Brain Stem Overview and Cranial Nerve Nuclei Flashcards
What are the 3 main parts which make up the brainstem?
- Midbrain
- Pons
- Medulla
How many of the cranial nerves originate in the brainstem?
10 of the 12 (CN I and II)
Where do autonomics in the spinal cord tend to be located?
Lateral aspect of the horn
Where can you find the motor aspect in the brainstem (for muscles etc.)?
Ventral aspects of the horn
Where does somatic sensory information lie in relation to visceral sensory information in the spinal cord?
Dorsally (further out)
In the brain stem where does somatic motor and sensory as well as visceral motor and sensory information lie from medial to lateral?
Most medial: - Somatic motor - Visceral motor - Visceral sensory - Somatic sensory (most lateral) Central grey matter more horizontal
Where is the general somatic motor located?
Most medial aspect
What is located in the GSE?
Hypoglossal nucleus (innervates tongue)
What is locted in the SVE (visceral motor)?
Nucleus ambigous (swallowing, speech, HR control)
What is located in the GVE (autonomic motor)?
- Dorsal motor nucleus of vagus (GI and respiratory control)
- Inferior salvitory nucleus (CN IX)
What is located within the GVA (autonomic sensory)?
Solitary nucleus
- CV/resp
What is located in the SVA (autonomic sensory)?
Solitary nucleus
- Taste
What is located in the GSA and SSA (somatic sensory)?
- Spinal nucleus
- Vestibular nuclei
- Cochlear nuclei
What are the major tracts of the medulla?
- Corticospinal tract
- Medial lemniscus
- Medial longitudinal fasiculus
Where does the medial lemniscus originate?
Dorsal column nuclei
What information does the medial lemniscal pathway carry?
Conscious proprioception and vibratory stimuli to thalamus
A brainstem lesion in the medial lemniscus leads to loss of what?
Contralateral loss of joint proprioception
Where do ascending tracts of the medial longitudinal fasiculus originate?
From lateral, medial and superior vestibular nuclei and project to pons
Where do descending tracts of the medial longitudinal fasiculus originate?
From medial vestibular nuclei and project to cervical spinal cord (vestibulospinal cord)
What information do the medial longitudinal fasiculus fibres carry?
Information about head position sent to cranial nerves
What does the reticular formation control?
- Modulation of sensory transmission to cortex
- Regulation of motor activity
- Autonomic regulation
- Sleep wake cycle / emotional behavior
What does the nucleus gracilis and cuneatus control?
- Receive information from dorsal columns
- Transmit information on conscious proprioception and vibratory stimuli to thalamus
What does the spinal nucleus if CN V control?
Pain and temperature from the head
What does the major nuclei control?
- Hypoglossal
- Nucleus ambiguus
What are the major nuclei of the medulla?
- Reticular formation
- Nucleus gracilis and cuneatus
- Spinal nucleus of CNV
- Cochlear, vestibular nuclei
- Motor nuclei
What is the pons?
- The connection between the medulla and the midbrain
- Main attachment of cerebellum
What are the 2 regions of the pons?
- Basillar pons (ventral)
- Tegmentum (dorsal)
What are the ascending tracts of the pons?
- Medial lemniscus
- Medial longitudinal fasiculus (MLF)
- Spinothalamic
- Trigeminothalamic
WHat are the descending tracts of the pons?
- Corticospinal
- Corticobulbar
- Rubrospinal
- Tectospinal
What are the nuclei of the lower caudal pons?
- Abducens nucleus (CNVI)
- Fascial nerve (CNVII)
- Vestibular nuclei
- Olivary nucleus
- Salvitory nucleus
What does the abducens nerve innervate?
Lateral rectus muscle of the eye (side to side movement)
What does the facial nerve innervate?
Muscles controlling ipsilateral fascial expression
WHat does the vestibular nuclei receive inputs from?
Vestibular apparatus
What does the vestibular nuclei facilitate?
Extensor motor neurons
WHat does the olivary nucleus receive input from?
Cochlear nuclei
What does the olivary nucleus transmit?
Auditory signals to higher areas of the brainstem
What does the salvitory nucleus control?
Salvation reflex
What are the major nuclei of the upper (rostal) pons?
- Main sensory (trigeminal) nucleus
- Motor nucleus (CNV)
- Nucleus locus cerules
- Mesencephalic nucleus
What does the main sensory *trigeminal) nucleus transmit?
Somatosensory information from the head region to thalamus
What does the motor nucelus innervate?
Muscles controling mastication
What does the nucleus locus ceruleus project?
It projects to cerebral cortex and cerebellum
What does the mesencephalic nucleus control?
- Part of reflex jaw closing circuit
- Receives muscle spindle afferent from the jaw
What are the 3 anatomically distinct areas of the midbrain?
- Tectum (dorsal)
- Tegmentum (central)
- Crus cerebri (ventral)
What are the major tracts and nuclei of the midbrain?
- Inferior colliculus (IC)
- Superior colliculus (SC)
- Red Nucleus (RN)
- Substantia nigra (SN)
What does the trochlear nerve (CN IV) do?
Motor - rotates eye downward
What does the oculomotor (CN III) nerve do?
Motor - eye, pupil and lens movement
What does the abducens (CN VI) nerve do?
Lateral eye movement
What cranial nerves are contained in the midbrain?
- CN III: Oculomotor
- CN IV: Trochlear
What cranial nerves come out of the pons?
CN V - VIII
What does CN VIII (vestibulocochlear) nerve transmit?
Sensory - hearing and balance
What nerves come out of the medulla?
CN IX and X
What does the glossopharyngeal nerve transmit?
MIxed
- Speech, swallowing, salivation (parotid gland)
- BP (carotid sinus), blood gases (carotid body), taste, and sensory data from tongue and external ear
What does the spinal accessory nerve control?
Motor
- head movement - controls movement of certain neck muscles
A brainstem lesion will usually produce defects on what side?
Same side (ipsilateral)
What do the sympathetic nerves in the pupillary light reflex do?
Radial fibres of iris that dilate pupil and several extraocuar muscles of eyes
What do parasympathetic nerves of the pupillary light reflex do?
- Excite ciliary muscles that control focusing of eye lens
- Sphincter of iris that constricts pupil
Describe the pupillary light reflex?
- When light shone into eyes, the pupils constrict
- Light on 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
- In darkness reflex is inhibited leading to dilation of pupil
What is the ganglion that CN III synapses on to constrict the pupils?
Ciliary ganglia
What will a brainstem lesion cause?
Ipsilateral horner’s syndrome
What are the symptoms associated with Horner’s syndrome?
Occurs on one side of the face and is a combination of:
- Unilateral ptosis (drooping eyelid)
- Miosis (small pupil)
- Anhidrosis (lack of sweating)