Physiology Midterm 2 Flashcards
(326 cards)
1
Q
What is the number role of the kidneys?
A
Regulation of extracellular fluid volume and blood pressure
2
Q
Role of the kidney?
A
- Regulation of extracellular fluid and blood pressure 2. Regulate plasma osmolarity 3. Regulates ion balance 4. Regualtes plasma pH 5. Excretion of waste (endogenous and exogenous) 6. Endocrine (erythropoietin and renin and Ca2+ homesostasis)
3
Q
Location of a cortical nephron?
A
Stays in the cortex of the kidney
4
Q
Location of a juxtamedullary nephron?
A
Dives down from cortex into the medulla of kidney
5
Q
How many portal systems are there in the body?
A
3 (2 capillary beds…hypothalamus/ant. pit. and kidney and liver)
6
Q
Renal portal system for a cortical nephron?
A
Renal artery, branches of smaller arteries then arterioles in cortex, afferent arterioles, glomerular capillaries, efferent arterioles, peritubular capillaries, venules, veins, renal vein, vena cava
7
Q
Renal portal system for a juxtamedullary nephron?
A
Renal artery, branches of smaller arteries then arterioles in cortex, afferent arterioles, glomerular capillaries, efferent arterioles, peritubular capillaries, vasa recta, venules, veins, renal vein, vena cava
8
Q
What is the juxtaglomerular apparatus?
A
Association between ascending limb of Loop of Henle and afferent/efferent arteriole
9
Q
What is the renal corpuscle?
A
Glomerulus and Bowman’s capsule
10
Q
How much plasma does the kidney process per day, and how much urine is excreted?
A
180 L/plasma per day and 1.5L urine/day
11
Q
How much of the fluid that passes through the kidneys reabsorbed?
A
99%
12
Q
Where does filtration happen in the kidney?
A
Renal corpuscle (glomerulus and Bowman’s capsule)
13
Q
Equation for the amount of urine excreted?
A
Amount filtered - amount reabsorbed + amount secreted = amount excreted
14
Q
Where is the filtrate from the kidney most similar to plasma?
A
At the renal corpuscle…the only thing that is different is it doesn’t have blood cells and less protein
15
Q
Where does iso-osmotic reabsorption occur?
A
The proximal tubule (70% of fluid and solute is reabsorbed)
16
Q
By the time the fluid in the kindeys gets to the ascending loop of Henle, how much of the filtrate has been reabosorbed?
A
90%
17
Q
Where does reabsorption happen in the kidneys?
A
All along the peritubular capillaries from the proximal tubule to the collecting duct
18
Q
Where does fine tuning and water/salt balance and endocrine control happen in the kidney?
A
The distal tubule/collecting duct
19
Q
How much of the plasma moves out of the glomerular capillaries into the tubules?
A
approximately 20%, with the rest entering the efferent arterioles
20
Q
What is the filtration fraction?
A
% of total plasma volume that enters into tubule
21
Q
Barriers to filtration in the renal corpuscle?
A
Glomerular capillary endothelium, basement membrane, epithelium of Bowman’s capsule
22
Q
How does the endothelium of glomerular capillaries create a barrier to filtration?
A
The fenestrated capillaries allow most substances to pass except for blood cells and most proteins (repelled by negatively charged proteins on pore surfaces)
23
Q
How does the basement membrane act as a barrier to filtration in the renal corpuscle?
A
It is a layer of ECM between capillary endothelium and epithelium of Bowman’s capsule. It acts as a coarse sieve, keeping most proteins in plasma
24
Q
How does the epithelium of Bowman’s capsule act as a barrier to filtration?
A
It has gaps between foot processes of podocytes that leave narrow slits close my semi-porous membrane
25
What are the 2 unique proteins that are expressed of the membrane of the filtration slits in the kidney?
Nephrin and podocin
26
What force is driving filtration in the glomerulus?
Hydrostatic pressure and the leakiness of the barrier keep net filtration HIGH...GFR = 180 L/day, plasma volume is approx. 3 L
27
Factors that influence GFR?
Net filtration pressure and filtration coefficient (surface area of glomerular capillaries and permeability of the interface)
28
Is GFR influences by changes in blood pressure?
NO, lots of autoregulation
29
If the resistance in the afferent arteriole of the kidney increased what would happen?
Renal blood flow would decrease, hydrostatic blood pressure would drop, lowering GFR
30
What would happen if resistance in the efferent arteriole in the increased?
Renal blood flow would decreases, but hydrostatic increases, which INCREASES GFR
31
Why does blood pressure have to be regulated so heavily in the kidneys?
High pressures will damage glomerulus capillaries
32
What is the myogenic response in the kidneys?
Intrinsic response of arteriole smotoh muscle to pressure changes. Vasoconstriction in response to increased blood pressure
33
What is tubuloglomerular feedback?
1. Increase in GFR 2. Increased flow through tubules 3. Increased flow of NaCl past macula densa 4. Paracrine signal from macula dense acts on afferent arteriole 5. Afferent arteriole constricts 6. Decrease in renal blood flow 7. Decrease in hydrostatic pressure 8. Decreased GFR
34
What is the juxtaglomerular apparatus?
Area in nephron where ascending loop of Henle/distal tubule, afferent and efferent arterioles are close to one other. Comtains the macula densa and granular cells that help to regulate GFR
35
Autonomic effects on GFR that can override the myogenic response and tubuloglomerular feedback in the kindeys?
Sympathetic innervation of afferent and efferent arterioles that in extreme conditions (severe dehydration and bleeding out) causes a sympathetic vasoconstriction due to a drop in blood pressure, which will decrease GFR
36
Endocrine effects on GFR?
Angiotension II (potent vasoconstrictor) and Prostaglandins (vasodilators). Bothe can also affect the filtration coefficient through actions on podocytes (alter size of slits) and mesengial cells (shapes of glomerular capillaries)
37
Why doesn't the kidney only filter the 1% that is excreted?
Filtration removes foreign/toxic substances in addition to endogenous materials (high rate of filtration quickly clears these substances) and filtering ions and water simplifies their regulation (material reaching distal tubule that is not needed for homeostasis passes into urine)
38
Steps in governing tubular reabsorption?
1. Na+ is reabsorbed by active transport 2. Electrochemical gradient drives anoin reabsorption 3. Water moves by osmosis, following solute reabsorption. Concentrations of other solutes increase as fluid volume in lumen decreases 4. Permeable solutes reabsorbed by diffusion through membrane transporters of by paracellular pathways
39
Paracellular pathway in kidneys?
