Lecture 15: ANS Pain Flashcards
How many neurons are in the pain system?
Two neurons
Where is the preganglionic and post-ganglionic neuron in the pain system found?
The preganglionic neuron is in the CNS and the axon is in the PNS
The postganglionic neuron is in the peripheral nervous system
What is the autonomic NS responsible for innervating?
Visceral tissues:
Internal organs
Smooth muscles
Glands of skin
What are the two divisions of the autonomic nervous system?
Sympathetic and Parasympathetic
What can the sympathetic and Parasympathetic system be likened to?
The on and off
How does the sympathetic system affect the lungs, heart and gut?
It increases lung capacity and HR and turns of the gut
How does the parasympathetic nervous system affect the lungs, heart and gut?
It decreases HR and lung capacity and turns on gut
What is the sensory portion of the autonomic nervous system?
Visceral afferent fibres that sense pain only
How many neurons are in the visceral afferent pathway?
One neuron
What pathway is used in the somatic motor system?
Corticospinal tract and corticobulbar tract
Where in the spinal cord is the motor neuron in the somatic motor system?
In the ventral horn, travels to the ventral root and to each spinal nerve
How many neurons are in the autonomic motor pathway?
Two neurons
How many neurons are in the autonomic motor pathway?
Two neurons
What are the two neurons in the autonomic motor pathway?
Preganglionic and post ganglionic neurons
Where is the postganglionic neuron of the autonomic motor system located?
In the PNS in an autonomic ganglion
Where does the postganglionic neuron of the autonomic motor system go to?
Visceral targets:
- Cardiac muscle
- Glands
- Smooth muscle
What is the general pathway of preganglionic neuron in the motor autonomic pathway?
Preganglionic neurons go through the ventral root and extend axons out to join with the spinal nerve to find the autonomic ganglion
What has visceral afferents?
All organs
What sensations do somatic afferents sense?
Many sensations - Hot, cold, pressure, itch, light touch, dull pain, sharp pain
What sensations do visceral afferents sense?
Visceral afferents only sense pain
How can the pain by visceral afferents be described?
Vague, dull, ill localized and poorly focused
What is another name for Sympathetic motor outflow?
Thoracolumbar outflow
What is another name for Parasympathetic outflow?
Craniosacral outflow
What is another name for Thoracolumbar outflow?
Sympathetic
What is another name for Parasympathetic outflow?
Craniosacral outflow
Where in the spinal cord does Thoracolumbar outflow originate?
Thorax and lumbar spinal cord
Where in the spinal cord does Craniosacral outflow originate?
Brainstem and sacral spinal cord
Through what nerves does the autonomic nervous system affect salivation?
VII - Facial
IX - Glossipharyngeal
Through what nerve does the autonomic nervous system affect pupil diameter?
CN III - Oculomotor
What is the sympathetic response of pupil control?
Increase pupil diameter
Where does the somatic nervous system originate?
From the somatic mesoderm
What originates from the somatic mesoderm?
The somatic nervous system
What innervates skin, muscles, bones and body walls?
The somatic nervous system
What does the somatic nervous system innervate?
Skin, muscles and bones of body walls and parietal membranes
What parietal membranes does the somatic nervous system innervate?
Pleura
Pericardium
Peritoneum
Periosteum
What innervates the:
Pleura
Pericardium
Peritoneum
Periosteum
The somatic nervous system
What do the motor nerves of the somatic nervous system supply?
Skeletal muscles
What do the sensory nerves of the somatic motor system sense?
Pain, temperature, touch, chemoreception
Describe the pain sensed by the somatic nervous system
Sharp and well localized
Where does the Visceral/Splanchnic PNS originate?
The splanchnic mesoderm
What originates from the splanchnic mesoderm?
The Visceral/Splanchnic PNS
What does the Visceral/Splanchnic PNS innervate?
Viscera - heart, lungs, liver, glands, blood vessels (smooth muscle), gut uterus, etc
Visceral membranes (PPP)
What vertebral layers does the sympathetic nerve supply?
T1-L2
What portion of the autonomic nervous system is T1-L2?
Sympathetic
What nerves and portions of the spinal cord are supplied by the Parasympathetic nervous system?
CN III - Oculomotor
CN VII - Facial
CN IX - Glossopharyngeal
S234 - Sacral
What is the Sensory supply of the Autonomic nervous system
Visceral afferents travel with sympathetic and vagus (X) and respond to stretch and ischemia
Describe the sensation of pain sensed by the autonomic nervous system
Pain sensed by the autonomic nervous system is dull, vague and ill focused. Only exception is baroreceptors - this sensation is not painful
Describe the innervation of the somatic nervous system to the body wall
The Thorax and abdomen have two layers. An inner visceral layer and a parietal layer that lines the body wall.
