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Peripheral Nervous System 1: The Somatic System

Peripheral Nervous System 1: The Somatic System. Taken from and modified……. Lawrence M. Witmer, PhD Professor of Anatomy Dept. of Biomedical Sciences Heritage College of Osteopathic Medicine, Ohio University Athens, Ohio 45701 witmerL@ohio.edu. Grant’s Atlas 12 2009. neuron.

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Peripheral Nervous System 1: The Somatic System

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  1. Peripheral Nervous System 1: The Somatic System Taken from and modified…… Lawrence M. Witmer, PhD Professor of Anatomy Dept. of Biomedical Sciences Heritage College of Osteopathic Medicine, Ohio University Athens, Ohio 45701 witmerL@ohio.edu Grant’s Atlas 12 2009

  2. neuron glial cell Dichotomies 1. Tissues: neurons vs. glia 2. Position: CNS vs. PNS 3. Function 1: sensory vs. motor 4. Function 2: somatic vs. visceral Gray’s Anatomy 38 1999

  3. Neurons-a quick review • Dendrites: carry nerve impulses toward cell body • Axon: carries impulses away from cell body • Synapses: site of communication between neurons using chemical neurotransmitters • Myelin & myelin sheath: lipoprotein covering produced by glial cells (e.g., Schwann cells in PNS) that increases axonal conduction velocity • Demyelinating diseases: e.g., Multiple Sclerosis (MS) in CNS or Guillain- Barré Syndrome in PNS dendrites cell body axon with myelin sheath Schwann cell synapses Moore’s COA6 2010

  4. CNS vs. PNS Central Nervous System • brain & spinal cord • integration of info passing to & from the periphery Peripheral Nervous System • 12 cranial nerves • 31 pairs of spinal nerves • Naming convention changes at C7/T1 Collection of nerve cell bodies: • CNS: nucleus • PNS: ganglion Moore’s COA6 2010

  5. Sensory (Afferent) vs. Motor (Efferent) sensory (afferent) nerve CNS e.g., skin (pseudo-) unipolar neurons conducting impulses from sensory organs to the CNS motor (efferent) nerve CNS e.g., muscle multipolar neurons conducting impulses from the CNS to effector organs (muscles & glands) Gray’s Anatomy 38 1999

  6. Somatic vs. Visceral Langman’s Embryo 9 2004

  7. Sensory/Motor + Somatic/Visceral Somatic Nervous System Autonomic Nervous System

  8. Structure of the Spinal Cord gray matter (cell bodies) • dorsal (posterior) horn • ventral (anterior) horn white matter (axons) ventral rootlets dorsal rootlets meninges pia • arachnoid • dura • denticulate ligament dorsal root (spinal) ganglion subarachnoid space (CSF) • dura • arachnoid • pia meninges spinal nerve • dorsal primary ramus • ventral primary ramus ventral root Moore’s COA6 2010

  9. Structure of Spinal Nerves: Somatic Pathways dorsal ramus dorsal root ganglion dorsal root spinal nerve somatic sensory nerve (GSA) dorsal horn CNS inter- neuron somatic motor nerve (GSE) ventral horn ventral ramus ventral root white ramus communicans Mixed Spinal Nerve sympathetic ganglion gray ramus communicans

  10. Structure of Spinal Nerves: Somatic Pathways dorsal ramus dorsal root ganglion dorsal root spinal nerve somatic sensory nerve (GSA) dorsal horn CNS inter- neuron somatic motor nerve (GSE) ventral horn ventral ramus Somatic sensations • touch, pain, temperature, pressure • proprioception: joints, muscles Somatic motor activity: innervate skeletal muscles ventral root white ramus communicans Mixed Spinal Nerve sympathetic ganglion gray ramus communicans

  11. Somatic Nervous system • Clearly we can see that this aspect of the peripheral system gathers information from the senses or receptors which are simply organs that detect a change in the internal (bladder full) or external(change in temp/light intensity) and respond in some way. • The trigger to a “response” is simply called a stimulus. • The skin responds to many of these stimuli

  12. Skin/ears/eyes • Skin protects us from the outside world as the receptors are constantly alerting us as to the changes we need to respond to, to protect us. • The ear groups receptors- sound, and balance • The eyes clearly enable us to see-msgs are sent via the optic nerve • See pages 228/229

  13. Diagrams

  14. Autonomic Nervous System • Some activities without you knowing about them-breathing heartbeat sweating etc.-These are controlled by the autonomic nervous system. • There are two parts to this system: • The Sympathetic-speeds up body functions to increase efficiency • Parasympathetic-slows things down-works when you are at rest-returns the body to normal functioning These systems are complimentary or opposite to one another in function

  15. Function of the sympathetic Nervous System

  16. Functions of the Parasympathetic Nervous System • Increases blood flow to the digestive tract • Stimulates salivary glands and increases the rate of digestion • Reduces the diameter of the bronchioles when there is a reduced need for oxygen • Controls heart beat • Contracts the eye muscles and reduces the diameter of the pupil

  17. overview

  18. Responding to Stimuli • Page 231- reflex actions • Read and note • Draw basic diagram using text as a guide • (teacher to draw on white board)

  19. References Agur, A. M. R. and A. F. Dalley. 2009. Grant’s Atlas of Anatomy, 121th Edition. Lippincott, Williams & Wilkins, New York. Bannister, L. H. et al. 1999. Gray’s Anatomy, 38th Edition. Churchill Livingstone, New York. Moore, K. L. , A. F. Dalley, and A. M. R. Agur. 2010. Clinically Oriented Anatomy, 6th Edition. Lippincott, Williams & Wilkins, New York. Sadler, T. W. 2004. Langman’s Medical Embryology, 9th Edition. Lippincott, Williams & Wilkins, New York. Stern, J. T., Jr. 1988. Essentials of Gross Anatomy. Davis, Philadelphia.

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