Brain Stem Anatomi

7/28/2019 Brain Stem Anatomi

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Brainstem & Cranial Nerves

Maryann Martone, Ph. D.

NEU 256

October 13, 2005


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Review: Levels of the Spinal Cord


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Ventricles in brainstem

Mesencephalon cerebral aqueduct

Metencephalon 4th ventricle

Mylencephalon 4th ventricle


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vermis

Occipital

LobeThalamus

Corpus callosum

Hypothalamus

Fornix

Anterior

commissure

Optic nerve

4th ventricle

Posterior commissure

pyramid

Mammillary body

Quadrigeminal

cistern


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internal capsulebasal ganglia

optic nerveoptic tract

hypothalamusmammillary body

cerebral peduncle

interpeduncular fossa

flocculus

inferior olivary

nuclear complex

cerebellum

cerebellar tonsil

pyramid

pyramidal decussation

pons

optic chiasm

Anterior view of brainstem


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optic tract

optic nerve

hypothalamus

optic chiasm

middle cerebellar peduncle

trigeminal nerve

vestibulocochlear nerve

flocculus

cuneate tubercle

inferior olivary nuclear complex

anterior median fissure pyramid

pons

cerebral

peduncle

Lateral view of brainstem


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Middle cerebellar

peduncle

Superior colliculus

Inferior colliculusCerebral

peduncle

Superior cerebellar

peduncle

Inferior cerebellar

peduncle

Medulla

4th ventricle

Posterior view of brainstem


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Components of the brainstem

Sensory ascending pathways (dorsal)

Motor descending pathways (ventral)

Cerebellar pathways Cranial nerve sensory and motor tracts

CPGs: rhythmic chewing, respiration,cardiovascular regulation & gain adjustments

for reflexes Modulatory systems: locus coeruleus, raphe

& substantia nigra


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Ascending sensory pathways

Fine discriminitive touch, conscious proprioception

Fasciculus gracilis: Terminates in the nucleus gracilis (medulla) Fasciculus cuneatus: Terminates (medulla) in the cuneate and

accessory cuneate nuclei

Sensations ofpain and temperature

Lateral Spinothalamic Tract origin dorsal horn cells of the gray matter

Fibers cross contralaterally through the anterior commissure andascend to the VPL nucleus

Transmits sensations oftouch

Ventral Spinothalamic Tract

origin cells of the posterior horn

Fibers cross to the opposite side in the anterior commissure


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Descending motor pathways

Voluntary movement

Lateral Corticospinal Tract Originates in large pyramidal cells (precentral gyrus)

cross to the opposite side of the cord at the pyramidal decussation &terminate in the dorsal horn cells

Ventral Corticospinal Tract

Originates in the pyramidal cells (motor area of the cortex)

Impulses related to equilibrium and antigravity reflexes

Vestibulospinal Tract

Fibers originate in the vestibular nuclei of the medulla and terminate

at level of the sacral spinal nerves

Connects vestibular complex and head and eye movementcoordination center in medulla

Medial Longitudinal Fasciculus

Contains both ascending and descending fibers


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Motor HierarchyLateral group (extremities;

fine motor control)

Corticospinal tract

Rubrospinal tract

Medial group (axialmusculature; rhythmic and

postural movements)

Vestibulospinal tract

Tectospinal tract

Reticulospinal tract

Final common path:

motor pool


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Reticular Formation

Core of brainstem(midbrain, pons and medulla)composed of looselyorganized neurons, outside of

the major nuclear groups ofthe brainstem.

Medial-to-lateral: raphenuclei, gigantocellular region,small cell region

Participate in widespread

connections Rostral continuation of

interneuronal network foundin spinal cord


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Cerebellar pathways

Conduct impulses from the leg and trunk muscles for

unconscious proprioception

Dorsal & Ventral Spinocerebellar Tracts

Enter cerebellum via inferior cerebellar peduncle


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Brainstem Internal Anatomy


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Components of the brainstem

Sensory ascending pathways (dorsal): Relay nuclei, tracts

Motor descending pathways (ventral) Tracts, motor nuclei brainstem

Cerebellar pathways Tracts, cerebellar afferent and efferent nuclei

Cranial nerve sensory and motor tracts Cranial nerve nuclei, nerve entry and exit points

CPGs: rhythmic chewing, respiration, cardiovascularregulation & gain adjustments for reflexes

Modulatory systems: locus coeruleus, raphe &substantia nigra

Chemically coded nuclei


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Tracing through the brainstem:

Dorsal Column/Medial Lemniscal

System


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Corticospinal Tract


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Caudal Medulla


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Caudal Medulla

Closed medulla


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Medulla


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Rostral Medulla


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Rostral Medulla


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Medulla-Pons Junction


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Mesencephalon


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The Cranial Nerves

The head and neck are not innervatedby spinal nerves

Sensory information is received and

motor information is sent via 12 cranialnerves

Considered part of the PNS they

convey messages to and from thebody's muscles and glands.


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Each cranial nerve.

Can be referred to by a name ornumber!

