Chapter 10: Muscular System (Gross Anatomy)/Chapter 9: Muscular System (Histology and Physiology)

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142 Terms

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Tendons
attach muscle to bone
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Aponeurosis
A broad, flat tendon
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Origin/head of a muscle
muscle end attached to the more stationary spot
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Insertion of a muscle
muscle end attached to the bone that moves when the muscle contracts
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Belly of a muscle
the largest portion, between the origin and insertion
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Agonist
muscle that causes an action
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Antagonist
muscle that acts in opposition to agonist
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When you are doing the flexion motion of a biceps curl, what muscle is the agonist? What muscle is the antagonist?
Biceps are the agonist, triceps are the antagonist
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Synergists
muscles that work together
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Examples of synergists muscles
biceps brachii & brachialis = elbow flexion
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Quadrangular muscle shape
knowt flashcard image
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Rhomboidal muscle shape
knowt flashcard image
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Fusiform muscle shape
knowt flashcard image
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Trapezium muscle shape
knowt flashcard image
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Triangular muscle shape
knowt flashcard image
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Digastric muscle shape
knowt flashcard image
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Bicipital muscle shape
knowt flashcard image
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Muscles are named according to: (7 things) LSSOONF
1. Location: pectoralis, gluteus, brachial.
2. Size: maximus, minimus, longus, brevis.
3. Shape: deltoid, quadratus, teres.
4. Orientation: rectus.
5. Origin and insertion: sternocleidomastoid, brachioradialis.
6. Number of heads: biceps, triceps.
7. Function: abductor, adductor, masseter (chewer).
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Muscular system functions (7 things)
1. Body movement.
2. Maintenance of posture.
3. Respiration.
4. Production of body heat.
5. Communication.
6. Constriction of organs and vessels.
7. Heartbeat.
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Contractility
muscle shortens with force
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Excitability
respond to a stimulus
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Extensibility
muscle can be stretched beyond its normal resting length and still contract
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Elasticity
recoil to original resting length after stretched
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Comparison of skeletal, smooth, and cardiac muscle
knowt flashcard image
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Each skeletal muscle =
a complete organ
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Muscle cells are associated with
connective tissue, blood vessels, & nerves
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Skeletal muscle fibers develop from
myoblasts
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Number of skeletal muscle fibers are
"constant" from birth.
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Which of these is not a major functional characteristic of muscle?
A. Contractility
B. Elasticity
C. Excitability
D. Secretability
D. Secretability
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Which of these is true of skeletal muscle?
A. Spindle-shaped cells.
B. Under involuntary control.
C. Forms the walls of hollow organs.
D. Many peripherally located nuclei per muscle cell.
D. Many peripherally located nuclei per muscle cell.
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What is a group of muscle fibers called?
a fasciculus
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4 layers of connective tissues coverings of skeletal muscle (SEPE)
Starts with the muscle fiber, then goes:
1. Sarcolemma
2. Endomysium
3. Perimysium
4. Epimysium
Starts with the muscle fiber, then goes:
1. Sarcolemma
2. Endomysium
3. Perimysium
4. Epimysium
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Sarcolemma
surrounds the muscle cell (example: plasma membrane of muscle fiber)
surrounds the muscle cell (example: plasma membrane of muscle fiber)
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Endomysium
Also around muscle cell
Also around muscle cell
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Perimysium
Denser C.T. surrounding fasciculus
Denser C.T. surrounding fasciculus
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Epimysium
C.T. that surrounds the muscle (many fasciculi make up muscle)
C.T. that surrounds the muscle (many fasciculi make up muscle)
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Fascia
connective tissue sheet in muscles that is continuous with tendons and periosteum
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Functions of fascia (4 things)
