Exercise Sciences Flashcards
What are the major muscle groups? (12) Where are they located? (origin and insertion (ANATOMY BOOK)
Forearms Biceps Triceps Shoulders Quadriceps Hamstrings Calves Abdominals Chest Trapezius - neck, upper back Latissimus Dorsi - mid, low back Glutes
Major Muscles - Anterior (15) (O and I)
Deltoid Pectoralis Major Biceps Brachii Rectus Abdominis Brachialis External Oblique Brachioradialis Finger flexors (FIND) Adductor Longus Gracilis Sartorius Rectus Femoris Vastus Lateralis Vastus Medialis Tibialis Anterior
Major Muscles - Posterior (12) (O and I)
Trapezius Infraspinatus Teres Major Triceps Brachii Latissimus Dorsi Finger Extensors (FIND) Gluteus Maximus Semitendinosus Biceps Brachii Semimebranosus Gastrocnemius Soleus
Describe muscle organization from smallest to largest functional unit (???????????)
Myofilaments (actin, myosin) Myofibril Sarcoplasm Sarcolemma Endomysium (between fibers) Fasciculi Perimysium Muscle Fibers Epimysium
Components of the contractile unit
Motor neuron Neuromuscular junction Motor unit Sarcoplasm Myofibrils Myofilament (action and myosin)
Process of Sliding Filament Theory of muscle action (4)
1) States that actin filaments at each end of sacromere slide inward on myosin filaments, pulling Z-lines toward center of sacromere, thus shortening the muscle fiber.
2) As actin slides over myosin, both H-zone and I-band shrink.
3) The action of myosin cross-bridges pulling on actin is responsible for movement of actin.
4) B/c of very small displacement of action w/ each flexion of of myosin cross-bridge, very rapid, repeated flexions must occur in many cross-bridges throughout entire muscle for measurable movement to occur.
What are the different types of muscle actions? (3)
Concentric
Eccentric
Isometric
Discuss the difference in force production based on muscle action
https://www.youtube.com/watch?v=ERWQXiuwCFc
Concentric: as velocity increases, force decreases.
Eccentric: as velocity increases, force produced increases until plateau (doesn’t decrease).
Isometric: velocity is 0 b/c joint does not move, thus there is 0 force
you can lower more weighed eccentrically than you can push during concentric contraction.
What factors affect the production of force within a muscle? (9) pages 30-33
Neural Control Muscle Cross-Sectional Area Arrangement of Muscle Fibers Muscle Length Joint Angle Muscle Contraction Velocity Joint Angular Velocity Strength-to-Mass Ratio Body Size
Motor Unit
A motor neuron and the muscle fibers it innervates.
All muscle fibers of a motor unit contract together when they’re stimulated by the motor neuron.
Typically several hundred muscle fibers per motor unit.
Motor Unit structure
Nucleus Dendrites Axon Nodes of Ranvier Myelin Sheath NMJ on muscle
Motor Unit and Muscle Activation
when a motor neuron fires an impulse or AP, all fibers it innervates are simultaneously activated and develop force.
Motor units and precision movements
ex. eye muscles
The extent of control of a muscle depends on the number of muscle fibers within each motor unit.
Muscle req. greater precision can have motor units w/ as few as 1 muscle fiber per unit.
Changes in number of active motor units in small muscles can produce the extremely fine gradations in force that are necessary for precise movements of the eyeball.
Motor units and less precise movements
ex. quad muscles
may have several hundred fibers served by one motor neuron.
Motor unit abnormailities
weakness or loss of contraction strength of the muscle.
can result in muscle:
Atrophy
Fasciculations (involuntary twitches)
Hypotonia (decrease in tone of skeletal tone)
Hyporeflexia (decreased muscle stretch reflexes; rapid stretching)
Muscle Fiber Types
Type I (slow twitch) Type IIa (fast twitch) Type IIx (fast twitch)
Fast Twitch Motor Unit
develops force and also relaxes rapidly and thus has a short twitch time.
Slow Twitch Motor Unit
develops force and relaxes slowly and has a long twitch time.
