Somatic & Visceral Innervation of the Chest

Question 1

dorsal ramus

Answer 1

• branch going toward back side

- has both motor and sensory neurons

Question 2

rami communicans

Answer 2

• allow different spinal nerves to synapse on one another (communication between neurons)
• gray and white

Question 3

dorsal root

Answer 3

• only associated with sensory components

Question 4

ventral root

Answer 4

• only associated with motor components

Question 5

spinal cord segment

Answer 5

• one inch component of spinal cord (i.e. T4 segment of spinal cord)

Question 6

Would damage of one nerve remove all sensory input from the regions it touches?

Answer 6

• no, overlap of dermatomes means that there would still be some sensory input

Question 7

innervation of diaphragm

Answer 7

• two domes of muscle that meet in middle and attach at central tendon (where heart sits)
• skeletal muscle that gets somatic innervation (from phrenic nerves–C3, C4, C5 in domes, from intercostal nerves in lateral portions)
• phrenic nerve

Question 8

ventral rami

Answer 8

• both sensory and motor nerves

- innervates front of chest for dif sensations

Question 9

phrenic nerve

Answer 9

• C3/C4/C5
• goes through superior thoracic aperture, enters into chest in middle mediastinum (medial to parietal pleura) and innervates diaphragm
• sensory nerves return at same level of those of supraclavicular nerve

Question 10

Why do C3, C4, C5 nerves extend all the way down to diaphragm?

Answer 10

• four week embryo –> relative position of heart bulge & respiratory diaphragm in future neck region
• cervical nerves serve diaphragm and heart (in close proximity)
• when diaphragm and heart moved later in development, pulled cervical nerves with them

Question 11

What do neural crest cells become?

Answer 11

• become dorsal root ganglia & autonomic (sympathetic) ganglia

Question 12

What does neural crest tube become?

Answer 12

• becomes cell body of ventral horn (somatic)

Question 13

somatic nervous system

Answer 13

• one neuron effector system –> only one cell from CNS to skeletal muscle

Question 14

autonomic nervous system

Answer 14

• two neuron effector system –> pre-synaptic cell and post-synaptic cell

Question 15

intercostobrachial nerve

Answer 15

• at T2

- goes into arm

Question 16

cutaneous branches of segmental spinal nerves

Answer 16

• some of skin on chest gets innervation coming neck (C3, C4)

Question 17

supraclavicular nerves

Answer 17

• C3, C4
• come off ventral rami
• passes around sternocleidomastoid and descends to innervate skin over superior region of chest and shoulder

Question 18

segmental spinal nerves

Answer 18

• remnant of “metameric segmentation”
• branches into cutaneous branches
• contains mix of motor and sensory nerves (mixed nerve)

Question 19

pericardiophrenic vessels

Answer 19

• pericardiophrenic artery/vein and phrenic nerve travel together through mediastinum

Question 20

internal thoracic artery (left and right)

Answer 20

• branches from subclavian artery
• descends along anterior thoracic wall lateral to sternum
• gives off anterior intercostals (supply intercostal spaces)

Question 21

intercostal nerves

Answer 21

• T1/T2 supply upper limb
• T3-T6 distributed throughout wall of thoracic cavity
• T7-T12 supply parts of thoracic and abdominal cavity walls
• make up afferents of periphery of diaphragm

Question 22

“referred pain”

Answer 22

• pain is felt in dermatomes
• diaphragm innervated by C3-5, so afferents return to those vertebrae
• on dermatome, C3-5 corresponds to neck and upper chest region
• pain felt in diaphragm is often “felt” in neck/chest because mix of sensory info at spinal cord

Question 23

pseudo-unipolar neuron

Answer 23

• sensory neuron of somatic NS
• dendrites on receptor “organ” and axon terminals in spinal cord
• cell bodies always outside CNS ( in dorsal root ganglia)

Question 24

multipolar neuron

Answer 24

• motor neuron
• cell body found in CNS (spinal cord)
• peripheral axon terminals synapse on effector organ
• in somatic NS, one neuron effector system (cell body found in Ventral horn)
• in autonomic NS, two neuron effector system (cell body found in lateral horn –> sympathetic)

Question 25

dorsal root ganglia

Answer 25

- collection of pseudo-unipolar cell bodies | - derivative of neural crest cells

Question 26

sympathetic NS

Answer 26

- spinal cord segments: T1 to L2/3 (thoracolumbar outflow) - preganglionic (presynaptic) cell bodies found in lateral horn - many post-synaptic cell bodies found sympathetic trunk in paravertebral ganglia - presynaptic axons are short (sympathetic truck ganglia), postsynaptic axons are long and go to effector organ

Question 27

splanchnic nerves

Answer 27

- innervate visceral organs (sympathetic NS) | - pre-synaptic and post-synaptic cells synapse in prevertebral ganglia

Question 28

white communicating rami

Answer 28

- preganglionic sympathetic nerve fibers from spinal cord enter ganglia through these communicating rami and synapse with postganglionic sympathetic nerve fibers - may synapse at level of entry or run up or down sympathetic trunk to a dif level before synapsing

Question 29

gray communicating rami

Answer 29

- postganglionic fibers exit ganglia of sympathetic trunk through these communicating rami and branch to plexuses or organs

Question 30

pulmonary ligament

Answer 30

- some of pleura dips down to innervate belly | - posterior to root of lung

Question 31

parasympathetic NS

Answer 31

- craniosacral outflow - brainstem (cranial nerves) and sacral nerves - ganglia close to or within effector organs - long presynaptic axon, short postsynaptic axon

Question 32

CN III

Answer 32

- pupillary sphincter | - parasympathetic

Question 33

CN VII & IX

Answer 33

- salivary and tear glands | - parasympathetic

Question 34

CN X

Answer 34

- vagus nerve --> leaves head and goes through superior thoracic aperture - parasympathetic - heart, lungs, and digestive tract

Question 35

sacral spinal cord segments (S1-S5)

Answer 35

- large intestine, urogenital tract | - parasympathetic

Question 36

formation of esophageal plexus

Answer 36

- vagus nerves (left and right) go behind root of lung and down esophagus, forming plexus - posterior mediastinum

Question 37

anterior vagus nerve

Answer 37

- branch of vagus nerve | - down esophagus past diaphragm at stomach

Question 38

formation of cardiac plexus

Answer 38

- SNS & PNS --> comes around arch of aorta - goes backwards to heart, following blood vessels - pain fibers --> pain from heart because cardiac muscle is hungry for oxygen forms from these nerves: superior cervical ganglion, middle cervical ganglion, inferior cervical and T1 ganglia, T2 sympathetic ganglion, T3 sympathetic ganglion

Question 39

balancing heart rate in autonomic NS

Answer 39

- brain telling heart to slow down | - withdrawing vagus stimulation causes heart to beat faster

Question 40

cardiac radiating pain (referred pain)

Answer 40

- crisscrossing of signals from heart and other nerves | - T1/T2/T3 --> experience pain in these dermatomes