18. Excitation Contraction Coupling

Question 1

How long does Rigor Mortis last?

Answer 1

15-25 hours

Question 2

Which type of muscle fiber has more mitochondria and myoglobin?

Answer 2

Type I

Question 3

What receptors are responsible for initiating a local potential at the neuromuscular junction?

Answer 3

Ligand gated acetylcholine receptors

Question 4

What are the three members of the troponin complex, and what do they bind to?

Answer 4

Troponin I: Actin

Troponin C: Calcium

Troponin T: Tropomyosin

Question 5

How do we induce a smooth, continuous muscle movement within a single motor unit when our neurons can only produce all or nothing responses?

Answer 5

Summation and tetanization

Increasing frequencies of stimulation increases the rate of contraction

Question 6

What enzyme breaks down acetylcholine in the synaptic gap?

Answer 6

Acetylcholine Esterase

Question 7

Would smaller, more precise muscles have more or less muscle fibers?

Answer 7

More muscle fibers

This allows them to regulate the force of their contraction more precisely.

Question 8

How do we make a muscle contract with more or less force?

Answer 8

Recruitment - activate more or fewer muscle units

Question 9

Where is the myosin head after ATP binds, but before ATP is hydrolyzed?

Answer 9

Released from the actin, but not yet cocked.

Question 10

What happens after the myosin head attaches to the actin?

Answer 10

Pi dissociates and the power stroke contracts the sarcomere.

Question 11

How long can we use phosphocreatine for muscle contraction?

Answer 11

8-10 seconds

Question 12

Besides the muscle cell hypertrophy, what changes in the muscles of a trained athelete vs someone like me (a nerd)?

Answer 12

More mitochondrial enzymes

More glycogen

More phosphocreatine

More stored fat

Question 13

Where are the two hinges in a myosin molecule?

Answer 13

Hinge 1: Separating the two heads

Hinge 2: One on each of the myosin heads, allowing independent movement

Question 14

When is a sarcomere able to produce the maximum amount of force?

Answer 14

When there is no overlap in actin, and every myosin head is able to access a binding site.

Question 15

Where is the myosin when the ATP is hydrolyzed?

Answer 15

Cocked and ready to interact with actin and contract

Question 16

What enzyme is used to shuttle calcium from the sarcoplasm into the sarcoplasmic reticulum after a contraction occurs?

Answer 16

Calcium ATPase

Question 17

Which type of muscle fibers have more phosphocreatine?

Answer 17

Type II

Question 18

Which type of muscle fiber has more glycogen?

Answer 18

Type II

Question 19

What receptors have to change confirmation to allow calcium to release into the sarcoplasm?

Which one is located in the membrane of the T Tubule?

Answer 19

DHP and RYR

DHP

Question 20

Which type of muscle fibers are larger?

Answer 20

Type II

Question 21

How long can we use Glycolysis for a muscle contraction?

Answer 21

1.3 - 1.6 minutes

Question 22

What allows the sarcoplasmic reticulum to hold up to 40x more calcium than it otherwise would?

Answer 22

Calsequestrin

Question 23

What small structures are made in the sarcolemma of the neuromuscular junction to increase the action potential going into the muscle?

Answer 23

Subneural Clefts

Question 24

What is a motor unit?

Answer 24

All the muscle fibers innervated by a single nerve fiber.

Question 25

How long can we use oxidative phosphorylation to sustain a muscle contraction?

Answer 25

Until the muscle runs out of things to throw into the TCA cycle.

Question 26

Where is the myosin head after a contraction, but before it binds a new ATP?

Answer 26

Still stuck to its binding site on the actin.

Question 27

When we strength train, do we get more muscle fibers, or just bigger muscle fibers?

Answer 27

Just bigger muscle fibers

(more myofibrils per muscle fibers)

Question 28

How long can we use stored ATP for a muscle contraction?

Answer 28

Two seconds