QuestionSBA
QuestionChoice
This is incorrect. The T-tubule system describes the invaginations of cell membranes deep into the centre of cardiomyocytes, allowing rapid transmission of the action potential. This, therefore, helps with the initial depolarization of the cell but is not the site of calcium release. calcium is released from the sarcoplasmic reticulum.
10026257
c
Calcium, released from the T-tubule system, binds to troponin-C, causing a conformation change and allowing actin and myosin to form cross-bridges, shortening the sarcomere
QuestionChoice
This is incorrect. Whilst the sequence of events is otherwise correct, the process of myosin and actin filaments sliding past each other results in the shortening, not lengthening of the sarcomere. This is the basis of cardiomyocyte contraction.
10026256
b
Calcium, released from the sarcoplasmic reticulum, binds to troponin-C, causing a conformation change and allowing actin and myosin to form cross-bridges, lengthening the sarcomere
QuestionChoice
This is incorrect. calcium binds to troponin-C, not troponin-I. Troponin-I is the inhibitory form, preventing actin-myosin cross-bridge formation.
10026259
e
Calcium, released from the sarcoplasmic reticulum, binds to troponin-I, causing a conformation change and allowing actin and myosin to form cross-bridges, lengthening the sarcomere
QuestionChoice
This option is incorrect for two reasons. Firstly, the T-tubule system describes the invaginations of cell membranes deep into the centre of cardiomyocytes, allowing rapid transmission of the action potential. This, therefore, helps with the initial depolarization of the cell but is not the site of calcium release. calcium is released from the sarcoplasmic reticulum. Secondly, calcium binds to troponin-C, not troponin-I. Troponin-I is the inhibitory form, preventing actin-myosin cross-bridge formation.
10026258
d
Calcium, released from the T-tubule system, binds to troponin-I, causing a conformation change and allowing actin and myosin to form cross-bridges, shortening the sarcomere
QuestionChoice
This is correct. Calcium is released from the sarcoplasmic reticulum during calcium-induced calcium release. This binds to troponin-C which causes a conformational change, moving troponin-C and exposing binding sites on the actin molecule. This allows myosin heads to bind. As the myosin and actin filaments slide past each other, the sarcomere is shortened.
10026255
a
Calcium, released from the sarcoplasmic reticulum, binds to troponin-C, causing a conformation change and allowing actin and myosin to form cross-bridges, shortening the sarcomere
Concept
Chapter
2693
4534
Myocytes
Topic
159
Cardiovascular physiology
17649
Which of the following statements is correct regarding excitation-contraction coupling in cardiomyocytes?
a