Download Neuroscience 1c – Brainstem and Crainial Nerves

Neuroscience 1c – Organisation of Brainstem and Cranial Nerves
Anil Chopra
1. With the aid of diagrams show the approximate position of the following
structures in the brainstem and state their function:
a. inferior medullary olive
b. substantia nigra
c. superior and inferior colliculi
d. reticular formation
e. nucleus coeruleus
2. Explain the origin and functions of cranial nerves III to XII
The brainstem is that part of the CNS that lies between the cerebrum and the spinal
cord. It consists of the midbrain the pons and the medulla oblongata.
Functional
component
General
somatic
afferent
Abbreviation General function
Cranial nerves containing component
GSA
Perception of touch, pain,
temperature
Trigeminal nerve [V]; facial nerve [VII]; vagus
nerve [X]
General
visceral
afferent
GVA
Sensory input from viscera
Glossopharyngeal nerve [IX]; vagus nerve [X]
Special
afferent*
SA
Smell, taste, vision, hearing
and balance
Olfactory nerve [I]; optic nerve [II]; facial nerve
[VII]; vestibulocochlear nerve [VIII];
glossopharyngeal nerve [IX]; vagus nerve [X]
General
somatic
efferent
GSE
Motor innervation to skeletal
(voluntary) muscles
Oculomotor nerve [III]; trochlear nerve [IV];
abducent nerve [VI]; hypoglossal nerve [XII]
General
visceral
efferent
GVE
Motor innervation to smooth
muscle, heart muscle, and
glands
Oculomotor nerve [III]; facial nerve [VII];
glossopharyngeal nerve [IX]; vagus nerve [X]
Branchial
efferent**
BE
Motor innervation to skeletal
muscles derived from
pharyngeal arch mesoderm
Trigeminal nerve [V]; facial nerve [VII];
glossopharyngeal nerve [IX]; vagus nerve [X];
accessory nerve [XI]
Classification of Nerves
Cranial Nerves
Components
Nerve
Afferent Efferent Exit from skull
Function
Olfactory nerve [I]
SA
Cribriform plate Smell
of ethmoid bone
Optic nerve [II]
SA
Optic canal
Vision
Oculomotor nerve
[III]
GSE,
GVE
Superior orbital
fissure
GSE-innervates levator palpebrae superioris, superior rectus, inferior
rectus, medial rectus, and inferior oblique muscles
GVE-innervates sphincter pupillae for pupillary constriction; ciliary
muscles for accommodation of the lens for near vision
Trochlear nerve [IV]
GSE
Superior orbital
fissure
Innervates superior oblique muscle
BE
Superior orbital
fissureophthalmic
division [V1]
Foramen
rotundummaxillary nerve
[V2]
Foramen ovalemandibular
division [V3]
GSA-sensory from: ophthalmic division [V1]-eyes, conjunctiva, orbital
contents, nasal cavity, frontal sinus, ethmoid sinus, upper eyelid,
dorsum of nose, anterior part of scalp; maxillary nerve [V2]-dura in
anterior and middle cranial fossae, nasopharynx, palate, nasal cavity,
upper teeth, maxillary sinus, skin covering the side of the nose, lower
eyelid, cheek, upper lip; mandibular division [V3]-skin of lower face,
cheek, lower lip, ear, external acoustic meatus, temporal fossa,
anterior two-thirds of tongue, lower teeth, mastoid air cells, mucous
membranes of cheek, mandible, dura in middle cranial fossa BEinnervates temporalis, masseter, medial and lateral pterygoids, tensor
tympani, tensor veli palatini, anterior belly of digastric, and mylohyoid
muscles
GSE
Superior orbital
fissure
Innervates lateral rectus muscle
Trigeminal nerve
[V]
GSA
Abducent nerve [VI]
Facial nerve [VII]
GSA, SA GVE,
BE
Internal acoustic GSA-sensory from external acoustic meatus, skin posterior to ear
meatus
SA-taste from anterior two-thirds of tongue
GVE-innervates lacrimal gland, submandibular and sublingual salivary
glands, and mucous membranes of nasal cavity, hard and soft palates
BE-innervates muscles of face (muscles of facial expression) and
scalp derived from the second pharyngeal arch, and stapedius,
posterior belly of digastric, stylohyoid muscles
Vestibulocochlear
nerve [VIII]
SA
Internal acoustic Vestibular division-balance
meatus
Cochlear division-hearing
Glossopharyngeal
nerve [IX]*
GVA, SA GVE,
BE
Jugular foramen GVA-sensory from carotid body and sinus, posterior one-third of
tongue, palatine tonsils, upper pharynx, and mucosa of middle ear and
pharyngotympanic tube
SA-taste from posterior one-third of tongue
GVE-innervates parotid salivary gland
BE-innervates stylopharyngeus muscle
Vagus nerve [X]*
GSA,
GVE,
GVA, SA BE
Jugular foramen GSA-sensory from skin posterior to ear and external acoustic meatus,
and dura in posterior cranial fossa
GVA-sensory from aortic body chemoreceptors and aortic arch
baroreceptors, mucous membranes of pharynx, larynx, esophagus,
bronchi, lungs, heart, and abdominal viscera of the foregut and midgut
SA-taste from the epiglottis