Molecules through cell-cell junctions
40
Epithelial/trans-cellular transport in kidneys?
Cross of the apical and basolateral membranes of epithelial cells. Mechanism depends on driving force...down gradient = leak channels or facilitated diffusion and against gradient = primary or indirect active transport
41
Steps in active transport of Na+ in proximal tubule?
1. Na+ enters cell through various membrane proteins, moving down its electrochemical gradient 2. Na+ pumped out basolateral side of cell by N+/K+ ATPase
42
Steps in Na+ - Linked Reabsoprtion?
1. Na+ moving down its electrochemical gradient uses SGLT transporter to pull glucose into the cell against its concentration gradient 2. Glucose doffuses out basolateral side of cell using GLUT protein 3. Na+ pumped out by Na+/K+ ATPase
43
How are amino acids, lactate, Krebs cycle intermediates, phsophate, and sulphate reabsrobed?
Apical symporter + basolateral facilitated diffusion carrier or ion exchanger
44
Steps in the passive reabsoprtion of urea?
1. Na+ and other solutes reabsorbed at proximal tubule (via ENaC, Na+/K+ ATPase) 2. Water follows by osmosis 3. Loss of water from tubular fluid results in higher urea concentration in tubule 4. Urea moves passiviely out of tubule through epithelial cells into ECF (paracellular route)
45
What is the renal threshold?
Plasma concentration of a substance at which Tm occurs
46
How is interstitial fluid able to be reabsorbed into the peritubular capillaries?
Lower hydrostatic pressure in the peritubular capillaries results in net reabosprtion of interstitial fluid
47
What is secretion in the kindeys?
Transfer from the extracellular fluid to tubular fluid...very specific and depends on membrane transporters
48
What are the major ions that are secreted for homeostatic regulation?
K+ and H+...endogenous materials and xenobiotics are also secreted
49
Steps in the secretion of organic anions at the proximal tubule?
1. Direct active transport. The Na+/K+ ATPase keeps the concentration of intracellular Na+ low 2. Secondary indirect active transport. NaSC cotransportoer concentrates dicarboxylate inside the cell using energy stored in Na+ concentration gradient 3. Tertiary indirect active transport. Basolateral OAT transporters concentrates organic anions (OA-) inside cell, using energy stored in dicarbodylate gradient
50
What is a naDC?
Na+-dicarboyxylate cotransporters on both the apical and basolateral membranes. Transports dicarboxylates such as citrate, oxaloacetate and alpha ketoglutarate
51
Organic anion transporters?
Able to transport range of anions...endogenous (bile salts) and exogenous (benzoate, salicyclate, and saccharine)
52
Composition of urine versus filtrate?
Glucose, AAs, proteins, and other useful metabolites gone. Waste products much more concentrated (water and ions variable depending on needs)
53
Formula for clearance from the kidney?
Clearance = excretion rate of X (mg/min) / concentration of substance in plasma (mg/mL)
54
What molecules are used as indicators of GFR?
Inulin and creatinine
55
Less of substance in urine than filtered?
Net reabsorption
56
More of substance in urine than was filtered?
Secreted
57
No change in the amount that was filtered and what is in urine?
Only filtration
58
Formula for filtration of a substance?
Concentration of substance in plasma x GFR
59
Opening between bladder and urthera is guarded by what 2 sphincters?
Internal -- smooth muscle (continuation of bladder wall) External -- skeletal muscle (tonic stimulation from CNS keeps it closed most of the time)
60
The simple spinal reflect of micturitoin (urination)?
Bladder fills, activates stretch receptors, afferent information travels to spinal cord and activates 2 sets of neurons, parasympathetic (acts on smooth muscle of bladder) and somatic (inhibits motor neurons to external sphincter)
61
Ions that kidney helps maintain homeostatic levels of?
Na+, Ck-, K+, H+, Ca2+, HPO42-, HCO3- (ECF volume and osmolarity)
62
Can the kidney replace lost water?
NO! Drinking is the only way to replace lost water, and the kidney can only conserve water.
63
Response to decreased blood volume and blood pressure?
Volume receptors in atria and carotid/aortic baroreceptors decrease firing rate. Trigger homeostatic reflix. Cardiovascular system decreases CO and vasoconstricts blood vessels. Increase thirst increases ECF and ICF. Kindeys conserve H2O to minimize further water loss.
64
Response to increased blood volume and blood pressure?
Volume receptors in atria, endocrine cells in atria, and carotid and aortic baroreceptors increase firing rate. Triggers homeostatic reflex. Cardiovascular system decreases CO and causes vasodilation. Kindeys excrete salts and water in urine to decrease ECF and ICF volume, both of which decrease blood pressure.
65
Amount of water gained throughout the day?
2.2 L from food/drink and 0.3 L/day from metabolism (aerobic respiration produces Co2 and H2O)
66
Amount of water lost throughout the day?
Insensible water loss from lungs and skin 0.9 L/day, urine 1.5L, and feces 2.5L
67
Water balance in the body?
0 L
68
Diuresis occurs because?
Need to eliminate excess water = dilute pee = 50 mOsM
69
Extremely concentrated urine occurs when?
Body needs to conserve water (antidiuretics)
70
How does water cross cell membranes?
Leaks through lipid bilayer (happens in most cells but doesn't explain the rapid movement through some cells) and travels through aquaporins
71
Number of aquaporins expressed on apical or basolateral surfaces of epithelial cells in various regions of renal tubules?
6
72
How is dilute urine produced?
Epithelial cells transport solutes but are impermeable to water...reduced expression of aquaporins = less water reabsorbed
73
How is concentrated urine produced?
Epithelial cells and surrounding interstitium are more salty than the tubular fluid, so high osmolarity of medullary interstitium allows urine to become concentrated as it flows through collecting duct
74
Osmolarity changes through a juxtamedullary nephron?
1. Isosmotic fluid leaving proximal tubule becomes progressively more concetrated in descending limb 2. Removal of solutes in thick ascending limb creates hposmotic fluid 3. Permeability to water and solutes in collecting ducts is regulated by hormones 4. Urine osmolarityy depends on reabsoprtion in collecting duct
75
The clearance of a substance X is...
the volume of plasma cleared of X per time
76
If the clearance rate of X is less than the amount filtered, then...
