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Gisselle Reyes, period 5, Muscular system, cross bridge cycling: …
Gisselle Reyes, period 5, Muscular system
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muscle coverings
- Epimysium: dense irregular connective tissue that surrounds entire muscle
- Perimysium: fibrous connective tissue that surrounds fascicles
- Endomysium: fine areolar connective tissue that surrounds muscle fiber
Myofibrils features
- Striations:
- A bands: dark regions
- I bands: lighter region
- Sarcomere: smallest contractile unit
- Myofilaments:
- Actin (thin): made of 2 actin myofilaments twisted together and had myosin binding sites
- Myosin (thick): has myosin heads and powered by ATP
- tropomyosin and troponin are regulatory proteins bound to actin
Skeletal muscle names
- Facial muscles:
- Frontalis, temporalis, orbicularis oculi, zygomaticus, orbicularis Oris, masseter
- Anterior Arms:
- Deltoid, triceps brachii, flexor Carpi ulnaris, palmaris longus, flexor Carpi radilais, brachoradialis, pronator teres, brachiaris,
- Anterior superior muscles:
- serratus anterior, rectus abdominis, external oblique, tensor fasciae latae, lliopsoas, sartorius, pectineus, pectoral major
- Anterior Inferior muscle:
- Adductor Longus, vastus lateralis, rectus femoris, vastus medialis, tibialis anterior, soleus, gastrocnemilus, extensor digitorum Longus, fibularis Longus, lliotibial tract band, gracilis, sartorius
- posterior Superior muscles:
- occipitalis, sternocleidomastoid, trapezius, infraspinatus, major, phomboid, latissimus Dorsi,
- posterior Inferior muscles:
- semitendinosus, biceps femoris,seimbranosus, gastrocnemius, soleus, Adductor Magnus, gracilis, fibularis longus
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neuromuscular junction
- Action potential arrives at axon terminal
- calcium channel opens and calcium enters motor neuron
- calcium releases Ach to synaptic cleft
- ACh diffuses to ACh receptors
- Na+ enters resulting in end plate potential
- Acetylcholinesterase degrades ACh
Action potential
- action potential is caused by electrical changes
- End plate potential: change in electrical charge caused by neurotransmitters binding to the postsynaptic membrane
- Depolarization: cell’s membrane potential becomes less negative making it more likely to trigger an action potential
- Repolarization; restoration of the membrane potential to the initial resting state
- refractory period: muscle fiber cannot be stimulated for a specific amount of time
Dieases
- Muscular Dystrophy: Muscle weakness and atrophy
- Fibromyalgia: muscle pain
- Mysathenia Gravis: Neurmuscular disorders that blocks neurotransmitters
- Cerebral Palsy: spastic paralysis causing muscle contraction
- Myositis: Inflammation of the muscle
- cross bridge cycling:
- Cross bridge formation: high-energy myosin head attaches to thin filament
- Working (power) stroke: myosin head pivots and pulls thin filament toward M line
- Cross bridge detachment: ATP attaches to myosin head, causing cross bridge to detach
- Cocking of myosin head: energy from hydrolysis of ATP “cocks” myosin head into high energy state
- Muscle contractions:
- Isometric contraction: no shortening; muscle tension increases but does exceed load
- Isotonic contraction: muscle shortens because muscle tension exceeds load
- Muscle twitch: simplest contraction resulting from a muscle fiber’s response to a single action potential
- Prime mover: produce a specific movement
- Antagonist: opposes prime mover
- Synergist: helps prime movers
- Fixators: type of synergist that immobilizes bone
- Factors of contraction:
- Number of muscle fibers stimulated
- Relative size of fibers
- Frequency of stimulation
- Degree of muscle stretch
- Aerobic exercise leads to an increase in muscle capillaries, the number of mitochondria, and myoglobin synthesis, resulting in greater endurance, strength, and resistance to fatigue
- Resistance exercise leads to muscle hypertrophy primarily due to an increase in fiber size, along with greater mitochondria, myofilaments, glycogen stores, and connective tissue, resulting in enhanced muscle strength and size
Naming skeletal muscles: muscle location, muscle shape, muscle size, direction of muscle fibers, number of origins, location of attachment, muscle action