Muscle Fibers M.Rich, RN

Bell Work 1. What type of muscle attaches to bone & allows for movement? 2. What type of muscles are involuntary? 3. What muscle would straighten your leg at the knee and keep it straight when you stand? 4. Muscles only PULL or PUSH. Which one? 5. Muscles that shorten as they contract are called? 6. Muscles that elongate as they contract are called?

Standard 8) Review the gross and cellular anatomy and physiology of the musculoskeletal, nervous, and cardiovascular systems. 9) Identify the two types of muscle fibers and their subtypes, slow twitch and fast twitch. Relate the concepts of histochemistry, immunocytochemistry, and physiologic contraction times to the performance of athletes in various sports. Evaluate the role genetics and training play in muscle fiber adaptations. From this research, generate an informational artifact to share with athletes or clients as part of an exercise/training program

Objectives Differentiate ways muscles can work Analyze Muscle Fibers Good Review Video: https://www.youtube.com/watch?v=3xTjn wo2S2A

Muscles can work as Flexors – contracting to bend our joints. Extensors – contracting to straighten joints. Prime movers (agonists) – contracting to start a movement. Antagonists – relaxing to allow movement to take place. Fixators – contracting to give the working muscles a firm base. Synergists – stabilizing the area around the prime mover and fine tuning our movement.

Flexion and Extension Flexion and extension are movements that occur in the sagittal plane. They refer to increasing and decreasing the angle between two body parts: Flexion refers to a movement that decreases the angle between two body parts. Flexion at the elbow is decreasing the angle between the ulna and the humerus. When the knee flexes, the ankle moves closer to the buttock, and the angle between the femur and tibia gets smaller. Unit III

Extension Extension refers to a movement that increases the angle between two body parts. Extension at the elbow is increasing the angle between the ulna and the humerus. Extension of the knee straightens the lower limb. Unit III

Joint Movement Terms FLEXION vs. EXTENSION hyperextend flexion flexion dorsiflexion plantar flexion neutral Unit III

Antagonist and agonist muscles Often occur in pairs, called antagonistic pairs. As one muscle contracts, the other relaxes. An example of an antagonistic pair is the biceps and triceps; to contract - the triceps relaxes while the biceps contracts to lift the arm

Synergist Synergist: The synergist in a movement is the muscle(s) that stabilizes a joint around which movement is occurring, which in turn helps the agonist function effectively.  Synergist muscles also help to create the movement. Synergist muscles also help to create the movement. In the bicep curl the synergist muscles are the brachioradialis and brachialis which assist the biceps to create the movement and stabilize the elbow joint.

Fixator The fixator in a movement is the muscle(s) that stabilizes the origin of the agonist and the joint that the origin spans (moves over) in order to help the agonist function most effectively. In the bicep curl this would be the rotator cuff muscles, the 'guardians of the shoulder joint'. The majority of fixator muscles are found working around the hip and shoulder joints.

HOW ARE MUSCLES ATTACHED TO BONES? Muscles are usually attached to 2 or more different bones. The muscle fibers end in a strong, white flexible cord, called a TENDON. At the bone, the fibers of the tendon are embedded in the PERIOSTIUM of the bone. This anchors the tendon strongly and spreads the force of the Contraction REMEMBER: Tendons join muscle to bone. Ligaments join bone to bone.

MUSCLE SPEED and TONE Our muscles are made up cells called muscle fibers. These tiny threadlike fibers are packed together in bundles. Muscles contract (shorten) because the fibers do. Muscle fibers don’t all contract together. The number contracting at any one time depends on how much force is needed

Muscle Fiber Types Slow Twitch and Fast Twitch Every muscle contains a mixture of fast and slow twitch muscle fibers. BUT: • The mixture is different in different muscles e.g. the gastrocnemius contains a lot of fast twitch fibers so standing on your toes is tiring The mixture is different for different people. Some distance runners have 80% slow twitch fibers while some power lifters have 80% fast twitch

Muscle Fiber Types

FAST TWITCH Tire very quickly. Do not have a good oxygen supply. Are stronger than slow-twitch fibers. Contract very quickly. Are used when we need fast, powerful movements. Are used only in high intensity exercise. Are used in anaerobic activities. Can you think of sports that use fast-twitch Fibers? Fast Twitch: powerful bursts of movements like sprinting.

Fast Twitch Fast-twitch muscle depletes with age considerably more than slow-twitch, so increasing muscle power is less feasible later in life

SLOW TWITCH Have a very good oxygen supply. • Work for a long time without tiring. • Are not as strong as fast-twitch fibers • Take longer to contract. • Are used in all types of exercise. • Are used especially in aerobic activities. Can you think of sports that use slow-twitch Fibers? Example: help enable long-endurance feats such as distance running

MUSCLE FIBERS and SPORT If we jog slowly, only a few of our slow-twitch fibers contract to move our legs. When we increase our speed we use more slow-twitch fibers. As we run faster our fast-twitch fibers also start to contract to help out. More and more will start to contract as we run even faster. At top speed all of our fast-twitch and slow twitch fibers will be working. MUSCLE CHANGES AND SPORT Muscle hypertrophy – the muscle increases is size Muscle atrophy – muscle decreases in size.

FAST/SLOW TWITCH https://www.youtube.com/watch?v=3xTjnwo2S2A

WHAT HAPPENS AS WE EXERCISE? There is an increased flow of blood to the working muscles. • Muscles take up more oxygen from the blood. • The muscles contract more often and more quickly. • More of the muscle fibers contract. • There is a rise in the temperature of the muscle. • Our stores of Adenosine Triphosphate (ATP) and Creatine Phosphate (CP) in the muscles are used up. • Waste products such as Carbon Dioxide and Lactic Acid build up in the muscles. • These waste products lead to tiredness and cramp. • Stores of muscle glucose are used up. • Our ability to carry on may be affected. • Overuse of muscles can lead to soreness and strains.

Muscle Contraction and ATP The source of energy that keeps everything going is called ATP. Adenosine triphosphate (ATP) is the biochemical way to store and use energy. Recall Cellular Respiration requires ATP.

MUSCLE TONE Even when a muscle is relaxed, a small number of fibers are contracted – enough to keep the muscle taut but not enough to cause movement. This partial state of contraction is called Muscle Tone Without muscle tone you would not be able to stand up straight! To maintain muscle tone without getting tired, groups of muscles take it in turns to contact. They work in relays Poor muscle tone leads to poor posture. Exercise improves muscle tone – it makes the fibers thicker so they contract more strongly

Research Questions 1. What are the types of Fast Twitch fibers? Define and make sure you mention anaerobic and aerobic exercise in your definitions. 2. Give two exercise examples of Slow Twitch and Fast Twitch 3. Define histochemistry, immunocytochemistry as it relates to muscles. Explain how it is used examine muscle cells. 4. Vocabulary terms to define (as it relates to muscles): Epimysium, Fasciculi, Perimysium, Myofibrils, Sacromere, Actin, Myocin, ATP, Tropomyosin, Troponin, Calcium 5. What is the sliding filament theory? Define and explain.

Resources https://www.verywell.com/fast-and-slow-twitch-muscle-fibers-3120094 https://courses.lumenlearning.com/boundless-ap/chapter/introduction-to-skeletal-muscle/ http://muscle.ucsd.edu/musintro/histochem.shtml http://www.immunohistochemistry.us/what-is-immunohistochemistry.html https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4083319/ http://www.sportsinjuryclinic.net/anatomy/human-muscles/muscle-contractions http://www.teachpe.com/anatomy/structure_skeletal_muscle.php http://www.teachpe.com/anatomy/sliding_filament.php