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A&P 2 lecture > Chapter 11: Water & Electrolyte Balance > Flashcards

Chapter 11: Water & Electrolyte Balance Flashcards

1
Q

What is the process of urine formation and what does glomerular filtrate contain?

A

Urine formation involves filtration, where glomerular filtrate (similar to plasma) is produced. It contains glucose, amino acids, albumins (100% reabsorbed), sodium ions, potassium, chloride, calcium, magnesium, bicarbonate, phosphate, urea, creatinine, and creatine. Creatinine is filtered but not reabsorbed.

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2
Q

What regulates sodium reabsorption and calcium/magnesium reabsorption in the kidneys?

A

Sodium reabsorption is regulated by Aldosterone, while calcium/magnesium reabsorption is regulated by Parathyroid Hormone (PTH).

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3
Q

What happens when ADH is present or absent?

A

With ADH: Urine volume is small and concentrated.

Without ADH: Urine volume is large and dilute, leading to diuresis, which can result in diabetes insipidus.

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4
Q

What is the net filtration pressure (NFP) and how is it calculated?

A

NFP is the pressure that determines filtration in the glomerulus. It is calculated as:

NFP = BP - (OP + Hydrostatic Pressure)

NFP = 60 mmHg - (32 mmHg + 18 mmHg) = +10 mmHg, which allows filtration.

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5
Q

How much filtrate is reabsorbed and where does it occur?

A

99% of filtrate is reabsorbed, mostly in the proximal convoluted tubule (PCT) and throughout the nephron, with obligatory water reabsorption occurring due to osmotic gradients.

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6
Q

Describe the filtrate flow through the nephron.

A

PCT (Proximal Convoluted Tubule): 100% volume, isotonic, obligatory water reabsorption.

Descending Limb of Loop of Henle: Water leaves, filtrate becomes hypertonic (5% volume).

Ascending Limb of Loop of Henle: Sodium leaves, water stays, filtrate becomes hypotonic (4.5% volume).

DCT (Distal Convoluted Tubule): Sodium and water reabsorbed under aldosterone (isotonic).

Collecting Duct: Water reabsorbed under ADH, filtrate becomes concentrated, leaving as urine (0.5% remaining, hypertonic).

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7
Q

What is the function of the juxtaglomerular apparatus (JGA)?

A

The JGA, where the DCT contacts the afferent arteriole, detects sodium concentration in the filtrate. Juxtaglomerular cells release renin, which helps produce Angiotensin II to regulate blood pressure.

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8
Q

What is the difference between obligatory and facultative water reabsorption?

A

Obligatory water reabsorption: Occurs due to osmotic gradients, primarily in the PCT.

Facultative water reabsorption: Controlled by ADH, occurs in the collecting duct based on hydration levels.

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9
Q

What is osmotic diuresis, and what causes it?

A

Osmotic diuresis is excessive water loss due to impaired osmotic gradient, preventing proper water reabsorption.

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10
Q

What causes hormonal diuresis?

A

Hormonal diuresis occurs when there is no ADH, leading to large volumes of dilute urine being produced.

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11
Q

What transport mechanism is used for glucose reabsorption in the PCT?

A

Secondary active transport using SGLT (Sodium-Glucose Cotransporter).

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12
Q

What does the Na+/K+ ATPase pump do in the PCT?

A

Pumps Na⁺ out of the cell and K⁺ in, using primary active transport (requires ATP).

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13
Q

What type of transport is used for water reabsorption in the PCT?

A

Osmosis via AQP I (Aquaporin I - Water Channel).

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14
Q

What happens with potassium in the PCT?

A

ROMK (Renal Outer Medullary Potassium Channel) secretes K⁺ into the filtrate via facilitated diffusion.

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15
Q

What is the role of the Na⁺/Amino Acid Cotransporter in the PCT?

A

Transports Na⁺ and amino acids into the cell via secondary active transport.

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16
Q

What is reabsorbed 100% in the PCT?

A

Glucose and amino acids are 100% reabsorbed in the PCT.

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17
Q

How is albumin reabsorbed in the PCT?

A

Through pinocytosis (a form of endocytosis).

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18
Q

What is the role of GLUT2 (Glucose Transporter) on the basolateral side of the PCT?

A

GLUT2 moves glucose from the cell into the blood via facilitated diffusion.

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19
Q

What type of transport does the urea transporter use in the PCT?

A

Facilitated diffusion.

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20
Q

What ions pass through the paracellular pathway in the PCT?

A

Ca²⁺, Mg²⁺, Cl⁻ via passive diffusion.

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21
Q

What are principal cells in the DCT responsible for?

A

They are hormone-sensitive cells involved in sodium and water reabsorption.

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22
Q

What is the role of ENaC (Epithelial Sodium Channels) in the DCT?

