Kin 152 Exam 2 Neuro/Muscle Contrac

  1. what is the purpose of the nervous system and what are its 2 major parts?

    describe them, and what type of info does each transmit

    CNS-brain and spinal cord.. afferent sensory info

    PNS-nerves that transmit information to and from the CNS.. efferent motor info
  2. what are the 2 components of the efferent (motor) division, describe each
    • Autonomic NS-its involuntary, controls things like HR and glands. It has sympathetic and parasympathetic components 
    • Somatic NS-its voluntary, controls things like the alpha motor nerve
  3. what generally relates to the number of muscle fibers per motor neuron that a muscle has?
    the function of that muscle's movement 

    the more delicate the movement, the less muscle fibers that the motor neuron will innervate. and vice versa
  4. what is a motor unit
    it makes up the functional unit of movement 

    it consists of the motor neuron and all of the muscle fibers that it innervates
  5. what is a motor neuron pool
    the group of alpha motor neurons that innervate a single muscle 

    ex. all of the motor neurons that innervate the muscle fibers on a bicep or tricep
  6. what essentially dictates the speed of a neural transmission within a fiber
    the size of a nerve fiber 

    • thicker=faster 
    • thinner=slower
  7. what does the muscle spindle respond to and do? why? 

    what kind of exercise is this particularly important in? explain
    it responds to changes in muscle fiber length(tension) and speed it induces contraction as a "stretch reflex" as a way to protect the muscle 

    • plyometrics. w/out muscle spindle, during these exercises we would essentially collapse because there would be no signal telling us to contract our muscles as they're stretched
    • Greater nerve action above voluntary and involuntary.
  8. what are the 3 main components of the "stretch reflex" (the steps to make it happen)
    • 1. the muscle spindle responds to the stretch in the muscle 
    • 2. the afferent nerve fiber sends sensory information to from the spindle fiber to the muscle cord 
    • 3. the efferent nerve fiber, or the alpha motor neuron, activates the stretched fiber
  9. what are 2 protection mechanisms in the muscle
    golgi tendon organ and muscle spindle
  10. what is the golgi tendon organ (GTO)? what 2 situations does it respond to and do during each? why?
    • its a tendon that detects the tension or force of active muscle when it shortens
    • -it induced a "reflex inhibition", and causes the muscle to relax. ex. bench pressing and your muscles "giving out" during last rep or during too much weight

    • when it stretches passively (static stretching) 
    • -causing you to fall further into your stretch

    this is a protection mechanism
  11. what do pacinian corpusles do?
  12. they sense movement in pressure and movement
  13. what does the alpha (anterior) motor neuron do?
    it transmits impulses from the spinal cord to the muscle
  14. What causes depolarization?
    a decrease in the charge gradient causing the inside of the cell to become more positive 

    a signal moves down the axon opening the sodium channel. Sodium moves into the cell rapidly, causing it to become more positive (depolarization). This triggers the potassium gates to open, causing K+ to move out of the cell slowly, shutting off the Na+ channel and leading to repolarization (making the cell more negative again)

    these gates are voltage gated (triggered by the electrical signals across the membrane)
  15. What is proprioception?
    How is proprioception important in exercise and sport performance?
    • -awareness of your body in space and time and its sequence of movements.
    • -vestibular feedback
    • -kinesthetic feedback

    awareness of your body in space and time and its sequence of movements. proprioceptors are sensitive to tension, pressure, and stretch (golgi organ tendon, pacinian corpusle, and muscle spindle)
  16. How is a nerve impulse transmitted down the axon of a neuron?
    • -the wave of depolarization travels down the axon. all of the voltage gates for K+ and Na+ transport proteins are all along the length of the axon (rapidly depolarizing and repolarizing the cell) 3 milliseconds 
    • -the depolarization terminates at the end of the nerve (terminal branches of axon)
    • -the bulbs on the end of the nerve are what touch the muscle fiber at the neuromuscular junction
    • -when the depolarization gets to the junction, ca++ is released into the nerve. This calcium triggers the release of the neurotransmitter, acetylcholine, which is what tells the tissue to make an action
  17. What role does myelin play in nerve transmission?
    makes the nerve thicker=it speeds up transmission
  18. what is the motor end plate?
    What is the neurotransmitter released from the motor neuron?
    • -the axon depolarization terminates at the end of the nerve at the motor endplate
    • -the motor end plate is where acetylcholine is released, it contains receptors for them to bind onto. causes either depolarization or hyperpolarization.
  19. How does the motor end plate know when to release acetylcholine? 

    what then happens at the muscle?
    the acetylcholine is held in vesicles. When the calcium is released into the nerve, it tells the vesicles to release acetylcholine to the muscle via exocytosis. Ach is now saying, take action!

    the depolarization (contraction) is now at the muscle, where the muscle is up taking Na+ and K+
  20. what happens after the muscle depolarizes and contracts? 

    what might cause muscle fatigue?
    the muscle has to prepare to depolarize again. ACH has to let go of the receptor, so acetyl CoA has to be broken down, and its parts are taken back up into the cleft and synthesized again. This costs a bit of energy and might cause muscle fatigue (some of it is washed out)
  21. what is depolarization? 

    what is hyperpolarization?

    relaxation/inhibition of contraction
  22. Why does repetitive heavy muscle contraction cause a heterogeneous blood flow to the muscle?
    When a muscle makes a contraction, the pressure that builds up in the arteries closes off blood flow. 

    it goes down during contraction, then goes back up during relaxation. its constantly changing
  23. how are making ATP if blood flow is heterogeneous, and blood flow is decreased during contraction.. which is the most metabolically demanding time frame?
    we have to accelerate glycolysis and phosphagen breakdown during contraction to maintain the ATP pool and is paid back during relaxation phase.
  24. What is myoglobin?

    what makes it able to store O2?

