Muscular tissue system 1

smooth muscle

non striated, involuntary

skeletal muscle

striated, voluntary

cardiac muscle

straited, involuntary

What is the name of the muscle cell

myocyte

Sarcolemma

plasma membrane

sarcoplasm

cytoplasm

sarcoplasmic reticulum

endoplasmic reticulum

Smallest to largest

sarcomere, myofibril, muscle fiber, fasicle, muscle

What does the epimysium surround?

the muscle

what does the perimysium surround?

fascicle

what does the endomysium surround?

muscle fiber

Where is the calcium stored in the skeletal muscle?

In the sarcoplasmic reticulum

What is the function of the T tubules?

Allow rapid transmission of action potential into the cell to the deepest myofibrils, and regulates calcium concentration in the sarcoplasmic reticulum

Why is that important?

So deep muscle fibers receive the message to contract at the same time as the more superficial fibers

The sarcomere runs from what to what structure?

Z-disc to Z-disc

what happens to the H-zone during muscle contraction?

The H-zone will shrink as the actin filaments are brought closer together

What happens to the A-band during muscle contraction?

The A-band does not change. It represents the length of the myosin filament which doesn’t change

What is the purpose of acetylcholinesterase?

Breaks down acetylcholine after its done its job. The components of Ach are dispersed or re-uptaken into the neuron to be synthesized into more Ach for the next signal.

Excitation Contraction coupling steps

o   1. Acetylcholine is released from the neuron and binds to receptors on the sarcolemma

 o   2. A wave of action potential (nerve signal) travels along the sarcolemma and down the T tubules

o   3. Action potential hits the triad and Ca is released from the sarcoplasmic reticulum

o   4. Calcium binds to troponin

o   5. Troponin alters the position of tropomyosin to reveal myosin binding sites

 o   6. myosin heads bind to the binding sites on actin

o   7. the power stroke occurs with the use of ATP

 o   8. actin filaments slide over myosin filaments shortening the sarcomere and creating contraction

What is the role calcium plays in muscle contraction?

Calcium binds to the troponin-tropomyosin complex to reveal the binding site for myosin heads

What would happen if no calcium was present? 

Myosin could not bind to actin and no contraction would occur.

Where does ATP play a role in muscle contraction?

ATP is necessary for the power stroke to occur. ATP is also used in the calcium pump to move calcium against its concentration gradient back into the SR during muscle relaxation.

What happens if there is no ATP?

Without ATP, myosin heads would remain attached to actin binding sites, and the fiber would be stuck in contraction. ATP allows for the release of myosin heads, cocking, and power stroking.

Acetylcholine

Ach is broken down by acetylcholinesterase and re-uptaken into the neuron

Calcium

calcium is pumped back into the sarcoplasmic reticulum by an energy requiring calcium pump

 

Troponin-tropomyosin complex

Tropomyosin covers the binding sites once calcium is removed from troponin and contraction can no longer occur.

Neurotransmitters involved

Smooth muscle responds to both ach and norepinephrine

Where calcium comes from

Calcium is stored in the SR in smooth muscle but also comes from the sarcoplasm and external to the cell

What calcium binds to

Calcium binds to calmodulin rather than troponin

How quickly it contracts and relaxes

Smooth muscle is slower to contract and relax. Longer, slower contraction process

Resistance to fatigue

Smooth muscle is slower to fatigue. It can stay contracted longer.