X is being REASORBED by the nephron
77
The renal threshold fro glucose is 300 mg/100 mL plasma. Your cousin, a Type I diabetic, is having trouble regulating her sugar levels. Her plasma glucose is 400 mg/100mL plasma. What would be true regarding glomerular filtration of glucose and excretion of glucose?
It would all be filtered, but not all reabsorbed, so she would excrete glucose in her urine/
78
Effect of vasopressin on collecting duct?
Collecting duct is freely permeable to water, so urine becomes concentrated. Vasopressin is not there, tubule is not permeable to water, causing dilute urine.
79
Steps for aquaporin insertion into apical membrane casued by vasopressin?
1. AVP binds to membrane receptor 2. Receptor activates cyclic AMP 2nd messenger system 3. AQP2 inserted into apical membrane 4. Water absorbed by osmosis into blood
80
What is membrane cycling?
Membrane vesicles containing aquaporin is added to plasma membrane by exocytosis and removed by endocytosis
81
What 2 things trigger release of vasopressin?
Increased plasma osmolarity and decreased blood volume/pressure
82
Why is it so important to regulate ECF osmolarity?
Affect cell size/volume = physical integrity of cells and tissues. Affects ionic strength = activity of macromolecules
83
Why does osmolarity fluctuate?
Variations in water intake/water loss and variations in Na+ intake/Na+ excretion
84
What are the consequences of osmotic perturbations?
Usually neurological. Hyperosmolarity causes seizures and death. Hyposmolarity causes headache/nausea/vomiting, leads to mental confusion, seizures, coma, death
85
Osmoreceptors?
Monitir plasma osmoloarity by increasing firing rate as osmolarity increases
86
Osmoreceptors are stimulated by?
Cell dehydration/shrinking
87
Where are peripheral osmoreceptors located?
Oropharyngeal cavity (back of mouth/throat) and within blood vessels that collect solutes absorbed from intestines.
88
What is the purpose of osmoreceptors?
Can detect osmotic strength of ingested materials and induce anticipatory responses. However, central osmoreceptors are the major points of regulation
89
Central osmoreceptors?
Cicumventricular organs (OVLT and subfornical organ) and supraoptic nucleus in hypothalamus (SON; origin of AVP-secreting neurons)
90
Secretion of AVP from hypothalamus?
1, AVP made and packaged in supraoptic nucleus of hypothalamus 2. Vesicles are transported down the cell 3. Vesicles containing AVP are stored in posterior pituitary 4. AVP is released into blood
91
Decrease in BP on the control of vasopressin secretion?
BP decreased, carotid and aortic baroreceptors decreae firing rate, sensory neuron send AP to hypothalamus, hypothalamic neurons synthesizeAVP
92
Decrease blood volume in the control of vasopressin secretion?
Decreased atrial stretch, sensory neuron to hypothalamus, supraoptic nucleus in hypothalamus makes AVP
93
Increased plasma osmolarity in the control of vasopressin secretion?
Hypothalamic osmoreceptors, interneurons to hypothalamus, supraoptic nuscleus makes AVP
94
Circadian rhythm in adults for AVP?
AVP increases at night so you conserve water and don't have to get up to pee. First pee in the morning is super concentrated!
95
What creates the salt gradient in the renal medulla?
High osmolarity in the medullary interstitium...creates osmotic gradient for reabsoprtion of water
96
Why doesn;t osmolarity of ICF decrease as water is drawn out of tubules?
The anatomical arrangement of Loop of Henle and vasa recta are very close to one another, so it allows for the transfer of water and solutes between the two vessels. This is a COUNTERCURRENT EXCHANGE SYSTEM
97
How does the countercurrenct mutiplier work in the renal medulla?
The ascending limb transports ions, but not water into the interstitium, which causes it to become saltier and the filtrate to become more dilute. More salt moves into the vasa recta. The descending limb transports water but doesn't transport ions, so water flows into vasa recta. This allows the interstitium to remain salty, allowing for concentrated urine to be produced.
98
Steps in ion transport in the thick ascending limb?
1. 1200 mOsm entering ascending loop (hypersosmotic) 2. NKCC symporters on apical membrane reabsorbs salt via secondary active transport (moves Na+, K+, and 2 Cl-) K+ and Cl- leave basolateral side via co-transporters and Na+ leaves basolateral side via Na/K ATPase 3. Water cannot follow solute 4. 100 mOsm leaving ascending loop (hyposmotic)
99
Purpose of Loop of Henle?
1. Pumping of Na+ and K+ in ascending limb is responsible for 25% Na+ and K+ reabsorption 2. Creates a salt gradient for the collecting duct that drive reabsoprtion of water in presence of AVP
100
If kidneys couldn't clear any salt, what would happen to blood pressure?
There would be an increaed water intake (1.1 L), which would increase in ECF volume, which would raise blood pressure/
101
What is responsible for most of the Na excretion?
The kidneys. Loss via feces and sweating minimal under normal conditions (vomiting, diarrhea, and heavy sweating are the exceptions)
102
Is Cl- regulated?
NO. Na+ regulated, Cl- normally follws via electrochemical gradient via NKCC and NaCl symporters
103
Is sweat hyperosmotic or hyposmotic?
Hyposmotic, losing more water than salt
104
Homeostatic response to salt ingestion?
1. Ingest NaCl 2. No change in volume, but increase in osmolarity 3. Vasopressin secreted, increaes renal water reabsorption and kidneys conserve water. 4. Thirst, increase water intake. 5. Increased renal water reabsorption and water intake causes an increase in ECF volume, which raises blood pressure and causes the kidneys to excrete more salt and water (slow response), which returns osmolarity to normal levels. 6. Increased blood pressure causes cardiovascular response to reflexively lower BP, volume and blood pressure to normal
105
Where is the only place Na+ reabsoprtion regulated?
The distal nephron. Unregulated in proximal tubule (always permeable to water) and ascending loop
106
Where is aldosterone synthesized?
Synthesized on demand in adrenal cortex and sent into bloodstream bound to carriers
107
Effects of aldosterone?
Rapid effects = modulation and existing pumps/channels Slow effects - drives transcription of genes with upstream aldosterone response elements, causing synthesis of new proteins and insertion of new pumps/channels
108
Target of aldosterone?
Principal cells (P cells) within epithelium of distal nephron
109
Steps in aldosterone response on P cells within epithelium of distal nephron?
