Neuroscience Midterm Exam 2024-2025 PDF

Descending Pathway & CN 7, 11, 12 NEUROSCIENCE– 1st SEMESTER MIDTERMS (AY 2024-2025) Doctor/Lecturer: Dr. Tulmo Transcriber/s and Editor/s: Group 3A muscular activity. I. Descendi...

Descending Pathway & CN 7, 11, 12 NEUROSCIENCE– 1st SEMESTER MIDTERMS (AY 2024-2025) Doctor/Lecturer: Dr. Tulmo Transcriber/s and Editor/s: Group 3A muscular activity. I. Descending Tracts Introduction Descending autonomic fibers DESCENDING PATHWAY (3-NEURON CHAIN) When talking about the different autonomic ○ First-order neuron functions, all of the organs of the body will have Cerebral cortex sympathetic and parasympathetic influences and ○ Second-order neuron its the descending autonomic activity through the internuncial neuron in anterior descending autonomic fibers that such functions gray column would take effect. ○ Third-order neuron Anterior horn cell A. Descending Tracts: Function B. Descending Tracts: Origin 1. Corticospinal tracts 1. Reticulospinal - Reticular formation ○ Concerned with voluntary, discrete, 2. Tectospinal - Superior colliculus skilled moments especially those of the 3. Rubrospinal - Red nucleus in tegmentum of distal parts of the limbs midbrain 2. Reticulospinal 4. Vestibulospinal - vestibular nuclei in pons and ○ Facilitate or inhibit the activity of alpha medulla and gamma motor neurons and may 5. Olivospinal - inferior olivary nuclei facilitate or inhibit voluntary movement or 6. Descending autonomic fibers - cerebral cortex, reflex activity hypothalamus, amygdaloid complex and reticular 3. Tectospinal formation ○ Concerned with reflex postural movements in response to visual stimuli 4. Rubrospinal ○ Acts on alpha and gamma motor neurons Rubrospinal to facilitate the activity of the flexor Rubro - red muscles and inhibit the activity of Olivospinal extensor or antigravity muscles Inferior olivary nucleus - biggest nucleus with a 5. Vestibulospinal crumpled bag-like appearance found in the ○ Acts on motor neurons to facilitate the medullary region. activity of the extensor muscles and if hit, muscular activity is affected inhibits the activity of the flexor muscles Descending autonomic fibers and is concerned with the postural Has different origins and is wide spread due to it activity associated with balance having various functions. 6. Olivospinal ○ May play a role in muscular activity C. Descending Tracts: Extrapyramidal Vs. Pyramidal (although it's existence is debated) Extrapyramidal 7. Descending autonomic fibers ○ Basal ganglia ○ Control of visceral activity ○ Cerebellum Pyramidal Vs. Extrapyramidal Corticospinal tracts The term pyramidal tract is used commonly by Also known as the pyramidal tract. Out of all the clinicians and refers specifically to the descending pathways, this is the most important corticospinal tracts. The term came into because you will be able to predict or localize common usage when it was learned that the where the lesion is through this tract. corticospinal fibers become concentrated on the Reticulospinal anterior Ascending reticular activating system is usually part of the medulla oblongata in an area referred reflex in nature. to as the pyramids. Tectospinal The term extrapyramidal tracts refers to all the Example: when a person turns their head descending tracts other than the corticospinal towards the direction where they hear the noise. tracts. Tectum and spinal. Begins at the tectum found in The Pyramidal motor system refers only to the the superior colliculus of the midbrain and ends corticospinal tract or pyramidal tract while at the anterior horn cell of the spinal cord. extrapyramidal motor system refers to other Corpora quadrigemina (superior & inferior structures that control movement other than the colliculus) corticospinal tract (basal ganglia and ○ Superior colliculus - visual reflexes cerebellum). Hence, any lesions which are ○ Inferior colliculus - auditory or sound labeled as extrapyramidal would be referring to impulses lesions either in the basal ganglia or its collecting Vestibulospinal pathways or the cerebellar pathways. It is the vestibulospinal tract that maintains balance while standing up due to the support of the extensor muscles. D. Descending Tracts: Organization of the Motor Olivospinal Cortex Plays a role in the reflex coordination of Face: lateral surfaces of both cerebral hemispheres Hand and arm: Superior to the area of face 1 Reference/s: Snell’s Neuroanatomy 8th ed., Dr. Tulmo’s Lecture & PPT, O’Sullivan & Siegelman Physical Rehabilitation 7th ed, Magee Orthopedic Physical Assessment 7th ed.  