Muscles & Control of Body Movement

Muscles & Control of Body Movement

1. skeletal

   • striated
   • contract in response to somatic motor neuron
     • muscle tension
     • neuromuscular junction
       • excitation-contraction coupling
         • Calcium release
           • sarcoplasmic reticulum
           • lots of calcium = lots of racheting --> contracting (sarcomere shortening)
           • acetylcholine release
             • somatic motor neuron
             • bind to receptors on sarcolemma
               • sodium in (more), potassium in
                 • depolarize
           • bind to troponin
             • tropomyosin moves away from actin
               • myosing & actin can bond strongly
                 • ATP for release of myosin head
                   • phosphocreatine in cytoplasm breakdown; short (limited)
                   • anaerobic glycolysis: takes a while for blood vessels to dilate, short period (longer than phosphocreatine)
                   • aerobic respiration: citric acid cycle and etc slow, requires oxygen, LARGE amount of energy marathon
                   • *Rigor mortis: no ATP = unable to release myosin heads
                   • power stroke
                   • hydrolysis
                   • Fatigue theories
                     • peripheral = predominant theory
                     • depletion of glycogen stores
                       • run out around 20 miles
                     • ions
                       • Calcium
                       • Potassium
                     • tetanus
                 • cross bridge
           • DHP receptor & RyR receptor (know involved)
             • relay change in levels
     • motor units
       • group of muscle fibers that function together and controlled by motor neurons, innervates split end 1 axon/motor unit
       • recruitment of motor units to increase force asynchronous to avoid fatigue shaking = switching back and forth between motor units
       • 1 motor unit to multiple fibers
     • optimum force
   • structure
     • tendons
       • attach to bone
     • origin
       • closest to more stationary
     • insertion
     • muscle fibers
       • alpha
       • long, cylindrical
       • several hundred nuclei
         • fusion of embryonic
         • satellite (committed stem) cellsj just outside
       • bundled into fascicles
         • collagen, elastic fibers, nerves and blood vessels
       • compare to sewer system; move things more quickly
         • t-tubule: faster action potential
       • thick filaments: myosin
       • thin filaments: actin
       • muscle twitch
         • fast
           • glycolytic paler fastest easily fatigueddon't need myoglobin
           • oxidative glycolytic
         • slow
           • oxidative, mitochondria RED (myoglobin)
         • summation (limited ability)
     • be at least familiar with sarcomere unit bands
   • antagonistic muscle groups
     • extensor (bones away)
     • flexor (bones towards)
   • contraction
   • largest cell type, massive distance

2. cardiac

   • intercoded discs for Ca flow
   • single nucleus
   • electrically linked
     • ...can have some heartbeats when dead

3. smooth

   • don't need to worry too much about structure
   • small
   • mostly involuntary (autonomic)
   • communication
     • gap junctions
     • varicosities
     • single vs. multi-unit
   • contraction
     • no bundling
     • Calcium in fluid
     • phosphotase
       • different sensitivites
   • tonic & phasic
   • slower, less energy used
   • large range
   • different potentials
     • pacemaker
   • regulation
     • hormones, paracrines

4. neural reflexes

   • somatic or autonomic brainstem or spinal cord (faster)
   • nothing on innate/inborn vs. learned reflexes
   • spinal reflex (child nodes not actually that related)
     • basal ganglia parkinson's = death of
     • integration in CNS
     • voluntary: corticospinal tract
       • most complicated
       • motor cortex
         • cerebellum
         • basal ganglia
         • brain stem as relay and integration center
   • *TABLE 13.3*

5. autonomic reflexes

   • slowest
   • CNS

6. skeletal muscle reflexes

   • polysynaptic
   • proprioceptors
     • stabilizing reflex
     • joint
     • golgi tendon organ
       • extrafusal fibers
   • muscle spindles
     • embedded in middle
     • stretch, intrafusal fibers
   • alpha-gamma coactivation
   • myotatic unit
     • patellar tendon reflex collection of pathways controlling single joint quick, monosynaptic
     • crossed extensor reflex more complex movement simultaneous; polysynaptic
     • reciprocal inhibition

7. mechanics

   • not too heavy

8. Disorders

   • Duchenne muscular dytrophy
   • McCardle's disease
     • cannot convert glycogen

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