3.4 Excitation-Contraction coupling & muscle relaxation

excitations

an electrical signal is transmitted from a motor neuron to a skeletal fiber

• It controls what muscle to move and when

excitation-contraction coupling

Ca2+ is released from the sarcoplasmic reticulum

contraction

Ca2+ binds to troponin on the filament → cross bridges form

Relaxation

Removal of Ca2+

where is the Ca2+ resequestered into

the sarcoplasmic reticulum

__ goes back into the Sarcoplasum and is recycled

calcium

What 2 process the forming of cross bridges

Excitation-contraction coupling and contraction

Activation of skeletal muscle is _____

Voluntary

CNS signals →

electrical impulse see along a motor neuron

Where does the electrical impulse arrive

Neuromuscular junction (NMJ)

__ will be transmitted from the motor neuron to muscle fibers across the __

Electrical impulses, NMJ

Signal is transmitted from _ to _

neuron, muscle fibers

motor end plate

a specialized region of sarcolemma

Increased surface area for receptors that respond to

Neurotransmitter

what causes the opening of Voltage gated Ca2+ channels

Action potential arriving at the synaptic end bulb

Neurotransmitter that undergoes exocytosis

Acetylcholine (ACh)

When ACh is released into synaptic clef what does it bind to

ACh receptors on the motor end plate that’s part of the sarcolemma

ACh receptor opens and ___

Na+ is released generating action potential in the sarcolemma

ACh is broken down to acetate and choline by

Acetylcholine esterase (AChE)

Action protein runs along the _ and counting into the _

sarcolemma, T-tubules

what does the action potential trigger from the sarcoplasmic reticulum

The release of Ca2+

Ca2+ diffuses into

Sarcoplasm and myofibrils

Ca2+ binds to _

troponin on thin filament

_ sites on actin get exposed

Myosin-binding

Crossbridges form →

Tension is generated (contraction starts)

what happens when action potential stops arriving to NMJ

Ca2+ stops being released

the Ca2+ is pumped out go the cytoplasm and back into the

Sarcoplasmic reticulum

Cytoplasmic _

decreases

as Ca2+ falls, _ falls off of _ → myosin-binding cites get covered by tropomyosin

Ca2+, troponin

Tensions _ and and cross bridges _

Drops, cycle stops

titin brings the _ back to resting position

sarcomere

ATP useage

• Myosin moter proteins

• put Ca2+ into SR, ATP pump

• H2/k+ appose

  • muscle AP

  • nuron

• Exocytosis

Inorder for myosin binding sites on actin to be exposed, calcium must bind to _

troponin

Myosin binding sites are covered by which structure

tropomyosin

The phenomenon of rigor mortis requires the presence of _ and the absence of _

Calcium, ATP