Midterm Chapter 19 Flashcards
Filtration is a relatively non-selective process. Explain the advantages of filtration.
Constant filtration keep our blood clean
ex: pulling everything our of your house and only putting back in what you want to keep like 5 times a day
How many liters of filtrate are produced each day?
180L/day
The single substance that contributes most to the osmotic concentration of the ECF is what?
Na+
About how many liters of filtrate are reabsorbed each day?
178.5L/day
About what % of the filtered Na+, H2O, glucose and amino acids are reabsorbed by the PCT? List the % of each.
70% of Na+
70% of H2O
All of glucose and amino acids
About what percent of the Na+ and H2O are reabsorbed in the descending limb of the loop of Henle?
20% of H2O
No Na+
About what percent of the Na+ and H2O are reabsorbed in the ascending limb of the loop of Henle?
20% of Na+
No H2O
the DCT (especially last portion) and cortical collecting duct reabsorb (what) under the influence of aldosterone?
Na+
What hormone influences reabsorption in the DCT?
Aldosterone
The medullary collecting duct absorbs water under the influence of what?
ADH (antidiuretic hormone)
Describe the anatomy of the filtration barriers of the renal corpuscle. (include tissues and use proper terminology)
The fenestrated glomerular capillaries sit up against the basement membrane of the simple squamous epithelium of the Bowman’s Capsule which has filtration slits between the epithelial cells. (see notebook for illustration)
What substances can pass through the filtration barrier?
Small molecules such as glucose or amino acids, ions, peptides, drugs, and waste products of organic metabolism such as creatinine and urea
What substances do not pass through the filtration barrier?
Plasma proteins are NOT filtered!
(Cells, of course, are too large to be filtered. Importantly, proteins are not filtered, but are retained in the plasma. Also, small molecular weight substances that are bound to proteins will not be filtered. It is the structure of the filtration membrane that prevents proteins from being filtered.)
The pressure of the blood in the glomerular capillaries is about what?
55mmHg
Explain what specific gravity is. What is it a measure of? What might a high specific gravity of urine indicate?
Specific gravity is a measure of how concentrated the urine is (i.e. the amount of solutes it contains.)
Normal specific gravity range between about 1.003 (very dilute) and 1.030 (very concentrated).
High specific gravity can indicate dehydration
Urine has a pH that is typically about what?
somewhat acidic - about 5.5 - 6.5
List the 2 major cells (parts) of the juxtaglomerular apparatus and describe what each does.
- Macula densa - The macula densa is a collection of specialized epithelial cells in the distal convoluted tubule that detect sodium concentration of the fluid in the tubule. In response to elevated sodium, the macula densa cells trigger contraction of the afferent arteriole, reducing flow of blood to the glomerulus and the glomerular filtration rate.
- Granular cells - derived from smooth muscle cells, of the afferent arteriole secrete renin when blood pressure in the arteriole falls. Renin increases blood pressure via the renin-angiotensin-aldosterone system.
“GFR” stands for what? A typical GFR is about what?
Glomerular Filtration Rate
Typical - 180 L/day
Dilating the afferent arteriole has what effect on GFR?
It will increase it
Constricting the afferent arteriole has what effect on GFR?
It will decrease it
How does the GFR remain essentially constant despite a constantly changing mean arterial pressure (mechanisms)?
The myogenic mechanism - afferent arteriole responds to sudden changes in pressure.
Increase BP = vasoconstriction
Decrease BP = vasodialation
Describe the compensatory response of the afferent arteriole of suddenly higher mean arterial pressure. What is this mechanism called?
Tubuloglomerular Feedback - Increase in Pglom = increase in velocity of filtrate (which caused it to flow through the tubule faster than the Na+ can filter out) = too much Na+ detected by macula densa = paracrine signals sent to the afferent arteriole muscles cells instructing to vasoconstrict.
Describe the compensatory response of the afferent arteriole of suddenly lower mean arterial pressure. What is this mechanism called?
