Frog Lab: Anatomy and Contraction
Bioengineering/Physiology 3202
Frog Lab I Slide 1
Bioengineering 3202- Human Physiology
Frog Heart Anatomy/Function
• Shared ventricle but blood separated
– Spiral fold
– Initial flow through pulmonary because of reduced pressure
– Resistance to flow varies with breathing (inhale reduces resistance)
Frog Lab I Slide 2
Bioengineering 3202- Human Physiology
1

EC Coupling
• Action potential causes influx of Ca 2+
• In mammals and birds, this causes release of more Ca 2+
• Ca 2+ interacts with actin/myosin to cause contraction
• Pumps gather up Ca 2+ or remove it from cell
Frog Lab I Slide 3
Bioengineering 3202- Human Physiology
Regulation of Cellular Contraction
Action Potential
Twitch (tension) • Adjust pretension to improve spacing in contractile elements
– Optimal spacing
• Works at tissue and whole heart levels
Ca i transient mV
[Ca ++ ] gram
Ca i
from I
Ca t
Total tension
Twitch tension
Passive (rest) tension
Frog Lab I
120
100
80
60
40
20
0
1
Slide 4
1.5
2 2.5
3 3.5
4
Striation Spacing [µm]
Bioengineering 3202- Human Physiology
2

isometric contraction
Effect of Pretension resting tension
Frog Lab I Slide 5 time
Bioengineering 3202- Human Physiology
Frank Starling Mechanism
Total tension
Twitch tension
• Increased filling produces increased output
• Extension of cellular mechanism
• Does not require neural input
Passive (rest) tension
Frog Lab I Slide 6
Bioengineering 3202- Human Physiology
3

Lab Goals/Tasks
• Dissection of heart
– Prepare according to web site
– Bring digital camera to make photos
• Measure contraction
– Attach force transducer
– Calibrate transducer
– Measure contraction as function of pre-tension
Frog Lab I Slide 7
Bioengineering 3202- Human Physiology
In Situ Views
Frog Lab I Slide 8
Bioengineering 3202- Human Physiology
4

Lab Preparation
Frog Lab I Slide 9
Bioengineering 3202- Human Physiology
5