Bladder

Question 1

Describe the neural innervation/components of the bladder

Answer 1

Sympathetic nervous system:

• inhibits micturition
• stimulates relaxation of the detrusor muscle (B3), and contraction of the internal urethral sphincter (alpha receptors)
• innervation of the B3 receptors on the detrusor muscle and the alpha receptors on the internal urethral sphincter come via the hypogastric plexus

Somatic nervous system:

• stimulates contraction of the external urethral sphincter
• innervation comes from the pudendal nerve. ACh is released onto nicotinic receptor.

Parasympathetic nervous system:

• stimulated contraction of the detrusor muscle. Release of ACh on the M3 muscarinic receptors on the detrusor muscle. Contraction of the detrusor muscle increases the intravesical pressure which allows urination to occur. Also get relaxation of the internal urethral sphincter through decreased SNS activity.