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Three types of muscle fibers exist, each with its own metabolic strategy and color.
-Slow oxidative: aerobic glycolysis predominates (dark color)
-Fast glycolytic: anaerobic glycolysis predominates (light color)
-Fast oxidative-glycolytic (FOG): a blend of both strategies (tan, light-burned)
Slow oxidative fibers more common in muscles which are used for
*also higher in myoglobin: "red fibers" or "dark meat"
Fast glycolytic fibers more common in muscles which need to
move fast for very short periods of time.
*lower in myoglobin: "white fibers" or "white meat"
Fast oxidative-glycolytic fibers more common in muscles which need both
endurance and speed.
Each type of muscle fiber tends to be innervated by a different motor unit, so that when a particular
motore neuron fibers it activates only fibers of one type.
Two sources of fatigue:
defense mechanism: if the muscle runs out of ATP, it goes into rigo, which would be a bad way to end your exercise routine.
- Theory of Causes:
- *local increase in ADP and Phosphate block Ca++ release by sarcoplasmic reticulum.
*accumulation of lactate inhibits enzymes
*accumulation of extracellular K+
*depletion of glycogen
Two sources of fatigue:
the central nervous system "shuts down" and will not activate motor neurons (the person "quits")
*Recovery consists of replenishing ATP, creatine, oxygen (bound to myoglobin), glycogen, Ca++ stores, and restoring pH to normal levels
Compared to skeletal muscle, cardiac muscle is adapted to be fatigue-resistant and
*higher number of mitochondria
*higher number of myoglobin content
*higher creating phosphate content
*ample blood supply
Cardiac muscle cannot contract under anaerobic conditions, at most
the heart can get 10% of energy from anaerobic metabolism; beyond that, pump failure occurs
With a fulcrum, lever and force, one can move almost anything. The effort is the ______ _____; the fulcrum is the _____; and the load is the ______ or ______ being moved.
muscle force; joint; weight; object
First-Class Lever is arranged in the order
- Effort, Fulcrum, Load.
- -the fulcrum is between the effort and the load.
This is analogous to a scissors. For example, the neck muscles (effort) use the atlanto-occipital joint (fulcrum) to keep the head (load) from falling forward.
Second-Class Lever is arranged in the order
- Fulcrum, Load, Effort.
- -the load is between the effort and the fulcrum.
This is analogous to a wheelbarrow. If you were to stand on your toes, the fulcrum would be the metacarpal-phalangeal joints; the load would be the weight of the body; and the effort would be supplied by the gastrocnemius and soleus muscles.
Third-Class Lever is arranged in the order
Fulcrum, Effort, Load.
This analogous to a pincers or tweezers. These are by far the most common levers in the human body, but lack stability. For example, if you hold a weight in your hand, the fulcrum is the elbow joint; the effort is the arm flexors; and the load is the weight being held.
Three terms used to describe muscle anatomy.
the place where a muscle "begins," where it attaches to a relatively immoveable point.
-usually, this is proximal
- the place where a muscle "ends," where it attaches to a moveable part.
- -usually, this is distal
what the muscle does when it contracts.
Names of muscle function
prime mover (agonist)
Prime Mover (Agonist):
muscle that does most of the work in the action being discussed.
oppose action of agonist
aid agonist in creating movement.
stabalizes the muscle origin.
Example: fixators in the shoulder girdle help to stop rotation of the shoulder joint during the motions of the triceps and biceps.
Names based on location include the
Many muscles are named after their shape:
Deltoid: after the Greek letter delta
Trapezius: has four sides like a trapezoid
Rectus (straight) abdominis
Rectus (straight) femoris
Some muscles are named for their size:
The triceps ("three-head") and biceps ("two-head") are named after the number of
Fibers of the transversus abdominis run _________ in the abdomen.
The sternocleidomastoid is easy because it's all there: it originates in the _______ and clavicle; it inserts on the ______ process of the temporal bone.