Central Nervous System II- Spinal Cord and Pathways PDF

Central Nervous System II: Spinal Cord and Pathways Course Objectives Nervous: Describe how the body communicates with itself by identifying anatomical structures and tracing pathways of the nervous system in order to aid in medical diagnoses when these systems are com...

Central Nervous System II: Spinal Cord and Pathways Course Objectives Nervous: Describe how the body communicates with itself by identifying anatomical structures and tracing pathways of the nervous system in order to aid in medical diagnoses when these systems are compromised.  Learning Objectives 6. Compare the difference between neurons 1. Define and visually identify the gross involved in sensory and motor pathways; anatomical terms of the spinal cord (indicated Focus on roll and location of UMN, LMN, versus with a ) primary, secondary, and tertiary neuron’s, including the location of neuron cell bodies 2. Describe how spinal nerves are named in relation to the vertebral column and recall 7. Chart the primary functions of the pathways/tracts (listed below) and their the spinal nerves that comprise the cervical divisions and lumbosacral enlargements 8. Using a simple diagram to draw out the 3. Explain the development of the spinal cord following pathways; include the location of focusing on the differential growth between decussation the spinal cord and surrounding structures Dorsal column pathway and the role of the filum terminale Spinothalamic pathway 4. Compare the meningeal layers of the spinal Spinocerebellar pathway cord to those surrounding the brain and brain Corticobulbar tract stem, focusing on potential/real spaces Corticospinal tracts (lateral and anterior) 5. Visually identify the histological terms discussed in lecture (indicated with a ) 9. Recall the role of the indirect pathways, focusing on the location and roll of the cerebral nuclei and cerebellum Vertebral Canal Anatomy  LO 1 Contents of Vertebral Canal Spinal cord Spinal nerve roots/rootlets Spinal meninges Neurovascular structures KenHub  LO 1 Contents of Vertebral Canal Ventr al Spinal cord Spinal nerve roots/rootlets Spinal meninges Neurovascular Dorsal structures  Gross 4 1 LO 1 Anatomy: b d Spinal Cord c c a All 1. Gray matter 3 2 a. Anterior/ventral horn 4 b. Posterior/dorsal horn c. Commissure d d. Central canal b c c 2. White matter a 3. Ventral median fissure 4. Dorsal median sulcus 3 Clinically Oriented Anatomy, Moore et al.,  LO 2 Spinal Cord Pathway between body and brain Major reflex center Protected by surrounding structures. What are these? Nerve Spinal cord segments s exit Bilateral pair of spinal nerves here (PNS) Named for the intervertebral foramina spinal roots exit Cervical- nerves C1 - C8 Thoracic- nerves T1 - T12 Lumbar- nerves L1 - L5 Sacral- nerves S1-S5 Coccygeal- nerve Co1 Clinically Oriented Anatomy, Moore et al.,  LO 3 Development of the Spinal Cord A. Early in development spinal cord length matches vertebral canal Caudal eminence (tail) degenerates (wk 9) B. Spinal cord in vertebral canal of coccyx atrophies C. Vertebral canal grows more quickly than spinal cord during fetal period, cord “ascends” D. Filum terminale anchors spinal cord caudally - vestigial remnant of caudal eminence Before We Are Born, Moore et al., 2020  LO 1 and 2 Spinal Cord Continuous with medulla oblongata a. Conus medullaris - tapered caudal end between T5 and L3 b. Cauda equine - Spinal rootlets continuing inferiorly c. Filum terminale - Anchor at coccyx Two areas of enlargement related to the innervation of the limbs a Cervical enlargement- C4 to T1 b Brachial plexus Lumbosacral enlargement- T11 to L1 Lumbar plexus c Sacral plexus Gray’s Basic Anatomy, Moore et al., 2018  LO 1 and 4 Spinal Meninges and Cerebrospinal Fluid Same meningeal layers as CNS 1. Epidural space- real space between