OCA2-Muscular System (or Online Course Assignment #2)
Be sure to view the helpful information about levers before beginning this assignment. This information is also available in the course content area of the home page.
If you encounter information that was NOT discussed in class, refer to the OER textbook that is required for this course.
You are allowed to use your book, notes, and other resources when completing this assessment. There is no time limit. You are allowed to complete this assignment as many times as you'd like before the due date. Your highest score will be kept.
If you continue to do this assignment after the due date, it will not adversely affect your grade. The highest score that you earned before the assignment deadline will be used in the Canvas grade book. If you do this assignment after the deadline for practice, it will appear as though it is late even though it is NOT late, and no points will be deducted for tardiness.
Helpful information about lever systems:
A lever includes the following components: (a) the lever arm (A) (rigid bar or bone in the body), (b) the fulcrum (F) (axis of rotation or joint in the body), (c) the load (L) (center of mass or weight of the body part being moved), and the (d) effort (E) (force exerted by pulling of the muscle insertion).
The effort arm (EA) is the distance between the fulcrum (joint) and the effort (muscle insertion)
The load arm (LA) is the distance between the fulcrum (joint) and the load (center of mass)
There are three main classes of levers
First-class lever: LFEorEFL
-- The fulcrum is always between the load and the effort.
-- A first-class lever can be a speed lever or a power lever.
-- Scissors and seesaws are examples of a first-class lever.
-- In the human body, a first-class lever raises your head off of your chest using your posterior neck muscles
2. Second-class: FLE or ELF (mechanical advantage) (power lever)
-- The load is always between the fulcrum and the effort.
-- The effort arm (EA) is always longer than the load arm (LA), so EA > LA.
-- Any lever where EA > LA is a power lever that has a mechanical advantage.
-- Power levers are efficient at moving large loads. (A small effort exerted over a relatively large distance can move a large load over a small distance.)
-- A wheelbarrow is an example of a second-class lever.
-- In the human body, a second-class lever raises your body onto its tip-toes using your calf muscles
3. Third: FEL or LEF (common in body) (mechanical disadvantage // speed lever)
-- The effort is always between the fulcrum and the load.
-- The load arm (LA) is always longer than the effort arm (EA), so LA > EA
-- Any lever where LA > EA is a speed lever that has a mechanical disadvantage.
-- Speed levers are efficient at moving a load rapidly over a large distance with a large range of motion.
-- A shovel, a baseball bat hitting a ball, and tweezers are examples of third-class levers.
-- In the human body, flexing the forearm with the biceps brachii muscle is an example of a third-class lever.
-- This is the most common type of lever in the human body. Thus, the body is engineered for moving limbs quickly over a large range of motion in order to move the body quickly.
4. There is one other type of lever within the human body that uses a pulley system. One of the extraocular muscles of the eye called the superior oblique muscle extends along the inner wall of the eye orbit. It then travels through the trochlea, which is a loop composed of fibrocartilage that is attached to the frontal bone. The muscle tendon turns at a right angle and then attaches to the eyeball. This muscle uses the trochlea as a pulley to depress the eye and to turn it laterally.
OPTIONAL VIDEO (Lever Systems) (6:47) (below)
OPTIONAL VIDEO (Extraocular muscles of the eye) (10:13) (below)
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