6 Flashcards
What are some features of the autonomic (visceral) nervous system?
- Part of the peripheral nervous system
- Central control is from hypothalamus
- controls body functions not under conscious control
- maintains and fine tunes internal environment; like an accelerator and brake
What are the two main components of the autonomic nervous system? How are ganglion involved?
- divided into sympathetic and parasympathetic components
- consists of preganglionic and postganglionic nerves
What are the usual target tissues of the ANS?
- smooth muscle: action is involuntary and frequently found in viscera
- smooth muscle in blood vessels
- glands (sweat, lacrimal, mucosal and salivary)
What is the difference between what the sympathetic and parasympathetic innervate?
Sympathetic
- smooth muscle of blood vessels, eye lid (tarsal muscle) and iris (dilator pupillae, which will dilate pupil)
- sweat glands
- Arrector pili muscles (hair follicles)
- decreases secretions from salivary and lacrimal glands (smaller volume but higher protein, so more viscous)
Parasympathetic
- smooth muscle of iris (sphincter pupillae) and muscle in ciliary body (controls thickness of lens)
- lacrimal glands (tears)
- salivary and mucosal glands
- smooth muscle of the respiratory and GI tract
Where in the spinal cord do the sympathetic and parasympathetic nerves arise from?
Sympathetic
- thoracolumbar outflow
- segments T1-L2 of spinal cord only
- cell bodies within lateral horn of grey matter of spinal cord
Parasympathetic
- craniosacral outflow
- Cranial (four cranial nerves): supplies parasympathetic innervation to head and neck, thorax and abd
- Sacral (S2-S4): pelvic splanchnics
Name the collective name of the top 3 ganglion of the sympathetic chain, and their individual names
- Collectively known as cervical ganglion
- Superior cervical ganglion (most important)
- middle cervical ganglion
- inferior cervical ganglion
Explain how sympathetic outflow to head and neck works
- nerves to head and neck region arise from T1/T2 spinal segments
- preganglionic fibres ascend from thorax, up the sympathetic chain
- they synapse with one of the cervical ganglia, mainly superior and middle
- postganglionic then follow common carotid into the external and internal carotid arteries
- they HITCH-HIKE onto the blood vessels
- follow internal carotid to supply the eye (through opthalmic artery)
- follow external carotid to supply sweat glands and vessels
How do the common carotid arteries and the lung apex relate to sympathetic nerves innervating head and neck, especially in pathology?
- patient will usually present with Horner’s syndrome
- partial ptosis, anhydrosis, miosis
- pathology involving apex of lung and common carotid artery and its branches can cause autonomic dysfunction in the eye and face
- may involve pancoast tumour
What is a pancoast tumour?
-tumour that occurs in the apex of the lung
What is Horner’s syndrome?
- involves partial ptosis, miosis and anhydrosis
- partial ptosis: partial drooping of eyelid, not complete because levator papillary superioris is helping to elevated it
- miosis: constriction of pupil
- anhydrosis: lack of sweating
Which cranial nerves “carry” parasympathetic fibres from the brainstem?
-CN 3, 7, 9, 10
Oculomotor, facial, glossopharyngeal, vagus
Describe the general pathway of parasympathetic innervation to head and neck
Rule of 4s
- Arise from brainstem from parasympathetic nuclei
- hitch-hike on to one of 4 CNs
- parasympathetic ganglia (4)
- hitch hike on to branches of CN V (trigeminal, very short distance; exception is CN x)
- goes to target tissues
- none of these CNs carry sympathetic fibres, those come from a different route
- postganglionic fibres travel and hitch-hike on branches of trigeminal nerve (is a short route)
What is the pathway for the parasympathetic innervation of CN 3?
- Arise from Edinger Westphal
- goes to CN 3
- goes to ciliary ganglia
- hitch hikes on CN Va
- goes to smooth muscle (sphincter pupillae: constricts pupil) and (ciliary muscle: controls and alters shape of lens)
- parasympathetic fibres run OUTSIDE of oculomotor nerve
What is the pathway for the parasympathetic through CN 7?
- arise from superior salivary
- goes to CN 7
- goes to submandibular ganglion
- goes to CN V branches
- ends at lacrimal gland
What is the pathway for the parasympathetic of CN 9?
- arises from inferior salivary
- goes to CN 9
- goes to pterygopalatine ganglia
- hitch hikes on CN V branches
- ends at mucosal gland in nasal/oral mucosa/resp. Tract
