Lecture 12: Autonomic Nervous System

Question 1

What is the general function of the autonomic nervous system? How does it operate?

Answer 1

• Controls the function of structures with smooth muscle, cardiac muscle, and certain glands
• operates w/o conscious control but can be modulated by conscious drive

Question 2

What are the major components of the autonomic nervous system?

Answer 2

• sympathetic (fight or flight)
• parasympathetic (rest and digest)
• enteric (GI function)

Question 3

What is the major brain structure receiving afferent information in the somatic nervous system?

Answer 3

thalamus

Question 4

What is the major brain structure receiving afferent information in the autonomic nervous system?

Answer 4

hypothalamus

Question 5

What is the major source of descending pathways for the somatic nervous system?

Answer 5

cerebral cortex

Question 6

What is the major source of descending pathways for the autonomic nervous system?

Answer 6

hypothalamus

Question 7

What are 3 major differences that ANS has?

Answer 7

• cell body ganglion outside of spinal cord
• gap junctions for rapid and continuous contractions
• additional synapses to allow for multiple pathways

Question 8

What are the differences between preganglionic and postganglionic ANS fibers in terms of their structure and organization within the ANS?

Answer 8

Preganglionic

• lightly myelinated (faster conduction)
• take info from spinal cord to ganglion

Postganglionic

• No myelin
• take info from ganglion to visceral organ

Question 9

Where are postganglion cell bodies positioned in sympathetic fibers?

Answer 9

close to spinal cord

- think sympathetic chain gang

Question 10

Where do sympathetic fibers originate?

Answer 10

• thoracolumbar division

- T1 - L3

Question 11

Where are postganglion cell bodies positioned in parasympathetic fibers?

Answer 11

close to target effector

Question 12

Where do Parasympathetic fibers originate?

Answer 12

• Craniosacral division
• brainstem - CN 3, 7, 9, 10
• S2 - S4

Question 13

What are the major neurotransmitters involved in the sympathetic nervous system? Where specifically are they found?

Answer 13

ACh - released at terminals of preganglionic fibers

Norepinephrine - released at terminals of postganglionic fibers

Question 14

What are the major neurotransmitters involved in the parasympathetic nervous system? Where specifically are they found?

Answer 14

ACh - released at terminals of preganglionic and postganglionic fibers

Question 15

What type of receptors are used for the neurotransmitters in sympathetic and parasympathetic nervous system?

Answer 15

ionotropic - ligand binding

metabotropic - use g-protein

Question 16

What is the purpose of the sympathetic “fight or flight” response?

Answer 16

• increase activity during times of physical or emotional stress
• allows our body to make maximum use of its resources, particularly metabolic resources

Question 17

What are the 3 routes taken after exiting spinal cord via ventral rami for sympathetic nervous system?

Answer 17

• travel to sympathetic trunk via white communicating rami and synapse immediately with postganglionic neurons at same level of spinal cord
• travel to sympathetic trunk via white communicating rami and ascend/descend to synapse in cranial or caudal ganglia
• continue through trunk w/o synapsing and later synapse with postganglionic neurons in prevertebral ganglia

Question 18

Where do neurons that travel to same level of spinal cord or ascend/descend sympathetic trunk target in the body?

Answer 18

blood vessels and skin via gray communicating rami

Question 19

Where do prevertebral ganglia target in the body?

Answer 19

visceral organs

• heart
• lungs
• gut
• kidneys
• liver
• bladder
• reproductive organs

Question 20

What is the purpose of the parasympathetic “rest and digest” response?

Answer 20

decrease activity during “rest and digest” periods to conserve energy use and build energy stores

Question 21

Why don’t we see all of the sympathetic bodily changes reversed by parasympathetic control? How do these additional sympathetic responses then subside?

Answer 21

• not all structures have innervation of parasympathetic nerves
• they are reduced by a reduction of sympathetic responses instead of direct parasympathetic innervation

Question 22

Where do the preganglionic neurons originate for the parasympathetic nervous system?

Answer 22

Brainstem

• CN 3 - edinger-westphal nuclei
• CN 7 - superior and inferior salivary nuclei
• CN 9 - Nucleus Ambiguous
• CN 10 - Dorsal Motor nucleus of vagus nerve

Sacral
- lateral horns of S2-S4

Question 23

What is the postganglionic target for Edinger-Westphal nuclei?

Answer 23

ciliary muscles for pupillary constriction

Question 24

What is the postganglionic target for superior and inferior salivary nuclei?

Answer 24

salivary and lacrimal glands

Question 25

What is the postganglionic target for nucleus ambiguous?

Answer 25

cardiac muscles for slowing HR

Question 26

What is the postganglionic target for dorsal motor nucleus of vagus nerve?

