RENAL Flashcards
What is the filtration unit of the nephron?
- Renal Corpuscle
What does the renal corpuscle comprise of?
- Glomerulus + Fluid filled bowmans capsule
What are the 3 processes involved in urine formation?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
What is the renal blood vessel arrangement?
- Arteriole–> Capillaries–> arterioles–> Venules
Do plasma proteins normally filter through the glomerulus?
NO! Too large
What is the difference between fluid in the plasma and bowman’s capsule?
- Bowmans capsule is free of protein
In general, which of the 3 processes in urine formation would be active when glucose enters?
- Filtration, COMPLETELY reabsorbed, NOT SECRETED
In general which of the 3 processes of urine formation would be active with many electrolytes (ions)?
- FIltration, SOME absorption and NO SECRETION
Which force drives filtration?
- Hydrostatic pressure and large finestrations (high permeability)
What are the 3 layers of the glomerular filtration barrier? (inside–> out)
- Single celled capillary endothelium (pores/finestrae)
- Non-cellular basement membrane
- Single celled epithelial lining of Bowmans capsule (podocytes and filtration slits)
What happens to the filtrations between endothelial cells in kidney failure?
- Become clogged, so can’t filter well (also in diabetes)
Are waste products well absorbed?
-No!
Are ions well absorbed?
- YES! Important to the body
How much filtrate is taken back into body?
- 99%
What is the equation for excretion?
- Excretion=Filtrate- (re absorption + Secretion)
Is glucose 100% reabsorbed normally?
- YES!
Is sodium or water reabsorbed more in general? -
- Sodium (99.5%) compared to H20 (99%)
What is GFR?
- Glomerular filtration rate
- Volume of filtrate formed from kidney each minute (ml/min)
What is the normal GFR?
- 125ml/min (180L/day)
What would happen without tubular reabsoprtion?
- Whole plasma volume (3L) and essential solutes would be excreted within 30MINS
What would happen in the body if GF continued normally, but tubular reabsorption decreased to 50% of normal rate?
Excretion would increase
In tubular reabsoprtion, which two pathways can solutes take?
- Transcellular (through cells)
- Paracellular (through tight junctions)
What is the transcellular pathway for tubular reabsorption?
- Luminal membrane –> cytosol—> Basolateral membrane –> interstitial fluid–> Endothelial cells–> Plasma of peritubular capillareis
Is reabsorption of H20 secondary to Na+?
YES! Most of energy goes into reabsorbing sodium
Where is almost all water and sodium reabsorbed?
- Proximal tubule
What happens if all the protein carriers are saturated with reabsoprtion?
- There is more excretion of the substance (bc. they are saturated)-excess will be excreted
What is the transport maximum?
- (Tm- mg/min)
- Maximum rate that solute can be transported to peritubular capillaries
What is the filtration rate of glucose proportional to?
- Plasma concentration of glucose - until Tm is reached
What is glucosuria and what is it due to?
- Presence of glucose in urine
- Due to excess plasma glucose concentration– Tm reached so it is excreted in urine (diabetes)
- 300mg/100ml
What is poyluria?
- Excessive volume of urine
What is oliguria?
- Small volume of urine
What does renal control of body water and Na+ determine?
- Extracellular (plasma aswell) fluid volume and osmolarity
What does most renal energy go towards?
- Na+ absorption
What would happen to our body (in general) if we only absorbed water (not Na+)?
- Eventually, water would enter the cells and they would burst
Where is the majority of water reabsorbed?
- In the proximal tubules (osmosis)-67% reabsorbed
What is a H2O diuresis?
- the process of removing excess H2O to correct plasma hyposmolarity
In general, if you drank 1L of water, what effect would it have on various body fluids? (Total body H2O, ECF vol, ECF plasma osmolarity, ICF vol, ICF osmolarity, cells)?
TOTAL BODY H2O: Increase ECF FLUID VOLUME: Increase ECF PLASMA OSMOLARITY: Decrease ICF OSMOLARITY: Decrease CELLS SWOLLEN OR SHRUNK: Swollen
Which structure detects changes in plasma osmolarity?
- Posterior pituitary secretes ADH
- Paraventricular nucleus and supraoptic nucleus (contain osmoreceptors)
- receptors change firing rate and so changes in ADH secretion
Is there ADH secretion with normal plasma osmolarity?
Small secretion
What type of ADH secretion is occurring in a low plasma osmolarity ?
- Swollen cell
- very little ADH secretion (neglibable )
What type of ADH secretion is occurring for high plasma osmolarity?
- HIGH adh secretion
- Cells will be shrunken so want to retain water (AP firing rate INCREASES—> ADH secretion increases)
Which anatomical part is reabsorption (ADH secretion) focused on?
- ONLY THE DISTAL TUBULES AND COLLECTING DUCTS
- 9% REMAINING that is filtered
Is there a 24hr cycle of ADH secretion in body?