1. Forms layer under the skin.
2. Holds muscles together - separates them into functional groups.
3. Allows free movements of muscles
4. Carries nerves (motor neurons, sensory neurons), blood vessels, and lymphatics
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Motor neurons
stimulate muscle fibers to contract
stimulate muscle fibers to contract
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Structure of motor neurons
Neuron cell bodies are in brain/spinal cord, then branched axons attach to skeletal muscle fibers
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Each muscle fiber is
innervated
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Muscle fiber anatomy
Nuclei is inside sarcolemma, and the muscle cell is packed with myofibrils within the sarcoplasm
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Sarcoplasm
muscle cell cytoplasm
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Myofibrils
groups of myofilaments
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2 types of myofibrils in a muscle fiber
1. Actin myofilaments
2. Myosin myofilaments
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Actin myofilaments
THIN threadlike, protein threads (letter R in picture)
THIN threadlike, protein threads (letter R in picture)
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Myosin myofilaments
THICK threadlike, protein threads
THICK threadlike, protein threads
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Sarcomeres (Z disk to Z disk)
basic structural & functional repeating unit of skeletal muscle (because it is the smallest portion of skeletal muscle capable of contracting) that is the attachment site for actin myofilaments
basic structural & functional repeating unit of skeletal muscle (because it is the smallest portion of skeletal muscle capable of contracting) that is the attachment site for actin myofilaments
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Z disk
knowt flashcard image
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F actin
a fibrous protein made of a long chain of G actin molecules strung together and twisted into a helix
a fibrous protein made of a long chain of G actin molecules strung together and twisted into a helix
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Tropomyosin
a long protein that covers active binding sites on actin to prevent myosin from binding
a long protein that covers active binding sites on actin to prevent myosin from binding
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Troponin
a globular protein complex that has 3 subunits that bind to the actin, tropomyosin, and Ca++
a globular protein complex that has 3 subunits that bind to the actin, tropomyosin, and Ca++
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What does the tropomyosin/troponin complex do?
regulates active sites on G actin and myosin
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How do myosin heads work? (2 steps)
1. Binds to active sites on actin - forms cross-bridges
2. Breaks down ATP (with ATPase Enzyme) releasing energy used to bend hinge region
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Muscle fiber striated appearance is cause by (4 things) IAM and H
1. I bands - ends of myosin
2. A bands - length of myosin
3. M line - filaments holding myosin in place
4. H zone - only myosin, no overlapping actin
1. I bands - ends of myosin
2. A bands - length of myosin
3. M line - filaments holding myosin in place
4. H zone - only myosin, no overlapping actin
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Which myofilament is the thick one?
A. Actin
B. Myosin
C. Troponin
D. Tropomyosin
B. Myosin
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Does actin or myosin change length when the muscle contracts?
No
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Relaxation: sarcomeres lengthen by _________ muscles.
antagonistic
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Sarcomere shortening
During contraction, Z disks are brought closer together as the actin myofilaments at each end of the sarcomere slide past the myosin toward each other. The H zones (yellow) and the I bands (blue) narrow. In a fully contracted muscle, the ends of the actin myofilaments overlap at the center of the sarcomere and the H zone disappears.
During contraction, Z disks are brought closer together as the actin myofilaments at each end of the sarcomere slide past the myosin toward each other. The H zones (yellow) and the I bands (blue) narrow. In a fully contracted muscle, the ends of the actin myofilaments overlap at the center of the sarcomere and the H zone disappears.
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Physiology of skeletal muscle fibers includes: (3 things)
1. ion channels
2. action potentials
3. neuromuscular junction (NMJ)
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Action Potential Phases
1. Membrane at resting potential (R.P.) then voltage hits absolute threshold because of a stimulus
2. Depolarization
3. Repolarization
4. Hyperpolarization
5. Back to R.P.
1. Membrane at resting potential (R.P.) then voltage hits absolute threshold because of a stimulus
2. Depolarization
3. Repolarization
4. Hyperpolarization
5. Back to R.P.
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During the depolarization phase of an action potential, the permeability of the plasma membrane to
A. Na+ decreases
B. K+ increases
C. Ca++ decreases
D. Na+ increases
D. Na+ increases
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Which direction does Na+ travel during depolarization?
