Physiology Class 7: Contraction of Skeletal Muscle

16 Questions

What is the primary function of the skeletal muscle?

Protect delicate tissues

Which type of muscle is part of the viscera and is involuntary?

Smooth muscle

What percentage of our body is composed of cardiac muscle?

10%

Which type of muscle is found only in the heart?

Cardiac muscle

What is the primary composition of sarcomeres in skeletal muscle?

Actin and myosin filaments

Where are the actin and myosin filaments located in a sarcomere?

In both I-bands and A-bands

What regulates the interaction between actin and myosin, preventing them from binding in the absence of calcium ions?

Troponin and tropomyosin proteins

During muscle contraction, what is released from the sarcoplasmic reticulum to allow actin and myosin to bind and form cross-bridges?

Calcium ions

What is the first source of ATP reconstitution but can only sustain maximal contraction for a limited time due to its stores?

Creatine phosphate system

Which type of metabolism occurs without the presence of oxygen, allowing for short bursts of high-intensity activity?

Anaerobic metabolism

What type of muscle contraction is characterized by muscle shortening while tension remains constant?

Isotonic

Which fiber type has high oxidative capacity and low force production?

Slow-twitch (Type I) fibers

What happens when muscle fibers are damaged?

Repair process

What is the effect of post-activation potentiation (PAP) on subsequent contractions?

Increased forceful contractions

Neuromuscular organization involves motor neurons innervating muscle fibers to control muscle contractions. What happens in smaller, faster-contracting muscles?

More motor neurons per muscle fiber

Muscular potential refers to the potential of action muscle. What is the duration of a potential action?

1-5 milliseconds

Study Notes

Eduardo Bailón welcomes students to the seventh class of physiology on his YouTube channel, Me Decide.
The topic of this class is the contraction of the skeletal muscle.
There are three main types of striped muscle: skeletal, smooth (visceral), and cardiac.
Skeletal muscle, also called striated muscle, is attached to the skeleton through tendons and is a voluntary muscle.
Smooth muscle, or visceral muscle, is part of the viscera and is an involuntary muscle, examples being the stomach and the inferior esophagus.
Cardiac muscle is found only in the heart and is an involuntary muscle.
Skeletal muscle makes up about 40% of our body, and smooth muscle and cardiac muscle each make up around 10%.
The skeletal muscle maintains form and position, protects delicate tissues, and generates heat.
The anatomy of the skeletal muscle includes its attachment to the skeleton through tendons, coverage by the epimysium, perimysium, and endomysium, and the presence of fascicles and motor units.
The histology of the skeletal muscle reveals that it is composed of sarcomeres, which are made up of actin and myosin filaments.
The actin filaments form a thin, mesh-like network, while the myosin filaments are thicker and form the "A-bands" in the sarcomere.
The myosin filaments have both a head and a tail, and the head contains the binding site for actin.
The interaction between actin and myosin is regulated by the troponin and tropomyosin proteins, which prevent actin and myosin from binding in the absence of calcium ions.
During muscle contraction, calcium ions are released from the sarcoplasmic reticulum, allowing actin and myosin to bind and form cross-bridges.
The energy for muscle contraction comes from the hydrolysis of ATP by myosin heads.
After contraction, the myosin heads release ADP and Pi, and ATP is resynthesized to allow for the next contraction.
Muscle relaxation occurs when calcium ions are pumped back into the sarcoplasmic reticulum by the sarcoplasmic reticulum calcium pump.- Muscular potential: Potential of action muscle lies between 80-90 mil volts, duration of potential action is 1-5 milliseconds, conduction velocity is 5 meters per second.
Role of transverse tubules: Facilitate contraction synchronization among muscle fibers, allowing for coordinated muscle contractions.
Creatine phosphate system: First source of ATP (adenosine triphosphate) reconstitution, but can only sustain maximal contraction for 5-8 seconds due to limited creatine phosphate stores.
Glucose metabolism (glycolysis): Second source of ATP reconstitution, breaking down glucose to pyruvic acid and lactic acid, releasing energy for ATP regeneration.
ATP regeneration: ATP is converted back to ADP (adenosine diphosphate) during muscle contraction, and ATP regeneration ensures muscle can maintain contraction by converting ADP back to ATP.
Anaerobic metabolism: Occurs without the presence of oxygen, allowing for short bursts of high-intensity activity, such as sprinting or weightlifting.
Aerobic metabolism: Requires oxygen and provides energy through the oxidation of nutrients, such as carbohydrates, fats, and proteins, for longer durations of activity, like endurance events.
Types of contractions: Two main types: isotonic, where muscle shortens while tension remains constant; and isometric, where muscle contracts without shortening.
Fibers types: Two primary types: slow-twitch, or Type I, fibers with high oxidative capacity and low force production; and fast-twitch, or Type II, fibers with low oxidative capacity and high force production.
Neuromuscular organization: Motor neurons innervate muscle fibers and control muscle contractions, with smaller, faster-contracting muscles having more motor neurons per muscle fiber and larger muscles having fewer motor units.
Summation of contractions: Increasing the number of contracting muscle fibers (summation of motor units) or increasing the frequency of contractions (summation of frequency) to produce a more forceful contraction.
Post-activation potentiation (PAP): Effect of muscle contraction facilitating subsequent contractions due to increased calcium availability in the sarcoplasm, allowing for more forceful contractions with less calcium input.
Calcium release: During muscle contraction, calcium is released from the sarcoplasmic reticulum and binds to troponin, initiating muscle contraction.
Heat production: Muscle heating increases muscle performance by improving calcium release from the sarcoplasmic reticulum and enhancing muscle fiber responsiveness.
Fiber damage: Intense muscle contractions can damage muscle fibers, leading to inflammation, repair, and eventual muscle growth.
Fitness and muscle growth: Regular resistance training, proper nutrition, and adequate rest promote muscle growth and improved muscle performance.

Delve into the intricacies of skeletal muscle contractions in this seventh class of physiology with Eduardo Bailón. Learn about the different types of striped muscles, muscle anatomy, histology, energy sources for muscle contraction, fiber types, and more.

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