A

They allow Na⁺ to enter the cell from the filtrate. Aldosterone stimulates their insertion, increasing sodium reabsorption.

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23
Q

How does water move in the DCT?

A

Water follows sodium into the cell via osmosis, depending on water channel availability and osmotic gradient.

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24
Q

What does the Na+/K+ ATPase pump do in the DCT?

A

It pumps Na⁺ out of the cell into the bloodstream and K⁺ into the cell, maintaining a low intracellular sodium concentration.

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25
Q: What happens in the collecting tubule under the influence of ADH?
Water reabsorption occurs under ADH (Antidiuretic Hormone), which increases the reabsorption of water.
26
What happens when there is no ADH present?
Diuresis occurs, resulting in large volume of dilute urine, as seen in Diabetes Insipidus.
27
How does water move in the collecting tubule?
Water moves through AQP II on the apical side into the cell, and then exits through AQP III on the basolateral side.
28
What is the osmolarity range of urine in the collecting tubule with water reabsorption?
Osmolarity starts at 300 mOsm and can reach 1200 mOsm after reabsorption.
29
What is tubular secretion?
It’s the process where substances are added from the blood into the filtrate to remove waste and regulate pH. Substances secreted include NH₄⁺, SO₄²⁻, H⁺, and urea.
30
What substances are reabsorbed during tubular secretion?
Sodium (Na⁺), Calcium (Ca²⁺), and Bicarbonate (HCO₃⁻) are reabsorbed from the filtrate into the blood.
31
What is the Transport Maximum (Tm)?
Tm refers to the maximum amount of a substance that can be reabsorbed by the kidneys, depending on the renal threshold and available transporters.
32
What happens if the blood glucose level exceeds the Tm for glucose (375 mg/min)?
If BGL = 400 mg/100 mL, 375 mg is reabsorbed, and 125 mg glucose is excreted in the urine.
33
What is the glomerular filtration rate (GFR)?
GFR = 125 mL/min, which equals 180 L/day of filtered fluid.
34
How do you calculate GFR using creatinine?
GFR = (Urine concentration of creatinine × Urine flow) ÷ Plasma concentration of creatinine.
35
How do you calculate urine flow rate?
Urine flow rate = Total urine volume ÷ Time (e.g., 302 mL ÷ 30 minutes = 10.07 mL/min).
36
What is renal clearance?
Renal clearance refers to how much plasma is cleared of a substance by the kidneys (filtered and secreted).
37
What happens to glucose in terms of renal clearance?
100% of glucose is reabsorbed, and its renal clearance is 0 because none is excreted.
38
What happens to creatinine in terms of renal clearance?
Creatinine is 100% cleared from plasma (not reabsorbed), so its renal clearance is 100%.
39
What is the total blood flow through the kidneys per minute?
1250 mL/min, with about 55% being plasma (700 mL/min).
40
What is the filtration fraction in the kidneys?
Filtration Fraction = GFR / Plasma Flow = 125 mL/min ÷ 700 mL/min ≈ 16-18%, meaning 16-18% of plasma is filtered.
41
What is myogenic control in short-term GFR regulation?
Reflex in smooth muscle of afferent arteriole: High BP → vasoconstriction → ↓ GFR Low BP → vasodilation → ↑ GFR
42
What is tubuloglomerular feedback and how does it affect GFR?
Macula densa detects filtrate concentration: Too concentrated → adenosine → vasoconstriction → ↓ GFR Too dilute → prostaglandins → vasodilation → ↑ GFR
43
How does the sympathetic nervous system regulate GFR long-term?
β2 receptor stimulation → vasodilation → ↑ GFR α1 receptor stimulation → vasoconstriction → ↓ GFR
44
What happens when the efferent arteriole constricts?
Increases glomerular pressure → maintains or increases GFR
45
What triggers the Renin-Angiotensin-Aldosterone System (RAAS) system, and what are the steps?
Trigger: Low BP Juxtaglomerular cells release renin → converts angiotensinogen → angiotensin I ACE converts angiotensin I → angiotensin II
46
What does angiotensin II do?
Constricts efferent arteriole → restores GFR Stimulates aldosterone → Na⁺/water retention → ↑ BP
47
What does Atrial Natriuretic Peptide (ANP) do if BP is too high?
Blocks ADH, aldosterone, and angiotensin II → lowers BP
48
What keeps the bladder relaxed when it’s filling?
Sympathetic input via β2 receptors relaxes detrusor α1 receptors keep internal sphincter closed
49
What nerve is involved in voluntary urination and which spinal levels?
Pudendal nerve (S2–S4)
