ch. 19 physio
What are the hormones that influence hormone control?
- Angiotensin II (strong vasoconstrictor and has a low filtration coefficient) - Prostaglandins ( vasodilation, and has a high filtration coefficient)
Explain the primary active transport of sodium in the epithelial transport.
- Lumen to cell Na+ electrochemical gradient (ENaC) Proximal tubule: Na+ -H exchanger 1. Na+ enters cell through various membrane proteins, moving down its ENaC. 2. Na+ is pumped out of the basolateral side of cell by the Na+-K-ATPase pump.
What are the 2 influencing factors on GFR?
- Net filtration pressure ( hydrostatic and colloid osmotic pressure) - Filtration coefficient
What are the kidneys made up of?
- Renal capsule structure (tough atipose tissue) - Renal cortex (outer) - Renal medulla (inner) - Renal pelvis
What is filtration coefficient?
- Surface are for filtration ( high surface area=high filtration) - Permeability of the filtration membrane ( size barrier) Proteins dont fit through
Explain the secondary active transport, symport with Na+ in the epithelial transport.
- Symport with Na+ - lumen to cell: apical cell surface: SGLT (Na glucose transporter): Na+ -glucose cotransporter - Cell to interstitial fluid: basolateral cell surface: GLUT: glucose transporter Na/K ATPase pump. 1. Na+ moving down its electrical gradient uses the SGLt protein to pull glucose into the cells against electrical gradient. 2. Glucose diffuses out the basolateral side of the cell using the GLUT protein. 3. Na is pumped out by Na+-K+-ATPase pump.
What does transport maximum mean?
- Tmax # of solutes vs. # of transporters. - can only transport as much as a transporter can handle. - when it reaches 100% it levels off
What are the 3 pressures that influence glomerular filtration.
- capillary blood pressure - capillary colloid osmotic pressure - capsule fluid pressure
What is the equation for renal clearance?
clearance of S = mass S excreted per time/ plasma [S] - volume of plasma from which S is removed per unit of time - what you clear from from your plasma
What is clearance?
clearance of a solute is the rate at which that solute disappears from the body by excretion or by metabolism.
If plasma creatinine = 1.8 mg/ 100mL plasma, urine creatinine = 1.5 mg/mL urine, and urine volume is 1100 mL in 24 hours, what is the creatinine clearance? what is GFR?
creatinine clearance= creatinine excretion rate/ [creatinine] plasma = (1.5 mg creatinine/mL urine 1.1 L urine/day) / 2.8 mg creatinine/100 mL plasma. Creatinine clearance is about 92 L/day, and GFR is equal to creatinine clearance.
What three basic processes that take place in the nephron?
filtration, reabsorption, and secretion
What are the nephrons?
formed by the layers of the outer cortex and inner medulla, they are organized arrangements of microscopic tubules. - About 80% of the nephrons in a kidney are almost completely contained within the cortex, but the other 20%- called the juxtamedullary nephrons- dip down into the medulla.
What is glucosuria?
glucose in the urine - high glucose in the blood means you have disbetes mellitus.
What is the general rule for efferent arterioles?
indirect relationship with met filtration pressure - low blood flow out of glomerulus = high GFR - high blood flow out of glomerulus = low GFR
What is creatinine?
is a breakdown product of phosphocreatine, an energy-storage compound found primarily in mucles.
What is saturation?
it refers to the maximum rate of transport that occurs when all available carriers are occupied by substrate.
Where is the juxtaglomerular located?
on the ascending loop of Henle and renal corpuscle
What is insulin clearance?
polysaccharide not normally found in the body - insulin clearance = glomerular filtration rate (GFR) - insulin is filtered but not reabsorbed or secreted Pin= plasma concentration Uin= urine concentration V= volume in urine
What active transports can you have for secretion?
primary, secondary AND tertiary - 1. direct active transport- the Na+-K-ATPase keeps intrascelluar Na low. - 2. secondary indirect active trasport- the Na+ -dicarboxylate contransporter (NaDC) concentrates a dicarboxlyate inside the cell using energy stored in the Na+ gradient. - 3. Tertiary indirect active transport- the basolateral organic anion transporter (OAT) concentrates organic anions (OA-) inside the cell, using the energy stored in the dicarboxylate gradient.
What is valslva maneuver?
pushing on your stomach to urinate - voluntary contraction of abdominal walls and expiratory muscles
What is secretion?
removal from the blood, get rid of it. - removing from blood stream and putting it back into the filtrate.
