Laboratory 4: Feeding mechanisms, feeding mechanics, and electromyographic free inquiry
Name: ______GREG CROWTHER____________________________; Date: __MAY 2015______________
Other Group Members: _____JEFF JENSEN___________________________________________________
Grading: up to 8 points for active participation in the lab, including the group
presentation at the end, and up to 12 points for the specific items below.
STATION 1: Comparative feeding mechanisms
STATION 1a: Teleost head (Rockfish)
How does this mobility and speed contribute to suction feeding?
[1 point] A mobile jaw controlled by fast muscles enables a rapid expansion in mouth volume.
This rapid volume change creates negative pressure in the mouth, sucking water into the
mouth. (This is analogous to how air is drawn into the lungs.)
STATION 1c: Skull of a non-mammal (alligator) versus a mammal (cat)
How do the teeth compare, and how does this relate to difference in metabolic rate?
Cats, as mammals, have higher metabolic rates than alligators. The cat’s teeth demonstrate
precise occlusion and are specialized, allowing fine slicing of prey etc., which enables more
rapid digestion and assimilation of nutrients. The alligator’s teeth are more similar to each
other (less specialized), so the prey can’t be processed as fully in the mouth.
Would you expect the movements of the alligator jaw to be as complex as those of a
mammal? Explain.
[1 point] Alligators have little skull behind the teeth relative to mammals (not much of a
coronoid process or zygomatic arch, for example), and thus relatively few/simple jaw muscles
as well, so their jaw movements should be simpler than those of mammals. Alligator jaws
basically operate as a simple hinge designed to capture, hold, and crush the prey (which
requires a stable jaw), not to perform fine chewing (which requires more mobile jaw).
STATION 1d: Skull of a carnivore (cat) versus herbivore (beaver)
Where is the jaw joint relative to the line of the tooth row? How is this related to how the
teeth are used?
Carnivores generally have jaw joints in line with the rows of teeth, whereas herbivores’ jaw
joints tend to be above the rows of teeth. This position makes the jaw less stable but more
mobile, allowing for more lateral motion, as needed in grinding plant matter. Herbivores’ jaw
joint position also allows many of the teeth to come together at about the same point, forming
grinding surfaces, whereas the carnivore jaw joint tends to focus force at a specific location,
maximizing bit force to subdue the prey.
What skull has a larger area of origin of the temporalis? Which has a larger coronoid
process? What does the coronoid process do, and how does this relate to function?
Carnivores have more prominent temporalis muscles, which help snap the jaw shut and
subdue prey, while herbivores have more prominent masseters for prolonged chewing. Thus,
BBIO352 – Principles of Anatomy and Physiology II, Winter 2015
Laboratory 4: Feeding mechanisms, feeding mechanics, and electromyographic free inquiry
cats have a relatively large temporalis origin and a large coronoid process, which is where the
temporalis inserts.
STATION 2: Your investigation
Indicate the names, origins, insertions, and actions, of the muscle(s) you will be
investigating in the table, and draw a sketch using the appropriate figure below the table.
[1 point for table, 1 point for drawing]
Muscles studied by the different groups included the following:
Muscle
Biceps brachii
Biceps femoris
Gastrocnemius
Triceps brachii
Vastus medialis
Origin
Scapula (coracoid
process and
supraglenoid tubercle)
Femur (ischial
tuberosity, linea
aspera)
Distal femur
(condyles)
Scapula (infraglenoid
tubercle) and humerus
Femur (linea aspera)
Insertion
Tuberosity of
radius
Action
Flexes elbow and
shoulder
Tibia and Fibula
Flexes knee, extends hip
Calcaneus
Plantar flexion, knee
flexion
Extends elbow and
shoulder
Knee extension
Olecranon of
ulna
Tuberosity of
tibia
Your sketches did not have to be super-detailed but should have been consistent with the
origins and insertions listed in the table.
Finally … your experiment!
What is your question?
What is your hypothesis?
Describe how you are going to test your hypothesis. What data are you going to collect?
Describe your data – what did you find?
What do your data mean?
What is your conclusion about your hypothesis?
[8 points] There was a lot of freedom for groups to define their own questions and hypotheses.
From the instructor’s standpoint, it was most important that you offered the following:
 a hypothesis that could be tested with our EMG setup (rather than, say, looking at
activation levels of two different non-contralateral muscles)
 a quantitative summary of your data, being clear about where the numbers came from
(are they averages? from one movement or several repetitions? over what time
periods?)
BBIO352 – Principles of Anatomy and Physiology II, Winter 2015
Laboratory 4: Feeding mechanisms, feeding mechanics, and electromyographic free inquiry

a reasonable interpretation of your data, explaining whether they supported the
hypothesis or why no conclusion could be drawn
BBIO352 – Principles of Anatomy and Physiology II, Winter 2015