Exam 1: Brainstem 3: Trigeminal complex and midbrain (slides repeated from previous lectures are included in those decks) Flashcards
Know and understand this chart
Know and understand this chart
On which neuron do the trigeminal nuclei (mesencephalic, chief, and spinal trigeminal) decussate, and where?
- The mesencephalic does not decussate!
- The chief decussates at the 2nd neuron in the trigeminal lemniscus
- The spinal trigeminal decussates at the 2nd neuron in the trigothalamic tract
Mesencephalic Trigeminal Nucleus:
- Here’s the exception: _____ _____ nucleus is located in the CNS/brainstem.
- Receive _____ input from muscles of mastication, tongue, extraocular muscles
- Clinical Relevance: Involved in _____ _____ reflex
Mesencephalic Trigeminal Nucleus:
- Here’s the exception: Primary sensory nucleus is located in the CNS/brainstem.
- Receive proprioceptive input from muscles of mastication, tongue, extraocular muscles
- Clinical Relevance: Involved in _jaw jerk reflex*_
- In this reflex, there are fibers that run from the mesencephalic nucleus DOWN to the pons to the MOTOR NUCLEUS of V (that ultimately innervate muscles of mastication via the mandibular division of V3)
- Other roles of this nucleus are “under investigation”
Trigeminal Pathways:
- The Spinal Sensory Trigeminal Pathway - mediating _____ touch, _____ and _____ information.
- The Main Sensory Trigeminal Pathway - a precisely topographically organized pathway mediating _____ tactile discrimination and _____
- The Mesencephalic Trigeminal System - monitoring _____ position and _____.
Trigeminal Pathways:
- The Spinal Sensory Trigeminal Pathway - mediating crude touch, pain and temperature information.
- The Main Sensory Trigeminal Pathway - a precisely topographically organized pathway mediating fine tactile discrimination and proprioception
- The Mesencephalic Trigeminal System - monitoring jaw position and movement.
Jaw Jerk Reflex:
- _____ induced in the lower jaw on _____ muscle with gentle tap on chin with reflex hammer
- Impulse travels to brainstem via _____ nerves
- Primary sensory neuronal cell body located in _____ (mostly) nucleus of trigeminal nerve
- _____ projections on motor nucleus of V trigger _____ reflexive movement of the _____ jaw
Jaw Jerk Reflex:
- Stretch induced in the lower jaw on masseter muscle with gentle tap on chin with reflex hammer
- Impulse travels to brainstem via mandibular nerves
- Primary sensory neuronal cell body located in mesencephalic (mostly) nucleus of trigeminal nerve (midbrain)
- Excitatory projections on motor nucleus of V trigger involuntary reflexive movement of the lower jaw
Corneal Reflex:
- Lightly touch cotton to front of patient’s eye (one eye only)
- Afferent axons carried by _____ branch of ___
- Sensory impulses travel both to _____ ganglia and _____ _____ ganglia
- From _____ _____ nucleus, signal travels to motor nucleus of _____ nerve
- Signal then travels to _____ _____ muscles in _____ eyes, resulting in blinking of _____ eye(s)
Corneal Reflex:
- Lightly touch cotton to front of patient’s eye (one eye only)
- Afferent axons carried by ophthalmic branch of V1
- Sensory impulses travel both to trigeminal ganglia and spinal trigeminal ganglia
- From spinal trigeminal nucleus, signal travels to motor nucleus of facial nerve (CNVII)
- Signal then travels to orbicularis oculi muscles in both eyes, resulting in blinking of both eyes
Corneal Reflex:
The corneal eye blink reflex is initiated by the _____ nerve endings in the cornea and involves the trigeminal nerve and ganglion, the spinal _____ tract and nucleus, interneurons in the _____ formation, motor neurons in the _____ nucleus and nerve, and the orbicularis oculi.
As the afferent information from each cornea is distributed ___laterally to facial motor neurons by the reticular formation interneurons, the eye blink response is _____,
Corneal Reflex:
The corneal eye blink reflex is initiated by the free nerve endings in the cornea and involves the trigeminal nerve and ganglion, the spinal trigeminal tract and nucleus, interneurons in the reticular formation, motor neurons in the facial nucleus and nerve, and the orbicularis oculi.
As the afferent information from each cornea is distributed bilaterally to facial motor neurons by the reticular formation interneurons, the eye blink response is consensual**, that is, **both eye lids will close to stimulation of the cornea of either eye.
Understand the origins of SA information originating on CN,s V, VII, IX, and X.
Distribution of general sensory GSA or SA information originating on CNs V (trigeminal), VII (facial), IX (glossopharyngeal), and X (vagus).
Some of these primary sensory fibers end in the principal sensory nucleus, but many form the spinal trigeminal tract and end in** the **spinal trigeminal nucleus.
Identify the region in the red box
The midbrain
What section of the brainstem is this?