Leg and foot: mostly medial and on the superior Area 4: Primary motor cortex (precentral gyrus) surfaces of the cerebral hemispheres Area 6: Premotor and supplementary motor cortex Area 3, 1, 2: Primary somatosensory cortex (postcentral gyrus); Somesthetic center in the Parietal lobe Organization of the Motor Cortex Stimulation of the different areas of the 2/3 arise from the precentral gyrus (controls motor activity), brain will produce actions on the while 1/3 arise from the postcentral gyrus (influence sensory opposite side of the human body to act. input). Homunculus E. Clinical Implications of Arrangement Due to decussation cervicomedullary junction Region of brain and contralateral weakness brainstem Spinal cord ipsilateral weakness weakness in muscles they Roots and nerves supply II. Reflex Arc Involuntary response to a stimulus ○ Components of the Reflex Arc Receptor organ (Deep Tendon) Afferent neuron (a neuron that conducts impulses towards the CNS) Effector neuron (receives the Corticospinal Tract stimulus that innervates the Fibers arise as axons of pyramidal cells situated in effector organ) the fifth layer of the cerebral cortex Effector organ (Muscle) Majority of the fibers are myelinated and relatively slow-conducting, small fibers Law of Reciprocal Inhibition ○ Other branches of the Corticospinal tract The flexor and extensor reflexes of the same limb Cerebral cortex to inhibit the cannot be made to contract simultaneously activity in adjacent regions Caudate and lentiform nuclei, red Crossed Extensor Reflex nuclei, olivary nuclei, and the reticular formation Evocation of a reflex on one side of the body ○ Pathway causes opposite effects on the other limb Pronator Drift Seen when the arms are held outstretched with the palms up and the fingers spread Weaker hand may begin to close and pronate and drift downward ○ Indicator of UMN lesion Upper Motor Neuron Lower Motor Neuron (UMN) (LMN) Increased tone Decreased tone Hyperreflexia Hyporeflexia Babinski sign Present Babinski sign Absent Muscle bulk generally Muscle bulk Atrophied preserved Fasciculations Absent Fasciculations Present Corticospinal Tracts → Anterior Axial (Head & Trunk) motor- doesn’t decussate → Lateral Limb (Arms & Legs) motor- decussates 2  ➔ CNVII has a motor function, has a role in the autonomic nervous system, and is a sensory cranial nerve Main motor nucleus: ○ upper face: bilateral above the level of the eye ○ lower face: only from opposite cerebral hemisphere below the level of the eye Consists of: ○ facial nerve proper ○ nervus intermedius Pass thru internal auditory meatus where Geniculate ganglion for taste lies ○ subserve the taste of the anterior ⅔ of the tongue Facial Nerve Proper Exists thru stylomastoid foramen of the temporal O’Sullivan & Siegelman Physical Rehabilitation 7th ed bone Innervates muscles of facial expression: ○ Platysma m. ○ Stapedius m. stabilizes the stapes and serves Babinski Sign to dampen excess sound Elicited by stroking of lateral aspect Nervus Intermedius of sole of foot Sends parasympathetic preganglionic fibers to ○ Extension of big toe and pterygopalatine ganglion to innervate: fanning (splaying) of four small toes ○ lacrimal gland ○ Indicative of Pyramidal ○ submaxillary tract lesion ○ sublingual Visceral afferent component carries taste sensation (anterior 2/3) to the solitary tract and nucleus Fasciculation Related with superior salivatory nucleus that (muscle twitching) is seen only with slow innervate submandibular & sublingual glands. destruction of the lower motor neuron cell. random spontaneous twitching of muscle fibers Cranial Nerve VII Nuclei often seen through the skin, are common in → main motor nucleus - lies deep in the reticular individuals with ALS formation of the lower part of the pons → parasympathetic nuclei - lie posterolateral to the main motor nucleus → sensory nucleus - upper part of the nucleus of the A. UMN Pattern of Weakness tractus solitarius and lies close to the motor Upper Extremity extensors are weaker than flexors Lower extremity flexor are weaker than the extensors III. Cranial Nerves VII, XI, XII Corticobulbar ○ The corticobulbar tract provides input to the nuclei innervating muscles of the face (CN7), muscles of mastication (CN5), muscles of the tongue (CN 7 & 9), muscles of the pharynx, muscles of larynx (CN11 Cranial), sternocleidomastoid, and trapezius (CN11 Spinal), etc. This innervation is bilateral for most of the cranial nerves, with the exception of ○ corticobulbar fibers providing input to the lower facial nucleus, which receives contralateral innervation. ○ EXCEPTION: Lower half of the face Genioglossus A. Cranial Nerve 7: Facial Nerve 3 nuclei: ○ main motor nucleus ○ parasympathetic nuclei Innervation of the tongue ○ sensory nucleus → Geniculate ganglion : Anterior ⅔ → Glossopharyngeal Nerve (XI) : Posterior ⅓ → Vagus Nerve (X) : Taste buds and Epiglottis 3 Facial Nerve: (Central/UMN Vs. Peripheral/LMN) → → → A) The innervation to the muscles of the upper face originates on both sides of the brain, whereas the innervation to the muscles of the lower face comes from the opposite side of the brain only. → B) When the cortex is injured, there’s weakness in the contralateral lower face only. Note the drooping of the corner of the lip on the left of the LOWER half while wrinkles are maintained on the UPPER half. Right cortex affecting the Left Lower half of the C. Cranial Nerve 12: Hypoglossal Face (Central; UMNL) Hypoglossal nucleus is located in the ventromedian → C) When the facial nerve is injured, there’s portion of the medulla. weakness in the ipsilateral upper and lower face. It leaves the cranial vault via the hypoglossal canal Note the smoothening of the wrinkles drooping of (posterior cranial fossa of the occipital bone). the corners of the eye and lips affecting both It supplies all the intrinsic muscles of the tongue UPPER and LOWER half of the face. Right Facial including: nerve affecting the Left Face (Peripheral; LMNL) ○ Styloglossus NOTE: Take note of where the lesion takes place, what ○ Hyoglossus consist of the Upper Motor Neuron and Lower Motor Neuron ○ Genioglossus and when does the decussation or crossing of fibers occur Pathway: Hypoglossal nucleus → Midline, beneath the floor of the 4th ventricle → exits via the hypoglossal canal B. Cranial Nerve 11: Accessory Nerve EXCEPTION TO THE ABOVE: Genioglossus Two components: muscle ○ Cranial ○ Only receives corticonuclear fibers from ○ Spinal the opposite cerebral hemisphere (one Motor nerve formed by the union of a cranial and source, contralateral as opposed to a spinal root bilateral source that supplies both sides Cranial Root: of the muscle). ○ from the axons of nerve cells of the ○ Pathway: Hypoglossal nucleus → emerges nucleus ambiguous from the groove between the pyramids and ○ Receives corticonuclear fibers from both olives → exits via the hypoglossal canal. hemispheres ○ Nerve emerges from the medulla between SIDE NOTE HYPOGLOSSAL NERVE the olive and the inferior cerebellar Right and Left genioglossus muscles pull the peduncle tongue forward. ○ Leave the skull thru the Jugular foramen In healthy adults, sticking out of the tongue moves after uniting with the spinal root forward and middle pulling forces both sides. ○ Joins the Vagus nerve Supply styloglossus, hyoglossus, and genioglossus ○ Innervates muscles of the soft palate, muscle. pharynx, and larynx. Action of genioglossus muscle with left lesion, the Spinal Root: tongue will move to the right. ○ From axons of nerve cells in the spinal Right corticobulbar (lesion) —> left nucleus —> left nucleus in upper 5 cervical cord CNXII —> left muscle —> tongue moves to the segments right ○ Gains entry to the cranium thru the Foramen magnum GENIOGLOSSUS TONGUE PROTRUSION ○ Distributed to the Sternocleidomastoid and → Lower motor neuron lesion (ipsilateral) - tongue Trapezius muscle will deviate toward the side with lesion, tongue is smaller on side of lesion (muscle atrophy), fasciculation may accompany or precede the atrophy → Lesion of the corticonuclear fibers (contralateral) - tongue will deviate to the side opposite the lesion, no atrophy and fibrillation *part of the nucleus that supplies the genioglossus receives corticonuclear fibers only from the opposite cerebral hemisphere 4  III. Reading Assignments A. DECEREBRATE RIGIDITY also known as decerebrate posturing due to the overactivity of gamma efferent nerve fibers to the muscle spindles results from the release of these neurons from higher centers. B. PARAPLEGIA IN FLEXION Happens when all descending tracts are severed The reflex responses are flexor in nature Tone of the extensor muscles is diminished C. PARAPLEGIA IN EXTENSION Domination of the increased tone of the extensor muscle over the flexor muscles Believed to be due to incomplete severance of all the descending tracts with the persistence of the vestibulospinal tract. 