Nerves of the thorax Flashcards
What is the autonomic nervous system under the control of?
• The hypothalamus
•
How many neurones to reach the end organ in the autonomic nervous system?
• 2
Where is the cell body of the preganglionic neurone located?
- Grey matter of the spinal cord or brainstem
* It is myelinated
Where is the cell body of the postganglionic neurone located?
- Autonomic ganglion
* It is unmyelinated
Describe the function of the parasympathetic system
- Rest and digest
- Slows the breathing and heart rate, reducing cardiac output and blood pressure
- Opens sphincters
- Constricts the pupils
- Secremotor to glands: salivary, lacrimal
Describe the route of the vagus nerve
• 10th cranial nerve
• exits the brainstem
• Leaves the cranial cavity via the jugular foramen, descends between the internal jugular vein and internal (then common) carotid artery
•
Describe the route of the right vagus
• Enters the thoracic cavity between the right subclavian and the brachiocephalic trunk
Describe the route of the left vagus
• Enters the thoracic cavity posterior to the left brachiocephalic vein, between the subclavian and common carotid arteries
What are the branches of the right vagus nerve?
• Recurrent laryngeal which winds around the right subclavian artery
What are the branches of the left vagus nerve?
• Recurrent laryngeal which winds around the aortic arch (
aortopulmonary window), just posterolateral to the ligamnetum arteriosum
What do the recurrent laryngeal nerves supply?
- Intrinsic laryngeal muscles
- Middle and inferior pharyngeal constrictor muscles
- Sensory to the laryngeal cavity below the level of the vocal folds
What is the role of the sympathetic nervous system?
- Fight or flight response
- Increases the heart rate and the strength of contraction
- Dilates the coronary arteries
- relaxes bronchial smooth muscle
- Closes sphincters
- Controls body temperature
Where are the sympathetic preganglionic cell bodies?
• Preganglionic cell bodies lie in the intermediolateral horn of T1-L2 spinal cord segments
Where are the sympathetic postganglionic cell bodies?
• Paravertebral sympathetic ganglia - anterior to the neck of the ribs - covered by the parietal pleura - interconnected - sympathetic chain • Wraps around the origin of the abdominal aorta
Where does the sympathetic trunk extend between?
- Atlas and the coccyx
* They fuse together in the single ganglion impair, opposite to the coccyx
Are there more paravertebral sympathetic ganglia or vertebra?
More vertebra because some of the ganglia fuse
Describe the different ganglia
- Superior (C1-4) cervical
- Middle (C5,6) cervical
- Inferior (C7,8) cervical
What makes up the stellate ganglion?
The inferior cervical ganglion and the stellate ganglion
In the sympathetic system, what are the 5 options?
1) synapse at its level
• Postganglionic axons pass in the grey ramus communicant and join T1-L2 spinal nerves
• Heart, thoracic wall, bit of the thigh
2) Travel up the chain to synapse in a cervical ganglion
• Postganglionic axons travel in the grey ramps communicates and join the cervical spinal nerves
• Eye, head, neck, upper torso, heart
3) Travel down the chain and synapse in a lumbar/sacral ganglion
• Postganglionic axons pass in the Grey ramus communicants and join the sacral/lumbar spinal nerves
4) Preganglionic branches pass through the trunk without synapsing
• Travel in the splanchnic nerves to the abdomen
• Synapse in the prevertebral ganglion
• Supplies the abdominal viscera
5) Leaves the sympathetic trunk and goes to the adrenal medulla
What are the splanchnic nerves?
• Thoracic splanchnic nerves: - Greater splanchnic nerve: T5-9 - Lesser splanchnic nerve: T10-11 - Least splanchnic nerve: T12 • Lumbar splanchnic nerve • Pelvic splanchnic nerve
What are the visceral plexuses in the thorax?
• Sympathetic and parasympathetic fibres mix and form an autonomic or visceral plexus
• Cardiac plexus
- anterior to the bifurcation of the trachea and posterior to the ascending aorta
• Pulmonary plexus
- anterior and (mainly) posterior to the roots of the lungs
• Oesophageal plexus
- around the oesophagus
Describe the cardiac plexus
- Anterior to the bifurcation of the trachea and posterior to the ascending aorta
- Sympathetics from T1-5 to the T1-5 ganglia and inferior and middle cervical ganglia
- Visceral afferent fibres travel alongside the sympathetic nerves
- Parasympathetics from the vagus
Describe the pulmonary plexus
- Anterior and (mainly) posterior to the roots of the lung
- sympathetics from the T2-4
- parasympathetics from the vagus
What does the phrenic nerve supply?
• Motor to the diaphragm • Sensory to: - mediastinal pleura - parietal pericardium - peritoneum and pleura related to the central tendon of the diaphragm
Describe the intercostal nerves
• Anterior rami of the thoracic spinal nerves
• Mixed nerves:
- motor branches to the intercostal and abdominal wall muscles
- visceromotor branches to the vessels
• With the exception of T1 which supplies the skin/a dermatome
Describe Pancoast’s tumour
tumour at the apex of the lung which may affect the sympathetic trunk or stellate ganglion compromising the sympathetic supply to the head and neck on the same side
Describe Horner’s syndrome
- Ptosis
- Pupillary constriction
- Anhydrosis
- Flushing of the face
