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CHAPTER 13 PERIPHERAL NERVOUS SYSTEM Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM Organization Copyright © 2010 Pearson Education, Inc. Figure 13.1 Place of the PNS in the structural organization of the nervous system. Central nervous system (CNS) Peripheral nervous system (PNS) Sensory (afferent) division Copyright © 2010 Pearson Education, Inc. Motor (efferent) division Somatic nervous system Autonomic nervous system (ANS) Sympathetic division Parasympathetic division PERIPHERAL NERVOUS SYSTEM Sensory Receptors Copyright © 2010 Pearson Education, Inc. Table 13.1 General Sensory Receptors Classified by Structure and Function (1 of 3) Copyright © 2010 Pearson Education, Inc. Table 13.1 General Sensory Receptors Classified by Structure and Function (2 of 3) Copyright © 2010 Pearson Education, Inc. Table 13.1 General Sensory Receptors Classified by Structure and Function (3 of 3) Copyright © 2010 Pearson Education, Inc. A receptor which responds to changes in temperature is a… 1) 2) 3) 4) 5) mechanoreceptor thermoreceptor photoreceptor chemoreceptor nociceptor Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM Sensory Perception – CNS Integration Copyright © 2010 Pearson Education, Inc. Figure 13.2 Three basic levels of neural integration in sensory systems. Perceptual level (processing in cortical sensory centers) 3 Motor cortex Somatosensory cortex Thalamus Reticular formation Pons 2 Circuit level (processing in Spinal ascending pathways) cord Free nerve endings (pain, cold, warmth) Muscle spindle Receptor level (sensory reception Joint and transmission kinesthetic to CNS) receptor 1 Copyright © 2010 Pearson Education, Inc. Cerebellum Medulla Which level of sensory integration is the level at which the reticular formation and thalamus distribute signals to appropriate cortical regions? 1) Circuit level 2) Receptor level 3) Perceptual level Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM NERVES: Structure Copyright © 2010 Pearson Education, Inc. Figure 13.3b Structure of a nerve. Endoneurium Axon Myelin sheath Perineurium Epineurium Fascicle Blood vessels (b) Copyright © 2010 Pearson Education, Inc. Figure 13.3a Structure of a nerve. Blood vessels Perineurium Fascicle Endoneurium (a) Copyright © 2010 Pearson Education, Inc. Nerve fibers The membrane surrounding a nerve is the... 1) endoneurium 2) epineurium 3) perineurium Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM NERVES: Classification & Location Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM Nerves: Ganglia Copyright © 2010 Pearson Education, Inc. A nerve is… 1) A neuron 2) A group of neuron cell bodies 3) A group of neuron axons wrapped in connective tissue in the peripheral nervous system 4) A group of neuron axons wrapped in connective tissue in the central nervous system 5) All of the above Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM Nerves: Regeneration and Repair Copyright © 2010 Pearson Education, Inc. Figure 13.4 Regeneration of a nerve fiber in a peripheral nerve (1 of 4). Endoneurium Schwann cells Droplets of myelin Fragmented axon Site of nerve damage Copyright © 2010 Pearson Education, Inc. 1 The axon becomes fragmented at the injury site. Figure 13.4 Regeneration of a nerve fiber in a peripheral nerve (2 of 4). Schwann cell Copyright © 2010 Pearson Education, Inc. Macrophage 2 Macrophages clean out the dead axon distal to the injury. Figure 13.4 Regeneration of a nerve fiber in a peripheral nerve (3 of 4). Aligning Schwann cells form regeneration tube Fine axon sprouts or filaments Copyright © 2010 Pearson Education, Inc. 3 Axon sprouts, or filaments, grow through a regeneration tube formed by Schwann cells. Figure 13.4 Regeneration of a nerve fiber in a peripheral nerve (4 of 4). Schwann cell Single enlarging axon filament Copyright © 2010 Pearson Education, Inc. Site of new myelin sheath formation 4 The axon regenerates and a new myelin sheath forms. PERIPHERAL NERVOUS SYSTEM Cranial Nerves Copyright © 2010 Pearson