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Kinesiology > Urinary System Physiology > Flashcards

Urinary System Physiology Flashcards

1
Q

Kidneys

A 
Functions include 
Excretion of waste 
H2O balance (plasma volume)
Blood pressure control (renin)
Acid base balance 
Blood cell production (erythropoietin)
Vitamin D activation
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2
Q

Urinary system

A

Consists of
Kidneys
Blood supply (20% total flow)
Transport vessels (ureters, urinary bladder, urethra)

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3
Q

Kidney anatomy

A

Renal calyces
Renal cortex (outer)
Renal medulla (inner)
Renal pelvis

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4
Q

Nephron

A

Functional unit of kidney
~1million/kidney
2 types = cortical (shorter, ~85%), juxtamedullary (longer, ~15%, osmotic gradient)
Tubule portion and blood supply portion
Vascular component = renal artery, afferent arteriole, glomerulus (ball like tuft of capillaries), efferent arteriole, peritubular capillaries, vein

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5
Q

Tubule

A 
Bowman’s capsule 
Proximal tubule 
Loop of henle (ascending, descending) 
Distal tubule 
Collecting duct
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6
Q

Basic renal processes

A 
Glomerular filtration (fluid into tubule) 
Tubular reabsorption (from tubule into blood)
Tubular secretion (from blood into tubule)
Urine comes as a result of these three things
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7
Q

Sites of action

A

Filtration = Bowman’s capsule
Reabsorption and secretion = proximal tubule, distal tubule (hormone controlled), collecting ducts
Loop of henle = creates osmotic gradient (reabsorption)

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8
Q

Substance fates

A

Substances can be =
Filtered and secreted (some only secreted)
Filtered and reabsorbed
Filtered and partially reabsorbed

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9
Q

Kidney functions

A

Glomerular filtration = all but RBCs and proteins (too big)
Reabsorption = Na+, Cl-, Ca2+, PO4, water, glucose
Secretion = K+, H+, large organics

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10
Q

Glomerulus

A

Tuft of capillaries (fenestrated, more permeable)

Surrounded by Bowman’s capsule

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11
Q

Glomerular filtration

A

Across 3 layers of the glomerular membrane =
Glomerular capillary wall
Basement membrane (a cellular gelatinous layer of collagen and glycoproteins)
Inner layer of Bowman’s capsule (consists of podocytes that encircle the glomerulus tuft)
~160-180L/day (~125ml/min)
Moves electrolytes, water, and glucose into tubules (RBCs and most proteins are too large to be filtered)
Urine <1% of filtrate

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12
Q

Location in nephron, volume of fluid, osmolarity of fluid

A

Bowman’s capsule = 180L/day, 300 mOsM
End of proximal tubule = 54L/day, 300 mOsM
End of loop of henle = 18L/day, 100 mOsM
End of collecting duct (final urine) = ~1.5L/day, 50-1200 mOsM

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13
Q

Podocytes

A 
Can change shape (control filtration) 
Renal failure (large slits, allows RBCs and proteins in)
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14
Q

Forces involved in glomerular filtration

A

3 main physical forces involved =
Glomerular capillary blood pressure
Plasma-colloid osmotic pressure
Bowman’s capsule hydrostatic pressure (Bowman’s capsule osmotic pressure)

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15
Q

Force, effect and magnitude in glomerular filtration

A

Glomerular capillary blood pressure = favours filtration, 55mmHg
Plasma colloid osmotic pressure = opposes filtration, 30mmHg
Bowman’s capsule hydrostatic pressure = opposes filtration, 15mmHg
Net filtration pressure (difference between force favouring filtration and forces opposing filtration) = favours filtration, 10mmHg

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16
Q

Glomerular filtration rate (GFR)

A

Depends on =
Net filtration pressure
How much glomerular surface area is available for penetration
How permeable the glomerular membrane is (podocytes slit size can change with infection)
GFR will change if the blood hydrostatic pressure changes
Auto-regulated = tubuloglomerular feedback (local (paracrine) control), hormones/autonomic (change arteriole resistance)

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17
Q

Arterioles control GFR

A

Resistance changes in renal arterioles later renal blood flow
A lower GFR if afferent arteriole constricts or if efferent arteriole dilates
A higher GFR if afferent arteriole dilates or if efferent arteriole constricts

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18
Q

Extrinsic control on GFR

A

Sympathetic control =
Long term regulation of arteriole BP
Input to afferent arterioles (baroreceptor reflex)
Lower blood pressure means lower GFR and retention of fluids

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19
Q

Other examples of when GFR can change

A

Plasma colloid osmotic pressure changes = eg) severely burned patient increases GFR, loss of proteins from blood to repair sites lowers osmotic pressure
Dehydrating diarrhea decreases GFR (loss of fluids increases osmotic pressure)
Bowman’s capsule hydrostatic pressure changes (obstructions such as kidney stone or enlarged prostate, elevates capsular hydrostatic pressure, decreases GFR)

