lecture 15 (T3): micturition and glomerular filtration Flashcards
how are sensory signals from bladder stretch receptors conduction to sacral region of spinal cord
via pelvic nerves
how are sensory signals from bladder stretch receptor conducted reflexively back to bladder
via parasympathetic nerves
what are the major functions of nephrons
get rid of waste materials (urea, creatinine, uric acid, bilirubin
regulate water, electrolyte balance, body fluid osmolarity
regulate arterial pressure
regulate acid-base balance
secretion, metabolism and excretion of hormones, gluconeogenesis
how is arterial pressure regulated long term in nephrons
excrete variable amounts of sodium ions and water
how is arterial pressure regulated short term in nephrons
secrete hormones and vasoactive factors such as renin
what hormones are secreted, metabolized, and excreted from nephrons
erythropoietin
active form of vitamin D
what are the 3 processes that determine the rates at which different substances are excrete in urine
filtration, reabsorption and secretion
what is the mathematical expression of the urinary excretion rate
fitration rate-reabsorption rate+ secretion rate
what is the first step in urine formation
filtration
what are the components of the glomerular filtrate
water, ions, glucose, urea
what is the equation for the filtration fraction
GFR/renal plasma flow
what is the fraction of renal plasma flow that is filtered
20%
why are some low-molecular weight substances not freely filtered
they are partially bound to proteins
what are the 3 layers of the filtration barrier
endothelium (with fenestrae and negative charge) basement membrane (with collagen and proteoglycan fibers and strong negative charges) podocytes (with negative charges)
what is GFR determined by
balance of hydrostatic and colloid osmotic forces acting across capillary membrane
capillary filtration coefficient
what is the filterability of water
1.0
what are some diseases that lower glomerular capillary filtration coefficient
chronic uncontrolled hypertension and diabetes mellitus
define minimal change nephropathy
loss of negative charges on the basement membrane
define hydronephrosis
distension and dilation of renal pelvis and calyces
what is the numerical value for glomerular hydrostatic pressure
60 mm Hg
what is the numerical value for bowman’s capsule hydrostatic pressure
18 mm Hg
what is the numerical value for glomerular capillary colloid osmotic pressure
32 mm hg
what is the numerical value for colloid osmotic pressure of bowman’s capsule
zero
what is K1
capillary filtration coefficient= product of permeability and filtering surface area of capillaries
what happens to GFR if K1 is increased
it increases
what factors influence glomerular capillary colloid osmotic pressure
arterial plasma colloid osmotic pressure
filtration fraction
what factors increase glomerular colloid osmotic pressure
increasing filtration fraction
what variables determine GFR
arterial pressure (proportional)
afferent arterial resistance (as it increases, GFR decreases)
efferent arteriole resistance (proportional)
what is the equation for renal blood flow
(renal artery pressure-renal vein pressure)/ (total vascular resistance)
all blood vessels of the kidneys are richly innervated by _______________
sympathetic system
what are strong activations of renal sympathetic nerves
constrict renal arterioles
decrease renal blood flow and GFR
what is endothelia released by
damaged vascular endothelial cells of kidneys and other tissues
what disease states lead to an increase in plasma level associated with vascular injury
toxemia of pregnancy
acute renal failure
chronic uremia
what does endothelia contribute to
renal vasoconstriction leading to reduced GFR
hemostasis when a blood vessel is severed
what does angiotensin II do in controlling GFR
constricts efferent arterioles
formed in situations associated with decreased arterial pressure or volume depletion
why do afferent arterioles seem be protected against the effects of angiotensin II
due to release of prostaglandins and nitric oxide which are vasodilators
what is the role of nitric oxide in controlling GFR
derived from endothelial cells
basic peel helps maintain renal vasodilation
what do prostaglandins and bradykinin do in controlling GFR
they are vasodilators that may offset effects of sympathetic and angiotensin II vasoconstrictor effects
define autoregulation
relative constancy of GFR and renal blood flow
what is the primary function of autoregulation
maintain relatively constant GFR
allow precise control of renal excretion of water and solutes
prevent relatively large changes in GFR and renal excretion that would otherwise occur with changes in blood pressure
what is normal GFR
180L/day
what are the 2 components of the tubuloglomerular feedback mechanism for autoregulation
an afferent arteriolar feedback mechanism
an efferent arteriolar feedback mechanism
where is the macula densa located
distal tubule
where are juxaglomerular cells located
in afferent and efferent arterioles
what happens to flow rate in loop of henle when GFR decreases
it slows
increased reabsorption of sodium and chloride ions in ascending limb
decrease in sodium chloride in macula densa
what does a decrease in [NaCl] result in (signal from macula dense)
decrease resistance to blood in afferent arterioles
increase renin release from JG cells, angiotensin II and efferent arteriolar resistance
what is the major storage site of renin
JG cells
