrease in GFR?
1. Decreased GFR
2. less water/NaCl filtered into Bowman's capsule
3. travels to juxtaglomerular apparatus
4. macula densa cells sense decreased flow and NaCl
5. MACULA DENSA CELLS RELEASE VASODILATORS (nitric oxide/NO)
6. afferent arterioles dilate
7. increased blood flow through kidney/glomerulus and GFR
118
What is the sympathetic control over the GFR
1. increase sympathetic response --> increase heart rate --> increase arterial blood pressure --> increase GFR
2. generalized alpha1 receptor vasoconstriction increases TPR (force of circulating blood) --> increase blood pressure --> reduces bleeding
3. alpha1 receptor constriction of renal afferent arterioles --> decreases renal blood flow --> decrease afferent arteriole flow --> decrease GFR --> conserve body water
4. beta1 receptor promote renin secretion from granular cells in afferent arterioles
119
What is the sympathetic effect on kidneys in response to hemorrhage (bleeding)?
1. decrease GFR
2. increase salt and H2O reabsorption
**tries to bring blood volume back up to normal by changing the function of the kidneys**
120
What is tubular reabsorption and what do the substances cross?
Filtrate --> plasma
1. luminal cell membrane
2. cystol (of luminal cell)
3. basolateral cell membrane
4. interstitial fluid
5. capillary wall
121
Na+ tubular reabsorption happens where?
EVERYWHERE THROUGHOUT THE TUBULE EXCEPT THE DESCENDING LIMB OF THE LOOP OF HENLE
121
What is reabsorbed back into the peritubular capillaries?
1. water (majority)
2. sodium (majority)
3. glucose (all of it)
4. urea (50% of it)
122
Describe sodium reabsorption in the proximal tubule?
secondary active transport
(moved across the membrane with another molecule X)
carrier specific
Cl- and H2O follow passively (+/- attraction and osmotic pressure)
123
Describe water reabsorption in the proximal tubule?
AQP1 water channels OR leaky tight junction
majority of water reabsorption occurs in proximal tubule
124
Where does water reabsorption occur?
1. proximal tubule
2. distal/collecting tubule (controlled by vasopressin)
3. loop of Henle (maintains vertical osmotic gradient)
125
Describe glucose reabsorption in the proximal tubule?
Filtered load = GFR * P(glucose)
Tm = maximum reabsorption rate of glucose/substances
126
What is renal threshold?
PLASMA CONCENTRATION AT WHICH THE SUBSTANCE CAN BE FILTERED, IT DOES NOT MEAN THAT IT WILL BE REABSORBED
EX. IF THERE IS TOO MUCH GLUCOSE, THE TUBULAR MAXIMUM WILL BE FILTERED AND REABSORBED BUT THE REST WILL BE FILTERED AND EXCRETED
127
What does tubular maximum mean?
WHEN ALL CARRIERS/THE MAXIMUM LOAD HAS BEEN REACHED/SATURATED
128
Describe urea reabsorption in the proximal tubule?
urea is concentrated while passing to proximal convoluted tubules
urea PASSIVELY DIFFUSES from tubular lumen --> capillary plasma (50%)
some is excreted, some is reabsorbed back (50%)
129
What is the vertical osmotic gradient?
solute concentrations increase from cortex --> renal papilla to facilitate the concentration of urine and reabsorption of water
130
What are the parts of the loop of Henle?
1. descending limb (permeable to water, NOT permeable to Na+)
- WATER MOVES OUT OF LUMEN
2. ascending limb (NOT permeable to water, active transport of Na+)
- Na+ MOVES OUT OF LUMEN
131
What is countercurrent flow?
when the current flows one way but then makes a hairpin turn and goes the opposite direction
132
What is countercurrent multiplication?
1. New fluid (300) goes into descending limb, pushing osmotically stable fluid (200) OUT of the ascending limb
2. ascending limb pumps Na+ out to get back to stable (300 --> 200)
3. continues until back to their stable osmotic level
THE ORIGINAL GOAL IS TO KEEP THE STABILITY OF EACH LIMB
DESCENDING LIMB CONCENTRATION (pump out H2O) IS HIGHER THAN ASCENDING LIMB (pump out Na+)
133
What is the osmotic gradient estabilished in?
In the medulla by the long loop of Henle (juxtamedullary nephrons)
134
The final vertical osmotic gradient is established and maintained by what?
ongoing countercurrent multiplication of the long loops of Henle
135
Vasa recta capillaries are permeale to what?
NaCl
H2O
136
Describe Na+ reabsorption in the distal tubules and collecting ducts.
Na leaky channels
regulated by renin-angiotensin-aldosterone system (RAAS)
137
NaCl ____________ (retention/excretion) leads to H2O ______________ (retention/excretion)
retention/retention
OR
excretion/excretion
137
What are the steps of releasing renin?
