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PROPRIOCEPTION & KINESTHESIS p. 37• Proprioception – The ability to sense the position and location and orientation and movement of the body and its parts• Kinesthesis – The ability to feel movements of the limbs and body
PROPRIOCEPTION• Proprioceptors of the joints and skin – Meissner’s corpuscles – Ruffini’s corpuscles – Pacinian corpuscles – Krause’s end-bulbs
PROPRIOCEPTION• Proprioceptors of the muscles – Muscle spindles – Golgi tendon organs
Muscle Spindles• Provide proprioception• Sense the amount of stretch and the rate of stretch• Reflexes involving the muscle spindles is how we ‘feel’ a movement was done correctly• Spindles are a part of learning; we develop such reflexes as we practice skills and movements
Golgi Tendon Organs• Sensitive to muscle tension and active contraction• Protect muscle from excess contraction force• Stimulation of GTO an afferent impulse is sent to the central nervous system• In turn, efferent impulses are sent to the… – Agonist muscle causing it to relax – Antagonist muscle causing it to contract
Neuromuscular Summary•An example from baseball.•A pitcher throws a curve ball toSammy Sosa•Sammy’s eyes see the ball comingtowards him and is able to identifythe pitch as a curve ball•Sensory nerves (afferent) send thatinformation to the CNS•In the CNS the sensory nervesynapses with motor nerves•The motor nerves in turn stimulatesthe muscles (deltoid and pectoralismajor) required to swing the bat inthe proper position to hit the ball
Neuromuscular Summary•Inside the fibers of the deltoid andpectoralis major, calcium isreleased•The calcium allows myosin headsto attach to actin•When the heads swivel the fibersof the deltoid muscle will shorten•The shortening of the fibers willpull on the humerus causingSammy to swing the bat•The muscle spindles “tell” theCNS when the arm is in thecorrect position•If all goes as planned, the deltoidand pectoralis major will move hisarms into a position to hit the ball
Neuromuscular Summary• An example from weight training.• A man is having his muscular strength tested on the bench press• For his first lift, 50 pounds is put on the bar• He will be using his pectoralis major muscle with has 500 motor units (300 slow twitch and 200 fast twitch) and his triceps muscle• His CNS stimulates 280 motor units leading to his pectoralis major muscle (180 slow twitch and 100 fast twitch)• End nerve ending stimulates a separate muscle fiber
Neuromuscular Summary• Calcium is released, myosin attaches to actin and swivels.• The pectoralis major and triceps muscles shortens and his arm extends outward raising the bar with 50 pounds on it.• After a few minutes of rest, 100 pounds is place on the bar• This time he stimulates 380 motor units (260 slow twitch and120 fast twitch)• The weight is successfully lifted• After a few minutes of rest, 150 pounds is place on the bar
Neuromuscular Summary• This time he stimulates 460 motor units (280 slow twitch and 180 fast twitch)• As the pectoralis major muscle contracts the GTO in the pectoralis major are stimulated• They stimulate a sensory nerve leading to the CNS• In the CNS, the sensory nerve synapses with a motor nerve that will inhibit (relax) the pectoralis major muscle• The man is unable to successfully lift the 150 pounds.