Anatomy of the Nerves of the Thorax

Where does the phrenic nerve originate?

C3, C4, C5

What thoracic structures are innervated by the phrenic nerve?

diaphragmatic, parietal and mediastinal pleura

Describe the anatomical path of the phrenic nerve:

courses anteriorly to the root of the lung

Describe the anatomical path of the left vagus nerve:

courses posteriorly to the root of the lung

Describe the anatomical path of the right vagus nerve:

courses over the brachiocephalic branch posterior to the lung

What is the name of the nerve branch of the vagus that innervates the larynx muscles?

recurrent laryngeal muscles

What structure does the vagus nerve arch over?

the arch of the aorta

What does the recurrent laryngeal nerve innervate?

The larynx below the vocal cords & the trachea.

Where are sympathetic chains found?

running parallel to vertebral bodies

What nerves branch off the sympathetic chain, innervating intercostal muscles and costal pleura?

intercostal muscles

Are intercostal muscles somatic or autonomic?

somatic

What are the 2 main branches of the nervous system?

central and peripheral

What makes up the CNS?

brain and spinal cord

What makes up the PNS?

cranial and spinal nerves

What are the two branches of the peripheral nervous system?

somatic and autonomic

What does the somatic nervous system do?

controls voluntary movements (body wall)

What does the autonomic nervous system do?

controls involuntary actions (internal activities of viscera)

What are the two branches of the autonomic nervous system?

sympathetic and parasympathetic

What is the role of the sympathetic nervous system?

arousal

What is the role of the parasympathetic nervous system?

relaxation

What is the usual sensory input in the sympathetic nervous system?

input from nociceptors

What are nociceptors?

pain receptors

What are afferent fibres?

Sensory fibres (arriving at the CNS)

What are efferent fibres?

Motor fibres (exiting the CNS)

How many segments are in the spinal cord?

31

Give the 5 groupings of spinal cord segments in superior to inferior order:

1) cervical

2) thoracic

3) lumbar

4) sacral

5) coccygeal

How many pairs of cervical spine nerves are there?

8

How many pairs of thoracic spine nerves are there?

12

How many pairs of lumbar spine nerves are there?

5

How many pairs of sacral spine nerves are there?

5

How many pairs of coccygeal spine nerves are there?

1

Is the dorsal root sensory or motor?

sensory

Is the ventral root sensory or motor?

motor

What is the name of branches of the dorsal root from vertebrae?

dorsal rami

What is the name of the branches that arise from ventral roots off vertebrae?

ventral rami

How many neurones are found in efferent autonomic pathways?

2

What is the name of the first neurones in the efferent autonomic pathway?

preganglionic neurone

What is the name of the second neurones in the efferent autonomic pathway?

postganglionic neurone

In the parasympathetic nervous system, which is longer: the pre or postganglionic neurone?

preganglionic neurone

What is the main nerve of the parasympathetic branch?

vagus nerve

Where does the vagus nerve originate from?

the medulla

Where do preganglionic fibres of the sympathetic branch arise from?

T1-L2

Describe the general pathway of efferent sympathetic fibres:

they run from T1-L2 into the sympathetic chain before being distributed across the body

What is the name of the structure that allows all electrical activity from T1-L2 to pass into the sympathetic chain?

white ramus communicans

True or false: the white ramus communicans is myelinated

true

True or false: the sympathetic chain can be used as a ladder to reach other nerves

true

Describe how sympathetic nerves innervate the body wall via the sympathetic chain pathway:

action potentials pass from the spinal cord into the sympathetic chain via the white ramus communicans before moving out into the dorsal and ventral ramus via grey ramus communicans

Where do heart sympathetic fibres arise from?

T1-T4

Where do lung sympathetic fibres arise from?

T2-T5

Where do oesophagus sympathetic fibres arise from?

T4-T6

What is the name of the region where sympathetic and parasympathetic nerves meet at the base of the heart?

cardiac plexus

What is the name of the region where sympathetic and parasympathetic nerves meet at the lungs?

pulmonary plexus

What nerve parasympathetically innervates the heart, lungs and oesophagus?

vagus

Where do intercostal nerves arise from?

T1-T11

Where do subcostal nerves arise from?

T12

What 4 things do intercostal nerves innervate?

1) intercostal muscles

2) some skin

3) costal pleura

4) cervical pleura

Describe why the vagus nerve is not exclusively autonomic:

it contains the recurrent laryngeal branch which is somatic

What is referred pain?

pain felt in a part of the body other than its actual source

Describe why heart pain is often referred to the upper limbs:

visceral pain courses back to the CNS via sympathetic fibres arising from T1-T4 which associate with both the heart and the dermatome of upper limbs

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