E-C coupling HeartLAb (The sliding Filament of Contraction)

Question 1

1. When ATP binds to the myosin head, does what to the cross bridge

Answer 1

hydrolyses (energises the cross-bridge)

Question 2

2. Ca2+ binds to what

Answer 2

Tropnin C

Question 3

2. Ca2+ binds to Troponin C, myosin binding sites are exposed, the myosin heads then engage with what

Answer 3

actin

Question 4

2. What happens if there is no Ca2+

Answer 4

No engagement, no contraction

Question 5

3. ADP and phosphate ____ from myosin head

Answer 5

unbinds

Question 6

3. ADP and phosphate unbinds from where

Answer 6

myosin head

Question 7

3. ADP and phosphate unbinds from myosin head, resulting in what

Answer 7

bending the cross-bridge

Question 8

3. ADP and phosphate unbinds from myosin head, bending the cross-bridge, what does this ultimately do

Answer 8

this moves the myosin filament along the actin filament (power stroke)

Question 9

3. What unbinding allows for the myosin filament to move along the actin filament (power stroke)

Answer 9

ADP and phosphate unbinding from the myosin head

Question 10

4. ADP and phosphate unbind, this allows for what

Answer 10

ATP to be available

Question 11

4. The presence of additional ATP binds to where

Answer 11

The myosin head

Question 12

The presence of additional ATP binds to the myosin head, in this state, the cross-bridge is not ________ and detaches from actin filament

Answer 12

energised

Question 13

The presence of additional ATP binds to the myosin head, in this state the cross-bridge is not energised and what happens

Answer 13

detaches from actin filament

Question 14

SACROMERE LENGTH AND CONTRACTILE FORCE
Sarcomere length ______ with increased blood filling - stretching the muscle

Answer 14

increases

Question 15

SACROMERE LENGTH AND CONTRACTILE FORCE
Sarcomere length increases with increased blood filling - resulting in what

Answer 15

stretching the muscle

Question 15

cardiac muscle stretch does 3 things to increase contractile force, what are they?
C
S
Ca

Answer 15

1. allows for more (C)ross bridges between thick and thin filaments to form
2. Increases the (S)ensitivity of the contractile machinery to Ca2+
3. Increases (c)a2+ release from the Cardiomyocyte

Question 15

WHERE DOES CA2+ COME FROM FOR THE SLIDING FILAMENT THEORY
What are the two main sources of Ca2+ around the cardiomyocyte

Answer 15

Extracellular 2(mM)
SR (2-3mM)