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Muscle Contraction

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Muscle Contraction 10/19/2009 CONTROL OF MOVEMENT: STRIATED MUSCLES SKELETAL (STRIATED) MUSCLE: - each muscle = ____________________________________ - each muscle cell = _______________________________________ -Myosin: Filamentous___________________________________________ protein with cross bridges -Actin: _________________________________________________Filamentous protein where cross bridges of myosin bind ANATOMY OF SKELETAL MUSCLE ______________ _____________ ________ Extrafusal muscle fiber ________ _________ Myofibril _____________ __________________ ___________ MUSCLE CONTRACTION Watch muscle contraction movie Myosin Myosin cross bridges filament Actin filaments Actin MtfMovement of filament actin filament Myosin cross bridge Movement of myosin filament Heads of cross bridges: 1. Attach to active sites on actin filaments 2. “Ratchet” forward 3. Release 4. Repeat -Onlyoccurs in the presence of ________ How is calcium released? From___________________________ activity at neuromuscular ________junction 1 10/19/2009 NEUROMUSCULAR JUNCTION Synapse between terminal of _________________ and a ___________ is called a neuromuscular junction; Terminals of alpha motor neurons synapse on _____________- grooves along the surface of muscle fibers; When motor neuron fires, _____________ is liberated from terminals at the endplate and depolarizes muscle fibers - ________________; Depolarization of muscle fiber opens ________ _________________________, producing a large calcium influx into the fiber; Calcium triggers the actin-myosin “rowing” action leading to the __________ of muscle fibers; Calcium is extruded from fiber by “pump”; Endplate potential ______ cause muscle fiber to fire = contraction or “twitch” of fiber. MOTOR UNITS Motor unit: _______________________________________ ___________________________________ Motor pool: All motor neurons that innervate fibers of a single muscle. Muscle fibers Alpha motor neurons Axons - weak muscular contraction = _______________________ - strong contraction = _______________________ - discrete/fine movements = __________________________ ____________ - crude/gross movements = __________________________ ____________ 2 10/19/2009 Localization and distribution of motor neurons in the spinal cord Somatosensory (mechano) and nociceptive (pain) receptors Glabrous skin: _________________________________ Hairy skin: skin__________________________________ that covers the rest of the body There are 3 groups of somatosensory receptors: 1. ______________ 2. ______________ 3. ______________ 3 10/19/2009 Somatosensory pathway from receptors to somatosensory (primary) cortex: How pain reaches the somatosensory cortex 4 10/19/2009 How is the phenomenon of “referred pain” produced? Arm and shoulder pain “referred” from heart pain receptors during heart attack. MONOSYNAPTIC STRETCH REFLEX Involves: - _________________ - _________________________________ - ________________________________________ __________________________ - ______________________________ - ____________________________________ Watch stretch reflex movie 5 10/19/2009 How muscle spindles work! - Gamma motor neurons provide the ________ ________________________________ - without gamma motor neurons, the spindles would become __________________________“slack” and unresponsive to_______________ stretch. - gamma motor neurons function __________to adjust the length_______________________ of intrafusal muscles titto an appropriate degree of tension Gamma motor neurons Muscle spindles Extrafusal muscle Spindle “slack” - insensitive to strech Spindle “tight” - ready to respond to strech POLYSYNAPTIC REFLEXES: EXAMPLE OF WITHDRAWAL FROM PAIN - reflexes requiring _________________________ - concept of _______________________________ ____________________________ - ex., biceps vs. triceps of arms - reciprocal innervation (excitatory vs. inhibitory) -excitatory ________________________________________ and inhibitory interneurons work ____________________________________together to withdraw limb from pain. 6 10/19/2009 CROSSED EXTENSOR REFLEX Think of this reflex as being ____________“connected” with previous polysynaptic withdrawal reflex For example, if flexion reflex triggered in one leg, ___________________________________ All thi s h appens _________________________; the brain has nothing to do with it. This serves to: - _______________________________________help remove or push entire body away from _______________________painful stimulus; - _______________________________________help restore balance when flexed leg is _____________________withdrawn. An example of a complex sensorimotor reflex is ________. - spinal cat, when placed on a treadmill can ______________________________________initiate normal walking when provided with ______________________________________somatosensory feedback of treadmill on feet. GOLGI TENDON REFLEX or how not to shred your muscles and bones! Golgi Tendon Organ: ______________________receptor organ sensitive ________________________________________to stretch and located at the junction of the _____________________________tendon and muscle. - only contacts ________________________ - if maximally activated, ___________________ ________________________________ - helps prevent tearing of muscles and tendons from bone Golgi____________ tendon organ_______ ____________________Pseudounipolar _________neuron alpha______________________ motor neuron inhibitory_________________________ interneuron 7.
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