Education, Inc. Figure 13.5a Location and function of cranial nerves. Frontal lobe Temporal lobe Infundibulum Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Accessory nerve (XI) Hypoglossal nerve (XII) (a) Copyright © 2010 Pearson Education, Inc. Filaments of olfactory nerve (I) Olfactory bulb Olfactory tract Optic nerve (II) Optic chiasma Optic tract Oculomotor nerve (III) Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Cerebellum Medulla oblongata Figure 13.5b Location and function of cranial nerves. Cranial nerves I – VI I II III IV V Olfactory Optic Oculomotor Trochlear Trigeminal VI Abducens Cranial nerves VII – XII VII Facial VIII Vestibulocochlear IX X XI XII Glossopharyngeal Vagus Accessory Hypoglossal (b) Copyright © 2010 Pearson Education, Inc. Sensory function Motor function PS* fibers Yes (smell) Yes (vision) No No Yes (general sensation) No No Yes Yes Yes No No Yes No No No Yes No Sensory function Motor function PS* fibers Yes (taste) Yes (hearing and balance) Yes Some Yes No Yes (taste) Yes (taste) No No Yes Yes Yes Yes Yes Yes No No *PS = parasympathetic Cranial nerve I is also known as the… 1) 2) 3) 4) Hypoglossal nerve Olfactory nerve Optic nerve Vagus nerve Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM Spinal Nerves Copyright © 2010 Pearson Education, Inc. Figure 13.6 Spinal nerves. Cervical plexus Brachial plexus Cervical nerves C1 – C8 Cervical enlargement Intercostal nerves Thoracic nerves T1 – T12 Lumbar enlargement Lumbar plexus Sacral plexus Cauda equina Copyright © 2010 Pearson Education, Inc. Lumbar nerves L1 – L5 Sacral nerves S1 – S5 Coccygeal nerve Co1 PERIPHERAL NERVOUS SYSTEM Spinal Nerves: Branches Copyright © 2010 Pearson Education, Inc. Figure 13.7a Formation of spinal nerves and rami distribution. Gray matter White matter Ventral root Dorsal root Dorsal root ganglion Dorsal ramus of spinal nerve Ventral ramus of spinal nerve Spinal nerve Dorsal and ventral rootlets of spinal nerve Rami communicantes Sympathetic trunk ganglion (a) Anterior view showing spinal cord, associated nerves, and vertebrae. The dorsal and ventral roots arise medially as rootlets and join laterally to form the spinal nerve. Copyright © 2010 Pearson Education, Inc. Figure 13.7b Formation of spinal nerves and rami distribution. Dorsal ramus Ventral ramus Spinal nerve Rami communicantes Sympathetic trunk ganglion Intercostal nerve Dorsal root ganglion Dorsal root Ventral root Branches of intercostal nerve • Lateral cutaneous • Anterior cutaneous Sternum (b) Cross section of thorax showing the main roots and branches of a spinal nerve. Copyright © 2010 Pearson Education, Inc. True or false: information only flows toward the spinal cord in a dorsal ramus. 1) True 2) False Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM Spinal Nerves: Plexuses (Plexi?) Copyright © 2010 Pearson Education, Inc. Figure 13.8 The cervical plexus. Ventral rami Segmental branches Hypoglossal nerve (XII) Lesser occipital nerve Greater auricular nerve Transverse cervical nerve Ansa cervicalis Ventral rami: C1 C2 C3 C4 Accessory nerve (XI) Phrenic nerve Supraclavicular nerves Copyright © 2010 Pearson Education, Inc. C5 Figure 13.9a The brachial plexus. Roots (ventral rami): C4 C5 Dorsal scapular Nerve to subclavius Suprascapular Cords C6 Posterior divisions C7 Lateral C8 Posterior T1 Upper Middle Trunks Lower Long thoracic Medial pectoral Medial Lateral pectoral Axillary Musculocutaneous Radial Upper subscapular Lower subscapular Median Ulnar Medial cutaneous nerves of the arm and forearm Thoracodorsal (a) Roots (rami C5 – T1), trunks, divisions, and cords Anterior divisions Copyright © 2010 Pearson Education, Inc. Posterior divisions Trunks Roots Figure 13.9b The brachial plexus. Musculocutaneous nerve Axillary nerve Biceps brachii Coracobrachialis Median nerve Radial nerve branches to triceps Lateral cord Posterior cord Medial cord Radial nerve Ulnar nerve (b) Cadaver photo Copyright © 2010 Pearson Education, Inc. Figure 13.9c The brachial plexus. Axillary nerve Anterior divisions Posterior