1. Aldosterone binds to cytoplasmic receptor 2. Hormone-receptor complex initiates transcription in the nucleus 3. Translation and protein synthesis makes new protein channels and pumps 4. Aldosterone-induced protens modulate existing channels and pumps 5. Result is increased Na+ reabsoprtion and K+ secretion
110
Stimulus for aldosterone secretion?
Increased plasma [K+] monitored by cells in the adrenal cortex (protects against hyperkalemia) 2. Decrease in BP
111
Primary action of aldosterone?
Na+ reabsorption and K+ secretion by increasing expression of channels (ENaC, ROMK), pumps (Na+/K+ ATPase)
112
Renin-Angiotensin System (RAS)?
1. Angiotensinogen made in liver, circulates in plasma as an inactive precursor 2. Renin, secreted from granular cells in JGA of nephron, cleave angiotensinogen into angiotensis I 3. ACE (in endothelium of blood vessels) turns angiotensin I into angiotensin II 4. Ag II acts on adrenal cortex to synthesize aldosterone 5. Aldosterone works on principal cells in distal nephron
113
Cells that make renin?
Granular cells (JG cells)
114
What activates the RAS?
Low blood pressure and renin from kidney initiates pathway
115
How do granular cells of juxtaglomerular apparatus know when to release renin?
1. Granular cells themselves monitor blood pressure in afferent arteriole, release renin i n response to decreased BP 2. Sympathetic neurons from cardio control centre in medulla terminate on JG cells, part of the baroreceptor response to dec. BP 3. Paracrine feedback from macula densa cells in distal tubule, decreased flow rate, leads to increased renin release (and vice versa)
116
Thirst can be stimulated by what 2 things?
Osmoreceptors shrinking and Ang II acting centrally on hypthalamus
117
KNOW HOMEOSTATIC RESPONSE TO DROP IN BP!!!
How ANG II affects arterioles, cardio control centre, hypothalamus, adreno-cortex
118
How is hypertension treated through the RAS?
Blocking Ang II...ACE inhibitors (cannot make Ang II), angiotensin receptor blockers, and direct renin inhibitors (no Ang I)
119
What is atrial natriuretic peptide?
A peptide hormone that is produced/released from specialized mycoardial cells mostly in the atria that is released when these atrial cells stretch more than normal. Acts to oppose RAS
120
Mechanism of natriuretic peptide?
1. Acts on hypothalamus to decrease AVP 2. Acts on kidney to decrease Na+ reabsorption, increase GFR, and decrease renin, which increase Na+ and H2O secretion 3. Acts on adrenal cortex to decrease aldosterone 4. Acts on CCC to decrease sympathetic output
121
Main effect of natriuretic peptide?
Lowers BP
122
Why is the ECF concentration of K+ maintained in a narrow range, even though only 2% is found in the ECF?
It is a major determinant of resting membrane potential/excitability of excitable cells.
123
Hyperkalemia leads to what is regards to cell excitability?
Reduced concentration gradient, so K+ stays in cells = cell depolarizes
124
Hypokalemia leads to what changes in regards to cell excitability?
Greater concentration gradient, more K+ leaves cell = cell hyperpolarized (muscle weakness)
125
How is Na+ replaced?
Low Na+ triggers salt appetite, linked to ANG II and aldosterone (Na+ balance)
126
How is water replaced?
Thirst -- controlled by centres in hypothalamus, respond to hyperosomolarity and ANG II
127
Although dehydration and hemorrhaging both involve a low volume alarm, how does the response to dehydration differ from hemorrhaging?
Dehydration involves loss of more water than solute, so there is also a hyperosmolarity alarm (do NOT need renin and aldosterone). Hemorrhage involves equal loss of water and salt, so no hyperosmolarity alarm.
128
Normal plasma pH?
7.38-7.42
129
Why is H+ concentration heavily regulated?
Affects tertiary structure of proteins, which is related to enzyme function. Abnormal pH affects the nervous system (acidosis = CNS depression and alkalosis = hyperexcitability/twitch). pH disturbances are also assocaited with K+ disturbances (partly due to renal transporter, H/K+-ATPase)
130
Where does the H+ input come from in the body?
Fatty acids, amino acids, metabolism, lactic acid, ketoacids
131
What are some of the buffers in the body?
HCO3- in ECF, proteins/hemoglobin/phosphates in cells, phosphates/ammonia in urine
132
Where does the H+ output come from in the body?
Ventilation and Renal H+ output
133
What is the primary source of H+ in the cell?
The CO2 produced during aerobic respiration is the main source of acid in the body. CO2+H2)H2CO3HCO3+H+
134
What is carbonic anhydrase?
Enzyme that catalyzes the reaction between CO2+H2) and HCO3- + H+
135
What is the first line of defence in pH homeostasis?
Buffers...combine with or release H+
136
2nd line of defence in pH homeostasis?
Ventilation...corrects 75% of disturbances and very rapid. Also can cause disturbances.
137
3rd line of defence in pH homeostasis?
Renal regualtion...slower, but highly effective. Receptor-mediated endocytosis, directly by excreting or reabsorbing H+ and indirectly by changing in the rate at which HCO3- buffer is reabsorbed or secreted
138
Hypoventilation effect on pH homeostasis?
Acidosis, reaction shift right
139
Hyperventilation effect on pH homeostasis?
Alkalosis, reaction shifts left
140
Respiratory compensation for acidosis?
Inc. in plasma pH works on carotid/aortic chemoreceptors and Inc. plasma CO2 works on central chemoreceptors --> both act on respiratory control centres --> inc. AP in somatic MN --> muscle of ventilation --> inc. rate and depth of breathing --> dec. plasma CO2 and dec. plasma H+
141
Transporters on the APICAL membrane that secrete H+ into urine?
1. Na+/H+ exchanger 2. H+ ATPase 3. H+ - K+ ATPase 4. Na-NH4 antiport
142
BASOLATERAL pump used to move bicarb back into plasma?
Na+ HCO3- symport. Moves Na+ and HCO3- out of epithelial cell into intersitium
143
Where does bicarb reabsorption happen?
Proximal tubule
144
How is bicarb reabsorption achieved in proximal tubule?
NO transporters on apical membrane, so indirect method used: filtered HCO3- --CA--> CO2 --CA in epithelial cell--> bicarb --basolateral pump--> interstitium
145
Fine-tuning of acid-base balance carried out where?