The Parietal layer is innervated by the somatic nervous system so pain from this area is very specific
What is the pathway of a typical motor neuron from the spinal cord?
The LMN in the ventral horn project to the spinal nerve and bifurcates to travel the dorsal primary ramus or primary ventral ramus
What is the pathway of a typical sensory neuron to the spinal cord?
Axons from the dorsal primary ramus and ventral primary ramus join and enter the spinal cord and enter the dorsal root
Where are preganglionic parasympathetic cell bodies found?
In the brainstem
III - Oculomotor
VI - Abducens
IX - Glossopharyngeal
X - Vagus
Sacral Spinal Cord
S2, S3, S4
Where are postganglionic parasympathetic cell bodies found?
In the autonomic ganglia close to their target organ/gland
Where are preganglionic sympathetic cell bodies found?
In the spinal cord at T1-L1/2
Where are Postganglionic sympathetic cell bodies found?
In the paravertebral (sympathetic chain) or prevertebral autonomic ganglia (in abdomen)
What is contained in the dorsal horn of the spinal cord?
Sensory neurons
What is contained in the Ventral horns of the spinal cord?
Motor neurons
What is contained in the Lateral horn of the spinal cord?
Preganglionic sympathetic cell bodies
Where are preganglionic sympathetic cell bodies found?
In the lateral horn of the spinal cord
What levels of the spinal cord is the lateral horn present?
From T1-L1/2
Why is the lateral horn only present from T1-L1/2?
Because this is where the sympathetic nervous system produces outflow
What is another name for sacral nerves?
Splanchnic nerves
What is the sacral autonomic outflow
Parasympathetics to the distal part of the GI tract and reproductive organs
Where do the parasympathetic to the distal part of the GI tract and reproductive organs originate?
From the sacral nerves
What is the length of the pre and postganglionic axons of the sympathetic nervous system?
The sympathetic nervous system has short preganglionic and long postganglionic
What is the length of the pre and postganglionic axons of the parasympathetic nervous system?
The parasympathetic nervous system usually has long preganglionic and short postganglionic
Where is the cell bodies for postganglionic neurons usually?
Close to the organ
What is found in the paravertebral (sympathetic chain)/Autonomic chain ganglia?
Postganglionic sympathetic cell bodies
Describe the motor and sensory signaling of the parasympathetic nervous system?
- Food in the stomach causes distension of the stomach lining
- Sensory nerves from the vagus project back to the brainstem and up to the hypothalamus
- This triggers the vagus nerve to promote digestion
What does the Parasympathetic division innervate?
All internal organs of the body but none in the body wall
What lacks parasympathetic innervation?
The Body wall - skin, muscle, bones, parietal membrane
What does the parasympathetic system not innervate?
The body wall - skin, muscle, bones and parietal membranes
What only has sympathetic innervation?
Skin, muscle, bones and parietal membranes
How does the Parasympathetic response affect the GI tract?
It dilates blood vessels leading to the GI tract, increasing blood flow and peristalsis
How does the parasympathetic nervous system affect the eyes?
It causes accommodation of the lens and pupil constriction
What vertebral layer is the separation of innervation of upper sympathetic structures and lower sympathetic structures?
T5
What is T5?
The separation between upper sympathetic function and lower sympathetic function
What does the sympathetic division innervate above T5?
- Eyes
- Salivary glands
- Heart
- Lungs
What are the three pathways that the sympathetic nervous system can innervate?
- Above the diaphragm
- Below the diaphragm
- The skin
What occurs at the sympathetic trunk/sympathetic chain ganglia/Paravertebral column?
The second order sympathetic cell bodies are found here
Where are the sympathetic cell bodies found?
The sympathetic trunk/sympathetic chain ganglia/Paravertebral column
What is the difference between the dermatomes of sympathetic and parasympathetics?
Sympathetics are found at every dermatomatomal level
How does the sympathetic nervous system affect the skin?
It causes sweat and sebaceous glands to empty and little arteries to dilate and arrector pili muscles to contract
Where in the spinal cord are preganglionic sympathetic cell bodies found?
In the lateral horn grey matter
What is found in the lateral horn of the spinal cord?
Preganglionic cell bodies of sympathetic nervous system
What vertebral levels are the preganglionic sympathetic cell bodies?
T1-L2
Which portion of the autonomic nervous system is localized from T1-L2?
The sympathetic nervous system
How does the sympathetic nervous system affect muscles?
Dilates muscle blood vessels
How does the sympathetic nervous system affect the lungs?
Dilates bronchioles of the lung to allow for greater alveolar oxygen exchange
How does the sympathetic nervous system affect the heart?
Increases heart rate and provides vasodilation to the coronary artery
How does the sympathetic nervous system affect the eyes?
