Introduction to the Nervous System PDF

Introduc)on to the Nervous System Edie Sperling, DPT, Western University of Health Sciences  Basic Anatomy: Two Ways to Consider the Nervous System How it’s organized physically in the body What it does in the body 4 Struct...

Introduc)on to the Nervous System Edie Sperling, DPT, Western University of Health Sciences  Basic Anatomy: Two Ways to Consider the Nervous System How it’s organized physically in the body What it does in the body 4 Structural Anatomy: Neuron Structure  Structural Anatomy: Cellular Structure Neurons Cell body with nucleus Dendrites (carries incoming/aGerent informa)on) Axons (carries outgoing/eGerent informa)on) Communicate across synapses with other neurons Neuroglia (glial cells) Support (scaGolding, insula)on, nourishment) for neurons More abundant than neurons 6 Structural Anatomy: Cellular Structure 7 Structural Anatomy: Central Nervous System (CNS) Structurally: Primary Func)ons: Coordinate incoming/ outgoing neural signals Execute higher mental func)ons 9  Cell Axons Structural Anatomy: bodies Gray & White Matter Gray MaSer Brain & spinal cord composed of what we call gray maSer & white maSer: White ma;er – myelinated axons Tract (axon bundles) systems Relays informa)on Gray ma;er - neuron cell bodies, dendrites, unmyelinated axons, neuroglia, & blood Deep to white maSer in spinal cord, BuSerUy/H shape Mostly external to white maSer in brain 10 Structural Anatomy: CNS Spinal cord gray maSer is organized into dorsal (back/posterior) & ventral (front/anterior) horns on each side Lateral horns exist, only at T1-L2 Dorsal = sensory informa)on (incoming/aGerent) Ventral = motor informa)on (outgoing/eGerent) 11 12  Myelin in the CNS Myelin in the CNS is made by oligodendrocytes. This is what causes axons to be white = white maSer Myelin increases the speed of transmission as the nerve signal (ac)on poten)al) “hops” between myelin wrappings on the Nodes of Ranvier. 13 Multiple Sclerosis MS is a pathological demyelina)on process in the CNS. As the myelin is damaged, nerve signals consequently move more slowly, which slows movement. 14 Structural Anatomy: Peripheral Nervous System (PNS)  Structural Anatomy: PNS Peripheral nerves emerge from brain & spinal cord Cranial nerves (from brain) 12 pairs Spinal nerves (from spinal cord) 31 pairs Collec)on of PNS cell bodies is a ganglion Peripheral nerves are bundles of axons & suppor)ng neuroglia enclosed in connec)ve )ssue (examples: median n., radial n., etc – all the ones with names) 16  Structural Anatomy: Spinal cord gray maSer PNS horns give rise to: Dorsal & Ventral Rootlets Dorsal which become: rootlets Dorsal & Ventral Roots which join to form: Spinal nerves Dorsal roots have the Dorsal Root Ganglion (DRG), cell bodies of the Ventral sensory nerves rootlets 17  Structural Anatomy: PNS Dorsal Spinal nerves split into rootlets Dorsal & Ventral Rami (plural) Rootlets, roots, spinal nerves, & rami all made up of axons/nerve gber bundles Ventral rootlets 18  Structural Anatomy: PNS Dorsal rootlets and root = sensory only Ventral rootlets and root = motor only Join to form the spinal nerve = mixed sensory + motor Split again into dorsal and ventral rami = stay mixed 19 Structural Anatomy: PNS Dorsal Rami: Supply vertebral joints, deep back muscles & skin (green area) 20  Structural Anatomy: PNS Ventral Rami: Supply gbers to rest of body, including limbs Many merge to form plexuses (cervical, brachial, lumbar, & sacral) 21 Structural Anatomy: PNS A lot of Lmes, we give the ventral rami another name 22  Myelin in the PNS Myelin in the PNS is made by Schwann cells, but it serves the same purpose of increasing speed of transmission. The nerve signal travels the same way – hopping between nodes of Ranvier. Note the diGerences between an oligodendrocyte and a Schwann cell. 23 Structural Anatomy: Naming Structures  Roots And Rami Of Spinal Nerves Dorsal Horn Lateral Horn Ventral Horn 25 Diagram courtesy of Dr. Brian Kraatz  Roots And Rami Of Spinal Nerves Dorsal Horn Dorsal Root Lateral Horn Ventral Horn Ventral Root 26 Diagram courtesy of Dr. Brian Kraatz  Roots And Rami Of Spinal Nerves Dorsal Root Dorsal Root Ganglion Dorsal Horn Lateral Horn Ventral Horn Ventral Root 27 Diagram courtesy of Dr. Brian Kraatz  Roots And Rami Of Spinal Nerves Dorsal Root Dorsal Ramus Ganglion Dorsal Horn Dorsal Root Spinal Nerve Ventral Ramus Lateral Horn Ventral Horn Ventral Root 28 Diagram courtesy of Dr. Brian Kraatz Structural Anatomy: Levels The Spine 30 Structural Anatomy: Levels Spinal cord runs within vertebral canal In fetuses & newborns, the spinal cord runs the whole length of the vertebral canal. 