2.4 Cerebellum & Spinal cord ANAT 2001A 2024.pdf

Cerebellum & Spinal Cord Ms. P.M Mamali Office: 2B11 Email: [email protected] ANAT2001A Conquer the Wits edge! 2024 Disclaimer & resources: Please note that these lecture notes are a...

Cerebellum & Spinal Cord Ms. P.M Mamali Office: 2B11 Email: [email protected] ANAT2001A Conquer the Wits edge! 2024 Disclaimer & resources: Please note that these lecture notes are a guideline only. Students are advised to supplement with information from the prescribed textbooks, completion of tutorial and practical questions, and other relevant resources. Prescribed textbook: Grays Anatomy the Anatomical Basis of Clinical Practice, by Stranding, 41st edition, 2016 Additional textbooks: Clinically Orientated Anatomy by Moore, Dalley and Agur, 8th edition, 2018. Human Anatomy and Physiology by Marieb and Hoehn, 10th edition, 2017  LEARNING OBJECTIVES: By the end of this lecture, students should be able to:  With regards to cerebellum, describe location of cerebellum structure of cerebellum Hemispheres, fissures & lobes of cerebellum Cortex & white matter  Name most important Afferent & Efferent connections Nuclei location & connections of peduncles Functions of cerebellum  Describe & draw the structure of spinal cord Location & length in adults vs children Shape, enlargements, ligaments, coverings, grooves on surface of spinal code Central canal, grey & white matter Segments Emergence of spinal nerve roots  Describe & draw structure of typical spinal nerve, transverse sectonal of a transverse section of spinal cord  Cerebellum Largest structure of hindbrain Found within posterior cranial fossa Covered by tentorium cerebelli of dura mater Composed of 2 large hemispheres Connected by vermis in midline Functionally: Plays a role in maintaining balance Influencing posture Coordinating movements by synchronizing contraction & relaxation of voluntary muscle  Cerebellum relations Lies posterior to pons & medulla inferior to posterior part of cerebrum Connects to posterior surface of brainstem Via superior, middle & inferior cerebellar peduncles forms roof of 4th ventricle (Anteriorly) On its surface, cerebellum has convoluted folds/folia Separated by fissures  Fissures & Cerebellar anatomical divisions Fissures: 2 fissures serve as landmarks to divide cerebellum into 3 lobes Primary fissure: (superiorly) Separates anterior lobe from posterior lobe Posterolateral fissure (Anteriorly & inferiorly) defines the structures of flocculonodular lobe Flocculus from each hemisphere & nodule of vermis Horizontal fissure Borders superior & inferior surfaces of cerebellum  Cerebellar cortex Cerebellar cortex thin layer of gray matter superficially highly convoluted, forming transversely oriented folia Branching pattern of folia Arbor vitae Within cortex lie cell bodies, dendrites & synaptic connections of cerebellar neurons. cellular organization of cortex  Cerebellar cortex Divided histologically into 3 layers: molecular layer> outer, fibre-rich Purkinje cell layer> intermediate Control motor movements inner granular layer> dominated by granule cell  Cerebellum: white matter Central core white matter Cerebellar Nuclei Found deep within white matter of each hemisphere 4 masses of cerebellar nuclei From lateral to medial Dentate Emboliform Globose Fastigial Emboliform & Globose = interposed nuclei  Cerebellum Output from cerebellum originates from 1 of 4 nuclear complexes Before leaving through superior cerebellar peduncle (predominantly) Output from each cerebellar hemisphere coordinates movements on ipsilateral side of body  Cerebellar functional divisions Cerebellar cortex can be divided into 3 functional areas Vermis Influences movements along axis of body E.g neck, trunk, abdomen & pelvis Intermediate zone Controls muscles of distal upper & lower limbs Lateral zone Participates in motor planning To coordinate sequential movements of entire body Input to these functional areas of cerebellar cortex Come from cerebral cortex, spinal cord & brainstem By passing through middle & inferior cerebellar peduncles (predominantly) https://www.google.com/url?sa=i&url=https%3A%2F%2Fteachmeanatomy.info%2Fneuroanatomy%2Fstruct ures%2Fcerebellum%2F&psig=AOvVaw0iSW4MI9Qgyf_k2XFABWzj&ust=1714479155841000&source=image s&cd=vfe&opi=89978449&ved=0CBIQjRxqFwoTCKD_zdyy54UDFQAAAAAdAAAAABAE  FUNCTIONAL ANATOMY OF CEREBELLUM Archicerebellum = flocculonodular lobe & fastigial nucleus Principal connections are with vestibular & reticular nuclei of brainstem maintenance of equilibrium Paleocerebellum = vermis & paravermal area + globose & emboliform nuclei. Receives fibres from spinocerebellar tracts projects to red nucleus of midbrain. Neocerebellum = cerebellar hemisphere & dentate nucleus receives afferents from pons projects to ventral lateral nucleus of thalamus.  