S6) Autonomic Innervation of the Head and Neck Flashcards
What is the autonomic nervous system?
The autonomic nervous system is the part of the peripheral nervous system that controls smooth muscle and glands
How is the ANS controlled?
Central control is from the hypothalamus
State 2 functions of the ANS
- Controls body functions not under conscious control
- Maintains and fine tunes internal environment (accelerator and brake)
State 2 target tissues of the ANS
- Smooth muscle
- Glands (lacrimal & salivary)
Describe the arrangement of neurones and ganglions in the ANS
What are the two types of autonomic outflow from the CNS?
- Sympathetic: ‘thoracolumbar outflow’
- Parasympathetic: ‘craniosacral outflow’
State the origins and location of cell bodies (nuclei) in the sympathetic nervous system
- Originates from T1 ‐ L2 segments of spinal cord
‐ Cell bodies are within lateral horn of grey matter of spinal cord
State the origins of cell bodies in the sympathetic nervous system for the head and neck structures
T1 - T2
Identify the ganglia involved in the sympathetic innervation of head & neck structures
Ganglia in cervical portion of sympathetic chain:
- Superior cervical ganglion
- Middle cervical ganglion (neck and chest structures)
Which structures do the post ganglionic sympathetic ganglia hitch-hike onto to innervate their effector tissues?
- Blood vessels e.g. ICA, ECA, opthalmic artery
- Branches of CN V (very distally)
Identify 4 effector tissues of the SNS in the structures of the head and neck
- Eye (dilator pupillae)
- Eye lid (superior tarsal muscle)
- Blood vessels
- Sweat glands
State 4 responses of the SNS in the head and neck structures
- Pupillary dilation
- Assists eyelid retraction
- Vaso‐constriction
- Stimulates sweating
Explain why carotid arteries and the lung apex are important anatomical relations to sympathetic nerves innervating head and neck
Pathology involving the apex of lung and internal carotid artery can cause autonomic dysfunction in the eye and face e.g. Horner’s syndrome
Horner’s syndrome can result from a pancoast tumour in the apex of the lung.
Identify 3 symptoms of this clinical condition
- Partial ptosis
- Miosis (constricted pupil)
- Anhidrosis
What is the most likely cause of Horner’s syndrome?
A pancoast tumour on the apex of the lung which impinges on the sympathetic chain
State the origins and location of cell bodies (nuclei) in the parasympathetic nervous system
- Cranial segment originates from 4 CN’s
‐ Sacral segment originates from S2 ‐ S4 (pelvic splanchnics)
‐ Cell bodies are in brainstem / within grey matter of sacral spinal cord
Parasympathetic preganglionic fibres for the head and neck structures arise from 4 nuclei in the brainstem.
Identify one
Edinger Westphal
State the 4 cranial nerves which are associated with the pre-ganglionic fibres of the PNS
- Oculomotor nerve (CN III)
- Facial nerve (CN VII)
- Glossopharyngeal nerve (CN IX)
- Vagus nerve (CN X)
State the 4 ganglia in the PNS innervation of head and neck structures
- Ciliary
- Submandibular
- Pterygopalatine
- Otic
Which cranial nerve fibre is associated with the post ganglionic parasympathetic nerve fibres in the head and neck?
Branches of trigeminal nerve (CN V)
Identify 4 effector tissues of the PNS in the head and neck
- Iris (sphincter pupillae) & ciliary muscles (controls lens)
- Lacrimal gland
- Mucosal glands (nasal/oral mucosa/ resp. tract)
- Salivary glands
State 3 responses of the PNS in the head and neck structures
- Constrict pupil
- Accommodation reflex (lens shape)
- Glandular (salivary and mucosal) secretions
Describe the anatomical course of CN III and the parasympathetic fibres from the brainstem via the ciliary ganglion
⇒ Preganglionic fibres emerge from EDW nuclei with CN III
⇒ Ciliary ganglion
⇒ Postganglionic fibres merge with CN Va
⇒ Acts on sphincter pupiliae & lens
in 8 steps, describe the pupillary light reflex for the left eye
⇒ Light in left pupil
⇒ Sensory afferent from left retina (CN II)
⇒ Some branches of CN II enter midbrain
⇒ Connection with EDW nuclei (left and right)
⇒ Preganglionic parasympathetic fibres leave brainstem
⇒ Fibres merge with CN III (left and right)
⇒ Fibres pass via ciliary ganglion
⇒ Postglangionic parasympathetic fibres reach sphincter pupillae
For the diagram below, explain the types of light reflexes one will observe:
- Left: direct light reflex
- Right: consensual light reflex
How does the facial nerve enter the cranial cavity from the brainstem?
Through the petrous temporal bone
Identify the two main branches of the facial nerve arising inside the petrous bone
- Greater petrosal nerve
- Chorda tympani nerve
Parasympathetics arising with CN VII have two associated parasympathetic ganglia.
Identify them
- Pterygopalatine ganglion
- Submandibular ganglion
In 5 steps, describe the anatomical course of CN VII and the parasympathetic fibres from the brainstem via the greater petrosal nerve and pterygopalatine ganglion
⇒ Preganglionic fibres emerge with CN VII
⇒ Pass through petrous temporal bone
⇒ At the geniculate region, greater petrosal nerve enters pterygopalatine fossa
⇒ Fibres reach pterygopalatine ganglion
⇒ Postganglionic fibres act on lacrimal, nasal & palatine glands
In 5 steps, describe the anatomical course of CN VII and the parasympathetic fibres from the brainstem via the chorda tympani nerve and submandibular ganglion
⇒ Preganglionic fibres emerge with CN VII
⇒ Pass through petrous temporal bone
⇒ Fibres join chorda tympani nerve & cross through middle ear cavity
⇒ Fibres exit via base of skull & reach submandibular ganglion
⇒ Post ganglionic fibres act on sublingual & submandibular glands
How does the glossopharyngeal nerve enter the cranial cavity?
Through the jugular foramen
In 6 steps, describe the anatomical course of CN IX and the parasympathetic fibres from the brainstem via the tympanic nerve and plexus
⇒ Preganglionic fibres emerge with CN IX
⇒ Pass through jugular foramen
⇒ Fibres join tympanic nerve & tympanic plexus
⇒ Fibres join lesser petrosal nerve & exit via foramen ovale
⇒ Fibres reach otic ganglion (in infratemporal fossa)
⇒ Postganglionic fibres then merge with CN Vc & act on parotid gland
In 4 steps, describe the anatomical course of CN X and the parasympathetic fibres from the brainstem to the respective effector tissues
⇒ Parasympathetic fibres emerge with CN X
⇒ Preganglionic fibres meets ganglion at or in target tissue
⇒ Postganglionic fibres act on smooth muscle and glands of GI & resp tract
⇒ Postganglionic fibres act on heart
Explain how Horner’s syndrome produces its characteristic symptom of partial ptosis
- Sympathetic innervation of superior tarsal muscle muscle stops
- Parasympathetic innervation of levator palpabrae superioris (through oculomotor nerve) still functions
- Eyelid retraction is present but cannot be assisted = partial ptosis
Explain how Horner’s syndrome produces its characteristic symptom of miosis
- Sympathetic innervation of dilator pupillae stops = pupils constrict
- Parasympathetic innervation of sphincter pupillae dominates = pupils constrict
