Urinary 8

Question 1

What organs/structures are involved in micturition?

Also make note of the differences between male and female physiology

Answer 1

Kidneys

Ureters

Bladder/Detrusor muscle

Intenal sphincter (male only)

External sphincter (within the urogenital diaphragm)

Urethra (shorter in females)

Question 2

What are the receptors involved in micturition and where is each found?

Give the ligand for each

What class of receptors do all of these belong to?

Answer 2

Bladder:

M3 Muscarinic receptor - Ach

Beta 3 Adrenergic receptor - Noradrenaline

Internal sphincter:

Alpha 1 Adrenergic receptor - Noradrenaline

External sphincter:

Nicotinic receptor - Ach

All GPCRs

Question 3

Describe the afferent nerves affecting micturition, list their receptors, where they affect and the effect they have

Answer 3

Pelvic nerve:

From Sacral region of spinal cord

Parasympathetic nerve

Activates M3 receptors in the bladder muscle

Causes contraction of the detrusor muscle

Pudendal nerve:

From Sacral region of spinal cord

Somatic nerve (under voluntary control)

Synpases with Nicotinic receptors on the external sphincter

Causes contraction of the external sphincter

Hypogastric nerve:

Thoracolumbar outflow

Sympathetic nerve

Synapses at ganglion then at B3 receptors on the bladder and A1 receptors on the internal sphincter

Causes relaxation of detrustor muscle (action on B3 receptors)

Causes contraction of internal sphincter (action on A1 receptors)

Question 4

What is the afferent nerve of the baldder?

Answer 4

Afferent Pelvic nerve

Originates in detrusor muscle

Stimuated when bladder is stretch, signifying the need for urination

Question 5

From where is micturition controlled?

Answer 5

The micturition centre in the Pons

Pons is a section of the brainstem