the RAAS, CKD, micturition control

Explain how the Na reabsorption affects H2O reabsorption

• High [Na] = no reabsorption = excess Na secreted in unripe

• Low [Na] = Na reabsorption

  • Na and Cl affect ECF volume = affects blood pressure

What is the juxtamedullary apparatus and where is it found

• Where the distal tubes passes through the fork formed by the afferents and efferent arteriole

• Granular cells secrete RENIN

How is renin secreted

• Secreted by granular cells

• Intracellular Baroreceptors detect changes in blood pressure

  • If blood pressure decreases they secrete more renin

• They are innervated by the sympathetic nervous system

  1. B.p decreases

  2. Sympathetic activity increases

  3. Smooth muscle granular cells secrete more RENIN

• The macular dense sense Na and Cl passing through the distal tubule

  • If Na and Cl in the urine decrease, the macula densa stimulates granular cells to secrete more renin

How does aldosterone increase Na absorption

1. Insertion of additional Na channels in the luminal membrane of tubular cells

2. Increases absorption

   • Cl follows passively to re-establish equilibrium

3. Insertion of additional Na/K-ATPase = pumps Na into interstitial fluid

   • K is pumped into distal/tubular cells

4. Na and Cl diffuse into blood stream

   • H2O follows movement to establish isotonicity

   • Increases ECF

Describe some symptoms of chronic kidney disease

• Anorexia and nausea

  • Accumulation of metabolic waste

• Anemia

  • Decrease in erythropoietin

• Hypertension and oedema

  • RAA system activation

  • Increase plasma volume = H2O can’t be eliminated

• Weakened muscle and bones

  • Calcium and other mineral imbalance

• Uremic encephalopathy

  • Accumulation of urea and nitrogenous waste = delirium and seizures

• Dehydration and thirst

• Electrolyte imbalance

• Acid base disturbances

How to treat chronic kidney disease

• Kidney transplants

• Dialysis

  • Haemodialysis

  • Peritoneal dialysis

Describe how haemodialysis works

• Blood is pumped from body into dialysing machine

• In the machine blood flows through the dialyser

• Dialysing solution is low in solute concentration

  • Flows in opposite direction

  • Solute leaves blood and enters dialysing solution via diffusion

Describe how peritoneal dialysis works

• Uses the patient’s pwn peritoneal membrane as a natural filter

• A catheter is implanted in the abdomen

• A dialysate solution is infused into the peritoneal cavity

• Waste and excess fluid diffuse from the blood stream [across the peritoneal membrane] into the dialysate

Describe the process of urination via reflex control

1. As bladder fills up stretch receptors in the bladder wall are activated

   • Send nerve impulses to the spinal cord

2. Spinal cord triggers a micturition reflex - via the parasympathetic nerve

   • Reflex causes relaxation of the internal sphincter

3. If the external sphincter is also relaxed, urination occurs

Describe the process of urination via voluntary control

1. Signals from the cerebral cortex override the micturition reflex

   • Can voluntarily contracts the external sphincter

   • Prevents urination even when the reflex is triggered

2. When we decide to urinate, the cerebral cortex sends signals to relax the external sphincter

   • Bladder contracts and urination occurs