    How is myoglobin different than hemoglobin?
    a protein in the muscles (myo=muscle) containing heme, which primarily functions O2 storage of the blood 

    Designed for low PO2 environments. It holds on to oxygen and doesn't let go until the muscle has 5 mmHg of O2 during exercise. That's near 0!

    Myoglobin is a protein found exclusively in muscle tissue and only binds 1 oxygen at a time, when hemoglobin binds 4

    *no bohr effect
  25. What are the T­tubules?
    • the action potential gets down into the muscle via the Tubules. The Ttubule carries the depolarization down into the muscle. 
    • They're connected to the sarcoplasmic reticulum
  26. what is the sarcoplasmic reticulum? what is its role during muscle contraction?
    • the storage point for calcium 
    • it comes in contact with the Ttubule at the triads. as the depolarization comes down the ttubule, it triggers voltage gates, enabling the SR to also depolarize. this causes the release of calcium onto the skeletal muscle. causes muscle contraction!
  27. what is a sarcomere?
    the functional/contractile unit of a myofibril that repeats from z line to z line

    striated appearance
  28. What is myosin? Actin?
    • ­ Actin­ The main protein that interacts with myosin during excitation­contraction coupling.
    • ­ Myosin­ Splits ATP and responsible for the “power stroke” of the myosin head.
  29. How are myosin and actin configured relative to one another?
    Myosin filaments lie along the line of muscle fiber’s actin filaments.
  30. Explain the roles of troponin and tropomyosin in muscular contraction.
    Troponin­ Binds Calcium and affects tropomyosin; represents the “switch” that transforms calcium signal into a molecular signal that induces crossbridge cycling.

    Tropomyosin­ Transduces the conformational change of troponin complex to actin

    The troponin releases the calcium causing tropomyosin to remove the blocking position on actin revealing actin’s active sites for myosin to bind on to.
  31. describe the 4 basic stages of a cross-bridge cycle
    • 1. formation of cross bridge: the activated myosin head binds to actin, and Pi is released to strengthen the bind
    • 2. power stroke: ADP is release and the the myosin head pivots, pulling thin myofilaments to sarcomere (this is contraction/shortening) 
    • 3. bridge detachment: when ATP binds to myosin head, the myosins bind to the actin weakens causing it to detach 
    • 4. reactivation of myosin head: ATP is hydrolized to ADP and Pi. the energy released during this returns it to its cocked or relaxed position (this is how myosin head is activated)
  32. what triggers cross bridge cycle?
    when calcium from the SR binds to troponin. the troponin changes shape so that the tropomyosin can move away from the binding sites of action, so that myosin can attach
  33. Explain ATPs role in muscular contraction.
    ­ Splitting of ATP yields energy for muscle action. ­ Activates crossbridges, causing them to oscillate, producing a conformational change in myosin's head
  34. Explain how a low ATP pool could induce fatigue.
    if there is a low ATP pool, the myosin head wouldn't be able to be hydrolyze and be cocked back into its relaxed state
  35. What about the muscle determines the muscle's performance (force and power capacity) 

    is it adapable?

    does muscle fiber type predict preformance?
    • its sarcomere alignment and length (its muscle fiber layout, or mechanics) 
    • yes, its adaptable.

  36. what makes a pennate muscle, and why is it significant in exercise?
    • -pennate muscle has short fibers packed into a long muscle
    • -it generates a lot of force (think quad or hamstring)
  37. what makes a fusiform muscle and why is it significant?
    • -fusiform muscle has long fibers that run longitudinally to the muscle 
    • -it favors endurance and speed, it has a poor force production
  38. what is PCSA? 
    physiologic cross sectional area 

    does fusiform or pennate muscle have a larger PCSA? why?
    the total cross sectional area of all fibers within a muscle

    pennate muscle because of "fiber packing"
  39. What are the three motor unit types? Name in order from fastest to slowest moving enzyme and conduction speed. what does this tell us

    Also, divide into TYPE 1 vs 2
    • FG>FOG>SO
    • -tells us the contraction cycle rate

    • Type 1: slow twitch (SO) 
    • Type 2: fast twitch 
    • -type 2a is FOG
    • -type 2b is FG
  40. What nerve characteristics of slow twitch fibers (SO)

    think structurally, metabolically, old thinking of function.. new thinking of function
    • -small fiber, high in mito, high in cap
    • -fat stores, its an oxidative enzyme
    • -old: thought to be related to endurance, but actually used in endurance and strength
  41. What nerve characteristics of fast twitch fibers (FOG and FG)

    think structurally, metabolically, old thinking of function.. new thinking of function

    • -large fiber, high in mito, med in cap
    • -glycogen, PCr, some fat, but with glycolytic enzymes
    • -old: related to speed/power, but also does endurance

    • FG
    • -large fiber, low in mito, low in cap
    • -glycogen, PCr, with glycolytic enzymes
    • -old: related to speed/power, but also does endurance
  42. why is SO the first motor unit type to be activated even though it has low conduction? why does it have low conduction?
    • -it has the smallest cell body, so it has a lower threshold for depolarization 
    • -the signal moves slower because the nerve is structurally the smallest/thinnest
  43. How does chronic endurance training changes these characteristics?
    -any kind of chronic over load (endurance and resistance training) will cause a transition from fast twitch fibers to slow twitch fibers 

    slow to fast happens with no training or factors that are similar
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Kin 152 Exam 2 Neuro/Muscle Contrac
exam 2 kin 152