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Nervous System

by: Kelsey McKenna

Nervous System Bio 202

Kelsey McKenna
C of C
GPA 3.04

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Dr. Pringle's lecture notes Nervous System 1-3
Human Anatomy
Dr. Pringle
Class Notes
Human Anatomy
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This 7 page Class Notes was uploaded by Kelsey McKenna on Saturday January 2, 2016. The Class Notes belongs to Bio 202 at College of Charleston taught by Dr. Pringle in Winter 2016. Since its upload, it has received 31 views. For similar materials see Human Anatomy in Biology at College of Charleston.


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Date Created: 01/02/16
1 NERVOUS SYSTEM Functions: • Orientation of the body to INTERNAL and EXTERNAL environments (sensory); o Internal: visceral o External: somatic o Sensory fibers are called afferent o Visceral afferent: telling the brain what’s going in on the inside of the body • Coordination and control of body activities o Motor are also known as efferent § Efferent taking information away from the brain • Assimilation of experiences requisite to memory, learning, & intelligence & • Programming of instinctual behavior. • Sensory –monitors changes (stimuli) inside and outside the body (Energy forms) o Sound waves, light, taste • Integrative –interprets the changes (“integration”) • Motor–controls responses by activating muscles and glands There are two Anatomic divisions: • Central Nervous System (C.N.S.) o Brain: “higher functions,” learning, memory, intelligence, reasoning, personality integrates and coordinates sensory data and motor commands. o Spinal Cord o Completely inside the dorsal body cavity protecting it • Peripheral Nervous System (P.N.S.) o nervous tissue outside the C.N.S. o conveys information to and from the C.N.S. § receptors: § neurons: o 99% are in the brain o spread throughout the body § nerves: are in the P.N.S o Cranial nerves: attached to the brain o Spinal nerves: attached to spinal cord § ganglia: in the P.N.S collection of neuron cell bodies § plexus: when the spinal nerves are hooked together so it creates a network, the ventral rami of the spinal nerves Stimuli: forms of ENERGY: Everything we perceive is a form of energy: light, sound, chemical, mechanical, temperature. TRANSDUCTION : changing energy from one form to another. RECEPTORS: transduce energy. They change these forms of energy to a type the body 2 can use (transduction) “Action potential” = “nerve impulse” • “Law of Specific Nerve Energy” Each receptor responds to a certain type of energy. • “Sensation” takes place at the receptor. • “Perception” takes place in the brain. • Classified: o Exteroceptors: sense external environment, somatic § General senses are from the skin: pain, touch, tempt, pressure § will go to the postcentral gyrus § “Special senses” (more complicated) sight, smell, taste § “Proprioceptors” sense position of muscle and joints, why you can close your eyes and touch your nose o Interoceptors: sense internal environment, visceral § Blood glucose, etc NEURONS: pg 5, single cells sensory or motor in P.N.S • Can be either sensory or motor o NOT both NERVES: cable-like collections of neurons (axons) in P.N.S. • Classified: o “Mixed” Contain motor and sensory neurons. All spinal nerves are mixed. o “Sensory only” three cranial nerves are sensory only § I, II, VIII o “Motor only” nope don't worry about it GANGLIA: collections of neuron cell bodies in the P.N.S. • Sensory: visceral and somatic: dorsal root ganglia • Motor: somatic None visceral (A.N.S.) a) parasympathetic “terminal ganglia” b) sympathetic: sympathetic chain ganglia= paravertebral g. collateral ganglia PLEXUS: network of interwoven nerves ventral ramus of spinal nerves in P.N.S. • No thorastic plexus. Nerves, ganglia, plexus: • Are all in PNS NUCLEUS: collection of neuron cell bodies in the C.N.S. TRACT : bundle of axons in the C.N.S. with a common origin, destination and function. • Same thing as a nerve COLUMN : several tracts bundled together in the spinal cord. 3 GRAY MATTER: dendrites, cell bodies, unmyelinated axons: • In the brain: “cortex” and “nucleus • In the spinal cord: “H” or “butterfly” WHITE MATTER : myelinated axons • In the brain: mostly on the inside NEUROGLIA: supporting cells. They do NOT conduct “action potentials.” They age SYNAPSE How the neurons communicate. Neurons can have 20,000 synapses. Chemical synapse: use neurotransmitter (N.T.) • axon terminal of presynaptic neuron (synaptic knob) o contains vesicles with N.T. • synaptic cleft (gap) • dendrite or cell body of post synaptic neuron o contains receptors for N.T., channels & enzymes An “action potential” (nerve impulse) reaching the synaptic knob causes: • exocytosis of the N.T. The N.T. diffuses across the synaptic cleft, binds to the receptor, which causes the channels