In the INTERCALATED CELLS in the DISTAL NEPHRON (interspersed with P cells)
146
Type A intercalated cells?
Secrete H+ and reabsorb bicarb to deal with acidosis
147
Type B intercalated cells?
Secrete bicarb and reabsorb H+ to deal with alkalosis
148
H+ / K+ ATPase is found on what membrane in Type A intercalated cells?
Apical
149
H+ / K+ ATPase is found on what membrane in Type B intercalated cells?
Basolateral
150
Primary causes of metabolic acidosis?
Increased acidity or loss of HCO3-
151
Primary cause of metabolic alkalosis?
Decreased acidity due to loss of H+
152
If primary cause of acid-base disturbance is respiratory, what mechanism corrects it?
Renal
153
If primary cause of acid-base disturbance is metabolic, what mechanism corrects it?
Respiratory and renal
154
Causes of respiratory acidosis?
Alveolar hypoventilation from respiratory depressions, asthma, fibrosis, severe pneumonia, and other diseases affecting breathing
155
Causes for metabolic acidosis?
Lactic acidosis/anaerobic metabolism, ketoacidosis (excessive breakdown of fats or certain AAs in type I diabetics and low carb diets), ingestion of certain toxins OR loss of bicarb from diarrhea
156
Causes of respiratory alkalosis?
Hyperventilation...excessive artifical ventilation or anxiety-drive hyperventilation
157
Causes of metabolic alkalosis?
Loss of H+ from stomach (excessive vomiting) and ingestion of excessive bicarb-based antacids
158
The ascending Loop of Henle is permeable to water...
NEVER...AVP works only on collecting duct
159
What is responsible for the formation of salt gradient in renal medulla?
Ascending limb must transport ions from tubule to interstitium
160
Inhibition of the NKCC transporter on the apical membrane of the ascending limb would result in?
Inhibit Na and Cl reabsoprtion, disruption of salt gradient, and increased urine production ----> loop diuretics
161
Responses to increased amount of salt?
Increased AVP and thirst
162
What are the stimuli for aldosterone secretion?
Hyperkalemia and decreased BP
163
Digestion?
Chemical and mechanical breakdown of foods into smaller units that can be taken up across the intestinal epithelium into the body
164
Absorption?
Active or passive transfer of substances from the lumen of the GI tract to the ECF
165
Motility?
Movement of material in the GI tract as a result of muscle contraction
166
Secretion in the GI?
Refers to both the transepithelial transfer of H2O and ions from the ECF to the digestive tract lumen and the release of substances synthesized by GI epithelial cells
167
Parts of the stomach?
Upper fundus, central body, lower antrum, and the pylorus (gatekeeps between the sotmach and the small intestine)
168
Most digestion occurs where?
small intestine
169
Parts of the small intestine?
Duadenum, jejunum, and ileum
170
Parts of large intestine?
Colon and rectum
171
4 layers of GI tract?
1. inner mucosa layer facing the lumen 2. Submucosa 3. Muscularis externa/smooth muscle 4. Covering of connective tissue called the serosa
172
3 layers of the mucosa?
1. Single layer of epithelial cells 2. lamina propria, subepithelial connective tissue that holds the epithelium in place 3. Muscularis mucosae, a thin layer of smooth muscle
173
Villi in the stomach are called?
Gastric glands
174
Villi in the stomach are called?
Crypts
175
Submucosa contains?
Connective tissues with larger blood and lymph vessels. Also contains the submucosal plexus, one of the 2 major networks of the enteric nervous system
176
2 parts and purpose of enteric nervous system?
Submuscal plexus and myenteric plexus, helps to coordinate digestive function
177
Purpose of submucosal plexus?
Innervates cells in the epithelial layer as well as smooth muscle of the muscularis mucosae (aka Meissner's plexus?
178
Purpose of myenteric plexus?
Controls and coordinates the motor activty of the muscularis externa
179
What does the muscularis externa primarily consist of ?
An inner circular layer of muscle (decreaess diameter of lumen) and an outer longitudinal layer (shortens the tube) Also an incomplete oblique muscle between the circular muscles and the submucosa
180
What is peristalsis?
Moving of food from mouth to anus
180
What is peristalsis?
Moving of food from mouth to anus
181
What are the 2 major patterns of contractions in the gut?
Peristalsis and Segmental contractions
181
What are the 2 major patterns of contractions in the gut?
Peristalsis and Segmental contractions
182
What do segmental contractions do?
Mix/churn...maximizes exposure to digestive enzymes and epithelial
182
What do segmental contractions do?
Mix/churn...maximizes exposure to digestive enzymes and epithelial
183
What type o muscle is the majority of gut muscle?
Smooth muscle connected by gap junctions
183
What type o muscle is the majority of gut muscle?
Smooth muscle connected by gap junctions
184
What parts of the gut are tonically contracted (minutes to hours)?
Smooth muscle sphincters and the anterior part of the stomach (keeps food from moving backward)
184
What parts of the gut are tonically contracted (minutes to hours)?
Smooth muscle sphincters and the anterior part of the stomach (keeps food from moving backward)
185
What parts of the gut undergo phasic contractions (few seconds)?
Posterior part of the stomach and small intestine
185
What parts of the gut undergo phasic contractions (few seconds)?
Posterior part of the stomach and small intestine
186
What are migrating motor complexes?
Contractions that slowly sweep down stomach to large intestine (every 90 minutes) from the stomach to the large intestine
186
What are migrating motor complexes?
Contractions that slowly sweep down stomach to large intestine (every 90 minutes) from the stomach to the large intestine
187
What type of contractions occur during and after a meal?
Peristalic and segmental contractions
187
What type of contractions occur during and after a meal?
Peristalic and segmental contractions
188
What are slow wave potentials?
Potentials that fire at a very slow rate and don't reach threshold with each cycle. When threshold is reached, voltage gated Ca2+ channels in the muscle fibre open, Ca2+ enters, and the cell fires one or more action potentials.
188
What are slow wave potentials?
Potentials that fire at a very slow rate and don't reach threshold with each cycle. When threshold is reached, voltage gated Ca2+ channels in the muscle fibre open, Ca2+ enters, and the cell fires one or more action potentials.
189
How is the degree of contraction in gut smooth muscle graded?
Longer wave = longer time for Ca2+ to enter = larger contraction.
189
How is the degree of contraction in gut smooth muscle graded?