Tubuloglomerular Feedback - Decrease in Pglom = too little Na+ detected by macula densa = paracrine signals sent to the afferent arteriole muscles cells instructing to vasodialate.
Where is glucose reabsorbed in the kidney? Be specific.
In the proximal convoluted tubule (PCT)
What is the target of ADH? What effect does it have on urine volume? on urine concentration?
ADH influences the reabsorption of H2O in the collecting duct. It will decrease volume and increase concentration.
If the afferent arteriole dilates, glomerular pressure 1.(increases/decreases/is unaffected) and GFR 2.(increases/decreases/is unaffected).
- increases
2. increases
if the afferent arteriole constricts, glomerular pressure 1.(increases/decreases/is unaffected) and GFR 2.(increases/decreases/is unaffected).
- decreases
2. decreases
Does GFR fluctuate with blood pressure or is it relatively constant even when blood pressure fluctuates?
It is relatively constant due to the myogenic mechanism
The intrinsic ability of the afferent arteriole to respond to sudden changes in BP is termed the what?
Myogenic mechanism
If blood pressure suddenly increased, the afferent arteriole would respond by (1. constricting/dilating) resulting in a glomerular pressure that is (2. high/low/normal) and a GFR that is (3. high/low/normal)
- constricting
- normal
- normal
If blood pressure suddenly decreased, the afferent arteriole would respond by (1. constricting/dilating) resulting in a glomerular pressure that is (2. high/low/normal) and a GFR that is (3. high/low/normal)
- dilating
- normal
- normal
The intrinsic regulatory mechanism that relies on communication of the macula densa with the afferent arteriole is termed what?
Tubuloglomerular feedback
Increased GFR can be detected by the macula densa by detecting the levels of what in the filtrate? The macula densa then signals the afferent arteriole to (constrict/dilate) resulting in a GFR that is (high/low/normal).
Na+
constrict
normal
decreased GFR can be detected by the macula densa by detecting the levels of what in the filtrate? The macula densa then signals the afferent arteriole to (constrict/dilate) resulting in a GFR that is (high/low/normal).
Na+
dilate
normal
GFR can be regulated by other organ systems when necessary. The (1. what) division of the nervous system releases (2. what) directly onto the afferent arteriole causing it to (3. constrict/dilate) resulting in a GFR that is (4. high/low/normal). describe a situation in a person’s life when this would occur, and explain how it would help maintain homeostasis.
- Sympathetic
- norepi/epi
- constrict
- low
This would help maintain homeostasis in an emergency when blood pressure is too low due to blood loss.
GFR can be regulated by other organ systems when necessary. The hormone (1. what) acts directly on the afferent arteriole causing it to (2. constrict/dilate) resulting in a GFR that is (3. high/low/normal). describe a situation in a person’s life when this would occur, and explain how it would help maintain homeostasis.
- Angiotension 2
- constrict
- low
The transporter that reabsorbs most glucose is referred to as: (what?) What part of the uriniferous tubule has these transporters?
Cotransport (transported via a symporter with Na+)
PCT
What is the renal plasma threshold for glucose?
200mg/dL
Define the term “renal plasma threshold.”
the concentration of a substance dissolved in the blood above which the kidneys begin to remove it into the urine.
Give a general definition for the term “renal clearance.”
Renal clearance is a term that describes the rate at which a substance disappears from the body by excretion.
Define excretion.
the result of all processes that produce urine.
filtered + secreted - reabsorption = excretion
List the 3 processes that influence excretion in the kidney.
- filtration
- secretion
- reabsorption
Inulin is a substance that (1. can/cannot) be filtered, (2. can/cannot) be metabolized, (3. can/cannot) be secreted, and (4. can/cannot) be reabsorbed by the kidneys. Thus it can be used clinically to determine a person’s (5. what?) Why would you want to know this about a patient?
- can be filtered
- cannot be metabolized
- cannot be secreted
- cannot be reabsorbed
- used to determine a person’s GFR
Why - to tell how well kidneys are working
Creatinine has many of the same properties as inulin and also can be used to assess what?
GFR