What is excretion?
removal in the urine, unless it is reabsorbed into the body. - total removal - normal: 1.5L/day, 50-1200 mOsm
What is reabsorption?
return to blood, put in back. - taking out of filtrate and putting it back in blood stream.
What are the mesangial cells?
smooth muscle cells, between and around loops of glomerular capillary. - they are blood flow regulators - and have the ability to constrict and restrict blood flow through glomerulus.
What are podocytes?
specialized cells that surround each glomerular capillary. They have long cytoplasmic extensions called foot processes that extend from the main cell body.
What happens in epithelial transport?
substances cross the apical and basolateral membranes of the tubule epithelial cell to reach interstitual fluid.
What happens in the paracellular pathway?
substances pass through the cell-cell junction between two adjacent cells.
What is neural control of GFR mediated by?
sympathetic neurons that innervate both the afferent and efferent arterioles. - sympathetic innervation of alpha receptors on vascular smooth muscle cause vasocontriciton= decreased GFR
What is the renal corpuscle?
the combination of glomerulus and Bowman's capsule
What are the three filtration barriers that substance must pass through before entering the tubule lumen?
the glomerular capillary endothelium, a basal lamina (basement membrane), and the epithelium of Bowman's capsule.
What is the myogentic response of afferent arterioles?
the intrinsic ability of vascular smooth muscle to respond to pressure changes. - high blood flow = high smooth muscle stretch = high Ca+ influx. ** calcium in, maintains normal GFR***
recap: what are the vasa recta?
the long peritubluar capillaries that dip into the medulla.
What is macula densa?
the modified portion of the tubule epithelium that is a plaque cell. In the tubuloglomeruarlar feedback.
What is filtration?
the movement of fluid from blood into the lumen of the nephron. it takes place ONLY in the renal copuscle, where the walls of glomerular capillaries and Bowman's capsule are modified to allow bulk flow of fluid.
What is filtration fraction?
the percentage of total plasma volume that filters into the tubule
What is micturition?
the process of urination
What is renal physiology?
the study of kidney function
How is filtration related to GFR in a transport maximum?
there is a direct relationship high glucose = high GFR of glucose
What is the general rule about afferent arterioles in GFR?
there is a direct relationship with net filtration pressure. - high blood flow into glomerulus = high GFR - low blood flow into glomerulus = low GFR
What is the function of the renal port system?
to filter fluids out of the blood and into the lumen of the nephron at the glomerular capillaries, then to reabsorb fluid from the tubule back into the blood at the peritubular capillaries.
What is urea passive reabsorption?
urea is a waste product. helps manipulate concentration gradients
What is micturition?
urination
Recall: blood flows path of least resistance. What happens when you vasoconstrict afferent arterioles?
vasoconstrict afferent = high resistance = low flow in afferent = low pressure (Pc) = low filtration rate. - low flow = low filtration
What is the path of excretion of urine?
water and solute move from the plasma into the hollow tubes of the nephron that make up the bulk of the paired kidneys. These tubules modify the composition of the fluid as it passes through. The modified fluid leaves the kidneys and passes into a hallow tube called a ureter. There are two ureters, one leading from each kidney to the urinary bladder. The bladder expands and fills with urine until, by reflex action, it contracts and expels urine through a single tube, the urethra.
What are filtration slits?
when foot processes wrap around the glomerular capallaries and interlace with another one, which leaves these narrow filtration slits.
What are the resting states of micturition and the storage reflexs?
- detrusor muscles: normal state= relaxed - internal urethral sphincter: normal state = passively contracted (smooth muscle, involunatary) - External urethral sphincter: normal state = tonically contracted (skeletal voluntary)
What is the renal corpuscle made up of?
- glomerulus ( endothelium, fenestrated capillaries, basement membrane) - Bowman's capsules ( parietal layer-outside, Bowman's space, visceral layer- cells right on capillary) - Filtration membrane (endothelium, fused basal lamina, and podocytes)
What are the mechanisms of reabsorption?
- paracellular pathway - Epithelial transport - Urea passive reabsorption - plasma protein endocytosis
What are the functions of the kidneys?
- regulation of extracellular fluid volume and blood pressure (when extracellular fluid volume decreases, blood pressure also decreases) - regulation of osmolarity - maintenance of ion balance ( Na, Ca, K ) - Homeostatic regulation of pH - manipulation of plasma H+ and HCO3 - Excretion of waste (nitrogenous waste, creatinine, some hormones, drugs and toxins) - Production of hormones ( erthropoietin, renin, and vitamin D production)
What are the steps of tunuloglomerular feedback?
