Nerves of the Thorax Flashcards
What controls the ANS?
hypothalamus
Describe the functionality of organs that have dual innervation
- sympathetics and parasympathetics exert opposite effects
- but functionally complement each other
Examples of vessels supplied by only sympathetics
- blood vessels
- errector pili muscles
- sweat glands
What is the role of the ANS?
- maintains stable internal environment
- regulates visceral activity (circulation/respiration/excretion/reproduction)
- supplies smooth muscles
- supplies cardiac muscle
- supplies glands
- regulates body temperature
- fibres accompany general visceral afferent fibres
What is the structure of autonomic nerves?
- reach end organ with 2 neurons
- preganglionic neuron cell body is in grey matter of spinal cord
- myelinated axon
- postganglionic neuron is at an automatic ganglion
- unmyelinated axon
What is the role of the parasympathetic system?
- rest and digest to conserve energy
- slows breathing and HR
- reduces cardiac output and BP
- opens sphincters
- constricts pupils
- secretomotor to glands (sweat/lacrimal)
What is the only parasympathetic source of abdominal organs?
- vagus
- 10th cranial nerve
Describe the pathway of the vagus nerve from the skull
- leaves cranial cavity through jugular foramen
- descends between IJV and internal then carotid artery in the carotid sheath
Describe where the right and left vagus enters the thoracic cavity
- right vagus enters thoracic cavity between right subclavian and brachiocephalic vein
- left vagus enters thoracic cavity posterior to left brachiocephalic vein between sublcavian and common carotid arteries
What are the branches of the left and right vagus nerves?
- right vagus: recurrent largyngeal nerve that wraps around right subclavian artery
- left vagus gives off recurrent laryngeal nerve that wraps around aortic arch forming the aortopulmonary window
What do the recurrent laryngeal nerves supply?
- intrinsic laryngeal muscles (except cricothyroid)
- middle and inferior pharyngeal constrictor muscles
- sensory supply to the laryngeal cavity below the level of vocal folds
What is the role of the sympathetic system?
- fight or flight (uses energy)
- increases HR and strength of contraction
- dilates coronary arteries (indirectly by local metabolic factors)
- constricts peripheral arteries
- relaxes bronchial smooth muscles
- closes sphincters
- controls body temperature (blood vessels/sweat glands)
Where are preganglionic sympathetic cell bodies found?
intermediolateral grey matter horn of T1-L2 spinal cord segments
Where are postganglionic sympathetic cell bodies found?
paravertebral sympathetic ganglia:
- anterior to neck of ribs, lateral aspect of vertebral bodies
- interconnected and covered with parietal pleura
prevertebral sympathetic ganglia:
- around the origins of branches of abdominal aorta
Describe the divisions of cervical parasympathetic ganglia to the vertebrae
- superior cervical ganglia C1-4
- middle cervical ganglia C5-6
- inferior cervical ganglia C7-8
What is it called when T1 joins the inferior cervical ganglion?
- stellate ganglion
- cervicothoracic ganglion
Explain the pathway of the sympathetic system to supply the mid-body area
neuron can synapse in the sympathetic chain at its level, postganglionic axons pass in the GRC and joins T1-L2 spinal nerves to supply mid-body area
Explain the pathway of the sympathetic system to supply the head, neck and upper limbs
neuron can travel up sympathetic chain to synapse in cervical ganglia, post ganglionic axons pass in GRC and joins cervical spinal nerves to supply head, neck and upper limbs
Explain the pathway of the sympathetic system to supply the lower limbs
neuron can travel down sympathetic chain to synapse in lumbar/sacral ganglion, postganglionic axons pass in the GRC and join lumbar/sacral nerves to supply lower limbs
Explain the pathway of the sympathetic system to supply abdominal viscera
preganglionic branches pass through the sympathetic trunk without synapsing, travels in splanchnic nerves to the abdomen to synapse in a prevertebral ganglion to supply abdominal viscera
Different types of splanchnic nerves
Thoracic splanchnic nerves:
- greater splanchnic nerve T5-9
- lesser splanchnic nerve T10-11
- least splanchnic nerve T12
Lumbar splanchnic nerves T1-L2
Pelvic splanchnic nerves
Explain the pathway of sympathetic system to supply adrenal medulla
supplied directly, it is itself like a ganglion
What are the divisions of the sympathetic system for the different segments of the body?
- head T1-3
- upper limb T4-6
- thoracic and abdominal walls T1-12
- lower limbs T12-L2
What type of nerves are splanchnic nerves?
sympathetic
