Chapter 13 nroc64.docx

6 Pages
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Department
Neuroscience
Course Code
NROC64H3
Professor
Janelle Leboutillier

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Description
Chapter 13 SOMATIC MOTOR SYSTEMSmooth Muscle lines the digestive tract arteries and related structures and is innervated by nerve fibers from the autonomic nervous system plays a role in peristalsis and the control of blood pressure and blood flowStriated MuscleCardiac Muscle heart muscle contracts rhythmically even in the absence of any innervations innervations from ANS functions to accelerate or slow down heart rateSkeletal Muscle functions to move bones around joints move eyes control respiration facial expression and produce speechEach skeletal muscle enclosed in a connective tissue sheath that at the ends of the muscle forms the tendonsWithin each muscle are hundreds of muscle fibersthe cells of skeletal muscleeach muscle fiber is innervated by a single axon branch from the CNSSkeletal muscle is derived embryologically from 33 paired somites these muscles and the parts of the nervous system that control them are collectively called the somatic motor systemunder voluntary controlExample Elbow JointHumerus bound by fibrous ligaments to radius and ulnaFlexorsbrachialis whose tendons insert into the humerous at one end and into ulna at the other endbiceps brachii and coracobrachialisSynergists muscles working togetherExtensorstriceps brachii and anconeus Antagonists muscles working in opposite directionsAxial Muscles muscles responsible for movements of the trunk maintains postureProximalGirdle Muscles move the shoulder elbow pelvis and knee locomotionDistal Muscles move the hands feet and digits manipulation of objects LOWER MOTOR NEURONSomatic musculature innervated by somatic motor neurons in the ventral horn of spinal cord AKA lower motor neuronsfinal common pathway for the control of behavior OrganizationAxons of lower motor neurons bundle together to form ventral roots each ventral root joins with a dorsal root to form a spinal nerve that exists the cord through the notches between vertebrae30 spinal nerves on each sideSpinal segment consists of the motor neurons that provide fibers to one spinal nerveSegments cervical 18 thoracic 112 lumbar 15 sacral 15Motor neurons that innervate distal and proximal musculature found mainly in the cervical and lumbarsacral segments those innervating axial musculature found at all levelsCells innervating axial muscles are medial to those innervating distal musclesCells innervating flexors are dorsal to those innervating extensorsAlpha Motor Neurons AMNTwo types of lower motor neurons alpha and gammaAMN directly trigger the generation of force by musclesMotor Unit one AMNall the muscle fibers it innervates
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