Type I characteristics
motor neuron size recruitment threshold nerve conduction velocity contraction speed relaxation speed fatigue resistance endurance force production power output aerobic enzyme content anaerobic enzyme content SR complexity capillary density myoglobin content mitochondrial size, density fiber diameter Color
Small motor neuron size Low recruitment threshold Slow nerve conduction velocity Slow contraction speed Slow relaxation speed High fatigue resistance High endurance Low force production Low power output High aerobic enzyme content Low anaerobic enzyme content Low SR complexity High capillary density High myoglobin content High mitochondrial size, density Small fiber diameter Color red
Type IIa characteristics
motor neuron size recruitment threshold nerve conduction velocity contraction speed relaxation speed fatigue resistance endurance force production power output aerobic enzyme content anaerobic enzyme content SR complexity capillary density myoglobin content mitochondrial size, density fiber diameter Color
Large motor neuron size Intermediate/High recruitment threshold Fast nerve conduction velocity Fast contraction speed Fast relaxation speed Intermediate/Low fatigue resistance Intermediate/Low endurance Intermediate force production Intermediate/High power output Intermediate/Low aerobic enzyme content High anaerobic enzyme content Intermediate/High SR complexity Intermediate capillary density Low myoglobin content Intermediate mitochondrial size, density Intermediate fiber diameter Color White/Red
Type IIx characteristics
motor neuron size recruitment threshold nerve conduction velocity contraction speed relaxation speed fatigue resistance endurance force production power output aerobic enzyme content anaerobic enzyme content SR complexity capillary density myoglobin content mitochondrial size, density fiber diameter Color
Large motor neuron size High recruitment threshold Fast nerve conduction velocity Fast contraction speed Fast relaxation speed Low fatigue resistance Low endurance High force production High power output Low aerobic enzyme content High anaerobic enzyme content High SR complexity Low capillary density Low myoglobin content Low mitochondrial size, density Large fiber diameter Color White
Types of specialized sensory receptors (proprioceptors) (2)
Muscles Spindles
Golgi Tendons Organs (GTO)
Muscle Spindles
Consist of several modified muscle fibers (infrafusal) enclosed in a sheath of connective tissue and run parallel to normal fibers (extrafusal).
Provide info concerning muscle length and the rate of change in length.
Spindles indicate the degree to which the muscle must be activated in order to overcome a given resistance
Muscle Spindles activity during stretch (4)
1) muscle lengthens and spindles stretch
2) this deformation activates sensory neuron of spindle, sending an impulse to spinal cord
3) impulse to spinal cord synapse (connect) w/ motor neurons
4) this activates motor neuron that innervates the same muscle (muscles contracts)
Muscle Spindles indicate degree to which muscle must be activated in order to overcome a given resistance. As load…
as load increases, the muscle is stretched to a greater extent, and engagement of muscle spindles result in greater activation of the muscle
Muscle spindles that perform precise movements…
have many spindles per unit of mass to help ensure exact control of their contractile activity.
ex. knee jerk flex
Muscle spindle activity during knee jerk flex
1) tapping tendon of knee extensor muscle group below patella stretches muscle spindle fibers
2) this causes activation of extrafusal muscle fibers in same muscle group
3) knee jerk occurs and the muscle actively shortens
4) this shortens intrafusal fibers and causes their discharge to cease
Muscle spindle location
inside muscle, parallel to extrafusal fibers (normal muscle fibers).
Golgi Tendon Organs (GTOs) location
in tendons near myotendinous junction and are in series (attached end to end) w/ extra fusal fibers).
Golgi Tendon Organs (GTOs)
1) activated when tenon attached to active muscle is stretched
2) as muscle tension of muscle increases, discharge of the GTO increases
3) GTO sensory neuron synapses w/ inhibitory interneuron in spinal cord, inhibiting a motor neuron that serves the activated muscle.
4) result is reduction in tension within the muscle and tendon.
Muscle spindles ______ muscle activation, GTO ______ muscle activation
spindles facilitate activation
GTOs inhibit activation
GTOs inhibitory process is though to provide…
a mechanism that protects against development of excessive tension
Effect of GTO during low and high forces
Low forces: minimal effect
High forces: reflexive inhibition activates, causing muscle to relax