to open or close. • This sets up changes in the 2 (postsynaptic) neuron. Two of the neurotransmitters: • Ach (acetylcholine) • N.E. (norepinephrine) • Synapse= neuron to neuron • Neuromuscular junction= neuron to muscle cell • Electrical synapse (junction) • Gap junction (intercalated disc) 4 Neurons I. Introduction: • The basic structural and functional unit of the nervous system. • Neurons are able to store memory, think, communicate with other neurons and regulate organs and glands because they: § are excitable § conduct impulses § release specific chemical regulators (neurotransmitters) • Neurons are single cells. • Neurons are very sensitive to decreased oxygen: 5 minutes without oxygen • Neurons cannot divide mitotically: § Cell body dies it cannot fix it self § The number is fixed at birth. § The number of connections (synapses) can change: o When you learn something new synapeses are formed II. Anatomy of Neurons • Cell body (aka perikaryon and soma) § nucleus with nucleolus: brain of the neuron § organells § micotubules § Nissl bodies (chromatophilic substances–rough E.R.) § neurofibrils • Clusters of cell bodies in the CNS are called • Clusters of cell bodies in the PNS are called ganglia B. Dendrites: taking information toward the cell body C. Axon: taking info away from the cell body 5 • Telodendria: where the axon splits into different branches, Not myelinated • Synaptic terminal (synaptic knob): the final part of the telodendria, contain neurotransmitters • Myelin § lipid (white): o insulates (“saltatory conduction”): when jumps between gaps o neurolemmal sheath § Nodes of Ranvier: gaps between the myelin • In PNS myelin is made by Schwann Cells • In CNS myelin is made by oligodendrocytes III. Classification of Neurons: • STRUCTURAL: based on the number of processes that come off the cell body. § Bipolar: two processes coming off the body o In eye and ear § Unipolar: one process attached to cell body § Multipolar: multiple processes coming off of the cell body § Anaxonic: only in CNS look like starfish • FUNCTIONAL: based on the direction of the nerve impulse (action potential). § Sensory neuron = Afferent neuron (toward the CNS, taking info to the brain) o Source of stimulus: • Somatic: coming from the outside world o Pressure on skin • Visceral: info from the inside of the body o Stretch receptors in the stomach, blood vessels, etc. • All sensory in PNS are unipolar § Motor neuron = Efferent neuron (away from the CNS) o Type of TARGET Organ: • Somatic: receptor in skin • Visceral: receptor inside the body § Interneuron: o In the CNS only • LOCATION: § Afferent- Somatic and Visceral st o 1 onder: goes from receptor to the dorsal horn (PNS) o 2 order: dorsal horn to the thalamus o 3 order: thalamus to the postcentral gyrus 6 § Efferent: o Upper motor neuron: completely within the CNS, turn on the lower motor neurons (tell them what to do) o Lower motor neuron: leave the CNS and go to the target o Can be somatic or visceral § Somatic efferent: § Visceral efferent: o Preganglionic neuron: before the ganglion, turns on the postganglionic o Postganglionic neuron: after the ganglion, goes to the target 3. Connections in and to the brain a. Association fibers: ex. Arcuate fibers b. Commissural fibers: ex. Corpus Callosum, Anterior commissure c. Projection fibers: ex. Internal Capsule (in brain) forms tracts and columns in spinal cord. 7 P.N.S. • Conveys impulses to and from the brain and spinal cord. Receptors: Nerves: A) Cranial B) Spinal Dermatome: area supplied by a spinal nerve Ganglia: Nerve plexuses: I. Spinal nerves: • Mixed–contain afferent and efferent neurons. • 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. • (–endoneurium, fasciculus–perineurium–epineurium) • Intervertebral foramen: has the spinal nerves pass through • ROOTS: attach nerves to spinal cord. o Dorsal root: contains only sensory neurons o Ventral root: contains only motor neurons o Remember: DAVE-dorsal afferent ventral efferent • SPINAL NERVE: where the two roots come together then the branches come off of the spinal nerve, like the trunk of a tree • BRANCHES: (Ramus) o Meningeal branch: o Posterior (dorsal) ramus: o Anterior (ventral) ramus: o White rami communicates: o Gray rami communicates: o Sympathetic trunk (“chain”) ganglion: II. Nerve Plexuses: “Network of interlaced nerves.” • Formed by anterior (ventral) rami. • CERVICAL PLEXUS: (C1-C4) o Phrenic nerve • BRACHIAL PLEXUS: (C5-T1) o Radial & Ulnar nerve o ( roots–trunks–divisions–cords–branches) Randy Travis drinks cold beer. • LUMBAR PLEXUS: (L1-L4) ex. Femoral nerve • SACRAL PLEXUS: (L4-S4) ex. Sciatic nerve • Reflex Arc: receptor–sensory neuron–“center” in CNS (interneuron)-- motor neuron–effector. o A) Visceral (autonomic) reflex: cardiac muscle, smooth muscle and § glands o B) Somatic reflex: skeletal muscles


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