Lectures 6 & 7 Cranial and spinal nerves, sympathetic trunk Flashcards
Motor fibres can be either?
Somatic efferent to voluntary muscles or autonomic (visceral efferent) to smooth muscles and glands.
The autonomic nervous system consists of?
Sympathetic and parasympathetic divisions.
Sensory nerves are either concerned with?
Special senses of sell, taste, vision, hearing and balance
Describe somatic motor nerves
Axons/fibres arise from neurons in either brain or spinal cord. These axons pass into peripheral nerves (usually nerves of mixed function) & via these nerves directly to the skeletal muscle that they innervate. There is no second cell body.
Describe autonomic nervous system
- Parasympathetic and sympathetic divisions
- Autonomic nerves are involved in: secretion from glands (secretomotor), smooth muscle contraction in blood vessels (vasomotor), internal organs, erector pili muscles.
- Many but not all organs have a dual sympathetic and parasympathetic supply with opposite effects - e.g. one stimulating and the other inhabiting.
Autonomic pathways involve which two neurons?
The neuron of origin in the brain or spinal cord and a second one in a peripheral ganglion e.g. in sympathetic trunk or one of the cranial parasympathetic ganglia e.g. pterygopalatine ganglion.
Define ‘ganglion’
Collection of nerve cell bodies outside the central nervous system
Define ‘preganglionic fibres’
Myelinated axons of autonomic nerves which have not undergone a second synapse. Called post-ganglionic after this synapsing. Post ganglionic fibres are usually unmyelinated.
Parasympathetic nerves leave the brainstem via FOUR cranial nerves:
- Oculomotor (CN3)
- Facial (CN7)
- Glossopharyngeal (CN9)
- Vagus (CN10)
- And via 2nd and 4th sacral spinal nerves
Preganglionic fibres from these nerves synapse in:
- Ciliary ganglion in orbit
- Pterygopalatine ganglion in pterygopalatine fossa
- Submandibular ganglion adjacent to submandibular salivary gland
- Otic ganglia just below foramen ovale
Describe ciliary ganglion
Parasympathetic fibres arise from oculomotor nerve
Describe pterygopalatine ganglion
Parasympathetic fibres arise from facial nerve
Describe submandibular ganglion
Parasympathetic fibres arise from facial nerve
Describe otic ganglia
Parasympathetic fibres arise from glossopharangeal nerve
Ciliary ganglion location?
Orbit
Pterygopalatine ganglion location
Pterygopalatine fossa
Submandibular ganglion location
Adjacent to submandibular salivary gland
Otic ganglion location
Just below foramen ovale
Ganglia receiving fibres from the vagus are in the thorax and abdomen.
True
Parasympathetic fibres are frequently transferred from the cranial nerves of origin to other cranial nerves (hitchhikers) via special connecting branches.
True
Sympathetic fibres are not hitchhikers.
False, they are great hitchhikers, and travel on both blood vessels (usually arteries) and/or branches of cranial nerves (more later).
What is the sympathetic trunk?
It is a chain of axons and ganglia situated along the sides of the vertebral bodies. It extends from cranial base to coccyx. In the neck, it is posterior to carotid sheath and anterior to vertebral transverse processes.
Sympathetic nerves arise from neurons in the?
Thoracic and upper lumbar spinal chord.
Preganglionic fibres of sympathetic nerves leave the spinal cord via ?
Mixed spinal nerves through gaps between the vertebrae called intervertebral foramen.
Define ‘mixed spinal nerves’
These are mixed because they also carry motor fibres leaving the spinal cord and sensory fibres passing into the spinal cord.
Mixed spinal nerves are connected to the sympathetic trunk in?
Thorax and upper lumbar regions via fine communicating branches, white rami.
White rami transmits ?
Preganglionic sympathetic fibres to the sympathetic trunk.
Where do preganglionic fibres synapse?
The preganglionic fibres synapse on neurons in the sympathetic ganglia somewhere in the sympathetic trunk, either adjacent to their point of exit from the spinal cord or at some other more distant ganglion.
Define post-ganglionic fibres
Axons derived from neurons in the sympathetic ganglia.
Where do post-ganglionic fibres go?
They either continue up the sympathetic trunk to supply head and neck or leave via grey rami and the mixed spinal nerves to supply trunk and limbs.
What are the three interconnected ganglia on the cervical part of the sympathetic trunk?
Cervicothoracic or stellate ganglion, middle cervical ganglion and superior cervical ganglion.
Describe sympathetic nerve supply to some neck structures
Two lower ganglia (cervicothoracic and middle) send branches which form plexuses on cervical blood vessels (e.g. thyroid artery).
Describe sympathetic supply to head and other neck structures
Upper ganglia (superior cervical ganglion) either
- Gives rise to branches which form plexuses on carotid arteries and their branches.
The sympathetic fibres on the arterial plexuses are then transmitted to cranial nerves in head or
- Sends branches to join the glossopharyngeal and vagus directly or pass to plexuses in the thorax (“hitchhikers”).
where do sympathetic fibres originate from?
Thoracic (T1-12) and upper lumbar (L1-2) spinal cord.
In _________________ as there is no sympathetic outflow from these regions.
Cervical (and sacral) regions there are only grey rami.
