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– 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

Nolte Text, p. 267

Haines AtlasHaines Atlas

Haines Atlas, fig. 6-2

SERIAL SECTIONS

Haines Atlas

CLINCAL IMAGING vs. ANATOMYWHICH 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:

• Name• Location• Function• Dev. Divisions

MesenMetenMyelen

Nolte Fig. 15-3

Cranial Nerves

Medulla 9 - 12

Pons 5 - 8

Midbrain 3 & 4

Diencephalon 2

Telencephalon 1 (not pictured)

Spinal Cord 11

Cranial Nerves (CN’s)• HEAD AND NECK INNERVATION

• Components of CN’s:1) Sensory2) Special sensory3) Motor (2 embryological types of skeletal mm)4) 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 NERVENUCLEUS vs. GANGLION

• WITHIN CNS• CLUSTER OF NEURONS• NOT PSEUDOUNIPOLAR*• SENSORY OR MOTOR

• OUTSIDE OF CNS• CLUSTER OF NEURONS• PSEUDOUNIPOLAR• SENSORY

*except mesencephalic nucleus of V

Carpenter, Core Text of Neuroanatomy, 1991

SENSORY GANGLIA of CRANIAL NERVES

Langman’s EmbryologyCarpenter, 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 MOTORORGANIZATION

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

Langman’s Embryology

• 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

BRANCHIAL ARCHES (PHARYNGEAL ARCHES)

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

Langman’s Embryology

Gilman & Winans-Newman

Nolte Text, p. 376

Nolte Fig. 12-1

Special SensorySomatic SensoryVisceral Sensory

Visceral motorBranchial motorSomatic motor

Haines Atlas

G 5, 7, 9, 10 = skin + mucous mem. (prop. 3, 4, 6, 12)

SS 2, 8 = eye + ear

AG 9, 10 = int. organs

VS 7, 9, 10, 1 = taste, olf.

S G 12, 3, 4, 6 = tongue + eye mm (myotomes)E

G 3, 7, 9, 10 = parasymp.V

S 5, 7 ambig. = branchial mm