50
What happens during urination?
Parasympathetic activation → detrusor contracts, internal sphincter opens External sphincter opens voluntarily
51
What percentage of body weight is water, and how is it distributed?
60% water: 40% Intracellular Fluid (ICF) – major ions: K⁺, phosphate 20% Extracellular Fluid (ECF) 15% interstitial fluid 5% plasma – major ions: Na⁺, Cl⁻
52
Where are these ions more concentrated: Na⁺, K⁺, Cl⁻, Ca²⁺?
Na⁺: More outside K⁺: More inside Cl⁻: More outside Ca²⁺: More outside
53
What are the sources of water intake/outake (2500 mL/day)?
dont need to rmb the specifics 1500 mL: Drinking 750 mL: Food 200 mL: Metabolic water ----------------- 700 mL: Sweat 200 mL: Lungs 100 mL: Feces 500 mL: Obligatory urine loss 1000 mL: Facultative loss
54
The GFR formula
The GFR = (urine conc of creatinine) X (Urine flow mL/min)
55
What is the apical side in cellular anatomy?
The side of the lumen.
56
What is the basolateral side in cellular anatomy?
The blood side.
57
In the thick segment of the ascending limb of the Loop of Henle, what goes in the apical side via the epithelial Ca2+ channel?
Ca2+.
58
In the thick segment of the ascending limb of the Loop of Henle, which ions are transported into the apical side?
Na+, K+, and 2Cl-.
59
What drug inhibits Na+, K+, and 2Cl- transport in the thick segment of the ascending limb of the Loop of Henle?
Lasix (Furosemide or water pill).
60
What effect does Lasix have in the thick segment of the ascending limb of the Loop of Henle?
It causes the loss of solutes, which in turn causes the loss of water.
61
How is Ca2+ exchanged in the thick segment of the ascending limb of the Loop of Henle?
Ca2+ enters the cell on the apical side and is exchanged for Na+ via the Na+/Ca+ exchanger to be transported to the basolateral side.
62
How is Na+ transported in the thick segment of the ascending limb of the Loop of Henle?
The Na+ from the Na+/Ca+ exchanger and transport with K+ and 2Cl- is taken out on the basolateral side via the Na+/K+-ATPase.
63
How is K+ transported into the cell in the thick segment of the ascending limb of the Loop of Henle?
K+ is transported into the cell from the basolateral side via the Na+/K+ ATPase.
64
How does Cl- leave the cell in the thick segment of the ascending limb of the Loop of Henle?
Cl- leaves the cell on the basolateral side in exchange for K+.
65
Where does K+ go after it leaves the cell in the thick segment of the ascending limb of the Loop of Henle?
K+ leaves on the apical side and is excreted via the Renal Outer Medullary K+ (ROMK) channel.
66
In the Proximal Convoluted Tubule (PCT), which ions are absorbed into the bloodstream?
Glucose, Amino Acids, Na+, Ca+, Albumins, and H2O.
67
What is the tonicity of the filtrate in the Proximal Convoluted Tubule (PCT)?
Isotonic.
68
In the Descending Limb of the Loop of Henle, what is absorbed by the vasa recta?
H2O.
69
In the Vasa Recta alongside the descending limb of the Loop of Henle, what is transported out into the medulla, creating an osmotic gradient?
Na+.
70
What is the osmolarity at the bottom of the Loop of Henle, and is it hypertonic or hypotonic?
1200mOsm, Hypertonic.
71
In the ascending limb of the Loop of Henle, what is transported into the Vasa Recta?
Na+.
72
What is the tonicity of the filtrate in the Distal Convoluted Tubule (DCT)?
Hypotonic.
73
What is the tonicity of the filtrate in the Collecting Tubule (CT)?
Hypotonic.
74
At the end of the nephron, what is the tonicity of the filtrate and its osmolarity?
Hypertonic with an osmolarity of 1200mOsm.
75
What is the total amount of Na+ circulating in the body per day?
1Kg Na+.
76
What does short-term regulation of Glomerular Filtration Rate (GFR) involve?
Nervous reflex of smooth muscles.
77
What happens when blood pressure is high in relation to GFR regulation?
Vasoconstriction, which slows GFR.
78
What happens when blood pressure is low in relation to GFR regulation?
Vasodilation, which increases GFR.
79
How does tubuloglomerular feedback control GFR?
The Macula Densa Cells detect highly concentrated filtrate and release Adenosine, which causes vasoconstriction and decreases GFR.
80
What is the role of Prostaglandins in GFR control when dilute filtrate is detected?
Prostaglandins are released, causing vasodilation and an increase in GFR.
81
Where does blood enter the nephron?
Afferent arteriole.
82
: What is the long-term control of GFR regulated by?
The sympathetic nervous system.
83