5  LIMBIC SYSTEM, HYPOTHALAMUS, NEUROTRANSMITTERS NEUROSCIENCE – 1st SEMESTER MIDTERMS (AY 2024-2025) Doctor/Lecturer: Dr. Michelle Yusay (October 15, 2024) Transcriber/s and Editor/s: Group 1B I. LIMBIC SYSTEM Functional system of cortical and subcortical neurons Interconnections form complex circuits important in: ○ Memory ○ Behavior ○ Emotions Damage to the Limbic System would cause: ○ Anterograde amnesia and inappropriate behavior and emotions A. Limbic Lobe - Limbus To border, fringe or ring Coined by Broca - 1878 lobe in medial surface of cerebral hemisphere Bordering corpus callosum and rostral brainstem LAMP ○ Limbic system-Associated Membrane Protein Limbic System - Function Cingulate gyrus and Subcallosal gyrus anterior Emotion activities extension Preservation of Species Cingulum Visceral Activities Septal regions Mechanisms for memory Parahippocampal gyrus and Hippocampal formation Numerous activities of the Hypothalamus Hippocampal Formation Limbic System - Components Memory and Learning Limbic lobe 3 Parts: Amygdala or amygdaloid nuclei ○ Dentate gyrus Hypothalamus ○ Hippocampus proper - Ammon’s Horn Midbrain nuclei ○ Subiculum - transitional zone between hippocampus Thalamus - anterior and dorsomedial nuclei and entorhinal area Fornix, Indusium, Griseum, Mammilothalamic tract Resembles a sea horse Stria terminalis, medullaris and habenula 2 inch long Floor of the temporal horn of the lateral ventricle 1 Reference/s:  → Cingulum to prefrontal, posterior parietal and temporal association areas and also entorhinal area of the parahippocampal gyrus → Then to the hippocampal formation Function: For formation of new memories and learning Bilateral removal (epilepsy) ○ loss of recent and short term memory and ability to learn Anterograde amnesia Thru cingulum from CEREBRAL CORTEX hippocampal formation emits signals to rehearse it until stored permanently for long term memory Alzheimer's Disease Progressive dementia under 65 years old Senile dementia over 65 years old Increasingly forgetful Endocrine Functions: ○ memory, orientation, cognition, and behavior Ventral: Loss of neurons in ○ estradiol-concentrating neurons and corticosterone ○ Hippocampus - output to association cortices and Corticosterone: diencephalon ○ injections have inhibitory effect ○ Parahippocampal areas - input to H from assoc and Hippocampal Lesions limbic area ○ disrupts ACTH release Decrease cholinergic innervation of cerebral cortex Stimulation of HF Reduction of hippocampal connections cause the ○ inhibits ovulation recent memory loss Reduction in cholinergic innervation is due to Hippocampal connections degeneration of large cholinergic neurons in the Basal R and L connected by the hippocampal commissure Nucleus of Meynert in the anterior perforated Neocortex (cingulate gyrus and prefrontal cortex) substance Cingulum (deep to cingulate and parahippocampal ○ substantia innominata gyri) Absence of neocortical acetylcholine account for the Entorhinal part of parahippocampal gyrus cognitive deficits Hippocampal Formation Korsakoff Syndrome Loss of recent memory and tendency to fabricate false accounts of recent events From chronic alcoholism and its nutritional deficiency of Vit B deficiency Hippocampus, mamillary bodies, and medial dorsal thalamic nuclei Initial center of the Papes Circuit Alveus of the hippocampus → Fimbria of the Fornix → Crux of the fornix → Body of the fornix → Column of the fornix (anterior commissure) → Subiculum → Nuclei of the mamillary body → Mamillothalamic tract (bundle of Vicq d Azyr) → Anterior thalamic nucleus → Thalamocingulate radiation → Cingulate Gyrus 2 Emotion From bilateral destruction of the temporal lobes - Any feeling state bilateral amygdaloid nuclei Fear, anger, excitement, love, hate Components Septal region Perception Poorly developed in human Feeling Includes: Autonomic ○ Paraterminal gyrus Affect ○ Subcallosal area in front of lamina terminalis Reflex ○ Septal nuclei Amygdaloid Nucleus Input from hippocampus Amygdala Reciprocal with hypothalamus, amygdala and cingulate Behavior and emotions gyrus Almond shaped beneath the uncus Divided into: ○ Large basolateral group ○ Small corticomedial ○ Central group Connections Basolateral nuclei ○ Well developed in human ○ Input from sensory areas of cerebral cortex and thalamus Corticomedial Nucleus ○ Poorly developed ○ Input directly from olfactory bulb ○ Via lateral olfactory stria Central Nucleus ○ Both basolateral and corticomedial Connections Septal region and anterior hypothalamus to midbrain reticular system ○ via medial forebrain bundle and stria medullaris Stria passes dorsomedial thalamus to habenular nucleus Habenulointerpeduncular tract (fasciculus retroflexus) to interpeduncular nuclei of the Midbrain reticular formation Function Input to ○ Respiratory ○ Cardiovascular ○ Salivator ○ Other centers to respond to emotional events Major output - Ventral Amygdaloid path Associated with reward or pleasure phenomenon Anterior perforated substance Connections may be modified by anti-psychotic drugs Basal nucleus, Hypothalamus and medial dorsal May be involved in the euphoria associated with use of thalamic nucleus narcotics Medial dorsal nucleus - prefrontal cortex Damage - marked increase in sexual activity in elderly ○ thalamoprefrontal radiation or uncinate fasciculus males Central