Lecture 10 - Urinary system Flashcards
What do arterial baroreceptors do
respond to changes in arterial pressure
Nerve ending highly sensitive to stretch or distortion
The degree of stretching is directly proportional to blood pressure
How do you treat hypertension (high blood pressure)
Diuretics: increase excretion of sodium and
water, decreasing cardiac output with no
change in peripheral resistance
Beta-adrenergic receptor blockers: Reduce
cardiac output
Calcium channel blockers: Reduce entry of
calcium in vascular smooth muscle cells =
weaker contractions = lowers peripheral
resistance
Angiotensin-converting enzyme (ACE)
inhibitors: Final step in formation of
Angiotensin II (a vasoconstrictor) is mediated
by an ACE. Blocking this enzyme causes
vasodilation lowering peripheral resistance
What does aldosterone do
slow-acting steroid hormone that stimulates
sodium reabsorption by kidney tubules
What does Vasopressin do (anti-diuretic hormone)
rapid-acting
peptide produced by the pituitary gland which stimulates
water reabsorption
What do Angiotensin-converting enzymes (ACEs) do
Found on endothelial cells
How to kidneys regulate blood pressure
intra-renal
baroreceptors detect changes in stretching with changes in blood
volume which stimulates a change in the production of renin
How does the heart interact with the kindeys
Produce ANP - Atrial natriuretic peptide which
1. Inhibits sodium reabsorption by kidney tubular cells
2. Acts on renal blood vessels to increase filtration rate causing
sodium excretion
3. Inhibits the action of aldosterone
What happens if there is a blood loss
Compensatory movement of interstitial fluid
into the capillaries to increase plasma volume
But this is a redistribution of fluid and not a
replacement of fluid
Other slower effects include:
- an increase in thirst
- a decrease in salt and water excretion
Mediated by hormones and kidney function:
- renin, angiotensin and aldosterone
What are the ratios for heat lost at rest in ambient environmental conditions
60% via radiation
* 12% via convective air currents
* 3% via conduction (e.g. feet to floor)
* 25% via evaporation (lungs and skin)
How does heat loss during exercise differ from rest
Up to 80% via evaporation of sweat from
the skin (dependent on humidity)
How does the kidney help during a water deficit
Help to conserve body water
and electrolytes during period
of increased loss
What does renal mean
“pertaining to the kidneys”.
The kidneys process the plasma portion of blood by
removing substances from it and, in some cases, by
adding substances to it”
What do the kidneys do
Remove waste products (e.g. urea) and foreign chemicals (e.g.
drugs) from the blood
* Regulate total body water, salts and acid base balance – kidneys
excrete just enough water and salts to maintain homeostasis
* Involved in gluconeogenesis (e.g. during fasting, the kidneys
produce glucose from amino acids that is released into the blood)
* Release hormones that regulate blood pressure (e.g. renin) and
EPO (increases number of red cells)
* Produce an active from of Vitamin D that influences calcium
balance and promotes strong, healthy bones
What are the sections of the urinary system
Kidney, uteter, bladder, urethra
What is the parts of a kidney
Renal pelvis, nephron, renal medulla, renal cortex, ureter
What does the renal corpuscle do
Forms a filtrate from blood
free from cells and proteins
- Filtrate leaves the corpuscle
and enters the tubule
- As it flows through the
tubule, substances are
added/removed
- Remaining fluid combines in
collecting ducts and exits the
kidneys as urine
What are the 2 types of nephron
Juxtamedullary and cortical
What are the components of the renal corpuslce
Bowmans capsule - containing podocytes
Glomerulus - contains afferent and efferent arterioles
What are fenestrae
small pores found in this instance on a podocyte
What are the 3 layers of filtration in the Bowmans capsule
Single cell lining of the capillary endothelium
Non-cellular protein-rich layer of basement membrane
Single cell lining of the Bowman’s capsule
What are the glomerular capillaries specialized for
Filtering
What do the peritubular capilaries do
Supply the nephron/tubules with their own blood supply
They then form the veins
where blood leaves the kidney
What are juxtamedullary nephrons (slide 29)
15% of all kidney nephrons
* Renal corpuscle close to cortical-medullary junction
* Henle’s loops plunge deep into the medullar
* Generate osmotic gradient for water reabsorption
What are cortical nephrons (slide 29)
These represent the majority of the kidney nephrons
* Corpuscle located in outer cortex
* Henle’s loops do not plunge deep into the medullar
What are the sections of the juxtaglomerular apparatus
Juxtaglomerular cells
Macula Densa
What does the Macula Densa do
Contains sensors that detect changes in blood composition
What do juxtaglomerular cells do
- Secrete RENIN
- Influence the formation of
ANGIOTENSIN 2 - Controls blood pressure
(vasoconstriction and
sodium/water retention)
Distal tubule
(not connected to
Bowman’s
capsule directly)
Macula
Densa
Contain sensors that de
What are the 3 distinct inputs to juxtaglomerular cells that increase renin secretion
1) Renal sympathetic nerves
2) Intrarenal baroreceptors
3) Macula densa
What does isotonic mean
he same
concentration of nonpenetrating
solutes as normal extracellular fluid.
What is a hypotonic solution
have a lower
concentration of nonpenetrating solutes
compared to normal extracellular fluid.
- water rushes in to the cell to dilute
intracellular solutes
What is a hypertonic solution
have a higher
concentration of nonpenetrating
solutes compared to normal
extracellular fluid.
- water rushes out of the cell to
dilute extracellular solutes
What is glomerular filtration
Urine formation begins with the filtration of
plasma from glomerular capillaries into the
Bowman’s space
What ultra-filtrate
The filtrate is cell free and, except for
large proteins, contains all the substance
in virtually the same concentrations as in
plasma
What is favouring filtration (slide 38)
P-GC = Glomerular capillary blood pressure
What is opposing filtration (slide 38)
P-BS = Fluid pressure in Bowman’s space
‘pi’-GC = osmotic force due to protein in
plasma
What doess Glomerular filtration rate (GFR) show
How well the kidneys are functioning
What are the features of tubular reabsorption (slide 40)
1) The filtered loads are very high (e.g. water)
2) Reabsorption of waste products is incomplete (e.g. urea)
3) Reabsorption of useful components is complete (e.g. water and salts)
What is the mechanism for sodium and water reabsorption
1) 2) Sodium reabsorption is an active process
occurring in all tubular lumen (except the
descending limb of loop of Henle)
Water reabsorption is by osmosis and is
dependent on sodium reabsorption
Slide 43 - Aquaporin role
Directed reading - * Primary active sodium reabsorption
* Coupling of water reabsorption to Sodium reabsorption
* Urine concentration: The countercurrent multiplier system
* The medullary circulation
