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