Muscle Arrangement

Fascicle Arrangement Muscle fibers in skeletal muscle form bundles called fascicles These single fibers are parallel to each other and end in a tendon However the arrangement of the muscle fascicles will determine the type of muscle, the strength of the muscle and the function of the muscle

Fascicle Arrangement In a parallel muscle the fascicles are parallel to the long axis of the muscle Most of the muscles in the human body are parallel muscles Some are broad and flat while others are long with a plump body The biceps brachii are good examples of this

Fascicle Arrangement Convergent muscles extend over a broad area and converge on a common attachment site The fascicles often fan out from their attachment site where they cover a large area The pectorals muscles are excellent examples of convergent muscles

Fascicle Arrangement Pennate muscles form a common angle with the tendon This means the tendon is straight, while all of the muscle fibers come off the tendon at a common angle These muscles commonly contain more fascicles than skeletal muscle and can create more tension when they contract

Fascicle Arrangement Circular muscles are fascicles that are contained around an opening These fascicles will decrease the size of the opening when they contract The fascicles will increase the size of the opening when they relax These are more commonly called sphincters

Skeletal Muscle Levers Skeletal muscles do not work in isolation Muscles work in groups in order to help perform tasks that are essential to the body For this we need to revisit physics…

Skeletal Muscle Levers A lever is a bar that pivots at a fixed point The fixed point that a lever pivots is called the fulcrum The lever moves based on the application of force in a give direction

Skeletal Muscle Levers A first class lever is seen when the fulcrum lies between the load and the applied load This can be seen in a child’s seesaw It can be seen in the muscles that control the head and neck

Skeletal Muscle Levers A second class lever is seen when the load is applied between the force and the fulcrum An example of this is the wheelbarrow In humans we can see this in our legs when we walk

Skeletal Muscle Levers A third class lever is seen when the force is seen between the load and the fulcrum This is seen in a baseball bat The fulcrum is the wrist, the force is the force of the bat and the load is the ball In humans this is the most common type of lever, seen in the arm

The Origin of the Story… Muscles have defined parts that dictate the job of the muscle Each part of the muscle is located in a specific part of the body and had a specific function These specific functions will be a great advantage to understanding the basics of the location of skeletal muscles

The Origin of the Story… In a muscle fiber, both ends of the myofibril are able to contract and move together You would think this would create a scenario where a skeletal muscle contracts evenly This is not the case Generally one end of the muscle is held in a fixed position During a contraction, the other end of the muscle will move to the opposite end

The Origin of the Story… The site where the end of the muscle attaches to in a fixed position is called the origin The site where the moveable end attaches to another structure is called the insertion Generally the origin is proximal to the insertion

Diagram

The Origin of the Story… The actual movement of the muscle is defined as the action The action of a muscle describes how it moves in the body and what end of the muscle manipulate the body The action is different for every muscle

Muscle Groups Muscles have the responsibility to move the skeleton around in the world However, one muscle cannot move the body in all different directions This is because one contraction can only shorten one muscle To move the body in all different directions you need a complex series of muscles

Activity! https://www.google.com/webhp?s ourceid=chrome- instant&ion=1&espv=2&ie=UTF- 8#q=qwop%20unblocked Pull out your chromebooks and go to the following link This is a great simulator that shows how hard it is to make muscles work together People who get over 5m can write their names and distances on the board High Scores

Muscle Groups Since each muscle group has different muscles that have different jobs Each job in a muscle group is defined and has a specific purpose A muscle agonist is a prime mover Agonist is the primary muscle that produces the desired movement in a joint

Muscle Groups An antagonist is a muscle whose action opposes that of the particular agonist These muscles contract and produce the opposite movement of the agonist A good example of this is the triceps brachii Their contractions produce extension in the elbow This is opposite of the biceps brachii

Muscle Groups When a synergist muscle contracts it is helping move the agonist These muscles are vitally important to moving the agonist Many muscle groups contain multiple synergists The hips and knees contain large amounts of strong synergists

Muscle Groups Some muscle groups are designed to prevent the movement of joints This can create a stable origin for other muscles These muscles are often synergists These muscles are called fixators