1. Macula densa cells sense low flow and low NaCl
2. stimulate granular cells to secrete renin
3. granular cells secrete renin into bloodstream
OR
1. Granular cells sense low blood pressure in afferent arteriole
2. granular cells secrete renin into bloodstream
138
Describe the steps of the RAAS.
1. ANGIOTENSINOGEN is released by the liver
2. RENIN is produced by the kidneys and converts ANGIOTENSINOGEN --> ANGIOTENSIN I
3. in the liver, an enzyme converts ANGIOTENSIN I --> ANGIOTENSIN II
4. ANGIOTENSIN II in the adrenal cortex causes the release of ALDOSTERONE
139
What is renin secreted in response to?
1. sympathetic stimulation (beta1 receptors)
2. reduced bp in afferent arteriole (sensed by granular cells)
3. reduced flow/NaCl sensed y macula densa
140
What are the effects of angiotensin II?
1. Vasopressin (increase H2O reabsorption in kidneys)
2. Thirst
3. Arteriolar vasoconstriction (decrease glomerular blood pressure, decrease GFR)
4. Production of aldosterone (increase Na+/H2O reabsorption)
141
What is the effect of aldosterone on Na+ reabsorption?
ALDOSTERONE INCREASES Na+ REABSORPTION
secreted by adrenal cortex
increases number of Na+ leaky channels and Na+-K+ pumps in distal tubules
142
Describe water reabsorption in the distal tubules and collecting ducts.
distal/collecting tubule impermeable to H2O
UNLESS IN THE PRESENCE OF ADH
graded effect (effect increases with the stimulation)
143
What can counteract the RAAS system?
Natriuretic peptides
144
What is the effect of ADH?
PROMOTES THE INSERTION OF AQUAPORINS (AQP2) INTO THE LUMINAL MEMBRANE
ADH DECREASES WATER EXCRETED AND INCREASES WATER REABSORBED
145
Vasopressin (ADH) acts upon what?
principal cell in the distal or collecting tubule
146
What is antidiuresis?
the process of reducing or stopping the excretion of urine
WHEN ADH/VASOPRESSIN IS PRESENT
INTRODUCES AQUAPORINS TO THE DISTAL AND COLLECTING DUCT TO ALLOW WATER TO BE LET OUT AND REABSORBED
small volume of concentrated urin is excreted
147
What is the process of tubular secretion of K+?
1. K+ is reabsorbed by proximal tubule
2. K+ is secreted by principle cells in distal and collecting tubules
OR
2. K+ is secreted through K+ leaking channels
148
What is aldosterone control on K+ secretion?
ALDOSTERONE INCREASE K+ SECRETION
aldosterone increases the number of Na+ leaky channels and Na+ - K+ pumps in the principal cells of distal/collecting tubules
**ALWAYS PROMOTES Na+ REABSORPTION AND K+ SECRETION**
149
What are some stimuli for aldosterone release?
low ECF volume
low flow
low BP
low Na load
higher K load
ALDOSTERONE IS USED TO RESTORE OR RAISE BLOOD VOLUME
150
Is the reabsorption and secretion in the proximal tubule controlled or uncontrolled?
UNCONTROLLED
151
What controls the final amounts of H2O, Na+, K+, and H+ excreted in urine?
REABSORPTION AND SECRETION IN THE DISTAL TUBULE AND COLLECTING DUCT
**since highly regulated, it will have the most control in regulating the levels of ions as compared to proximal absorption/secretion**
151
Is the reabsorption and secretion in the distal tubule/collecting duct controlled or uncontrolled?
CONTROLLED
regulated
152
What is plasma clearance?
effectiveness of kidney in removing a particular substance from the plasma
153
How calculate plasma clearance?
Clearance rate * plasma concentration of the substance
154
What is clearance rate?
volume of plasma cleared of a particular substance each minute by the kidney
155
What is the relationship between urine excretion and plasma clearance?
Urine excretion = plasma clearance
156
How does insulin go through a nephron?
FOREIGN CARBOHYDRATE SUBSTANCE
FREELY FILTERED
NOT SECRETED OR REABSORBED
157
What is used clinically to determine GFR?
Insulin (since not reabsorbed or secreted)
Creatinine
158
What is the difference between insulin and creatinine in terms of GFR?
insulin: not secreted + not reabsorbed
creatinine: SLIGHTLY SECRETED + not reabsorbed
159
If a substance is freely filtered and not secreted or reabsorbed, the GFR ____ (=, >, <) clearance rate.
GFR = clearance rate
160
If a substance is filtered and reabsorbed but no secreted or little secretion, the GFR ____ (=, >, <) clearance rate.
GFR > clearance rate
161
What is PAH?
Organic anion not naturally found in humans
161
If a substance is filtered and secreted but no reabsorption or little reabsorption, the GFR ____ (=, >, <) clearance rate.
GFR < clearance rate
