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Frog Lab I Slide 1 Bioengineering 3202- Human Physiology

Frog Lab: Anatomy and Contraction

Bioengineering/Physiology 3202

Frog Lab I Slide 2 Bioengineering 3202- Human Physiology

Frog Heart Anatomy/Function

• Shared ventricle but bloodseparated

– Spiral fold

– Initial flow throughpulmonary because ofreduced pressure

– Resistance to flow varieswith breathing (inhalereduces resistance)

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Frog Lab I Slide 3 Bioengineering 3202- Human Physiology

EC Coupling

• Action potential causes influxof Ca2+

• In mammals and birds, thiscauses release of more Ca2+

• Ca2+ interacts withactin/myosin to causecontraction

• Pumps gather up Ca2+ orremove it from cell

Frog Lab I Slide 4 Bioengineering 3202- Human Physiology

Regulation of Cellular Contraction

• Adjust pretension to improvespacing in contractile elements

– Optimal spacing

• Works at tissue and wholeheart levels

mV

t

Action Potential

Twitch (tension)

Cai transient

[Ca++]gram

Cai from ICa

0

20

4060

80100120

1 1.5 2 2.5 3 3.5 4

Tens

ion

[% o

f max

imum

]

Striation Spacing [µm]

Total tension

Passive (rest) tension

Twitch tension

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Frog Lab I Slide 5 Bioengineering 3202- Human Physiology

Effect of Pretension

time

tens

ion

activ

e te

nsio

n

isometriccontraction

resting tension

Frog Lab I Slide 6 Bioengineering 3202- Human Physiology

Total tension

Passive (rest) tension

Twitch tension

Frank Starling Mechanism

• Increased fillingproduces increasedoutput

• Extension of cellularmechanism

• Does not requireneural input

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Frog Lab I Slide 7 Bioengineering 3202- Human Physiology

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 8 Bioengineering 3202- Human Physiology

In Situ Views

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Frog Lab I Slide 9 Bioengineering 3202- Human Physiology

Lab Preparation