Measuring Ocular Microtremor. The Brainstem Has 3 components 4 cranial nerves on each section.
New Brainstem and Cranial Nerves
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Transcript of New Brainstem and Cranial Nerves
Brainstem & Cranial Nerves
Maryann Martone, Ph. D.
NEU 256
October 13, 2005
Review: Levels of the Spinal Cord
Ventricles in brainstem
• Mesencephalon cerebral aqueduct
• Metencephalon 4th ventricle
• Mylencephalon 4th ventricle
vermis
Occipital LobeThalamus
Corpus callosum
Hypothalamus
Fornix
Anterior commissure
Optic nerve
4th ventricle
Posterior commissure
pyramid
Mammillary body
Quadrigeminal cistern
internal capsulebasal ganglia
optic nerveoptic tract
hypothalamusmammillary body
cerebral peduncle
interpeduncular fossa
flocculusinferior olivary
nuclear complex
cerebellum
cerebellar tonsil
pyramid
pyramidal decussation
pons
optic chiasm
Anterior view of brainstem
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
Middle cerebellar peduncle
Superior colliculus
Inferior colliculusCerebral peduncle
Superior cerebellar peduncle
Inferior cerebellar peduncle
Medulla
4th ventricle
Posterior view of brainstem
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
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 of pain and temperature• Lateral Spinothalamic Tract
– origin dorsal horn cells of the gray matter– Fibers cross contralaterally through the anterior commissure and ascend to the VPL
nucleus
Transmits sensations of touch• Ventral Spinothalamic Tract
– origin cells of the posterior horn– Fibers cross to the opposite side in the anterior commissure
Descending motor pathwaysVoluntary 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 movement coordination center in medulla• Medial Longitudinal Fasciculus
– Contains both ascending and descending fibers
Motor Hierarchy•Lateral group (extremities; fine motor control)
•Corticospinal tract
•Rubrospinal tract
•Medial group (axial musculature; rhythmic and postural movements)
•Vestibulospinal tract
•Tectospinal tract
•Reticulospinal tract
•“Final common path”: motor pool
Reticular Formation
• “Core” of brainstem (midbrain, pons and medulla) composed of loosely organized neurons, outside of the major nuclear groups of the brainstem.
• Medial-to-lateral: raphe nuclei, gigantocellular region, small cell region
• Participate in widespread connections
• Rostral continuation of interneuronal network found in spinal cord
Cerebellar pathways
Conduct impulses from the leg and trunk muscles for unconscious proprioception
• Dorsal & Ventral Spinocerebellar Tracts– Enter cerebellum via inferior cerebellar peduncle
Brainstem Internal Anatomy
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, cardiovascular regulation & gain adjustments for reflexes
• Modulatory systems: locus coeruleus, raphe & substantia nigra– Chemically coded nuclei
Tracing through the brainstem: Dorsal Column/Medial Lemniscal
System
Corticospinal Tract
Caudal Medulla
Caudal Medulla
“Closed” medulla
Medulla
Rostral Medulla
Rostral Medulla
Medulla-Pons Junction
Mesencephalon
The Cranial Nerves
• The head and neck are not innervated by spinal nerves
• Sensory information is received and motor information is sent via 12 cranial nerves
• Considered part of the PNS they convey messages to and from the body's muscles and glands.
Each cranial nerve….
• Can be referred to by a name or number!
