Wk6 Cranial Nerves Flashcards
What is a nucleus?
Cell bodies of neurones with common functions clumping together (CNS)
What is a ganglion?
Collection of cell bodies of neurones with common functions (PNS)
What is a fibre tract/fasciculus?
A bundle of axons travelling within the CNS
What is a nerve/peripheral nerve?
Bundle of axons travelling in PNS
Peripheral nerves axons
axons are said to be mixed in that they carry electrical signals travelling in two opposite directions
Efferent or motor axons
have their cell bodies in nuclei (i.e. CNS) and their axons convey commands from the brain or spinal cord to skeletal muscles, smooth muscles or glands
Afférent or sensory axons
their cell bodies in dorsal root ganglia and convey sensory information from the body’s surfaces and visceral organs to the CNS (i.e. brain and spinal cord).
What are peripheral nerves split into?
Cranial nerves - those collections of peripheral nerves whose axons connect the brain to/and from targets structures of the head and neck region
Spinal or segmental nerves - axons of spinal or segmental nerves connect the spinal cord to/and from targets structures from all parts of the body apart from the head region.
General somatic afférent
General sensation
Fine touch, crude touch, pressure, pain, temperature
Special somatic afférent
Special sensation
Vision, smell, hearing and balance
General visceral afférent
Pain, temperature, general sensations from viscera
General somatic efferent
Somatic or voluntary
Supply skeletal muscles of the body (trunk and limbs)
General visceral efferent
Visceral or autonomic
Supply smooth muscles, cardiac muscle
Glands
Special visceral efferent or BE
Branchiomotor
Muscles derived from pharyngeal arches
Olfactory nerve (CNI)
distributed to the uppermost part of the nasal cavity and is concerned with smell; it contains only special sensation fibres. It reaches the nose via the cribriform plate of the ethmoid bone and fractures of the ethmoid involving the dura mater may be associated with leakage of CSF from the nose
Optic nerve (CNII)
a purely sensory nerve in that it carries signals from the retina of the eye to the brain. It projects to the brain in a particularly special way that enables each eye to supply the visual brain on both sides
Cranial nerves III, IV, VI
when taken together are known as nerves of oculomotion as they all innervate the extraocular muscles that move the eye. Understanding the anatomy of cranial nerve III, also known as the oculomotor nerve is of particular importance to any doctor and as such, all students are encouraged to familiarise themselves with its intricacies
Cranial nerve V
the trigeminal, is the great sensory nerve of the head and neck. It is divided into three divisions, namely, the ophthalmic, maxillary and mandibular nerves. The first two are entirely sensory but the mandibular nerve also contains motor fibres which innervate the muscles of mastication
Cranial Nerve VII
is a complex nerve as it contains motor, general & special sensory and parasympathetic fibres. In most literature, it is also called the facial nerve and this is unfortunately wrong and students need to be wary of this. Motor fibres of CNVII constitute the facial nerve and are distributed to muscles of facial expression as well as the posterior belly of digastrics, stylohyoid and stapedius muscles. Its general sensory fibres constitute the nervous intermedius (or middle nerve) and supply part of the external acoustic meatus and auricle. Special sensory fibres supply taste buds of the anterior two thirds of the tongue whilst parasympathetic fibres are widely distributed to the glands of the nose, palate and to the submandibular and sublingual salivary glands
Cranial nerve VIII
is the vestibuolochochlear nerve and is the nerve for hearing and equilibration (or balance). In the periphery, CNVIII has very close relations to CNVII
Cranial nerve IX
glossopharyngeal nerve
also contains four types of nerve fibres. Motor fibres supply the stylopharyngeus muscle, parasympathetic fibres innervate the parotid gland and fibres of special sensation innervate of the posterior third of the tongue. General sensory fibres are widely distributed to the pharynx and oropharyngeal isthmus, the dorsum of the palate, the auditory tube and associated structures, the mastoid antrum and mastoid cells. Finally, via its sinus nerve branch, it supplies the carotid sinus and carotid body that monitor blood pressure and arterial oxygen levels respectively
Cranial nerve X
Vagus nerve
has an enormous territory extending into the abdomen. In the head and neck it is sensory to the lower part of the pharynx, the airways and oesophagus. It provides general sensation, parasympathetic fibres and motor fibres to the lower parts of the pharynx (motor to all of the pharynx except stylopharyngeus), the larynx, trachea and oesophagus. In addition, it supplies all of the palate muscles except tensor veli palatine. It supplies taste fibres to taste buds associated with the epiglottis and is sensory to the external auditory meatus and back of the auricle
CNXI
Accessory nerve
has a cranial part and a spinal part. The cranial root is accessory to the vagus by providing part of its motor component. The spinal root of the nerve contains fibres from C2, C3 and C4. It innervates the sternocleidomastoid and trapezius muscles. Current evidence suggests that the spinal root contains both sensory and motor fibres
CNXII
Hypoglossal nerve
the motor supply to all of the muscles of the tongue with the exception of palatoglossus muscle. Some cervical spinal nerves from C1, C2 and C3 are looped onto the hypoglossal nerve forming the ansa cervicalis. These fibres are distributed to the strap muscles of the neck
Cranial nerve mnemonic NAMES
Oh - olfactory Oh - optic Oh - occulomotor To - trochlear Touch - trigeminal And - abducens Feel - facial A - vestibulocochlear Girls - glassopharynx Vagina - vagus Ah - accessory Heaven - hypoglossal
Cranial nerves sensory or motor or both
Some - sensory Say - sensory Marry - motor Money - motor But - both My - motor Brother - both Says - sensory Big - both Business - both Makes - motor Money - motor
