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Divisions of the Nervous System Spinal Cord, Spinal Nerves, & Reflexes Lab Anatomy and Physiology I Mary Catherine Flath, Ph.D. CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM (Brain & Spinal Cord; Interneurons) (Cranial and Spinal Nerves SENSORY/AFFERENT NEURONS (INPUT) MOTOR/EFFERENT NEURONS (OUTPUT) SOMATIC (Effectors: skeletal muscle; conscious) AUTONOMIC (Effectors: smooth muscle, cardiac muscle, glands; unconscious) PARASYMPATHETIC (maintains homeostasis; acetylcholine) SYMPATHETIC (Fight or Flight; norepinephrine) Copyright 2016 Dr. Mary Cat Flath BONES OF THE VERTEBRAL COLUMN PROTECT THE SPINAL CORD Spinal Cord Protection BONES MENINGES VERTEBRAL COLUMN DURA MATER ARACHNOID MATER PIA MATER CEREBROSPINAL FLUID Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Cervical Spine Cervical Spine The Vertebral Column: Spine Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 1 Spinal Cord Protection BONES VERTEBRAL COLUMN MENINGES Meninges of the Spinal Cord DURA MATER ARACHNOID MATER PIA MATER The dura mater of the spinal cord is not directly attached to the bone of the vertebrae CEREBROSPINAL FLUID Copyright 2016 Dr. Mary Cat Flath An epidural space is formed This space is filled with loose connective tissue and fat Provides a second protective cushion Copyright 2016 Dr. Mary Cat Flath Spinal Cord Protection BONES MENINGES CEREBROSPINAL FLUID Within spinal cord in central canal Around spinal cord in subarachnoid space We will learn circulation pathway for cerebrospinal fluid later Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Divisions of the Nervous System CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM (Brain & Spinal Cord; Interneurons) (Cranial and Spinal Nerves SENSORY/AFFERENT NEURONS (INPUT) MOTOR/EFFERENT NEURONS (OUTPUT) SOMATIC (Effectors: skeletal muscle; conscious) AUTONOMIC (Effectors: smooth muscle, cardiac muscle, glands; unconscious) PARASYMPATHETIC (maintains homeostasis; acetylcholine) SYMPATHETIC (Fight or Flight; norepinephrine) Copyright 2016 Dr. Mary Cat Flath Spinal Cord Structure Begins at foramen magnum Ends between L1 and L2 at point called the conus medullaris 31 segments named for vertebrae 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Copyright 2016 Dr. Mary Cat Flath 2 Spinal Cord Structure About thickness of thumb Enlarged cervical and lumbar regions 31 pairs of spinal nerves (PNS) arise from each of the 31 segments Spinal nerves below L2 form Cauda Equina Distal remnant of pia mater terminates as filum terminale Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath SPINAL CORD CROSS-SECTION Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 3 Spinal Cord Model 10 1 2 Copyright 2016 Dr. Mary Cat Flath 23 24 26/28 8 9> 3 5 (cross-section) 6 25 7 14 Copyright 2016 Dr. Mary Cat Flath Key to Spinal Cord Model 1. Posterior White Column 2. Lateral White Column 3. Anterior White Column 5. Posterior Gray Horn 6. Lateral Gray Horn 7. Anterior Gray Horn 8. Gray Commissure 9. Central Canal 10. Posterior Median Sulcus 14. Anterior Median Fissure 23. Dorsal Root 24. Dorsal Root Ganglion 25. Ventral Root 26. Spinal Nerve (mixed) 28. Ventral Ramus Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Key to Spinal Cord Photo 9 1 12 2 8 7 11 3 4 5 6 10 14 13 Copyright 2016 Dr. Mary Cat Flath 1. Posterior White Column 2. Lateral