1. GFR increases 2. Flow through tubule increases 3. Flow past macula densa increases 4. Paracine from macula densa to afferent arterioles 5. Afferent arterioes constrict ( resistance in afferent arterioles increase) ( hydrostatic pressure in glomerulus decreases) ( GFR decreases)
Why bother to filter 180 L/day and then reabsorb 99% of it? Why not simply filter and excrete 1% that needs to be eliminated? (2 reasons)
1. many foreign substances are filtered into the tubule but not reabsorbed into the blood. The high daily filtration rate helps clear such substances from the plasma very rapidly. Once a substance filters into the lumen of Bowman's capsule, it is no longer part of the body's internal environment. 2. filtering ions and water in the tubule simplifies their regulation. If a portion of filtrate that reaches the distal nephron is not needed to maintain homeostasis, it passes into the urine.
What is the average filtration rate?
180 L/24 hrs OR 7.5 L/hr OR 125 mL/min
What is plasmas osmolarity? (#)
300 mOsm
Name one way in which filtration and secretion are alike, Name one way in which they differ.
Filtration and secretion both represent movement from the extracelluar fluid into the lumen. Filtration takes place only at Bowman's capsule; secretion takes place all along the rest of the tubule.
What is equation for tubular secretion?
Amount excreted = amount filtrated - amount reabsorbed + amount secreted
Ion regulation is a key feature of kidney function. What happens to the resting membrane potential of a neuron if extracellular K+ levels decrease?
If extracellular K+ decreases, more K+ leaves the neuron, and the membrane potential hyperpolarizes (becomes more negitive, increases)
How is reabsorption relationed to Tmax
Below Tmax: high glucose = high GFR of glucose Above Tmax: high glucose = constant GFR of glucose
How is excretion related to Tmax?
Below renal threshold: high glucose = no excretion of glucose Above renal threshold: high glucose = excretion of glucose
What is the path of blood flow through the kidneys?
Blood enters the kidney through the renal artery before flowing into smaller arteries and then into the cortex. Blood flows from the afferent arterioles into a ball-like network of capillaries know as the glomerulus. Blood leaving the glomerulus flows into the efferent arterioles, then into a second set of capillaries, the peritubular capillaries that surround the tubule. In the juxtamedullary nephrons, the long peritubular capillaries that dip into the medulla are called the vasa recta. Finally renal capillaries join to form venules and small veins, conducting blood out of the kidney through renal veins.
What happens to the force of cardiac contraction of plasma Ca+ levels decrease substantially?
If plasma Ca+ decreases, the force of contraction decreases.
What would happen to the body if filtration continued at a normal rate but reabsorption dropped to half the normal rate?
If reabsorption decreases to half the normal rate, the body would run out of plasma in under an hour.
What do the renal veins do?
Carry blood from the kidneys to the inferior vena cava.
what is the relationship between urea and clearance?
Clearance < GFR - reabsorption
If systemic blood pressure remains constant but the afferent arterioles of a nephron constrict, what happens to renal blood flow and GFR in that nephron?
If the afferent arterioles constricts, the resistance in that arteriole increases, and blood flow through that arteriole is diverted to lower-resistance arterioles. GFR decreases in the nephron whose arteriole constricts.
What is the equation for clearance of S?
Cs = (Us*V) / Ps where, Cs = clearance of S Us = urine concentration of S V = urine volume per unit of time Ps = plasma concentration of S (Us*V) = amount in the urine
What are the variations on manipulations of materials in glomerular filtration and some tubular reabsorption?
Excretion < filtration less more
What are the variations on manipulations of materials in glomerular filtration and total tubular reabsorption?
Excretion = 0 , excretion << filtration total reabsorption
What are the variations on manipulations of materials in glomerular filtration and tubular secretion?
Excretion > filtration more less
What is the path of filtrated fluids starting with Bowman's capsule?
From Bowman's capsule, filtrated fluids flows into the proximal tubule, then into the loop of Henle, a hairpin shaped segment that dips down towards the medulla and then back up. The loop of Henle is divided into two limbs, a thin descending limb and an ascending limb with a thin and thick segment. The fluid then passes into the distal tubule. The distal tubules of up to 8 nephrons drain into a single larger tubule and its collecting ducts together form the distal nephron. Collecting ducts pass from the cortex through the medulla and drain into the renal pelvis. From the renal pelvis, the filtered and modified fluid, now called the urine, flow into the ureter on its way to excretion.
What does GFR stand for? and what is it? as well as the normal averages for it?