Longer wave = longer time for Ca2+ to enter = larger contraction.
190
What influences the amplitude and duration of contraction in gut smooth muscle?
Neurotransmitters (autonomic input), hormones, and paracrine factors
190
What influences the amplitude and duration of contraction in gut smooth muscle?
Neurotransmitters (autonomic input), hormones, and paracrine factors
191
Where are slow waves the most frequent in the GI tract?
More frequent in the duodenum
191
Where are slow waves the most frequent in the GI tract?
More frequent in the duodenum
192
What sets the slow wave frequency in the GI tract smooth muscle?
Interstitial cells between layers of smooth muscle..."interstitial cells of Cajal"
192
What sets the slow wave frequency in the GI tract smooth muscle?
Interstitial cells between layers of smooth muscle..."interstitial cells of Cajal"
193
What is secreted in the GI tract?
Water and ions (secreted into lumen, then reabsorbed). Enzymes. Mucus. Salivia. Bile (from liver).
193
What is secreted in the GI tract?
Water and ions (secreted into lumen, then reabsorbed). Enzymes. Mucus. Salivia. Bile (from liver).
194
Transporters for the secretion of ions in the GI tract?
Na+/K+ ATPase, NKCC co-transporter, Cl-/HCO3- exchanger, NA+/H+ exchanger, and H+/K+ ATPase
194
Transporters for the secretion of ions in the GI tract?
Na+/K+ ATPase, NKCC co-transporter, Cl-/HCO3- exchanger, NA+/H+ exchanger, and H+/K+ ATPase
195
Ion channels for the secretion of water and ions in the GI tract?
ENaC, K+ channels, Cl- channels (including CFTR channel)
195
Ion channels for the secretion of water and ions in the GI tract?
ENaC, K+ channels, Cl- channels (including CFTR channel)
196
What is the pH in the lumen of the stomach?
As low as 1
196
What is the pH in the lumen of the stomach?
As low as 1
197
Acid secretion in parietal cells of stomach?
H+ is secreted from apical side via the H+/K+ ATPase and bicarb (from CO2 and OH-) is reabsorbed into the blood via the HCO3-/Cl- transporter. Cl- is transported into the stomach lumen, too.
197
Acid secretion in parietal cells of stomach?
H+ is secreted from apical side via the H+/K+ ATPase and bicarb (from CO2 and OH-) is reabsorbed into the blood via the HCO3-/Cl- transporter. Cl- is transported into the stomach lumen, too.
198
What is the alkaline tide?
The reabsorbtion of HCO3- into the blood in exchange for Cl- being abosorbed into parietal cell and H+ being secreted into lumen.
198
What is the alkaline tide?
The reabsorbtion of HCO3- into the blood in exchange for Cl- being abosorbed into parietal cell and H+ being secreted into lumen.
199
Bicarb from pancreas is released into?
Dueodenum to neutralize acid arriving from the stomach
199
Bicarb from pancreas is released into?
Dueodenum to neutralize acid arriving from the stomach
200
What do acinar cells do?
Secrete enzymes from pancreas into duodenum/small intestine
200
What do acinar cells do?
Secrete enzymes from pancreas into duodenum/small intestine
201
What do duct cells do in the pancreas?
Secrete bicarb solution
201
What do duct cells do in the pancreas?
Secrete bicarb solution
202
Bicarb secretion in pancreatic duct cell or duodenal cell?
Bicarb secreted via apical Cl-/HCO3- exchanger. Cl- enters via basolateral NKCC transporter and leaves via apical CFTR channel. Luminal Cl- the nreenters cell via Cl-/HCO3- exchanger
202
Bicarb secretion in pancreatic duct cell or duodenal cell?
Bicarb secreted via apical Cl-/HCO3- exchanger. Cl- enters via basolateral NKCC transporter and leaves via apical CFTR channel. Luminal Cl- the nreenters cell via Cl-/HCO3- exchanger
203
What does bicarb secretion in pancreatic duct cells and duodenal cells require?
A high expression of carbonic anhydrase (like kidney and RBCs)
203
What does bicarb secretion in pancreatic duct cells and duodenal cells require?
A high expression of carbonic anhydrase (like kidney and RBCs)
204
NaCl secretion in the small intestice, colon, and salivary glands?
1. Na+, K+, 2 Cl= enter via NKCC transporters 2. Cl- enters lumen through CFTR channel 3. Na+ is reabsorbed 4. Negative Cl- in lumen attracts Na+ by paracellular pathway. Water follows.
204
NaCl secretion in the small intestice, colon, and salivary glands?
1. Na+, K+, 2 Cl= enter via NKCC transporters 2. Cl- enters lumen through CFTR channel 3. Na+ is reabsorbed 4. Negative Cl- in lumen attracts Na+ by paracellular pathway. Water follows.
205
What does the ion secretion into lumen of pancreas or small intestine do?
Causes an osmotic drive that allows for the formation of a watery environment
205
What does the ion secretion into lumen of pancreas or small intestine do?
Causes an osmotic drive that allows for the formation of a watery environment
206
How is the gut lubrciated?
Crypt cells in small intestine and colon secrete iostonic saline solution that mixes with mucus secreted by goblet cells to lubricate gut contents
206
How is the gut lubrciated?
Crypt cells in small intestine and colon secrete iostonic saline solution that mixes with mucus secreted by goblet cells to lubricate gut contents
207
What are the pancreatic effects of cystic fibrosis?
Mutation in gene that codes for CFTR channel --> Cl- not transported into ducts ---> various effects including dec. Na+ and water transport into ducts ---> mucus still produced by goblet cells but greatly thickened due to lack of water ---> blockage of pancreatic ducts ---> exocrine secretions of pancreas not released (bicarb, enzymes) ---> back pressure/inflammation ---> damage to pancreas
207
What are the pancreatic effects of cystic fibrosis?
Mutation in gene that codes for CFTR channel --> Cl- not transported into ducts ---> various effects including dec. Na+ and water transport into ducts ---> mucus still produced by goblet cells but greatly thickened due to lack of water ---> blockage of pancreatic ducts ---> exocrine secretions of pancreas not released (bicarb, enzymes) ---> back pressure/inflammation ---> damage to pancreas
208
What are responsible for the secretion of enzymes in GI tract?
Either exocrine glands (pancreas, salivary) or epithelial cells of stomach and small intestine
208
What are responsible for the secretion of enzymes in GI tract?
