Brainstem Overview and Cranial Nerve Nuclei Flashcards
What is the brainstem
- Part of brain lying between spinal cord, cerebellum and cerebral hemisphere
What makes up the brainstem?
- medulla
- pons
- midbrain
What are the main brainstem structures?
- Nuclei for 10 of 12 pairs of cranial nerves
- Controls eye movements (3rd, 4th and 6th Cranial nerves
- Areas vital in the control of respiratory and cardiovascular systems
- Autonomics nervous system nuclei
- Several ascending and descending tracts connecting spinal cord to cerebral cortex and cerebellum
Describe the position of grey matter in the spinal cord vs the brainstem
Spinal cord = more vertical
Brain stem = more horizontal
What are the 7 main afferent input and efferent output pathways and their positioning in the brainstem?
- Special sensory afferent (SSA)
- General sensory afferent (GSA)
- General visceral afferent (GVA)
- Special visceral afferent (SVA)
- General visceral efferent (GVE)
- Special visceral efferent (SVE)
- General somatic efferent (GSE)
What is the arrangement of function in the brainstem of:
GSE
- GSE (somatic motor)
- Hypoglossal nucleus – innervates tongue
What is the arrangement of function in the brainstem of:
SVE
- SVE (visceral motor)
- Nucleus ambiguous
- Swallowing, speech, heart rate control
- Nucleus ambiguous
What is the arrangement of function in the brainstem of:
GVE
- GVE (autonomic motor)
- Dorsal motor nucleus of the vagus (CN X)
- GI and respiratory control
- Inferior salivatory nucleus (CN IX)
- Dorsal motor nucleus of the vagus (CN X)
What is the arrangement of function in the brainstem of:
GVA
- Solitary nucleus
- cardiovascular and respiratory
What is the arranagement of function in the brainstem of:
SVA
- Solitary nucleus
- Taste
What is the arranagement of function in the brainstem of:
GSA and SSA
- GSA and SSA (somatic sensory)
- Spinal nucleus
- Vestibular nuclei
- Vestibular nuclei
What are the three major tracts of the medulla?
- Corticospinal tract
- Medial meniscus
- Medial longitudnal fasiculus
Desribe the corticospinal tract in the brainstem
- Tract decussates just below the pyramids
- Controls voluntary movement
- Brainstem lesion leads to contralateral UMN paralysis
Describe the medial meniscus pathway in the medulla
- Originates from dorsal column nuclei
- Transmit information on about conscious proprioception and vibratory stimuli to thalamus
- Brainstem lesion leads to contralateral loss of joint proprioception
Describe the medial longitudnal fasiciculus in the medulla
- Ascending tracts originate from lateral, medial & superior vestibular nuclei and project to pons
- Information about head position sent to cranial nerves
- Descending fibres originate from medial vestibular nuclei and project to cervical spinal cord (vestibulospinal tract)
What are the major nuclei of the medulla?
- Reticular Formation
- Nucleus gracilis and cuneatus
- Spinal nucleus of CN V
- Cochlear, Vestibular nuclei
- Motor nuclei
What is the function of the reticular formation in the medulla?
- Modulation of sensory transmission to cortex
- Regulation of motor activity
- Autonomic regulation
- Sleep wake cycle/emotional behaviour
What is the function of the nucleus gracilis and cuneatus in the medulla?
- Receive information from dorsal columns
- Transmit information on conscious proprioception and vibratory stimuli to thalamus
What is the function of the spinal nucleus of CN V?
pain and temperature information from the head
What are the motor nuclei of the medulla?
hypoglossal
nucleus ambiguous
What are the main attachments of the pons?
- Connection between medulla and midbrain
- Main attachment of cerebellum
What are the two regions of the pons?
- Basilar pons (ventral)
- Tegmentum
What are the ascending tracts of the pons?
- Medical lemniscus
- Medial longitudinal fasciculus
- Spinothalamic
- Trigeminothalamic
What are the descending tracts of the pons?
- Corticospinal
- Corticobulbar
- Rubrospinal
- Tectospinal
What 4 cranial nerves emerge at the level of the pons?
