6 Flashcards
(24 cards)
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
What is the pathway for the parasympathetic of CN 10?
- arise from dorsal motor
- go to CN 10
- goes to optic ganglion
- ends at salivary glands
- preganglionic fibres will meet ganglion in or at the target tissue
Target tissues are:
- mucosal glands in pharynx/larynx and smooth muscles of oesophagus and trachea
- smooth muscle and mucosal glands within rest of resp. And GI tract
- heart
How do pupillary light reflexes work?
- shine light in (ex. Left) eye
- optic nerve senses the light (sensory AFFERENT)
- communication from optic tract to brainstem telling how much light there is
- this info is relayed to Edinger Westphal nucleus on both sides
- pre-ganglionic parasympathetic fibres then bring back info through oculomotor nerve on BOTH eyes
- pre-ganglionic synapse at ciliary ganglion to become post-ganglionic
- reach sphincter pupillae muscle of the iris
- as a result, the pupils constrict
- direct light reflex: eye in which light is shone
- consensual light reflex: opposite eye
What two branches of CN 7 do the parasympathetic fibres hitch-hike on to get to the target tissues?
- Greater petrosal
- Chorda tympani
- both arise in petrous bone
What are the two associated parasympathetic ganglia of CN 7?
- Greater petrosal runs over foramen lacerum and goes to PTERYGOPALATINE GANGLIOn which is found in the PTERYGOPALATINE FOSSA
- post-ganglionic goes to lacrimal and mucosal glands
- Chorda tympani goes to SUBMANDIBULAR GANGLION which is found beneath the tongues
- innervates submandibular gland and carries taste to anterior 2/3 of tongue
- post-ganglionic parasympathetics then run with distal branches of the trigeminal (lingual nerve)
Describe the parasympathetic fibres of CN 9
-exits through jugular foramen with CN 9 but at this point, splits into a number of branches:
-tympanic nerve which supplies sensory to middle ear
-parasympathetic fibres run with the tympanic nerve initially (hitch-hike)
-then parasympathetics exit middle ear as lesser petrosal nerve
-synapses in otic ganglion (in infratemporal fossa)
-postganglionic parasympathetics then hitch-hike on branch of CN Vc (auriculotemporal)
-supply parotid gland
See diagram in session 6 lecture slide 25
What is exophthalmos?
Retraction of eyeballs
What is the difference between hyperthyroidism and Grave’s disease?
- hyperthyroidism is an umbrella term
- Grave’s disease is an autoimmune condition which causes hyperthyroidism, so you will have exophthalmos
Between which two layers does an extradural haemmorhage occur?
Inter table of periosteum and periosteal layer of dura
How can we treat an extradural haemorrhage?
- drain the blood
- go through layers of scalp but not periosteal layer of dura