divisions Humerus Radial nerve Musculocutaneous nerve Ulna Radius Ulnar nerve Median nerve Radial nerve (superficial branch) Dorsal branch of ulnar nerve Superficial branch of ulnar nerve Digital branch of ulnar nerve Muscular branch Median nerve Digital branch (c) The major nerves of the upper limb Copyright © 2010 Pearson Education, Inc. Trunks Roots Figure 13.9d The brachial plexus. Anterior divisions Posterior divisions Major terminal branches (peripheral nerves) Musculocutaneous Median Ulnar Radial Axillary Trunks Cords Roots Divisions Anterior Lateral Medial Posterior Anterior Posterior Posterior Anterior Posterior Trunks Upper C5 C6 Middle C7 C8 Lower (d) Flowchart summarizing relationships within the brachial plexus Copyright © 2010 Pearson Education, Inc. Roots (ventral rami) T1 Figure 13.10 The lumbar plexus. Ventral rami Iliohypogastric Ilioinguinal Genitofemoral Lateral femoral cutaneous Obturator Femoral Lumbosacral trunk Ventral rami: Iliohypogastric L1 Ilioinguinal Femoral Lateral femoral L2 cutaneous Obturator L3 Anterior femoral cutaneous Saphenous L4 L5 (a) Ventral rami and major branches of the lumbar plexus (b) Distribution of the major nerves from the lumbar plexus to the lower limb Copyright © 2010 Pearson Education, Inc. Figure 13.10a The lumbar plexus. Ventral rami Ventral rami: L1 Iliohypogastric L2 Ilioinguinal Genitofemoral Lateral femoral cutaneous L3 L4 Obturator Femoral L5 Lumbosacral trunk (a) Ventral rami and major branches of the lumbar plexus Copyright © 2010 Pearson Education, Inc. Figure 13.10b The lumbar plexus. Iliohypogastric Ilioinguinal Femoral Lateral femoral cutaneous Obturator Anterior femoral cutaneous Saphenous (b) Distribution of the major nerves from the lumbar plexus to the lower limb Copyright © 2010 Pearson Education, Inc. Figure 13.11a The sacral plexus. Ventral rami Ventral rami: L4 Superior gluteal Lumbosacral trunk Inferior gluteal Common fibular Tibial Posterior femoral cutaneous Pudendal Sciatic L5 S1 S2 S3 S4 S5 Co1 (a) Ventral rami and major branches of the sacral plexus Copyright © 2010 Pearson Education, Inc. Figure 13.11b The sacral plexus. Superior gluteal Inferior gluteal Pudendal Sciatic Posterior femoral cutaneous Common fibular Tibial Sural (cut) Deep fibular Superficial fibular Plantar branches (b) Distribution of the major nerves from the sacral plexus to the lower limb Copyright © 2010 Pearson Education, Inc. Figure 13.11c The sacral plexus. Gluteus maximus (medial portion removed) Piriformis Inferior gluteal nerve Pudendal nerve Greater trochanter of femur Common fibular nerve Tibial nerve Posterior femoral cutaneous nerve Sciatic nerve Ischial tuberosity (c) Cadaver photo Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM Spinal Nerves: Dermatomes Copyright © 2010 Pearson Education, Inc. Figure 13.12 Map of dermatomes. C2 C3 C4 C5 C6 C7 C8 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 C2 C3 C4 C5 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T2 C5 C6 C6 C7 L1 C8 L2 T12 S2 S3 T2 C5 C6 L1 C8 L2 S1 L4 S2 S3 S4 S5 C6 C7 C6 C7 C8 C8 L2 S2 S1 L1 L3 L5 L4 T11 T12 L1 L3 L5 C7 C6 S1 S2 L3 C5 L2 L5 L4 L3 L5 L5 L4 S1 (a) Anterior view Copyright © 2010 Pearson Education, Inc. S1 (b) Posterior view L4 L5 L4 L5 S1 True or false: Pain felt on the surface of a body region is always related to skin problems. 1) True 2) False Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM MOTOR ENDINGS Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM MOTOR INTEGRATION Copyright © 2010 Pearson Education, Inc. Figure 13.13 Hierarchy of motor control. Precommand level • Cerebellum • Basal nuclei Precommand Level (highest) • Cerebellum and basal nuclei • Programs and instructions (modified by feedback) Internal feedback Feedback Projection Level (middle) • Motor cortex (pyramidal system) and brain stem nuclei (vestibular, red, reticular formation, etc.) • Convey instructions to spinal cord motor neurons and send a copy of that information to higher levels Projection level • Primary motor cortex • Brain stem nuclei