BIOL 111 Peripheral Nervous System PDF

BIOL 111:The Peripheral Nervous System Instructor: Pamela Paynter-  Discuss sensory receptors and their classification  Describe the structure of a nerve  Identify the cranial and spinal nerves  Outline the various nerve plexuses  Discuss various spinal...

BIOL 111:The Peripheral Nervous System Instructor: Pamela Paynter-  Discuss sensory receptors and their classification  Describe the structure of a nerve  Identify the cranial and spinal nerves  Outline the various nerve plexuses  Discuss various spinal reflexes  Central nervous system (CNS) Peripheral nervous system (PNS) Brain and spinal cord Cranial nerves and spinal nerves Integrative and control centers Communication lines between the CNS and the rest of the body Sensory (afferent) division Motor (efferent) division Somatic and visceral sensory Motor nerve fibers nerve fibers Conducts impulses from the CNS Conducts impulses from to effectors (muscles and glands) receptors to the CNS Somatic sensory Somatic nervous Autonomic nervous fiber system system (ANS) Skin Somatic motor Visceral motor (voluntary) (involuntary) Conducts impulses Conducts impulses from the CNS to from the CNS to skeletal muscles cardiac muscles, Visceral sensory fiber smooth muscles, Stomach and glands Skeletal muscle Motor fiber of somatic nervous system Sympathetic division Parasympathetic division Mobilizes body systems during activity Conserves energy Promotes house- keeping functions during rest Sympathetic motor fiber of ANS Heart Structure Function Sensory (afferent) division of PNS Parasympathetic motor fiber of ANS Bladder Motor (efferent) division of PNS (Meeking, 2010).   Ganglia – neuron cell bodies  Peripheral nerves – neuronal axons  PNS neuroglia  Satellite cells  Enclose neuron cell bodies in ganglia  Schwann cells  Cover peripheral axons (Santa Monica College, n.d.).  By Stimulus Type  By location  By Structural Complexity By Stimulus Type:  Mechanoreceptors  Chemoreceptors  Respond to  Respond to mechanical force chemicals in (touch, pressure) solution  Thermoreceptors  Nociceptors  Sensitive to  Respond to temperature potentially changes damaging stimuli  Photoreceptors that results in pain  Respond to light energy By location:  Exteroceptors  Sensitive to stimuli arising from outside body  Interoceptors  Or visceroreceptors, from internal viscera  Proprioceptors  Monitor degree of stretch in skeletal muscles, tendons, joints and ligaments (Los Angeles Valley College, n.d.). 7 By Structural Complexity :  Simple  Majority  Modified dendritic ending of sensory neurons  Complex  Sense organs associated with special senses 8  Nerves and ganglia outside the central nervous system  Nerve = bundle of neuron fibers  Neuron fibers are bundled by connective tissue (Bostwick-Taylor & Darlington, 2008).  Structure of a Nerve  Endoneurium surrounds each fiber  Groups of fibers are bound into fascicles by perineurium  Fascicles are bound together by epineurium (Marieb, 2003). Nerves of The PNS Sensory nerves Conduct impulses into brain or spinal cord Motor nerves Conduct impulses to muscles or glands Mixed (both sensory and motor) nerves Contain both sensory nerve fibers and motor nerve fibers Most nerves are mixed nerves ALL spinal nerves are mixed nerves (Shier, Butler & Lewis, 2009). 11  Cranial nerves arising from the brain Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera Spinal nerves arising from the spinal cord Somatic fibers connecting to the skin and skeletal muscles Autonomic fibers connecting to viscera (Shier, Butler & Lewis, 2009). 12  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Olfactory bulb Olfactory (I) Olfactory tract Optic (II) Optic tract Oculomotor (III) Trochlear (IV) Trigeminal (V) Vestibulocochlear (VIII) Abducens (VI) Hypoglossal (XII) Facial (VII) Vagus (X) Glossopharyngeal (IX) Accessory (XI) 13 (Shier, Butler & Lewis, 2009).  Remember: Cranial nerves are designated ‘C N’ Cranial nerves are designated with Roman numerals (I – XII) (Shier, Butler & Lewis, 2009). 14  12 pairs of nerves that mostly serve the head and neck  Only the pair of vagus nerves extend to thoracic and abdominal cavities  Most are mixed nerves, but three are sensory only (Bostwick-Taylor & Darlington, 2008).  I Olfactory nerve—sensory for smell  II Optic nerve—sensory for vision  III Oculomotor nerve—motor fibers to eye muscles  IV Trochlear—motor fiber to eye muscles (Bostwick-Taylor & Darlington, 2008).  