cranial nerves Flashcards
what are the definitions of these terms:
- afferent
- efferent
- somatic
- visceral
Afferent = axons carrying nerve impulses towards the CNS –
- afferents are sensory
Efferent = axons carrying nerve impulses away from the CNS –
- efferents are motor
Somatic = EITHER sensory (afferent) innervation to skin or muscle
AND / OR motor (efferent) innervation to striated muscles
Visceral = sensory (afferent) or motor (efferent) innervation to visceral organs, glands, smooth muscle
- In the case of motor = autonomic (sometimes called visceromotor)
what is meant by special and general?
General = sensory and motor functions
- usual normal stuff
- spinal
Special = basically only for special functions such as hearing, taste
- cranial nerves have special functions
what is SSA?
Special Somatic Afferent -
- sensory information for the senses of hearing and balance
CN VIII
what is SVA?
Special Visceral Afferent -
- sensory for the sense of taste
CN VII, IX, X
what is SVE
Special Visceral Efferent -
-
motor innervation
- to striated muscles derived from the pharyngeal arches
- i.e. face, mouth, pharynx, larynx.
- to striated muscles derived from the pharyngeal arches
CN V, VII, IX, X, XI
(sometimes called branchiomotor nerves/neurons)
which muscles are derived from which pharyngeal arches?
1 - muscles of mastication
2 - muscles of facial expression, stylohyoid, posterior belly of digastric
3 - stylopharyngeus
4 - soft palate muscles
5 -
6 - muscles of larynx
how are the general (spinal) nerve associated in the spinal cord?
the spinal nerves are associated with columns
afferents :
- columns contain second order sensory neurons
- these are innervated by DRG afferents
- Columns are innervated by the GSA, GVA fibres which synapses with interneurons to continue the signal
efferents :
- columns contain lower motor neuron cell bodies
- these project to innervate
- skeletal muscles GSE
- autonomic nuclei GVE
- these project to innervate
what are the components of spinal nerves?
draw and label
Motor and autonomic join spinal nerves
- Sensory also
- GSA and GVA
- axon of the sensory neuron which synapses with DRG neurons
- these innervate second order sensory neurons - (which are in the columns?)
- connect to thalamus
how are the cranial nerve components arranged in the midbrain and hindbrain?
Cranial nerve components have columns of neurons in midbrain and hindbrain
GVA and SVA are merged into one column
all autonomic motor axons associated with CN are parasympathetic
which fibres contain lower motor neurons?
which fibres contain second order sensory neurons?
Fibres whose nuclei contain lower motor neurons :
- GSE
- GVE
Fibres whose nuclei contain second order sensory neurons :
- GVA
- SVA
- GSA
- SSA
draw the locations of the soma of the GSE cranial nerve nuclei
draw the locations of the soma of the GVE cranial nerve nuclei
draw the locations of the soma of the GVE cranial nerve nuclei
III
- involved in pupillary reflex
VII
- superior salivatory nucleus
- what projections ^
IX
- interior salivary nucleus
- what projections ^
X
- project to plexi – not ganglions
- to large parts of the body
draw the locations of the soma of the GVA and SVA cranial nerve nuclei
NTS receives innervation from primary afferent sensory neurons
- Contains cell bodies of second order sensory neurons
Visceral sensory division
- receive sensory information from afferents from IX and X
- includes blood pressure, stretch
Taste
- receive from afferents associated with CN VII IX X
draw the locations of the soma of the GSA cranial nerve nuclei
GSA cranial nerve nuclei receive innervation from primary afferent sensory neurons
- and contain cell bodies of second order sensory neurons
Only CN V
- 3 nuclei
draw the locations of the soma of the SSA cranial nerve nuclei
describe cranial nerve I
olfactory
- Not a true cranial nerve
- Just nerve tract
- Outgrowth of forebrain
describe cranial nerve II
optic
- Not true cranial nerve
- Just nerve tract
- Outgrowth of forebrain
- Joins retina with forebrain
describe cranial nerve III
oculomotor
-
GSE to most extrinsic eye muscles
- All but those innervated by IV and VI
- Also carries GVE (parasympathetic) to ciliary muscles and pupillary constrictor via the ciliary ganglion
how are the extrinsic eye muscles innervated?
