Urological physiology

Question 1

Urinary STORAGE: detrusor

a) Action
b) Receptors
c) Pharmacology

Answer 1

a) Detrusor relaxes to allow filling
b) Sympathetic nervous system (beta-3-receptor).
c) Hence, B3-receptor agonist (mirabegron) is used to treat overactive bladder/urge incontinence

Question 2

Urinary STORAGE: bladder neck (IUS)

a) Action
b) Receptors
c) Pharmacology

Answer 2

a) Bladder neck constricts to prevent voiding:
b) Sympathetic nervous system (alpha-1-receptor).
c) Hence, alpha-blockers (e.g. tamsulosin, doxasozin) used to relax bladder neck in BPH and mitigate LUTS/ retention

Question 3

Urinary STORAGE: external urethral sphincter (EUS)

a) Action
b) Nerve

Answer 3

a) Contraction of striated muscle
b) Pudendal S2 - S4 (somatic control)
c)

Question 4

Urine voiding: explained

Answer 4

• Pontine micturition centre signals to sacral nerves
• Parasympathetic stimulation for detrusor contraction
• EUS relaxes (voluntary)

Question 5

Urine voiding: pharmacology

a) Bladder receptor
b) Drug class, examples
c) Side effects of these drugs

Answer 5

a) Muscarinic (M3) receptor , parasympathetic (ACh)
b) Antimuscarinics (e.g. oxybutynin, solifenacin, tolterodine) used for urinary frequency, urgency, enuresis and urge incontinence.
c) Can’t see (xerophthalmia), can’t pee (retention), can’t spit (xerostomia), can’t shit (constipation)