There is both a white ramus (to sympathetic trunk from mixed spinal nerve) and grey ramus (from sympathetic trunk to mixed spinal nerve) at?
Thoracic or upper lumbar vertebrae
Cranial nerves arise from?
Collections of nerve cell bodies called nuclei in the grey matter of the brain mostly.
How are grey and white matter defined?
Grey and white matter in the central nervous system are defined according to whether nerve cell bodies are present (grey matter) or not present (white matter). Both grey and white matter contain supporting cells and axons and dendrites.
Cranial nerves consist of axons of one or more of the following functions:
- Somatic motor (to voluntary muscles)
- Autonomic - sympathetic & parasympathetic
- Sensory
List the sensory ganglia of cranial nerves
- Trigeminal ganglion
- Geniculate ganglion
- Spiral and vestibular ganglia
- Superior and inferior ganglion
Trigeminal nerve has which ganglion?
Trigeminal ganglion, which is in trigeminal cave within dura covering posteromedial middle cranial fossa.
Facial nerve has which ganglion?
Geniculate ganglion which is in facial canal adjacent to middle and inner ear
Vestibulocochlear nerve has which ganglion?
Spiral and vestibular ganglia in inner ear.
Glossopharyngeal nerve has which ganglion?
2 sensory ganglia - superior and inferior in jugular foramen
Vagus nerve has which ganglia?
2 sensory ganglia - superior (jugular ganglion), inferior (nodose) ganglion (immediately below jugular foramen on underside of skull.
List the three divisions of the trigeminal nerve arising from the trigeminal ganglion
- Opthalmic - arises as a purely sensory nerve
- Maxillary - arises as a purely sensory nerve
- Mandibular - arises as a sensory and somatic otor nerve
Certain branches of all three divisions of trigeminal receive autonomic hitch-hikers
True
All three divisions have cutaneous branches which are involved in sensation of face and neck
False, face and scalp
Opthalmic division of the trigeminal is associated with?
Associated with the roof and upper lateral walls of the orbit.
Ophthalmic division of trigeminal is transmitted into the orbit via the?
Superior orbital fissure
List three main branches of opthalmic division of the trigeminal ganglion.
- Lacrimal (lateral)
- Frontal (central)
- Nasociliary (deep and medial)
Describe frontal branch of opthalmic division of trigeminal
- Cutaneous branches supratrochlear (more medial, smaller)
- Supraorbital (more lateral, larger, through supraorbital notch/foramen)
Describe nasociliary branch of the opthalmic division of the trigeminal ganglion
The anterior and posterior ethmoidal foramina for the branches to the ethmoid air cells should be identified on skulls.
Maxillary nerve is transmitted via ____ into ______.
Foramen rotundum, pterygopalatine fossa.
Maxillary sends sensory fibres which pass through foramen rotundum but do not synapse with what?
Pterygopalatine ganglion (this is a parasympathetic ganglion of the facial nerve).
Branches from the pterygopalatine ganglion contain a mixture of?
Autonomic and sensory fibres which supply nose, palate etc.
Maxillary enters orbit via the ?
Inferior orbital fissure
the terminal cutaneous branches of the maxillary nerve arising in the orbit are ________.
Infraorbital and zygomaticoorbital nerves.
Mandibular branch of trigeminal ganglion is associated with _____ and transmitted through ______.
Mastication and mandibular structures, foramen ovale
List the three parts of the mandibular branch of the trigeminal ganglion
- Mandibular trunk
- Anterior division of trunk
- Posterior division of trunk
Describe trunk part of mandibular branch of the trigeminal ganglion
- short segment just below foramen ovale
- Branches of trunk: meningeal branch, nerve to medial pterygoid (motor to medial pterygoid and tensor tympani and tensor palati).
Describe anterior division of mandibular trunk
- Mostly motor
- Branches to muscles of mastication, branches named according to muscles they supply (masseter, lateral pterygoid, deep temporal)
- Except sensory or lung buccal nerve which is sensory.
Buccinator has a motor supply from?
Facial nerve and may have sensory innervation from the long buccal nerve
Describe posterior division of trunk
Sensory except mylohyoid nerve (usually/ mostly motor).
Posterior division of trunk contains?
Cutaenous auriculotemporal nerve
Cutaneous auriculotemporal nerve arises as?
Arises as two roots which surround the middle meningeal artery. Also carries parasympathetic fibres of glossopharangeal origin to parotid.
Other branches of posterior division of trunk include?
- Inferior alveolar nerve
- Mylohyoid nerve
- Lingual nerve
- Chorda tympani (branch of facial nerve which hitch-hikes on lingual nerve to reach tongue)
- Mental nerve
Describe mental nerve
It is the cutaneous branch of inferior alveolar is deep to orbicularis oris and is usually not displayed in prosections. The bony superficial opening of the mental foramen should be recognised.
Identify cranial nerves outside the skull
- Glossopharyngeal
- Vagus
- Hypoglossal
- Spinal accessory
Describe glossopharyngeal nerve passage
Passes between mdidle and superior pharyngeal constrictors with stylopharyngeus muscle.
Describe vagus nerve passage
Close association with internal and common carotid and presence of branch - recurrent laryngeal nerve - in upper thorax
Describe hypoglossal nerve location
Deep to intermediate tendon of digastric
Describe spinal accessory nerve location
Between sternocleidomastoid and trapezius.