periosteum of vertebral canal and dura mater, filled with epidural fat, vessels 2. Dura mater Single layer- Forms dural sac and blends with epineurium on spinal nerves 3. Arachnoid mater 1. Subarchanoid space- real space between arachnoid and pia mater, filled with CSF 4. Pia mater Follows surface of spinal cord, spinal nerves, and vessels Anchors spinal cord in dural sac via denticulate ligaments and filum terminale  LO 1 and 4 Spinal Meninges and Cerebrospinal Fluid 1/2 Same meningeal layers as CNS 1. Epidural space- real space between periosteum of vertebral canal and dura mater, filled with epidural fat, vessels 3 Denticulate 2. Dura mater ligaments Single layer- Forms dural sac and blends with epineurium on spinal nerves 3. Arachnoid mater 1. Subarchanoid space- real space between arachnoid and pia mater, filled with CSF 4 4. Pia mater Follows surface of spinal cord, spinal nerves, and vessels Anchors spinal cord in dural sac via denticulate ligaments and filum terminale  LO 1 and 4 Spinal Meninges and Cerebrospinal Fluid Same meningeal layers as CNS 1. Epidural space- real space between periosteum of vertebral canal and dura mater, filled with 1 2 epidural fat, vessels b 2. Dura mater 3 Single layer- Forms dural sac and blends with epineurium on spinal nerves 3. Arachnoid mater b. Subarchanoid space- real space between arachnoid and pia mater, filled with CSF 4. Pia mater Follows surface of spinal cord, spinal nerves, and vessels Anchors spinal cord in dural sac via denticulate ligaments and filum terminale  LO 5 Spinal Cord Histology All 1. Grey matter 2. White matter 3. Anterior horns 4. Posterior horns 5. Central canal 6. Anterior fissure  Image source here CNS Pathways  LO 6 Communication between CNS and Body Pathway = Tract (bundle of axons) + nucleus (group of neuron cell bodies) Tracts are paired and many are named for where they originate (prefix) and terminate (suffix) E.g., Spinocerebellar pathway – from the spine to the cerebellum Sensory pathway- ascending/afferent pathway Motor pathway- descending/efferent pathway 90% decussate (cross to opposite side) Contralateral – opposite side Some remain ipsilateral- same side  LO 6 Communication between CNS and Body Sensory pathways- from body to CNS Dorsal column system Spinothalamic pathway Spinocerebellar pathway Motor pathways- from CNS to body Direct Corticobulbar tract Corticospinal tract Indirect Lateral pathway Medial pathway Cerebral nuclei (basal ganglia) Cerebellum  Sensory Pathways: From body to brain https://open.oregonstate.education/aandp/chapter/14-5-sensory-and-motor-pathways/  LO 6/7 Sensory (Ascending) Pathways Receives information from skin, muscles, and joints Sensory receptors conduct nerve impulses to CNS via Three types of sensations dorsal horn of spinal detected, each with its own spinal cord cord pathway Sensory information 1. Discriminative touch- is processed and skin: uses pressure, touch, and vibration to determine filtered before textures and shapes of arriving in the unseen objects cerebrum 2. Proprioception- muscles and joints: detect position of Which structure of the joints stretch in muscles, and diencephalon is tension in tendons responsible for filtering sensory information?? 3. Temperature and pain (and  LO 6 Anatomy of Sensory Pathways Use 2 or 3 neurons to transmit information from body to brain 3 1. Primary neuron (first order) Sensory neuron with sensory receptor Cell bodies in dorsal root or cranial nerve ganglia Project to secondary neuron in CNS 2. Secondary neuron (second order) Interneuron Cell bodies- posterior horn of spinal cord or brainstem nucleus 2 1 Fibers will always decussate then synapse Project to Thalamus- conscious sensation Discriminative touch; Cerebellum- unconscious proprioception proprioceptio n 3. Tertiary neuron (third order) Interneuron 1 Cell bodies – thalamus Project to