Has a general function

Has at least a motor, sensory orparasympathetic component

Some have more than one component

Has associated brainstem nuclei Innervates a structure(s)


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I

I

II

IIIIV

V

VI

VIIIVII

IXX

XI XII

Cranial nerves can be identifiedon the ventral surface of the brain


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I Olfactory On Some

II Optic Old Say

III Occulomotor Olympus Marry*

IV Trochlear Towering Money

V Trigeminal Tops ButVI Abducens A My

VII Facial Frenchman Brother*

VIII Auditory/Vestibulocochlear And Says

IX Glossopharyngeal German Big*

X Vagus Viewed Business*XI Spinal/Accessory Some Makes

XII Hypoglossal Hops Money

Some tricks to learning cranial nerve

numbers, names & components

S = Sensory

M = Motor

B = Both/Mixed Sensory & Motor

* = Parasympathetic


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Arrangement of

brainstem

cranial nervenuclei in

columns

Midbrain

Pons

Medulla

Insert picture with

different levels

differentiated


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General Rules of Thumb

Most motor nuclei are

associated with a singlecranial nerve

Afferent nuclei often receive

fibers from several cranial

nerves

All associated with a

single function however,

e.g., nucleus of solitary

tract


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Functions of Cranial Nerves

www.neurophys.com/EMG/Cranial_Nerves/


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Cranial Nerve I: Olfactory

Component: Sensory

Function: Smell

Tract: Olfactory cells of nasal mucosa

Olfactory Bulbs pyriform cortex


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Cranial Nerve II: Optic

Component(s): Sensory

Function: Vision

Tract: retinal ganglioncells opticchiasmthalamusprimary visualcortex in

occipital lobe


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Cranial Nerve III: Oculomotor

Component #1: Motor

Function(s): Movement of eyeball &

lens accomodation

Structure(s)

Innervated:

4 eyeball muscles & 1

eyelid muscle

Component #2: Parasympathetic

Nucleus location: midbrain

Function: pupil constriction

Structure(s)

Innervated:

ciliary muscle and

pupillary constrictor

muscles


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Cranial Nerve III: Oculomotor


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Cranial Nerve IV: Trochlear

Component: Motor

Function: moves eyeball

Nucleus location: midbrain

Structure(s)

Innervated:

superior oblique muscles


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Cranial Nerve V: Trigeminal

Component #1: Sensory(impulses oftouch, pain, heat and

cold)

Locations of nuclei: pons & medulla

Function: (1) sensations; (2)

general sensory fromtongue; (3)

proprioception

Structure(s)

Innervated:

(1) face, scalp, teeth,

lips, eyeballs, nose &

throat lining; (2) anterior

2/3 of tonque; (3)

muscles of mastication


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Component #2: Motor

Function: chewing

Nucleus location: trigeminal motor nucleusin pons

Structure(s)

Innervated:

muscles of mastication


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Cranial Nerve VI: Abducens

Component: Motor

Function: Eyeball movement

Nucleus: abducens nucleus in

pons

Structure(s)

Innervated:

lateral rectus muscle of

eye


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Cranial Nerve VII: Facial

Component #2: Motor

Nucleus location: facial motor nucleus in

ponsFunction: facial expressions

Structure(s)

Innervated:

muscles of the face

Component #1: Sensory

Nucleus location: medulla

Function: (1) taste & (2)

proprioception

Structure(s)

Innervated:

(1) anterior 2/3 of tongue

& (2) face and scalp


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Cranial Nerve VII: Facial

Component #3: ParasympatheticNucleus location: Superior salivatory

nucleus in medulla

Function: salivation and lacrimation

(drooling and tears)

Structure(s)

Innervated:

salivary and lacrimal

glands via

submandibular and

pterygopalatine gamglia


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Cranial Nerve VIII: Vestibulocochlear(aka acoustic or auditory nerve)

Component: Sensory

Functions: (1) Balance

(2) Hearing

Nucleus: In pons and medulla

Structure(s)

Innervated:

vestibular apparatus of

internal ear

cochlear of internal ear

auditory cortex in the

temporal lobes


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Cranial Nerve VIII: Vestibulocochlear(aka acoustic or auditory nerve)


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Cranial Nerve IX: Glossopharyngeal



Function: (1) taste; (2)proprioception for

swallowing & (3) blood

pressure receptors

Structure(s)

Innervated:

(1) posterior two thirds of

tongue; (2) throatmuscles & (3) carotid

sinuses


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Component #2: Motor


Function: (1) swallowing and gagreflexes & (2) tear

production

Structure(s)

Innervated:

(1) throat muscles and

(2) lacrimal glands


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Function: saliva production

Structure(s)

Innervated:

parotid glands


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Cranial Nerve X: Vagus



Function: (1) chemoreceptors; (2)

pain receptors; (3)sensations; (4) taste

Structure(s)

Innervated:

(1) blood oxygen

concentration, carotid

bodies; (2) respiratory &

digestive tracts; (3)external ear, larynx &

pharynx (4) tongue


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Component #2: Motor


Function(s): (1) heart rate & stroke

volume; (2) peristalsis;(3) air flow; (4) speech &

swallowing

Structure(s)

Innervated:

(1) pacemaker &

ventricular muscles; (2)

smooth muscles of thedigestive tract (3) smooth

muscles in bronchial

tubes (4) muscles of

larynx a & pharynx


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Structure(s)

Innervated:

smooth muscles and

glands of the same areas

innervated by motorcomponent, as well as

thoracic and abdominal

areas


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Cranial Nerve XI: Spinal Accessory

Component: Motor

Function: head rotation (& shoulder

shrugging!)

Nucleus location: accessory nucleus in

medullaStructure(s)Innervated:

trapezius &sternocleidomastoidmuscles


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Cranial Nerve XII: Hypoglossal

Component: Motor

Function: Speech and swallowing

Nucleus location: In medulla

Structure(s)Innervated:

Throat and tonguemuscles


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Cranial Nerve XII: Hypoglossal

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