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Neurological System Anatomy & Physiology

Part 2

S. Elliott, RN, BScN, CNCC(C)

ICU Professional Practice Leader

M. Cunningham, RN, MScN, ICU Nurse Practitioner

Hotel-Dieu Grace Hospital

Windsor, Ontario

January 2013

Divisions of Nervous System

� CNS

� Brain

� Spinal Cord

� Peripheral NS

� 12 pr CN

� 31 pr SN

� ANS

� PNS

� SNS

Subdivisions of the Brain

� 3 major areas:

� Cerebrum

� Hemispheres

� Thalamus

� Hypothalamus

� Basal Ganglia

� CN I & II

� Brain Stem

� Midbrain

� Pons

� Medulla

� Cerebellum

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Important Landmarks

� Gyri

� Sulci/fissure

� Lobes

� Great longitudinal fissure

� Lateral fissure of Sylvius

� Central fissure of Rolando

� Parietal-Occipital fissure

� pre-central gyrus

� post-central gyrus

Sulci & Gyri

Precentral gyrus Central fissure of Rolando

Grey & White Matter

� Each hemisphere covered by cerebral cortex of gray matter 2-5 mm thick� Contains billions of neurons

� Under cortex lies white matter� Association & projection pathways

� Contains nerve fibers and neuroglia

� 3 types:

� Transverse (commissural) fibers- largest is corpus callosum

� Projection fibers

� Association fibers

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

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White Matter Fibres

•Transverse (Commissural)

•Connect functionally related

structures

•Run from one cerebral

hemisphere to the other

•Corpus Callosum is largest

commissure

•Projection Fibres

•Pass between the cerebral

cortex & subcortical structures

•Association Fibres

•Interconnect cortical sites lying within one cerebral

hemisphere

•Superior Longitudinal Fasciculus

•Inferior Longitudinal Fasciculus

Internal Capsule� Corona radiata- area where many fibers are coverging from/to cortex & converging @ brainstem

� Internal Capsule- area where fibers enter thalamus/hypothalamus region

� Massive bundle of sensory & motor fibers connection various subdivisions of the brain and spinal cord� Contains both radiation and projection fibers

Back to the Surface…Lobes

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Brodmann Classification & Function

Functions of the Lobes

� Frontal� precentral gyrus

� “Broca’s” area

� motivation, aggression, ST memory, abstract & high-level thought, concentration & mood

� voluntary eye movement

� Parietal� interpret sensory input i.e. size, shape, weight

� awareness of/orientation to body in space

� Temporal� olfactory & auditory input

� Interpretive area

� Junction of temporary, occiptial, & parietal meet

� memory

� Wernicke’s area

� Occipital� visual reception, association & integration

Functional Areas of Cortex

� Primary Motor area � precentral gyrus

� neurons control conscious & precise voluntary skeletal muscle contraction

� Primary Sensory area� postcentral gyrus

� termination of sensory pathways that carry general sensory info r/t temperature, touch, pressure, pain & proprioception

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Motor Cortex Sensory Cortex

A different view…

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosugrical nursing (6th Ed):

Lipincott Williams & Wilkins.

Cerebral Dominance

� @ birth, both hemispheres have equal capacity for development

� one hemisphere develops into dominant one� 90% population Lt hemispheric dominance

� Reflected by “handedness” but many Lt handed individuals are Lt hemispheric dominant

� Lt brain dominant� language, analysis, etc

� Rt brain dominant� nonverbal perceptual, art, music

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Basal Ganglia

� Several masses of subcortical nuclei located deep in cerebral hemispheres

� Lenticular nucleus

� Globus pallidus and putamen Corpus Striatum

� Caudate nucleus

� Amygdaloid body

� Claustrum

� Motor control of fine body movements

� Especially hands & lower extremities

Basal Ganglia Geography

Diencephalon & Brainstem

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Diencephalon

� Divided into 4 regions� Thalamus*

� Hypothalamus*

� Subthalamus

� Epithalamus* Most NB

� Thalamus� Pair of egg-shaped masses of gray matter deep in hemispheres

� Last station for impulse processing before ascending to the cortex

� Role in conscious pain awareness, focusing attention, the RAS, & Limbic system

� Hypothalamus � Infundibulum connects hypophysis with hypothalamus

� Autonomic (esp SNS), endocrine, hormonal, temp regulation, sexual/ appetite satiation, sleep-wake cycle, circadian rhythms

(Hypophysis) Pituitary Gland� Located in the sella turcica & base of brain

� Connected to the hypothalamus by infundibulum/hypophysealstalk

� Hypothalamus

� Controls pituitary secretions

� Hypophysis ÷ 2 lobes

� Anterior:

� GSH, ACTH, TSH,

� Prolactin, FSH, LH

� Posterior:

� ADH, Oxytocin

Posterior Fossa Cranial Contents

�Brain Stem� Vital functions area that supports life

� Midbrain� CN III-IV

� Visual reflexes

� Pons� CN V-VIII

� Sensory, motor facial visual, secondary respiratory centres & auditory reflexes

� Medulla� CN IX-XII

� main respiratory centre, gag/airway, BP, HR

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Cerebellum

� Equilibrium

� Movement co-ordination

� Fine motor move’t

� Balance

Spinal Cord Anatomy

� segmented mass of nervous tissue

� approx L-1 (2/3 vertebral canal)

� two-way conduction

� major reflex

� meningeal layers

� large epidural space

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

Spinal Nerves� Spinal Nerves

� Dorsal roots

� afferent (sensory) impulses enter cord

– Convey sensory input from specific areas of body

(dermatomes)

– Impulses are directed to the

dorsal root ganglia

� GSA & GVA fibers

� Ventral root

� efferent (motor) impulses leave cord

– Convey motor impulses from

the spinal cord to the body

� GSE & GVE fibers

Extracted from Crossman, A. R., Neary, D. (1995) An Illustrated Colour Text. Churchill Livingstone, New York.