primary somatosensory cortex  LO 7 Dorsal Column Sy stem What does it do? Proprioception of limb position Discriminative touch- precise pressure and vibration Divisions 1. Cuneate fasciculus- all sensory above T6, except face Upper limb, superior trunk, neck, and posterior head Synapses on nucleus cuneatus 2. Gracile fasciculus- all sensory below T6 Lower limb and inferior trunk Synapse on nucleus gracilis Divisions join as one in brainstem as medial lemniscus  LO 8 Dorsal Column System Cerebrum 1. Primary neurons – cell bodies in dorsal root ganglia- enter spinal cord via dorsal root – ascends in spinal cord, ipsilateral to sensory reception in body Brainstem 2. Travel then synapse in medulla on to secondary neuron cell bodies 3. Decussate in medulla oblongata 4. Synapse in thalamus on to tertiary neuron cell bodies Spinal cord 5. Axons carry sensory information T6 to primary somatosensory cortex, contralateral to sensory receptor origin  LO 8 Dorsal Column System Cerebrum 1. Primary neurons – cell bodies in dorsal root ganglia- enter spinal cord via dorsal root – ascends in spinal cord, ipsilateral to sensory reception in body 2. Travel then synapse in medulla on to secondary neuron cell bodies Brainstem 3. Decussate in medulla oblongata 4. Synapse in thalamus on to tertiary neuron cell bodies 5. Axons carry sensory information to primary somatosensory cortex, contralateral to sensory receptor Spinal cord origin  LO 7 Spinothalamic Pathway Thalamus (Anterolateral System) Midbrain What does it do? Crude touch and pressure Pons Pain, temperature, and itch Medulla Divisions Anterior- crude touch Lateral- pain and temperature Spinal cord  LO 8 Spinothalamic Pathway Cerebrum 1. Primary neurons cell bodies in dorsal root ganglia, enter spinal cord via dorsal root 2. Synapse in posterior horn on to secondary neuron Brainstem 3. Immediately decussate in spinal cord at entry level 4. Axons ascend spinal cord contralateral to sensory receptor origin 5. Synapse in thalamus on to tertiary Spinal cord neuron cell bodies T6 6. Axons to primary somatosensory cortex  LO 8 Spinothalamic Pathway Cerebrum 1. Primary neurons cell bodies in dorsal root ganglia, enter spinal cord via dorsal root 2. Synapse in posterior horn on to secondary neuron 3. Immediately decussate in spinal cord Brainstem at entry level 4. Axons ascend spinal cord contralateral to sensory receptor origin 5. Synapse in thalamus on to tertiary neuron cell bodies Spinal cord 6. Axons to primary somatosensory cortex  LO 7 Spinocerebellar Pathway What does it do? Proprioceptive information about body movement coordination to cerebellum Divisions Posterior spinocerebellar tract- lower limbs, trunk, and upper limbs, axons do not decussate Anterior spinocerebellar tract- inferior trunk and lower limb, some axons decussate Why is the crossover of sensory input in this pathway important?  LO 8 Spinocerebellar Pathway Cerebellum 1. Primary neuron enter dorsal root Brainstem 2. Synapse immediately on cell bodies of secondary neurons in posterior horn to a. Posterior spinocerebellar tract- ascend in spinal cord, travel through From arm cerebellar peduncles to cerebellum No decussation b. Anterior spinocerebellar tract- some decussates immediately in spinal cord, ascend spinal cord, cerebellar peduncles, into Spinal cord cerebellum From leg Explain why there is no tertiary (third order) neuron.  