Question

an increase in extracellular ca²⁺ generally increases
multiple choice
autonomic stimulation of the heart.
the frequency of the action potentials.
the force of contraction.
the heart rate.
na⁺ channel opening.

Explanation:

Calcium ions ($Ca^{2 +}$) play a crucial role in muscle contraction. In cardiac muscle, an increase in extracellular $Ca^{2+}$ leads to more $Ca^{2+}$ entering the cardiac - muscle cells. This enhances the interaction between actin and myosin filaments, resulting in a stronger force of contraction. It does not directly increase autonomic stimulation of the heart, the frequency of action potentials, heart rate, or $Na^{+}$ channel opening in the way described.

Answer:

C. the force of contraction.