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STUDENT OBJECTIVE

Students study muscle at the microscopic, gross, and physiological levels. They also study bone at the microscopic and gross levels, and compare endoskeletons with other types of skeletal systems.

EQUIPMENT	AMOUNT
	(Class of 24 with 8 groups)
Compound microscope Stimulator and electrode Kymograph or recorder, stylus or transducer	1/student 1/group or lab 1/group or lab
MATERIALS
Earthworms, live Fetal pigs from previous exercise Dissecting trays Dissecting instruments Fresh beef bones cut longitudinally Dry mammalian long bones Exoskeleton examples (insects, millipedes, crabs, spiders) Endoskeleton examples (human, frog, bird) Prepared slides (can be shared to reduce costs) Skeletal muscle, longitudinal section (CBS#31-3256)* Smooth muscle, longitudinal section (CBS#H1260)* 31-3340 Earthworm, cross section (CBS#30-7246)* Bone (CBS#31-2964)* Cartilage, hyaline (CBS#31-2886)* Grasshopper, cross section Physiogrip by Intellitool (Batavia, IL) Computer Electrode gel Square wave stimulator	1/group 1/student 1/student set/student Demonstration 1/group several/lab 2/lab 1/student 1/student 1/student 1/student 1/student 1/student 1/group 1/group 1/group 1/group

*Please refer to the Appendix for name and address of supplier.

PREPARATION

Four Weeks before Lab

Order and pre-test Physiogrip systems. Test square wave stimulators.

Notes

Physiogrip may be used as a class demonstration. If done by student groups, groups should be a minimum of 4—5 students.

Classroom Suggestions

1. Check out the links for this lab topic at http://auth.mhhe.com/biosci/genbio/dolphin/ You will find useful materials for developing your lab introduction or summary, and in some cases, you may want to tell students to connect to a particular site for further information.

ANSWERS TO CRITICAL THINKING QUESTIONS

1. Neuromuscular excitability is extremely sensitive to calcium. Hypercalcemia would lead to increased heart (cardiac muscle) irritability and may cause life-threatening cardiac arrhythmias. Hypocalcemia would depress the heart. Also very low Ca⁺⁺ levels would increase excitability of the neurons (due to increased Na⁺ permeability). Peripheral nerves may discharge impulses spontaneously, leading to tetanic muscle contraction.
2. Weight. Flight requires a light skeleton. The bones of birds are incredibly light and delicate. They are hollow with an internal framework of bars giving structural support. The spaces are filled with air rather than marrow.
3. By closely studying the bones to determine possible function (i.e., weight bearing, etc.), analyzing bone ends to determine joint structure and range of movement, and analyzing sites of muscle attachment, scientists can deduce a theoretical body shape. Computer mirror-imaging can help fill in gaps and computer-assisted stereolithography can guide a laser to sculpt a model from resin.

SUPPLEMENTAL MATERIALS