Transcript File
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 [email protected] Grant’s Atlas 12 2009 Dichotomies neuron 1. Tissues: neurons vs. glia 2. Position: CNS vs. PNS 3. Function 1: sensory vs. motor 4. Function 2: somatic vs. visceral glial cell Gray’s Anatomy 38 1999 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 GuillainBarré Syndrome in PNS dendrites cell axon with body myelin sheath Schwann cell Moore’s COA6 2010 synapses 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 Sensory (Afferent) vs. Motor (Efferent) sensory (afferent) nerve (pseudo-) unipolar neurons conducting impulses from sensory organs to the CNS e.g., skin motor (efferent) nerve multipolar neurons conducting impulses from the CNS to effector organs (muscles & glands) Gray’s Anatomy 38 1999 e.g., muscle Somatic vs. Visceral attribute Somatic System Visceral 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 perception conscious, voluntary unconscious, involuntary Langman’s Embryo 9 2004 Sensory/Motor + Somatic/Visceral Somatic Visceral Sensory (Afferent) somatic sensory visceral sensory [General Somatic Afferent (GSA)] [General Visceral Afferent (GVA)] Motor (Efferent) somatic motor visceral motor [General Somatic Efferent (GSE)] [General Visceral Efferent (GVE)] Somatic Nervous System Autonomic Nervous System Structure of the Spinal Cord white matter (axons) meninges pia • arachnoid • dura • gray matter (cell bodies) • dorsal (posterior) horn • ventral (anterior) horn denticulate ligament dorsal rootlets ventral rootlets dorsal root (spinal) ganglion subarachnoid space (CSF) Moore’s COA6 2010 ventral root • dura • arachnoid • pia meninges spinal nerve • dorsal primary ramus • ventral primary ramus Structure of Spinal Nerves: Somatic Pathways dorsal ramus dorsal root ganglion dorsal root spinal nerve dorsal horn somatic sensory nerve CNS interneuron (GSA) ventral somatic ramus motor ventral horn nerve (GSE) ventral root Mixed Spinal Nerve white ramus communicans sympathetic ganglion gray ramus communicans Structure of Spinal Nerves: Somatic Pathways dorsal ramus dorsal root ganglion dorsal root spinal nerve dorsal horn CNS interneuron (GSA) ventral horn Somatic sensations ventral root Mixed Spinal Nerve somatic sensory nerve ventral somatic ramus motor nerve • touch, pain, temperature, (GSE) pressure • proprioception: joints, muscleswhite ramus communicans Somatic motor activity sympathetic gray: ramus innervate skeletal muscles ganglion communicans 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 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 Diagrams Autonomic Nervous System • Some activities without you knowing about thembreathing 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 Function of the sympathetic Nervous System Organ Effect Eye Dilates pupil Heart Increases rate and force of contraction Lungs Dilates bronchioles Blood Vessels Constricts Sweat Glands Activates sweat secretion Digestive tract Inhibits –movement peristalsis Kidney Increases renin secretion Pg 230 text book 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 overview Responding to Stimuli • • • • Page 231- reflex actions Read and note Draw basic diagram using text as a guide (teacher to draw on white board) 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.