npb101 renal system

kidneys receive ___-most of the body's entire cardiac output

2nd

the kidneys convert _____ ____ to urine

blood plasma

the kidneys maintain the blood's ____ balance

ion

the bladder is controlled by _____ muscle

smooth

renal cortex vs. renal medulla

Renal cortex: outer part of the inside of the kidney
- blood vessels located here

Renal medulla: inside part of the inside of kidney
- conc. of urine is regulated here

what is the smallest functional unit of the kidney?

the nephron

what are the 2 components of the nephron?

vascular and tubular

what are the 2 types of nephrons, and which type is more abundant in the kidney?

cortical and juxtamedullary
cortical is more abundant (80%)

cortical glomeruli lie in the (inner/outer) cortex layer

outer

juxtamedullary glomeruli lie in the (inner/outer) cortex layer

inner

the afferent arteriole carries blood to the ____

glomerulus

where does filtrate production begin?

glomerulus

the efferent arteriole carries blood from the ____

glomerulus

supply the renal tissue, involved in exchanges with fluid in tubular lumen

peritubular capillaries

components of vascular nephron

- afferent arteriole
- glomerulus
- efferent arteriole
- peritubular capillaries

ball of capillaries where filtrate production begins

glomerulus

components of tubular nephron

- bowman's capsule
- proximal tubule
- loop of henle
- distal tube and collecting duct

collects glomerular filtrate

bowman's capsule

uncontrolled reabsorption and secretion of selected substances occur here

proximal tubule

structure that establishes osmotic gradient in renal medulla that's important in the kidney's ability to produce urine of varying concentration

loop of henle

variable, controlled reabsorption of Na+ and H2O/secretion of K+ and H+ occur here

distal tube and collecting duct

what structure is the combined vascular and tubular component of the nephron?

juxtaglomerular apparatus

this nephron structure facilitates the exchange of info and adjusts how much filtrate is produced, produces substances involved in control of kidney function, and is the region where the ascending loop of henle passes through

juxtaglomerular apparatus

what are the 3 basic renal processes of urine formation in order, and in what direction does urine flow for each of them?

glomerular filtration - glomerulus to bowman's capsule
tubular reabsorption - tubular lumen to peritubular capillaries
tubular secretion - peritubular capillaries to tubular lumen

of the 3 urine formation processes, which are selective and which are nonselective?

glomerular filtration - nonselective
tubular reabsorption and secretion - selective

what substances are not filtered out through glomerular filtration? (i.e. they stay in our bodies)

cells (e.g. RBCs) and proteins

how many layers must filtrate pass through during glomerular filtration, and what are those layers?

1. pores within endothelial cells of glomerular capillary
2. basement membrane (negative charge prevents protein leak)
3. filtration slits in inner layer of bowman's capsule

purpose of podocyte foot process

contains/controls glomerular filtrate rate

if bp increases, (more/less) plasma is filtered out

more

if bp decreases, (more/less) plasma is filtered out

less

what happens if the bp = 0?

filtrate production stops, leading to eventual kidney failure

what are the 3 pressures that affect glomerular filtration rate?

- glomerular capillary blood pressure
- plasma-colloid osmotic pressure
- bowman's capsule hydrostatic pressure

of the 3 GFR pressures, which favor/oppose filtration?

- glomerular capillary bp: favors
- plasma-colloid osmotic pressure: opposes
- bowman's capsule hydrostatic pressure: opposes

of the 3 GFR pressures, which are constant and which can be changed?

glomerular capillary bp can be changed, the other 2 stay constant

t/f: glomerular capillary bp controls GFR since the other 2 pressures don't change

t

what causes plasma-colloid osmotic pressure?

the unequal distribution of protein between plasma and glomerular filtrate

what causes bowman's capsule hydrostatic pressure?

fluid pressure by filtrate in bowman's capsule

net filtration pressure normally (favors/opposes) filtration

favors

in addition to net filtration pressure, what are the other determinants of GFR?

- glomerular surface areas available for penetration
- permeability of glomerular membrane

what are the 2 controlled adjustment methods of GFR?

autoregulation and extrinsic sympathetic control

what happens to GFR during vasoconstriction?

GFR decreases

local response within arteriolar smooth muscle wall to stretch

myogenic autoregulation

adjustments to afferent arteriolar pressure in response to salt concentration in loop of henle

tubuloglomerular feedback

how does autoregulation maintain a constant GFR across a large BP range (e.g. during exercise, stress, disease, etc.)

macula densa cells detect increased GFR and salt delivery to distal tubules (due to high BP) -> GFR decreases -> prevents unnecessary loss of water/salts to urine during exercise

autoregulation and extrinsic sympathetic control both use the same mechanism of:

changing the diameter of the afferent arteriole (vasoconstriction/vasodilation)

how would kidney stones affect GFR?

GFR would decrease because of an increase in the hydrostatic pressure in Bowman's capsule

tubular epithelium vs. capillary epithelium

tubular epithelium:
- has luminal and basolateral membrane
- forms tight junctions with adjacent tubular cells
- permeability varies along length of tubule, subject to hormonal control
capillary epithelium:
- no tight junctions between cells
- more permeable

trans epithelial transport requires that a substance pass through which 5 barriers in order?

