Peripheral Nervous System PDF

©  Peripheral Nervous System Dr. Sean McWatt, PhD [email protected] Nervous System Central nervous system CNS Nervous System Brain Spinal Cord Nerves...

©  Peripheral Nervous System Dr. Sean McWatt, PhD [email protected] Nervous System Central nervous system CNS Nervous System Brain Spinal Cord Nerves Peripheral nervous system Functions PNS Controls and integrates bodily activity Reacts to constant changes in external and internal environments This lecture will give a brief introduction to the brain and spinal cord before focusing on the spinal nerves, which make up the majority of peripheral nerves that extend into the body. We will also take a brief look at the cranial nerves, which extend directly out of the brain, making up the remainder of the peripheral nervous system Anterior view Drake, Gray’s Anatomy for Students, 2nd Ed., Copyright © 2009 by Churchill Livingstone Functional Overview Central nervous system Peripheral nervous system Sensory Motor Autonomic Somatic Somatic Autonomic Viscera and enteroceptors Body Skeletal muscle Organs and glands Voluntary control Involuntary control This lecture primarily focuses on the somatic nervous system, but we will introduce some basic Parasympathetic Sympathetic Feed and breed Fight, flight, or fright structures of the autonomic Rest and digest nervous system as well Adapted from Dr. Danielle Brewer-Deluce Learning Outcomes By the end of this lesson, you will be able to… Describe the basic anatomy of the brain and spinal cord Describe the anatomy of a spinal nerve and explain the distribution of sensory and motor neurons within it Explain the concept of a plexus and identify key areas of the spinal cord where the brachial plexus, sympathetic trunk, and lumbosacral plexus emerge Differentiate between the sympathetic and parasympathetic nervous systems and the general origins of their nerves Brain and Spinal Cord  Brain The cerebrum is split into lobes and areas that control all of our higher functioning and a large amount of integration and processing of signals from the periphery Cerebrum Temporal lobe Auditory, smell, and memory processing Brainstem Midbrain Pons Medulla oblongata Cerebellum Basal functions and pathways Many functions! Sagittal view (left) Sagittal view (right) Gilroy, Anatomy: An Essential Textbook, Copyright © 2013 by Thieme Spinal Cord Part of the central nervous system (CNS) Cervical Cervical enlargement for brachial plexus (C5-T1) Thoracic Lumbar Lumbar enlargement for lumbosacral plexus (L1-S4) LII Spinal cord ends at around LI-LII vertebral level The spinal cord terminates at Sacral the level of LII because of Coccygeal differential growth – our spinal cords stop growing early, but our bodies continue! Sagittal views (left) Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins  Spinal Cord The cauda equina is made up of the spinal nerves that go to the lower Conus medularis lumbar, sacral, and coccygeal target areas that leave the spinal cord at its termination (around LII vertebral level) Cauda equina “Horse’s tail” Spinal cord terminates at around LI-LII Filum terminale Extension of pia mater http://tiny.cc/3h07bz Posterior views Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins Spinal Cord Spinal nerves Central canal CSF Gray matter Posterior horn “H” Sensory input Lateral horn Autonomic output Anterior horn Motor output The cell bodies of peripheral motor neurons exist in the anterior and lateral horns of the gray Spinal matter within the spinal cord Cord White matter The cell bodies of peripheral sensory neurons exist in the dorsal root ganglion Anterolateral view (transverse) Drake, Gray’s Anatomy for Students, 2nd Ed., Copyright © 2009 by Churchill Livingstone  Cerebrospinal fluid Spinal Cord Meninges Within subarachnoid space Pia mater ‘Tender/soft mother’ Denticulate ligaments Cerebrospinal fluid (CSF) Shark Within subarachnoid space tooth Superolateral view Arachnoid mater ‘Spider-like mother’ Dura mater ‘Tough/hard mother’ Meninges are tissue layers that wrap around the Posterior view http://tiny.cc/ad07bz brain and spinal cord to anchor and protect them Anterolateral view Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins Spinal Cord Meninges: Spaces Subarachnoid Subdural space space Potential space Lumbar puncture Targeting subarachnoid space for CSF sample or LII fast-acting spinal anesthesia Epidural spaces Epidural Targeting epidural Superolateral view space for slow diffusion SII of anesthetic The spinous processes of lumbar vertebrae are more horizontally oriented, making it easier to pass a needle between them and perform clinical procedures Sagittal view Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins Spinal Nerves Spinal Cord Spinal nerve Spinal nerves extend into the periphery from between vertebrae at each level of the spinal cord Skin Muscle Dermatome Myotome The spinal nerves extend from the spinal cord to distribute motor signals throughout the body and return sensory American Spinal Injury Association signals to the central nervous system Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins  Spinal Nerves Motor and sensory to the muscles of the intrinsic back and skin of the back Posterior/dorsal Posterior/dorsal Root rootlets With dorsal root