A & P I Guided notes 4

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Where does muscle contraction occur..?

between thick and thin filaments

What happens when Ca+2 binds to troponin in the thick filament..?

it exposes the active site

What happens once the active site is exposed..?

the myosin heads bind to the active site

What are the myosin head now called (after the binding)

cross bridges

What do the cross bridges then do..?

Pivot

What does pivoting use to make energy..?

ATP

Why does pivoting use ATP energy..?

to pull thin filaments toward the center of the sacromere

What do the myosin heads do after pivoting..?

they detach and reload with ATP

The pivoting cycle repeats as long as..?

• Nerve signals continue

• ATP energy is available

What is ATP?

a molecule made up of adenosine and three phosphate groups

What does the squiggly line represent..?

high energy bond

What happens when the third phosphate is broken off..?

energy is release

What is the (ATP reaction) be written as..?

ATP—> ADP—>Pi + energy

What happens during sustained muscle contraction..?

muscles use enormous amounts of ATP

What is the Sliding Filament Model..?

describes how sarcomeres contract

According to the Sliding Filament Model..?

• the filament slide between thick filaments toward the M line

• The wide of the A zone stays the same—> thick filaments dont move

• The Z lines move closer together

What does Neural Stimulation in the Sarcolemma result in..?

excitation contracting coupling

What is excitation contracting coupling..?

• coupling - excitation and contracction are connected

• excitation - action potential in muscle fiber

• contraction - sarcomeres shorten via sliding filament model

Excitation leads to contraction because these two processes are..?

connected

Where is the location where the are coupled up..?

the triad

What does the triad do..?

• recieves electrical signal

• releases calcium

The cisternae of the SR releases Ca+2 which..?

• triggers the interaction of thick and thin filaments

• The interaction of filaments sliding and pivoting consumes ATP and produces tension

What is tension..?

is a pulling force; objects are pulled toward a source of tension

The point of muscle contraction is to produce..?

this pulling force

What is the first step of muscle contraction..?

Step 1: calcium release (sarcoplasm is release near zones of overlap)

What is the second step of muscle contraction..?

• exposure of active sites (ca binds to the troponin which changes shape)

• the tropomyosin moves, uncovering the active sites

What is the third step of muscle contractons..?

Formation of cross bridges ( myosin binds to the active sites)

What is the forth step of muscle contractions..?

Pivoting of the myosin heads (this action uses ATP energy)

What is the fifth step of muscle contractions..?

Cross bridge dettaches (They dettach when new ATP binds to the myosin head)

What is the last step of muscle contrctions..?

the reactivation of myosin

• ATP splits into ADP and Pi

• releasing energy

• The myosin is recharged and ready for the next round of the cycle when active sites are uncovered again

What is rigor mortis..?

stiffness of death

Rigor mortis is latin for..?

fixed muscular contraaction fterr death

After death the body can no longer make..?

ATP

What happens if the body does not have ATP..?

• ION pumps cant pump back ATP

• Calcium diffuses out into the sarcoplasm

• clacium causes active sites to be exposed

• myosin heads attach and pibot

• myosin becomes stuck because there is not ATP to cause detachment