MUSCLE STRUCTURE & MUSCLE CONTRACTION

1. MUSCLE STRUCTURE & MUSCLE CONTRACTION By: Dara Williams

2. Role: generates the mechanical forces and motion necessary for locomotion, manipulation of objects, circulation of blood, movement of food through the digestive tract, and various other processes. Muscular System:

3. TYPES OF MUSCLE: • Smooth Muscle- capable of slow, sustained contraction • Skeletal Muscle- produce movements by pulling on tendons • Cardiac Muscle- contracts rapidly

4. Asynchronous - indirect muscle contractions in which muscle contractions are not synchronized w/ signals from motor neurons

5. Muscle Contraction • When a muscle contracts, it pulls toward or away from the bone with which it articulates • Because muscle can only contract, they cannot pull; only push • Muscles act antagonistically with one another, which means that the movement produced by one can be reversed by another

6. Example • The bicep muscle, for example, flexes (bends) your arm whereas contraction of the triceps muscle extends it • Thus the biceps and triceps work antagonistically

7. Understanding Agonist & Antagonist • The muscle that contracts to produce a particular action is known as the agonist • The muscle that produces the opposite movement is the antagonist • When the agonist is contracting, the antagonist is relaxing. Generally, movements are accomplished by groups of muscles working together, so several agonists and several antagonists may take part in any action. Note that muscles that are in one movement may serve as antagonists in another. The superficial skeletal muscles of the human body are shown in (front & back)

8. In fact, vertebrate’s skeletal muscle is the most abundant tissue in the body. Its elongated cells, called muscle fibers, are organized in bundles wrapped by connective tissue. The biceps in your arm for example, consists of thousands of individual muscle fibers and their connective tissue coverings. • Each striated muscle fiber is a long cylindrical cell w/ many nuclei. The plasma membrane known as sarcolemma has multiple inward extensions that form a set of t tubules (transverse tubules). The cytoplasm of a muscle fiber is called the sarcoplasmic reticulum. • Myofibrils, which are threadlike structures, run lengthwise through the muscle fiber.

10. Myosin & Actin • They consist of even matter structures, the myofilaments, or simply filaments. There are two types, which are myosin and actin filaments • Myosin filaments are thick, consisting mainly of the protein myosin • The thin actin filaments consists mostly of the protein- actin; they also contain filaments consists mostly of the protein- actin; they also contain the protein tropomyosin and the troponin complex that regulate the actin filaments.

11. Important! • Myosin and actin filaments are organized into repeating units called sarcomeres, the basic units of muscle contraction. • Sarcomeres are joined at their ends by an interweaving of filaments called the Z line • The myosin head binds to an exposed active site on the actin filament, forming a cross bridge linking the myosin and actin filaments

13. Muscle Structure • Tendons - tough cords of connective tissue that anchors (pic of anchor) muscles to bone • PULL ON BONES • Creatine Phosphate- Backup energy compound that can be stockpiled

14. Dysfunctions • Chemical energy is stored in muscle fibers in glycogen, a large polysaccharide formed from hundreds of glucose molecules. • During a burst of strenuous exercise, the circulatory system cannot deliver enough oxygen to keep up with the demand of the rapidly metabolizing muscle cells, resulting in oxygen debt. • Accumulation of the waste product lactic acid also contributes to muscle fatigue.

15. In response to a single, brief electrical stimulus, skeletal muscle contracts with a single, quick contraction called a simple twitch. When a second stimulus is received before the first contraction is complete, the two twitches may add together, a process called summation. • Summation results in a smooth, sustained contraction called tetanus. • Even when you are not moving, your muscles are in a state of partial contraction known as muscle tone.

16. Differences in the Muscles • Smooth muscle is not attached to bones but instead forms tubes that squeeze like the muscle tissue in the body of the wall of the earthworm. • Cardiac muscle is not attached to bone either contracts and relaxes in alternating rhythm, propelling blood with each contraction.

17.  Fun Facts!  • Insect flight muscles contract more rapidly than any other known muscle( up to 1,000 contractions per second!) • The tongue is the strongest muscle in the body • Guess which muscle is the fastest: The group of muscles that work together to blink your eye. • A pound a muscle burns 75-100 calories just by “being”

18. THE END!