bio exam 4- Urinary System
Three pathways of the release of renin.
1. Direct stimulation of the granular cells (as part of the baroreceptor reflex) by the SNS 2. Stimulation of the granular cells by input from the activated macula densa cells (macula densa cells sense low NaCl concentration they signal granular cells to release renin) 3. Reduced stretch of granular cells (act as mechanoreceptors) a drop in BP reduces tension on granular cells and stimulates them to release more renin.
Functions of the nephrons include: 1. 2. 3.
1. Glomerular filtration 2. tubular reabsorption 3. tubular secretion
Urine formation involves what 3 processes
1. Glomerular filtration -(dumping into waste container) takes place in renal corpuscle 2. Reabsorption- (Reclaiming what the body needs to keep) selectively moving filtrate back into the blood 3. Secretion- (Selectively adding to the waste retainer) selectively moving substances from the blood into the filtrate
What are the 2 mechanisms of Renal Autoregulation or the Intrinsic controls of GFR?
1. Myogenic mechanism - VSM of arterioles, it contracts when stretched and relaxed when not stretched 2. Tubuloglomerular feedback - directed by the macula densa cells of the juxtaglomerular complex. These cells located in the walls of the ascending limb of the nephron loop, respond to NaCl concentration (which varies with filtrate flow). They respond by releasing vasoconstrictor chemicals that cause constriction of afferent arteriole, reducing blood flow into the glomerulus.
What are the 2 Extrinsic controls of GFR?
1. Sympathetic Nervous System Controls 2.
What are 2 anatomical features of the Renal corpuscle:
1. The endothelium of the Glomerulus capillaries has Fenestrated pores 2. Epithelial cells of the Glomerular Capsule that are called podocytes with foot processes (fenestration slits) so filtrate can enter easily
GFR is___ml/min
125ml/min or 180L per day
Hydrostatic pressure in the Glomerular capillaries (the glomerular blood pressure)
55 mm Hg (vs. 35 mm Hg in all other capillaries) The hydrostatic pressure in glomerular capillaries is HIGHER than other capillaries in the body
The glomeruli function as filters. High glomerular blood pressure is ___
55mm Hg
A major stimulus for the release of antidiuretic hormone is __________.
A major stimulus for the release of antidiuretic hormone is a rise in plasma osmolality. ADH results in increased water reabsorption.
Which of the hormones below is responsible for facultative water reabsorption?
ADH
What does the Peritubular capillaries exchange with?
ALL other parts of the nephron tubule
What hormone promotes active tubular secretion of potassium ions in the late distal convoluted tubule (DCT) and collecting ducts?
Aldosterone
Which of the following regulates the secretion of K+ into the filtrate?
Aldosterone
Macula densa cells
Chemoreceptors that monitor NaCl content of the filtrate entering the Distal Convoluted Tubule
The intrinsic renal control myogenic mechanism ____ when stretched (dues to high BP) and ___ when not stretched
Contracts when stretched and relaxes when not stretched. Rising blood pressure stretches vascular smooth muscle in the afferent arteriole walls causing it to constrict. This constriction restricts blood flow into the glomerulus and prevents glomerular blood pressure from rising to damaging levels.
What nephron has a short loop in the cortex?
Cortical
Which nephrons are most abundant?
Cortical 85%
What are the 2 types of nephrons?
Cortical and Juxtamedullary
Where does mostly secretion take place?
Distal convoluted tubule
which control regulates extremely low systemic blood pressure? Intrinsic or Extrinsic?
Extrinsic, Intrinsic controls cannot handle extremely low blood pressure, such as might result from serious hemorrhage. (Once BP drops below 80 mm Hg autoregulation and extrinsic controls take over).
Angiotensin II is a substance made by the body to lower blood pressure during stress. T or F
False it increases BP when it drops too low
Water can leave the ascending limb of the loop of Henle. T or F
False, Water can leave the descending limb of the loop of Henle but not the ascending limb.
What type of capillaries are the glomerular capillaries? What is their function?
Fenestrated capillaries. Their function is to filter large amounts of plasma into the glomerular capsule.
What feature makes the Glomerulus capillaries pourous?
Fenestrated pores
Name the tubular components of a nephron in the order that filtrate passes through them.
Filtrate is formed in the glomerular capsule and then passes through the proximal convoluted tubule, the descending and ascending limbs of the nephron loop, and the distal convoluted tubule (and into the collecting duct)
Where does filtration take place?
Glomerular capsule: glomerulus capillaries = Renal corpuscle
_________ is the chief force pushing water and solutes out of the blood and across the filtration membrane.
Glomerular hydrostatic pressure (HPg)
What are the 2 nephron capillary beds?
