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

2. 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 neuron glial cell

3. Neurons-a quick review cell body dendrites axon with myelin sheath synapses Schwann cell Moore’s COA6 2010 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

4. CNS vs. PNS Moore’s COA6 2010 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

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

6. Somatic vs. Visceral attributeSomatic SystemVisceral System embryological origin of tissue “body wall:” somatic (parietal) mesoderm (dermatome, myotome) “organs:” splanchnic (visceral) mesoderm, endoderm examples of adult tissues dermis of skin, skeletal muscles, connective tissues glands, cardiac muscle, smooth muscle perceptionconscious, voluntaryunconscious, involuntary Langman’s Embryo 9 2004

7. Sensory/Motor + Somatic/Visceral SomaticVisceral Sensory (Afferent) somatic sensory [General Somatic Afferent (GSA)] visceral sensory [General Visceral Afferent (GVA)] Motor (Efferent) somatic motor [General Somatic Efferent (GSE)] visceral motor [General Visceral Efferent (GVE)] SomaticNervousSystemAutonomicNervousSystem

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

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

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

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 OrganEffect EyeDilates pupil HeartIncreases rate and force of contraction LungsDilates bronchiolesbronchioles Blood VesselsConstricts Sweat GlandsActivates sweat secretion Digestive tractInhibits –movement peristalsis–movement peristalsis KidneyIncreases renin secretionrenin Pg 230 text book

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.