Term
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Definition
| Cellular events leading to a basic muscle action |
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Term
| How much of the body weight is muscle? |
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Definition
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Term
| How much of muscle is protein and water? |
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Definition
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Term
| Smooth muscle (Function and location) |
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Definition
Involuntary muscle
In the walls of blood vessels and internal organs |
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Term
| Cardiac muscle (Function and location) |
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Definition
Controls itself with help from nervous and endocrine systems
Only in the heart |
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Term
| Skeletal muscle (function and location) |
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Definition
Voluntary muscle; controlled consciously
Over 600 throughout the body |
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Term
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Definition
*Density ranges from ~150 to >200 per mm of fiber length
*Slow-twitch fibers tend to have a greater myonuclei density than fast-twitch fibers
*Changes in fiber size does not change myonuclear domain size
*Tight coupling between the quantity of genetic machinery and the protein requirements of a muscle fiber |
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Term
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Definition
| An individual muscle cell |
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Term
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Definition
| A muscle fiber enclosed by a plasma membrane |
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Term
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Definition
| The cytoplasm of a muscle fiber |
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Term
| What allows transport of substances throughout the muscle fiber? |
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Definition
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Term
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Definition
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Term
| Structure of myosin molecule |
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Definition
| Each MHC (myosin heavy chain) is composed of a head (motor domain), which contains ATP- and actin-binding sites, and is connected to a long tail by a thin neck region to which the MLC's (myosin light chains) are bound. |
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Term
| Different types of Myosin Heavy Chains |
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Definition
*MHC I- slow skeletal muscle
*MHC IIA- fast skeletal muscle
*MHC IIB- fast skeletal muscle (rat)
*MHC IIX- fast skeletal muscle
*MHC-emb- developing skeletal muscle
*MHC-neo- developing skeletal muscle |
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Term
| Which is more abundant? Actin or myosin |
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Definition
| Actin (regulates tension generation) |
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Term
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Definition
| Protein that is responsible for turning on muscle contraction and is composed of three parts |
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Term
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Definition
*Tn-T binds troponin to tropomyosin
*Tn-C binds calcium during contraction
*Tn-I inhibitory on tropomyosin when there is no Ca2+ |
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Term
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Definition
| functions as a molecular ruler that specifies the length of the thick (myosin) filament |
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Term
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Definition
| Functions as a molecular ruler that specifies the length of the thin (actin) filament |
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Term
| Actin:Myosin ratio in human skeletal muscle |
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Definition
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Term
| What is the sliding filament theory? |
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Definition
*When myosin cross-bridges are activated, they bind strongly with actin, resulting in a change in the cross-bridge
*The change in the cross-bridge causes the myosin head to tilt toward the arm of the cross-bridge and drag the actin and myosin filaments in opposite directions
*The tilt of the myosin head is known as a power stroke
*The pulling of the actin filament past the myosin results in muscle shortening and generation of muscle force |
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Term
| Calcium levels in extracellular and intracellular environments |
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Definition
Extra (interstitial fluid)- 0.001 mM
Intra- 0.0000001 mM |
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Term
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Definition
*Calcium is bound to calsequestrin (storage protein) in the SR
*During muscle contraction, the intracellular can increase 100-1000 times the resting level
*Diffusion distance for Ca2+ from SR to myofibril is 2-4 micrometers
*The SR is connected to the T-tubule system by feet-like projections (ryanodine receptor/DHP receptors) |
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Term
| What is muscle contraction? |
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Definition
| Cellular events leading to a basic muscle action |
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Term
| Events leading to Muscle Fiber Action |
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Definition
1) Action potential- release of ACh at the neuromuscular junction
2) ACh binds to receptors causing action potential to "spread" over the muscle fiber into the T-tubules and stimulate the SR
3) Action potential release of Ca2+ from the SR
4) Ca2+ binds to troponin causing a shift in the tropomyosin revealing active sites of actin
5) Breakdown (hydrolysis) of ATP to ADP "cocks" myosin head
6) "Cocked" myosin attaches to actin and movement (muscle contraction) occurs
7) Cross-bridge detachment requires new ATP
8) Events occur as long as Ca2+ is present
9) Ca2+ is present as long as action potential are delivered to the SR
10) In the absence of AP the SR recycles (takes up) the Ca2+
11) Troponin and tropomyosin shift back to their resting position (therefore no muscle contraction) |
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Term
| What is muscle action initiated by? |
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Definition
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Term
| What does the nerve releasing cause? |
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Definition
| Releases ACh, which allows sodium to enter and depolarize the cell. If the cell is sufficiently depolarized, an action potential occurs which releases stored Ca2+ ions |
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Term
| What does Ca2+ ions binding with troponin cause? |
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Definition
| When Ca2+ ions bind with troponin, it lifts the tropomyosin molecules off the active sites on the actin filament. These open sites allow the myosin heads to bind to them. |
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Term
| When myosin binds with actin, what happens? |
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Definition
| The myosin heads tilts and pulls the actin filament so they slide across each other. |
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Term
| When does muscle action end? |
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Definition
| It ends when the calcium is pumped out of the sarcoplasm to the sarcoplasmic reticulum for storage. |
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Term
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Definition
| Energy for muscle action is provided when the myosin heads binds to ATP. ATPase on the myosin head splits the ATP into a usable energy source. |
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Term
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Definition
Hollow needle is inserted into muscle to take sample
*Sample is mounted, frozen, thinly sliced, and examined under a microscope.