• Has a general function• Has at least a motor, sensory or
parasympathetic component• Some have more than one component• Has associated brainstem nuclei• Innervates a structure(s)
I
I
IIIII
IVVVI
VIIIVII
IXX
XI XII
Cranial nerves can be identified on the ventral surface of the brain
I Olfactory On Some
II Optic Old Say
III Occulomotor Olympus Marry*
IV Trochlear Towering Money
V Trigeminal Tops But
VI 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 = SensoryM = MotorB = Both/Mixed Sensory & Motor* = Parasympathetic
Arrangement of brainstem
cranial nerve nuclei in columns
• Midbrain
• Pons
• Medulla
Insert picture with different levels differentiated
General Rules of Thumb
•Most motor nuclei are associated with a single cranial nerve
•Afferent nuclei often receive fibers from several cranial nerves
•All associated with a single function however, e.g., nucleus of solitary tract
Functions of Cranial Nerves
www.neurophys.com/EMG/Cranial_Nerves/
Cranial Nerve I: OlfactoryComponent: Sensory
Function: Smell
Tract: Olfactory cells of nasal mucosa Olfactory Bulbs pyriform cortex
Cranial Nerve II: Optic
Component(s): Sensory
Function: Vision
Tract: retinal ganglion cells optic chiasm thalamus primary visual cortex in occipital lobe
Cranial Nerve III: OculomotorComponent #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
Cranial Nerve III: Oculomotor
Cranial Nerve IV: Trochlear
Component: Motor
Function: moves eyeball
Nucleus location: midbrain
Structure(s) Innervated:
superior oblique muscles
Cranial Nerve V: Trigeminal
Component #1: Sensory(impulses of touch, pain, heat and cold)
Locations of nuclei: pons & medulla
Function: (1) sensations; (2) general sensory from tongue; (3) proprioception
Structure(s) Innervated:
(1) face, scalp, teeth, lips, eyeballs, nose & throat lining; (2) anterior 2/3 of tonque; (3) muscles of mastication
Cranial Nerve V: Trigeminal
Component #2: Motor
Function: chewing
Nucleus location: trigeminal motor nucleus in pons
Structure(s) Innervated:
muscles of mastication
Cranial Nerve V: Trigeminal
Cranial Nerve VI: Abducens
Component: Motor
Function: Eyeball movement
Nucleus: abducens nucleus in pons
Structure(s) Innervated:
lateral rectus muscle of eye
Cranial Nerve VII: Facial
Component #2: Motor
Nucleus location: facial motor nucleus in pons
Function: 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
Cranial Nerve VII: Facial
Component #3: Parasympathetic
Nucleus 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
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
Cranial Nerve VIII: Vestibulocochlear (aka acoustic or auditory nerve)
Cranial Nerve IX: Glossopharyngeal
Component #1: Sensory
Nucleus location: medulla
Function: (1) taste; (2) proprioception for swallowing & (3) blood pressure receptors
Structure(s) Innervated:
(1) posterior two thirds of tongue; (2) throat muscles & (3) carotid sinuses
Cranial Nerve IX: Glossopharyngeal
Component #2: Motor
Nucleus location: medulla
Function: (1) swallowing and gag reflexes & (2) tear production
Structure(s) Innervated:
(1) throat muscles and (2) lacrimal glands
Cranial Nerve IX: Glossopharyngeal
Component #3: Parasympathetic
Function: saliva production
Structure(s) Innervated:
parotid glands
Cranial Nerve X: Vagus
Component #1: Sensory
Nucleus location: medulla
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
Cranial Nerve X: Vagus
Component #2: Motor
Nucleus location: medulla
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 the digestive tract (3) smooth muscles in bronchial tubes (4) muscles of larynx a & pharynx
Cranial Nerve X: Vagus
Component #3: Parasympathetic
Structure(s) Innervated:
smooth muscles and glands of the same areas innervated by motor component, as well as thoracic and abdominal areas
Cranial Nerve XI: Spinal Accessory
Component: Motor
Function: head rotation (& shoulder shrugging!)
Nucleus location: accessory nucleus in medulla
Structure(s) Innervated:
trapezius & sternocleidomastoid muscles
Cranial Nerve XII: Hypoglossal
Component: Motor
Function: Speech and swallowing
Nucleus location: In medulla
Structure(s) Innervated:
Throat and tongue muscles
Cranial Nerve XII: Hypoglossal