White Column 3. Anterior White Column 4. Posterior Gray Horn 5. Lateral Gray Horn 6. Anterior Gray Horn 7. Gray Commissure 8. Central Canal 9. Posterior Median Sulcus 10. Anterior Median Fissure 11. Dorsal Root Ganglion 12. Dorsal Root 13. Ventral Root 14. Spinal Nerve (mixed)/Ventral Ramus Copyright 2016 Dr. Mary Cat Flath 4 9 1 12 4 5 2 8 7 3 11 Structures on either side of the Spinal Cord (PNS) 1___________________ 2___________________ 3___________________ 4___________________ 5___________________ 6___________________ 7___________________ 8___________________ 9___________________ 10__________________ 11__________________ 12__________________ 13__________________ 14__________________ 6 10 14 13 Spinal nerves are formed from the fusion of a Dorsal root Cell bodies (of sensory neurons) form enlarged Dorsal Root Ganglion Ventral root Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Spinal Cord Functions Tracts of the Spinal Cord • conduit for nerve impulses to & from brain •White Matter houses Nerve Tracts • Ascending Tracts • Sensory impulses are carried in Posterior White Columns • Descending Tracts • Motor impulses are carried in Anterior White Columns • center for spinal reflexes • Gray Matter 11-8 Copyright 2016 Dr. Mary Cat Flath Spinal Cord Model 10 1 2 tracts conduct sensory impulses to the brain •Posterior White Columns • Descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands •Anterior White Columns Copyright 2016 Dr. Mary Cat Flath 6 7 14 23 24 Key to Spinal Cord Model 25 Copyright 2016 Dr. Mary Cat Flath 11-13 (cross-section) 26/28 8 9> 3 5 • Ascending 1. Posterior White Column 2. Lateral White Column 3. Anterior White Column 5. Posterior Gray Horn 6. Lateral Gray Horn 7. Anterior Gray Horn 8. Gray Commissure 9. Central Canal 10. Posterior Median Sulcus 14. Anterior Median Fissure 23. Dorsal Root 24. Dorsal Root Ganglion 25. Ventral Root 26. Spinal Nerve (mixed) 28. Ventral Ramus Copyright 2016 Dr. Mary Cat Flath 5 Spinal Cord Functions • conduit for nerve impulses to & from brain •White Matter houses Nerve Tracts • Ascending Tracts • Sensory impulses are carried in Posterior White Columns • Descending Tracts • Motor impulses are carried in Anterior White Columns • center for spinal reflexes • Gray Matter Copyright 2016 Dr. Mary Cat Flath 11-8 Copyright 2016 Dr. Mary Cat Flath Reflex Arcs – Simplest demonstration of nerve pathways Reflexes – automatic, subconscious responses to stimuli Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Withdrawal Reflex Knee-jerk Reflex • helps maintain posture Copyright 2016 Dr. Mary Cat Flath 11-9 • protective 11-10 Copyright 2016 Dr. Mary Cat Flath 11-11 6 Take a few minutes And test your Patellar reflex & Pupillary reflex. Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Divisions of the Nervous System CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM (Brain & Spinal Cord; Interneurons) (Cranial and Spinal Nerves SENSORY/AFFERENT NEURONS (INPUT) MOTOR/EFFERENT NEURONS (OUTPUT) SOMATIC (Effectors: skeletal muscle; conscious) AUTONOMIC (Effectors: smooth muscle, cardiac muscle, glands; unconscious) PARASYMPATHETIC (maintains homeostasis; acetylcholine) SYMPATHETIC (Fight or Flight; norepinephrine) Copyright 2016 Dr. Mary Cat Flath Peripheral Nervous System Definition of a nerve: A bundle of myelinated axons in the PNS •Cranial nerves arising from the brain • 12 pairs • Spinal nerves arising from the spinal cord • 31 pairs • All mixed 11-42 Copyright 2016 Dr. Mary Cat Flath Spinal Nerves Mixed nerves • 31 pairs • 8 cervical (C1 to C8) • • 12 thoracic (T1 to T12) • 5 lumbar (L1 to L5) • 5 sacral (S1 to S5) • 1 coccygeal (Co) Copyright 2016 Dr. Mary Cat Flath 11-54 Copyright 2016 Dr. Mary Cat Flath 7 Spinal Cord Model Spinal Nerve Structure 10 1 2 Dorsal root • axons of sensory neurons from the dorsal root ganglion Dorsal root ganglion • cell bodies of sensory neurons Ventral root • axons of motor neurons whose cell bodies are in spinal cord Spinal nerve • union of ventral root and dorsal root Copyright 2016 Dr. Mary Cat Flath 11-55 23 24 26/28 8 9> 3 5 (cross-section) 6 25 7 14 Copyright 2016 Dr. Mary Cat Flath Nerve Plexus Nerve plexus – complex networks formed by anterior branches (i.e. ventral rami) of spinal nerves; fibers of various spinal nerves are sorted and recombined Cervical Plexus C1-C4 Brachial Plexus C5-T1 Lumbosacral Plexus T12-S5 Copyright 2016 Dr. Mary Cat Flath Photo from NHC A&P Help I http://science.nhmccd.edu/biol/ap 1lab.htm Copyright 2016 Dr. Mary Cat Flath 11-57 Copyright 2016 Dr. Mary Cat Flath Divisions of the Nervous System CENTRAL NERVOUS SYSTEM PERIPHERAL NERVOUS SYSTEM (Brain & Spinal Cord; Interneurons) (Cranial and Spinal Nerves SENSORY/AFFERENT NEURONS (INPUT) MOTOR/EFFERENT NEURONS (OUTPUT) SOMATIC (Effectors: skeletal muscle; conscious) AUTONOMIC (Effectors: smooth muscle, cardiac muscle, glands; unconscious) PARASYMPATHETIC (maintains homeostasis; acetylcholine) SYMPATHETIC (Fight or Flight; norepinephrine) Copyright 2016 Dr. Mary Cat Flath 8 Name the structure 10 1 Let’s take practice quiz. 2 23 24 26/28 8 9> 3 5 6 25 7 14 Copyright 2016 Dr. Mary Cat Flath Key to Spinal Cord Model 1. Posterior White Column 2. Lateral White Column 3. Anterior White Column 5. Posterior Gray Horn 6. Lateral Gray Horn 7. Anterior Gray Horn 8. Gray Commissure 9. Central Canal 10. Posterior Median Sulcus 14. Anterior Median Fissure 23. Dorsal Root 24. Dorsal Root Ganglion 25. Ventral Root 26. Spinal Nerve (mixed) 28. Ventral Ramus Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 9 Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath How many bones per region? How many spinal nerves per region? Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Spinal Nerves mixed nerves • 31 pairs • 8 cervical (C1 to C8) • • 12 thoracic (T1 to T12) • 5 lumbar (L1 to L5) • 5 sacral (S1 to S5) • 1 coccygeal (Co) Copyright 2016 Dr. Mary Cat Flath 11-54 Copyright 2016 Dr. Mary Cat Flath 10 Photo from NHC A&P Help I http://science.nhmccd.edu/biol /ap1lab.htm Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath Photo from NHC A&P Help I http://science.nhmccd.edu/biol/ap 1lab.htm Name the components of a reflex arc. Copyright 2016 Dr. Mary Cat Flath 9 1 12 2 8 7 11 3 4 5 6 10 14 13 Copyright 2016 Dr. Mary Cat Flath Copyright 2016 Dr. Mary Cat Flath 11 Key to Spinal Cord Photo 1. Posterior White Column 2. Lateral White Column 3. Anterior White Column 4. Posterior Gray Horn 5. Lateral Gray Horn 6. Anterior Gray Horn 7. Gray Commissure 8. Central Canal 9. Posterior Median Sulcus 10. Anterior Median Fissure 11. Dorsal Root Ganglion 12. Dorsal Root 13. Ventral Root 14. Spinal Nerve (mixed)/Ventral Ramus Good luck studying for next week’s quiz! Copyright 2016 Dr. Mary Cat Flath 12