Brainstem
description
Transcript of Brainstem
Brainstem
David A. Morton, Ph.D.Jan 10th, 2013
Midbrain and Pons
Objectives• Explain how spinal nerves differ from cranial nerves• Name all the cranial nerves and know their components and functions• Identify and locate the CN’s associated with the medulla, pons and midbrain• Recognize the major internal and external landmarks on the dorsal and ventral
surface of the brain stem, so that you can determine if a gross or stained cross section is medulla, pons or midbrain.
• Identify on a typical cross section all the brain stem nuclei containing motor neurons that end on striated muscle.
• List the cranial nerves that contain parasympathetic fibers, the location of their nuclei, and their function
• Explain why cranial nerves are so important in localizing lesions.• Name reflexes that test these nerves and brain stem levels.• Relate branches of the vertebrobasilar blood supply to the medulla and pons
explaining the deficits that would occur with vascular occlusion.
Directional terms with Brain
CN I – Olfactory nerve
Cranial nerve overview
CN II – Optic nerve
Cranial nerve overview
CN III – Oculomotor nerve
Cranial nerve overview
CN IV – Trochlear nerve
Cranial nerve overview
CN V – Trigeminal nerve
Cranial nerve overview
CN VI – Abducens nerve
Cranial nerve overview
CN VII – Facial nerve
Cranial nerve overview
CN VIII – Vestibulocochlear nerve
Cranial nerve overview
CN IX – Glossopharyngeal nerve
Cranial nerve overview
CN X – Vagus nerve
Cranial nerve overview
CN XI – Spinal accessory nerve
Cranial nerve overview
CN XII – Hypoglossal nerve
Cranial nerve overview
Brainstem
• Midbrain
• Pons
• Medulla
Brain Overview
Medulla
Pons
Midbrain
Diencephalon
• Thalamus
• Hypothalamus
• Pineal gland
Brain Overview
PHTh
Th
• Corpus callosum
• Lateral ventricle
• 3rd ventricle
• Cerebral aqueduct
• 4th ventricle
Brain Overview
4
Corpus callosum
3
LV
aq
Spinal Cord and Spinal Nerve Review
Alar
Basal
Sulcus limitans
Spinal cord
Som S
VS
VM
SM
Spinal nerve anatomy
• Dorsal root
• Somatic sensory neurons
• Visceral sensory neurons
• Ventral root
• Visceral motor neurons
• Somatic motor neurons
Internal anatomy of brainstem
Alar
Basal
Sulcus limitans
Spinal cord
Som S
VS
VM
SM
Alar
Basal
Sulcus limitans
Medulla
Som S
VSVM
SMBM
The fate of the alar and basal laminae
• Why are brain stem sensory nuclei lateral
to motor nuclei in brainstem?
External anatomy:
• Quadrigeminal plate
• Superior colliculus
• Inferior colliculus
• Cerebral peduncles
• CN IV
Midbrain (mesencephalon)
SC
CPIC
IV
Dorsal view of brainstem
External anatomy:
• Quadrigeminal plate
• Superior colliculus
• Inferior colliculus
• Cerebral peduncles
• CN III (arrows)
Midbrain (mesencephalon)
Rostral midbrain
Caudal midbrain
SC
IC
CP
CP
Dorsal view of midbrain
CP
Ventral
Ventral
Cranial nerve nuclei
• Rostral midbrain
• Oculomotor nucleus
• Edinger-Westphal nucleus
• Caudal midbrain
• Trochlear nucleus
Oculomotor nucleus
Edinger-Westphal nucleus
Trochlear nucleus
Midbrain
MotorSensory
Internal anatomy
• Tectum
• Tegmentum
• Central gray matter
• Red nucleus
• Substantia nigra
• Cerebral peduncles
Midbrain (Rostral)
Subs
tantia n
igra
Cere
bral
pedu
ncle
Aq
Tectum
Tegmentum
Rn
Rostral midbrain
Internal anatomy
• Oculomotor nucleus
• Edinger-Westphal nucleus
Midbrain (Rostral)
Subs
tantia n
igra
Cere
bral
pedu
ncle
Aq
Rostral midbrain
Internal anatomy
• Trochlear nucleus
Midbrain (Caudal)
Caudal midbrain
Horizontal section
Red nucleus
Substantia nigra
Functional significance of midbrain:
• Visual and auditory reflexes
• Coordinates eye movements
• Pupillary reflex
• Consciousness and arousal (RAS)
Midbrain
Arterial supply. Branches off the:
• Posterior cerebral artery
• Basilar artery
Midbrain
Pupi
llary
and
Acc
omm
odati
on R
eflex
es
CN II
Bilateral contraction of sphincter pupillae and
ciliary muscles
CN III
External anatomy:
• Basilar pons (pons proper)
• Middle cerebellar peduncle (MC)
• Basilar artery
• 4th ventricle
• CNN V, VI, VII, VIII
Pons
MC
V
VI VIIVIII
Pons
4th vent.
Horizontal section
MC
4th
4th
Cranial nerve nuclei
• Rostral Pons
• Trigeminal nucleus
• Caudal Pons
• Abducens nucleus
• Facial nucleus
• Sup salivatory nucleus
Trigeminal nucleus
Facial nucleus
Abducens nucleus
Pons
MotorSensory
Sup salivatory nucleus
4th Ventricle
Motor nucleus of V
TegmentumR.F.
Pons Proper
Axons of the sensory part of V
Axons of the motorpart of V
Pons (Rostral/Mid)
Internal anatomy
• Trigeminal motor nucleus
• Functional significance
Pons (caudal)
Facial nucleus
• Branchial motor nucleus
• Innervate muscles of face
Pons (caudal)
Superior salivatory nucleus
• Visceral motor (Para)
• Origin of preganglionic
parasympathetic neurons
Pons (caudal)
Abducens nucleus
• Origin of Abducens n. (CN VI)
• Homolog to ventral horn
Pons (caudal)
Internal anatomy
• Facial nucleus
• Superior salivatory nucleus
• Abducens nucleus
Corneal reflex
Spinal trigem. Nucleus & Tract
• Consensual reflex
• Sensory: CN V-1 to spinal trigeminal nucleus
• Motor: Facial nucleus out to the temporal branch of CN VII
Corneal ReflexSemilunar ganglion
of CN V
CN V-1
L R
Spinal trigeminal nucleus
Touch the cornea
Blink(Orbicularis occuli muscle)
Facial motor nucleus
Temporal branch of CN VII
Pons
Arterial supply. Branches off the:
• Basilar artery
• Median and Circumferential
branches
Match the following reflexes with their associated brainstem level:
a. corneal reflex testing?
b. Gag reflex testing?
c. pupillary light reflex testing?
I II III
Match the following reflexes with their associated brainstem level:
a. corneal reflex testing?
b. Gag reflex testing?
c. pupillary light reflex testing?
I
II
III
You have a patient who cannot look to the right with the right eye or smile or wrinkle
the right side of their face. Characterize the lesion as to level, side, structure(s) involved.
You have a patient who cannot look to the right with the right eye or smile or wrinkle
the right side of their face. Characterize the lesion as to level, side, structure(s) involved.
What reflex would be abnormal in a patient with a lesion that included the circled area?
What reflex would be abnormal in a patient with a lesion that included the circled area?
Abducens nucleus
Facial nucleus