Glomerulus capillaries and Peritubular capillaries - also have vasa recta
Low blood pressure causes the ____ cells of the juxtaglomerular complex to release renin.
Granular cells
If the efferent arteriole constricts while the afferent arteriole remains unchanged, the glomerular filtration rate __________.
If the efferent arteriole constricts while the afferent arteriole remains unchanged, the glomerular filtration rate increases. This will increase glomerular hydrostatic pressure.
Where does the hormone controlled reabsorption processes take place?
In the DCT and the collecting duct
Granular cells
In the arteriole walls act as mechanoreceptors that sense blood pressure in the afferent arteriole
The renin-angiotensin-aldosterone mechanism is the body's main mechanism for _____ blood pressure. (increasing/decreasing)
Increasing blood pressure.
What are the 2 cell types at the collecting ducts? What are their functions?
Intercalated cells - microvilli, maintains the acid-base balance of blood Principle cells - water and salt balance
What are the 2 controls of GFR?
Intrinsic controls(Renal Autoregulation) - within the kidney Extrinsic controls - nervous & endocrine system (hormones)
How does the Glomerulus capillaries differ from other capillaries in the body?
It is fed AND drained by arterioles - the afferent arteriole and the efferent arteriole. This maintains the high pressure that is needed for filtration. Filtration absorbs a large amount of fluid through reabsorption by the renal tubule cells (mostly PCT) and returned to the blood via peritubular capillaries.
What nephron has a long loop into the medulla?
Juxtamedullary - play an important role in concentrated urine
Match the response to the function: Baroreceptors Chemoreceptors Macula densa cells SNS stimulation Granular cells
Macula densa cells = chemoreceptors Baroreceptors=Granular cells Baroreceptors= SNS stimulation
The ascending limb of the Nephron loop is ___ to water
NOT permeable to water, permeable to solutes Na+ and Cl- move out of the filtrate
Extrinsic controls are the ___ and ____ mechanisms
Neural and Hormonal
Vasa Recta
ONLY in the Juxtamedullary nephrons vessels that extend into the long loops in them medulla.
What does the Glomerulus capillaries exchange with?
ONLY the Glomerular capsule
The mechanism of water reabsorption by the renal tubules is ________.
Osmosis
Which hormone raises blood calcium levels?
PTH
Glomerular filtration
Passive process in which hydrostatic pressure forces fluids + solutes through membrane
Where does the efferent arteriole feed into?
Peritubular capillaries or vasa recta
The descending limb of the Nephron loop is ____ to water
Permeable to water - the water leaves the filtrate
Which tubule contains microvilli? Why? Proximal convoluted tubule or Distal convoluted tubule
Proximal Convoluted Tubule -contains microvilli to increase surface area for Reabsorption
Which area is most active in tubular reabsorption ?
Proximal Convoluted Tubules are most active in reabsorption. Most of the nutrients, water and sodium ion and the bulk of actively transported ions are reabsorbed here.
Where does mostly reabsorption take place?
Proximal convoluted tubule
Which tubule has cuboidal epithelial cells and large mitochondria with microvilli at the apical surface?
Proximal convoluted tubule
What takes over during Neural renal control?
Sympathetic Nervous system - when BP is normal the SNS stays at rest and the renal blood vessels are dilated and renal autoregulation is in control, however, when BP is very low it is necessary for the SNS to take over. When BP falls norepinephrine is released and causes VSM to constrict increasing BP. This is part of the baroreceptor reflex. As part of this reflex the afferent arterioles also constrict which decreases GFR and helps restore BV & BP.
Each collecting duct receives filtrate from MANY nephrons. T or F
TRUE
Renin is an enzyme released by the juxtaglomerular cells of the kidneys in response to low blood pressure, causing the transformation of angiotensinogen to angiotensin I.
TRUE
The Nephron Loop has a descending and ascending limb. Which one is thin and which one is thick?
The Descending Limb is thin- simple squamous, The Ascending Limn is thick - simple cuboidal
Where does the afferent arteriole feed into?
The Glomerulus capillaries
The blood supply to the nephron is the __________.
The blood supply to the nephron is the afferent arteriole.
Why is the glomerular capillary hydrostatic pressure higher (55mm Hg) than other capillaries in the body?
The glomerular capillaries are drained by a high-resistance efferent arteriole whose diameter is smaller than the afferent arteriole that feeds them. As a result, filtration occurs along the entire length of each glomerular capillary and reabsorption does not occur as it would in other capillary beds.
high blood pressure in the glomerulus occurs because:
The glomeruli are fed and drained by arterioles, and the afferent arterioles are larger in diameter
A nonfasting urine sample from an individual who has previously ingested donuts and a soft drink showed the presence of sugar (glucose). Which of the following statement explains the presence of the glucose in the urine?
