Renal Physiology Flashcards
Innervation
T10-L2 SNS
Hypo gastric Ganglion/Nerve–bladder relaxation, internal sphincter contraction
PNS (S2-S4)
Pelvic nerve
—bladder contraction
–internal sphincter relaxation
Voluntary–
Pudendal nerve
–external sphincter
Process of micturation
Bladder pressure stimulates afferent sensory nerves
Urethral sphincter relaxes
Pudendal nerve contraction to override parasympathetic micturation reflex
Filling of the bladder
Contraction of striated sphincter (somatic)
Contraction of smooth muscle (sympathetic)
Inhibition of destructor muscle (sympathetic
Emptying the bladder
Relaxation of striated spin her (somatic)
Relaxation of smooth muscle sphincter and opening of the bladder neck (sympathetic)
Detrusor muscle contraction (para)
Pressure
Stretch receptors–>SNS efferent–>pons–>SNS afferent–>NE–> B3
–>destrusor relaxation (inhibition of contraction)
NE–>alpha1–>contraction of internal urethral sphincter
SNS efferent and afferent so=hypo gastric
Pudendal–>ACh–>contract external urethral spinner
Pressure>10cmH20 (emptying phase)
> 10cmH2O–>pelvic PNS afferents–>pons–>pelvic PNS efferents–>ACh–>M3 receptors–>destrusor contraction
NO–>internal urethral sphincter relaxes
Pons–>pudendal–>ACh–>nicotinic–>contraction of external urethral sphincter until it is ready
Major functions of the Kidneys
Regulate body fluid osmolality and volumes, electrolyte balance, acid-base balance, excretion of metabolites and substances, production and secretion of hormones
Kidney Blood Flow
Renal artery, interlobar artery, arcuate artery, interlobular artery (comes second, longer name), afferent arteriole, glomerular capillaries, efferent arterioles, peritubular capillaries, interlobular vein, arcuate vein, interlobar vein, renal vein
Artery that enters the nephron
Afferent arteriole
Portion of the peritubular capillary that dives into the renal medulla
Vasa recta then back into an interlobular vein
Glomerulus vs peritubular capillary system
Glomerulus–high pressure, fluid out of capillaries
Peritubular–low pressure, filter fluid into capillaries
Two major divisions of peritublar capillary system
Cortical capillaries and deep medullary capillaries
3 layers of the barrier that any solute must pass from the glomerular capillary blood into bowman’s space
Capillary epithelium (Fenestrations) Combined basement membrane(most restrictive) Podocytes (filtration slits,structural integrity)
What does the nephron clear from blood plasma
Unwanted substances:
Urea, creatinine, Uris acid, unrated, Na+, K+, Cl-, H+, Drugs, organics
Blood supply to glomerular capillaries
Afferent arteriole
Blood supply to peritubular capillaries
Efferent arteriole
GFR values
100-140 ml/min (120 ml/min)
180 L/day
99% reabsorbed, 179 liters/day
Always permeable to H20
Proximal convoluted
Thick descending limb
Thin descending limb
Half of loop
Never permeable to H2O
Half of loop
Thin ascending limb
Thick ascending limb (distal straight tubule)
Distal convoluted tubule (early)
ADH permeable to H2O
Late distal convoluted tubule, cortical and medullary collecting tubule
GFR
Glomerular capillary permeability/surface area product (Kf)
Times the net hydrostatic pressure (glomerular capillary minus bowman’s) minus the PCOP (colloid pressure of glomerular capillary blood)
Kf
Permeability times surface area
Permeability: Fenestrations, basement membrane, filtration slits
Surface area:capillary size and number
Major Determinants of GFR
1) hydrostatic or blood pressure
2) permeability/cell-cell junctions
3) plasma components
Pt normal value
Normally 0 due to the drainage by the PCT
Blocking of a structure beyond the glomerulus will cause problems
Actual GF
Kf X ((Pc-Pt)-PIc)
Efferent Arteriole protein concentration
Higher on oncotic pressure, increased protein concentration
Even point where filtration=reabsorption is right before the efferent arteriole, therefor you are ALWAYS FILTERING
The high osmotic pressure will draw H2O back into the peritubular capillary from the PCT, more water into extracellular space
Why does reabsorption back into the capillary on the venular end occur?