V Trigeminal nerve—sensory for the face; motor fibers to chewing muscles  VI Abducens nerve—motor fibers to eye muscles  VII Facial nerve—sensory for taste; motor fibers to the face  VIII Vestibulocochlear nerve— sensory for balance and hearing (Bostwick-Taylor & Darlington, 2008).  IX Glossopharyngeal nerve—sensory for taste; motor fibers to the pharynx  X Vagus nerves—sensory and motor fibers for pharynx, larynx, and viscera  XI Accessory nerve—motor fibers to neck and upper back  XII Hypoglossal nerve—motor fibers to tongue (Bostwick-Taylor & Darlington, 2008). CN I Olfactory Olfactory Smell epithelium CN II Optic Retina Vision CN III Occulomotor Midbrain Eye movement; accommodation CN IV Trochlear Midbrain Eye movement (superior oblique) CN V Trigeminal Pons Sensation to face; chewing CN VI Abducens Pons Eye movement ( lateral rectus) CN VII Facial Pons Facial expression; taste to anterior 2/3 of tongue CN VIII Vestibulocochlear Pons Hearing & balance CN IX Glossopharyngeal Medulla Salivation; swallowing; taste to posterior 1/3 of tongue CN X Vagus Medulla Digestion; taste to pharynx CN XI Accessory Medulla Movement of trapezius & SCM CN XII Hypoglossal Medulla Movement of tongue 19 (Shier, Butler & Lewis, 2009). (Bostwick-Taylor & Darlington, 2008). Spinal Nerves  There is a pair of spinal nerves at the level of each vertebrae. (Marieb, 2003).  Spinal Nerves  Part of the peripheral nervous system  31 pairs attach through dorsal and ventral nerve roots  Lie in intervertebral foramina 22 (Los Angeles Valley College, n.d.).  (Santa Monica College, n.d.).  Connected to the spinal cord via roots (bundles of axons)  Posterior root = sensory axons into the posterior gray horn  Anterior root = motor axons from the anterior gray horn  Before the posterior root is the dorsal root ganglion - cell bodies of incoming sensory neurons (axons continue on to form the root)  Emerge from intervertebral foramina as mixed nerves Dorsal roots – sensory fibers arising from cell bodies in dorsal root ganglia Ventral roots – motor fibers arising from anterior gray column of spinal cord (Los Angeles Valley College, n.d.). 24  Dorsal and ventral roots join in an intervertebral foramen forming spinal nerve  After passing through intervertebral foramina the spinal nerve branches into the four rami (sing., ramus): Dorsal and ventral rami (somatic) and meningeal branches Rami communicantes (visceral) 25 (Los Angeles Valley College, n.d.).  Dorsal rami -sensory/motor- serve the muscles and skin of the posterior trunk  Back, from neck to sacrum, innervated in a neatly segmented pattern: horizontal strip at same level as emergence from spinal cord  Ventral rami Sensory/motor - serve the muscles and skin of the lateral and anterior trunk  In thorax only, a simple segmented pattern as intercostal nerves  Also serve the limbs (Los Angeles Valley College, n.d.). 26 Meningeal branches = x These branch from the spinal nerve and re-enter the intervertebral foramen to innervate the meninges and blood vessels within. Rami communicantes =  Third branch from the spinal nerve  -carries nerves of the ANS (Santa Monica College, n.d.).  Dorsal Root of SN Ventral Root of SN SPINAL NERVE Dorsal Ventral Rami Ramus Ramus Communicantes Sensory – IN Sensory – IN Signals to and from the Motor – OUT Motor – OUT ANS SKIN TRUNK VISCERA – cardiac and BACK MUSCLES LIMBS Smooth muscle (Santa Monica College, n.d.).  ALL are mixed nerves Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 31 pairs of spinal nerves: Posterior 8 cervical nerves view C1 C2 C3 C4 Cervical (C1 to C8) C5 nerves C6 C7 C8 T1 12 thoracic nerves T2 T3 T4 (T1 to T12) T5 T6 Thoracic T7 nerves 5 lumbar nerves T8 T9 T10 (L1 to L5) T11 T12 L1 5 sacral nerves Cauda equina L2 L3 Lumbar L4 nerves (S1 to S5) L5 S1 S2 1 coccygeal nerve S3 Sacral S4 nerves S5 Co Coccygeal nerve (Co or Cc) 29 (Shier, Butler & Lewis, 2009).  Networks of successive ventral rami that exchange fibers (crisscross & redistribute)  Why would this be protective?  Mainly innervate the limbs 30 (Los Angeles Valley College, n.d.).  Joining of ventral rami of spinal nerves to form nerve networks or plexuses Found in neck, arm, low back & sacral regions No plexus in thoracic region – intercostal nn. innervate intercostal spaces – T7 to T12 supply abdominal wall as well (Santa Monica College, n.d.).  Cervical  Brachial  Lumbar  Sacral 32 (Los Angeles Valley College, n.d.).  