Neurological Anatomy Debbie Summers RN, MSN, CS I. Overview of Neuroanatomy A. Divisions of the Nervous System 1. Central Nervous System a. Brain b. Spinal Cord 2. Peripheral Nervous System a. Cranial Nerves – 12 Pairs b. Spinal Nerves – 31 pairs c. Autonomic Nervous System Sympathetic nervous system - “Fight” or take a “flight” Parasympathetic nervous system - “Rest” and “digest” B. Cells of Nervous System 1. Neurons - functional cell have specialized projections called dendrites and axons. Dendrites bring information to the cell body and axons take information away from the cell body. 2. Neuroglia cells – supporting structure cells C. Skull 1. 8 Cranial Bones 2. 14 Facial Bones D. Meninges and Spaces 1. Meninges-PAD the brain A. Dura Mater-tough mother, lines the skull and brain folds B. Arachnoid – fibrous elastic layer which reabsorbs CSF C. Pia Mater-delicate vascular layer covering the brain and provides nutrients 2. Spaces A. Epidural D. Subdural E. Subarachnoid August 1, 2002 E. Cerebrum 1. Frontal lobe- conceptualization, abstraction, judgement formation, motor function, write words, and higher level centers for autonomic function. Pre-frontal area – personality and character Frontal eye fields – voluntary eye scanning movements; conjugate movements of eye to opposite side of stimuli; voluntary fixation on object Precentral gryus – motor area – voluntary movement, opposite side of body - Homunculus- “little man” Motor speech – broca’s area – word formation, articulation, speed and rhythm, pronunciations 2. Parietal lobe- highest integrative and coordinating center for perception and interpretation of sensory information, ability to recognize body parts and left versus right. post-central gyrus located in parietal lobe is sensory 3. Temporal lobe- Memory storage, auditory integration, and hearing Receptive speech - wernicke’s area 4. Occipital lobe- Visual center and understanding of written material Functional Divisions of the Cerebral Cortex Responsible for many “higher order” functions like language and information processing. Language centers are usually found only in the left cerebral hemisphere. Cortical Area Function Prefrontal Cortex Problem Solving, Emotion, Complex Thought Motor Association Cortex Coordination of complex movement Primary Motor Cortex Initiation of voluntary movement Primary Somatosensory Cortex Receives tactile information from the body Sensory Association Area Processing of multisensory information Visual Association Area Complex processing of visual information Visual Cortex Detection of simple visual stimuli Wernicke's Area Language comprehension Auditory Association Area Complex processing of auditory information Auditory Cortex Detection of sound quality (loudness, tone) Speech Center Speech production and articulation (Broca's Area) 2 5. Subcortical areas a. Internal capsule fibers connecting subdivisions of the brain and spinal cord. Shape of an open fan. b. Limbic system- short term memory, learning, and emotional behavior. c. Basal ganglia- diffuse network deep in cerebral hemispheres. Exhibits regulating and controlling influences on motor integration major center of the extrapyramidal motor system d. Thalamus- relay station e. Hypothalamus- most intricate connection between endocrine and neurosystem - Temperature regulation - Water regulation - Control hormonal secretion of pituitary gland - Control BP (autonomic nervous system) f. Pituitary Gland Anterior – TSH, TSH, ACTH, Prolactin, LH, FSH Posterior – ADH, Oxytocin F. Brainstem 1. Midbrain- Motor movement, relay of impulses, postural reflex patterns, auditory reflexes, righting reflex, some control of vision and origin of cranial nerves III and IV. 2. Pons- Pneumotaxic center (rhythm of respiration), connection between medulla, midbrain, and cerebellum, and origin of cranial nerves V, VI, VII, and VIII. 3. Medulla oblongata- cardiac, vasomotor, and respiratory center, center for cough, swallowing, and hiccuping, role in reticular activating system, and origin of cranial nerves IX, X, XI, and XII. 3 G. Cerebellum Coordination of fine motor movement, balance, rapid repetitive movements. H. Ventricles-400-600 cc CSF daily, reabsorption. Clear fluid with high glucose 1. Cerebral Spinal Fluid (CSF) a. Formed: Choroid Plexus b. Circulates: c. Lateral ventricles d. Intraventricular foremen (Foramen of Monroe - this is the sight for zero referencing ventricular drains. it is located midway between the lateral aspect of the eyebrow and the tragus of the ear.) i 3rd Ventricle ii Aqueduct of Sylvius iii 4th Ventricle iv Cisterna & Subarachnoid space v Foramen of Luscka & Magendie e. Absorbed: Arachnoid Villi (determined by hydrostatic pressure) 4 Circle of Willis: Brings the system intact to provide collateral