Segmental level • Spinal cord (b) Structures involved Segmental Level (lowest) • Spinal cord • Contains central pattern generators (CPGs) Sensory input Reflex activity Motor output (a) Levels of motor control and their interactions Copyright © 2010 Pearson Education, Inc. PERIPHERAL NERVOUS SYSTEM REFLEX ARC Copyright © 2010 Pearson Education, Inc. Figure 13.14 The five basic components of all reflex arcs. Stimulus Skin 1 Receptor Interneuron 2 Sensory neuron 3 Integration center 4 Motor neuron 5 Effector Spinal cord (in cross section) Copyright © 2010 Pearson Education, Inc. Figure 13.15 Anatomy of the muscle spindle and Golgi tendon organ. Secondary sensory endings (type II fiber) Primary sensory endings (type Ia fiber) Muscle spindle Connective tissue capsule Efferent (motor) fiber to muscle spindle Efferent (motor) fiber to extrafusal muscle fibers Extrafusal muscle fiber Intrafusal muscle fibers Sensory fiber Golgi tendon organ Copyright © 2010 Pearson Education, Inc. Tendon Figure 13.16 Operation of the muscle spindle. Muscle spindle Intrafusal muscle fiber Primary sensory (la) nerve fiber Extrafusal muscle fiber Time Time Time (a) Unstretched muscle. Action potentials (APs) are generated at a constant rate in the associated sensory (la) fiber. (b) Stretched muscle. Stretching activates the muscle spindle, increasing the rate of APs. (c) Only motor (d) - Coactivation. neurons activated. Both extrafusal and Only the extrafusal intrafusal muscle muscle fibers contract. fibers contract. The muscle spindle Muscle spindle becomes slack and no tension is mainAPs are fired. It is tained and it can unable to signal further still signal changes length changes. in length. Copyright © 2010 Pearson Education, Inc. Time Figure 13.17 The Stretch Reflex (1 of 2) The events by which muscle stretch is damped 1 When muscle spindles are activated 2 The sensory neurons synapse directly with alpha motor neurons (red), which excite extrafusal fibers of the stretched muscle. Afferent fibers also by stretch, the associated sensory neurons (blue) transmit afferent impulses synapse with interneurons (green) that inhibit motor neurons (purple) controlling antagonistic muscles. at higher frequency to the spinal cord. Sensory neuron Cell body of sensory neuron Initial stimulus (muscle stretch) Muscle spindle Antagonist muscle Spinal cord 3a Efferent impulses of alpha motor neurons 3b Efferent impulses of alpha motor cause the stretched muscle to contract, which resists or reverses the stretch. neurons to antagonist muscles are reduced (reciprocal inhibition). Copyright © 2010 Pearson Education, Inc. Figure 13.17 The Stretch Reflex (2 of 2) The patellar (knee-jerk) reflex – a specific example of a stretch reflex 2 Quadriceps (extensors) 1 3a 3b 3b Patella Muscle spindle Spinal cord (L2 – L4) Hamstrings (flexors) Patellar ligament 1 Tapping the patellar ligament excites muscle spindles in the quadriceps muscle. 2 Afferent impulses (blue) travel to the spinal cord, where synapses occur with motor neurons and interneurons. 3a The motor neurons (red) send + Excitatory synapse – Inhibitory synapse Copyright © 2010 Pearson Education, Inc. activating impulses to the quadriceps causing it to contract, extending the knee. 3b The interneurons (green) make inhibitory synapses with ventral horn neurons (purple) that prevent the antagonist muscles (hamstrings) from resisting the contraction of the quadriceps. Figure 13.19 The crossed-extensor reflex. + Excitatory synapse – Inhibitory synapse Interneurons Efferent fibers Afferent fiber Efferent fibers Extensor inhibited Flexor stimulated Site of stimulus: a noxious stimulus causes a flexor reflex on the same side, withdrawing that limb. Copyright © 2010 Pearson Education, Inc. Arm movements Flexor inhibited Extensor stimulated Site of reciprocal activation: At the same time, the extensor muscles on the opposite side are activated. True or false: The flexor-crossed extensor reflex involves multiple integration neurons. 1) True 2) False Copyright © 2010 Pearson Education, Inc.