Calcium signals initiate contraction

Question 1

A complex of 3 proteins

Answer 1

Troponin

Question 2

What binds reversibly to Ca2+ and controls the position to tropomysoin?

Answer 2

• Troponin C binds reversibly to Ca2+
  -Troponin controls position of tropomysoin

Question 3

partially covers myosin binding site on actin, Prevents myosin and actin from interacting

Answer 3

Tropomyosin

Question 4

Tropomyosin function

Answer 4

Tropomyosin partially covers the myosin binding site on actin

Prevents myosin and actin from interacting

Question 5

What are the 6 contraction steps

Answer 5

1) Calcium release from terminal cisternae
2) Calcium binds troponin
3) Troponin pulls tropomyosin from myosin-binding sites on actin
4) Myosin binds tightly to and moves actin
6) Repeated as long as binding sites are uncovered and A T P is available

Question 6

These are the
1) Calcium release from terminal cisternae
2) Calcium binds troponin
3) Troponin pulls tropomyosin from myosin-binding sites on actin
4) Myosin binds tightly to and moves actin
6) Repeated as long as binding sites are uncovered and A T P is available

Answer 6

6 contraction steps

Question 7

describe the relaxed state of myosin and how troponin and tropomyosin act

Answer 7

• Myosin head cocked
• Tropomyosin partially blocks binding site on actin
  -Myson is weakly bound to actin

Question 8

Initiation of contraction happens when

Answer 8

A calcium signal initiates contraction

Question 9

Arrange the following in order:
-Ca2+ levels increase in cytosol
-Troponin-ca2+ complex cells pulls tropomyosin away from actin’s myosin-binding sites
-Myosin binds strongly to actin and completes Powerstroke
-Actin filaments moves
-Ca2+ binds to troponin (TN)

Answer 9

1) Ca2+ levels increase in cytosol
2) Ca2+ binds to troponin (TN)
3) Troponin-ca2+ complex cells pulls tropomyosin away from actin’s myosin-binding sites
4) Myosin binds strongly to actin and completes Powerstroke
5) Actin filaments moves

Question 10

What is the order of the CONTRACTION CYCLE

Answer 10

1) ATP binds to myosin. Myosin releases actin
2) Myosin hydrolyzes ATP. Energy from ATP rotates the myosin head to the cocked positon. Myosin binds weakly to actin
3)Power stroke- begins when tropomysoin moves off the binding site.
4) Myosin releases ADP at the end of the power stroke

Question 11

What chemical initiates excitation-contraction coupling

Answer 11

Acetylcholine

Question 12

Where is ACH released from

Answer 12

The somatic motor neuron

Question 13

What does Ach initiate?

Answer 13

Action potential in the muscle fiber

Question 14

In the muscle fiber, ACh binds to the receptors on the sarcolemma which causes what?

Answer 14

It causes Na+ to enter the cell and K+ ions to exit the cell.

Depolarizatio occurs which causes end-plate potential (EPP)—> muscle action potential

Question 15

What does a muscle action potential trigger?

Answer 15

calcium release from the sarcoplasmic reticulum

Question 16

What happens when calcium binds to troponin?

Answer 16

It initiates a contraction

Question 17

What are the steps when Acetylcholine initiates excitation-contraction coupling?

Answer 17

1. Acetylcholine (ACh) is released from the somatic motor neuron
2. ACh initiates an action potential in the muscle fiber
   — ACh binds to receptors on the sarcolemma
   — Na+ enters the cell and K+ions exit the cell
3. The muscle action potential triggers calcium release from the sarcoplasmic reticulum
4. Calcium combines with troponin to initiate contraction

Question 18

1. Acetylcholine (ACh) is released from the somatic motor neuron
2. ACh initiates an action potential in the muscle fiber
   — ACh binds to receptors on the sarcolemma
   — Na+ enters the cell and K+ions exit the cell
3. The muscle action potential triggers calcium release from the sarcoplasmic reticulum
4. Calcium combines with troponin to initiate contraction

Answer 18

Acetylcholine initiates excitation-contraction coupling steps