Colloid osmotic pressure is much greater than tissue colloid pressure
Water in via osmosis
Equal point of filtration in skeletal muscle vs glomerular capillaries
Due to the high hydrostatic pressure in glomerular capillaries, the colloid osmotic pressure doesn’t reach or surpass it until the efferent capillary
The equal point is when hydrostatic pressure=colloid osmotic pressure
WHat can/cannot pass through glomerular capillary wall?
Water, urea, glucose, inulin, creatinine–Can
Myoglobin, Hb, serum albumin cannot
Renal blood flow effect on Glomerular filtration
Increase flow, increases GFR
Increasing Glomerular pressure
Decreasing osmolality of blood passing through glomerulus since there is less time for blood to lose fluid and increase osmolality
Arterial pressure effect on GFR
Increase arterial pressure, increase GFR by increase glomerular pressure
But–auto regulation makes this a disproportional increase
Afferent arteriole diameter on GFR
Constriction decreases RBF, decrease blood to glomerulus, decreasing glomerulus pressure, decreasing GFR
Dilation–>increase RBF–>increase GP—>increase GFR
Efferent Diameter effect on GFR
Small construction will decrease outflow, increase pressure, increase GFR
Moderate degree of constriction will decrease GFR because blood stays longer in the Glomerulus–>plasma osmolality increases–>filtration decreases
Sympathetic stimulation effect on GFR
Afferent arterioles constrict preferentially to decrease GFR
Could decrease GFR to small perfect, and urinary output could decrease to 0
Kidney stone blocking ureter
Increase hydrostatic pressure in bowman’s space, decreasing GFR, no change in RBF
Reabsorption
Transfer of solute so from tubular fluid (pre-urine) to blood
Solute are subtracted from the filtered amount of pre-urine
Can be passive but often requires ATP
Glucose filtered-glucose excreted
Ureters
Visceral smooth muscle tubes
More urine via peristalsis waves
30 cm long
Connects posterior base of the bladder neck
Clearance
Result of filtration to the tubules or secretion back into the tubule.
Dimensions are crucial
VOLUME/TIME
INPUT=OUT
Only input=arterialx=venousx+urinex
Renal Clearance of a Solute verbal equation
Plasma concentration of a solute times the renal plasma flow of the solute in the artery is equal to (plasma venous concentration of solute times renal plasma flow in veins) plus (urine concentration of X times urine flow rate)
But venous content of X should be 0 (since all is excreted)
Cx
Virtual input volume
Or
RPFa
Classic Clearance Equation
Cx= (Ux times V)/Pax (arterial plasma concentration)
Formula for RPF
Clearance of PAH
Cpah=(Upah times V)/Ppah
RBF equation
RPF/(1-Hct)
(Upah X V)/Ppah all divided by 1-Hct
Cpah/(1-Hct)
Normal value of GFR
120 ml/min
Cannot be considered a clearance because there’s no volume component
GFR conditions
Amount filtered=amount excreted
NO REABSORPTION OR SECRETION CAN TAKE PLACE
Two substances that can be used to measure GFR
Inulin, creatinine
Normal values for Creatinine in urine and plasma
Urine–125
Creatinine-1-2
If Ccr isn’t equals to Ci or GFR, you have renal disease
Filtration Fraction
Fraction of renal plasma flow that becomes glomerular filtrate
FF= GFR/RPF
GFR=120
RPF=600
Normal FF=0.2
On average, a person gets about 20% of their plasma filtered per minute by the kidneys
Cpah equals GFR, RPF, or RBF?
RPF