nucleus to Anterior hypothalamus and septal region Limbic System - Visceral brain, Summary ○ Terminal stria Ring Right and Left amygdala - anterior commissure ○ Crown Subdivisions Functions: ○ Cortical Programs appropriate behavioral responses Limbic Lobe ○ Animals Hippocampus Primarily corticomedial nuclei ○ Subcortical ○ Humans Amygdaloid Nucleus Purely non-olfactory experience Septal Region From all parts of cerebral cortex via cingulum to Fornix basolateral nuclei Hypothalamus (MB) Assess nature of input pass to hypothalamus, Olfactory other limbic centers and cerebral cortex to elicit Thalamus response Thalamus Orbitofrontal and cingulum - perceive emotions Sensory Relay for everything you see, hear, taste and Hypothalamus - expresses emotions touch to be directed to cortex to relate with experience for memory storage Kluver - Bucy Syndrome Smell Absence of emotional response (fear, rage, ○ only sense that bypass the thalamus aggression) ○ direct relay near emotion amygdala and mammillary Compulsion to be overly attentive to all sensory stimuli bodies examine objects visually, tactilely and orally. Amygdala Hypersexuality Stimulation Psychic blindness or visual agnosia ○ (+) Anger/Violence, Fear/Anxiety 3  Suppress II. HYPOTHALAMUS ○ (-) Mellow VEGETATIVE AND ENDOCRINE IMBALANCE affected by Benzodiazepines (similar effect to alcohol) Located on the inferior aspect of the diencephalon Hyperorality Borders: Hypersexuality ○ Anterior - Lamina Terminalis Uninhibited Behavior ○ Posterior - midbrain Hippocampus ○ Dorsal - hypothalamic sulcus STORING new Memories ○ Medial - 3rd ventricle Convert Short term memory to Long term memory ○ Lateral - subthalamic nucleus Destruction leads to difficulty in forming new memories Controls visceral activity ○ But old memories remain intact Effector of the limbic system - elicits emotion Learning is difficult Has neural and endocrine components so exerts Hypothalamus influence through nervous and circulatory system BELOW the Thalamus Important in self-preservation and preservation of the Less than 1% of Total Brain Volume species Kidney Bean shaped Influences water balance, food intake, the endocrine HIGHEST CONTROL CENTER FOR INTERNAL system, reproduction, sleep, behavior, and the ORGANS autonomic nervous system Regulates the ANS (Autonomic Nervous System) ○ Fight or Flight release epinephrine (adrenaline) / norepinephrine ○ Rest and Digest hunger, thirst, sleep ○ Self Preservation increase salivation, increase GI motility, processing food ○ Preservation of Species sexual urges, preserving young Functions Learning Integration ○ Olfactory Hypothalamic Subdivisions and Nuclei ○ Visceral Extremely small ○ Somatic 4g or Acetylcholine Tyrosine -> The Catecholamines Tryptophan -> Serotonin w 6 7  NEUROSCIENCE I: SPINAL ANATOMY COURSE NAME– 1st SEMESTER PRELIMS (AY 2024-2025) Doctor/Lecturer: Dr. Jose Mikael R. Garcia Transcriber/s and Editor/s: Group 2-B THE HUMAN SPINE Atlanto-axial spine is comprised of: Occipitocervical junction 7 cervical ○ complex junction of the occiput, atlas, and 12 thoracic axis 5 lumbar ○ stabilized by a dense ligamentous network 5 fused sacral bony segments allowing for movement in three dimensions These segments: The atlas (C1) 1. confer structural support and flexibility ○ permits head flexion and extension via its 2. harbor and convey the ff: articulations with the occipital condyles the spinal cord Fovea dentis 30 paired nerve roots ○ smooth, rounded intracanalicular surface nervous communication of the anterior arch ○ serves as a facet articulating with the General Features odontoid process of the axis below Normal spinal alignment is characterized by: Atlanto-occipital junction 1. cervical lordosis ○ stabilized by the anterior and posterior 2. thoracic kyphosis atlanto-occipital membranes 3. lumbar lordosis ○ attach the occiput to the superior borders => together result in sagittal balance of the anterior and posterior arches of the Intervertebral and zygapophyseal (facet) joints - atlas where spinal motion among adjacent segments occurs Each spinal segment is a bony ring composed of: ○ anterior vertebral body ○ posterior vertebral arch pedicle, pars interarticularis, and laminae encircling the spinal canal Vertebral bodies ○ enlarge from cephalad to caudad ○ provide the primary axial support of the spinal column ➔ occipitocervical joint - between the head and the neck ➔ translation - the forward and backward movement of the bone Atlanto-axial spine Axis (C2) ○ provides the majority of the neck’s axial rotation via its odontoid process (dens) Transverse ligament across the ring of the atlas ○ supports articulation of atlanto-axial joint ○ restricts anterior translation of