- YES!
- Adults have increased secretion overnight
What happens to the following body fluids in a state of dehydration?
- TOTAL body H20
- ECF volume
- ECF osmolarity
- ICF volume
- ICF osmolarity
- CELLS
1. DECREASE 2 DECREASE 3. INCREASE 4. DECREASE 5. INCREASE 6. SHRUNKEN
How does the body act to bring body levels back to normal following dehydration?
- INCREASED OSMOLARITY (ECF)
- Osmoreceptors SHRINK and firing rate DECREASES
- Increased ADH secretion (from post pituitary nerve terminals)
- Water reabsorption will INCREASE
- Water excretion will DECREASE
- So total body water and ECF osmolarity will go back to normal
What is diabetes insipidus and what are the two forms of it?
Hypothalmic disorder
- ADH/vasopressin defificiency (or can’t repsond to ADH)
- No elevated plasma glucose (has nothing to do with it)
- DILUTE URINE
1. Central
2. Nephrogenic
What is central diabetes insipidus?
- Failure of the posterior pituitary to secrete ADH (lack of the hormone)
What is nephrogenic diabetes insipidus?
- The kidney can’t respond to ADH due to pathology (like a tumor) –> ADH receptors on renal tubular cells not responding
Do significant changes in blood cause a change in ADH secretion?
- yes!
How does blood volume affect MAP?
- By affecting venous pressure (changes of volume of blood in veins)
What is the general pathway for an increase in blood volume?
- Firing rate of arterial and pulmonary stretch receptors + arterial baroreceptors INCREASES
- INCREASE in neuronal impulses (cranial nerves) –> hypothalmic osmoreceptors
- INHIBITION of hypothalmic synthesis and posteriour pituitary release of ADH
- INCREASE in flow of dilute urine
What is the rough pathway for a decrease in blood volume (MAP)?
- Decrease in firing rate (atrial and pulmonary stretch recpetors and arterial cardiac and carotid) barareceptors
- Decrease in neuronal impulses via cranal nerves –> hypothalmic osmoreceptors
- Underestrained MASSIVE SYNTHESIS and posterior pit. release of ADH (acts on aquaporins and collectign ducts)
- Water retention occurs and urinary `excretion lowers
What two things is thirst triggered by?
- Dehydration (Decrease in ECF volume + increase in plasma osmolarity)
- Blood plasma volume decreasing
What roughly happens to trigger thirst through (1) dehydration?
- osmoreceptors SHRINK–> signal to cerebral cortex–> sensation of thirst–> reflex (neuronal pathways) and drop in salivary secretion–> DRY MOUTH AND THROAT
(SENSITIVE- DETECTS 1-2% CHANGES IN OSMOLARITY)
What roughly happens to trigger thirst through blood plasma volume decreasing?
- Stimulation of volume sretch sensitive receptors (baroreceptors/cardiopulmonary receptrs) –> stimulation of thirst centres in hypothalamus–> sensation of thirst
(LESS SENSITIVE 10-15 % CHANGES)
Which drugs alter ADH secretion?
- CAFFINE AND ETHANOL(mild diuretcis–> inhibit ADH)
- DIURETICS (water diuresis)–> e.g. shane warne to wash drugs out of system
- ECSTACY –> stimulates ADH release –> dilutional hyponatremia
What is the hormone Aldosterone involved in?
- Regulating total Na+ levels
When do we have the highest ADH levels?
- Decreased blood volume associated with increased plasma osmolarity
When ingesting NA+ tablets (chewing and swallowing), What happens to the ECF volume and osmolarity?
- Volume stays the same
- ECF osmolarity INCREASES
What happens if you have a net retention of NA+?
- INcrease in ECF plasma volume (so increases CVS pressures) and MAP
What are Na+ and H2O intake controlled by?
- H20 intake and salt apeptite
What are Na+ and H2O OUTPUTS controlled by?
- Under influence of kidney (kidney regulating amount of Na+ and H2O in urine)
Can the kideny corect for inadequate dietary Na+ and H20?
- NO
What does diuresis mean?
- Excretion of h2O in urine (pure)
What is naturesis?
- Excretion of Na+ in urine
Are there direct Na+ receptors to sense changes in the body?
- NO!
How does the body sense changes in Na+ levels (what detects the changes) ?
- Indirectly senses changes in total body sodium via changes in PLASMA VOLUME
- detected by CVS stretch sensitive and baroreceptros (atria, veins, arterioles)
+ Renal sensors (intrarenal baroreceptors, in the distal tubules -macula densa cells)
How does the body adjust Na+ levels?
- Adjusting the Na+ excreted (urine) by CHANGING GLOMERULAR FILTRATION RATE (GFR)
What is the equation for Na+ excreted?
- Na+ excreted= Na+ filtered - Na+ absorbed (GFR adjusted)
Where is aldosterone secreted from?
