Chapter 6 (Exam 2) Flashcards
(51 cards)
What are the 4 shared traits of all muscle tissue types?
Excitability, Contractility, Extensibility, Elasticity
These properties allow muscle tissues to play essential roles in posture, movement, circulation, digestion, and more.
What are the unique characteristics of skeletal muscle?
Voluntary control, Striated appearance, Multinucleated, Attached to bones via tendons, Fast contractions
Examples include biceps brachii, hamstrings, and deltoid.
What are the unique characteristics of cardiac muscle?
Involuntary, Striated, Single nucleus, Branched fibers with intercalated discs, Found only in the heart
Cardiac muscle contracts rhythmically and is self-excitable.
What are the unique characteristics of smooth muscle?
Involuntary, Non-striated, Spindle-shaped cells, Single nucleus, Located in walls of hollow organs
Contracts slowly and rhythmically, controlled by the autonomic nervous system and hormones.
How do antagonistic and synergistic muscles function?
Antagonistic muscles perform opposite movements; Synergistic muscles assist the prime mover
Example: Biceps (flexes elbow) vs. Triceps (extends elbow); Brachialis helps biceps during elbow flexion.
What is the structural organization of skeletal muscle?
Myofilaments → Myofibrils → Muscle fibers → Fascicles → Whole muscle
Surrounded by connective tissue layers: Endomysium, Perimysium, Epimysium.
What is the sarcomere and its key components?
The basic contractile unit of a muscle fiber located between Z-lines; Key bands/zones: A-band, I-band, H-zone, M-line
During contraction, Z-lines get closer, sarcomere shortens, and I-band & H-zone narrow.
Describe the sliding filament mechanism.
Calcium binds troponin → Tropomyosin shifts → Myosin heads bind to actin → Power stroke occurs → ATP detaches myosin
This cycle repeats as long as calcium and ATP are present.
How does a motor neuron activate a muscle fiber?
An action potential travels down a motor neuron; ACh released at the neuromuscular junction; Signal travels down T-tubules; Calcium released
Calcium initiates the contraction cycle.
What is the role of calcium in contraction?
Ca²⁺ binds to troponin, shifts tropomyosin, exposes actin’s binding sites
Myosin can now bind to actin; Calcium is pumped back into the SR for relaxation.
What are actin, myosin, troponin, and tropomyosin?
Actin: Thin filament; Myosin: Thick filament; Troponin: Binds calcium; Tropomyosin: Blocks actin’s binding sites
Troponin moves tropomyosin off actin during contraction.
What is the role of transverse (T) tubules?
Extensions of the sarcolemma that carry electrical signals deep into the muscle fiber
They trigger calcium release from the SR across the fiber.
What is ATP’s role in the sliding filament model?
Detaches myosin from actin, Hydrolyzes to reset myosin head, Powers calcium pumps in the SR
Without ATP, muscles go into rigor mortis.
What is the function of acetylcholine (ACh)?
A neurotransmitter released by motor neurons; Binds to receptors on muscle membrane
Acetylcholinesterase breaks down ACh to end stimulation.
What is Duchenne Muscular Dystrophy (DMD)?
A severe X-linked genetic disorder primarily affecting boys; Caused by absence of dystrophin
Leads to muscle fiber damage and symptoms like muscle weakness and loss of mobility.
What is a motor unit?
One motor neuron and all the muscle fibers it controls; Fewer fibers = fine control; More fibers = gross movement
Recruitment increases contraction strength.
What is the difference between a muscle twitch and tetanus?
Twitch: brief, single contraction; Tetanus: sustained, maximal contraction from rapid stimulation
Holding a weight continuously requires tetanus.
What is summation in muscle contraction?
Occurs when a second stimulus arrives before the first twitch is over; Creates a stronger force
This leads to tetanus if stimuli are rapid.
What are the four energy sources for muscle contraction?
- Stored ATP
- Creatine phosphate
- Anaerobic respiration
- Aerobic respiration
Each provides energy for different durations and intensities.
What is oxygen debt and how is it corrected?
Extra oxygen required after exercise to restore muscle cells; Used to replenish ATP and creatine phosphate, convert lactic acid
Reload oxygen onto myoglobin.
Compare slow-twitch and fast-twitch muscle fibers.
- Slow-twitch (Type I): Aerobic, fatigue-resistant, suited for endurance
- Fast-twitch (Type II): Anaerobic, rapid contractions, fatigue quickly
Examples: long-distance running vs. sprinting.
What roles do different muscle types play in exercise and endurance?
- Skeletal muscle: Main driver of movement
- Cardiac muscle: Becomes more efficient with aerobic training
- Smooth muscle: Regulates blood flow and digestion
Not directly involved in skeletal movement.
What are the benefits of aerobic exercise?
- Increases mitochondria and capillary density
- Improves cardiovascular and respiratory efficiency
- Reduces resting heart rate
Examples: running, swimming, cycling.
What are the benefits of resistance exercise?
- Increases muscle mass
- Improves bone density
- Enhances metabolic rate
Examples: weightlifting, push-ups.
