Chapter 13 The Spinal Cord and Spinal Nerves Lecture Outline PNS Ganglia Nerves CNS Center Nucleus Neural cortex Tracts Columns / Funiculi Pathways Spinal cord Vertebral canal Vertebral foramen Spinal meninges 1. Dura mater Occipital bone Coccygeal ligament Epidural space 2. Arachnoid A. Arachnoid membrane B. Arachnoid trabeculae Subarachnoid space Cerebrospinal fluid (CSF) 3. Pia mater Denticulate ligaments Cross sectional anatomy Posterior median sulcus Anterior median fissure Central canal CSF Gray matter Posterior gray horn: sensory Anterior gray horn: somatic motor Lateral gray horn: ANS Gray commissure: decussation White matter Posterior white column / funiculus Anterior white column / funiculus Lateral white column / funiculus Tracts 1. Ascending tracts: sensory 2. Descending tracts: motor 3. Transverse tracts: decussation Spinal roots Dorsal root: sensory Dorsal root ganglion Ventral root: motor Intervertebral foramen Dorsal root + ventral root = spinal nerve Spinal nerves 31 pair: C1-C8 T1-T12 L1-L5 S1-S5 Co1 Cauda equina Lumbar puncture = spinal tap L3-L4 Intervertebral disc 1. Nucleus pulposus 2. Anulus fibrosis Herniated disc Slipped disc Nerve structure: 1. Epineurium 2. Perineurium Fascicles 3. Endoneurium Enlargements: cervical & lumbar Motor neurons Dermatome Nerve plexus Cervical plexus: C1-C5 neck & diaphragm Brachial plexus: C5-T1 pectoral girdle & upper limbs Lumbar plexus: T12-L4 pelvic girdle & lower limbs Sacral plexus: L4-S4 lower limbs Trauma & disorders Paralysis Parethesias Paraplegia Quadriplegia Organization of neural pathways Sensory neurons Motor neurons Interneurons Neuronal pools Neural circuits 1. Divergence 2. Convergence 3. Serial processing 4. Parallel processing 5. Reverberation Reflexes Simple reflex Reflex arc 1. Stimulus 2. Sensory neuron activation 3. Information processing 4. Motor neuron activation 5. Peripheral effector response Negative feedback Reflex classification 1. Development Amy Warenda Czura, Ph.D.1SCCC BIO130 Chapter 13 HandoutA. Innate reflexes B. Acquired reflexes 2. Processing site A. Spinal reflexes B. Cranial reflexes 3. Nature of response A. Somatic 1. Superficial somatic reflexes 2. Stretch reflexes B. Visceral / Autonomic reflexes 4. Complexity A. Monosynaptic reflex B. Polysynaptic reflex Common reflex examples 1. Patellar reflex Monosynaptic Type A fiber Muscle spindle 2. Withdrawl reflex A. Flexor reflex B. Reciprocal inhibition C. Crossed extensor reflex Amy Warenda Czura, Ph.D.2SCCC BIO130 Chapter 13 HandoutSpinal Meninges1. Dura Mater: outermost, dense collagen fibers, attaches to periosteum of occipital bone and coccyx by coccygeal ligament. Surrounded by the epidural space which contains blood vessels and adipose2. Arachnoid: middle, two layers: A. Arachnoid membrane: simple squamous epithelium, contacts dura mater B. Arachnoid trabeculae: collagen and elastin fibers that bind to pia mater, the fibers pass through the subarachnoid space which contains cerebrospinal fluid (CSF: for shock absorption and diffusion medium)3. Pia mater: innermost, fine mesh of collagen and elastin fibers bound to neural tissue, attached to arachnoid trabeculae, has denticulate ligaments that extend through arachnoid to dura mater to prevent lateral movement of the cordAll three layers are continuous with cranial meninges of the same name and theconnective tissue around the spinal nervesPosterior median sulcusAnterior median fissureCentral canal: contains CSF for diffusionGray matter: somas, neuroglia, unmyelinated axons Posterior gray horn: somatic and visceral sensory nuclei Anterior gray horn: somatic motor nuclei Lateral gray horn: throacic and lumbar only, visceral motor nuclei (ANS) Gray commissure: axons for decussationWhite matter: myelinated axons Posterior white column/funiculus Anterior white coulmn/funiculus Lateral white column/funiculus All 6 columns contain tracts: Ascending tracts: sensory to brain Descending tracts: motor from brain Transverse tracts: decussationAxons exit as spinal roots (dorsal + ventral = spinal nerve) Dorsal root: sensory axons from receptor to CNS Dorsal root ganglion: somas of the sensory neurons Ventral root: motor axons from CNS to effectorsSpinal Cord Cross Sectional AnatomyAmy Warenda Czura, Ph.D.3SCCC BIO130 Chapter 13 HandoutNerve Structure: dorsal root + ventral root + blood vessels + connective tissue1. Epineurium: outermost layer, dense collagen fibers2. Perineurium: partitions that extend inward from epineurium and divide axons into bundles called fascicles3.Endoneurium: innermost layer, thin collagen fibers that surround each axonNerve plexus = interwoven network of nervesCervical plexus: nerves C1-C5, innervate muscles of neck and diaphragmBrachial plexus: nerves C5-T1, innervate pectoral girdle and upper limbsLumbar plexus: nerves T12-L4, innervate pelvic girdle and lower limbsSacral plexus: nerves L4-S4, innervate lower limbsSpinal Nerve PlexusAmy Warenda Czura, Ph.D.4SCCC BIO130 Chapter 13 HandoutNeural Circuitsone neuron/pool to many(send single input to multiple locations in brain)many neurons/pools to one(allow conscious and subconscious control of same effector)stepwise, one neuron/pool tothe next(allow linear transmissionfrom one location to next)positive feedback loop(continues signaling until inhibited byanother neuron)divergence + serial processing(allow multiple things to occur at once)Amy Warenda Czura, Ph.D.5SCCC BIO130 Chapter 13 HandoutReflex Arc1. Stimulus activates receptor-receptor = specialized cell or dendrites ofsensory neuron-receptor responds to a particular type of stimuli2. Sensory neuron is activated-stimulation causes action potential on axon ofsensory neuron-nerve impulse travels into spinal cord via dorsalroot3. Information processing-simple case: sensory neuron synapses on motorneuron-more complex: sensory neuron synapses on