Answer 26

- thorax and abdomen for glandular secretion - cardiac muscle for slowing HR - lungs for bronchoconstriction - gut for increased motility and digestion

Question 27

What is the postganglionic target for lateral horns of S2-S4?

Answer 27

- colon for vasodilation - rectum for vasodilation - bladder for muscle contraction - reproductive organs for penile and clitoral vasodilation

Question 28

Which structures do not have dual sympathetic/parasympathetic innervation?

Answer 28

- sweat glands - erector pili muscles - most blood vessels - adrenal medulla

Question 29

Why are sympathetic responses longer lasting?

Answer 29

- divergence of preganglion neurons - longer unmyelinated postganglionic neurons - slower inactivation of norepinephrine in the synapse - presence of norepinephrine and epinephrine from adrenal medulla in blood

Question 30

Under what circumstances is the parasympathetic nervous system activated during fear?

Answer 30

paradoxical fear - backed into a corner so you go numb

Question 31

What are the major areas that control autonomic function?

Answer 31

- hypothalamus - brainstem nuclei - amygdala and other limbic structures - medial prefrontal cortex - insular cortex

Question 32

How is the autonomic system regulated?

Answer 32

- baroreceptors - chemoreceptors - osmoreceptors - thermoreceptors

Question 33

What are the two general functions of afferent input coming from the autonomic nervous system into central structures?

Answer 33

- Feedback input via solitary nucleus for local autonomic reflexes (modulates visceral motor activity) - Inform higher integrative centers of more complex patterns of stimulation that may signal danger and/or may require more multi-system control

Question 34

During the SNS/PNS afferent pathway, what structures project to the SNS/PNS preganglionic neurons? What does this result in?

Answer 34

- solitary nucleus (reflexive control) - hypothalamus (homeostasis) - medullary reticular formation (general modulatory control) - results in inhibition or excitation of SNS/PNS preganglionic neurons depending on what is needed

Question 35

How is the autonomic system involved in referred pain?

Answer 35

- 2nd order neurons that receive visceral pain are part of anterolateral system which is in charge of cutaneous pain, some visceral pain gets perceived as cutaneous pain - Referred pain

Question 36

heart referred pain

Answer 36

Anterior - left chest, neck, medial arm Posterior - C7/middle of back

Question 37

Lung and diaphragm referred pain

Answer 37

Anterior/Posterior | - left neck/trap region

Question 38

Esophagus referred pain

Answer 38

Anterior | - sternum and left chest

Question 39

Liver and gallbladder referred pain

Answer 39

Anterior - right lateral neck and top of shoulder Posterior - right upper back and shoulder - inferior angle of scapula - right kidney area

Question 40

Stomach referred pain

Answer 40

Anterior - middle of torso Posterior - in-between scapula

Question 41

Pancreas referred pain

Answer 41

Anterior | - middle of torso

Question 42

Gallbladder referred pain

Answer 42

Anterior | - right lower quadrant of torso

Question 43

Kidney referred pain

Answer 43

Anterior - belly button and down to inner groin - lateral hips and side of upper leg Posterior - lumbar region - lateral hips and side of upper leg

Question 44

Small Intestine referred pain

Answer 44

Anterior | - middle of torso just above belly button

Question 45

Appendix referred pain

Answer 45

Anterior - Right lower quadrant of torso just above start to legs - from ASIS diagonally towards genitals

Question 46

Ovary referred pain

Answer 46

Anterior | - just right and left of midline in lower belly region

Question 47

Colon referred pain

Answer 47

Anterior | - middle of body right about at ASIS line

Question 48

Urinary Bladder referred pain

Answer 48

Anterior - right above genitals and genital area Posterior - top of butt crack - below gluteal fold on inner part of hamstrings

Question 49

What structures are involved in the central autonomic network?

Answer 49

- insula - medial prefrontal cortex - hypothalamus - limbic system - hippocampal formation and amygdala

Question 50

What is the role of the insular cortex in the central autonomic network?

Answer 50

primary visceral sensory area

Question 51

What is the role of the medial prefrontal cortex in the central autonomic network?

Answer 51

primary visceral motor area | - ex: blushing in response to embarrassing moments or vasoconstriction and pallor during fear

Question 52

What is the role of the hypothalamus in the central autonomic network?

Answer 52

- homeostasis - Controls blood flow, regulates energy metabolism, regulates reproductive activity, and coordinates responses to threatening conditions

Question 53

What is the role of the limbic system in the central autonomic network?

Answer 53

- hippocampal formation and amygdala | - link memory and emotion to autonomic functions

Question 54

What is the function of the enteric system?

Answer 54

Exerts control of gastrointestinal system through neuronal system embedded in the lining of GI organs - peristalsis - segmentation (washing machine movement of stomach to churn food) - hormone secretion (gastrin, secretin)