Physiology Review

(ppt modified from http://www.recreation.ucsb.edu/ess/ess40/chap8.htm)

The SARCOMERE

is the functional unit of the muscle.

A sarcomere is found

between two Z lines.

The Muscle Fiber Is Composed of Special Contractile Proteins

• Myosin is the main, thick structural protein in the sarcomere. It has cross bridges for attaching to the Actin protein.

• Actin is the main, thin structural protein in the sarcomere. Each actin molecule has a binding site that can attach with a Myosin cross bridge.

• Actin and myosin are contractile proteins.

Tropomyosin and Troponin Are Regulatory Proteins.

These regulatory proteins control the muscle contraction process.

•They either allow or block actin-myosin interaction depending on their configuration.

TROPOMYOSIN•Tropomyosin covers the actin binding sites.

•This prevents the union of actin with myosin cross bridges.

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.

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

Sliding Filament Mechanism

•The myosin cross bridges can bind to the actin.

•After binding the thin (actin) filaments are pulled toward the center of the sarcomere.

•This is known as the Sliding Filament Mechanism.

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

SLIDING FILAMENT MECHANISM

•Neither the thick nor thin filaments change in length. They change their position with one another.

•The actin slides closer together between the thick filaments.

• http://3dotstudio.com/contract.gif

• The myosin cross bridges pull the thin actin filaments inward.

• A single power stroke pulls the actin inward only a small percentage of the total distance.

• Complete shortening occurs by repeated cycles of the power stroke.

• The link between myosin and actin is broken at the end of one cross bridge cycle. A cross bridge returns to its original position and can connect to the next actin molecule position, pulling the actin filament further.

www.octc.kctcs.edu

Muscle contraction

• The process starts when the muscle cell is depolarized

• A neuron sends action potentials to muscle fibers.

• This neuron releases acetylcholine at the neuromuscular junction.

• This produces an action potential over the entire muscle cell membrane.– Sodium/Potassium pumps are not working when Ach

is on the receptors of muscle cells…chaos ensues!

The Release of Calcium Ions from the sacroplasmic reticulum starts the Sliding Process.

• Calcium from the SR binds with troponin.

• By this event, tropomyosin is pulled off the binding sites of actin

• This allows the myosin cross bridges to bind to actin and slide this protein.

Test Information…• 60 points total

–20 Anatomy ID—real people, pictures and microscope slides

–Some anatomy on Physiology portion• Body movements• Draw a line drawing of sarcomere

Name this muscle

Muscle?

Muscle?

Notecardable items…

• Fill in the blank (with words provided) of body movements (4)

• Two short answers have choices…choose the question you can answer the MOST completely. – A diagnostic vs. muscle connections– Mitochondria’s role in contraction vs

blood supply

Short Answer Questions(notecardable…)

• Explain the protein alignment within a sarcomere. Draw a diagram as well…

•Physiology of muscle cell—broken into 5 questions–Three phases of function of MC–Function of neuromuscular junction

–Stimulation in detail–Contraction in detail–Mechanism for lengthening

Short Answer Questions(notecardable…)

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

• Steroid question—what have you learned about the pros/cons/debate?