Types of Muscles
Name the three basic types of muscle tissue found in the human body.
What is Skeletal, Cardiac and Smooth muscle
What is the primary function of skeletal muscles in body movement?
What is to produce voluntary movement by contracting and exerting force on bones and joints.
What is the basic contractile unit of a skeletal muscle fiber called?
What is the sarcomere.
Which tissue connects muscle to bone?
What is tendon.
What molecule serves as the immediate energy source for muscle contraction (the one that is directly used by myosin)?
What is adenosine triphosphate (ATP)
Which muscle type is voluntary and primarily attached to bones by tendons?
What is Skeletal muscle.
Give two examples of functions performed by smooth muscle in internal organs.
What are peristalsis in the gastrointestinal tract; control of vessel diameter (vasoconstriction/vasodilation); regulation of pupil size; contraction of the bladder.
Name the neurotransmitter released at the neuromuscular junction to trigger muscle contraction.
What is the Acetylcholine (ACh) and the energy source would be ATP.
Name the connective tissue layer that surrounds an entire muscle (the outermost sheath.
What is epimysium.
During intense exercise, muscles may operate anaerobically. Name the byproduct produced and its effect on muscle performance.
What is lactic acid (lactate) accumulation; associated with decreased pH locally and muscle fatigue (note: lactate itself can be used as fuel and is not solely the cause of long-term muscle soreness).
Which muscle tissue type is striated but involuntary and found only in the heart?
What is Cardiac Muscle.
How does cardiac muscle contribute to homeostasis?
What is pumping blood to maintain circulation, delivering oxygen/nutrients and removing wastes — supporting internal balance (homeostasis).
Outline the sequence of events at the neuromuscular junction from motor neuron action potential to muscle fiber excitation.
What is the motor neuron action potential → ACh released into synaptic cleft → ACh binds nicotinic receptors on motor end plate → muscle membrane depolarizes (end-plate potential) → action potential propagates along sarcolemma and T-tubules → sarcoplasmic reticulum releases Ca2+Ca2+.
Differentiate between origin and insertion with respect to muscle attachments
What is the origin is the less-movable (usually proximal) attachment; insertion is the more-movable (usually distal) attachment — during contraction the insertion moves toward the origin.
Explain how oxygen debt (excess post-exercise oxygen consumption) helps restore muscle physiology after strenuous activity.
What is oxygen debt allows replenishment of ATP and creatine phosphate stores, oxidation of lactate back to pyruvate and glucose (Cori cycle), and restoration of ionic gradients and body temperature to resting levels.
Describe one structural difference between smooth muscle cells and skeletal muscle fibers.
What is smooth muscle cells are spindle-shaped, single‑nucleated, and lack sarcomeric striations; skeletal fibers are long multinucleated cells with visible sarcomeres (striations).
Explain how skeletal muscles help maintain body temperature
What is muscle contractions generate heat (thermogenesis), especially through shivering and basal muscle tone
Define the sliding filament theory in two sentences and identify which proteins are primarily involved.
What is the sliding filament theory: actin (thin) filaments slide past myosin (thick) filaments powered by cross-bridge cycling; primary proteins: actin and myosin (with regulatory troponin/tropomyosin in striated muscle).
Identify one physiological feature that allows cardiac muscle cells to contract synchronously.
What are intercalated discs containing gap junctions and desmosomes allow electrical coupling and mechanical linkage for synchronous contraction.
Describe how the motor unit size and recruitment pattern differ when performing a delicate task versus lifting a heavy weight.
What are Delicate tasks: small motor units (few muscle fibers per motor neuron) are recruited first and allow fine control; heavy force: large motor units and greater recruitment, along with increased firing rates, produce more force (size principle)
Explain how the arrangement of actin and myosin differs between skeletal, cardiac, and smooth muscle and how this relates to striation patterns.
What is skeletal and cardiac muscle have repeating sarcomeres with orderly arrays of actin and myosin giving striations; smooth muscle has actin and myosin arranged more randomly and anchored to dense bodies, producing no striations.
Describe how antagonistic muscle pairs work together to produce controlled joint movement; include an example.
What are antagonistic pairs: one muscle (agonist) contracts while the antagonist relaxes to allow movement; e.g., biceps brachii (flexion) and triceps brachii (extension) at the elbow.
Describe excitation–contraction coupling, including the role of the sarcoplasmic reticulum and Ca2+Ca2+.
What is excitation–contraction coupling: action potential travels down T‑tubules → triggers sarcoplasmic reticulum to release Ca2+Ca2+ → Ca2+Ca2+ binds troponin causing tropomyosin shift → myosin-binding sites on actin exposed → cross-bridge cycling and contraction; Ca2+Ca2+ reuptake by SR leads to relaxation.
Compare and contrast fast-twitch (Type II) and slow-twitch (Type I) skeletal muscle fibers in terms of metabolism, fatigue resistance, and typical activities they support.
What are type I (slow-twitch): high mitochondrial density, oxidative metabolism, fatigue-resistant, used for endurance activities.
Type II (fast-twitch): more glycolytic, fewer mitochondria, fatigue faster, generate high force for short bursts (Type IIa more oxidative than IIb/IIx).
Provide a concise explanation of muscle hypertrophy at the cellular level (what changes occur in the muscle fiber with strength training).
What is hypertrophy: increase in muscle fiber cross-sectional area due to added myofibrils (increase in actin/myosin), increased sarcoplasm and connective tissue, and upregulation of protein synthesis pathways (e.g., mTOR signaling).