Editing Normal Erectile Physiology (section)

== Answers ==

# Explain the physiology of an erection
#* In the flaccid state, the cavernous smooth muscle and the smooth muscles of the arteriolar and arterial wall are tonically contracted, allowing only a small amount of arterial flow into the corpora
#* Sexual stimulation triggers release of neurotransmitters from the cavernous nerve terminals. This release of neurotransmitters results in relaxation of these smooth muscles results in
#** Increased blood inflow
#** Decreased blood outflow
#** Increase in PO2 and intracavernous pressure
# Why does the corpus spongiosum not become as rigid as the corpora cavernosae?
#* The corpus spongiosum lacks the outer longitudinal layer of the tunica albuginea
# Describe the autonomic innervation and somatic involved in erection?
#* Parasympathetic (S2-S4): erection
#* Sympathetic (T10-T12): detumesence, emission
#* Somatic (S2-S4, Onuf nucleus): pudendal nerve is responsible for sensation and contraction of the ischiocavernosus and bulbocavernosus/bulbospongiosus muscles (and external urethral sphincter)
# What is the main neurotransmitter involved in erection? Where is it released from? What is its function? What enzyme synthesizes it? Which enzyme subtype is responsible for initiation vs. maintenance of erection?
#* Nitric oxide
#* Non-adrenergic, non-cholinergic nerve terminals and the endothelium
#* Stimulate production of cGMP by activation guanylate cyclase in smooth muscle; increased cGMP in smooth muscle stimulates relaxation
#* Nitric oxide synthase; nNOS for initiation, eNOS for maintenance
# What is the principal neurotransmitter involved in detumesence?
#* Norepinephrine
# Which phosphodiesterase subtypes are found in the corpus cavernosum? Which subtype is the main one mediating detumescence?
#* All except PDE6, which is exclusively in the photoreceptors of the eye
#* PDE5
# What are the phases of detumescence?
# What are the 3 types of erection? Which is most likely preserved on a patient with upper spinal cord injury?
#* Nocturnal, psychologic, and reflexogenic
#* Reflexogenic