1. luminal membrane of tubular cell
2. cytosol of tubular cell
3. basolateral membrane of tubular cell
4. interstitial fluid
5. capillary wall

describe the 2 types of tubular reabsorption

passive: movement down osmotic/electrochemical gradient (H2O)
active: requires energy (sodium, glucose, amino acids, electrolytes)

t/f: during tubular reabsorption, almost all of sodium is reabsorbed

t

where in the nephron is sodium reabsorbed? List their percentages and the function of sodium reabsorption in each region.

67% in proximal tubule - reabsorption of glucose, amino acids, water, chloride, urea
25% in loop of henle - ability to produce urine of varying concentrations/volumes, sets up concentration gradient
8% in distal and collecting tubes - regulation of ECF volume, subject to hormonal control

how does aldosterone stimulate sodium reabsorption?

by inserting additional leak channels in the luminal membrane, and additional Na/K ATPase pumps in the basolateral membrane

intracellular sodium concentration is (high/low), while interstitial sodium concentration is (high/low)

low, high

what protein facilitates the movement of H2O down its concentration gradient?

aquaporin

describe the 2 types of aquaporins

aqp1 - always open, found in proximal tubules
aqp2 - regulated by vasopressin, expressed by distal/collecting tubes

t/f: because urea is small in size, its diffusion/reabsorption is not very effective, so half of urea in the filtrate is still excreted

t

what are the 6 key substances of the raas system (in order)?

angiotensinogen, renin, angiotensin 1, ACE, angiotensin 2, aldosterone

angiotensinogen is made in the

liver

renin is released from the

kidneys

ACE is an enzyme present in the

lungs

aldosterone is released by the

adrenal cortex

renin role

converts angiotensinogen to angiotensin I

ACE role

converts angiotensin 1 to angiotensin 2

angiotensin 2 roles (4)

stimulates vasopressin, thirst, vasoconstriction, stimulates adrenal cortex to release aldosterone

aldosterone role

increases sodium reabsorption by inserting additional sodium channels and pumps

what is the ultimate purpose of the RAAS system?

to reabsorb sodium and water to restore normal values of ions, water, pressure, etc. in the body

what is the connection between hypertension and RAAS activity?

hypertension is caused by an abnormal increase in RAAS activity

what conditions stimulate the RAAS system?

low sodium, ECF volume, and arterial bp

what inhibits sodium reaborption/RAAS?

ANP and BNP (natriuretic peptides)

glucose and amino acids are (actively/passively) reabsorbed in the proximal tubule via ____

actively, sodium-dependent hsymport carriers (e.g. SGLT)

t/f: the number of SGLTs is finite, which results in a tubular maximum

t

what is the renal threshold?

300 mg/100 mL

what is the tubular maximum?

400 mg/min

describe healthy tubular reabsorption conditions of glucose

all glucose is reabsorbed, none secreted

hydrogen ions can be secreted/reabsorbed by special ____ ____ in distal/collecting tubes

intercalated cells

long loops of henle _____ the vertical osmotic gradient (VOG)
vasa recta ____ VOG
collecting tubules ____ VOG

establish, preserve, use

in what direction does K+ move during tubular secretion?

into the lumen, opposite of Na+'s direction

high plasma K+ concentration stimulates:

aldosterone from adrenal cortex

t/f: almost all K+ in urine is a result of tubular secretion

t

ECF osmolarity value

300 mOsm/L

hypotonic vs. hypertonic in terms of urine concentration

hypotonic: water excess, dilute urine
hypertonic: water lack, concentrated urine

what is the process that establishes the VOG in loop of henle?

countercurrent multiplication

isotonic osmolarity

renal cortex

filtrate after passing through the loop of henle is (concentrated/dilute)

dilute

limb that is: impermeable to sodium, highly permeable to water

descending

limb that is: actively transporting sodium into the interstitial fluid, always impermeable to water

ascending

maximum concentration in medulla

1200 mOsm/L

draw the descending and ascending loops of henle and label the following:
- cortex and medulla
- varying concentrations (e.g. 100, 300, 1200)
- movement of water and sodium in the respective limbs

.

countercurrent multiplication maintains a difference of ___ mOsm/L at every "level"

200

vasopressin

stimulated during water deficit, inserts aqp2 in luminal membrane to produce a small volume of concentrated urine, thus conserving water

how does excess alcohol consumption affect vasopressin?

vasopressin is inhibited, leading to dehydration and excess urine output

vasa recta purpose

preserves VOG while supplying blood to medulla

micturition

process of emptying the bladder from kidneys -> uterus -> bladder

what prevents back flow of urine?

increased pressure against ureters as the bladder fills

what 2 sphincters prevent the bladder from emptying continuously? differentiate the 2 in terms of type of muscle, voluntary/involuntary

internal urethral sphincter: smooth muscle, involuntary
external urethral sphincter: skeletal muscle, voluntary

internal urethral sphincter:
when the bladder relaxes -> ____
when the bladder contracts -> ____

sphincter closes, sphincter opens

t/f: the external urethral sphincter's motor neurons continuously fire and keep the sphincter closed unless the neurons are inhibited

t

initiated when stretch receptors in the bladder wall stimulate parasympathetic supply to the bladder, inhibiting the bladder's motor neurons

micturition reflex

how can you prevent the micturition reflex?

by deliberately tightening the external sphincter