4A
____ % of the plasma moves out of the glomerular capillaries into tubules
20
What are the two ways to cross the epithelial layer?
- para-cellular pathways
- epithelial (trans-cellular) transport
The deeper into the medulla you go the ______ it gets
saltier
At the proximal tubule ____ is reabsorbed
At the loop of Henle ____ is reabsorbed
70%; 20%
What is a hormone?
chemical messenger secreted into the blood by specialized cells
What is the renal corpuscle composed of?
Glomerulus and Bowman's Capsule
Explain the process of active transport of Na+ in the proximal tubule
- Na+ enters cells through various membrane proteins, moving down its electrochemical gradient
- Na+ pumped out the basolateral side of the cell by Na+/K+ ATPase
How does water cross cell membranes?
- leaks through the lipid bilayer
- travel through 'water channels' called aquaporins
What type of hormone is aldosterone and what it's alternative name?
- steroid hormone
- mineralocorticoid
Name the 4 features of typical hormones?
- secreted by a group of cells derived from epithelial tissue that form discrete glands
- secreted into the blood
- travels to distant targets
- acts at very low concentrations
What are the barriers to glomerular filtration?
1. Endothelium of glomerular capillaries
2. Basement membrane
3. Features of specialized epithelium (aka podocyte foot processes)
Explain the principles governing tubular reabsorption
1. Na+ is reabsorbed by active transport
2. Electrochemical gradient driven anion reabsorption
3. Water moves by osmosis, following solute reabsorption, concentrations of other solutes increase as fluid volume in the lumen decrease
4. Permeable solutes reabsorbed by diffusion through membrane transporters or by paracellular pathways
* movement is from tubule lumen to interstitial fluid
When you want to produce dilute urine what happens?
there is a reduction in the expression of aquaporins, causing less water to be reabsorbed
What stimulates renin release from granular cells of juxtaglomerular apparatus?
- granular (JG) cells themselves monitor blood pressure in afferent arterioles, and release renin in response to decreased BP
- paracrine feedback from macula densa cells in the distal tubule causes a decrease in flow rate and an increase in renin release
- sympathetic pathways originating in the cardiac control centre in the medulla terminate on granular cells (part of baroreceptor response to decrease BP)
What are the mechanisms for removing hormones from receptors?
- hormones in plasma are inactivated on their way through the liver/kidney
- non-specific proteases in ECF break them down
- hormones-receptor complex can be internalized by the target cell
Name three roles of the kidneys
- regulation of extracellular fluid volume and blood pressure
- regulates plasma osmolarity
- regulated ion balance
- regulated pH
- excretion of waste
- endocrine
Compounds that compete with drugs for ___________ will slow the transport of its other cargo out of the blood
OAT transporter
How does vasopressin affect the body?
- vasopressin binds to membrane receptors
- receptors activate cAMP second messages system
- cell inserts AQP2 water pores into the apical membrane
- water is absorbed by osmosis into the blood
* aquaporin molecules that are already synthesized are installed on the membrane
Where is atrial natri uretic peptide (ANP) produced and what does it do?
produced in specialized myocardial cells, mostly in atria and released when these atrial cells stretch more than normal
Explain the peptide hormone synthesis and secretion pathway.
1. Nascent preprohormone emerging from ribosome directed into ER lumen by signal sequence creating prohormone
2. Enzyme in ER remove signal sequence creating prohormone
3. Prohormone passes from ER through Golgi complex
4. Secretory vesicle containing enzymes and prohormone bud off Golgi. Enzymes cleave prohormone into one or more active peptides plus additional peptide fragments.
5. In response to the signal, secretory vesicles release contents by exocytosis into ECF
6. hormone moves into circulation for transport to its target
Explain the tubule glomerular feedback and autoregulation of GFR
1. GFR increases
2. increase in flow through tubules
3. increase in the flow of NaCl past macula densa
4. paracrine signals from macula densa acts on afferent arteriole
5. renal blood flow decreases
6. decrease in pH
7. Decrease in GFR
What is the formula for clearance? (with units)
clearance = excretion rate of X (mg/min) / [x] in plasma (mg/ml)
clearance should be in units of ml/min
What is the point of the loop of Henle?
- 25% of Na+ and K+ reabsorbed in the thick part of the ascending limb
- create a salt gradient for the collecting duct
- uses a countercurrent exchange system
When you have a decrease in volume and no change in osmolarity what does that cause?
+
When you have a decrease in volume and an increase in osmolarity what does that cause?
- Hemorrhage
- Dehydration
What is the club holding this event?
BUGS
Biology Undergraduate Society