31  Structural Anatomy: Levels CNS stops growing before rest of body Vertebral column ends up being longer than spinal cord Adult spinal cord ends ~L1/L2 32  Structural Anatomy: Levels Spinal nerve roots are progressively displaced Cauda equina (“horse’s tail”) are the roots that emerge and con)nue down aper the spinal cord ends 33 Spinal Cord Anatomy 34 Functional Anatomy Func)onal Anatomy 36 Functional Anatomy: Somatic = Voluntary  Functional Anatomy: Somatic Voluntary Part of both CNS & PNS Provides general sensory & motor innerva)on to body but NOT viscera (organs), smooth muscle, glands 38  Functional Anatomy: Somatic Motor (eRerent) Sbers Go to skeletal muscles to cause contrac)on Sensory (aRerent) Sbers Transmit pain, temperature, light touch, pressure, propriocep)ve 39 Func)onal Anatomy: Soma)c Motor Innerva)on Upper motor neuron (UMN) Cell body located in brain Synapses on an interneuron or Lower motor neuron (LMN) UMN Lower motor neuron (LMN) Cell body located in brainstem or spinal cord LMN Axon passes out of CNS Directly innervates muscle 40 41 Functional Anatomy: Sensory Innervation to Skin Sensory innerva)on is just nerves that send informa)on INTO the spinal cord and brain instead of out (like motor informa)on) Informa)on coming in is called ARerent Receptors in the skin (and organs, muscles, blood vessels, eye, etc.) pick up signals from the environment and transmit those signals to our CNS, where some)mes ac)on is taken on them (i.e., a puG of air blows into our eye, so we blink). 42 Roots And Rami Of Spinal Nerves Dorsal Root Ganglion Dorsal Ramus Dorsal Root Dorsal Horn Spinal Ventral Ramus Nerve Lateral Horn Ventral Horn Ventral Root 43 Diagram courtesy of Dr. Brian Kraatz  Roots And Rami Of Spinal Nerves SomaLc aRerent/ Dorsal Root Ganglion sensory pathways Dorsal Root Dorsal Ramus Dorsal Horn Spinal Ventral Ramus Nerve Lateral Horn Ventral Horn Ventral Root 44 Diagram courtesy of Dr. Brian Kraatz  Roots And Rami Of Spinal Nerves Dorsal Root Ganglion Dorsal Ramus Dorsal Root Dorsal Horn Spinal Ventral Ramus Nerve Lateral Horn SomaLc eRerent Ventral Horn (motor) pathways Ventral Root 45 Diagram courtesy of Dr. Brian Kraatz  Roots And Rami Of Spinal Nerves SomaLc aRerent pathways Dorsal Root Ganglion Dorsal Ramus Dorsal Root Dorsal Horn Spinal Ventral Ramus Nerve Lateral Horn Ventral Horn Ventral Root SomaLc eRerent pathways Diagram courtesy of Dr. Brian Kraatz Functional Anatomy: Autonomic = Involuntary 47  Central Nervous System (Brain and Spinal Cord) ERerent ARerent Peripheral Nervous System (everything else) Visceral SomaLc (organ stuR) (muscle stuR) Visceral ARerent Visceral ERerent SomaLc ARerent SomaLc ERerent (sensory) (motor) (sensory) (motor) Autonomic ParasympatheLc SympatheLc (chill mode) (freak-out mode) Autonomic Nervous System  Autonomic Nervous System SympatheLc ParasympatheLc SympatheLc: ParasympatheLc: Fight or Uight Relax and digest Gets body ready to Can can be alert but run or gght not stressed Increased nervous Decreased nervous system tone to be system tone to relax primed for ac)on (Extreme reac)on: freeze)  Autonomic Nervous System SympatheLc: ParasympatheLc: SympatheLc ParasympatheLc Smooth muscle sphincters contract to GI mo)lity goes up & sphincters relax prevent diges)on, urina)on, defeca)on Glandular produc)on (diges)ve, mucus, Sweat etc) Increased heart rate Decreased heart rate Peripheral blood vessels dilate-visceral Visceral vessels dilate vessels constrict Broncho-relaxa)on Bronchodila)on Nasal concha swell, mucosal membranes Oral & nasal passages dry, clear, & secrete open Lacrimal glands more produc)ve Lacrimal glands less produc)ve Pupils constrict Pupils dilate Sexual arousal Orgasm SympatheLcs SympatheLc nerves are derived from sympathe)c cell bodies which live in the spinal cord between T1-L2 Sympathe)c nerves must enter and travel up or down the sympatheLc chain (a gber bundle of nerve )ssue lateral to the vertebral column on either side) to reach organs, glands, blood vessels, etc. ParasympatheLcs PARASYMPATHE TICS Parasympathe)c nerves only derive from cranial nerves 3, 7, 9, 10 and from the sacral spinal cord S2-S4. That’s how this system got the name “craniosacral”  PARASYMPATHETICS CNIII Oculomotor goes to ciliary muscles in the eye CNVII Facial goes to submandibular and sublingual glands (salivatory), and lacrimal and nasal glands/mucosa CNIX Glossopharyngeal goes to the paro)d gland (saliva) CN X Vagus goes to parts of the mouth and pharynx, larynx, thorax, abdomen, and gonads (tes)cles and ovaries) **Note there are two of each cranial nerve  Visceral ARerents (sensory input from organs)  Visceral ARerent Fibers AGerents originate in visceral organs and pass signals back to CNS They have two main func)ons General sensory: pressure, pH, temperature Pain Dermatomes  What is a Dermatome? **One nerve = thousands of nerve fibers** A spinal level refers to a specific region of the spinal cord (like C8 or T9), and each spinal level receives cutaneous fibers from an area of skin. A dermatome is an area of the skin in which all cutaneous fibers track back to the same spinal level (i.e., they all go into the spinal cord at, say, at C8, which would define C8 dermatome).