Neurological System Anatomy & Physiology Part 2

Transcription

1 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 1

2 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 2

3 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 & 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 3

4 Brodmann Classification & Function Functions of the Lobes Frontal precentral gyrus Broca s area motivation, aggression, ST memory, abstract & highlevel 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 4

5 Motor Cortex Sensory Cortex A different view Hickey, J. (2009) The clinical practice of neurological & neurosugrical nursing (6th Ed): Lipincott Williams & Wilkins. Cerebral birth, both hemispheres have equal capacity for development Lt brain dominant one hemisphere develops language, analysis, etc into dominant one Rt brain dominant 90% population Lt hemispheric dominance nonverbal perceptual, art, music Reflected by handedness but many Lt handed individuals are Lt hemispheric dominant 5

6 Basal Ganglia Several masses of subcortical nuclei located deep in cerebral hemispheres Lenticular nucleus Globus pallidus and putamen Caudate nucleus Amygdaloid body Claustrum Motor control of fine body movements Especially hands & lower extremities Corpus Striatum Basal Ganglia Geography Diencephalon & Brainstem 6

7 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, sleepwake cycle, circadian rhythms (Hypophysis) Pituitary Gland Located in the sella turcica & base of brain Connected to the hypothalamus by infundibulum/hypophyseal stalk 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 7

8 Equilibrium Movement co-ordination Fine motor move t Balance Cerebellum 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 Spinal Nerves Extracted from Crossman, A. R., Neary, D. (1995) An Illustrated Colour Text. Churchill Livingstone, New York. 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 8

9 Dermatomes Myotomes 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) 9

10 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) medulla Other tracts 10

11 Sensory Tracts Dorsal(Posterior) Columns Fasciculus gracilis & cuneatus: Fine touch Pressure Vibration Position sense Proprioception Lateral Spinothalamic Pain Temperature Sensory System 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 11

12 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 thoraciclumbar 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 12

13 SNS -activated during stress - fright, fight, flight -adrenergic release of NE PNS -stimulates visceral activities -conservation, homeostasis -cholinergic release of ACh ANS Another View 13

14 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 Maybe this will help! Cranial Nerve Rhymes 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 CN I Olfactory Sense of smell 14

15 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 15

16 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 16

17 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 17