- Adrenal glands
What type of hormenoe is alsosterone?
- Steroid hormone (mineral corticoid)
What is the most important controller for Na+ reabsoprton?
- Aldosterone
Where in the adrenal gland is aldosterone secreted?
- Zona glomerular cells
How can the amount of Na+ absorbed in the distal tubules of kidney be finetuned and regulated?
- By varying the plasma aldosterone concentration
With aldosterone entering cell and binding to mineral corticoid receptor to initiate protein synthesis, which proteins are involved?
- P1: Na+ protein channel made
- P2: ATPase Na+/K+ pump protein
P3: ATP formation
P4: K+ channel
Roughly how many days does it take to get rid of sodium load in body?
-6-8 days
What does binging on salty chips initially lead to?
- Sodium retention initially (then water retention)–> ECF volume increase
- Na+ channels & ATPase (etc.P1 P2 P3…) get retrieved from collecting ducts of late distal tubules
- Become IMPERMEABLE to sodium
- Decrease in reabsorption of collecting ducts and Na+
- So INCREASE in excretion of Na+ in urine
How long after ingesting water is the output the highest (to get rid of excess water)?
- After 60mins
- pre formed aquaporins
- ADH causes aquaporins to get inserted into luminal membrane (rapid)
What happens with not enough aldosterone production?
- Addinsons disease
- BP decreases
- Salt cravings and muscle weakness
What is the proper name for salt cravings in a disease?
hyponatremia (low Na+ plasma concentration)
What is the proper name for muscle weakness in disease with electrolyte imbalance?
- Hyperkalemia (high plasma potassium concentration)
What happens with TOO MUCH aldosterone in the body?
- BP increases
- Leads to hypernatremia (high plasma sodium conc.)
- Leads to Hypokalemia (low plasma K+ conc
What does the ACE enzyme do, and what does that allow for?
Converts inactive Angiotensin I –> active Angiotensin II
- This then acts on adrenal cortex to secrete ALDOSTERONE
- this increases tubular Na+ reabsorption
- also acts on blood vessels (constricts vessels)
- Acts on posterior pituitary to secrete ADH
- Leads to INCREASED RETENTION OF WATER AND Na+
When is the ACE enzyme recruited?
- Decreased in perfusion of kidneys (BP lowers, decreased flow into kidneys
What are ACE inhibitors used to treat?
Hypertension (HIGH BP)
What is the rate limiting step in formation of Angiotensin II?
- Level of Renin secreted (in plasma)
What does the activation of the Renin-Angiotensin do?
- INCREASED Na+ (tubular) reabsorption
- DECREASED Na+ (urinary) excretion
What happens when body is lacking in Na+?
- Increase renin conc. in plasma
- Increase plasma angiotensin II
- Increase aldosterone
What causes renin to be secreted?
- Stored, synthesised and released by gruanular cells in juxtaglomerular region (afferent renal arteriole–> although some are on efferent arteriole)
What are 3 ways to increase secretion of renin?
- Decrease renal arterial pressure (intrarenal baroreceptors)
- Decrease luminal Na+ concentration passing macula densa
- Increase renal sympathetic nerve activity
What does a decrease in plasma volume lead to for renal arterial pressure (increasing renin secretion)?
- Decrease in renal arterial pressure
- This DECREASES the stretch in the juxtaglomerular cells (decreased intracellular calcium)
- So increased renin secretion (1)
What does an increase in plasma volume cause for the renal arterial pressure (decreasing renin secretion)?
- Increase in renal arterial pressure
- Increase in stretch of juxtaglomerular cells (increase in Ca2+) intracellular concentration
- Decrease in renin secretion
For INCREASED luminal Na+ passing through the macula densa cells is there an increase or decrease in renin secretion?
- Decrease in renin secretion
For DECREASED luminal Na+ passing through macula densa cells is there an increase or decrease in renin secretion?
- INCREASE in renin secretion (2)
What happens to the renal sympathetic nerve activity for decreased body Na+?
- Low plasma volume and low blood pressure (RSNA increases)
- JUXTAGLOMERULAR Beta receptors are activated
- Act to increase renin secretion (3)
What is ANP?
- Atrial Naturetic Peptide
- With increased Na+ –> increased plas. vol.–> increased atrial filling (stretch) –> secretion of ANP hormone
- ACTS TO INCREASE NATURESIS (URINARY EXCRETION OF Na+)
What are 3 ways that ANP lowers BP?
- (Increasing Na secretion-naturesis)
1. Acts on collecting ducts by decreasing Na+ reabsorption
2. Indirectly INHIBITS renin secretion (–> aldosterone secretion) and indriectly decreases this effect
3. Dilation of afferent and constriction of efferent arteriole - Increases the GFR (and pressure) + filtered load of Na+–> leads to INCREASED EXCRETION of Na+
