BRAINSTEM I Neuroscience 2005

LECTURE OVERVIEW Definition of Brainstem Brief Gross Orientation Brief Cross Sectional Anatomy Orientation Correlation of Gross and Cross Sectional Anatomy Composite List of Brainstem Structures Cranial Nerves (CN’s) Introduction Nucleus vs. Ganglion Organization / Classification Based on Embryology Spinal Cord vs. Brainstem Skeletal mm: Branchial Arch vs. Somite Myotome Correlation of Location and Function of CN’s

DIVISIONS of the BRAINSTEM Midbrain Pons Medulla (Terms “upper” and “lower” sometimes used)

LOCATION of BRAINSTEM Cranial Cavity CNS Begins caudally at FORAMEN MAGNUM Mostly infratentorial CNS Between spinal cord and diencephalon Carpenter, Core Text of Neuroanatomy, 1991

Brainstem in situ Nolte Text, p. 263

Grant’s Atlas of Anatomy

Median Saggital Plane Haines Atlas Haines Atlas Nolte Text, p. 267

Haines Atlas, fig. 6-2

SERIAL SECTIONS Haines Atlas

CLINCAL IMAGING vs. ANATOMY WHICH WAY IS UP? VENTRAL DORSAL Haines Atlas

CLASSICAL REPRESENTATIVE SECTIONS MEDULLA PONS MIDBRAIN Haines Atlas

Nolte Fig. 11-5

Nolte Fig. 11-6

Brainstem Structures: Nolte Fig. 15-3 Brainstem Structures: Name Location Function Dev. Divisions Mesen Meten Myelen

Cranial Nerves Telencephalon 1 Diencephalon 2 Midbrain 3 & 4 Pons (not pictured) Diencephalon 2 Midbrain 3 & 4 Pons 5 - 8 Medulla 9 - 12 Spinal Cord 11

Cranial Nerves (CN’s) HEAD AND NECK INNERVATION Components of CN’s: Sensory Special sensory Motor (2 embryological types of skeletal mm) Autonomic Motor: Parasympathetics (sm. mm, glds) - preganglionic - head to the transverse colon - where do the sympathetics to the head originate? Neurons of origin in: - NUCLEI - GANGLIA Clinical relevance: - localization of lesions - extent of damage / prognosis - difficult to treat

CRANIAL NERVE NUCLEUS vs. GANGLION OUTSIDE OF CNS CLUSTER OF NEURONS PSEUDOUNIPOLAR SENSORY WITHIN CNS CLUSTER OF NEURONS NOT PSEUDOUNIPOLAR* SENSORY OR MOTOR *except mesencephalic nucleus of V Carpenter, Core Text of Neuroanatomy, 1991

SENSORY GANGLIA of CRANIAL NERVES Langman’s Embryology Carpenter, Core Text of Neuroanatomy, 1991

Cranial Nerve Nuclei

“WORM DIAGRAMS” NOLTE HAINES ATLAS

CLASSIFICATION OF CRANIAL NERVES Based on: A. Function Motor Somatic (skel. mm) Visceral (sm. & card. mm & spec. skel. mm) Sensory Special Sensory B. Embryologically Derived Location Alar plate = sensory (lateral) Basal plate = motor (medial)

SENSORY and MOTOR ORGANIZATION Embryonic CNS Spinal Cord Brainstem Langman’s Embryology

SPINAL CORD (body) BRAINSTEM (head*) Motoneurons (EFF) : somatic motor (skel. mm) visceral motor (sm. & card. mm., glands) Sensory neurons (AFF): somatic sensory (skin, muscle, muc. mem., bone, and joint receptors) visceral sensory (viscera) Motoneurons (EFF): somatic motor (skel. mm) visceral motor (sm. &card. mm., glands) branchial motor (skel. mm) Sensory neurons (AFF): somatic sensory ( skin, muscle., muc. mem., bone, and joint receptors) visceral sensory (viscera) special visceral (taste, smell) special somatic (eye, ear) *vagus and accessory nn. also to body

Somatic vs. Branchiomeric Skeletal Muscle Somatic: from the myotomes (part of somites) extraocular mm = CN III, IV, VI tongue mm = CN XII Branchial: from branchial arch* musculature mm of mastication = CN V mm of facial expression = CN VII mm of the pharynx and larynx = CN’s IX, X, XI (ambiguus) *also referred to as “pharyngeal arch”

Pharyngeal Arches Pharyngeal = Visceral so skel. musc. from arches is a “special” kind of “visceral” muscle (SVE) The term Pharyngeal Arch is used interchangeably with Branchial Arch BRANCHIAL motor = SVE Langman’s Embryology

BRANCHIAL ARCHES (PHARYNGEAL ARCHES) Langman’s Embryology 1st = V musc. mast., ant. belly dig., mylohy., tensor tym., tensor palat. 2nd = VII musc. facial expr., stapedius, post. belly dig., stylohyoid, auricular 3rd = IX stylopharyngeus 4th = X Sup. Laryngeal Br. = cricothyroid, levator palat., pharyng. constr. ( 6th arch supplied by Recurrent Laryngeal Br. = intrinsic laryn. mm; also CN XI)

Langman’s Embryology Nolte Text, p. 376 Gilman & Winans-Newman

Special Sensory Somatic Sensory Visceral Sensory Visceral motor Branchial motor Somatic motor Nolte Fig. 12-1

Haines Atlas

S G 12, 3, 4, 6 = tongue + eye mm (myotomes) E G 5, 7, 9, 10 = skin + mucous mem. (prop. 3, 4, 6, 12) S S 2, 8 = eye + ear A G 9, 10 = int. organs V S 7, 9, 10, 1 = taste, olf. S G 12, 3, 4, 6 = tongue + eye mm (myotomes) E G 3, 7, 9, 10 = parasymp. S 5, 7 ambig. = branchial mm