Study Guide: Exam 3
49 Cards in this Set
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Functions of the muscular system (4)
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Locomotion, facial expression, posture, regulation of body temperature
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Origin definition
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The place where the muscle strts on a bone- stays stationary (fixed end of muscle)
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Insertion
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The place where the muscle ends on bone- moves toward the origin (movable end of muscle)
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Lever
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Rigid bar --> bone
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Fulcrum
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Fixed point around which the right bar (bone) moves --> joint
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First class levers and Example
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(LFE) = Load, Fulcrum, Effort
Ex: Load=Head pulling down, Fulcrum=Temporal, Effort=Muscle pulling head back
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Second class levers and Example
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(FLE)= Fulcrum, Load, Effort
Ex: No examples found in the body
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Third class levers and Example
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(FEL)- Fulcrum, Effort, Load.
Ex: Most common type of lever in the body. Very inefficient energetically but yields controllable movements. F=Fulcrum, E= Bicep Brachii, L=Weight in hand
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Flexion/Extension
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Movement to reduce or increase the angle between articulating bones at a joint in the anterior/posterior plane
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Abduction/Adduction
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Movement away or toward the longitudinal axis (or midline) of the body in the frontal plane
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Circumduction
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Combination of adduction/abduction and flexion/extension such that the distal end of a limb moves in a circle
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Rotation: Medial (internal) rotation & Lateral (external) rotation
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Refers to the movement away from the long axis of the trunk
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Protraction/Retraction
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Movement of a part of the body anteriorly or posteriorly in the horizontal body plane. (Mandible, clavicles, scapula)
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Elevation/Depression
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Movement of a part of the body superiorly or inferiorly in the frontal body plane (Mandible, scapula, clavicle)
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Dorsiflexion/Plantar flexion
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Flexion and extension of the foot at the ankle.
Dorsiflexion=flexion of the dorsal surface of the foot
Plantar flexion=flexion of the plantar surface of the foot
-Plantar surface=sole of the foot
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Inversion/Eversion
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Inversion- movement of the foot such that the plantar surface is turned inward
Eversion- movement of the foot such that the plantar surface is turned outward
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Supination/Pronation
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Movement of the forearm such that the palms face anteriorly or posteriorly
The palm is supinated in standard anatomical position-palms face anteriorly
Pronation-palms face posteriorly
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Agonist and Example
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Muscle primarily responsible for the movement. Example: Biceps brachii. Ex2: Deltoid
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Antagonist and Example
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Muscle which opposes the action of the agonist. Example: Triceps brachii. Ex2: Latissimus dorsi
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Synergist and Example
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Assists the agonist in making the action more efficient. Example: Brachialis. Ex2: Supraspinatus
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Fixator and Example
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Special synergists which help to prevent movement at muscle origin. Example: Trapezius
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Skeletal Muscle Functions (5)
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1. Skeletal movement (locomotion) 2. Posture and body position (facial expression) 3. Support 'soft tissues' (gut) 4. Guard entrances and exits to the body 5. Maintain body temperature
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Cellular and Subcellular Skeletal Muscle Structure
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1. Muscle cells are FIBERS
2. Typically MULTINUCLEATE
-arise from fusion or MYOBLASTS
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Skeletal muscle fiber structure has three functional levels of organization. Structure ONE.
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1. Plasma membrane=SARCOLEMMA. Surrounds cytoplasm=SARCOPLASM. TRANSVERSE TUBULES (T-tubules) arise from sarcolemma.
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Skeletal muscle fiber structure has three functional levels of organization. Structure TWO.
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2. Sarcoplasmic Recticulum (SMOOTH ER). Close in location to T-tubules. Surrounds myofibrils.
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Skeletal muscle fiber structure has three functional levels of organization. Structure THREE.
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3. Myofibrils. Longitudinal bundles or protein filaments=ACTIN & MYOSIN. Highly organized into repeating units=SARCOMERES.
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Sarcomeres
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Functional Unit of Contraction Elements
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Thin Filament
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Unit of contraction in sarcomere. Attached to Z line (Z disc). Composed of two helically arranged strands of ACTIN.
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Thick Filament
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Unit of contraction in the sarcomere. Spans the distance between thin filaments. Composed of a highly organized array of MYOSIN molecules. Myosin head has ATPase activity when bound to actin.
