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Human physiology > Lecture 17: Micturition and glomerular filtration > Flashcards

Lecture 17: Micturition and glomerular filtration Flashcards

1
Q

Micturition reflex

A

Superimposed micturition contraction begins to appear as bladder fills
Sensory signals from bladder stretch receptors
Reflex contractions relax spontaneously when bladder is only partially filled
Once initiated, the micturition is self-regenerative
The self-regenerative reflex fatigues after a few seconds and the bladder relaxes
As bladder continues to fill, micturition reflexes occur more often and more powerful
When reflex is powerful enough, it causes a second reflex, passes through pudendal nerves to inhibit external sphincter
Higher brain centers (in pons) keep micturition partially inhibited except when it is desired
When it is time to urinate, cortical centers can facilitate the sacral micturition centers to help initiate reflex and at the same time inhibit external urinary sphincter

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2
Q

Sensory signals from bladder stretch receptors

A

Conducted to sacral region of spinal cord via pelvic nerves

Conducted reflexively back to bladder via parasympathetic nerves

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3
Q

Nephron functions

A

Get rid of waste material
Regulate water/electrolyte balance
Regulate body fluid osmolarity
Regulate arterial pressure- long/short term mechanisms
Regulate acid-base balance
Secretion, metabolism, excretion of hormones
Gluconeogenesis

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4
Q

Three processes that determine the rates at which different substances are excreted in the urine

A

Filtration
Reabsorption
Secretion

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5
Q

Urinary excretion rate

A

UER= Filtration rate - reabsorption rate + secretion rate

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6
Q

Components of glomerular filtrate

A

Water
Ions
Glucose
Urea

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7
Q

Filtration fraction equation

A

FF= GFR/Renal plasma flow

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8
Q

% of plasma flowing through kidney that is filtered

A

20%

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9
Q

Low-molecular weight substances filtration

A

Some low-molecular weight substances are not freely filtered because they are partially bound to proteins

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10
Q

What is the glomerular filtration rate

A

125ml/min= 180L per day

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11
Q

Layers of filtration barrier

A

Endothelium- w/fenestrae and negative charges
Basement membrane- w/collagen, proteoglycan filaments and strong negative charges
Podocytes- w/negative charges

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12
Q

GFR determined by

A

Balance of hydrostatic and colloid osmotic forces acting across capillary membrane
Capillary filtration coefficient

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13
Q

Water has a filterability of

A

1.0

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14
Q

Capillary filtration coefficient

A

Product of permeability and filtering surface area of capillaries

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15
Q

Diseases that lower glomerular capillary filtration coefficient

A

Chronic uncontrolled hypertension and diabetes millitus

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16
Q

Define minimal change nephropathy

A

Loss of negative charges on the basement membrane

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17
Q

Define hydronephrosis

A

Distension and dilation of renal pelvis and calyces

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18
Q

GFR equation

A

GFR= K1 x Net filtration pressure

19
Q

K1 is the

K1 equation

A

Capillary filtration coefficient

K1= GFR/Net filtration pressure

20
Q

Net filtration pressure is

A

Glomerular hydrostatic pressure- 60mm Hg
Bowmans capsule hydrostatic pressure- 18mm Hg
Glomerular capillary colloid osmotic pressure- 32mm Hg
Colloid osmotic pressure of bowmans capusle- 0

21
Q

Effects of increasing/decreasing K1

A

Increase K1- raises GFR

Decrease K1- reduces GFR

22
Q

Factors that influence glomerular capillary colloid osmotic pressure

A

Arterial plasma colloid osmotic pressure

Filtration fraction

23
Q

Factors that increase glomerular colloid osmotic pressure

A

Increasing filtration fraction

24
Q

Increase in arterial pressure causes

A

Increases glomerular hydrostatic pressure which increases GFR

25
Q

Increase in afferent arteriolar pressure causes

A

Decrease in glomerular hydrostatic pressure which decreases GFR

26
Q

Increase in efferent arteriolar pressure causes

A

Increase in glomerular hydrostatic pressure which increases GFR (slightly)

27
Q

Kidneys have __x the blood flow of the brain and __x the oxygen consumption of the brain

A

7x the blood flow of the brain but only 2x the oxygen consumption

28
Q

Much of the oxygen consumed by the kidneys is related to

A

The high rate of active sodium reabsorption

29
Q

Tubular sodium reabsorption is closely related to

A

GFR and rate of sodium filtered

30
Q

Renal blood flow equation

A

RBF= (Renal artery pressure- Renal vein pressure) / (Total vascular resistance)

31
Q

Blood vessels in kidney are richly innervated by

A

Sympathetic nervous system

32
Q

Strong activation of renal sympathetics causes

A

Constrict renal arteries
Decrease renal blood flow and GFR
Moderate sympathetic activation has little effect

33
Q

Hormones controlling GFR consistency

A 
Norepinephrine/epinephrine- parallel the sympathetic system
Endothelin
Angeiotensin II
Endothelial-derived NO
Prostaglandins and bradykinin
34
Q

Endothelin

A

Released by damaged vascular endothelial cells
May contribute to renal vasoconstriction
May contribute to hemostasis
Plasma levels increase in certain disease states associated with vascular injury

35
Q

Angiotensin II

A

Constricts efferent arterioles– increases GFR
Formed in situations associated w/decreased arterial pressure or volume depletion
Does not constrict afferent arterioles

36
Q

How are afferent arterioles protected against effects of angiotensin II

A

Due to release of prostaglandins and NO (both vasodilators)

37
Q

NO derived from

A

Endothelial cells

38
Q

Prostaglandins/bradykinin

A

Vasodilators that may offset effects of sympathetic and angiotensin II vasoconstrictor effects (especially on afferent arterioles)

39
Q

Definition/function of autoregulation

A

Refers to relative consistency of GFR and renal blood flow
Maintain relatively constant GFR
Precise control of renal excretion of water/solutes
Prevent relatively large changes in GFR and renal excretion that would otherwise occur w/changes in blood pressure

40
Q

Tubuloglomerular feedback mechanisms for autoregulation

A

Afferent and efferent arteriolar feedback mechanisms

41
Q

Juxtaglomerular complex

A

Macula densa in distal tubule

Juxtaglomerular cells in afferent and efferent arterioles

42
Q

Decrease GFR causes

A

Slow flow rate in loope of henle
Increased reabsorption of Na/Cl ions in ascending limb
Decrease in sodium chloride at macula densa

43
Q

Decrease in NaCl results in a signal from ___

A 
Macula densa which causes
Decreased resistance to blood in afferent arterioles
Increases renin release from JG cells
Increase angiotensin II
Increase efferent arteriolar resistance

Human physiology (16 decks)

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