Movement And Muscles
Movements of our body are accomplished by contraction of the skeletal muscles –Flexion: Contraction of a flexor muscle draws in a limb – Extension: Contraction of extensor muscle •Skeletal muscle fibers have a striated appearance • Skeletal muscle is composed of two fiber types: –Extrafusal: innervated by alpha -motoneurons from the Spinal cord: exert force –Intrafusal: sensory fibers that detect stretch of the muscle •Afferent fibers: report length of in trafusal: when stretched, the fibers Stimulate the alpha- Neuron that innervates the muscle fiber: Maintains muscle tone •Efferent fibers: contraction adjusts sensitivity of afferent fibers. 3 Classes of Movement 1. Voluntary movements Complex actions Reading, writing, playing piano Purposeful, goal-oriented Learned Improve with practice 2. Reflexes Involuntary, rapid, stereotyped Eye-blink, coughing, knee jerk Graded control by eliciting stimulus http://www.muscleseek.com/muscles-anatomy-muscles-location/neck-muscles-structure-exercises-problems-diagnosis-treatments/
3. Rhythmic motor patterns Combines voluntary & reflexive acts Chewing, walking, running Initiation & termination voluntary Once initiated, repetitive & reflexive