Muscles -> Excitation Contraction Coupling

Action potentials in sarcolemma can lead to _______ of muscle fiber

contraction

What is the linking of electrical and mechanical components of muscle contraction?

Excitation contraction coupling

Where does excitation contraction coupling occur?

Triad

Calcium is stored at high concentrations where?

Sarcoplasmic reticulum

Action potential occurs where?

Sarcolemma

Action potential occurs in sarcolemma and continues along the length of muscle fiber into where?

T-tubules

Action potentials cause what in the terminal cisternae to open?

Voltage-gated calcium channels

What diffuses into sarcoplasm surrounding myofibrils?

Ca2+

Ca2+ binds with what?

Troponin

When Ca2+ binds with troponin, causes what to happens?

Tropomyosin to move

When Ca2+ binds with troponin, causing tropomyosin to move, what is exposed?

Active sites on G-actin

Myosin heads bind with what?

Exposed active sites

When myosin head binds with exposed active sites, what is forming?

Cross-bridges

What is a mechanical component of muscle contraction?

Cross-bridge cycling

Cross-bridge cycling causes sarcomere to _____ and muscle to _____

Shorten and contract

The energy from _____ molecule is required for each cross-bridge cycle

1 ATP

Before each cross-bridge cycle, the myosin head is in its what?

Resting high energy configuration

When myosin head in cross-bridge cycling is in its resting state from having broken down ___ in the previous cycle & stored the energy

ATP

What is still bound in cross-bridge cycling?

ADP and P

In cross-bridge cycling, tropomyosin is still prevent _____ from binding active sites on actin

myosin

Ca2+ binds troponin, which moves tropomyosin and active sites on G-actin are exposed?

Step 1 of cross-bridge cycling

Myosin heads bind to active sites on actin forming cross bridge, myosin releases what? (Step 2 of cross-bridge cycling)

Phosphate

A power stroke occurs?

Step 3 of cross bridge crossing

Movement of myosin head at hinge region which slides thin myofilament towards H zone of sarcomere, leaving myosin head in its low energy configuration, and still bound to actin but releases ADP, what is this

Power stroke

This is step 4 of cross bridge cycling, binding of a ATP molecule to myosin head causes it to detach from what?

G-actin

This is step 5 of cross bridge cycling, myosin head breaks _______________, both of which remain attached to myosin

ATP into ADP & P

In step 6 of cross bridge cycling, breakdown of ATP provides energy, which leave myosin head to return to what?

High energy configuration

When breakdown of ATP provides energy, leaving myosin head to return to its high energy configuration is known as what?

Recovery stroke

What change occurs to the myosin myofilament?

Myosin head moves at hinge

What change occurs to the actin myofilament?

Actin slid along myosin closer to H zone

Under what circumstances might ATP not be available during cross bridge cycling?

Death, no ATP, rigor mortis

What is rigor mortis?

Stiffening of muscles

Action potential propagated along what?

motor neuron

Action potential in neuron stimulates ______ of voltage gated Ca2+ channels

opening

Influx of Ca2+ into motor neuron causes release of _______ into synapse

Acetylcholine

ACh opens ________ Na+ channels on motor end-plate

Ligand-gated

Action potential propagated along ___________

muscle fiber

Action potential moves down ________

t-tubules

T-tubules wrap around what?

Sarcomeres

T-tubules wrap around sarcomeres, where actin & myosin overlap & carry action potentials into inferior of what?

muscle

Ca2+ binds troponin of _______________, causing tropomyosin to move, exposing active sites on G-actin

thin myofilaments

ATP molecules are broken down to ADP & P, releasing ________ needed to move myosin head to high energy configuration

energy

Relaxation of muscle occurs when?

ACh is no longer released at neuromuscular junction