MOVEMENT

• Axon branching


  Innervating several muscle fibers
• Movements can be more precise

  Where each axon innervates only a few fibers, as with eye muscles, than where it innervates many fibers, as with biceps muscles
• This difference allows the eye to move more precisely than the biceps
• Fast contractions and rapid fatigue


  Prolonged use results in fatigue because the process is anaerobic - using reactions that do not require oxygen at the time but need oxygen for recovery
• Using them builds up an oxygen debt
• Neuromuscular junction

  A synapse between a motor neuron axon and a muscle fiber
• In skeletal muscles, every axon releases acetylcholine at the neuromuscular junction, and acetylcholine always excites the muscle to contract
• Deficit of acetylcholine or its receptors impairs movement
• Antagonistic muscles

  Moving a leg or arm back and forth requires opposing sets of muscles
• Biceps


  A flexor
• Triceps

  An extensor
• Smooth muscles


  Control the digestive system and other organs, consists of long, thin cells
• Cardiac muscles

  Found in the heart, consists of fibers that fuse together at various points, control the heart
• Skeletal/Striated muscles


  Consists of long cylindrical fibers with stripes, control movement of the body in relation to the environment
• Movements depend on overall plans, not just connections between a stimulus and a muscle contraction
• Damage to different brain locations produces different kinds of movement impairment
• Brain damage that impairs movement also impairs cognitive processes. Control of movement is inseparably linked with cognition
• Movements vary in sensitivity to feedback, skill, and variability in the face of obstacles
• Slow-twitch fibers

  Less vigorous contractions and no fatigue, do not fatigue because they are aerobic - they use oxygen during their movements
• Fast-twitch fibers


  Percentages of fast-twitch and slow-twitch fibers vary based on genetics and training
• Swedish ultramarathon runner Bertil Järlaker


  • Built up so many slow-twitch fibers in his legs that he once ran 2,188 mi in 50 days with only minimal signs of pain or fatigue
• Competitive sprinters


  • Have more fast-twitch fibers and other adaptations for speed instead of endurance
• Proprioceptor


  A receptor that detects the position or movement of a part of the body - in these cases, a muscle
• Muscle spindle

  Responds to a stretch, located parallel to the muscle, when the muscle is stretched more than the antagonistic muscle, it sends a message to a motor neuron in the spinal cord, which sends a message back to the muscle, causing a contraction
• Golgi tendon organs

  Respond to increases in muscle tension, located in tendons at opposite ends of a muscle, act as a brake against an excessively vigorous contraction, detect the tension that results during a muscle contraction, their impulses travel to the spinal cord, where they excite interneurons that inhibit the motor neurons
• Vigorous muscle contraction inhibits further contraction by activating the Golgi tendon organs
• Reflexes are consistent automatic responses to stimuli, generally considered involuntary because they are sensitive to reinforcements, punishments, and motivations
• Ballistic movements are executed as a whole: Once initiated, they cannot be altered
• Central Pattern Generators are neural mechanisms in the spinal cord that generate rhythmic patterns of motor output
• The stimulus that activates a central pattern generator does not control the frequency of the alternating movements
• Motor program


  Fixed sequence of movements, once begun, the sequence is fixed from beginning to end
• By comparing species, we see that a motor program can be gained or lost through evolution
• The "knee jerk reflex" is an example of a stretch reflex
• Proprioceptors


  Latin: proprius, meaning "one's own"
• Two kinds of proprioceptors regulate muscle contractions
• Premotor Cortex


  Most active immediately before a movement, receives information about the target to which the body is directing its movement, as well as information about the body's current position and posture
• Prefrontal Cortex


  Also active during delay before a movement, stores sensory information relevant to a movement, important for considering the probable outcomes of possible movements
• Damage to the prefrontal cortex may result in disorganized movement such as showering with your clothes on or pouring water on the tube of toothpaste instead of the toothbrush
• Saccade


  A voluntary eye movement from one target to another
• Posterior Parietal Cortex


  Monitors the position of the body relative to the world, proportionately larger in humans than most other primates