Chapter 11: Muscular System Flashcards
What are the 5 functions of the muscular system?
1) Stabilize body position. 2) Produce movement. 3) Regulate organ volume. 4) Move substances. 5) Produce heat.
How many individual muscles are in the body?
700
How do skeletal muscles produce movement?
They exert force on tendons which pull on bones or other structures. When a skeletal muscle contracts, it moves one of the articulating bones in a joint.
What is the origin?
The attachment of the muscle’s tendon to a stationary bone.
What is the insertion?
The attachment of the muscle’s other tendon to a movable bone.
What is the belly?
The fleshy middle part of the muscle between the tendons.
What is reverse muscle action (RMA)?
Muscle actions can be reversed during specific movements so the positions of the origin and the insertion are switched.
What is the lever?
Rigid structure that can move around a fixed point (joint, fulcrum).
What is the effort?
The force exerted by the muscular contraction that causes movement.
What is the load?
The resistance that opposes the movement. Can be the weight of the body part being moved.
What is mechanical advantage?
When the load is closer to the fulcrum, and the effort is farther from the fulcrum. A small effort is required to move a large load over a small distance.
What is mechanical disadvantage?
When the effort is closer to the fulcrum, and the load is farther from the fulcrum. A large effort is required to move a small load but at a greater speed.
First class lever.
Fulcrum is between the effort and the load. Can produce a mechanical advantage or disadvantage depending on whether the effort or load is closer to the fulcrum.
First class lever example.
1) Scissors. 2) Head resting on vertebral column.
Second class lever.
The load is between the fulcrum and the effort. Always produces a mechanical advantage. Produces the most force, but is uncommon in the human body.
Second class lever example.
1) Wheelbarrow. 2) Standing up on toes.
Third class lever.
The effort is between the fulcrum and the load. Always produces a mechanical disadvantage. Favours speed and range of motion over power. The most common lever in the human body.
Third class lever example.
Elbow and biceps brachii with arm and forearm bones.
How are muscle fibres arranged in a fascicle?
They are all parallel to one another.
How much does a muscle fibre shorten when it contracts?
It shortens to 70% of its resting length.
What can the length of a muscle fibre tell us?
The longer the fibre, the greater the range of motion.
What can the cross-sectional area of a muscle tell us?
The more fibres per unit of cross-sectional area, the greater the power.
What are the 5 patterns of fascicles?
1) Parallel. 2) Fusiform. 3) Circular. 4) Triangular. 5) Pennate.
Parallel.
Fascicles are parallel to the longitudinal axis of the muscle. There are fewer and longer fascicles, generating a large range of motion with less power.
Fusiform.
Fascicles are nearly parallel to the longitudinal axis of the muscle, and are spindle-shaped.
Circular.
Fascicles are in concentric circular arrangements, and mostly form sphincter muscles.
Triangular.
Fascicles spread over a broad area and then converge at a thick central tendon.
Pennate.
Fascicles are short and feather-shaped, generating a small range of motion with lots of power. The tendon extends nearly the entire length of the muscle.
Unipennate.
Fascicles are arranged on only one side of the tendon.
Bipennate.
Fascicles are arranged on both sides of centrally positioned tendons.
Multipennate.
Fascicles attach obliquely from many directions to several tendons.
What is the prime mover?
The agonist muscle that contracts to cause movement.
What is the antagonist muscle?
The muscle that stretches and yields to the efforts of the prime mover.
How are unwanted movements prevented as the prime mover crosses intermediate joints?
Synergist muscles contract and stabilize these joints.
What are fixators?
Muscles that stabilize the origin of the prime mover, and steady the proximal end of a limb while movements are occurring at the distal end.
What is a compartment?
A group of skeletal muscles and their associated blood vessels and nerves that all have a common function.
Name the muscles of the head that produce facial expressions.
Occipitofrontalis, orbicularis oris, zygomaticus major, buccinator, orbicularis oculi.
What is the action of the occipitofrontalis?
It covers the scalp. The frontal belly of the muscle draws the scalp anteriorly to raise the eyebrows and wrinkle the forehead skin. The occipital belly of the muscle draws the scalp posteriorly.
What is the action of the orbicularis oris?
It covers the mouth, and it works to close and protrude the lips, and compress the lips against the teeth.
Which muscle is important for kissing and talking?
Orbicularis oris.
What is the action of the zygomaticus major?
It covers the mouth, and works to draw the angle of the mouth superiorly and laterally.
Which muscle is important for smiling?
Zygomaticus major.
What is the action of the buccinator?
It covers the mouth, and works to press the cheeks against the teeth and lips, keep food between teeth, and draw the corners of the mouth laterally.
Which muscle is important for whistling, blowing, sucking and chewing?
Buccinator.
What is the action of the orbicularis oculi?
It covers the orbits and eyebrows, and works to close the eyes.
Name the muscles of the mandible important for chewing and talking. Why are they called the muscles of mastication?
Masseter and temporalis. They move the mandible at the TMJ.
What is the action of the masseter?
It is the strongest muscle of mastication, and it works to elevate the mandible.
What is the action of the temporalis?
It works to elevate and retract the mandible.
What is the origin and insertion of the masseter?
Origin: maxilla and zygomatic arch. Insertion: angle and ramus of the mandible.
What is the origin and insertion of the temporalis?
Origin: temporal bone. Insertion: coronoid process and ramus of mandible.
Name the muscle of the neck that moves the head.
Sternocleidomastoid.
What is the origin and insertion of the sternocleidomastoid?
Origin: sternal head of manubrium and clavicular head of clavicle. Insertion: mastoid process of temporal bone and superior nuchal line of occipital bone.
What is the bilateral action of the sternocleidomastoid?
Flex cervical portion of vertebral column and extend head of atlanto-occipital joints.
What is the unilateral action of the sternocleidomastoid?
Laterally flex and rotate the neck and head.
What is the RMA of the sternocleidomastoid?
Elevate the sternum during forced inhalation.
Name the muscles of the abdomen.
Rectus abdominis, external oblique, internal oblique, transversus abdominis.
What is the action of the rectus abdominis?
Flex vertebral column and compress abdomen for defecation, urination, forced exhalation and childbirth.
What is the RMA of the rectus abdominis?
Flex pelvis.
What is the origin and insertion of the rectus abdominis?
Origin: pubic crest and symphysis. Insertion: cartilage of ribs 5-7 and xiphoid process.
What is the bilateral action of the external oblique?
Compress abdomen and flex vertebral column.
What is the unilateral action of the external oblique?
Laterally flex and rotate vertebral column.
What is the bilateral action of the internal oblique?
Compress abdomen and flex vertebral column.
What is the unilateral action of the internal oblique?
Laterally flex and rotate the vertebral column.
What is the action of the transversus abdominis?
Compress abdomen.
What is the insertion of the transversus abdominis?
Insertion: xiphoid process, lines alba and pubis.
Which muscles form the rectus sheaths?
The aponeuroses of the external oblique, the internal oblique, and the transversus abdominis?
What is the linea alba?
White tough and fibrous band that extends from xiphoid process of sternum to pubic symphysis.
Name the muscles of the thorax involved in breathing.
Diaphragm and intercostals.