Afferent Cerebellar Pathways Input from cerebral cortex to cerebellum primarily involved in voluntary muscle control coordination of movement Axonal projections from cerebral cortex, destined for cerebellar Descend through internal capsule Terminate on pontine nuclei Axons from pontine nuclei then cross over as Transverse fibers to enter contralateral cerebellum Through middle cerebellar peduncle  Afferent Cerebellar Pathways Input from spinal cord to cerebellum Conveys information from muscles & joints Influence muscle tone & posture Primary spinal cord pathways with connections to cerebellum Anterior/ventral spinocerebellar tracks Posterior/dorsal spinocerebellar tracks These tracks originate from joint & cutaneous mechanoreceptors Ascend through spinal cord to enter ipsilateral cerebellum primarily through inferior cerebellar peduncle  Afferent Cerebellar Pathways Cerebellar input arises vestibular nuclei & reticular formation in brainstem Involved in reflexive maintenance of balance  nuclei send axonal projections to ipsilateral cerebellum through inferior cerebellar peduncle  Efferent Cerebellar Pathways Output from cerebellum originates from 1 of 4 deep cerebellar nuclei Largest collection of fibers leaving cerebellum originates from dentate nucleus Axons from this nuclear complex project to contralateral ventral nucleus of thalamus After decussating in superior cerebellar peduncle Then axons of thalamic nuclei project to motor cortex influences posture & movement  Efferent Cerebellar Pathways Interposed nuclei Have a similar course as axons from dentate But with addition of another synaptic target Axons from interposed nuclei decussate in superior cerebellar peduncle To synapse on contralateral ventral nucleus of thalamus & contralateral red nucleus in midbrain Axons leaving red nucleus descend to inferior olivary nucleus in medulla Axonal projections from interposed nuclei Monitors & correct motor activity of upper & lower extremities  Efferent Cerebellar Pathways Axons from fastigial nucleus project To vestibular nuclei, reticular formation, contralateral ventral nucleus of thalamus & contralateral tectum Vestibular axons pass through inferior cerebellar peduncle to reach Also, going through inferior cerebellar peduncle axons heading to reticular formation Ascending in superior cerebellar peduncles are axons that will  Lesions of cerebellum Midline lesion of cerebellum (e.g tumour) leads to loss of postural control impossible to stand or sit without toppling over despite preserved coordination of limbs. Unilateral cerebellar hemispheric lesion causes ipsilateral incoordination of arm ( intention tremor )& leg causing unsteady gait Bilateral dysfunction of cerebellum caused by alcoholic intoxication, hypothyroidism, inherited cerebellar degeneration ( cerebellar ataxia ) causes slowness & scanning of speech ( dysarthria ) incoordination of both arms & staggering, unsteady gait  Questions?  1. Describe the histology of the cerebellar cortex 2. Name brain masses/ nuclei are found in the cerebellum? 3. Which cerebellar nuclei makes up interposed nuclei? SPINAL CORD Ms. P.M Mamali Office: 2B11 Email: [email protected]  Vertebral column 30 vertebrae 7 cervical 12 thoracic 5 lumbar 5 sacral = 1 sacrum 4 coccygeal =1 coccyx 31 pairs of spinal nerves 8 cervical, 12 thoracic, 5 lumbar, 5 sacral & 1 coccygeal  Spinal cord Continuous with medullar oblongata near foramen magnum at base of skull Cylindrical in shape Occupies vertebral canal of vertebral column to LI /LII vertebral level in an adult Longer in children Occupies entire vertebral canal before birth LIII at birth Filum terminale Fibrous band from conus medullaris to periosteum of coccyx Fixate & stabilize distal spinal cord Conus medullaries Conical terminal end of spinal cord Cauda aquina Lower spinal nerves  Lumber puncture & epidural anaesthesia Lowest part of spinal canal does not contain spinal cord hollow needles can be safely inserted into the subarachnoid space to remove CSF for diagnostic purposes ( lumbar puncture ) to inject radio-opaque substances for radiological delineation of the spinal canal & contents ( myelography ). anaesthetics may be introduced into epidural space in surgical procedures ( epidural block ).  