Either exocrine glands (pancreas, salivary) or epithelial cells of stomach and small intestine
209
What regulated secretion of enzymes in GI tract?
Neural, hormonal, or paracrine signals. Usually parasympathetic stimulation (via vagus) stimulates enzyme secretion.
209
What regulated secretion of enzymes in GI tract?
Neural, hormonal, or paracrine signals. Usually parasympathetic stimulation (via vagus) stimulates enzyme secretion.
210
What does mucus primarily consist of?
Primarily of "mucins" -- a mixture of glycoproteins
210
What does mucus primarily consist of?
Primarily of "mucins" -- a mixture of glycoproteins
211
What cells produce mucus in GI tract?
Serous cells in salivary glands, mucous cells in stomach, and goblet cells in intestine
211
What cells produce mucus in GI tract?
Serous cells in salivary glands, mucous cells in stomach, and goblet cells in intestine
212
Signals for secretion of mucus?
Parasympathetic stimulation, various neuropeptides of enteric system, and cytokines (from immune cells...infection and inflammation increase mucus secretion)
212
Signals for secretion of mucus?
Parasympathetic stimulation, various neuropeptides of enteric system, and cytokines (from immune cells...infection and inflammation increase mucus secretion)
213
2 steps in secretion of saliva?
1. Fluid secreted by acinar cells similar to ECF (isotonic saline) 2. As it passes through ducts, epithelial cells take back Na+ and secrete K+, so that it eventually resembles intracellular fluid (duct cells have low H2O permeability, so water remains in saliva = hypo-osmotic)
213
2 steps in secretion of saliva?
1. Fluid secreted by acinar cells similar to ECF (isotonic saline) 2. As it passes through ducts, epithelial cells take back Na+ and secrete K+, so that it eventually resembles intracellular fluid (duct cells have low H2O permeability, so water remains in saliva = hypo-osmotic)
214
Signals fro saliva secretion?
Stimulation from parasympathetic nervous system. Inhibited by sympthatetic.
214
Signals fro saliva secretion?
Stimulation from parasympathetic nervous system. Inhibited by sympthatetic.
215
What is the largest internal organ in the body?
LIVER
215
What is the largest internal organ in the body?
LIVER
216
Where does the blood flow to the liver come from?
Oxygenated blood from hepatic artery and the hepatic portal vein (rich in nutrients from the GI tract and hemoglobin breakdown products from the spleen)
216
Where does the blood flow to the liver come from?
Oxygenated blood from hepatic artery and the hepatic portal vein (rich in nutrients from the GI tract and hemoglobin breakdown products from the spleen)
217
How does blood leave the liver?
Hepatic vein
217
How does blood leave the liver?
Hepatic vein
218
Bile synthesized in the liver is secreted into what for storage?
Secreted into the common hepatic duct for storage in the gall bladder
218
Bile synthesized in the liver is secreted into what for storage?
Secreted into the common hepatic duct for storage in the gall bladder
219
How is bile secreted into the lumen of the intestine?
Through the common bile duct
219
How is bile secreted into the lumen of the intestine?
Through the common bile duct
220
What are the hepatocytes of the liver organized into?
Hexagonal units called lobules
220
What are the hepatocytes of the liver organized into?
Hexagonal units called lobules
221
Pathway of bile in liver?
Hepatoctyes ---> bile canaliculi ---> bile ductules ---> common hepatic duct to gall bladder ---> common bile duct ---> sphincter of Oddi ---> duodenum
221
Pathway of bile in liver?
Hepatoctyes ---> bile canaliculi ---> bile ductules ---> common hepatic duct to gall bladder ---> common bile duct ---> sphincter of Oddi ---> duodenum
222
Percent breakdown of blood flow in lobule?
25% from hepatic artery (oxygenated) and 75% from hepatic portal vein (GI tract and spleen)
222
Percent breakdown of blood flow in lobule?
25% from hepatic artery (oxygenated) and 75% from hepatic portal vein (GI tract and spleen)
223
Blood flow through lobule?
Hepatic artivery or Hepatic Portal Vein ---> sinusoids (very gappy, lots of plasms filtered out to lymph, lots of proteins added in) ---? centralvein ---> hepatic vein
223
Blood flow through lobule?
Hepatic artivery or Hepatic Portal Vein ---> sinusoids (very gappy, lots of plasms filtered out to lymph, lots of proteins added in) ---? centralvein ---> hepatic vein
224
Key components of bile?
Bile salts (facilitae fat digestion), Bile pigments (bilirubin from hemoglobin breakdown)
224
Key components of bile?
Bile salts (facilitae fat digestion), Bile pigments (bilirubin from hemoglobin breakdown)
225
What is absorbed from the GI tract in the liver?
Bilirubin, nutrients, drugs, foreign substances
225
What is absorbed from the GI tract in the liver?
Bilirubin, nutrients, drugs, foreign substances
226
What is secreted into duodenum from the liver?
Bile salts, bilirubin, water, ions, and phospholipids
226
What is secreted into duodenum from the liver?
Bile salts, bilirubin, water, ions, and phospholipids
227
Metabolites to peripheral tissues via the hepatic vein from the liver?
Glucose, plasma proteins, urea, vitamin D, somatomedins, metabolites for excretion
227
Metabolites to peripheral tissues via the hepatic vein from the liver?
Glucose, plasma proteins, urea, vitamin D, somatomedins, metabolites for excretion
228
What metabolites are brought to the liver via the hepatic artery?
Bilirubin, hormone and drug metabolites, and nutrients
228
What metabolites are brought to the liver via the hepatic artery?
Bilirubin, hormone and drug metabolites, and nutrients
229
What is peristalsis?
Moving of food from mouth to anus
230
What are the 2 major patterns of contractions in the gut?
Peristalsis and Segmental contractions
231
What do segmental contractions do?
Mix/churn...maximizes exposure to digestive enzymes and epithelial
232
What type o muscle is the majority of gut muscle?
Smooth muscle connected by gap junctions
233
What parts of the gut are tonically contracted (minutes to hours)?
Smooth muscle sphincters and the anterior part of the stomach (keeps food from moving backward)
234
What parts of the gut undergo phasic contractions (few seconds)?
Posterior part of the stomach and small intestine
235
What are migrating motor complexes?
Contractions that slowly sweep down stomach to large intestine (every 90 minutes) from the stomach to the large intestine
236
What type of contractions occur during and after a meal?