Cervical plexus (C1-C4) innervates the muscles and skin of the neck and shoulder most important: Its phrenic nerve* (C3-C5) is the sole motor supply of diaphragm: one reason why neck injuries are so dangerous – can be lethal * (respiratory arrest = stop breathing) (Irritation diaphragm spasms called hiccups) 33 (Los Angeles Valley College, n.d.).  Serves upper limbs and shoulder girdle  Arises primarily from C5-T1 34 (Los Angeles Valley College, n.d.).  Lumbar plexus - ventral rami of T12–L4  Sacral plexus – ventral rami of L4–S4  Innervate pelvic girdle and lower limbs (Santa Monica College, n.d.).  An area of skin that the sensory nerve fibers of a particular spinal nerve innervate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. C2 C2 C3 C3 C4 C5 C4 C6 C5 C7 C8 T1 T1 C6 T1 T12 L1 T12 L5 S1 S2 L1 S3 S4 S2 L2 S5 C6 C0 S3 C7 L3 L1 L2 L4 C8 L3 L5 S1 L4 L5 36 (a) (b) (Shier, Butler & Lewis, 200 Spinal & Cranial Reflexes 1. 1.Spinal Spinal reflex: reflex: spinal spinal cord; cord; Cranial Cranial reflex: reflex: brain brain 2. 2.Inborn Inborn or or Learned Learned 3. 3.Rapid Rapid motormotor response response to to aa stimuli stimuli 4. 4.Unconscious Unconscious & & involuntary involuntary (not (not involve involve cerebrum) cerebrum) 5. 5. Instinctive Instinctive behaviour behaviour (CNEC Christian College, 2011). & &  (1) (1) Receptor Receptor (2) (2) Sensory Sensory Five Essential Neuron Neuron Components (3) (3) Integration Integration Center Center (4) (4) Motor Motor Neuron Neuron (CNEC Christian College, 2011). (5) (5) Effector Effector  Spinal cord Interneuron Dorsal 1 Receptor 3 Cell body 2 White matter of sensory Sensory neuron neuron Gray matter 4 Ventral Central Motor neuron canal 5 Effector (muscle or gland) 39 (b) (Shier, Butler & Lewis, 2009). The Reflex Arc  Reflex – rapid, predictable, and involuntary responses to stimuli  Reflex arc – direct route from a sensory neuron, to an interneuron, to an effector (Marieb, 2003).  Reflexes are automatic, subconscious responses to stimuli within or outside the body Simple reflex arc (sensory – motor) Most common reflex arc (sensory – association – motor) Central Sensory or Nervous afferent neuron Motor or System efferent neuron Receptor Effector (muscle or gland) 12 (a) (Shier, Butler & Lewis, 2009). 41 Simple Reflex Arc (Marieb, 2003).  43 (Shier, Butler & Lewis, 2009).  Example is the knee-jerk reflex Simple monosynaptic reflex Helps maintain an upright posture & prevents overstretching Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Axon of sensory Spinal cord neuron Cell body of Effector (quadriceps femoris sensory neuron Cell body of muscle group) motor neuron Receptor associated with dendrites of sensory neuron Axon of motor neuron Patella Direction of impulse Patellar ligament 44 (Shier, Butler & Lewis, 2009).  Prevents or limits tissue damage Cell body of sensory neuron Axon of sensory neuron Direction of impulse Interneuron Spinal cord Effector (flexor Axon of muscle contracts motor neuron Cell body of and withdraws part motor neuron being stimulated) Dendrite of sensory neuron Pain receptor in skin 45 Tack (Shier, Butler & Lewis, 2009).  Contralateralreflex Maintain balance Interneuron + = Stimulation – = Inhibition + – – + Sensory neuron Extensor Extensor relaxes contracts Flexor relaxes Motor Motor neurons neurons Flexor contracts 17 46 (Shier, Butler & Lewis, 2009).  Conditional Reflex 1. Acquired (not inherited) through training or learning. 2. Replace a normal stimulus by a unrelated stimulus to give same response. 3. Initial skills by voluntary; then become unconscious (conditional reflex)(CNEC Christian College,  Bostwick-Taylor, P & Darlington, F. (2008). The Nervous System. Retrieved from http://www.iteachbio.com/Anatomy- Physiology/Anatomy%20and %20PhysiologyTextbook%20Resources/EM %20Chapter%20ppts./EMChapter7c.ppt  CNEC Christian College. (2011). Nervous II. Retrieved from http://www.cneccc.edu.hk/subjects/bio/ppt /hkal/Nervous%20II.ppt  Los Angeles Valley College. (n.d.). The Peripheral Nervous System. Retrieved from http://www.lavc.edu/instructor/watson_k/do cs/Lecture%2014%20-%20Peripheral %20Nervous%20System.ppt  Marieb, E. (2003). The Nervous System Retrieved from http://www.haspi.org/curriculum-library/A-P- Core-Labs/12%20Nervous%20System/ Powerpoint%20Presentations/Nervous %20System%201.ppt  Santa Monica College. (n.d.). PNS Terminology. Retrieved from http://homepage.smc.edu/zuk_patricia/A natomy%201/lecture%20PNS.ppt  Shier, D., Butler, J. & Lewis, R. (2009). Nervous System II. Retrieved from http://nhscience.lonestar.edu/biol/durha m/docs/biol2401/chapt11_holes_lecture. ppt