GVE-innervates smooth muscle and glands in the pharynx, larynx,
thoracic viscera, and abdominal viscera of the foregut and midgut
BE-innervates one tongue muscle (palatoglossus), muscles of soft
palate (except tensor veli palatini), pharynx (except stylopharyngeus),
and larynx
Accessory nerve
[XI]
BE
Jugular foramen Innervates sternocleidomastoid and trapezius muscles
Hypoglossal nerve
[XII]
GSE
Hypoglossal
canal
Innervates hyoglossus, genioglossus, and styloglossus muscles and
all intrinsic muscles of the tongue
Brainstem Nuclei
Fig 6.2
Fig 6.3
Fig 6.5
Fig 6.4
Fig 6.6
Fig 6.7
Fig 6.8




Middle cerebellar peduncle  pons: cortex => cerebellum
Substantia nigra  midbrain: control of movement with basal ganglia
Cerebral peduncle  midbrain: carries corticospinal & corticobulbar tracts from
cerebrum to pons
Inferior olivary nucleus  medulla: supplies proprioceptive input to the cerebellum
Functions of Brainstem
» is located anterior to the cerebellum to which it is connected by three pairs of
cerebellar peduncles
» It contains the following:
o The nuclei for 10 of the 12 cranial nerves (exceptions – olfactory and optic)
o Apparatus for controlling eye movement including cranial nerves III, IV and
VI
o Monoaminergic nuclei that project widely through the CNS
o Areas vital to the control of the CVS, respiration and the ANS
o Areas important in the control of consciousness
o Descending and ascending pathways lining the spinal cord to supraspinal
structures such as cerebral cortex and cerebellum
 Inferior Medullary Olive – Is in the medulla and receives inputs from a number
of sources and provides the climbing fibre input to the cerebellum
 Substantia Nigra – Is in the midbrain and contains both dopamine and γaminobutyric acid (GABA) neurones. It forms part of the basal ganglia and is
involved in the control of movement. Loss of dopaminergic neurones in this part
of the brain is the major pathological event in Parkinson’s disease
 Superior and Inferior Colliculi – The inferior coliculus is in the midbrain and is
part of the auditory system while the superior colliculus is involved with visual
processing and eye movement control.
 Reticular Formation – A loosely arranged network of cells in the brainstem that
are left when all the identified tracts and nuclei in the brainstem are removed.
Possibly a continuation of spinal cord interneurones. Cells use different
neurotransmitters - noradrenaline, 5-HT (5-hydroxytryptamine), ACh and
Dopamine transmitters depending on function of particular cells. There is a
sensory portion in the lower medulla and lower pons, and a motor portion in the
upper medulla and upper pons. The main function of the reticular formation is:
 Sleeping and waking – parts of the formation are involved in producing sleep
states and others in awakening mechanisms – the reticular activating system
bases on the noradrenergic system
 Modulation of sensory information across the thalamic relay nuclei – a role in
gating sensations such as pain
 Motor control via the modulation of spinal interneurons and transmitting
information to the cerebellum – the lateral parts of the formation
 Modulation of respiration
 Nucleus Coeruleus – One of the medial reticular nuclei connected with the
nucleus of the trigeminal nerve
 Other structures of note:
 The pyramid – which represents the descending corticospinal tract that
decussates at the lower border of the brainstem
 The cerebellar peduncles - which convey information to and from the
cerebellum
 The vestiblar nucleus - which has important connections from the ear and
projects to the spinal cord and cerebellum
 The periaqueductal grey matter – of the mesencephalon is an area rich in
opioids and thus important in supraspinal modulation of nociception
 The central aqueduct – running through the midbrain links the 3rd and 4th
ventricles
Raised intracranial pressure causes the medulla and cerebellar tonsils to be pushed
downward through the foramen magnum. This is characterised by headaches, neck
stiffness and paralysis of some cranial nerves. Patients with this condition should
never have a lumbar puncture as it may result in herniation of the brain through the
foramen magnum even further.
Thrombosis of vertebral or posterior inferior communicating artery can occur.
Symptoms include:
– Vertigo
– Ipsilateral cerebellar ataxia
– Ipsilateral loss of pain/thermal sense (face)
– Horner’s syndrome
– Hoarseness, difficulty in swallowing
– Contralateral loss of pain/thermal sense (trunk and limbs)
Relations to ventricles:
Lower Medulla: central canal
Upper Medulla: 4th Ventricle
Pons: 4th ventricle
Midbrain: aqueduct