A. Into the cell.
B. Out of the cell.
C. It doesn't go much of anywhere.
D. It goes to Hulsey Wellness Center.
A. Into the cell.
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Synapse of a NMJ
axon terminal resting in a depression of the sarcolemma
axon terminal resting in a depression of the sarcolemma
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Another name for postsynaptic membrane
motor end-plate
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What does acetylcholine do?
stimulates/inhibits action potentials in the postsynaptic membrane
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Acetylcholinesterase
Degrading enzyme in synaptic cleft that prevents accumulation of acetylcholine
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Acetylcholinesterase is an important molecule in the neuromuscular junction because it
A. Stimulates receptors on the presynaptic terminal.
B. Stimulates receptors on the postsynaptic membrane
C. Breaks down acetylcholine.
D. Causes the release of Ca++ from the sarcoplasmic reticulum.
C. Breaks down acetylcholine.
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Excitation-contraction coupling
The Mechanism where an action potential causes contraction of a muscle fiber
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Excitation-contraction coupling involves (5 things)
1. Sarcolemma
2. Transverse (T) tubules: depression in the sarcolemma
3. Terminal cisternae of the Sarcoplasmic reticulum (smooth ER)
4. Ca2+
5. Troponin
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Relaxation process (3 things)
1. Ca2+ moves back into sarcoplasmic reticulum by active transport, which requires energy. (Diffusion of Ca2+ out of Sarcoplasmic Reticulum is rapid, but active transport of Ca2+ back into the Sarcoplasmic Reticulum is slow in comparison.)
2. Ca2+ moves away from troponin-tropomyosin complex.
3. Tropomyosin complex re-establishes its position and blocks binding sites on actin again.
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What is the neuromuscular junction?
the axon terminal and the area of the sarcolemma they innervate
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Given these events for muscle contraction:
1. Sarcoplasmic reticulum releases Ca++
2 Sarcoplasmic reticulum takes up Ca++
3. Ca++ ions diffuse into the cytoplasm where the myofibrils are located.
Choose the correct order.
1, 3, 2
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What happens if something destroys (or blocks) the acetylcholine receptor site in the neuromuscular junction?
myasthenia gravis
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Myasthenia gravis
an autoimmune disease where muscles have flaccid paralysis (are weak) because of the destruction of the ACh receptors by antibodies
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Muscle twitch phases
1. latent/lag
2. contraction
3. relaxation
1. latent/lag
2. contraction
3. relaxation
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Motor unit
a single motor neuron and all muscle fibers innervated by it.
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Summation
increasing the force of contraction of the muscle fibers within the muscle
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Recruitment
increasing the number of muscle fibers contracting
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Multiple motor unit summation
increased force of contraction
because more motor units are
Stimulated
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the amount of tension is determined by
the amount of motor units responding
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Muscle tetany
sustained muscle contraction
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As the frequency of action potentials increase, the frequency of contraction increases until
tetanus is achieved
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Incomplete tetanus
muscle fibers partially relax between contractions
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Complete tetanus
no relaxation between contractions, with very rapid AP's
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Isotonic muscle contraction
tension is constant, and has change in length (ex: upper limb movement, fingers typing)
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Isometric muscle contraction
tension increases, and no change in length (ex: postural muscles of body)
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Most muscle contractions are not strictly isotonic or isometric.
True, for example walking
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Concentric muscle contraction
(Isotonic) Tension is great enough to overcome opposing resistance and muscle shortens (ex: loaded backpack off the floor - as muscle shortens tension increases
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Eccentric muscle contraction
(Isotonic) Tension is maintained but opposing resistance lengthens the muscle (ex: lower a heavy weight)
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Muscle tone
constant tension by muscles over a long time that keeps back and lower limbs straight, head upright, abdomen flat
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Choose the correct statement.
A. Isometric: change in length and tension.
B. Isometric: no change in length but the tension increases.
C. Isotonic: no change in length but the tension increases.
D. Isotonic: change in length and tension.
B. Isometric: no change in length but the tension increases.
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Fatigue
decreased capacity to work and reduced efficiency of performance
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3 types of fatigue
1. Psychological
2. Muscular
3. Synaptic
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Psychological fatigue
Perceives can't/but can! (Involves CNS, most common, and depends on emotional state of individual.)
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Muscular fatigue
results from ATP depletion. (ex: marathon runners, swimmers,
2nd most common
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Synaptic fatigue
occurs in NMJ due to lack of acetylcholine (occurs in cases of extreme exertion, rarely occurs)
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Rigor Mortis
muscles become rigid several hours after death
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Why does Rigor Mortis happen?
Low levels of ATP and the breakdown of the SR Membrane cause Ca2+ to leak into sarcoplasm, which causes the myosin heads to attach to actin cross bridges. Then because of a low ATP concentration (shortly after death ATP production stops) myosin can't let go.
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When does Rigor Mortis end?
when tissues deteriorate