Muscular system (Chp 8) Flashcards
(25 cards)
Can muscles push to create movement?
No, muscles cannot push. They work by contracting, which shortens the muscle and pulls on the bone it’s attached to via tendons. For a limb to return to its original position, an opposing muscle (antagonist) must contract to pull it back. Muscles always work in agonist-antagonist pairs to allow controlled movement in both directions.
How do muscles work in pairs to produce movement?
Skeletal muscles function in antagonistic pairs. When one muscle (the agonist) contracts to produce movement, the opposing muscle (the antagonist) relaxes.
For example, to bend the elbow, the biceps brachii contracts while the triceps brachii relaxes. To extend the elbow, the triceps contracts and the biceps relaxes.
What are the three types of muscle tissue, and how do they differ?
Skeletal muscle – Voluntary, striated, multinucleated, attached to bones for movement. Controlled by the somatic nervous system.
Cardiac muscle – Involuntary, striated, branched cells with one nucleus and intercalated discs for coordinated contraction. Found only in the heart. Controlled by the autonomic nervous system.
Smooth muscle – Involuntary, non-striated, spindle-shaped cells with one nucleus. Found in walls of hollow organs (e.g., intestines, blood vessels). Also controlled by the autonomic nervous system.
What is the structural organization of a muscle from largest to smallest?
Muscle – Entire organ made up of bundles of fascicles.
Muscle fascicle – A bundle of muscle fibers.
Muscle fiber (cell) – Long, cylindrical, multinucleated cell.
Myofibril – Threadlike structures inside a muscle fiber made of sarcomeres.
Myofilaments – The smallest structures: thin filaments (actin) and thick filaments (myosin).
How do actin and myosin interact during muscle contraction?
Myosin (thick filament) heads bind to actin (thin filament) at binding sites exposed by calcium. The myosin heads pivot, pulling actin toward the center of the sarcomere. This shortens the sarcomere and contracts the muscle. ATP provides the energy needed for the myosin heads to detach and re-cock for another cycle.
What roles do calcium ions and ATP play in muscle contraction?
Calcium (Ca²⁺) binds to troponin, shifting tropomyosin to expose actin’s binding sites.
ATP binds to the myosin head, allowing it to detach from actin. ATP is then hydrolyzed to ADP + Pi, which resets the myosin head for another power stroke.
What are the energy sources for muscle contraction, and in what order are they used?
Stored ATP – Immediately available, lasts a few seconds.
Creatine phosphate – Donates phosphate to ADP to regenerate ATP quickly.
Anaerobic glycolysis – Breaks down glucose without oxygen, producing lactic acid.
Aerobic respiration – Uses oxygen to produce ATP from glucose, fatty acids, or amino acids. This is the most efficient and long-lasting source.
What are the differences between fast-twitch and slow-twitch muscle fibers?
Fast-twitch (Type II): Contract quickly with great force, fatigue rapidly, rely mostly on anaerobic respiration, have fewer mitochondria and low myoglobin. Used for sprinting and explosive movements.
Slow-twitch (Type I): Contract slowly with less force but resist fatigue, rely on aerobic respiration, have many mitochondria and high myoglobin (darker color). Used for endurance activities like long-distance running.
sarcollema
muscle fibre membrane
sarcoplasm
inner materials surrounding fibers
sarcoplasmic reticulum
used for the transport of calcium ions
myofibrils
individual parralell muscle fibres within the sarcoplasm s
what defines the skeletal muscle? (striated, shape of cell, # of nuclei per cell, voluntary or involuntary, location in the body)
of nuclei per cell:
Striated: Yes
shape of cell: tubular and branched
# of nuclei per cell:
in voluntary or voluntary: voluntary
location: attached to the bone
what defines the smooth muscle? (striated, shape of cell, # of nuclei per cell, voluntary or involuntary, location in the body)
of nuclei per cell
Striated: no
shape of cell:
# of nuclei per cell:
in voluntary or voluntary:
location:
what defines the cardiac muscle? (striated, shape of cell, # of nuclei per cell, voluntary or involuntary, location in the body)
Striated: yes
shape of cell:
# of nuclei per cell:
in voluntary or voluntary:
location:
what two muscle groups are striated
cardiac and skeletal
actin characteristics
thick or thin: thin
number of strands: two
does it have other proteins associated with it: yes troponin and tropomyosin
longer or shorter: shorter
head or no head: no head
myosin characteristics
thick or thin: thick
number of strands: two
does it have other proteins associated with it: no
longer or shorter: longer
head or no head: head
what moves first when the myofilament retracts
the heads of the myosin
________ is pulled a long with myosin heads as they flex
Actin
myosin heads ________ one after another and myosin walks a long actin
flex
Actin is pulled a long with myosin heads as they flex
myosin heads flex one after another and myosin walks a long actin
this reaction requires 1 _________ molecule
ATP
what are the 4 main functions of muscles
Movement – muscles pull on bones to create motion.
Posture Maintenance – help keep you upright.
Joint Stabilization – muscles and tendons support joint structure.
Heat Production – generate body heat during contraction.
fast twitch muscle definition
speed of contraction: fast
fatigue: quickley
activity: sprinting/powerlifting (short Bursts of energy
mitochondria: fewer
color: pale (white) less myoglobin
