Exam 4 Flashcards
What are the two types of substances removed?
- By-products of metabolism
– Creatinine from muscle metabolism
– Urea from amino acids - Foreign substances, such as drugs
environmental toxins
– Saccharin in artificial sweetener
– Benzoate in diet soda
What is gluconeogenesis?
In times of starvation we convert fat into glucose
Why do we have a high rate of kidney flow?
To maintain fluid and electrolyte levels that are important to heart health
What is filtration driven by?
Pressure system. Selects based on size
What is a nephron?
The structural and
functional units that form urine.
What is secretion?
Selectively moving things out of the blood and into the tubule.
What is the equation for urinary clearance?
Excretion = Filtration - Absorbance + Secretion
aka
E = F - R + S
Where is the cortex?
It is surrounding the kidney
Is the glomerulus high or low pressure?
It is high pressure
What are the 2 types of nephrons?
Cortical nephrons and juxtamedullary nephrons
What is filtered in the glomerulus?
Plasma
What does the glomerular capsule do?
It collects the filtrate
What is wrapped around the capillaries in the glomerulus?
Podocytes
What is the function of podocytes?
Wraps around capillaries so they don’t break apart in the high pressure environment
T or F
Capillaries are leaky.
True!
How do capillaries regulate filtration?
They are leaky, but the holes are fairly small, so size is the only regulation, anything in the plasma that is smaller than a protein will end up in filtrate
What happens in the proximal convoluted tubule?
Reabsorption- taking back what we want to keep
What happens in the nephron loop?
Reabsorption of water and salt
What is reabsorption in the distal convoluted tubule and collecting duct regulated by?
Regulated by hormones
What is Glomerular filtration rate?
GFR is blood flow coming into the glomerular through the afferent. The amount of filtrate we’re making over time.
What is the most driving force of GFR?
Blood pressure, which is really high inside the glomerular.
What is the relationship between BP and GFR?
Directly related, if BP goes up, then GFR goes up.
How is GFR affected by exercise?
GFR increases during exercise because BP goes up.
What is the effect of a constantly increased GFR?
If we increase GFR for too long we won’t be able to keep all the correct nutrients and things we don’t want to lose. Think of chronic high blood pressure.
How do we change the pressure in GFR?
Myogenic controls, which is changing the sizes of the afferent and efferent arteries.
What happens to Glomerular filtration rate if BP goes up?
GFR goes up. We constrict the afferent artery to decrease blood flow into glomerulus to decrease the pressure. Then dilate efferent to also reduce pressure inside.
What happens with myogenic controls when BP goes down?
Efferent is constricted to keep the pressure up so GFR doesn’t go down.
What are the 3 mechanisms to control the GFR?
Myogenic control, JG cells, macula densa cells.
What is the renin pathway?
Renin is released from JG cells.
In the liver, angiotensinogen is converted to angiotensin 1 which enters the blood.
In the bloodstream, ACE converts angiotensin 1 into angiotensin 2 which has 2 effects.
Angiotensin 2 constricts all of the arterioles which directly increase BP. 2nd effect is the angiotensin 2 goes to the adrenal cortex and triggers the release of hormone aldosterone.
Aldosterone goes back to the kidney and increases sodium reabsorption in the CD/DCT. This increase water reabsorption which increases BV and therefor increases BP.
Explain ADH stimulus, sensor, type of receptor, and effector.
Stimulus for ADH release is an increase in the osmolarity of the blood (can happen from too much salt or dehydration). The hypothalamus is what detects this shift. Then, hypothalamus increases ADH output, which increases the number of aquaporins in the CD/DCT to increase water reabsorption. The hypothalamus also increases the thirst drive. Urine output decreases.
Explain ANP stimulus, sensor, type of receptor, and effector.
Stimulus for ANP is an increase in blood pressure, then it inhibits renin. Urine production goes up because we don’t reabsorb salt as much, so water doesn’t move out. Traps sodium in the filtrate to hold water and increase urine output which decreases blood volume and decreases blood pressure.
Explain Renin stimulus, sensor, type of receptor, and effector.
Stimulus for renin/aldo is decrease in BP. The JG cells are the sensor. They are mechanoreceptors. Response is constriction of arterioles and release of hormone aldo which increases sodium reabsorption in CD/DCT
How is salt reabsorbed?
By sodium potassium pump using active transport by ATP
How is water reabsorbed?
By osmosis through aquaporins by following salt.
How much glucose is reabsorbed?
100%
What is the purpose of the loop of henle?
For reabsorption of water and salt. Concentrates urine and saves as much water as possible.
What happens in the descending limb in the loop of henle?
The descending limb is permeable to water and impermeable to salts. Water moves through aquaporins. Gets much saltier the further along it travels.
What happens in the ascending limb?
Ascending limb is impermeable to water and actively pumps salt out. No aquaporins on this side.
How much nutrients get reabsorbed in the PCT?
100%
Why would there be glucose in the urine?
Transport maximum is exceeded with diabetes and why there is glucose in the urine
What is a reason someone with diabetes would be dehydrated?
In diabetes, excess glucose in filtrate makes water not absorb as much because it follows concentrate