the atlas with respect to the dens. ➔ C1-C2 - area with high level of turning ➔ C1-C7 - there’s a high degree of flexion 1 Reference/s: Dr. Garcia's PPT Table. Cervical Kinematics Level Flexion-Ext Lateral Axial ension Flexion Rotation (Degrees) (Degrees) (Degrees) O-C1 15-35 0 C1-C2 10-20 30-90 C3-C7 55-80 20 20 (overal) ➔ C1-C2: axial rotation ➔ C3-C7: flexion movement Subaxial Cervical Spine Vertebral arteries - passes generally from C1 to C6 via the transverse foramina and the potential for substantial mobility Superior articulating facets - transition from a posteromedial orientation at C3 to a posterolateral orientation at C7 C7: has transverse foramen but paired vertebral arteries do not course through them ➔ Kyphotic Apex- the maximum curvature / flexion of C2 to C6: have bifid spinous processes the thoracic kyphosis Cervical roots - named according to the vertebra ➔ Some spinal cord tumors - very small are at the below each nerve except C8 level of T7, T8,T9 but they have devastating C8: courses between C7 and T1 neurological deficits because the spinal cord has no Orientation of superior articulating facets: room as compared to spinal cord tumors at the ➔ C1-C3 - posteromedial level of T1 and T2. ➔ C4-C7 - posterolateral ➔ Lumbar puncture / Spinal tap- NOT DONE AT THORACIC REGION! ◆ (Spines inclined downward which is why Thoracic Spine you never see anyone do a spinal tap at Characterized by substantial stability as conferred the level of thoracic region because you by its costal articulations. will not be able to access the spinal Kyphotic apex - typically at T8 cord.) ○ narrowest cross-sectional area of the ➔ Vertebral foramen- spinal cord is located spinal canal ○ most oblique spinous processes in the spine Lumbar Spine Spines - long and inclined downward. Characterized by the spine’s largest vertebral Costal facets - present on lateral aspect of body. bodies Thoracic facets ○ result of increased width ○ intermediately oriented ○ largest axial loads in the mobile spine. ○ intermediate restriction of translation and Ventral body - heights decline from approximately rotation L2 to L5 Lumbar facets - oriented in a nearly sagittal plane, with the concave superior articulating processes facing medially and somewhat posteriorly. Inferior articulating processes - lie medial to the superior processes, correspondingly face laterally and somewhat anteriorly Spine’s largest vertebral bodies - because it carries the largest axial bones Lumbar vertebrae spinous process - oriented horizontally compared to Thoracic that is facing downward ADULTS : spinal cord ends at the level of T12-L1 2  Anterior Longitudinal Ligament originates at the tubercle of the atlas’s anterior arch (with its extension to the extracranial basion termed the atlanto-occipital membrane) extends ventral to the entire spinal column to the sacrum Adherent to the the periosteum of vertebral bodies and the ventral intervertebral anulus fibrosus ventrally The ALL serves to restrain extension ➔ ALL is anterior to vertebral body ➔ prevents anterior dislocation Sacral Spine a triangular anteriorly concave bone bridges and shares loads between the spine and the pelvis through its complex articulations with: ○ superiorly: L5 (via facet articulations facing medially and posteriorly) ○ bilaterally: the ilium (via the synovial sacroiliac joints) ○ interiorly: the non–load-bearing four-level Posterior Longitudinal Ligament coccyx restrains spinal flexion Composed of five vertebrae fused both anteriorly courses along the vertebral bodies dorsally from the and ventrally axis (with its extension to the intracranial basion by early adulthood, the mature sacrum encases its termed the tectorial membrane) to the sacrum respective nerve roots in a central canal terminating primarily a stabilizer of adjacent levels, around S4, below which the sacral hiatus is found ○ deep layers - wider and thinner than where invested in periosteum; located over the ➔ Sacrum is also known as the tail bone annulus fibrosus ➔ tip of sacral spine- coccyx ○ superficial layers - span longer intervertebral intervals relative paucity of thoracic and central disk herniations - due to intervertebral fanning, greater thickness of thoracic region, and relative weakness of anulus fibrosus fibers posterolaterally, When PLL ossifies: → PLL thickens and expand in diameter → Reduction within the space/Narrowing of the spinal canal → Potentially compressing the spinal cord and nerves → Increase risk of spinal injury Paucity - rarely occur Ligamentum Flavum courses dorsal to the spinal cord Ligamentous Anatomy prevent hyperflexion The spine is further connected and kept in alignment by: attaches the laminae of adjacent levels