Week 6: Pelvic Innervation

Question 1

Sympathetic preganglionic neurons

Answer 1

T10-T12 (lesser and least splanchnic nerves)

L1-L2 (lumbar splanchnic nerves)

Question 2

sympathetic ganglia

Answer 2

pelvic ganglia

Question 3

sympathetic postganglionic neurons

Answer 3

hypogastric plexus

Question 4

effects of sympathetic innervation in pelvis

Answer 4

• vasoconstriction
• relaxation of smooth bladder
• contraction of smooth muscle of internal urethral sphincter and internal anal sphincter
• contraction of smooth muscle of reproductive tract
• ejaculation

Question 5

Parasympathetic preganglionic neurons

Answer 5

S2-S4 (pelvic splanchnic nerves)

Question 6

parasympathetic ganglia

Answer 6

located in wall of organ

Question 7

effects of parasympathetic innervation in pelvis

Answer 7

• vasodilation
• contraction of bladder smooth muscle
• relaxation of smooth muscle of internal anal sphincter
• modulate activity of enteric nerves to increase peristalsis of distal colon and rectum
• erection

Question 8

visceral afferents conveying unconscious reflex sensation or pain sensations from viscera INFERIOR to the pelvic pain line (plus distal sigmoid colon and rectum)

Answer 8

follow the course of parasympathetic fibers to spinal sensory ganglia of S2-S4

Question 9

visceral afferents conveying unconscious reflex sensation or pain sensations from viscera superior to the pelvic pain line (excluding distal sigmoid colon and rectum)

Answer 9

follow the sympathetic fibers to the inferior thoracic and superior lumbar spinal ganglia

Question 10

skin and skeletal muscles of pelvis innervated by

Answer 10

ventral rami of lumbosacral (L4-S4) and coccygeal spinal nerves, which form plexuses of the same name

Question 11

smooth muscle and glands of pelvic viscera are innervated by

Answer 11

pelvic splanchnic nerves (S2-S4, parasympathetic) and lumbar and sacral splanchnic nerves (T10-12 and L1-L2, sympathetic)

Question 12

visceral afferents from intraperitoneal pelvic viscera

Answer 12

(eg uterine contractions) travel via hypogastric nerves to the aortic plexus and lumbar splanchnic nerves (sympathetic)

Question 13

visceral afferents from subperitoneal pelvic viscera

Answer 13

(eg cervical dilation and upper vagina) travel via pelvic splanchnic nerves to S2-S4 (parasympathetics)

Question 14

Afferent fibers from the lower vagina and perineum

Answer 14

travel via the pudendal nerves to S2-S4

Question 15

Female sympathetic pathway to innervate ovary

Answer 15

Thoracic splanchnic nerves (T10-T12, lesser and least) and lumbar splanchnic nerves (L1-L2) -> aorticorenal ganglia -> ovarian plexus -> ovary

Question 16

Female sympathetic pathway to innervate uterus, vagina, clitoris, bulb of vestibule, and fallopian tube

Answer 16

Thoracic splanchnic nerves (T10-T12, lesser and least) and lumbar splanchnic nerves (L1-L2) -> pelvic ganglia -> hypogastric plexus -> uterus, vagina, clitoris, bulb of vestibule, and fallopian tube

Question 17

Female parasympathetic pathway to innervate uterus, vagina, clitoris, bulb of vestibule, and fallopian tube

Answer 17

pelvic splanchnic nerves (S2-S4) via hypogastric plexus

Question 18

Male sympathetic pathway to innervate testis and epididymis

Answer 18

Thoracic splanchnic nerves (T10-T12, lesser and least) and lumbar splanchnic nerves (L1-L2) -> aorticorenal ganglia -> testicular plexus -> testis and epididymis

Question 19

Male sympathetic pathway to innervate prostate, penis, vas deferens, and seminal vesicles

Answer 19

Thoracic splanchnic nerves (T10-T12, lesser and least) and lumbar splanchnic nerves (L1-L2) -> pelvic ganglia -> hypogastric plexus -> prostate, penis, vas deferens, and seminal vesicles

Question 20

male parasympathetic pathway to innervate prostate, penis, vas deferens, and seminal vesicles

Answer 20

pelvic splanchnic (S2-S4) via hypogastric plexus

Question 21

Micturition (urination/voiding) is regulated by

Answer 21

an autonomic spinal cord reflex: the micturition reflex

Question 22

sympathetic pathway of innervation of bladder

Answer 22

lumbar and sacral splanchnic nerves -> inferior hypogastric plexus -> filling of bladder

Question 23

in bladder, hypogastric nerves cause

Answer 23

relaxation of detrusor muscle and contraction of the internal urethral sphincter to allow bladder filling

Question 24

parasympathetic pathway of innervation of bladder

Answer 24

visceral afferent nerves from bladder stimulate pelvic splanchnic nerves -> contraction of detrusor muscle -> emptying of bladder

Question 25

when does one first sense the urge for voluntary bladder emptying?

Answer 25

around 150 mL, fullness is sensed at 400-500 mL

Question 26

micturation reflex inhibition

Answer 26

•when micturation is inappropriate
efferent impulses from brain inhibit pre-ganglionic parasympathetic neurons in sacral spinal cord and continue to stimulate contraction of the external sphincter via the pudendal nerve

Question 27

erection

Answer 27

• parasympathetic innveration by pelvic splanchnic nerves (S2-S4)
• vasodilation (relaxation) of the arteries in the penis and clitoris so they fill with blood and crimp veins so there is no drainage of blood

Question 28

orgasm/ejaculation

Answer 28

• sympathetic innervation by lumbar splanchnics (L1-L2)
• initiate contraction of smooth muscle of the epididymal ducts, vas deferens, semial vesicles, and prostate to move sperm toward the prostatic urethra

Question 29

pudendal nerve

Answer 29

• anterior rami of spinal nerves S2,3,4
• provides sensory and motor innervation to levator ani and perineum
• exits the greater sciatic foramen, passes over sacrospinous ligament, and enters the lesser sciatic foramen under sacrotuberus ligament to enter pudendal (alcock’s canal)

Question 30

pelvic pain line

Answer 30

• organs above the line are intraperitoneal, and visceral afferents follow the sympathetics
• below are subperitoneal, and visceral afferents follow the parasympathetics