Peristalic and segmental contractions
237
What are slow wave potentials?
Potentials that fire at a very slow rate and don't reach threshold with each cycle. When threshold is reached, voltage gated Ca2+ channels in the muscle fibre open, Ca2+ enters, and the cell fires one or more action potentials.
238
How is the degree of contraction in gut smooth muscle graded?
Longer wave = longer time for Ca2+ to enter = larger contraction.
239
What influences the amplitude and duration of contraction in gut smooth muscle?
Neurotransmitters (autonomic input), hormones, and paracrine factors
240
Where are slow waves the most frequent in the GI tract?
More frequent in the duodenum
241
What sets the slow wave frequency in the GI tract smooth muscle?
Interstitial cells between layers of smooth muscle..."interstitial cells of Cajal"
242
What is secreted in the GI tract?
Water and ions (secreted into lumen, then reabsorbed). Enzymes. Mucus. Salivia. Bile (from liver).
243
Transporters for the secretion of ions in the GI tract?
Na+/K+ ATPase, NKCC co-transporter, Cl-/HCO3- exchanger, NA+/H+ exchanger, and H+/K+ ATPase
244
Ion channels for the secretion of water and ions in the GI tract?
ENaC, K+ channels, Cl- channels (including CFTR channel)
245
What is the pH in the lumen of the stomach?
As low as 1
246
Acid secretion in parietal cells of stomach?
H+ is secreted from apical side via the H+/K+ ATPase and bicarb (from CO2 and OH-) is reabsorbed into the blood via the HCO3-/Cl- transporter. Cl- is transported into the stomach lumen, too.
247
What is the alkaline tide?
The reabsorbtion of HCO3- into the blood in exchange for Cl- being abosorbed into parietal cell and H+ being secreted into lumen.
248
Bicarb from pancreas is released into?
Dueodenum to neutralize acid arriving from the stomach
249
What do acinar cells do?
Secrete enzymes from pancreas into duodenum/small intestine
250
What do duct cells do in the pancreas?
Secrete bicarb solution
251
Bicarb secretion in pancreatic duct cell or duodenal cell?
Bicarb secreted via apical Cl-/HCO3- exchanger. Cl- enters via basolateral NKCC transporter and leaves via apical CFTR channel. Luminal Cl- the nreenters cell via Cl-/HCO3- exchanger
252
What does bicarb secretion in pancreatic duct cells and duodenal cells require?
A high expression of carbonic anhydrase (like kidney and RBCs)
253
NaCl secretion in the small intestice, colon, and salivary glands?
1. Na+, K+, 2 Cl= enter via NKCC transporters 2. Cl- enters lumen through CFTR channel 3. Na+ is reabsorbed 4. Negative Cl- in lumen attracts Na+ by paracellular pathway. Water follows.
254
What does the ion secretion into lumen of pancreas or small intestine do?
Causes an osmotic drive that allows for the formation of a watery environment
255
How is the gut lubrciated?
Crypt cells in small intestine and colon secrete iostonic saline solution that mixes with mucus secreted by goblet cells to lubricate gut contents
256
What are the pancreatic effects of cystic fibrosis?
Mutation in gene that codes for CFTR channel --> Cl- not transported into ducts ---> various effects including dec. Na+ and water transport into ducts ---> mucus still produced by goblet cells but greatly thickened due to lack of water ---> blockage of pancreatic ducts ---> exocrine secretions of pancreas not released (bicarb, enzymes) ---> back pressure/inflammation ---> damage to pancreas
257
What are responsible for the secretion of enzymes in GI tract?
Either exocrine glands (pancreas, salivary) or epithelial cells of stomach and small intestine
258
What regulated secretion of enzymes in GI tract?
Neural, hormonal, or paracrine signals. Usually parasympathetic stimulation (via vagus) stimulates enzyme secretion.
259
What does mucus primarily consist of?
Primarily of "mucins" -- a mixture of glycoproteins
260
What cells produce mucus in GI tract?
Serous cells in salivary glands, mucous cells in stomach, and goblet cells in intestine
261
Signals for secretion of mucus?
Parasympathetic stimulation, various neuropeptides of enteric system, and cytokines (from immune cells...infection and inflammation increase mucus secretion)
262
2 steps in secretion of saliva?
1. Fluid secreted by acinar cells similar to ECF (isotonic saline) 2. As it passes through ducts, epithelial cells take back Na+ and secrete K+, so that it eventually resembles intracellular fluid (duct cells have low H2O permeability, so water remains in saliva = hypo-osmotic)
263
Signals fro saliva secretion?
Stimulation from parasympathetic nervous system. Inhibited by sympthatetic.
264
What is the largest internal organ in the body?
LIVER
265
Where does the blood flow to the liver come from?
Oxygenated blood from hepatic artery and the hepatic portal vein (rich in nutrients from the GI tract and hemoglobin breakdown products from the spleen)
266
How does blood leave the liver?
Hepatic vein
267
Bile synthesized in the liver is secreted into what for storage?
Secreted into the common hepatic duct for storage in the gall bladder
268
How is bile secreted into the lumen of the intestine?
Through the common bile duct
269
What are the hepatocytes of the liver organized into?
Hexagonal units called lobules
270
Pathway of bile in liver?
Hepatoctyes ---> bile canaliculi ---> bile ductules ---> common hepatic duct to gall bladder ---> common bile duct ---> sphincter of Oddi ---> duodenum
271
Percent breakdown of blood flow in lobule?
25% from hepatic artery (oxygenated) and 75% from hepatic portal vein (GI tract and spleen)
272
Blood flow through lobule?
Hepatic artivery or Hepatic Portal Vein ---> sinusoids (very gappy, lots of plasms filtered out to lymph, lots of proteins added in) ---? centralvein ---> hepatic vein
273
Key components of bile?
Bile salts (facilitae fat digestion), Bile pigments (bilirubin from hemoglobin breakdown)
274
What is absorbed from the GI tract in the liver?
Bilirubin, nutrients, drugs, foreign substances
275
What is secreted into duodenum from the liver?
Bile salts, bilirubin, water, ions, and phospholipids
276
Metabolites to peripheral tissues via the hepatic vein from the liver?
Glucose, plasma proteins, urea, vitamin D, somatomedins, metabolites for excretion
277
What metabolites are brought to the liver via the hepatic artery?
Bilirubin, hormone and drug metabolites, and nutrients
