Lecture 12: Autonomic Nervous System Flashcards
What is the general function of the autonomic nervous system? How does it operate?
- 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
What are the major components of the autonomic nervous system?
- sympathetic (fight or flight)
- parasympathetic (rest and digest)
- enteric (GI function)
What is the major brain structure receiving afferent information in the somatic nervous system?
thalamus
What is the major brain structure receiving afferent information in the autonomic nervous system?
hypothalamus
What is the major source of descending pathways for the somatic nervous system?
cerebral cortex
What is the major source of descending pathways for the autonomic nervous system?
hypothalamus
What are 3 major differences that ANS has?
- cell body ganglion outside of spinal cord
- gap junctions for rapid and continuous contractions
- additional synapses to allow for multiple pathways
What are the differences between preganglionic and postganglionic ANS fibers in terms of their structure and organization within the ANS?
Preganglionic
- lightly myelinated (faster conduction)
- take info from spinal cord to ganglion
Postganglionic
- No myelin
- take info from ganglion to visceral organ
Where are postganglion cell bodies positioned in sympathetic fibers?
close to spinal cord
- think sympathetic chain gang
Where do sympathetic fibers originate?
- thoracolumbar division
- T1 - L3
Where are postganglion cell bodies positioned in parasympathetic fibers?
close to target effector
Where do Parasympathetic fibers originate?
- Craniosacral division
- brainstem - CN 3, 7, 9, 10
- S2 - S4
What are the major neurotransmitters involved in the sympathetic nervous system? Where specifically are they found?
ACh - released at terminals of preganglionic fibers
Norepinephrine - released at terminals of postganglionic fibers
What are the major neurotransmitters involved in the parasympathetic nervous system? Where specifically are they found?
ACh - released at terminals of preganglionic and postganglionic fibers
What type of receptors are used for the neurotransmitters in sympathetic and parasympathetic nervous system?
ionotropic - ligand binding
metabotropic - use g-protein
What is the purpose of the sympathetic “fight or flight” response?
- increase activity during times of physical or emotional stress
- allows our body to make maximum use of its resources, particularly metabolic resources
What are the 3 routes taken after exiting spinal cord via ventral rami for sympathetic nervous system?
- 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
Where do neurons that travel to same level of spinal cord or ascend/descend sympathetic trunk target in the body?
blood vessels and skin via gray communicating rami
Where do prevertebral ganglia target in the body?
visceral organs
- heart
- lungs
- gut
- kidneys
- liver
- bladder
- reproductive organs
What is the purpose of the parasympathetic “rest and digest” response?
decrease activity during “rest and digest” periods to conserve energy use and build energy stores
Why don’t we see all of the sympathetic bodily changes reversed by parasympathetic control? How do these additional sympathetic responses then subside?
- not all structures have innervation of parasympathetic nerves
- they are reduced by a reduction of sympathetic responses instead of direct parasympathetic innervation
Where do the preganglionic neurons originate for the parasympathetic nervous system?
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
What is the postganglionic target for Edinger-Westphal nuclei?
ciliary muscles for pupillary constriction
What is the postganglionic target for superior and inferior salivary nuclei?
salivary and lacrimal glands
What is the postganglionic target for nucleus ambiguous?
cardiac muscles for slowing HR
What is the postganglionic target for dorsal motor nucleus of vagus nerve?
- thorax and abdomen for glandular secretion
- cardiac muscle for slowing HR
- lungs for bronchoconstriction
- gut for increased motility and digestion
What is the postganglionic target for lateral horns of S2-S4?
- colon for vasodilation
- rectum for vasodilation
- bladder for muscle contraction
- reproductive organs for penile and clitoral vasodilation
Which structures do not have dual sympathetic/parasympathetic innervation?
- sweat glands
- erector pili muscles
- most blood vessels
- adrenal medulla
Why are sympathetic responses longer lasting?
- 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
Under what circumstances is the parasympathetic nervous system activated during fear?
paradoxical fear - backed into a corner so you go numb
What are the major areas that control autonomic function?
- hypothalamus
- brainstem nuclei
- amygdala and other limbic structures
- medial prefrontal cortex
- insular cortex
How is the autonomic system regulated?
- baroreceptors
- chemoreceptors
- osmoreceptors
- thermoreceptors
What are the two general functions of afferent input coming from the autonomic nervous system into central structures?
- 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
During the SNS/PNS afferent pathway, what structures project to the SNS/PNS preganglionic neurons? What does this result in?
- 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
How is the autonomic system involved in referred pain?
- 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
heart referred pain
Anterior
- left chest, neck, medial arm
Posterior
- C7/middle of back
Lung and diaphragm referred pain
Anterior/Posterior
- left neck/trap region
Esophagus referred pain
Anterior
- sternum and left chest
Liver and gallbladder referred pain
Anterior
- right lateral neck and top of shoulder
Posterior
- right upper back and shoulder
- inferior angle of scapula
- right kidney area
Stomach referred pain
Anterior
- middle of torso
Posterior
- in-between scapula
Pancreas referred pain
Anterior
- middle of torso
Gallbladder referred pain
Anterior
- right lower quadrant of torso
Kidney referred pain
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
Small Intestine referred pain
Anterior
- middle of torso just above belly button
Appendix referred pain
Anterior
- Right lower quadrant of torso just above start to legs
- from ASIS diagonally towards genitals
Ovary referred pain
Anterior
- just right and left of midline in lower belly region
Colon referred pain
Anterior
- middle of body right about at ASIS line
Urinary Bladder referred pain
Anterior
- right above genitals and genital area
Posterior
- top of butt crack
- below gluteal fold on inner part of hamstrings
What structures are involved in the central autonomic network?
- insula
- medial prefrontal cortex
- hypothalamus
- limbic system - hippocampal formation and amygdala
What is the role of the insular cortex in the central autonomic network?
primary visceral sensory area
What is the role of the medial prefrontal cortex in the central autonomic network?
primary visceral motor area
- ex: blushing in response to embarrassing moments or vasoconstriction and pallor during fear
What is the role of the hypothalamus in the central autonomic network?
- homeostasis
- Controls blood flow, regulates energy metabolism, regulates reproductive activity, and coordinates responses to threatening conditions
What is the role of the limbic system in the central autonomic network?
- hippocampal formation and amygdala
- link memory and emotion to autonomic functions
What is the function of the enteric system?
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)
