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Physiology lab #
Due 11-1-0
Introduction
Write your Physiology lab research paper
The skeletal muscles are the muscles that allow are bodies to move. In this lab we will be observing the skeletal muscles. Each skeletal muscle is arranged in a heirarchy of tubes. At the cell level the tubes then break down into the basic elements that allow for muscle movements.
These tubes consist of the proteins myosin and actin. When the muscle is stimulated by a nerve cell, the myosin slides along the actin. This sliding action is caused when the myosin heads attach to the actin and then being facilitated by ATP and calcium ions, the myosin head contracts and pulls the myosin. This motion contracts the myofibrils and therefore contracts the muscle.
Materials and Methods
Scissors
Teasing needle
Fine-point forceps
Pipettes
Petri dish
Microscope slides, cover slips
Ruler
Compound and dissecting microscopes
Glycerinated rabbit psoas muscle in glycerol
0.5% ATP in distilled water(Solution A)
0.5% ATP plus 0.05 M KCl plus 0.001 M MgCl in distilled water (Solution B)
0.05 M KCl plus 0.001 M MgCl in distilled water(Solution C)
Procedure
First remove the muscle from the stick to which it is tied, then pour the glycerol into a Petri dish. Cut the muscle into segments of aboutcm each and place these in the glycerol solution. Each group will tease the segment of muscle into very thin groups of myofibers.Then prepare a wet mount ofthe myofibers on a slide and observe it under a dissecting scope.
Second, add solution B, observe immediately. Measure the fibers after 0 sec and calculate the degree of contraction.
Third, repeat this procedure again with solution A,new fiber and clean slides. After observing and calculating repeat the procedure again with solution C, new fibers and a clean slide.
Results and Discussion
Question What are two events necessary for contraction to occur?
AnsIn order for contraction to occur the myosin must be activated by ATP, and the myosin binding site must be exposed to the presence of Ca++ .
Question What are possible sources of ATP in an intact muscle?
Ans Possible source of ATP in an intact muscle are glucose from the aerobic pathway or creatine phosphate from the anerobic pathway.
Question What is the source of Ca++ in an intact skeletal muscle?
Ans The source of Ca++ in an intact skeletal muscle is the sarcoplasma.
Question What is the role of Ca++ in an intact skeletal muscle?
AnsCalcium is use to bind troponinCto tropomyosin in order to reveal the myosin binding site. When this occur a conformational change result which produce an interaction of cross-bridging between the thick and thin filaments.
Question What are the events leading to the release of Ca++ in an intact muscle?
Ans An electric impulse at the motor neroun causes the activation of acetylcholine at the sarcolemma . This then cause a depolarization and allow for sodium ion influx which generate an action potential across the membrane and T-tubules and this causes the release of Ca++ .
Draw the striations observed.
Label one contractile apparatus (sarcomere), A band, I band
Measure the strand using a millimeter scale and record.
PRE-TREATMENT
STRAND 1_16_______________________
STRAND __15_______________________
STRAND ___17______________________
AVERAGE LENGTH____16______________
POST-TREATMENT
STRAND 1___14_________________________
STRAND ___1_________________________
STRAND ____14_______________________
AVERAGE LENGTH__1.5_________________
DEGREE OF CONTRACTION___116%________
QuestionHave the fibers changed in length?
Ans Yes the fiber changed in length
Question Have the fibers changed in width?
AnsNo the fiber didn't change in width.
Repeat the procedures using clean slides, new muscle fibers and Solution A.
PRE-TREATMENT
STRAND 1_____15_______________________
STRAND _____15_______________________
STRAND _____15_______________________
AVERAGE LENGTH_____15_______________
POST-TREATMENT
STRAND 1______18______________________
STRAND ______1______________________
STRAND _______0____________________
AVERAGE LENGTH___1________________
DEGREE OF CONTRACTION__78.%_________
QuestionHave the fibers changed in length?
Ans Yes the fibers changed in size and became shorter.
QuestionHave the fibers changed in width?
AnsYes the fibers changed in width and became wider.
Repeat the procedures using clean slides, new muscle fibers and Solution C.
PRE-TREATMENT
STRAND 1___17_________________________
STRAND ___16_________________________
STRAND ___16_________________________
AVERAGE LENGTH____16.________________
POST-TREATMENT
STRAND 1____14________________________
STRAND ____15________________________
STRAND ____14_______________________
AVERAGE LENGTH____14._______________
DEGREE OF CONTRACTION___114%________
QuestionHave the fibers changed in length?
Ans Yes the fibers changed length and are shorter.
QuestionHave the fibers changed in width?
AnsYes the fibers changed in width and are thicker/wider.
QuestionWhich bands appear to shorten?Why?
AnsThe Z -disk seem to be the one that is shorter. This occur due to the fact that the myosin cross bridge pulls on the thin filaments causing them to slide inward, and theZdisk come toward each other and the sarcomeres appear shorter.
QuestionSarcoplasmic reticulum is destroyed in the glycerinated muscle.
Why is contraction still possible?
Ans Contraction is still possible because of the presence of calcium from external source (the solution).
QuestionWhat are the conditions necessary for the contraction to occur?
QuestionIs relaxation still possible?Explain.
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