Countercurrent Exchange & Micturition

Countercurrent Exchange

• flowing in opposite directions

• filtrate going in one direction, blood vessel goes in opposite direction

Why does the body use countercurrent exchange?

allows for the greatest exchange of solutes

Vasa Recta

blood vessel in the nephron

Micturition

act of urinating

Pontine Micturition Center (PMC)

• causes detrusor muscle to contract and sphincters to open

• located in the pons

• when bladder fills with enough urine, sends a signal to PMC, sensation to pee

Detrusor muscle

when bladder fills, detrusor muscle is stretched

when squeezed, causes sphincters to open

What are the two sphincters?

internal sphincter and external sphincter (skeletal)

Prefrontal Cortex

• located in the frontal lobe

• can override PMS if its not the appropriate place to urinate since the external sphincter is under voluntary control

• can stop urination mid stream

Limbic System

can override the prefrontal cortex, resulting in urination linked to emotions (excited or scared)