Dilates pupils and relaxes the ciliary muscle of the lens to allow light to enter
How does the sympathetic nervous system affect glucose?
Increases glucose secreted from the liver
Where in the spinal cord are preganglionic sympathetic motor cell bodies?
In the lateral horn of the spinal cord
What is the pathway of motor sympathetic innervation to the body wall from T1-L1/2(skin, sweat glands, arrector pili muscles, smooth muscles in arterioles)?
- Motor axons leave the ventral root and joint the spinal cord
- It will then leave the spinal cord through the white ramus communicans where it synapses with the second order neuron
- The second order neuron will then enter the gray ramus communicans and re enter the spinal nerve and goes to the DPR and the VPR
What is the only pathway that uses the white and grey communicans?
The Sympathetic pathway
What kind of axons are found in a spinal nerve?
- Somatic afferents
- Visceral afferents
- LMNs (somatic motor)
- Preganglionic sympathetics
What kind of axons are found in a nerve at the top of the skin or a muscle?
- Somatic afferents
- Visceral afferents
- LMNs (somatic motor)
- Postganglionic sympathetics
What is the somatic motor pathway from the spinal cord?
- LMN cell body in the ventral horn sends its axons out through the ventral root
- It continues to the spinal nerve and goes to the DPR or VPR
What is the White Ramus Communicans from T1-L2?
The path that the sympathetic portion of the spinal nerve uses to leave the spinal nerve to find the postganglionic neuron
What is the grey ramus communicans?
The path that the sympathetic portion of the spinal nerve uses to rejoin the spinal nerve to skin, sweat glands, arrector pili muscles and arteries
What is the pathway for sympathetic motor axons above or below T1-L2 innervate the skin?
- The preganglionic sympathetic nerve leaves the ventral root
- It travels to the spinal nerve and leaves the spinal nerve using the white ramus communicans
- It synapses onto the postganglionic neuron
- Instead of going to the grey ramus communicans it travels up to above T1 or below L1/L2
Where does motor sympathetic innervation to the skin above T1 or below L1/L2 originate?
It originates from the T1-L1/2 level
What is the difference in motor sympathetic innervation from T1-L1/2 vs above or below these zones?
The difference between the two is the in the T1-L1/2 it rejoins the spinal nerve at the same vertebral level at the grey ramus communicans. Above or below it rejoins the spinal nerve at the grey ramus communicans at a different vertebral level to get back to the spinal nerve
Why is the white ramus communicans not found everywhere?
Because the white ramus communicans is only required when the motor autonomic portion of a spinal nerve needs to leave to nerve in order to to find the postganglionic sympathetic motor neuron. It doesn’t do this above T1 or below L1/2
What is the pathway of sympathetic motor innervation to organs above the diaphragm but not the skin (eye, salivary gland, etc)?
- Preganglionic sympathetic motor neurons exit the ventral root
- They join the spinal nerve then leave the spinal nerve using the white ramus communicans
- They then travel up the sympathetic chain ganglion
- And synapse at the superior cervical ganglion
- The postganglionic neuron then goes to the eye, salivary gland, etc
What is the pathway of sympathetic motor innervation to organs above the diaphragm but not the skin (heart and lungs)?
- Motor neuron exits the ventral root
- Joins the spinal nerve
- Exits the spinal nerve using the white ramus communicans and synapses on the LMN
- Has a direct cardiac branch that goes directly to the heart and thorax
What vertebral layers do motor sympathetic to the heart and lungs originate?
T1-T5
What is the difference between the motor sympathetic pathway to the heart and lungs vs eyes and salivary glands?
Sympathetics to the eyes and salivary glands (etc) go and synapse at the super cervical ganglion. Sympathetics to the heart and lungs synapses after entering the white ramus communicans and has a direct route to the thorax
How many neurons is in the pathway of the visceral afferent pathway from the heart?
One neuron
What is the pathway of the visceral afferent from the heart?
Directly for the thorax is will join the white ramus communicans, join the spinal nerve and enter the dorsal horn of the spinal cord
Where do all sympathetics to the thorax arise from?
T1 to T5
Where do splanchnic nerves arise from?
Within the sympathetic thoracic trunk to innervate the abdominal viscera
What vertebral levels does sympathetic innervation of the abdominal viscera arise from?
T5 - L1/2
What are the steps in the sympathetic innervation of the GI system?
- Motor neurons arise in the ventral root of the spinal cord arising from T5 - L1/2
- They enter the white ramus communicans
- They do not rejoin the spinal nerve. They form a splanchnic nerve that goes below the diaphragm
- It synapses just below the abdominal aorta
- the postganglionic sympathetic neuron then goes to GI organs
Where does the sympathetic pathway to the GI organs synapse?
At the abdominal aorta
Which sympathetic pathway synapses below the abdominal aorta?