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20
Q

Measuring GFR

A

Use inulin to measure
No reabsorption or secretion
Therefore, excretion = filtration

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21
Q

Movement

A

Trans-cellular transport = active or passive, eg) Na+ or glucose
Paracellular transport = passive only, diffusion of water, ions

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22
Q

Tubular reabsorption

A 
Passive = no energy required, down electrochemical gradient or osmotic gradients 
Active = requires energy, moves against electrochemical gradients
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23
Q

Na+ reabsorption

A

Active process
Na+ - K+ ATPase pump in basolateral membrane is essential for Na+ reabsorption
Affects reabsorption of other substances
Na+/K+ pump creates Na+ gradients across membranes
Facilitates Na+ reabsorption

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24
Q

Tubule area, % of Na+ reabsorbed, role of Na+ reabsorbed

A

Proximal tubule = 67%, plays role in reabsorbed great glucose, amino acids, H2O, Cl-, and urea
Ascending limb of the loop of henle = 25%, plays critical role in kidneys ability to produce urine of varying concentrations
Distal and collecting tubules = 8%, variable and subject to hormonal control; plays role in regulating ECF volume

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25
Q

Reabsorption of other substances

A

Following the reabsorption of Na+ :
Water reabsorption (via osmotic gradient created)
Cl- reabsorption (via electrical gradient)
Glucose (by carries)

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26
Q

Glucose reabsorption

A

Sodium linked glucose reabsorption in the proximal tubule
Tubular maximum = point where all the glucose carriers are full, excess glucose stays in the tubules and is lost in the urine

27
Q

Renal threshold

A

Blood glucose level where the carriers are full and glucose is seen in the urine
Eg) diabetes mellitus

28
Q

Urea reabsorption

A

Urea = small, diffusible
Passive process
To equilibrium
50%

29
Q

Reabsorption

A 
Na+ = 99.9%, Na+/K+ ATPase pump 
Cl- = 99%, electrical gradient 
Water = 99%, osmotic gradient 
Glucose = 100%, carrier mediated 
Urea = 50%, passive
30
Q

Aldosterone

A

Controls Na+/K+ ATPase pumps
Released if blood volume is low
High aldosterone = increased speed of pump, increased Na+ reabsorption, increased water reabsorption (decreased urine)
Eg) dehydration

31
Q

Renin-angiotensin-aldosterone system

A

Regulates Na+ and blood pressure and blood volume

32
Q

Atrial Natriuretic Peptide (ANP)

A

Antagonist to aldosterone
Inactivates Na+/K+ ATPase pump
Inhibits Na+ reabsorption
Secreted by atria with = increased blood pressure, increased Na+, increased stretch of atria (increased volume)

33
Q

Secretion

A 
Transfer of molecules from extra cellular fluid into tubule 
Active process 
K+ (Na+/K+ pump)
H+ (acid-base balance)
Large organics (biotransformed)
34
Q

Counter-current mechanism

A

Descending loop of henle = permeable to water, impermeable to salts, filtrate becomes more concentrated
Ascending loop of henle = permeable to salts (actively reabsorbs NaCl), impermeable to water, filtrate becomes less concentrated

35
Q

Vasa recta

A

Vessel following loop of henle

Similar osmotic gradient in blood supply

36
Q

Loop of henle

A

Creates a large, vertical osmotic gradient in medulla

100-1200 mOsM/L

37
Q

Water reabsorption

A

ADH causes insertion of water pores into the apical membrane
ADH = anti-diuretic hormone
Controls permeability of collecting ducts
Released if blood osmolarity high
Low ADH = impermeable to water, dilute urine (high volumes) eg) water loading
High ADH= due to high blood osmolarity, makes collecting duct permeable to water, concentrates urine (lower volumes) eg) dehydration

38
Q

Dehydration

A 
Increase ADH
Increase aldosterone 
Decrease ANP
Increase water reabsorption 
Decrease urine volume (more concentrated)
39
Q

Behavioural mechanisms

A

Drinking replaces fluid loss
Low sodium stimulates salt appetite
Avoidance behaviours help prevent dehydration (eg - desert animals avoid the heat)

40
Q

Water loading

A 
Decreased ADH
Decreased aldosterone 
Increased ANP
Decreased water reabsorption 
Increase urine volume (more dilute)
41
Q

Proximal tubule

A

67% of Na, Cl, and water reabsorption
100% glucose and amino acids are reabsorbed
K is secreted/reabsorbed (small amount)
Variable H secretion occurs
Organic ion secretion (not controlled)
Phosphate and electrolytes (controlled, variable reabsorption)
Urea reabsorption (to equilibrium 50%)