Glomerular filtration rate. GFR = amount of plasma filtered per time 70 kg person= 180 L/24 hrs or 7.5 L/hr or 125 mL/min
A water molecule enters the renal corpuscle from the blood and ends up in the urine. Name all the anatomical structures that the molecule passes through on its trip to the outside world.
Glomerulus-- Bowman's capsule-- proximal tubule-- loop of henle-- distal tubule-- collecting duct-- renal pelvis-- ureter-- urinary bladder-- urethra
What is the equation for net filtration pressure in glomerulus? and what does these stand for: Pc Pf TTc
NFP = Pc - TTc - Pf OR NFP = Pc - (Pf + TTc) in out Pc = capillary hydrostatic pressure (filtration) 55 mm Hg Pf = glomerular capsule fluid hydrostatic pressure (absorption) 15 mm Hg TTc = capillary colloid osmotic pressure (absorption)
What is the equation for net filtration reabsorbed into capillaries?
NFP= Pc - TTc Pc= peritubular capillary hydrostatic pressure (filtration), 10 mm Hg. TTc - capillary colloid osmotic pressure (absorption), 30 mm Hg
Why is the osmotic pressure of plasma in efferent arterioles high than that in afferent arterioles?
Osmotic pressure is higher in efferent arterioles because fluid volume is deceased there, leaving the same amount of protein in a smaller volume
Most of the reabsorption takes place where?
Proximal tubule. - with a small amount of reabsorption in the distal segments of the nephrons.
What happens when you vasodilate efferent arterioles?
Vasodilate = low resistance = high flow in efferent = low pressure (Pc) = low filtration rate - high flow = low filtration
A person with cirrhosis of the liver has lower-than-normal levels of plasma proteins and consequently a high-than-normal GFR. Explain why a decrease in plasma protein concentration causes an increase in GFR.
The primary driving force for GFR is blood pressure opposed by fluid pressure in Bowman's capsules and colloid osmotic pressure due to plasma protein. With fewer plasma proteins, the plasma has lower-than-normal colloid osmotic pressure. With less colloid pressure opposing GFR, GFR increases.
What drives filtration across the walls of the glomerular capillaries?
The process is very similar in many ways to filtration of fluid out of systemic capillaries
If a hypertensive person's blood pressure is 143/107 mm Hg and mean arterial pressure is diastolic pressure + 1/3 the pulse pressure, what is this person's mean arterial pressure? What is this persons GFR?
This persons mean arterial presssure is 119 mm Hg, and GFR is 180 L/day
What happens when you vasocontrict efferent arterioles?
Vasocontrict = high resistance = low flow in efferent = high pressure (Pc) = high filtration rate - high resistance = low flow and high filtration
Recall: blood flows path of least resistance. What happens when you vasodilate afferent arterioles?
Vasodilate = low resistance = high flow in afferent = high pressure (Pc) = high filtration rate. - low resistance= high flow, high filtration
If net filtration out of glomerular capillaries occurs, then you know that capillary hydrostatic pressure must be (greater than/less than/equal to) capillary colloid osmotic pressure.
When net filtration out of the glomerular capillaries occurs, the capillary hydrostatic pressure must be greater than the capillary colloid osmotic pressure.
If net reabsorption into peritubular capillaries occurs, then capillary hydrostatic pressure must be (greater than/ less than/ equal to) the capillary colloid osmotic pressure.
When net reabsorption into the peritubular capillaries occurs, the capillary hydrostatic pressure must be less than the capillary colloid osmotic pressure.
What are the Boqman's capsules?
Where the nephrons began. - they are hallow, ball-like structures that surrounds the glomerulus.
What is tubuloglomerular feedback?
a paracine signaling mechanism through which changes in fluid flow through the loop of Henle influence GFR. local control. - Macula densa monitors Na+ in filtrate - high Na+ filtrate = high paracrine release = afferent arterioles vasocontriction = lower GFR (less blood flowing in, means lower GFR)
What do the renal arteries do?
branch off the abdominal aorta and supply blood to the kidneys.
What is the relationship between glucose and clearance?
clearance = 0 - total reabsorption
What is the relationship between insulin and clearance?
clearance = GFR - no reabsorption - no secretion
What is the relationship between penicillin and clearance?
clearance >> GFR - much more - secretion
What is autoregulation having to do with GFR?
autoregulation of glomeular filtration rate is a local control process in which the kidney maintains a relatively constant GFR in the face or normal fluctuations on blood pressure
What does retroperitoneal mean?
behind the peritoneum. - the kidneys are behind the peritoneal cavity, so they are refereed to this
