Lecture 61/63/64 Flashcards
Excretion
Kidneys - excrete ___soluble things
Liver - things soluble in ___
water
fat
What are the waste contents of urine
H+, creatinine (from the muscles), Urea (protein metabolism by product)
What are the two major functions of the Kidney?
and three minor ones?
- Maintain the volume and composition of the ECF
- Excrete waste products
also:
Control of blood pressure
activates Vitamin D
make EPO - message to bone marrow to make RBCs
From what us urine made mostly?
Plasma
How much plasma does it take to make 2 litres of urine?
200 Litres
What percentage of cardiac output goes to the Kidneys?
20-25%
The amount of solute excreted is the
=______ - _____ + _______
Amount filtered - amount reabsorbed + amount secreted
______inter-digitate over the surface of the capillaries.
The “truck” around with the capillaries wrap themselves is the mesangial cell
podocytes inter-digitate over the surface of the capillaries.
The “truck” around with the capillaries wrap themselves is the mesangial cell
Filtered substances pass through ___________ _____ and filtration slits
Filtered substances pass through endothelial pores and filtration slits
What happens to the Glomerular filtration rate when the afferent arteriole dilates?
It increases
What happens to renal blood flow when the afferent arteriole dilates?
it inncreases
overcomes Resistance of efferent arteriole
What is the glomerular filtration rate? (GFR)
Volume of plasma filtered by the glomerulus per unit time
Inulin is the ideal substance for determining GFR because…
It is not reabsorbed, secreted or metabolised.
It is exogenous (comes from outside the body)
How do you check, with inulin
Check the amount that is in the blood and the urine, to determine how much was filtered. Clearance
What is renal clearance?
Clearance is defined as the rate of urinary excretion of a substance, relative to its plasma concentration.
“How much you see in the urine?”
What normally happens to the GFR if mean arterial pressure increases from 90 to 110 mmHg
It doesn’t change
MAP doesn’t really affect
__________maintains a nearly constant GFR when mean arterial blood pressure is between 80 and 180 mm Hg
Autoregulation maintains a nearly constant GFR when mean arterial blood pressure is between 80 and 180 mm Hg
What cells line the wall of the tubule, between the afferent arteriole and the distal convoluted tubule
macula densa
Macula densa acts, in the presence of too much volume in the distal tubule to:
releases paracrine:
afferent arteriole constricts
resistance in afferent arteriole increases
hydrostatic pressure in glomerulus decreases
GFR decreases
Renal excretion can be altered by what:
Renin-angiotensin system
SNS
Atrial natriuretic peptide (comes from heart - if too much blood)
Vasopressin
Atrial natriuiretic peptide is released when there is ________ of the muscular walls of the heart.
Its a signal that there is too much ______ _____ in the system
Atrial natriuiretic peptide is released when there is stretching of the mscular walls of the heart.
Its a signal that there is too much blood volume in the system
where does aldosterone comes from?
Adrenal glands
What does the renin-angiotensin (and aldosterone) system regulate?
The renin-angiotensin system (RAS) or the renin-angiotensin-aldosterone system (RAAS) is a hormone system that regulates blood pressure and water (fluid) balance.
It increases BP and blood volume by aloowing reabsorption of
How does noradrenaline help reduce blood volume?
SNS messages
Noradrenaline contrictrs the pre-glomerular arteriole
what does aldosterone do?
Aldosterone causes the tubules of the kidneys to increase the reabsorption of sodium and water into the blood. This increases the volume of fluid in the body, which also increases blood pressure.
True or False:
ANP will act on the post-gromerular arteriole to dilate and increase the GFR
False.
ANP will act on the pre-glomerular arteriole to dilate and increase GFR
True or False:
ANP also has an action on the collecting duct to inhibit the reabsorption of Na+
True
Which tubular activity is bigger?
Reabsorption (200L down to 2L of urine)
Where in the nephron is reabsorption the greatest?
proximal tubule
want to get the bulk processing done early
What is the most important solute to be reabsorbed? Why?
Sodium
the reabsorbtion of sodium, so many other things won’t happen properly
True or False
Na+ is reabsorbed by active transport
True
When Na+ is moves across back into the ECF, what follows?
Anions (charge)
H20 (osmotic gradient created, follows) - through aquaporins
K+/Ca2+/urea start to get concentration in the tubule so they also cross
What is cotransported out of the lumen with Na+?
Glucose
Glucose appears in the diabetics urine because diabetes….
There’s a certain capacity on the amount of glucose that can be reabsorbed. Diabetic plasma exceeds the amount that can be reabsorbed.
___% of the oxygen consumption by the kidney is due to sodium reabsorption.
80% of the oxygen consumption by the kidney is due to sodium reabsorption.
Sodium balance:
Input is from ___
Output is mostly urine, but also ___ and ___
Sodium balance
Input is from diet
Output is mostly urine, but also faeces and skin
There is a lag phase in terms of sodium balance due to…
There is a lag phase in terms of sodium balance due to the renin-angiotensin and aldosterone acting on the collecting duct
Infusion of 1L of normal saline will cause a change in blood volume of:
3/4 of ECF is in the interstitial spaces
therefore 0.25L will increase in the plasma volume
The body detects sodium balance through…
carotid baroreceptors
Renal arterial pressure receptors in the afferent arteriole
Renin will be released when ___ is _____
Which is detected by:
Volume is Low:
which is detected by:
Fall in pressure at preoglomerular arteriole
Reduction in sodium chloride delivery to macula densa
SNS activation
