muscular system exam final time making ts fr

What is excitability?

The ability of muscle tissue to receive and respond to a stimulus (nervous signal).

What is contractility?

The ability to shorten forcibly when adequately stimulated.

What is extensibility?

The ability to be stretched or extended without damage.

What is elasticity?

The ability of a muscle fiber to recoil and resume its resting length.

What allows muscle to contract? (Main drivers)

Interaction between actin and myosin filaments, triggered by Calcium and powered by ATP.

What is a tendon?

Connective tissue that attaches muscle to bone.

What is the whole muscle?

The highest level of organization, covered by the epimysium.

What is a fascicle?

A bundle of muscle fibers within the whole muscle.

What is a muscle fiber?

An individual muscle cell; where the sarcolemma and SR are found.

What is a myofibril?

Rod-like contractile elements that occupy most of the muscle cell volume.

What are myofilaments?

The macromolecular level consisting of individual Actin and Myosin proteins.

What level is responsible for muscle contraction?

The Sarcomere level (the functional unit located within myofibrils).

What is the sliding filament model?

The theory that thin filaments slide past thick filaments to shorten the sarcomere.

What is the sliding filament model for?

To explain how muscle tension is generated and how the muscle physically shortens.

What structures are involved in the sliding filament model?

Actin (thin), Myosin (thick), Troponin, and Tropomyosin.

What are the steps of the sliding filament model?

1. Ca2+ binds Troponin 2. Tropomyosin moves 3. Myosin binds Actin 4. Power stroke 5. ATP detaches Myosin.

What is the nervous system role in contraction?

The motor neuron sends an electrical signal to the muscle via the neurotransmitter Acetylcholine (ACh).

What is the role of ACh receptors?

Found on the sarcolemma; they receive ACh to start the muscle's electrical impulse.

What is the role of T-tubules?

Found deep in the cell; they carry the electrical impulse from the surface to the interior.

What is the role of the SR (Sarcoplasmic Reticulum)?

Found surrounding myofibrils; its role is to store and release Calcium (Ca2+).

What is the role of myosin and actin?

Found at the myofilament level; Myosin pulls Actin to create physical movement.

What is the role of Calcium (Ca2+)?

The "trigger" that binds to troponin to expose myosin-binding sites on actin.

Where is Calcium stored/found?

Stored in the Sarcoplasmic Reticulum (SR) until an impulse arrives.

What is the role of Sodium (Na+) and Potassium (K+)?

They create the action potential (electrical signal) across the sarcolemma.

Where are Na+ and K+ found?

Found in the extracellular fluid and sarcoplasm (around the sarcolemma).

What is the role of Magnesium (Mg2+)?

Required for ATP binding/hydrolysis and aids in the relaxation phase.

What is the cross-bridge cycle?

The repeating sequence of events that causes thick and thin filaments to slide.

What is the cross-bridge cycle for?

To generate mechanical force and tension within the muscle fiber.

What structures and materials are involved in the cross-bridge cycle?

Actin, Myosin, Calcium ions, and ATP energy.

What are the 4 steps of the cross-bridge cycle?

1. Formation (Binding), 2. Power Stroke (Pulling), 3. Detachment, 4. Reactivation (Cocking).

What is a motor unit?

One motor neuron plus all the individual muscle fibers it controls.

How is a motor unit involved in muscle contraction?

It is the unit of recruitment; small units for fine control, large units for heavy force.

How does recruitment affect force?

Activating more motor units increases the total number of fibers contracting, increasing force.

How does stimulation frequency affect force?

Rapid nerve impulses lead to "summation," where contractions add up to reach Tetanus.

How does initial muscle length affect force?

Maximum force is produced when actin and myosin have optimal overlap before starting.

Energy from Creatine Phosphate (Products & Use)

Product: 1 ATP. Best for: Short, 100% explosive power (0-15 seconds).

Energy from Anaerobic Glycolysis (Products & Use)

Product: 2 ATP + Lactic Acid. Best for: High-intensity bursts (30-60 seconds).

Energy from Aerobic Respiration (Products & Use)

Product: ~32 ATP + CO2 + Water. Best for: Prolonged, moderate activity (minutes to hours).

What are the components of the holistic approach?

Nutrition (protein/electrolytes), Hydration, Sleep, and Progressive Overload exercise.

What is the effect of daily use and exercise?

Causes micro-tears leading to Hypertrophy (increased fiber size and mitochondria).

What is the effect of lack of movement?

Leads to Atrophy (muscle wasting), where mass is lost and may be replaced by fat.

What happens to muscle tissue over time after age 30?

Sarcopenia (gradual loss of muscle mass and strength).

What can we do about Sarcopenia?

Engage in regular resistance and weight-bearing exercise to preserve mass.

Resistance exercise examples and benefits

Ex: Weightlifting, sprints. Benefits: Increases fiber size, power, and bone density.

Endurance exercise examples and benefits

Ex: Running, swimming. Benefits: Increases capillaries, mitochondria, and stamina.

What is muscle fatigue and its general cause?

Inability to contract despite signal; caused by ion imbalances (K+) or phosphate buildup.

What is NOT a cause of fatigue that was previously blamed?

Lactic acid is not the cause; it is a fuel source used by other tissues.

What are the recovery needs of explosive exercise?

Needs time to restore Creatine Phosphate stores and for the Nervous System (CNS) to reset.

What are the recovery needs of sustained exercise?

Needs rehydration and the replenishment of Glycogen (carb) stores in muscles/liver.