External features Anterior & posterior roots Formed by a coalition of series of rootlets that emerge from spinal cord Converge to form 31 pairs of spinal nerves Extends the length of spinal cord 2 regions of enlargement Found along length of spinal cord accommodate neurons innervating upper & lower extremities Cervical enlargement Extends from C5-T1 Innervates upper extremities Lumbar enlargement Extends from L2-S3 Innervates lower extremities  Nerve plexus Cervical plexus Brachial plexus Lumbar plexus Sacral plexus  Spinal meninges Spinal cord is surrounded by 3 meninges Dura mater Arachnoid mater Pia mater Spinal dura mater continuous with cranial dura mater Separated from bony vertebral canal epidural space Arachnoid mater not tightly adherent to dura mater Potential space = Subdural space  Spinal meninges Subarachnoid space created by loose relationship of arachnoid & pia mater Extends inferiorly to level of SII vertebra Given that spinal cord terminates at LI/LII vertebra, lower termination point of subarachnoid space creates a safe & enlarged space for accessing CSF in clinical setting  Spinal meninges Pia mater is highly vascular Adherent to surface of spinal cord Denticulate ligament Formed by pia mater Midway between anterior & posterior roots At posterior & anterior rootlets, Sleeve-like projections from denticulate ligament extend Out through arachnoid mater to attach dura mater  Anchor & position spinal cord within central area of subarachnoid space  Spinal nerve Dorsal & ventral roots Piece dura mater separately Run through epidural space Unite at ganglia to form spinal nerve Cauda aquina Roots of lumbar & sacral spinal nerves  External features Fissures & sulci Found on anterior & posterior surface of spinal cord Run longitudinally Anterior median fissure: Deep separation run along midline of anterior surface of spinal cord Posterior median sulcus Shallow separation Run along posterior of spinal cord Flanked on either side by posterolateral sulcus  Internal features Cross-section of spinal cord reveals inner H-shape gray matter Consisting of neuronal cell bodies Surrounded by white matter Outer white mater Composed of myelinated neuronal axons Has central canal Filled with CSF Continuous superiorly with 4th ventricle Anterior horns of gray matter Contain cell bodies of motor neurons Posterior horns Contain cell bodies receiving sensory information  Internal features Intermediolateral cell column Enlargement of lateral portion of gray matter Can be seen in T1-L2 region of spinal cord Enlarges to accommodate preganglionic cell bodies of sympathetic nervous system Gray matter is divided into 10 zones Rexed’s laminae Relates to ascending & descending tracts within spinal cord  Internal features Anterior funiculus (AF) of white matter Consists of motor axons Posterior funiculus (PF) Consists of axons conveying sensory information Lateral funiculus (LF) mixture of axons conveying both sensory & motor information https://www.google.com/url?sa=i&url=https%3A%2F%2Fnba.uth.tmc.edu%2Fneuroanatomy%2FL6%2FLab06p01_index.html&psig=AOvVaw00hfhPzaUKj OkTajrzN7Qc&ust=1714473769018000&source=images&cd=vfe&opi=89978449&ved=0CBAQjRxqFwoTCOjPqtOe54UDFQAAAAAdAAAAABAD  Spinal tracts in spinal cord Has ascending & descending tracts coursing through it Connect with brain to convey sensory (afferent) & motor (efferent) information For facilitation of movement, reflexes, sensory input & feedback mechanisms  Ascending tracts in spinal cord Sensory information enters CNS from peripheral sensory receptors Conducted through neurons that synapse targets in spinal cord, cerebral cortex & other brain structures Sensory modalities caried in these pathways include Pain, temperature, tactile & proprioception input Conscious perception of sensory input is transmitted Through neuronal pathways reach primary somatosensory region of cerebral cortex. Subconscious sensory input Transmitted to other structures of cerebellum Ascending tracts in spinal cord 2 somatosensory pathways ascend within spinal cord reach cerebral cortex Anterolateral pathways: Conveys sensations of pain, temperature & crude touch E.g Spinothalamic, spinoreticular & spinomesencephalic tracts Posterior column-medial lemniscus pathway Conveys sensations of discriminative/ fine touch, vibrations & conscious proprioception Descending tracts in spinal cord Involved in voluntary movements, postural movements & coordination of head, neck & eye movements Originates from cerebral cortex & brain stem Influenced by sensory input & feedback circuitry from Cerebellum & basal ganglia Composed of tracts of Lateral motor systems Eg Lateral corticospinal tract & Rubrospinal tract Medial motor systems Anterior corticospinal tracts, Tectospinal tract, Vestibulospinal tract, Reticulospinal tracts Vascular supply of spinal cord Blood supply Vertebral arteries 1 Anterior spinal artery Descends along anterior median fissure 2 posterior spinal arteries Descends in posterolateral sulcus Venous drainage: Longitudinally running channels connect anterior & posterior spinal veins on surface of cord