Nerves of the thorax

Question 1

AUTONOMIC NERVOUS SYSTEM

Answer 1

✓ Under the control of the hypothalamus

Question 2

dual innervation of the ANS

Answer 2

Sympathetics and parasympathetics exert opposite effects in a particular organ/tissue but they functionally complement each other to keep the body functioning normally.

Question 3

AUTONOMIC NERVOUS SYSTEM role

Answer 3

✓ 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

Question 4

AUTONOMIC NERVES

Answer 4

✓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

Question 5

PARASYMPATHETIC SYSTEM

Answer 5

✓ 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)

Question 6

VAGUS

Answer 6

✓ 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

Question 7

right vagus

Answer 7

✓ Right vagus enters the thoracic cavity between the right subclavian artery and Brachiocephalic vein

Question 8

left vagus

Answer 8

✓ Left vagus enters the thoracic cavity posterior to the left Brachiocephalic vein, between the subclavian and common carotid arteries

Question 9

right recurrent laryngeal nerve

Answer 9

winds around right subclavian artery

Question 10

left recurrent laryngeal nerve

Answer 10

winds around the aortic arch (aortopulmonary window), just posterolateral to the ligamentum arteriosum

Question 11

✓ Recurrent laryngeal nerves supply

Answer 11

− Intrinsic laryngeal muscles (Except 1)
− Middle and inferior pharyngeal constrictor muscles
− sensory to the laryngeal cavity below the level of the vocal folds

Question 12

SYMPATHETIC SYSTEM

Answer 12

✓ 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)

Question 13

(THORACOLUMBAR OUTFLOW) ✓ Preganglionic cell bodies

Answer 13

lie in the intermediolateral horn of T1-L2 spinal cord segments

Question 14

(THORACOLUMBAR OUTFLOW) ✓ Postganglionic cell bodies

Answer 14

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

Question 15

✓ Number of paravertebral sympathetic ganglia

Answer 15

− Superior (C1-4), middle (C5-6) and inferior (C7-8) cervical ganglia
− Inferior cervical+T1→Stellate Ganglion (cervicothoracic ganglion) (C7-T1)

Question 16

four routes for sympathetic synapse - Synapse at its level

Answer 16

• Postganglionic axons (unmyelinated, grey) pass in the GRC and join T1-L2 Spinal nerves

Question 17

four routes for sympathetic synapse - Travel up the chain to synapse in a cervical ganglion

Answer 17

• Postganglionic axons

pass in the GRC and join cervical spinal nerves

Question 18

four routes for sympathetic synapse - Travel down the chain to synapse in a lumbar/sacral ganglion

Answer 18

• Postganglionic axons

pass in the GRC and join lumbar/sacral spinal nerves

Question 19

four routes for sympathetic synapse - Preganglionic branches pass through the sympathetic trunk without synapsing

Answer 19

• Travel in splanchnic nerves to the abdomen
• Synapse in a prevertebral ganglion
• Supply abdominal viscera

Question 20

✓ Thoracic splanchnic nerves

Answer 20

• Greater splanchnic nerve: T5-9
• Lesser splanchnic nerve: T10-11
• Least splanchnic nerve: T12

Question 21

other types of splanchnic nerves (preganglionic autonomic(sympathetic) nerve )

Answer 21

✓ Lumbar splanchnic nerves

✓ Pelvic splanchnic nerves

Question 22

✓ Sympathetics of the head

Answer 22

from T1 - T3 segments

Question 23

✓ Sympathetics of the upper limb

Answer 23

from T4 - T6 segments

Question 24

✓ Sympathetics of the thoracic and abdominal walls

Answer 24

from T1 - T12 segments

Question 25

✓ Sympathetics of the lower limb

Answer 25

from T12 to L2 segments

Question 26

autonomic or visceral plexuses in the thorax, abdomen or pelvis

Answer 26

✓ Sympathetic and parasympathetic fibres mix

Question 27

• Cardiac plexus

Answer 27

Anterior to the bifurcation of the trachea and | posterior to the ascending aorta

Question 28

• Pulmonary plexus:

Answer 28

Anterior and (mainly) posterior to the roots of the lungs

Question 29

• Oesophageal plexus:

Answer 29

Around the oesophagus

Question 30

CARDIAC PLEXUS

Answer 30

✓ 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

Question 31

PULMONARY PLEXUS

Answer 31

✓ Sympathetics from T2-4 → T2-4 ganglia | ✓ Parasympathetics from vagus

Question 32

PHRENIC NERVE

Answer 32

✓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

Question 33

INTERCOSTAL NERVES

Answer 33

✓ 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

Question 34

PANCOAST’S TUMOUR

Answer 34

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

Question 35

Horner’s syndrome

Answer 35

* Ptosis (drooping) of the upper eyelid • Pupillary constriction (miosis) * Anhydrosis (lack of sweating) * Flushing of the face