- CN IV GSE to superior oblique eye muscle
- CN VI GSE to lateral rectus eye muscle
- CN III GSE to other extrinsic eye muscles
describe cranial nerve IV
trochlear
- GSE to superior oblique eye muscle
describe cranial nerve VI
abducens
- GSE to lateral rectus eye muscle
describe cranial nerve V
trigeminal
-
GSA
- sensation from face, mouth, nasal cavity, teeth, dura, anterior 2/3 tongue
- also carries CN VII to targets
- lacrimal nerve carries GVE facial nerve fibres to lacrimal gland
- lingual nerve carries parasympathetic facial nerve fibres to SL and SM salivary glands
- SVA fibres to tongue
-
GVE innervation
-
muscles derived from 1st pharyngeal arch
- mastication
- biting
- swallowing
-
muscles derived from 1st pharyngeal arch
-
SVE motor neurons in mandibular division innervate muscles
- tensor tympani
- dampens chewing sounds
- tensor velo palatini
- tenses soft palate and opens eustachian tube for swallowing
- tensor tympani
which facial muscles are involved in :
mastication
swallowing
describe cranial nerve VII
facial
-
SVA
- Taste from 2/3 anterior tongue and soft palate
- Neuron soma found in geniculate ganglion
- Central axons project to NTS
-
GVE preganglionic parasympathetic to :
- Oral / nasal mucosa & lacrimal glands
- Via pterygopalatine ganglion
- Sublingual and submandibular glands
- Via submandibular ganglion
- Oral / nasal mucosa & lacrimal glands
-
SVE
- To 2nd arch musculature - facial expression
describe cranial nerve VIII
vestibulocochlear
-
SSA
- Innervate organ of corti within cochlear
- Have soma in spiral ganglion
- Innervate vestibular canals
- Have some in vestibular ganglion (scarpa’s)
- Innervate organ of corti within cochlear
- The vestibulo cochlear nerve exits through petrous temporal bone through internal auditory meatus before entering brainstem with CN VII
describe cranial nerve IX
glossopharyngeal
-
SVA
- Taste to posterior 1/3 tongue
- Found in petrosal ganglion
- Central axons project to NTS
- To taste division
-
GVA
- To carotid sinus/body, post 1/3 tongue and pharynx
- Carotid sinus
- Measurement of blood pressure
- Blood-gas measurement
- Carotid sinus
- Found in petrosal ganglion
- Central axons project to NTS
- To taste visceral sensory division
- To carotid sinus/body, post 1/3 tongue and pharynx
-
GVE
- To parotid salivary gland (parasym)
- Are preganglionic parasympathetic fibres
- Have postganglionic fibres in otic ganglion
- To parotid salivary gland (parasym)
-
SVE
- To stylopharyngeus from nucleus ambiguus
- Muscle elevates pharynx for swallowing and gagging
- To stylopharyngeus from nucleus ambiguus
describe cranial nerve X
vagus
-
SVA
- taste to epiglottis
- afferents - cell body found in nodose ganglion
- terminate in NTS
-
GVA sensation –
- aortic body, larynx, pharynx, trachea, heart, lungs, gut etc
- Throughout the body
- Aortic arch
- Contains baroreceptors - blood pressure measurement
- Contains chemoreceptors - blood oxygen conc measurement
- afferents - cell body found in nodose ganglion
- terminate in NTS
-
GVE
- from dorsal motor nucleus to heart, and smooth muscle of bronchioles and gut
- preganglionic parasympathetic from dorsal motor nucleus of X to postganglionic neuron plexi in;
- heart, bronchioles of the lung, GI tract, pancreas etc.
-
SVE
- from nucleus ambiguus to pharynx and larynx.
describe cranial nerve XI
spinal accessory
- Motor roots at C1-C5 coalesce to form CN XI
- Enters skull through foramen magnum
- Emerges from jugular foramen
-
SVE
- SCM innervation and rotates head
- Sensory innervation of SCM = C2 spinal nerve
- Upper trapezius innervation
- Controls shoulder blades
- Sensory innervation = C3,4 spinal nerves
- SCM innervation and rotates head
describe cranial nerve XII
hypoglossal
-
GSE
- to intrinsic and extrinsic tongue musculature
- (not palatoglossus = X)
- to intrinsic and extrinsic tongue musculature
