The Mighty Muscle!

Muscles Provide Us With…. Movement Of the body parts Support Connections between muscles and bones help to hold the body in and upright position. Heat Production Muscles produce heat as a by-product of movement. Helps maintain normal body temperature.

Connective Tissue of Muscle The most abundant connective tissue of muscle is the fascia. Fascia is connective tissue Can surround the muscle Can occupy the space between muscle and skin Muscle contains other connective tissue – discussed on later slide.

Muscle Tissue Types Smooth Skeletal Cardiac Found in the organs Responsible for organ movement and contraction Peristalsis of the GI tract Skeletal Attached to bones Responsible for body movements Cardiac Responsible for heart contraction

Striated or Not? Muscle Fibers - Skeletal Striated Striations Nucleus

Cardiac Muscle Striated

Smooth No striations

Voluntary vs Involuntary Smooth and Cardiac Your brain controls the contract of the muscle Voluntary Skeletal muscle You can control the muscle movements http://health.howstuffworks.com/adam-200005.htm Video on muscle types

Structure of Skeletal Muscle Muscles are made up of muscle cells and connective tissue Most muscles attach at two places and crosses a joint. Attachment at the more stationary end is the origin. Attachment at the moveable end is the insertion.

Structure of Skeletal Muscle

Epimysium Connective tissue that surrounds the entire muscle. Deep fascia

Perimysium Sheath of connective tissue that holds individual muscle fibers together. These fiber bundles are called fascicles

Endomysium Layer of connective tissue that surrounds each individual muscle fiber.

Muscle Fibers Muscle fibers contract to give movement to the body. Each muscle fibers contains myofibrils These are thin fibers that actually do the contraction of the muscle.

Blood vessels surround the bundles.

Skeletal Muscles Skeletal muscles can be broken down into groups based upon: The type of movement they portray. Based on the type of joint that the muscle works. Skeletal muscles can’t make themselves longer….but they can contract, or make themselves shorter Muscles generally work in pairs. One contracts, and in doing so stretches the other, and reverses its effects on the joint. Example: When you contract your bicep, in return, the tricep extends. As you contract one muscle the other one extends.

Action of muscles can be grouped as Flexors Flexors bend at the joint, decreasing the interior angle of the joint = Bicep Extensors Opposites of flexors, extensors unbend at the joint, increasing the interior angle = tricep Abductors Abductors take away from the body, like lifting the arm to the side – spreading your fingers or toes Adductors Adductors, the opposites of abductors, move toward the body – lowering arm when raised to the side.

Movement of Muscles Internal look at the muscle fiber. See Handout.

Specifically…..Brachial Plexus The brachial plexus is a network of nerves that originate near the neck and shoulder. These nerves begin at the spinal cord in the neck and control the hand, wrist, elbow, and shoulder These are both motor and sensory neurons.

Muscle Fibers and Nerves Nerves can stimulate muscle fibers Inside the fibers, there is a negative charge When stimulated, the resting membrane potential changes Channels open in the membrane allowing sodium ions to rush in creating an action potential

Muscle Fibers and Nerves The nerves that stimulate muscles are called motor neurons and originate from the spinal cord. When the action potential is created, the muscle fiber contracts. How does this happen? http://www.sumanasinc.com/webcontent/animations/content/muscle.html video

Contraction of Muscles Remember, the individual muscle fibers are called myofibril Myofibrils are the function unit of the muscle Special names given to its structures sarcolemma for plasma membrane sarcoplasmic reticulum for endoplasmic reticulum sarcosomes for mitochondria sarcoplasm for cytoplasm

Contraction of Muscles Each myofibril is made up of arrays of parallel protein filaments. Myosin (protein) = thick filaments Actin (protein) = thin filaments Also contain a small amount of troponin tropomyosin. These fibers make up a sarcomere

Where they overlap is called the A band In the myofibril, there are alternating thick and filaments that overlap. Where they overlap is called the A band This band appears dark when looking at the striations within a muscle H zone is where there is no overlap of thin filaments I bands are where only thin filaments occur Appears as the lighter band when looking at the striations within the muscle Z lines are where the different sarcomeres meet up

http://highered. mcgraw-hill http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__sarcomere_contraction.html

Sliding Filament Theory/Mechanism Before a stimulus is received, a muscle is at rest. Calcium ions are being stored within the sarcoplasmic reticulum ATP molecules are chemically bound to thin filaments (actin) The thin filament has all three proteins (actin, troponin) and tropomyosin) attached The fiber is ready to contract if a stimulus from a nerve were to occur.

The sarcoplasmic reticulum receives a stimulus from a motor neuron It becomes more permeable to calcium ions. The calcium is released into the sarcomere. Once calcium is in the sarcomere, it binds to troponin in the thin filaments. Actin and troponin undergo a shape change. This exposes binding sites on thin filaments. When these sites are exposed, portions of thick filaments called cross bridges bind forming a connection between thin and thick filaments.

ATP is broken down into ADP and phosphate and energy. When these cross bridges occur, calcium causes a breakdown of ATP that is bound to the thick filaments. ATP is ready to be broken down…. ATP is broken down into ADP and phosphate and energy. The energy that is released is used to move the cross bridges and some is released as heat. Movement of the cross bridges causes the thin filaments to be drawn toward the center of the sarcomere. When this action is completed, another ATP molecule binds to myosin causing the thick filament’s cross bridge to break from the attachment with the thin filament.

Once the thick filament position is restored, the cross bridge reforms its attachment to a binding site on the thin filament. This cycle occurs again and again resulting in a continual movement of thin filaments toward the center of the sarcomere causing the sarcomere to shorten. This gives muscle contraction! http://www.vetmed.wsu.edu/VAn308/muscleanimation.htm

Rigor Mortis!

What Happens? When you die, ATP becomes unavailable. The cross bridges that are formed (because the ATP is already attached) when you die are not released and the body is “frozen” in a certain position. Conversion to ADP does not occur. Rigor mortis can happen quickly after death. It lasts form 12-24 hours after death (depending on external conditions) Release occurs due to the break down of tissues in the body.