The Muscular System Flashcards
The axial and appendicular muscles have different functions.
What are the divisions and functions of the muscular system?
The muscular system is divided into axial and appendicular divisions.
Axial muscles support and position the axial skeleton.
Appendicular muscles support, move, and brace the limbs.
How many skeletal muscles are there in the body?
What factors influence the performance of a skeletal muscle?
There are ~700 skeletal muscles in the human body.
Skeletal muscle performance varies according to muscle fibre organization and how the muscle attaches to the skeleton.
Muscular power and range of motion are influenced by fascicle organization and leverage.
Why does a pennate muscle generate more tension than does a parallel muscle of the same size?
In a pennate muscle, the fascicles form a common angle with the tendon. It pulls at an angle, so contracting pennate muscles do not move their tendons as far as parallel muscles do. However, it contains more muscle fibres (thus, more myofibrils) than does a parallel muscle, so it produces more tension.
Describe a parallel muscle.
Fascicles are parallel to the long axis of the muscle. Most skeletal muscles are parallel muscles (e.g., biceps brachii)
Describe a convergent muscle.
Muscle fascicles extending over a broad area converge on a common attachment site (e.g., pectoralis major).
A convergent muscle is versatile because the stimulation of different positions of the muscle can change the direction of the pull. However, fibres in convergent muscle does not pull as hard on the attachment site as would a parallel muscle of the same size.
Describe a circular muscle.
a.k.a. sphincter muscle.
The fascicles are concentrically arranged to encircle a duct, tube, or opening. When the muscle contracts, the diameter of the opening decreases (constricts).
A lever is a rigid structure used to life or pry something that pivots on a fixed point called the fulcrum.
Describe a first-class level.
The fulcrum lies between the applied force and the load.
Akin to a pry bar (e.g., neck extension)
A lever is a rigid structure used to life or pry something that pivots on a fixed point called the fulcrum.
Describe a second-class lever.
The load is located between the applied force and the fulcrum.
Because the force is always farther away from the fulcrum than the load is, a small applied force can move a larger weight; albeit slowly and over a short distance. Thus, the effective force is increased at the expense of speed and distance moved.
Akin to a wheelbarrow
e.g., plantar flexion at ankle joint
A lever is a rigid structure used to life or pry something that pivots on a fixed point called the fulcrum.
Describe third-class levers.
The most common levers in the body.
The force is applied between the load and the fulcrum.
Speed and distance travelled are increased at the expense of effective force.
Akin to barbecue tongs.
e.g., flexion at elbow joint
(In the biceps brachii muscle, the load is six times farther from the fulcrum than is the applied force. The effective force is reduced to the same degree)
What are the origins and insertions of muscles?
The origin of the muscle is the place where the fixed end attaches.
The insertion of the muscle is the site where the movable end attaches to another structure.
Describe the role of the agonist, synergist, and antagonist muscles.
An agonist is a prime mover; its contraction is chiefly responsible for producing a particular movement.
A synergist helps the larger agonist work efficiently by providing additional pull near the insertion, or stabilization of the origin. Synergists that assist by preventing movement of another joint are called fixators.
The action of an antagonist opposes that of a particular agonist. (e.g., the triceps brachii is the antagonist of the biceps brachii and vice versa)
