Water Balance Pt 1 | Physiology 2 Final

What important concentration from kidney allows animals to avoid dehydration

urine concentration

What spp has the lowest urine osmolarity (mOsm/L), what is the value and urine/plasma conc

calf 500 mOsm/L → 2:1 urine/plasma conc ratio

In the medullary interstitium, water reabsorption occurs by what mechanism

osmosis

How does osmolality of tubular fluid gradually inc from the renal cortex to renal medulla

reabsorption of water by vasa recta and ion reabsorption creates a gradual inc osmolality in the interstitium from cortex to medulla

Which part of the nephron reabsorbs the most amount of water

PCT

What is the osmolality level of tubular fluid from bowman’s capsule to beginning of thin descending limb of Henle’s Loop (and why)

osmolality level of tubular fluid remains the same from BC to thin descending loop bc of equilibrium of interstitium and tubular fluid

What is the osmolality level of tubular fluid from thin descending limb of Henle’s Loop to ascending limbs (thick and thin)

Osmolality level of tubular fluid inc gradually until it is equal to interstitium (→ water is reabsorbed into medulla due to osmosis; low permeability to solutes)

Why is the osmolality level of tubular fluid gradually increasing from thin descending limb of Henle’s Loop to ascending limbs (thick and thin)

→ water is reabsorbed into medulla due to osmosis; low permeability to solutes in thin descending limb to ascending limb

What is the osmolality level of tubular fluid from ascending limbs (thick and thin) to late DT

gradual dec of osmolality level of tubular in thin ascending limb to thick ascending limb becoming diluted and falling to 100 mOSM/kg (→ ascending limbs impermeable to water but show a high NaCl reabsorption creating medullarly hypertonicity by increasing osmolality of interstitium.)

Why is the osmolality level of tubular fluid from ascending limbs (thick and thin) to late DT decreasing

→ ascending limbs impermeable to water but show a high NaCl reabsorption creating medullary hypertonicity by increasing osmolality of interstitium

What does osmolality of fluid depend on in the late DT and cortical collecting ducts

osmolality of fluid depends on level of ADH; therefore, if ADH is high water permeability is high

What contributes to the medullary hypertonicity of the collecting ducts as filtered urea is reabsorbed into blood

urea conc inc (by UT-A1/A3) in intersitititum contributing to medullary hypertonicity

How is urea recycled in Henle’ loop leading to medullary hypertonicity

urea is reabsorbed in IMCD (by UT-a1/3) to the interstitium causing medullary hypertonicity; the urea from the the interstitium goes into the vasa recta to be transported into thin limbs of Henle’s loop reaching CD for urea reabsorption/recycle

What part of the nephron creates an opposite flow

the sharp turn of the loop (thin ascending and descending)

Where can water only pass through in the henle’s loop

thin descending limbs

What are the three main characteristics of countercurrent multipler system of loop of henle that allows for inc/dec concentration

1. loop making a sharp turn (creating fluid flow in opposite direction)

2. water only passing in thin descending limbs

3. solutes are reabsorbed in ascending limbs w/o water generating an osmotic gradient

If ADH is present, CD is ___ permeable and determines the ___ of the excreted urine

water

osmolality

What determines the final osmolality of excreted urine

CD determines the osmolality of excreted urine

What occurs with CD water reabsorption and urine concentration in the presence of ADH

CD will be:

• permeable to water

• able to concentrate urine

What occurs with CD water reabsorption and urine concentration in the absence of ADH

CD will be:

• impermeable to water

• not be able to concentrate urine

Describe the pathway of vasopression/ADH attaching to CD tubular cells to initiate water reabsorption

1. AVP/ADH attaches to V2 receptor (ADH receptor) activating cAMP to protein kinase A

2. Protein kinase A initiates protein phosphorylation of assortment of AQP-2 in vesicles

3. transported to tubular lumen/apical membrane for H2O reabsorption

What occurs to tubular concentration when water is reabsorbed into the interstitium (and why)

inc of tubular concentration due to less dilution of fluid

When water reabsorption increases, what occurs to urine concentration — How does this affect dehydration of the animal

inc of urine concentration; allows for animals to retain water (preventing dehydration)

What are the three types of ADH receptors in the kidney

1. V1a

2. V1b

3. V2

What are the specific ADH receptors in glomerulus and renal medulla

V1a (in glomerulus and renal medulla)

What are the specific ADH receptors in inner medulla (thin limbs

V1b (in thin limbs)

What are the specific ADH receptors in mTAL, DCT, CD

V2 (in mTAL, DCT, CD)

What occurs to ADH and urine when osmolality in plasma is increased

ADH is released → inc conc of urine

When there is dehydration, an inc of extracellular osmolarity in the plasma occurs leading to what activation

activation of osmoreceptors (from hypothalamus)

What is the entire pathway of osmoreceptor-ADH feedback when there is dehydration and inc of osmolarity in plasma

1. dehydration → inc extracellular osmolarity

2. activation of osmoreceptors (from anterior hypothalamus)

3. ADH secretion (from posterior pituitary)

4. inc water permeability in CD

What are the purpose of AQP3/4 in the CD

transports water out of the CD cells at the basolateral membrane to avoid bursting

True or false: AQP3/4 are located at the basolateral membrane and are ADH sensitive to avoid bursting of the CD cells

false; AQP3/4 are located at the basolateral membrane and are not ADH sensitive to avoid bursting of the CD cells

What is micturition

process whereby the urinary bladder empties when it becomes filled

What monitors the progressive filling of the bladder

stretch-sensitive cells of the internal urethral sphincter

What sympathetic nerve innervates the inhibition of micturition

hypogastric n.

What parasympathetic nerve innervates the activation of micturition

pelvic n.

What somatic nerve controls continence

pudenal n.

When sympathetic nervous system is activated via hypogastric n., what are the actions of the detrusor muscel and inner urethral sphincter

• relaxation of detrusor muscle

• contraction of inner urethral sphincter

(→ inhibition of micturition)

When parasympathetic nervous system is activated via pelvic n., what are the actions of the detrusor muscle and inner urethral sphincter

• contraction of detrusor muscle

• relaxation of inner urethral sphincter

(→ activation of micturition)

When somatic nervous system is activated via pudenal n., what are the actions of the external urethral muscle

contraction of external urethral sphincter (→ continence)

Which nerve is important for somatic NS of micturition and the neurotransmitter and receptor associated with its action

pudendal n. - ACh on N receptors

Which nerve is important for parasympathetic NS of micturition and the neurotransmitter and receptor associated with its action

pelvic n. - ACh on M3 receptor

Which nerve is important for sympathetic NS of micturition and the neurotransmitter and receptor associated with its action

hypogastric n. - NE on B3 receptors

What are the three different results of activation of SNS, PSNS, Somatic NS of micturition of the bladder

• SNS → inhibition of micturition

• PSNS → activation of micturition

• Somatic → continence

What are the sequence of events of micturition

1. progressive filling of the bladder causes the bladder wall to stretch

2. when tension of internal urethral sphincter passes threshold, sensory signals reach the spinal cord to the micturition center (in pons) and thalamus

3. from thalamus, signals reach the cerebral cortex

4. parasympathetic activation of micturition reflex

   • pelvic n. contracts detrusor muscle and relaxes inner urethral sphincter

   • internal and external sphincter open and urine exits the body

An increase of intravesical pressure in bladder, causes what type of contractions

tonic contractions/micturition contractions similar to pregnancy contractions