Autonomic NS and Visceral Sensation

Question 1

Sympathetic anatomy

Answer 1

Preganglionic cell bodies have thoracolumbar origin of T1to L3 spinal cord segments
Axons leave CNS via ventral roots and enter communicating branch of spinal nerve, travel via sympathetic trunk
Postganglionic cell bodies in chain ganglia of trunk or prevertebral ganglia in abdominal and pelvic cavities
Short pre and long postganglionc fibers, found everywhere

Question 2

Carotid sinus reflex

Answer 2

Control of systemic blood pressure, involves baroreceptors

Question 3

Micturition

Answer 3

Voiding urinary bladder

Requires integration of neurons from all parts of nervous system (Symp, PS, and somatic circuits)

Question 4

Viscerosomatic reflex

Answer 4

Protective reflex generated by visceral afferents in parietal/visceral layers of peritoneum or w/in a visceral organ integrated w/ somatic motorneurons innervating abdominal body wall
Occurs over inflamed body part -> localized rigidity of overlying somatic skeletal muscle

Question 5

Common drugs that act on ANS

Answer 5

Atropine: blocks coupling of ACh on target cell

Question 6

Autonomic nervous system

Answer 6

Innervates all cardiac and smooth muscle, visceral organs, and glands
Dual and antagonistic in action, visceral organs supplied by both ANS divisions operating in antagonistic pattern (exceptions in limbs, skin, and salivary glands)

Question 7

Visceral structures

Answer 7

Located inside body and function to regulate internal environment, innervated by visceral neurons (sensory afferents and motor efferents)

Question 8

Somatic structures

Answer 8

Located in body wall and function to interact with external environment, innervated by somatic neurons (sensory afferents and motor efferents)

Question 9

Referred pain

Answer 9

Allows for a maybe event to be noticed by animal

Saves neurons by piggy-backing on somatic sensory afferent

Question 10

Visceral pain

Answer 10

Caused by a blockage (in a hollow organ), capsule stretch (in a solid organ), or referred pain in association with either serial inflammation or convergence onto spinal interneurons receiving somatic input

Question 11

Central pathway of visceral afferent neurons

Answer 11

Free nerve endings wrapped around organs and respond to mechanical/chemical stimuli
Visceral afferents -> nucleus of tractus solitaires (NTS) -> parabrachial nucleus, reticular formation, hypothalamus, amygdala, midline thalamus, cingulated gyrus, orbitofrontal cortex, and insula

Question 12

Properties of visceral afferent neurons

Answer 12

90% C fibers, cell bodies in DRG or cranial nerve sensory ganglia
Capable of signaling both nociceptive and non effects in visceral organs
Sympathetic nerves carry visceral afferents -> cortical perception
PS nerves carry afferents relaying reflex and regulatory info which isn’t perceived

Question 13

ENS reflexes

Answer 13

Intrisic

Peristaltic reflex, segmentation/mixing movements and tonic sphincter contractions

Question 14

Neurons in enteric system

Answer 14

Most adrenergic, not cholinergic

Question 15

Sympathetic physiology

Answer 15

Fight or flight

Operates globally over entire body due to adrenal gland

Question 16

Parasympathetic physiology

Answer 16

Rest and digest

Operates by controlling organs individually and locally as needed to maintain homeostasis

Question 17

Parasympathetic pharmacology

Answer 17

Postganglionic neurons release ACh onto target tissue which contains muscarinic receptors

Question 18

Common to PS and S: Anatomy

Answer 18

Postganglionc fibers are unmyelinated and preganglionic fibers thinly or unmyelinated

Question 19

Common to PS and S: Pharmacology

Answer 19

Release ACh from preganglionic neurons that act on post junctional nicotinic receptor at somatic MNJ and in ANS ganglia
Exception: non-apocrine sweat glands are sympathetic targets but respond to ACh release

Question 20

Enteric nervous system

Answer 20

Intrinsic neural network in GI tract capable of generating rhythmic coordinated contractions/relaxation of intestinal musculature in absence of input from CNS
Coordinated action between 2 smooth muscle layers
Local ganglia w/in each plexus connected via interganglionic fiber tracts
Controls gut endocrine cells and secretory activity of epithelial cells

Question 21

Sympathetic pharmacology

Answer 21

Postganglionic neurons release norepinephrine onto target tissue which contains adrenergic receptors

Question 22

Parasympathetic anatomy

Answer 22

Preganglionic cell bodies have craniosacral origin, residing in nerve PS nuclei associated w/ CN 3, 7, 9, and 10 and S1-S4 spinal cord segments
Postganglionic cell bodies in specialized PS ganglia in head or terminal ganglia near or w/in visceral organ
Long pre and short postganglionic fibers, found only in visceral cavities, external genitalia, eye, and glands of head

Question 23

VCL/VCM

Answer 23

ventrocaudal lateral

ventrocaudal medial