The individual exceeded transport maximum - with limited glucose transporters the kidneys can be temporarily overwhelmed by high sugar load after eating.
The major calyces are the __________.
The major calyces are the large branches of the renal pelvis.
What is the countercurrent multiplier in the kidney?
The nephron loop of a juxtameduallary nephron
Which process results in increased blood pressure in response to hormone release?
The renin-angiotensin-aldosterone mechanism results in increased blood pressure in response to hormone release.
What are the structural differences between juxtamedullary and cortical nephrons?
The structural differences are: (1) juxtamedullary nephrons have long nephron loops (with long thin segments) and renal corpuscles that are near the cortex-medulla junction, whereas cortical nephrons have short nephron loops and renal corpuscles that lie more superficially in the cortex; (2) efferent arterioles of the juxtamedullary nephrons supply vasa recta, while efferent arterioles of the cortical nephrons supply peritubular capillaries.
Glomerular filtration rate (GFR)
The volume of filtrate formed each minute by all nephrons. The Net Filtration Pressure in the glomerulus favors filtration over the entire length of the capillary bed unlike other capillary beds where filtration only occurs at the arteriole end and reabsorption occurs at the venous end. As a result the kidneys produce 125ml/min or 180 L of filtrate per day!
Where are macula densa cells and what do they respond to0?
These cells located in the walls of the ascending limb of the nephron loop respond to filtrate NaCl concentration. When GFR increases, there is not enough time for reabsorption and the concentration of NaCl in the filtrate remains high
ADH is released by the posterior pituitary gland.
True
Aldosterone is produced in the adrenal cortex in response to angiotensin II
True
In situations where there is an extreme change of blood pressure (e.g., mean arterial pressure of less than 80 mm Hg), extrinsic controls take precedence over intrinsic blood pressure controls. T or F
True
The descending limb of the loop of Henle is relatively impermeable to solutes and freely permeable to water. T or F
True, The countercurrent multiplier functions because of two factors: (1) the descending limb of the loop of Henle is relatively impermeable to solutes and freely permeable to water; and (2) the ascending limb is permeable to solutes, but not to water.
Which of the following hormones is important in stimulating water conservation in the kidneys?
antidiuretic hormone
If the Tm for a particular amino acid is 120 mg/100 ml and the concentration of that amino acid in the blood is 230 mg/100 ml, the amino acid will ________.
appear in the urine
Where does antidiuretic hormone (ADH) exert its effects to promote water reabsorption?
collecting duct
In the presence of ADH urine is
concentrated in smaller amounts. As ADH rises the collecting ducts come more permeable to water
The function of angiotensin II is to ________.
constrict arterioles and increase blood pressure
Sympathetic NS activation causes ___
constriction of the afferent arterioles which decreases urine formation
In the absence of ADH the urine is ____
dilute in large amounts The dilute urine is formed because the dilute filtrate reaching the collecting duct is simply allowed to pass from the kidneys
What type of capillaries make up the glomerulus?
fenestrated
The filtration membrane consists of:
fenestrated glomerular endothelium, basement membrane, and the podocyte-containing visceral layer of the glomerular capsule. It permits free passage of substances.
The factor favoring filtrate formation at the glomerulus is the ________.
glomerular hydrostatic pressure
The chief force pushing water and solutes out of the blood across the filtration membrane is ________.
glomerular hydrostatic pressure (glomerular blood pressure)
Excretion of dilute urine requires ________.
impermeability of the collecting tubule to water
What results from increased levels of aldosterone?
increased Na+ reabsorption
ADH acts on the ____________ to ___________ water excretion.
kidneys; decrease
When the concentration of ADH increases, __________.
less urine is produced
Tubuloglomerular feedback mechanism is directed by the ___ cells of the ____ complex.
macula densa cells of juxtaglomerular complex.
The basic functional unit of the kidney is the __________.
nephron
The most important factor affecting the glomerular filtration rate is __________.
net filtration pressure
The glomerular (Bowman's) capsule and glomerulus make up the __________.
renal corpuscle
Aldosterone increases reabsorption of ___ mostly in the ___
sodium in the Distal Convoluted Tubules
Which structure is the muscular tube that delivers urine to the bladder?
ureter
The kidneys regulate:
urine volume, composition, pH of the blood, and eliminate nitrogenous wastes
The macula densa cells respond to high levels of NaCl in the filtrate by releasing _____ chemicals that cause _____ of the afferent arteriole.
vasoconstrictor that cause intense constriction of the afferent arteriole reducing blood flow in the glomerulus. This drop in blood flow decreases GFR, slowing the flow of filtrate and allowing more time for filtrate processing (NaCl reabsorption).
Antidiuretic Hormone (ADH) increases reabsorption of ___ in the ____
water by the collecting ducts
