6 The Muscular System Flashcards
What are the primary functions of muscles?
- Voluntary movement of the body (e.g., walking, jumping)
- Involuntary actions (e.g., reflexes, pupil adjustment, hair standing on end)
- Posture maintenance
- Heat production
- Internal organ movement (e.g., food through the digestive tract, bladder control)
Properties of muscles (4)
- excitability
- contractility
- extensibility
- elasticity
the capacity of a muscle to respond to a stimulus.
excitability
the ability of a muscle to shorten and generate a pulling force.
contractility
the property that allows a muscle to be stretched back to its original length.
extensibility
ability of a muscle to recoil to its original resting length after being stretched.
elasticity
muscle tissue:
- Under voluntary control
- Provides body movement
- Controlled by the nervous system
skeletal muscle tissue
muscle tissue:
- Involuntary (not under conscious control)
- Found in the walls of various internal organs
- Moves food and controls internal organs
smooth muscle tissue
muscle tissue:
- Involuntary (not under conscious control)
- Found in the heart (Works to pump blood)
cardiac muscle tissue
muscle fibers that contain more mitochondria and myoglobin, react slowly, resist fatigue, and are used in postural muscles that support the body’s stance.
red (slow) muscle fibers
muscle fibers that have lower myoglobin and mitochondria, react quickly, operate anaerobically, and provide quick bursts of power, useful in muscles that control fingers and eye movements.
white (fast) muscle fibers
blend traits of red and white fibers. They’re found in postural muscles like the calf, supporting both steady posture and rapid movements like running or jumping.
Intermediate muscle fibers
stimulate muscle fibers to contract, with each muscle fiber innervated by a branch of a neuron axon, forming a neuromuscular junction.
motor neurons
Muscles need high amounts of energy, so a __ supplies oxygen and nutrients and removes metabolic waste from muscle fibers.
dense capillary network
are the structural units in muscle fibers, containing actin and myosin protein filaments essential for contraction.
myofibrils
the functional unit of a myofibril, located between Z discs, where actin is anchored, and contraction occurs.
sarcomere
thick and consist of roughly 300 molecules, with each molecule resembling a “golf club” structure that enables it to bind to actin during muscle contraction.
myosin filament
bind to actin’s active sites, forming cross-bridges, and have ATPase activity, which releases energy to bend the hinge region during muscle contraction.
myosin head
Actin (thin) myofilaments consist of three major proteins: (3)
- fibrous (F) actin
- tropomyosin
- troponin
forms a double helix with myosin-binding sites on G actin monomers, allowing myosin to bind during contraction.
F actin
an elongated protein that winds along the groove of the F actin double helix, helping regulate muscle contraction by covering binding sites on actin.
Tropomyosin
What are the subunits of troponin and their functions? (3)
- Tn-A - binds to actin
- Tn-T - binds to tropomyosin
- Tn-C binds to calcium ions
crucial for muscle contraction control.
__ motor units control fine movements (e.g., fingers, eyes), while __ motor units control large weight-bearing muscles (e.g., thighs, hips).
- Small
- large
surrounds each myofibril, stores calcium (Ca++) when the muscle is relaxed, and releases it into the sarcoplasm when stimulated for contraction.
Sarcoplasmic reticulum (SR)