ganglion; Sensory Sensory Posterior/dorsal Spinal nerve ramus Motor and sensory Intervertebral foramen Anterior/ventral root Motor Anterior/ventral ramus Spinal nerves are like the trunks Anterior/ventral rootlets Motor and sensory to all of trees, with roots and rootlets Motor other muscles and skin anchoring them to the spinal cord, and branch-like rami extending into the periphery http://tiny.cc/2097bz Drake, Gray’s Anatomy for Students, 2nd Ed., Copyright © 2009 by Churchill Livingstone Anterior view Spinal Nerves Motor unit One neuron that innervates multiple muscle fibres Motor (efferent) vs. sensory (afferent) Posterior/dorsal horn, rootlets, and roots Proximal to the spinal nerve = sensory Posterior (i.e., rootlets and roots), anterior ramus structures carry motor signals and posterior structures carry sensory signals Anterior/ventral horn, rootlets, and roots = motor In the spinal nerve and distal to it Anterior (i.e., anterior and posterior rami), ramus all structures carry both motor and sensory signals All rami (anterior AND posterior) = motor AND sensory Anterolateral view Drake, Gray’s Anatomy for Students, 2nd Ed., Copyright © 2009 by Churchill Livingstone Plexuses and Other Features Spinal Cord Part of the central nervous system (CNS) Cervical Cervical enlargement for brachial plexus (C5-T1) Thoracic Lumbar Lumbar enlargement for lumbosacral plexus (L1-S4) LII Spinal cord ends at around LI-LII vertebral level Sacral The cervical and lumbar Coccygeal enlargements indicate levels at which the limbs form, requiring many nerves Sagittal views (left) Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins  Plexuses and Peripheral Nerves The same thing happens in Dermatomes Nerve map the lower limb with the Area of skin innervated Area of skin lumbar and sacral plexuses by fibers from a single C3 innervated by a single spinal nerve C4 peripheral nerve T2 C5 T3 T4 C6 T2 T5 C5 T1 C6 C7 C8 Radial n. Spinal nerves from different C5-T1 levels combine and separate This mixing of spinal within plexuses to create nerves creates complex peripheral nerves that carry peripheral nerve map with fibers from multiple spinal levels nerves that contribute to multiple dermatomes Anterior view Agur and Dalley, Grant’s Atlas of Anatomy, 13th Ed. Copyright © 2013 by Lippincott Williams and Wilkins  Sympathetic Trunk Central canal CSF Cervical spinal cord Gray Posterior horn matter Sensory input “H” Lateral horn Autonomic output Anterior horn Motor output White matter Sympathetic neurons arise from the lateral horn of the spinal cord at levels Thoracic spinal cord T1 – L2 and join the sympathetic trunk Transverse view Drake, Gray’s Anatomy for Students, 2nd Ed., Copyright © 2009 by Churchill Livingstone Anterolateral view Sympathetic Trunk Neurons ascend or descend the sympathetic trunk to carry sympathetic (fight, flight, or fright) signals throughout the periphery Those neurons emerge from the spinal cord at every level between T1 and L2. So, the sympathetic trunk is attached to the spinal nerves of T1-L2, even though it extends above and below that Autonomic Sympathetic Nervous System Parasympathetic Sympathetic system arises from T1-L2 Cranial nerves T1 CN III (oculomotor n.) Lung CN VII (facial n.) CN IX (glossopharyngeal n.) CN X (vagus n.) Parasympathetic system is L2 craniosacral S2 Sympathetic S4 Gilroy, Anatomy: An Essential Textbook, trunk/chain Copyright © 2013 by Thieme Cranial Nerves Extra Info: Cranial Nerves Twelve pairs of nerves (bilateral) 1. Olfactory n. (CN I) 2. Optic n. (CN II) General somatic: 3. Oculomotor n. (CN III) Skeletal muscle, skin 4. Trochlear n. (CN IV) 5. Trigeminal n. (CN V) General visceral: 1. Ophthalmic n. (CN V1) Blood vessels, glands, 2. Maxillary n. (CN V2) intraocular muscles 3. Mandibular n. (CN V3) 6. Abducent n. (CN VI) 7. Facial n. (CN VII) Special somatic: 8. Vestibulocochlear n. (CN VIII) Vision, hearing 9. Glossopharyngeal n. (CN IX) 10. Vagus n. (CN X) Special visceral: 11. Spinal accessory n. (CN XI) Taste, smell 12. Hypoglossal n. (CN XII) Don’t memorize all of these The cranial nerves are complex! We will look at them in more detail in the upper-year course Gilroy, Anatomy: An Essential (KIN 3222 | HS 3300) Textbook, Copyright © 2013 by Thieme Preview: PSNS Summary Oculomotor n. (CN III) Pupillary constriction Facial n. (CN VII) Production of tears (lacrimal gland) Production of saliva (sublingual and submandibular glands) Production of mucus (nasal cavity and palate) Glossopharyngeal n. (CN IX) Production of saliva (parotid gland) Vagus n. (CN X) Bronchi and lungs Heart Esophagus, foregut, and midgut We will discuss these four cranial nerves in our next lecture on the autonomic nervous system Gilroy, Anatomy: An Essential Textbook, Copyright © 2013 by Thieme Learning Outcomes By now, you should better understand how to… Describe the basic anatomy of the brain and spinal cord Describe the anatomy of a spinal nerve and explain the distribution of sensory and motor neurons within it Explain the concept of a plexus and identify key areas of the spinal cord where the brachial plexus, sympathetic trunk, and lumbosacral plexus emerge Differentiate between the sympathetic and parasympathetic nervous systems and the general origins of their nerves  © [email protected]