42
Q

Distal tubule

A

Variable Na reabsorption (controlled by aldosterone and ANP)
Variable water reabsorption (controlled by aldosterone and ANP)
Variable K secretion/reabsorption (controlled by aldosterone)
Variable H secretion (depends on acid-base balance)

43
Q

Collecting ducts

A

Site of water reabsorption
Controlled by ADH
Concentrated the urine
Requires osmotic gradient (loop of henle)
Variable water reabsorption (controlled by ADH)
Variable H secretion
Variable urea reabsorption (related to loop of henle)

44
Q

Excretion

A

Excretion = filtration - reabsorption + secretion
Clearance = rate at which a solute disappears from body
Non-invasive way to measure GFR (inulin and creatine)

45
Q

Renal clearance

A 
RC = UV/P
RC = renal clearance rate (ml/min)
U = concentration (mg/ml) of the substance in urine 
V = flow rate of urine formation (ml/min; GFR) 
P = concentration of the same substance in plasma
46
Q

Inulin/glucose clearance

A

Inulin clearance is equal to GFR

Glucose clearance is usually zero because of 100% reabsorption

47
Q

Micturition

A

The urination reflex
Autonomic control of sphincters and detrusor muscle
CNS can over-ride or initiate

48
Q

Muscle and innervation

A

Detrusor (smooth muscle) =parasympathetic (causes contraction), inhibited during filling, stimulated during micturition
Internal urethral sphincter (smooth muscle) = sympathetic (causes contraction), stimulated during filling, inhibited during micturition
External urethral sphincter (skeletal muscle) = somatic motor (causes contraction), stimulated during filling, inhibited during micturition

49
Q

During filling

A

Bladder (detrusor) muscle is relaxed

Sphincters are contracted

50
Q

During micturition

A

Stretch receptors increase their firing
Sphincters are relaxed
Detrusor muscle contracts
Urine flows out of bladder

51
Q

Renal failure

A

Wide ranging consequences
Causes = infectious organisms, toxic agents, inappropriate immune responses, obstruction of urine flow, an insufficient renal blood supply
Build up of wastes to toxic levels (vomiting, diarrhea, cellular necrosis)
Loss of calcium (osteoporosis)
Na+/K+ imbalance (affects nerve and muscle)
Loss of proteins (edema)
Loss of RBCs (anemia)
Low blood pressure (decreased renin, dizziness)

52
Q

Kidney stones

A

Crystallization of minerals in either the kidney, ureters, or bladder
Calcium
Oxalates (veggies, spinach, beets)
Dehydration (binge drinking)

53
Q

Acid-base balance

A

Normal pH of 7.38-7.42
H+ concentration is closely regulated
Abnormal pH can alter tertiary structure of proteins and affects the nervous system
Acidosis = neurons become less excitable and CNS depression
Alkalosis = hyper excitable
pH disturbances (with K+ disturbances)

54
Q

Acidosis

A

Metabolic acidosis = metabolic organic acid production, lactic acid (exercise), ketoacids (diabetes), diarrhea, organic acids intake (diet)
Respiratory acidosis = production of CO2 (acid production)

55
Q

Alkalosis

A

Metabolic alkalosis = vomiting, dietary sources of bases (a few), pyloric stenosis
Respiratory alkalosis = hyperventilation

56
Q

pH homeostasis

A

Buffers = combines with or releases H+
Ventilation = 75% of disturbances
Renal regulation = slowest of the 3 mechanisms, directly excreting or reabsorbing H+

57
Q

Buffers

A 
Fastest response (within seconds)
Combines with H+ so it doesn’t affect pH
Phosphate 
Protein - hemoglobin 
Bicarbonate
58
Q

Respiratory compensations

A

pH is adjusted by changing rate and depth of breathing (reps done within minutes)
CO2 + H2O H2CO3 H+ + HCO3-

59
Q

Respiratory corrections

A

Reflex pathway for respiratory compensation of metabolic acidosis (increase breathing)

60
Q

Renal compensation: kidney

A 
Slowest response (within hours)
Can retain or eliminate H+ or H2CO3- 
Apical Na+ - H+ exchanger (NHE)
Na+ - HCO3- symport 
H+ - ATPase 
H+ - K+ ATPase 
Na+ - NH4 antiport
61
Q

Body’s correction for acidosis

A

To raise body pH =
Buffers bind to H+
Breathing increases (decreases CO2 and H+ via carbonic acid)
Kidney excretes H+ and keeps bicarbonate

62
Q

Body’s correction for alkalosis

A

To lower pH =
Buffers release H+
Breathing slows down (retains CO2 and H+)
Kidney retains H+ and secretes bicarbonate

63
Q

Intercalated cells

A

Type A = function in acidosis, secrete H+, reabsorb bicarbonate
Type B = function in alkalosis, secrete bicarbonate, reabsorb H+

Kinesiology (19 decks)

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