Week 4 Muscle Excitation- Trachte

Question 1

Lou Gehrig’s Disease/ Amyotropic lateral sclerosis

Answer 1

degeneration of motor neurons

Question 2

Lambert-Eaton

Answer 2

auto-antibodies against calcium channels in motor neurons resulting in an inability to relase acetylcholine

Question 3

Botulism

Answer 3

prevents acetylcholine relases by cleaving synaptic associated proteins (SNAPS)

Question 4

Myathenia Gravis

Answer 4

autoantibodies against nicotinic receptors in skeletal muscle

Question 5

Malignant Hyperthermia

Answer 5

mutation of the ryanodine receptor allowing excessive release of calcium, usually triggered by anesthetics

Question 6

Duchenne’s muscular dystrophy

Answer 6

a mutation in dystrophin, a skeletal muscle support protein

Question 7

What happens to the A band and I band during a muscle contraction?

Answer 7

The A band remains the same, the I band decreases in width

Question 8

What causes the power stroke in a muscle contraction?

Answer 8

Release of the phosphate causes the angle of the myosin head to revert to 45 degrees

Question 9

Describe the process of a muscle contraction

Answer 9

• Ca+ is released and binds to troponin causing a conformational change in the tropomyosin, exposing the myosin binding site on the actin
• ATP hydrolysis cocks the myosin head so it is ready to attach to actin
• Myosin cross bridge binds Actin
• Phosphate is released causing the power stroke (moves the head from 90 to 45 degrees toward M line)
• ATP is required to myosin head to detach from actin

Question 10

What is required for muscle relaxation?

Answer 10

• sequestration of calcium (this required ATP) by Ca ATPases

- this allows troponin-tropomyosin complex to inhibit bind of myosin

Question 11

***What is the amount of force generated by a muscle directly proportional to?

Answer 11

the number of actin-myosin crossbridges per cross-sectional area

Question 12

When do muscles work best?

Answer 12

Muscles work best when there is considerable overlap between actin and myosin

Question 13

What is an isometric contraction?

Answer 13

when the load is larger than the muscle’s ability to move it (the muscle contracts enough to pull the tendon taut but does not actually move the body attachment)

-trying to move something that won’t move

Question 14

What is an isotonic contraction

Answer 14

if the load on the muscle is constant

Question 15

Slow twitch fibers

Answer 15

Type 1 fibers
slower myosin ATPase enzyme
contain a lot of myoglobin
Red fibers
*Need myoglobin because they require lots of oxygen to maintain

Question 16

fast twitch fiber

Answer 16

Type II fibers
Faster myosin ATPase enyme
White fibers (less myoglobin)
Adapted for anaerobic metabolism

Question 17

Concentric contraction

Answer 17

muscle contracts resulting in shortening (typical biceps curl)

Question 18

Eccentric

Answer 18

muscle lengthens while attempting to shorten
(dropping a curl with resistance, running down a hill)
more damage to muscle with this type of contraction

Question 19

What are some big differences between cardiac and skeletal muscle?

Answer 19

• Cardiac does not required innervation to contract, has autorhythmicity
• more dependent on extra-cellular calcium

Question 20

Why is smooth muscle unique?

Answer 20

• not striated
• contraction not controlled by troponin or topomyosin
• initiated by calcium interacting with a calcium-dependent myosin light chain kinase
• oftenhas autorhythmicity (like intestinal muscle)

Question 21

What is the speed of a muscle contraction dependent on?

Answer 21

myosin ATPase activity