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Titin
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The third myofilament of striated muscle. Largest known protein. Stores energy during shortening and then assists in returning the sarcomere to its resting length
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Sliding Filament Model of Muscle Contraction (3)
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1. Myosin "heads" bind to actin to form a CROSSBRIDGE. 2. Conformational change, energized by ATP hydrolysis, causes thin filaments to SLIDE along thick filaments. 3. Myosin head groups release, form new crossbridges, and the sliding cycle repeats
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End result of filament model of muscle contraction
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Z-Lines move toward one another. Sarcomere length decreases. Muscle fiber shortens.
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As Thick/thin filament overlap increases...
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-I band width gets narrower
-A band widths remains constant
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Crossbridge Cycling
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Cycle is entered following exposure of myosin binding sites on the actin thin filament. (Regulatory role for Ca2+)
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Crossbridge Cycling Step One
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1. MYOSIN HEAD BINDS TO ACTIN FORMING A CROSSBRIDGE
a. ATP has already bound to the myosin head
b. This ATP is hydrolyzed by the unbound head, and the released energy results in a "cocking" of the head group.(ADP and Pi remain bound to the cocked head).
c. Myosin head group binds to ac…
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Crossbridge Cycling Step Two
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2. CROSSBRIDGE PIVOTS.
After binding, ADP and Pi are released and the head group 'pivots' back toward original orientation. When the ATP is hydrolyzed->release of energy trapped. The thin filament "slides" past the thick filament.
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Crossbridge Cycling Step Three
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3. CROSSBRIDGE DETACHES
ATP binds to the myosin head group -->breaking of crossbridge. The attaches head group-->RIGOR COMPLEX. The detached head group then hydrolyzes the ATP
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Sequence of Events of Excitation-Contraction Coupling
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1. Electrical signal transmitted from a motoneuron to a skeletal muscle fiber
2. Triggers a release of Ca2+ from SR
3. Ca2+ binds to a regulartory proteins of thin filament, thereby permitting crossbridges to form. (crossbridge cycling results in tension development) 4. Removal of Ca2+ …
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The 'Electrical Signal'
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Neuromuscular Transmission!
1. Activation of SKELETAL muscle is VOLUNTARY. Requires a signal from the central nervous system (CNS). Signal results in an electrical impulse along a motoneuron that arrives at the NEUROMUSCULAR JUNCTION
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The Neuromuscular Junction Key Points (4)
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1. Synaptic vesicles of NMJ contain NEUROTRANSMITTER, ACETYLCHOLINE (ACh)
2. ACh released from synaptic terminal, diffuses across synaptic cleft & binds to ACh receptor. 3. The activated ACh receptor permits Na+ to enter muscle at motor endplate, producing an ACTION POTENTIAL along sarco…
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Release of Ca2+ from the SR (5)
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1. AP runs along sarcolemma, continues into T-tubule
2. Triggers release of Ca2+ from SR
3. Ca 2+ binds to regulatory proteins on thin filament. MYOSIN BINDING SITE GETS EXPOSED.
5. Crossbridges form->tension generated
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Relaxation- Sequenstration of Ca2+
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1. When APs stop arriving at the NMJ, the 'trigger' to release Ca2+ from the SR stops.
2. Active Ca2+ transporters in the SR membrane pump Ca2+ back into the SR. CYTOPLASMIC[CA2+] DECREASES. 3. As [Ca]cyto falls, Ca comes off regulatory proteins- the myosin binding sites covered. 4. Cros…
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The molecular/cellular basis of the length-tension relationship
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Tension is proportional to cross-bridge function
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How do we know that formation of crossbridges is responsible for the generation of tension in skeletal muscle?
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Observation(s)
a. actin plus myosin hydrolyzs ATP
b. 'Skinned' muscle fibers retain sarcomere structure and shorten in the presence of ATP and Ca2+
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Hypothesis between tension by sarcomere and thick and thin filaments
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The level of tension generated by sarcomere is directly proportional to the overlap of thick and thin filaments.
Testing: Length-tension relationship
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Term: Neuromuscular Junction (NMJ)
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A synapse between the axon terminals of a motor neuron and the sarcolemma of a muscle fiber(cell)
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Term: Neurotransmitter
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One of a variety of molecules within axon terminals that are released into the synaptic cleft in response to a nerve impulse and that change the membrane potential of the postsynaptic neuron
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Term: Action potential (AP)
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An electrical signal that propagates along the membrane of a neuron or muscle fiber (cell); a rapid change in membrane potential that involves a depolarization followed by a repolarization
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Term: Acetylcholine (ACh)
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A neurotransmitter liberated by many peripheral nervous system neurons and some central nervous system neurons. It is excitatory at neuromuscular junctions
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Study Guide: Exam 3