Muscular System Flashcards
Skeletal Muscle
Single, very long, cylindrical, multinucleate cells with striations
Smooth Muscle
Single, fusiform, uninucleate; no striations
Cardiac Muscle
Brancing chains of cells; uninucleate; striations; intercalated discs
What is Neuromuscular Junction
Synaptic connection between terminal end of a motor nerve and a muscle
Neuromuscular Junction Steps
1) Nerve impulse reaches axon terminal of motor neuron
2) Calcium channels open, calcium enters the axon terminal
3) Synaptic vesicles to release the neurotransmitter acetylcholine by exocytosis
4) Acetylcholine diffuses across synaptic cleft and binds to receptors in sacrolemma
5) ACh opens channels that allow simultaneous passage of Na+ into the muscle fiber and K+ out of the muscle fiber. More Na+ ions enter than K+ ion leave, producing a local change in the electrical conditions of the membrane (depolarization). This eventually leads to an action potential
6) The enzyme acetylcholineterase breaks down ACh in synaptic clever, ending the process
Sliding Filament Model
1) ATP is split when myosin head is unattached
2) ADP and P are bound to myosin as cross-bridge forms between the myosin head and actin
3) Upon ADP and P release, power strike occurs; head bends and pulls actin
4) Binding of fresh ATP causes myosin head to return to resting position
Sarcolemma
Plasma membrane in muscle fibers
Sarcoplasm
The cytoplasm of a muscle cell
Sarcoplasmic
reticulum
A specialized smooth endoplasmic reticulum
T tubules
Consists of sarcolemma penetrating into the myocyte interior, allows transmission of the action potential
Myofibrils
A cylindrical bundle of sacromeres within the skeletal muscle cell
Sarcomeres
A functional unit of muscle fiber
Myofilaments: Actin
Thin filaments made of actin,
Myofilaments: Myosin
Thick filaments made of myosin
Endomysium
Connective tissue sheath wrapped around muscle fiber
Perimysium
Fibrous membrane wrapped around fascicles (bundle of muscle fiber)
Epimysium
Connective tissue that covers the muscle
Tendon
Indirectly attaches muscle to bone
Isotonic
Same tension, changing length
Myofilaments slide, muscle shortens and movement occurs
E.g., bending knees, lighting weights
Isometric
Same length, changing tension
Myosin filaments are ‘spinning their wheels’, trying to slide but muscle is pitted against some more or less immovable object
E.g., pushing the palms together in front of you causes arm and chest muscles to contract isometrically
Origin
Attached to the immovable/less-moveable bone, anchor/leverage point
Insertion
Attached to the moveable bone, when contraction occurs insertion moves towards origin
Prime Mover
Major responsibility for causing a particular movement
Antagonist
Muscles that oppose or reverse a movement, are stretched and relaxed when prime mover is active
Synergist
Help prime movers by producing same movement or reducing undesirable movements
Fixator
Hold a bone still/stabalize the origin of a prime mover so all tension can be used to move the insertion bone
Flexion
decreases angle of joint and brings two bones closer together/BENDS
Extension
Increases angle or distance between two bones or parts of the body
Hyperextension
Extension that is greater than 180 degrees
Rotation
Movement of bone along its longitudinal axis
Abduction
Moving a limb away from the midline or median plane of the body
Adduction
Movement of a limb towards the midline or median plane of the body,
Circumduction
Proximal end of limb is stationary and its distal end moves in a circle, limb outlines as a cone
Dorsiflexion
Lifting the foot so the superior surface approaches the shin, point towards head
Plantar flexion
Pointing toes away from head
Inversion
Turn the sole medially
Eversion
Turn the sole laterally
Supination
Forearm rotates laterally so that the palm faces anteriorly or up
Pronation
Forearm rotates medially so that palm faces posteriorly
Opposition
Saddle joint between metacarpal 1 and carpals allows opposition of thumb
