Physiology Review The SARCOMERE is the functional unit of the muscle. A sarcomere is found between two Z lines.

Neural Stimulation Phase 1 of Muscle Physiology: The process starts when the muscle cell is depolarized A neuron (nerve cell) releases acetylcholine at the neuromuscular junction. This produces an action potential over the entire sarcolemma. (This is called an action potential because if there is enough Ach released, it has the potential to cause contraction of the muscle) Sodium/Potassium pumps cannot work when Ach is on the receptors of muscle cells…chaos ensues!

Muscle Contraction Phase 2 of Muscle Physiology: The process starts when Ach docks on the sarcolemma. Ach causes Na+ ions to rush INTO the cell and K+ ions to rush OUT of the cell—remember the pumps aren’t working when Ach is docked on the sarcolemma! This influx of Na+ ions causes the Sarcoplasmic Reticulum to release it’s Ca+2 into the muscle cell.

Muscle Contraction Calcium from the SR binds with troponin. The release of Calcium ions from the sacroplasmic reticulum starts the Sliding Process. Calcium from the SR binds with troponin. Tropomyosin is pulled off the binding sites of actin This allows the myosin cross bridges to bind to actin and slide the actin toward the center of the cell.

http://people.eku.edu/ritchisong/crossbridge3.gif

SLIDING FILAMENT MECHANISM Neither the Myosin nor the actin filaments change in length. They change their position with one another. The actin slides between the myosin.

The muscle cell is made up of Contractile proteins and Regulatory proteins

Contractile Proteins Myosin is the main, thick protein in the sarcomere. It has cross bridges for attaching to the Actin protein and is found in center of cell. Actin is the main, thin protein in the sarcomere. Each actin molecule has a binding site that can attach with a Myosin cross bridge and is found attached to the z-lines.

Regulatory Proteins Tropomyosin and Troponin are regulatory proteins and control the muscle contraction process. They either allow or block actin-myosin interaction depending on their configuration.

fig.cox.miami.edu/.../150/neuro/tropomyosin.jpg

TROPOMYOSIN Tropomyosin covers the actin binding sites. This prevents the union of actin with myosin cross bridges in a relaxed muscle cell.

TROPONIN Troponin has three binding sites: one binds to Tropomyosin, one to Actin, and one to Ca+ ions. When calcium combines with troponin, tropomyosin slips away from its blocking position between actin and myosin. With this change actin and myosin can interact and muscle contraction can occur.

http://3dotstudio.com/contract.gif

www.octc.kctcs.edu

Relaxation Phase 3 of Muscle Physiology: The process starts when the muscle cell is repolarized A neuron (nerve cell) stops releasing acetylcholine at the neuromuscular junction. If there is no more Ach, the Na+/K+ pumps can do their work again and will start re-establishing the status quo of more Na+ outside the cell and more K+ inside the cell

Relaxation Once there is less Na+ inside the cell, the sarcoplasmic reticulum will resorb the Ca+2 that it released. Ca+2 will release from the troponin, and tropomyosin will “spring” back up to block the actin/myosin binding site once again. Contraction will stop The contraction of ANTAGONISTIC muscle fibers are necessary to pull the sarcomere to it’s original length.

Name this muscle

Muscle?

Muscle?

Test Information… 57 points total (min of 34.5) 20 Anatomy ID—real people, pictures and microscope slides Some anatomy on Physiology portion Body movements Draw a line drawing of sarcomere

Notecardable items… Fill in the blank (with words provided) of body movements (4) One short answer has choices…choose the question you can answer the MOST completely. Mitochondria’s role in contraction vs blood supply

Notecardable items… Steroid question—what are they, what effects do they have on the human body, what debate is there as to effectiveness? How do muscles attach inside the body? To each other? To bones?

Short Answer Questions (notecardable…) Explain the protein alignment within a sarcomere. Draw a diagram as well…

Short Answer Questions (notecardable…) Physiology of muscle cell—broken into 5 questions Three phases of function of MC Function of neuromuscular junction Stimulation in detail (# in order) Contraction in detail (# in order) Relaxation in detail (# in order)

Short Answer Questions (notecardable…) Antagonistic/Synergistic as it relates to function of muscles Difference between strains, sprains and contusions Three factors contributing to muscle aging Case study