*allows study of muscle fibers and the effects of exercise and training on fiber composition. |
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Term
| Slow-twitch muscle fibers |
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Definition
*High aerobic (oxidative) capacity and fatigue resistance
*Low anaerobic (glycolytic) capacity and motor unit strength
*Slow contractile speed (110 ms) and myosin ATPase
*10-180 fibers per motor neuron
*Low sarcoplasmic reticulum development |
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Term
| Fast-Twitch (FTa) Muscle Fibers |
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Definition
*Moderate aerobic (oxidative) capaicty and fatigue resistance
*High anaerobic (glycolytic) capacity and motor unit strength
*Fast contractile speed (50 ms) and myosin ATPase
*300-800 fibers per motor neuron
*High SR development |
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Term
| Fast-Twitch (FTb/x) Muscle Fibers |
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Definition
*Low aerobic (oxidative) capacity and fatigue resistance
*High anaerobic (glycolytic) capacity and motor unit strength
*Fast contractile speed (>50 ms) and myosin ATPase
*300-800 fibers per motor neuron
*High SR development |
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Term
| Motor Unit Force Development |
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Definition
| The difference in force development between FT and ST motor units is due to the number of muscle fibers per motor unit, not the force generated by each fiber |
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Term
| What determines fiber type? |
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Definition
*Genetics determine which motor neurons innervate our individual muscle fibers
*Muscle fibers become specialized according to the type of neuron that stimulates them
*Training and muscular inactivity may result in small changes in the percentage of FT and ST fibers
*Aging may result in changes in the percentage of FT to ST fibers |
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Term
| What fiber type does skeletal muscle contain? |
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Definition
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Term
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Definition
| ATPase in FT fibers acts faster providing energy for muscle action more quickly than ATPase in ST fibers |
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Term
| Do FT or ST have more developed SR enhancing calcium delivery? |
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Definition
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Term
| Do FT or ST have larger motor units? |
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Definition
| Motor units supplying FT fibers are larger than ST; thus, FT motor units can recruit more fibers |
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Term
| What are ST fibers suited for? |
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Definition
| High aerobic endurance and low-intensity endurance activities |
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Term
| What are FT fibers good for? |
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Definition
| Anaerobic or explosive activities |
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Term
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Definition
*For a motor unit to be recruited into activity the motor nerve impulse must meet or exceed the threshold
*When this occurs, all muscle fibers in the motor unit act maximally
*If the threshold is not met no fibers in that unit act
*More force is produced by activating more motor units |
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Term
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Definition
| Prime movers; responsible for movement |
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Term
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Definition
| Oppose the agonists to prevent overstretching of them |
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Term
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Definition
| Assist the agonists and sometimes fine-tune the direction of movement |
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Term
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Definition
| Muscle moves at same speed, while muscle force is measured. Motor driven machines using employ this type of motion (i.e. Cybex) |
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Term
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Definition
| Muscle force remains the same, while velocity of movement is measured. "Tonic" means same force. Example would be using free weights |
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Term
| Factors influencing force generation |
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Definition
*Number of motor units activated
*Type of motor units activated (FT or ST)
*Muscle size
*Initial muscle length (myosin/actin overlap)
*Joint angle
*Speed of muscle action (shortening or lengthening) |
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Term
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Definition
| Concentric, eccentric, static |
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Term
| How do you increase force production? |
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Definition
| Recruiting more motor units |
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Term
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Definition
| All joints have optimal angle at which the muscles crossing the joint produce maximal force |
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Term
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Definition
| The angle of maximal force depends on the relative position of the muscle's insertion on the bone and the load placed on the muscle |
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Term
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Definition
| The speed of action affects the amount of force produced |
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Term
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Definition
| The maximal force a muscle or muscle group can generate |
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Term
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Definition
*The product of strength and the speed of movement
*Power=Force X Velocity |
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Term
| What is muscular endurance? |
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Definition
*The capacity to sustain repeated muscle actions
*Can be evaluated by noting the number of repetitions you can perform at a given percentage of your 1-RM
*Is increased through gains in muscular strength
*Is increased through changes in local metabolic and circulatory function |
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Term
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Definition
*Hypertrophy- refers to increase in muscle size
*Atrophy- refers to decreases in muscle size