What effect does epinephrine binding to Beta 2 receptors have?
: It causes vasodilation or an increase in GFR.
84
What effect does epinephrine binding to Alpha 1 receptors have?
It causes vasoconstriction or a decrease in GFR.
85
What happens to the GFR when there is vasoconstriction of the efferent arteriole?
GFR decreases from 125mL/min to about 115mL/min.
86
What does Angiotensin II do to the efferent arteriole?
: It causes vasoconstriction, restoring GFR.
87
What hormone is released when blood pressure is low and what does it cause
Aldosterone and ADH, which cause Na+ and H2O retention and increase blood pressure.
88
What is the renin-angiotensin-aldosterone system's role in blood pressure regulation?
Low BP induces the release of Renin, which leads to the formation of Angiotensin II and raises blood pressure.
89
What does high blood pressure cause the heart to release?
Arterial Natriuretic Peptide, which inhibits ADH, Aldosterone, and Angiotensin II.
90
What is micturition?
Urination.
91
What muscles are found in the urinary bladder?
Detrusor muscles.
92
When the bladder is filled, what happens to the detrusor muscles?
They relax via sympathetic stimulus from Beta2 receptors.
93
What nerves stimulate urination?
Parasympathetic nerves via the pudendal nerve (S2, S3, S4).
94
What does the pudendal nerve do during urination?
It causes bladder contraction.
95
What type of muscle is the Internal Urethral Sphincter?
Smooth muscle that opens under bladder contraction.
96
What type of muscle is the External Urethral Sphincter?
Skeletal muscle that opens under bladder contraction.
97
How much of body weight (BW) is water, and how is it divided between ICF and ECF?
60% of BW is water, with 40% in ICF and 20% in ECF.
98
How is the 20% of ECF divided between Interstitial fluid and plasma?
15% is in Interstitial fluid, and 5% is in plasma.
99
Pyuria nephritis means...
Blood in urine
100
Nephropyelitis means...
UTI
101
BP (hydrostatic) in glomerular capillaries?
60 mmHg
102
Osmotic pressure in capillaries?
32 mmHg
103
Capsular hydrostatic pressure?
18 mmHg
104
80% of filtrate is reabsorbed where?
PCT
105
PCT reabsorbs what?
Glucose, AAs, proteins, Na⁺, Cl⁻, H₂O
106
Osmotic gradient in PCT?
Constant – 300 mOsmols (isotonic)
107
Glucose enters via...
SGLT 1/2 – secondary active transport
108
Glucose exits via...
GLUT 2 – facilitated diffusion
109
Na⁺/K⁺ transport via...
Na⁺/K⁺ ATPase – basolateral side
110
Descending LOH removes...?
Only H₂O
111
Concentration in descending limb?
HYPERTONIC
112
Only –% of substance filtered is excreted
16–18%
113
Ascending LOH removes...?
Only Na⁺
114
Concentration in ascending limb?
1200 → 100 mOsm (hypotonic)
115
Filtrate concentration in DCT?
100 → 300 mOsm (isotonic)
116
What hormone acts on CT?
ADH – reabsorbs H₂O makes urine 4x as concentrated
117
CT concentration gradient?
300 → 1200 mOsm
118
Water transport proteins?
AQP I, II, III
119
Glucose reabsorption?
SGLT (apical), GLUT (basolateral)
120
Na⁺ transporters?
Na⁺/K⁺ ATPase, ENaC
121
AA transport?
Na⁺/AA cotransporter
122
K⁺ efflux?
ROMK channels
123
Excess glucose above Tm (375) is...
Excreted in urine
124
GFR equation
(Urine creatinine conc) × (Urine flow rate)
125
Renal clearance definition
Volume of plasma cleared of substance per unit time
126
Creatinine reabsorption & clearance?
0% reabsorbed, 100% cleared
127
Glucose reabsorption & clearance?
100% reabsorbed, 0% cleared
128
Only –% of substance filtered is excreted
16–18%
129
What are the two urethral sphincters and their control types?
Internal Urethral Sphincter: Involuntary, smooth muscle External Urethral Sphincter: Voluntary, skeletal muscle
130
What is incontinence?
Uncontrolled urination, often due to nerve issues or nervousness
131
What are the two phases of urination (micturition)?
Storage Phase – Sympathetic input Voiding Phase – Parasympathetic input
132
What happens during the Storage Phase of urination?
Detrusor muscle is relaxed Internal urethral sphincter is closed Controlled by sympathetic nervous system
133
What happens during the Voiding Phase of urination?
Bladder stretch receptors activated Parasympathetic input contracts detrusor muscle Internal sphincter opens External sphincter opens voluntarily
134
What nerve is responsible for opening the external urethral sphincter?
pudendal nerve
135
The structure of an amino acid is:
NH2 - R1 - COOH NH2: Amino group COOH: Carboxyl group

A&P 2 lecture (13 decks)

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