blood flow, but also area that most cerebral aneurysms are found (i.e. at the base of the anterior, middle, or post cerebral arteries) 5 ABBR Name of Artery ACA Anterior Cerebral Artery AComA Anterior Communicating Artery AICA Anterior Inferior Cerebellar Artery ASA Anterior Spinal Artery BA Basilary Artery ICA Internal Carotid Artery MCA Middle Cerebral Artery PCA Posterior Cerebral Artery PComA Posterior Communicating Artery PICA Posterior Inferior Cerebellar Artery SCA Superior Cerebellar Artery VA Vertebral Artery 6 Abbr Name of Artery Distribution Ascends through base of skull to give rise to the anterior and Internal Carotid ICA middle cerebral arteries, and connect with posterior half of circle Artery of Willis via posterior communicating artery Anterior Cerebral Supplies most medial portions of frontal lobes and superior ACA Artery medial parietal lobes Middle Cerebral Trifurcates into temporal, frontal, and parietal branches that MCA Artery supply most of the parenchyma of these lobes Anterior AComA Communicating Connects the anterior cerebral arteries at their closest juncture Artery The vertebrals emerge from the posterior base of skull and merge VA Vertebral Artery to form the basilar artery Formed by the junction of the two vertebral arteries, it terminates BA Basilar Artery as a bifurcation into the posterior cerebral arteries Posterior Cerebral Supplies the occipital lobe and the inferior portion of temporal PCA Artery lobe. A branch supplies the choroid plexus. Posterior Connects the anterior circle of Willis with the posterior cerebral PComA Communicating artery of vertebral-basilar circulation posteriorly Artery Superior SCA Supplies the dorsal cerebellum, pons, and midbrain Cerebellar Artery Anterior Inferior AICA Supplies the inferior cerebellum and portions of pons and medulla Cerebellar Artery Posterior Inferior Supplies the posterior cerebellum, choroid plexus in 4th ventricle, PICA Cerebellar Artery and portions of medulla Anterior Spinal ASA Descends along the anterior (ventral) aspect of the spinal cord Artery Venous Circulation a) External Jugular - venous blood from the skin and muscles of the head b) Internal Jugular - drains the dural sinuses of the brain c) Dural Sinuses - large veins within the dura mater of the brain i) Superior Sagittal ii) Inferior Sagittal iii) Straight iv) Transverse v) Sigmoid vi) Cavernous vii) Petrosal d) Superficial Veins i) Drain cortex into the dural sinuses 7 e) Deep veins - drain the white matter, thalamostriate, septal, internal cerebral and the great cerebral vein (Vein of Galen) into the Internal Jugular vein Cranial Nerve Function I. Olfactory Sense of smell II. Optic Vision III. Oculomotor Elevation of upper eyelid Responsible for EOM IV. Troclear Responsible for EOM V. Trigeminal Sensory- Facial Motor- Jaw, chewing VI. Abducens Responsible for EOM VII. Facial Sensory- Taste anterior 2/3 of tongue Motor- Facial movement VIII. Acoustic Hearing and balance IX. Glossopharyngeal Uvula movement - swallowing X. Vagus Carotid sinus reflex XI. Spinal accessory Shoulder movement XII. Hypoglossal Tongue movement 8 Cerebral Circulation Anterior Circulation - Internal Carotid Artery 1. Middle Cerebral Artery (MCA) a. Superior branches of MCA supply these key functional areas: Primary motor cortex for face and arm, and axons originating in the leg as well as face and arm areas that are headed for the internal capsule as part of the corticobulbar or corticospinal tracts Broca's area and other related gray and white matter important for language expression--in the language-dominant (usually left) hemisphere Frontal eye fields (important for 'looking at' eye movements to the opposite side) Primary somatosensory cortex for face and arm Parts of lateral frontal and parietal lobes important for 3-D visuospatial perceptions of one's own body and of the outside world, and for ability to interpret and express emotions--in the nondominant (usually right) hemisphere b. Inferior branches of MCA supply these key functional areas: Wernicke's and other related areas important for language comprehension in the language-dominant (usually left) hemisphere Parts of the posterior parietal lobe important for 3-D visuospatial perceptions of one's own body and of the outside world, and for the ability to interpret emotions--in the nondominant (usually right) hemisphere Optic radiations, particularly fibers that represent information from the contralateral superior quadrants and loop forward into the temporal lobe (they are located anterior and lateral to the temporal horn of the lateral ventricle) as they travel from the lateral geniculate body to the striate cortex, located in the occipital lobe 2. Anterior Cerebral Artery (ACA) septal area primary motor cortex for the leg