Identify A, B, C and D
Caudal midbrain
A) Tectum
B) Tegmentum
C) Crus cerebri
D) Cerebral peduncle
Understand the structures and landmarks visible on the Midbrain: Gross, longitudinal section
Understand the structures and landmarks visible on the Midbrain: Gross, longitudinal section
Identify the structure or landmark
_Midbrain*_
*Midbrain part visible from this view: cerebral peduncles
Identify the structure or landmark
oculomotor nerve (CN III)
Cranial nerve nuclei in Midbrain:
• motor for ___ and ___
• _____ nucleus of V
• Edinger-Westphal nuclei (_____ nuclei associated with CN ___)
Cranial nerve nuclei in Midbrain:
• Cranial nerve nuclei motor for III and IV
• mesencephalic nucleus of V
• Edinger-Westphal nuclei (parasympathetic nuclei associated with CN III)
Functional Systems in Midbrain:
- Long tracts
- Cerebral aqueduct (conduit between?)
- _____ gray (PAG, tightly packed cell group surrounding the aqueduct)
- _____ formation
- Cerebral peduncles (_____ _____ + _____ _____)
Functional Systems in Midbrain:
- Long tracts (ascending, descending) (rubrospinal tract included here)
- Cerebral aqueduct (conduit between 3rd and 4th ventricles)
- Periaqueductal gray (PAG, tightly packed cell group surrounding the aqueduct)
- Reticular formation
- Cerebral peduncles (basis pedunculi + substantia nigra)
Superior colliculus: (rostral midbrain)
- center for visual reflexes (receives _____ inputs), connects to lateral geniculate body (_____) and _____ tract
- Nuclei: Which 2 nuclei?
Superior colliculus: (rostral midbrain)
- center for visual reflexes (receives retinal inputs), connects to lateral geniculate body (thalamus) and optic tract
- Nuclei: oculomotor (CN III, both GSE and GVE) and red nucleus (“rubro-”)
also found in Superior colliculus: (rostral midbrain)
- Substantia nigra (pars _____ and pars ______)
- Ventral tegmental area (_____ fibers that supply forebrain)
- Pretectal region (rostral to the superior colliculus; involved in _____ _____ reflex
also found in Superior colliculus: (rostral midbrain)
- Substantia nigra (pars compacta and pars reticulate)
- Ventral tegmental** area (**dopaminergic fibers that supply forebrain)
- Pretectal region (rostral to the superior colliculus; involved in pupillary light reflex
Inferior colliculus: (caudal midbrain)
- center for hearing, projects to medial geniculate body (thalamus)
- Lateral lemniscus carries inputs from pons
- Nuclei: Which 2 nuclei?
Inferior colliculus: (caudal midbrain)
- center for hearing, projects to medial geniculate body (thalamus)
- Lateral lemniscus carries inputs from pons
- Nuclei: mesencephalic nucleus of trigeminal, trochlear (CN IV; note axonal crossing and dorsal exit!)
also found in Inferior colliculus: (caudal midbrain)
- Brachium conjunctivum (decussation of _____ _____ _____)
- Substantia _____
also found in Inferior colliculus: (caudal midbrain)
- Brachium conjunctivum (decussation of superior cerebellar peduncles)
- Substantia nigra
What are the 2 unique things about the trochlear nerve in the brainstem compared to the other cranial nerves?
It decussates before it exits the midbrain!
and
It exits the posterior of the brainstem instead of the anterior
Identify the landmark or structure
What section of the brainstem is this?
(If lesion is ? the issues are ipsilateral_
(if lesion is ? the issues are contralateral)
Trochlear nerve
in the caudal midbrain
Identify the landmark or structure
What section of the brainstem is this?
inferior colliculus
in the caudal midbrain
Identify the landmark or structure
What section of the brainstem is this?
mesencephalic nucleus
in the caudal midbrain
Identify the landmark or structure
What section of the brainstem is this?
nucleus of trochlear nerve
in the caudal midbrain
Identify the landmark or structure
What section of the brainstem is this?
substantia nigra
in the caudal midbrain
Identify the landmark or structure
What section of the brainstem is this?
superior colliculus
in the rostral midbrain
Identify the landmark or structure
What section of the brainstem is this?
mesencephalic nucleus of trigeminal nerve
in the rostral midbrain
Identify the landmark or structure
What section of the brainstem is this?
nucleus of oculomotor nerve
in the rostral midbrain
Identify the landmark or structure
What section of the brainstem is this?
red nucleus
in the rostral midbrain
Identify the landmark or structure
What section of the brainstem is this?
substantia nigra
in the rostral midbrain
Identify the landmark or structure
What section of the brainstem is this?
oculomotor nerve
in the rostral midbrain
name the key arteries for the brainstem
and know what areas of the brainstem they supply
PCA
SCA
Basilar
AICA
PICA
Vertebral artery