ALL thickness increases from the rostral most ligament PLL at C2 toward the caudal ligament at L5– S1. ○ thickest - at its insertion in the posterosuperior caudal lamina and medially 3  ○ thinnest - superiorly and laterally at each → Filum terminale- holds nerve poles in place level. → The central canal is filled with CSF; from the fourth There is a deep, thin midline component that in ventricle, some CSF flows through a narrow many patients runs continuously the entire course passage called the obex and enters the central of the spine. canal of the spinal cord ligament thickness - increases from C2 to S1 Spinal Cord Tracts Medial-lateral topographic principle: ○ afferent pathways- enters at higher levels Spinal Cord and Spinal Nerves and remain lateral than lower levels ○ descending efferent- tracts innervating lower levels remain lateral, whereas more proximal groups synapse medially onto gray matter more proximally Corticospinal Tract Cortico (cortex) and Spinal (spine) “from cortex to spine” meaning - descending motor pathway Spinal cord - ensheathed in leptomeninges: The corticospinal or pyramidal motor tract has ○ pia, arachnoid, and dura first-order neuron cell bodies predominantly in layer Paired denticulate ligaments - attach spinal cord V of the primary motor (Brodmann area 4), to the arachnoid and dural sheath premotor, and supplementary motor cortices of the ○ 20-22 pairs brain CSF in continuity with the intracranial subarachnoid The axons of these upper motor neurons travel compartment bathes the cord and its proximal nerve through the corona radiata and posterior limb of the roots internal capsule, cerebral peduncle, and upper 31 pairs of ventral and dorsal roots brainstem before decussating in the medullary ○ emerge from the spinal cord on each side pyramids and traveling in the contralateral lateral per level corticospinal tract dorsolaterally in the spinal cord ○ combines into a mixed spinal nerve with A minority of axons descends instead as the dorsal and ventral components ipsilateral anterior corticospinal tract, which lies just these components exit the spinal lateral to the anterior median fissure before crossing canal below their correspondingly in the anterior white commissure at their level of named levels termination As a result of developmental ascent of the spinal cord relative to the vertebral column, there is a discrepancy in functional spinal cord segments relative to bony exit points in the vertebral column Conus medullaris - termination of spinal cord at L1-L2 in adults before fanning into the cauda equina ○ attached to the sacrum via filum terminale Structure in transverse section: ○ a small central CSF- filled canal - lined with ependyma ○ gray matter - butterfly-shaped; surrounds the CSF ○ white matter - surrounds the gray matter Width: widest in the cervical region ○ because of the combination of its substantial dorsal horns serving the upper extremities and the afferent white matter dorsal fasciculi innervated at all inferior levels lumbosacral enlargement - present from L2 to S3 Dorsal Column-Lemniscus because of this region’s motor functions The cell bodies of sensory neurons reside in the dorsal root ganglia. These neurons have specialized receptors that detect a range of stimulus modalities: ○ mechanical deformation ○ chemical perturbation ○ temperature derangement Their axons enter the spinal cord via the posterolateral tract These neurons project proprioception, fine touch, pressure, and vibration through: ○ gracilis (from the lower body below Additional Notes: around T6, the lateral component of the → Cervical spinal nerves are the exception, and they dorsal column) and exit above ○ cuneate (with first-order neurons residing → Pia mater- adherent to the parenchyma of the above T6 medially) ipsilaterally to their spinal cord respective nuclei in the medulla 4  The second-order neurons in the nucleus gracilis/cuneatus Vascular Anatomy ○ decussate as the internal arcuate tract before projecting as the medial lemniscus The cervical spine is intimately associated with the ○ innervate the ventral posterolateral extracranial vertebral arteries. thalamic nucleus (or the ventral posteromedial nucleus in the case of head Coursing from the subclavian artery via the longus sensation) colli and anterior scalene muscles, the second vertebral The third-order neurons project to the artery segment (V2) passes through the transverse contralateral primary sensory cortex via the foramina of C6 to C2 before coursing vertically toward posterior limb of the internal capsule the transverse foramen of C1, posteromedially around the C1 lateral mass, across the posterior arch of C1 superiorly and immediately posterior