17 Questions
What is the result of the action potential from nerves connecting to the muscles at the motor endplate?
Release of Ca+2 from the Sarcoplasmic Reticulum
What is the primary function of the motor unit?
To transmit the action potential from the nerve to the muscle fibers
What is the term for the process by which the excitation of the muscle cell is coupled to contraction of the muscle?
Excitation-contraction coupling
Which of the following is NOT a characteristic of smooth muscle?
It has tropomyosin
What is the term for the muscle contraction that causes a bending movement?
Flexion
What is the term for the muscles that contract to provide the main force to move or rotate a bone through its joint?
Agonists
What is the primary factor that determines the force generated by a muscle?
The number of cross-bridges formed between actin and myosin
What type of muscle contraction occurs when the force applied to the muscle exceeds the force produced by the muscle?
Lengthening contraction
What is the relationship between muscle contraction speed and muscle power?
The slower the contraction, the more power is generated
What is the effect of muscle length on muscle contraction?
Muscle length affects the actin-myosin overlap and the force generated
What is an example of an isometric contraction?
Pushing with all your might on a wall
What is the primary function of muscles in the musculoskeletal system?
To convert chemical energy to mechanical energy
Which of the following is NOT a type of muscle fiber?
Epithelial
What is the structure that attaches to the thin filaments in a myofibril?
Z-disc
What is the result of the hydrolysis of ATP to ADP during muscle contraction?
The myosin head is cocked back
What is the functional unit of muscle contraction, comprising a motor neuron and the muscle fibers it innervates?
Motor unit
What is the term for the area between two consecutive Z-discs in a myofibril?
Sarcomere
Study Notes
Musculoskeletal System
- The musculoskeletal system is composed of bones, joints, muscles, cartilage, tendons, ligaments, and other connective tissue.
- Its primary functions are to support the body, allow motion, and protect internal organs.
Muscles
- The purpose of muscles is to move the body and convert chemical energy into mechanical energy (ATP to force).
- Muscle fibers contain contractile proteins: actin and myosin.
- There are three types of muscles: skeletal, cardiac, and smooth.
Muscle Organization
- Individual muscles are made up of muscle bundles.
- Muscle bundles are made up of muscle fibers.
- Muscle fibers are made up of myofibrils.
- Myofibrils are organized into sarcomeres, the contractile unit of the muscle.
Sliding Filament Model
- The myosin head binds ATP and detaches from actin.
- Hydrolysis of ATP to ADP results in a conformational change in the myosin head.
- The myosin head binds to actin, forming a cross-bridge.
- The myosin head releases ADP and Pi, resulting in another conformational change, called the power stroke.
Motor Unit
- A motor unit is a motor neuron and all of the muscle fibers that connect to it.
- An action potential from nerves connects to the muscles at the motor endplate.
- This causes the sarcoplasmic reticulum to release Ca+2, which binds with troponin, exposing actin binding sites.
Muscle Contractions
- Muscles are arranged in pairs, with antagonist muscles causing opposite movements.
- Agonist muscles contract to provide the main force to move or rotate a bone through its joint.
- Muscle length affects the actin-myosin overlap and the force that can be generated.
- Maximizing the number of cross-bridges formed maximizes muscle power (force).
- Muscle contraction speed relates to muscle power (force).
- Isometric contraction occurs when the muscle does not change length.
- Lengthening contraction occurs when the force applied to the muscle exceeds the force produced by the muscle.
Learn about the process of muscle contraction, including the role of myofibrils, cross-bridge cycling, and excitation-contraction coupling. Understand how action potential from nerves triggers muscle contraction. Test your knowledge on muscle physiology!
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