Cardiac Muscle

Introduction

Give a brief general description, in your own words, of the aims of this practical. (5)

Experimental Preparation and Set-up

Briefly describe, in your own words, the experimental preparation and set-up used in this practical. (5)

A. Length-Force Relation

In the space below, paste a copy of your LabChart graph showing the complete experimental recording for this experiment (add more space as necessary with hard keyboard returns). Make sure that the recording is correctly identified and fully labeled with all important details. (5)

1) In the table below record the muscle length and the corresponding passive and active force at each muscle length. (5)

Muscle Length

(mm)

Passive Force

(g)

Active Force

(g)

⦁ From these data plot a graph showing how both passive force and active force vary with muscle length. Label the axes and give the graph a figure number and an appropriate title or legend. Graphs can be plotted by hand on graph paper, or prepared using a computer program such as Microsoft Excel. (5)

In the space below, paste a copy of the graph of your length- force results (add more space as necessary with hard keyboard returns).

3) How does the active length-force relation of this isolated strip of cardiac muscle relate to the function of the whole heart? (5)

B. Varying Stimulus Strength

1) Were you able to grade the strength of the contractions of the strip of cardiac muscle by varying the strength of the stimulus voltage? Briefly describe what you observed. (3)

2) How can you account for this result? (2)

C. Effect of Extracellular Calcium on Contraction Strength

In the space below, paste a fully labeled graph of your complete experimental recording for this experiment (add more space as necessary with hard keyboard returns). (5)

1) Record the active force you measured at each calcium concentration in the Table below (2)

Extracellular Calcium (mM) 0.2 0.8 2.0

Active force (g)

⦁ From these data plot a graph of the active force against the calcium concentration