Sensory Function: Receptors Exteroceptors- respond to stimuli outside the body Dorsal Column Merkel cells- light touch Meissner corpuscles- light touch Pacinian corpuscles- touch, pressure, and vibration Ruffini endings- pressure in joints Krause bulbs- pressure and vibration Spinothalamic Free nerve endings- pain and temperature Motor Pathways  Motor Pathways LO 6 Descending projection that originate in cerebral cortex and brainstem Always at least two motor neurons Upper motor neuron (UMN) Cell bodies in cerebral cortex or brainstem nuclei Synapse on interneurons or lower motor neurons Excite or inhibit lower motor neuron Fibers will always decussate then synapse Lower motor neuron (LMN) Cell bodies in anterior horn of spinal cord (innervate limb and trunk) or brainstem cranial nerve nuclei (head and neck) Axons exit CNS and synapse on skeletal muscle Only excitatory Direct- primary motor cortex UMN synapse on LMN in brainstem or spinal cord  LO 7/8 Corticobulbar Tract What does it do? Voluntary movement of cranial muscles Axons travel from primary motor cortex, exit brainstem as cranial nerves 1. UMN cell bodies in primary motor cortex, axons travel to brainstem Midbrain 2. Some UMN decussate in brain stem, just prior to synapsing on LMN cell bodies in cranial nerve Pons nuclei Most cranial nerve nuclei receive bilateral input from cerebral cortex (contralateral and ipsilateral input to Medulla muscle) 3. Exit to form cranial nerves  LO 7/8 Corticospinal Tra ct What does it do? Voluntary movement of limbs and axis Axons travel from primary motor cortex to body through anterior horn of spinal cord Midbrain Somatotopy of gray matter in anterior Pons horn Divided into flexors/extensors and proximal/distal Medulla Lateral Divisions- separate in brainstem Medulla Lateral corticospinal tract- limb muscles Spinal cord Anterior corticospinal tract- axial muscle Anterior  LO 7/8 Corticospinal Tract Cerebrum 1. UMNs leave primary motor cortex, descends to pyramids in medulla a. Lateral corticospinal tract- limb muscles Brainstem Decussate at pyramids 2. Descends in spinal cord 3. Travels through anterior horn of spinal cord synapse on LMN prior to exiting Spinal cord T6 b. Anterior corticospinal tract- axial muscle Decussate in spinal cord just prior to exiting  LO 7/8 Corticospinal Tract Cerebrum 1. UMNs leave primary motor cortex, descends to pyramids in medulla a. Lateral corticospinal tract- limb muscles Decussate at pyramids Brainstem 2. Descends in spinal cord 3. Travels through anterior horn of spinal cord synapse on LMN prior to exiting b. Anterior corticospinal tract- axial muscle Spinal cord Decussate in spinal cord just prior to exiting  Indirect Motor Pathways and Others  LO 9 Indirect Motor Pathways Named indirect because they involve nuclei in the brainstem and cerebrum Complex route in brainstem and cerebrum before entering spinal cord as UMN Modify or help control the pattern of somatic motor activity by exciting or inhibiting upper or lower motor neurons Synapse with LMN or interneurons in spinal cord prior to exiting  Indirect LO 9 pathway Motor Pathways- Indirect Lateral pathway Regulates and controls precise, discrete movement and tone in flexor muscles of the limb Direct Think precise control of pathway arms and hands Rubrospinal tract Medial pathway Muscle tone and gross movement extensor muscles of the head, neck, limbs, and trunk Think posture and locomotion Reticulospinal, Tectospinal, and Vestibulospinal tracts Cognitive Functions of the Premotor Systems |  LO 9 Motor Pathways Cerebral nuclei (basal ganglia) Receives input from motor, sensory, association cortical areas, and limbic system Provide reflexive, patterned background movement needed for conscious motor activities, motor commands from other nuclei E.x., Walking Differs from cerebellum because primarily receive motor input rather than motor and sensory input  LO 9 Motor Pathways Cerebellum Continuously receiving information from sensory and motor pathways Regulates the functions of motor pathways Unconsciously perceives the state of the body, receives plan for movement, checks to see if activity was carried out correctly If movement is not correct, generates error-correcting signal by sending signals to premotor and primary motor cortex Response is transmitted to efferent motor neuron