ANS II

Question 1

organization of the PNS

Answer 1

• activation more discrete than the SNS
• CN III pupillary constriction, miosis
• secretion of glands- nasal, lacrimal, submandibular (VII), parotid (IX), gastric and pancreatic (X)
• GI peristalsis/ increased motility and sphincter relaxation, bronchial constriction, decreased HR
• from S2-S4-lower GI, urinary bladder, repro organs
• relaxation of ureter and sphincter for urination, penile erection, rectal emptying

Question 2

dorsal motor nucleus of the vagal nerve

Answer 2

in the medulla

Question 3

nucleus tractus solitarius

Answer 3

• sensory control center tells ANS what to do and when

- boundary between pons and midbrain

Question 4

nucleus ambiguus

Answer 4

• cell bodies of preganglionic fibers from CN X to host of terminal ganglia in viscera
• along with dorsal motor nucleus
• in medulla

Question 5

SNS vs PNS

Answer 5

• mostly exert opposing actions-HR, GI

- sometimes act complimentary-PNS does erection and SNS does ejaculation

Question 6

SNS and PNS in gut

Answer 6

• distinct division of ANS, contains more neurons than the spinal cords
• myenteric plexus controls motility
• submucosal plexus controls secretion
• these can work on their own, but are enhanced/ turned down by ANS
• distention of gut by food activated mechano/chemo receptors in the lumen that have sensory neurons in control center and activate PNS to promote digestion
• cutting the PNS results in decrease in GI movement and increase in sphincter tone- PNS is tonic
• SNS mostly controls BV, PNS doe secretion and motility
• sensory neurons in gut input brain and SNS and PNS provide modulatory input to gut
• PNS is mostly pre ganglionic until plexi and SNS is mostly post ganglionic the whole way

Question 7

Gut 2

Answer 7

• Ach is released from PNS- depolarizes cells and causes contractions of smooth muscle
• norepi from SNS hyperpolarizes and relaxes smooth muscle but also causes sphincter contraction- can lead to ileus- blocked

Question 8

micturition

Answer 8

• filling of bladder is controlled by SNS- b2 receptor on internal sphincter and a1 receptor on detrusor muscle. muscle is relaxed and sphincters are contracted
• emptying is PNS- M receptors on detrusor and internal sphincter cause contraction of muscle and relaxation of internal sphincter

Question 9

higher order nuclei

Answer 9

• several autonomic functions are controlled by nuclei in higher areas
• hypothalamus- head ganglion
• nuclei in mid brain, pons, medulla, brain stem
• transection of the brain stem just below medulla results in decrease in BP to less than 1/2 normal
• transection above mid pontine level preserves basal control of arterial pressure, but eliminates modulation by higher structurs
• respiration not ANS per se but is involuntary
• autonomic centers are relay stations for control initiated at higher levels in the brain, esp by hypothalamus and sometimes cerebrum
• sometimes cortical control controls ANS, sometimes ANS overwhelms cortical function

Question 10

vasovagal syncope

Answer 10

• disturbing thoughts in cortex
• activation of vasodilator centers in hypothalamus and heart through vagus- slows heart
• signals through spinal cord to SNS vasodilators in the muscle- increases flow to muscle
• fall in BP reduces blood flow to brain