*Muscle strength involves more than just muscle size |
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Term
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Definition
*Transient- pumping up of muscle during a single exercise bout due to fluid accumulation from blood plasma into the interstitial spaces of the muscle
*Chronic- increase of muscle size after long-term resistance training due to changes in muscle fiber number (fiber hyperplasia) or muscle fiber size (fiber hypertrophy) |
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Term
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Definition
*The number of myofibrils and actin and myosin filaments increase, resulting in more cross-bridges
*Muscle protein synthesis increases during the postexercise period
*Testosterone plays a role in promoting muscle growth
*Training at higher intensities appears to cause greater fiber hypertropy than training at lower intensities |
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Term
| Possible neural factors of strength gains |
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Definition
*Recruitment of additional motor units for greater force production
*Counteraction of autogenic inhibition allowing greater force production
*Reduction of coactivation of agonist and antagonist muscles
*Changes in the discharge rates of motor units
*Changes in the neuromuscular junction |
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Term
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Definition
*Muscle fibers split in half with intense weight training
*Each half then increases to the size of the parent fiber
*Satellite cells may also be involved in skeletal muscle fiber generation
*It has been clearly shown to occur in animal models; only a few studies show this occurs in humans too |
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Term
| Sensory-Motor Integration |
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Definition
1) A stimulus to the skin is received by a sensory receptor
2) The impulse travels through sensory neurons to the CNS
3) The CNS interprets the information and determines the motor response
4) The motor impulse travels out from the CNS through motor neurons
5) The motor impulse reaches the muscle fibers and the response occurs |
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Term
| Spinal cord integration center |
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Definition
| simple motor reflexes such as pulling your hand away after touching something hot |
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Term
| Lower brain stem integration center |
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Definition
| More complex subconscious motor reactions such as postural control |
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Term
| Cerebellum integration center |
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Definition
| Subconscious control of movement such as that needed to coordinate multiple movements |
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Term
| Thalamus integration center |
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Definition
| Conscious distinction among sensations such as feeling hot or cold |
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Term
| Cerebral cortex integration center |
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Definition
| Conscious awareness of a signal and the location within body of the signal |
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Term
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Definition
*Sensory impulses evoke a response through a motor neuron
*The closer to the higher brain centers that the impulse stops, the more complex the motor reaction
*A motor reflex is a programmed response that is integrated by the spinal cord without conscious thought |
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Term
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Definition
*Lie between and are connected to regular skeletal muscle fibers
*The middle of the spindle cannot contract but can stretch
*When muscles attached to the spindle are stretched, neurons on the spindle transmit information to the CNS about the muscle's length
*Reflexive muscle contraction is triggered to resist further stretching |
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Term
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Definition
*Encapsulated sensory organs through which muscle tendon fibers pass
*Located close to the tendons attachment to the muscle
*Sense small changes in tension
*Inhibit contracting (agonist) muscles and excited antagonist muscles to prevent injury |
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Term
| Conscious control of movement |
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Definition
*Neurons in the primary motor cortex control voluntary muscle movement
*Clusters of nerve cells in the basal ganglia initiate sustained and repetitive movements--walking, running, maintaining posture, and muscle tone
*The cerebellum controls fast and complex muscular activity |
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Term
| What is the process by which your PNS relays sensory input to your CNS which processes the input and response with the appropriate motor signal |
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Definition
| Sensory-motor integration |
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Term
| Where is sensory input integrated? |
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Definition
| Spinal cord, brain stem, or in the brain depending on its complexity |
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Term
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Definition
| Automatic responses to a given stimulus |
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Term
| What triggers reflexes to protect the muscles from being overstretched? |
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Definition
| Golgi tendon organs and muscle spindles |
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Term
| What integrates sensory input for voluntary muscle action? |
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Definition
| Primary motor cortex, basal ganglia, and cerebellum |
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Term
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Definition
| Memorized motor patterns stored in the brain |
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Term
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Definition
| Each muscle fiber is innervated by only one neuron, but one neuron may innervate up to several thousand muscle fibers |
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Term
| T/F All muscle fibers within a motor unit are of the same fiber type |
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Definition
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Term
| Are ST or FT motor units called on first? |
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Definition
| ST are called on first because they have smaller neurons |
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