Exercise Physiology Quiz

The human body has three types of muscle: skeletal, smooth, and cardiac. Skeletal muscle is responsible for voluntary movement, smooth muscle controls involuntary movements in organs, and cardiac muscle is found only in the heart.

Skeletal muscle has two main types: slow-twitch fibers and fast-twitch fibers. Slow-twitch fibers contract slowly but fatigue resistant, while fast-twitch fibers contract quickly but fatigue quickly.

The smallest contractile unit of muscle is the sarcomere. It is the basic functional unit of a muscle fiber and consists of overlapping thin filaments (actin) and thick filaments (myosin) arranged in a specific pattern, which allows muscle contraction.

Muscle excitability refers to the ability of muscle tissue to respond to stimuli. A motor neuron sends action potentials to the muscle, triggering a contraction.

Muscle contractility is the ability of muscle tissue to shorten forcefully. This happens due to the sliding filament theory, where myosin filaments pull on actin filaments, causing the sarcomere to shorten.

Muscle extensibility is the ability of muscle to stretch beyond its resting length. This allows muscles to lengthen and relax after a contraction.

Muscle elasticity is the ability of muscle tissue to recoil back to its resting length after being stretched. This helps muscles maintain their form and prevents them from staying stretched out.

Muscles have several important functions: producing movement, maintaining posture, stabilizing joints, and producing heat. Muscles generate heat as a byproduct of cellular respiration.

A motor unit is the functional unit of muscle. It consists of a motor neuron (nerve cell) and all the muscle fibers it innervates. Each motor neuron controls a group of muscle fibers.

Somatic motor neurons of the Peripheral Nervous System (PNS) carry neural messages from the spinal cord to muscles. These messages are what initiate muscle contractions.

The principle that states that motor units are recruited in order of their size, with smaller motor units being recruited first.

Muscle fibers that are slow-twitch, fatigue-resistant, and primarily used for endurance activities.

Muscle fibers that are fast-twitch, moderately fatigue-resistant, and can be used for both endurance and power activities.

Muscle fibers that are fast-twitch, easily fatigued, and primarily used for explosive power activities.

An indirect test that assesses muscle fatigue by measuring the decline in power output during a specific exercise.

Muscle fibers are categorized into three types: slow oxidative (SO), fast oxidative glycolytic (FOG), and fast glycolytic (FG). Each type has distinct properties like contraction speed, force production, and fatigue resistance.

SO fibers are slow-twitch, fatigue-resistant, and utilize oxidative metabolism for energy. They have high capillary density and mitochondrial density, enabling efficient oxygen utilization for sustained contractions.

FOG fibers are fast-twitch, moderately resistant to fatigue, and utilize both oxidative and glycolytic metabolism for energy. They have a medium capillary and mitochondrial density, balancing endurance and power.

FG fibers are fast-twitch, easily fatiguable, and primarily utilize anaerobic glycolysis for energy. They have low capillary and mitochondrial density, favoring rapid power production.

The number of muscle fibers innervated by a single motor neuron. Low ratios in SO fibers allow for fine motor control, like eye movements, while high ratios in FG fibers provide for gross motor control, like biceps or gastrocnemius movements.

Muscle fiber type can be determined directly through biopsy and staining techniques. Indirectly, it can be estimated using various exercise tests that measure muscle performance and fatigue.

This experiment surgically switched the locations of two muscle masses before nerve outgrowth. The outgrowing axons detoured to innervate the correct muscles, indicating that muscles signal nerves to determine fiber type.

This experiment reattached a fast motor nerve to a slow-contracting muscle. Over time, the muscle switched characteristics, demonstrating nerves can influence muscle fiber type.

The specialized synapse where a motor neuron communicates with a muscle fiber.

The neurotransmitter released at the neuromuscular junction, triggering muscle contraction.

Tiny sacs within the motor neuron that store and release acetylcholine.

The region of the muscle fiber that contains receptors for acetylcholine.

The process of the muscle fiber's membrane potential becoming less negative, which initiates a muscle contraction.

The principle that a muscle fiber will contract completely or not at all, depending on whether the stimulus reaches the threshold.

The time period during which a muscle fiber cannot be stimulated to contract again.

The time period during which a muscle fiber can be stimulated to contract again but requires a stronger stimulus than usual.

The series of events that link the arrival of a nerve impulse at the neuromuscular junction to muscle contraction.

Essential for muscle contraction, as they trigger the sliding filament mechanism.

An action potential (AP) traveling down the t-tubule triggers the release of calcium ions (Ca2+) from the sarcoplasmic reticulum. This Ca2+ then binds to troponin, causing a conformational change that shifts tropomyosin, exposing the active sites on actin.

Actin and myosin are the proteins that power muscle contraction. Myosin, the thick filament, has binding sites that attach to the active sites on actin, the thin filament. This binding allows myosin to pull on actin, causing the sarcomere to shorten, and the muscle to contract.

The depolarization of the triad region (a region of the muscle where the t-tubule meets the sarcoplasmic reticulum) triggers the release of Ca2+ from the sarcoplasmic reticulum.

An isometric contraction occurs when muscle tension increases, but the muscle length remains the same. The force generated by the muscle is equal to the opposing force.

An isotonic contraction involves muscle tension remaining constant while the muscle length changes. The muscle force overcomes the opposing force, resulting in movement.

A concentric contraction is an isotonic contraction where the muscle shortens as it contracts. The force generated by the muscle is greater than the opposing force.

An eccentric contraction is an isotonic contraction where the muscle lengthens as it contracts. The force generated by the muscle is less than the opposing force.

An isokinetic contraction is a contraction where the speed of contraction remains constant, regardless of the force generated by the muscle.