The splanchnic sympathetic pathway to the GI system
What is the pathway of pain from the GI area?
- The pain neuron travels along the splanchnic nerve
- It reaches cell bodies in the DRG and enters the spinal cord and synapses
- Travels along the spinothalamic tract to the cortex
What tract does pain from the GI travel when it reaches the spinal cord?
The spinothalamic tract
Where does visceral referred pain feel like it arises from?
Somatic structures supplied by those same spinal levels
What is the main characteristic of visceral pain?
It is always referred
What is visceral pain carried by?
Visceral afferent fibers
What do Visceral afferent fibers do?
Respond to stretch, ischemia and chemoreception in the viscera
What is the pathway if an injury is to somatic structures (ie front skin) of the T2 dermatome?
- Somatic afferents in the ventral primary ramus elicit an action potential
- It travels from the ventral primary ramus to the dorsal horn of the spinal cord
- From the dorsal horn of the spinal cord travels up the spinothalamic tract to the cortex
If the injury arising from a somatic structure like the skin what is the sensation like?
It is well localized to the site of the injury and is sharp
What vertebral region does the heart sit at?
T1-T5
What regions does T1-T5 innervate?
Heart
Eyes
Lungs
Salivary glands
Because they all sit above the diaphragm
What general area does the T1-T5 area innervate?
All visceral organs above the diaphragm
What is the pathway that referred pain from the heart travels?
- Preganglionic sympathetics from T1 - T5 arise bilaterally from the heart
- They enter the dorsal root of the spinal cord and travel up the spinothalamic tract (same tract as it was coming from the body wall)
- Goes to the primary somatosensory cortex so the brain perceives the pain along the body wall
Why do the same axons that innervate the eyes, lungs, salivary glands, heart etc?
Because all the axons arise from the T1 - T5 level
What vertebral areas innervate the heart?
The heart is innervated bilaterally innervated by T1-T5
How is the heart innervated (motor)?
- Preganglionic sympathetics from T1 - T5 bilaterally send their axons from the lateral horn of the spinal cord to the ventral root of the spinal cord
- It joins the spinal nerve
- Exits the spinal nerve through the white ramus communicans and synapses with the second order neuron and goes directly to the heart bilaterally
Why does pain from the heart feel like it is coming from a general area?
Because it is bilaterally innervated by T1-T5 which also innervates many somatic body structures above the diaphragm so the body thinks that the pain is coming from somatic structures along the body wall
What are the characteristics of GI tube from mouth to anus embyrologically?
Embryologically it is one tube that is bilaterally innervated
What is the pathway of pain from somatic structures innervated by T7-T9?
- Pain is sensed directly at the somatic sight
- It travels to the spinal cord where it synapses onto the spinothalamic tract and travels to the cortex
What is the sympathetic motor innervation of the stomach?
- Preganglionic sympathetic axons extend from the ventral root
- Joins the spinal nerve and leaves the spinal nerve though the white ramus communicans
- Enters the sympathetic ganglia but doesn’t synapse
- Enters the diaphragm and synapses at the aorta at the prevertebral ganglia
- The post ganglionic axon goes to the stomach
What vertebral layers innervate the stomach?
T7-T9
What is the visceral afferent pathway of the stomach?
- The stomach is innervated by T7-T9
- Pain is sensed and T7, 8 and 9 are activated bilaterally (since its bilateral, the brain thinks midline)
- It will go up to the brain through passing the prevertebral ganglia and to the spinal nerve and to the dorsal root of the spinal cord and up to the spinothalamic pathway
Why is pain to the stomach sensed midline?
Because it is bilaterally innervated from T7-T9 which also innervates the same dermatome level of somatic structures
What vertebral level is pain from the stomach somatically sensed as coming from?
Midline from T7-T9
What is the sensation from a ruptured appendix?
Pain start midline then moves to the right of the body
What dermatomal level is the appendix innervated by?
T10
What main organ does the T10 innervate?
The appendix
Why does the pain sensation of the appendix move?
Swelling of the appendix will cause pain and the innervation of the spinothalamic tract which initially assumes its midline because its bilaterally innervated. As the appendix gets bigger it rubs against the body wall and visceral pain become direct pain
What is an example of somatic referred pain?
When you hit the elbow and it radiates to the hand
What is an example of somatic referred pain from the diaphragm?
The diaphragm is a skeletal muscle so it is somatically innervated but because it is in the thoracic cavity the brain doesn’t know where it is. It is bilaterally innervated. When there is pain the gallbladder people will report it in the shoulder because it swells and rubs on the diaphragm above it. The diaphragm is innervated by the same spinal nerves that innervate the shoulder
What vertebral levels innervate the diaphragm?
C3, C4 and C5 (phrenic nerve)
What do the C3, C4 and C5 dermatomes innervate?
The shoulder