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Dermatomes

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

Myotomes

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

Spinal Cord Anatomy

Grey matter

� composed of cell bodies (ant. post. lat.)

� mirror image (H)

� grey commissure/central canal

White matter

� composed of nerve fibers

� 3 directions (up, down, across)

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

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White Matter

� Funiculi or columns

� named according to position

� motor messages travel together- descending (efferent)

� sensory travel together-ascending (afferent)

� “Spinothalamic”

� “Corticospinal”

� Name reveals Origin & Destination

Ascending & Descending Tracts

Motor Pathways

� Corticospinal Tract

� Precise/skilled voluntary movement

� Impulse originates in the motor strip (descends without synapse)

� Decussate @ medulla

� Other tracts

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

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Sensory Tracts

� Dorsal(Posterior) Columns� Fasciculus gracilis & cuneatus:

� Fine touch

� Pressure

� Vibration

� Position sense

� Proprioception

� Lateral Spinothalamic� Pain

� Temperature

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

SensorySystem

� Sensation initiated by sensory receptors’ stimulation

� Located in skin, mucous

membranes, muscles, tendons,

viscera

� Peripheral nerve enters the SC, sensory fibers follow posterior root,

and tracts procede along STT or PC

� Lateral STT– Pain & Temperature

� Posterior Columns

– Position & Vibration

– Fine touch; accurately localized & finely discriminating

� Anterior STT– Crude touch; light, no accurate id

C, T, L, S dedication

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Spinal Cord Blood Supply

� 1 Anterior Spinal Artery

� 2 Posterior Spinal Arteries

� Radicular Branches

Veins of Spinal Cord

� Similar to arterial

� 6 interconnecting venous channels

� Groups of venous plexuses

� drain along nerve root

Autonomic Nervous System

� Sympathetic NS� activated during stress

� “fright, fight, & flight”

� adrenergic fibers release NE

� Preganglionic fibers emerge from thoracic-lumbar region

� Parasympathetic NS� stimulates visceral activities associated with conservation, restoration, & maintenance of normal function

� cholinergic fibers release AcH

� Pregangionic fibers emerge from cranio-sacral region

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SNS-activated during stress -”fright, fight, flight”

-adrenergic release of NE

PNS-stimulates visceral activities

-conservation, homeostasis

-cholinergic release of ACh

ANS… Another View

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

Extracted from:

Hickey, J. (2009) The clinical practice of neurological & neurosurgical

nursing (6th Ed): Lipincott Williams & Wilkins.

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Cranial Nerves

� CN I - Olfactory

� CN II - Optic

� CN III - Oculomotor

� CN IV - Trochlear

� CN V - Trigeminal

� CN VI - Abducens

� CN VII - Facial

� CN VIII - Oculovestibular

� CN IX - Glossopharyngeal

� CN X - Vagus

� CN XI - Spinal Accessory

� CN XII - Hypoglossal

Names

� I: On

� II: Old

� III: Olympus

� IV: Towering

� V: Tops

� VI: A

� VII: Fin

� VIII: And

� IX: German

� X: Viewed

� XI: Some

� XII: Hops

Sensory/Motor/Both

� Some

� Say

� Marry

� Money

� But

� My

� Brother

� Says

� Bad

� Business

� Marry

� Money

Maybe this will help!Cranial Nerve Rhymes

CN I Olfactory

� Sense of smell

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CN II (Optic)

� Visual fields

� Visual acuity*

CN III, IV, VI (Oculomotor, Trochlear, Abducens)

� Tested together as mediates voluntary eye movement � III- upper eyelid elevation & most eye movements

� IV- controls downward & inward eye move’t

� VI- controls lateral eye move’t

� CN III responsible for pupillary light reflexes

Cranial Nerves III, IV, VI

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CN V (Trigeminal)� Sensation to 3 divisions of the face

� Touch jaw, cheeks, &

forehead bilaterally with

cotton wisp/point of pin

� Controls muscles of mastication

� Have pt clench jaw & palpate temporal & masseter muscles

� Attempt opening of clenched jaw

� Corneal Reflex

CN VII (Facial)

� Controls all facial muscles

� Have patient smile, show teeth, & puff out cheeks

� Observe facial symmetry as pt raises/ lowers eyebrows

� Responsible for taste

perception on ant 2/3

portion of tongue

CN VIII (Oculovestibular)

� Cochlear division

� Controls hearing

� Vestibular division

� Controls equilibrium, body position & space orientation

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CN IX, X (Glossopharyngeal & Vagus)

� IX� Controls swallowing

� Supplies sensation to phayngeal mucous membranes

� Taste perception on posterior 1/3 of tongue

� X� Controls swallowing, phonation, & movement of uvula, soft palate, tonsils, viscera of the thorax & abdomen

� Observe palate while pt says “ah”

� Test for gag, swallowing

� Suctioning, presence of cough, etc

CN XI (Spinal Accessory)

� Controls the sternocleidomastoid & upper trapezius muscles’ strength� Pt pushes his chin against your hand

� Palpate & inspect trapezius muscle as pt shrugs against resistance

CN XII (Hypoglossal)

� Tongue movement

� Permits normal speech and swallowing