- trigeminal
- abducens
- facial
- vastibulcochlear
What are the main nuclei of the lower (caudal pons)
- Abducens Nucleus (CN VI)
- Facial Nucleus (CN VII)
- Vestibular Nuclei
- Olivary Nucleus
- Salivatory Nucleus
What are the main nuclei of the upper (rostral) pons?
- Main Sensory (trigeminal) Nucleus (CN V)
- Motor Nucleus (CN V)
- Nucleus locus ceruleus
- Mesencephalic Nucleus
What is the function of the abducens nucleus?
- Innervates lateral rectus muscle of eye (side to side movement)
What is the function of the facial nucleus of the pons?
- Innervate muscles controlling ipsilateral facial expression
What is the function of the vestibular nucleus in the Pons?
- Inputs from vestibular apparatus
- Facilitate extensor motor neurons
What is the function of the olivary nucleus in the pons
- Input from cochlear nuclei
- Transmit auditory signals to higher areas of brainstem
What is the function of the salivartory nucleus in the pons?
- Salivation reflex
What is the function of the main sensory (trigeminal) nucleus in the pons?
- Transmission of somatosensory information from head region to thalamus
What is the function of the motor nucleus (CN V) in the pons
- Innervate muscles controlling mastication
What is the function of nucleus locus ceruleus in the pons?
- Projects to cerebral cortex and cerebellum
What is the function of the mesencephalic nucleus in the pons?
- Muscle spindle afferent form the jaw
- Part of reflex jaw closing circuit
Where is the midbrain located?
- Lies between pons and forebrain
What are the major tracts and nuclei of the midbrain?
- Inferior Colliculus (IC)
- Superior Colliculus (SC)
- Red Nucleus (RN)
- Substantia nigra (SN)
Highlight where each of the cranial nerves emerge from the brainstem and give their functions
What do brainstem lesions usually produce?
- A brainstem lesion will usually produce ipsilateral cranial nerve defects
What is the function of PSNS nerves in the pupillary light reflex?
What is the function of SNS nerves in the pupillary light reflex?
- Radial fibres of iris that dilate pupil and several extraocular muscles of eyes
What happens when light is shone into the eyes?
the pupil constricts
What happens when there is a light stimulation of the retina?
- stimulates optic nerve fibres that innervate pretectal nuclei
- Secondary impulses pass to Edinger-Westphal nucleus and back through parasympathetic nerves to constrict sphincter of iris
Summarise the main contents of the medulla oblongata in the brainstem
The caudal medulla contains the pyramids anteriorly (overlying the descending corticospinal and corticobulbar tracts) and the posterior columns posteriorly (overlying the ascending fasciculi gracilis and cuneatus). The rostral medulla contains the pyramids anteriorly, the olives laterally (overlying the inferior olivary nuclear complex), and the caudal part of the fourth ventricle and the inferior cerebellar peduncles posteriorly.
Summarise the main contents of the pons in the brainstem
The anterior, basal pons contains the transverse pontine fibres and the descending corticospinal and corticobulbar tracts. The fourth ventricle, middle cerebellar peduncles, and superior cerebellar peduncles comprise the posterior pons.
Summarise the contents of the midbrain in the brainstem
The cerebral peduncles form the anterior part of the midbrain. These contain the descending corticospinal and corticobulbar tracts. The inferior and superior colliculi mark the posterior surface of the caudal and rostral midbrain, respectively, and the cerebral aqueduct lies deep to the colliculi, connecting the third and fourth ventricles.
What are the main special senses
- olfaction, vision, taste, hearing and balance
What cranial nerves are purely sensory?
- I - olfactory
- II - optic
- VIII - vestibulocochlear
What cranial nerves are purely motor?
- III - oculomotor
- IV - trochlear
- VI - abducent
- XI - accessory
- XII - hypoglossal
What cranial nerves contain motor and sensory componentd?
- V - trigeminal
- VII - facial
- IX - glossopharyngeal
- X - vagus
