Columnscontain ascending anddescending tracts.Ascending tracts-axons that conduct action potentialstoward the brainDescending tracts-axons that conduct action potentialsaway from the brainGray Matter in Spinal Cord-The gray matter has a letter H shapewith horns.Posterior horns- contain axons whichsynapse with interneuronsAnterior horns- contain somaticneuronsLateral horns- contain autonomicneuronsCentral canal- fluid filled space incenter of cordSpinal Cord Cross Section
Reflexes-A reflex is an involuntary reaction inresponse to a stimulus applied to theperiphery and transmitted to theCNS.-The simplest reflex is the stretchreflex.Stretch Reflex-occurs when muscles contract inresponse to a stretching forceapplied to them.-knee-jerk reflex, or patellar reflex isa classic example of a stretch reflex.Withdrawal or Flexor Reflex-is to remove a limb or another bodypart from a painful stimulus.-sensory receptors are painreceptors, and stimulation of thesereceptors initiates the reflex.Spinal Nerves-Arise along spinal cord from union ofdorsal roots and ventral roots-Contain axons sensory and somaticneurons-Located between vertebra-Categorized by region of vertebralcolumn from which it emerges (C forcervical)-31 pairs-Organized in 3 plexusesCervical Plexus-Spinal nerves C1-4-Innervates muscles attached tohyoid bone and neck-Contains phrenic nerve whichinnervates diaphragmBrachial Plexus-Originates from spinal nerves C5-T1-Supply nerves to upper limb,shoulder, hand.Lumbosacral Plexus-Originates from spinal nerves L1 toS4-Supply nerves lower limbs
Dermatome-The nerves arising from each regionof the spinal cord and vertebralcolumn supply specific regions of thebody.-A dermatome is the area of skinsupplied with sensory innervation bya pair of spinal nerves.-Each of the spinal nerves except C1has a specific cutaneous sensorydistribution.BRAINBRAIN STEM-connects the spinal cord tothe remainder of the brainComponents:•Medulla oblongata•Pons•Midbrain•Reticular FormationMedulla oblongataLocation: continuous with spinal cordFunction:-regulates heart rate, blood vesseldiameter, breathing, swallowing,vomiting, hiccupping, coughing,sneezing, balanceOther:-pyramids: involved in consciouscontrol of skeletal musclePonsLocation-above medulla, bridge betweencerebrum and cerebellumFunction:-breathing, chewing, salivation,swallowing, relay station betweencerebrum and cerebellumMidbrainLocation: above ponsFunction:-coordinated eye movement, pupildiameter, turning head toward noiseOther:-the dorsal part has the four colliculiwhich are involved in visual andauditory reflexes
Reticular FormationLocation-scattered throughout brainstemFunction:-regulates cyclical motor function,respiration, walking, chewing,arousing and maintainingconsciousness, regulates sleep-wake cycle.
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