SEHS Test Sliding Filament Theory Flashcards
(7 cards)
Explain the process of the sliding filament theory
The sliding filament theory describes how muscles contract to create movement. It involves two types of protein filaments within muscle fibers: actin (thin filaments) and myosin (thick filaments). During contraction, myosin heads bind to the actin filaments and pull them past each other, which shortens the muscle. This pulling action is powered by energy from ATP (adenosine triphosphate). When the muscle relaxes, the filaments slide back to their original positions. This mechanism enables muscles to generate force and control movement efficiently.
Discuss the cross bridge cycle
The cross-bridge cycle is the continuous process that enables muscle contraction at the molecular level. It starts when myosin heads attach to specific binding sites on the actin filaments, forming a cross-bridge. The myosin heads then pivot, pulling the actin filaments toward the center of the sarcomere in a movement called the power stroke. After this, ATP binds to the myosin heads, causing them to detach from the actin. The ATP is then broken down into ADP and phosphate, which re-energizes the myosin heads and prepares them for the next cycle. This cycle repeats as long as calcium ions and ATP are available, allowing the muscle to contract continuously.
What are the roles of troponin and tropomyosin?
Troponin and tropomyosin are regulatory proteins that control muscle contraction. Tropomyosin covers the binding sites on the actin filaments, preventing myosin heads from attaching when the muscle is relaxed. Troponin, which is attached to tropomyosin, acts as a regulatory switch. When calcium ions bind to troponin, it changes shape and moves tropomyosin away from the binding sites on actin. This exposes the sites and allows myosin heads to bind to actin, initiating the contraction process. Without the regulation by troponin and tropomyosin, muscles would not be able to contract properly or maintain relaxation when required.
Describe how motor units are innervated to create muscle forces
A motor unit is made up of one motor neuron and all the muscle fibers it controls. When the motor neuron sends an electrical signal, called an action potential, it travels down to the muscle fibers. This signal causes the release of neurotransmitters at the neuromuscular junction, which then triggers the muscle fibers to contract. The number of motor units activated determines the strength of the muscle contraction — activating more motor units produces greater force. Smaller motor units control precise, fine movements, while larger motor units are responsible for stronger, more powerful contractions. This system enables the body to adjust muscle force accurately based on the required activity.
What are synergists?
Synergists are muscles that assist the main muscle, known as the agonist, during a movement. They help stabilize joints and enhance the efficiency of the movement by supporting the agonist’s action. For example, during a bicep curl, the brachialis and brachioradialis act as synergists to aid the biceps in contracting. Synergists also prevent unwanted movements by stabilizing nearby joints. Without them, movements would be less smooth and controlled. They play a crucial role in coordinating complex muscle actions to ensure effective and precise movement.
What are fixators (stabilizers)?
Fixators, also known as stabilizers, are muscles that hold a joint or body part steady while another movement occurs nearby. They prevent unwanted movement, allowing the agonist muscle to work more effectively and safely. For example, during a bicep curl, the muscles around the shoulder act as fixators to keep the arm stable. Fixators also help maintain balance and posture during complex movements. Without fixators, movements could become unsteady and less controlled. They are essential for smooth, coordinated muscle function.
Explain the differences between elevation and depression
Elevation is the upward movement of a body part toward the head, such as when you shrug your shoulders and they lift up. Depression is the opposite movement, where a body part moves downward, away from the head. For example, lowering your shoulders back down after a shrug. These movements mainly occur at joints like the shoulders and the jaw. Understanding elevation and depression is important for accurately describing body movements during activities and exercises.
