Nerves of the thorax Flashcards
AUTONOMIC NERVOUS SYSTEM
✓ Under the control of the hypothalamus
dual innervation of the ANS
Sympathetics and parasympathetics exert opposite effects in a particular organ/tissue but they functionally complement each other to keep the body functioning normally.
AUTONOMIC NERVOUS SYSTEM role
✓ Regulates the visceral activity (Circulation, respiration, digestion, excretion, reproduction)
• Supplies smooth muscles (walls of the blood vessels, bronchi, intestines)
• Supplies the cardiac muscle
• Supplies the glands
✓ Regulates body temperature
✓ Autonomic fibres “accompany” the general visceral afferent fibres
AUTONOMIC NERVES
✓Reach the end organ with two neurons
✓Cell body of the 1st neuron (preganglionic neuron) is at grey matter of the spinal cord or brain stem
− axon is myelinated
✓Cell body of the 2nd neuron (postganglionic neuron) is at an autonomic ganglion
− axon is unmyelinated
PARASYMPATHETIC SYSTEM
✓ Rest & digest or Rest & repose - conserves energy
✓ Slows breathing and heart rate, reducing cardiac output and BP ✓ Stimulates digestion (secretion of digestive enzymes)
✓ Opens sphincters
✓ Constricts pupils (accommodation for close focus)
✓ Secretomotor to glands (salivary, lacrimal)
VAGUS
✓ The parasympathetic innervation of the thoracic viscera is by the 10th cranial nerve, vagus
✓ Vagus leaves cranial cavity through jugular foramen, descends between internal jugular vein and internal (then common) carotid artery
right vagus
✓ Right vagus enters the thoracic cavity between the right subclavian artery and Brachiocephalic vein
left vagus
✓ Left vagus enters the thoracic cavity posterior to the left Brachiocephalic vein, between the subclavian and common carotid arteries
right recurrent laryngeal nerve
winds around right subclavian artery
left recurrent laryngeal nerve
winds around the aortic arch (aortopulmonary window), just posterolateral to the ligamentum arteriosum
✓ Recurrent laryngeal nerves supply
− Intrinsic laryngeal muscles (Except 1)
− Middle and inferior pharyngeal constrictor muscles
− sensory to the laryngeal cavity below the level of the vocal folds
SYMPATHETIC SYSTEM
✓ It prepares the body to “Fight or flight” situations → body uses energy
✓ Increases heart rate and strength of heart beat
✓ Dilates coronary arteries (indirectly, by local metabolic factors)
✓ Constricts peripheral arteries
✓ Relaxes bronchial smooth muscles (Increases respiratory efficiency)
✓ Closes sphincters
✓ Controls body temperature (blood vessels, sweat glands)
(THORACOLUMBAR OUTFLOW) ✓ Preganglionic cell bodies
lie in the intermediolateral horn of T1-L2 spinal cord segments
(THORACOLUMBAR OUTFLOW) ✓ Postganglionic cell bodies
lie either in paravertebral sympathetic ganglia
− Anterior to the neck of the ribs→lateral aspect of the vertebral bodies
− Covered by the parietal pleura
−Interconnected→sympathetic chain (sympathetic trunk)
OR
✓ Postganglionic cell bodies lie in prevertebral sympathetic ganglia
− around the origins of branches of abdominal aorta
✓ Number of paravertebral sympathetic ganglia
− Superior (C1-4), middle (C5-6) and inferior (C7-8) cervical ganglia
− Inferior cervical+T1→Stellate Ganglion (cervicothoracic ganglion) (C7-T1)
four routes for sympathetic synapse - Synapse at its level
• Postganglionic axons (unmyelinated, grey) pass in the GRC and join T1-L2 Spinal nerves
four routes for sympathetic synapse - Travel up the chain to synapse in a cervical ganglion
• Postganglionic axons
pass in the GRC and join cervical spinal nerves
four routes for sympathetic synapse - Travel down the chain to synapse in a lumbar/sacral ganglion
• Postganglionic axons
pass in the GRC and join lumbar/sacral spinal nerves
four routes for sympathetic synapse - Preganglionic branches pass through the sympathetic trunk without synapsing
- Travel in splanchnic nerves to the abdomen
- Synapse in a prevertebral ganglion
- Supply abdominal viscera
✓ Thoracic splanchnic nerves
- Greater splanchnic nerve: T5-9
- Lesser splanchnic nerve: T10-11
- Least splanchnic nerve: T12
other types of splanchnic nerves (preganglionic autonomic(sympathetic) nerve )
✓ Lumbar splanchnic nerves
✓ Pelvic splanchnic nerves
✓ Sympathetics of the head
from T1 - T3 segments
✓ Sympathetics of the upper limb
from T4 - T6 segments
✓ Sympathetics of the thoracic and abdominal walls
from T1 - T12 segments
✓ Sympathetics of the lower limb
from T12 to L2 segments
autonomic or visceral plexuses in the thorax, abdomen or pelvis
✓ Sympathetic and parasympathetic fibres mix
• 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
CARDIAC PLEXUS
✓ Sympathetics from T1-5 → T1-5 ganglia + inferior and middle cervical ganglia
− Visceral afferent fibres travel alongside the sympathetic nerves
− Referred pain from heart to T1 /T2 dermatomes (medial aspect of left arm) +T3-5
✓ Parasympathetics from vagus
PULMONARY PLEXUS
✓ Sympathetics from T2-4 → T2-4 ganglia
✓ Parasympathetics from vagus
PHRENIC NERVE
✓Sole motor supply to the diaphragm
✓Also supplies sensory fibres to ✓the mediastinal parietal
pleura
✓parietal pericardium
✓peritoneum and pleura related to the central tendon of the diaphragm
INTERCOSTAL NERVES
✓ Anterior rami of the thoracic spinal nerves
✓ Mixed nerves
– Motor branches to intercostal and abdominal wall muscles
– Visceromotor branches to vessels
– Lateral cutaneous branch
– Anterior cutaneous branch
PANCOAST’S TUMOUR
Tumour at the apex of the lung may affect the sympathetic trunk or stellate ganglion, compromising sympathetic supply to the head and neck on the same side
Horner’s syndrome
- Ptosis (drooping) of the upper eyelid • Pupillary constriction (miosis)
- Anhydrosis (lack of sweating)
- Flushing of the face