to each superior articulating process in the sulcus arteriae vertebralis (together with the C1 spinal nerve), and under the atlanto-occipital membrane before entering the intradural compartment. Spinothalamic Tract In the spinothalamic (part of the anterolateral) pathways, sensory information ascends one or two levels before synapsing on dorsal horn neurons, which then decussate in the anterior white commissure Second-order neurons relaying pain and temperature ○ ascend as - lateral spinothalamic tract Arterial Supply through the spinal cord and brainstem (as The spinal cord is supplied primarily by longitudinal the spinal lemniscus) and vessels: The paired posterior spinal arteries (PSAs) ○ synapse in - thalamic ventroposterolateral that run dorsolaterally and a single anterior spinal nucleus, whose neurons project to the artery (ASA) that runs ventrally. primary sensory cortex The anterior spinothalamic tract relays crude touch These anastomose in the Lazorthes basket. and pressure sensations via a similar pathway, with its predominantly white matter fasciculus located in The ASA originates from the union of bilateral the spinal cord’s ventral white matter, lateral to the vertebral artery branches, originating near their anterior corticospinal tract termination at the vertebrobasilar junction. These branches course ventral to the medulla and join to form a single vessel around the level of the foramen magnum, which then descends inferiorly in the anterior median fissure of the spinal cord. 5  As the ASA courses inferiorly, further contribution is Dermatomes provided by anterior segmental medullary (and Area of skin that is innervated by the sensory fiber sometimes radicular) arteries arising from the aorta, of a single spinal nerve with the largest branch termed the artery of Single dermatome may overlap adjacent Adamkiewicz, which generally arises between T9 dermatomes and L2 on the left side, although there is ○ destruction of a single spinal nerve does considerable variation. not produce obvious anesthesia Sulcal arteries originating from the ASA perforate the pia mater to supply the anterior one-half to - C3: Neck two-thirds of the spinal cord, including the anterior - C5: Deltoid and lateral corticospinal tracts, the anterior horns, - C6: Radial aspect of Forearm and Thumb and the anterolateral system, while sparing the - C8: Ulnar aspect of Thumb dorsal columns. - T4: Nipple Injury to the anterior spinal artery may lead to the - T8: Umbilicus anterior spinal artery syndrome, which consists - L1: Groin of paralysis, loss of fecal/urinary continence, and - L3: Knee loss of pain and temperature sensation below the - L5: Dorsal surface of Foot and Big toe level of the lesion, with relatively preserved vibratory sensation and proprioception. The paired PSAs originate from the vertebral artery or posterior inferior cerebellar artery. With additional contribution from posterior segmental medullary arteries, the PSAs supply the dorsal columns and dorsal horns of the spinal cord and the posterior spinal nerve roots. These posterior territories are also commonly supplied by radicular arteries, which arise from spinal branches of segmental vessels, enter the spinal canal via the intervertebral foramina, and divide into anterior and posterior radicular branches that travel with respective ventral and dorsal nerve roots toward sulcal artery anastomoses Of note, the midthoracic spine is typically a watershed zone between radicular arteries, making this area susceptible to ischemia in the setting of hypoperfusion. Venous Drainage Anatomy of the Spinal Cord Territory supplied by the PSAs is drained by the midline posterior spinal vein and paired posterolateral spinal veins, whereas the area supplied by the ASA is drained by the midline anterior spinal vein Across levels, these vessels form a venous plexus comprising midline anterior and median longitudinal veins and lateral longitudinal veins, which are in turn drained by the anterior and posterior radicular veins ➔ Dorsal nerve root: Sensory input; has dorsal root Radicular veins ultimately communicate with the ganglia. first epidural internal plexus and finally with the ➔ Ventral nerve root: Motor output; has no ventral root ganglia external venous plexus extravertebrally. The spinal column venous system, which has extensive anastomotic relations with retroperitoneal and thoracic compartments in what is known as the Baston venous plexus, is valveless Myotome Motor fibers of a spinal nerve innervate those muscles that lie beneath their respective dermatomes. C5-C6: Biceps brachii C5-C7: Brachioradialis C6-C8: Triceps C8-T1: Intrinsic hand muscles L2-L4: Quadriceps femoris S1-S2: Gastrocnemius 6