Cranial Nerves Flashcards
What are the purely sensory cranial nerves?
Olfactory, optic, vestibulocochlear
What are the purely motor cranial nerves?
Oculomotor, trochlear, aducens, accessory spinal, hypoglossal
What are the cranial nerves with mixed modalities?
Trigeminal, facial, golssopharyngeal, vagus
Where do cranial nerves provide motor and sensory innervation?
The head (exception is vagus nerve)
Where do the cranial nerves exit the cranial vault?
All exit anteriorly, except CN IV which exits posteriorly and CN VIII which exits laterally
What is each sensory or motor component associated with?
A streak of grey matter in the brain/brainstem which serves on function
What are motor components associated with?
Motor nuclei = groups of efferent nerve cells that send their axons into the cranial nerve
What are sensory components associated with?
Sensory nuclei = groups of nerve cells upon the sensory neurons of the cranial nerves synapse
Where are the soma of sensory nerve cells found?
In ganglia outside of the CNS
What is the only sensory modality that doesn’t synapse in the thalamus prior to reaching the cotex?
Olfactory nerve
Where is the nuclei origin of motor cranial nerves?
Near the midline = all emerge close to midline which reflect location of their nucleus
What are some features of the oculomotor nerve?
Somatic motor and parasympathetic
Relates to Edinger-Westphal and oculomotor nucleus
What muscles does the oculomotor nerve supply with sympathetic fibres?
Sphincter pupillae and ciliary muscles
What are some features of the trochlear nerve?
Somatic motor
Crosses midline
Nucleus in lower midbrain
What are some features of the abducens nerve?
Somatic motor
Located in the caudal pons
What are some features of the hypoglossal nerve?
Somatic motor
Located in the medulla
Where does the spinal accessory nerve originate?
From the cervical spinal cord
What are the functions of the trigeminal nerve?
Somatosensation of face
Proprioception associated with chewing
Motor = muscles of mastication, tensor tympani, mylohyoid, anterior belly of digastric, tensor veli palatini
What nuclei are associated with the trigeminal nerve?
Mesencephalic nucleus, pontine trigeminal nucleus, spinal nucleus, sensory nucleus, ventral trigeminothlamic tract
What are some features of the mesencephalic nucleus?
Carries proprioception info from chewing muscles
Located close to jaw
What is special about the mesencephalic nucleus?
Only site in CNS where cell bodies of primary afferent neurons live in the CNS
What information is the pontine trigeminal nucleus responsible for?
Discriminative touch and vibration
What information is the spinal nucleus responsible for?
Pain and temperature
What does the sensory nucleus of the trigeminal nerve form?
Long column of neuron that stretches from midbrain down to upper 2 segments of cervical spinal cord
How does the ventral spinothalamic tract allow bilateral representation of touch in the cortex?
Most fibres cross the midline but some don’t
What are the functions of the facial nerve?
Motor to muscles of facial expression
Parasympathetic to pterygopalatine and submandibular ganglia
Taste to anterior 2/3 tongue
What are the functions of the glossopharyngeal nerve?
Tactile sense, pain and temperature from tongue, Eustachian tube and upper pharynx
Taste to posterior 1/3 tongue
Parasympathetics to otic ganglion
Motor to stylopharyngeus
How many components does the facial nerve have?
3
What are the functions of the vagus nerve?
Tactile sense, pain and temperature form pharynx, larynx, trachea, oesophagus and viscera
Taste from epiglottis
Parasympathetic to ganglia of thoracic and abdominal viscera
Motor to striated muscle of pharynx and larynx
What nerve besides CN X contributes to the motor innervation of the striated muscle of the pharynx and larynx?
Spinal accessory nerve
What are the components of the glossopharyngeal nerve?
Gustatory nucleus, spinal trigeminal nucleus, inferior salivary nucleus, nucleus ambiguus
What are the components of the vagus nerve?
Dorsal nucleus, solitary tract, spinal trigeminal nucleus, nucleus ambiguus
What are the three complex cranial nerves?
Facial nerve, glossopharyngeal nerve and vagus nerve
What cranial nerves share the solitary nuclei?
CN VII, IX and X = taste and visceral sensory info
What cranial nerves share the superior and inferior salivary nuclei?
CN VII and X = parasympathetic efferents to ganglia of salivary glands and pterygopalatine ganglion
What cranial nerves share the nucleus ambiguus?
CN IX and X (and cranial part of XI) = motor efferents to muscles of pharynx, larynx and upper oesophagus
What is the corticobulbar tract?
Part of the pyramidal tract that is motor to cranial nerves = includes fibres to motor nuclei of CN V, VII, X and XII
How are the inputs from the corticobulbar tract to the facial nucleus organised?
Only bilateral to part of nucleus that controls upper part of face = only crossed input reaches part of nucleus that controls lower half of face
How is the motor input to the cranial nerves innervating extra-ocular muscles organised?
Complex interplay from frontal and parietal lobes, reticular formation, visual cortex and vestibular system
How is the input to cranial nerves containing parasympathetic efferents organised?
Input mainly from the hypothalamus whose efferents reach the preganglionic autonomic neurons both directly and via synapses in the reticular formation
What is the hypothalamus influenced by?
Physiological status and input from many brain regions
What is the reticular formation?
Network of loosely aggregated cells with cell bodies, axons and dendrites intermingling in the central core of the brainstem
What is the reticular formation distinct from?
Long pathways and specific distinct cell groups
What are the functions of the centres included in the reticular formation?
Integrate cranial nerve reflexes
Influence voluntary movement
Participate in conduction and modulation of pain
Regulate autonomic centres
Integrate some basic functions (e.g respiration)
Activates cerebral cortex
What is the reticular formation a major component of?
The ascending reticular activating system
