Chapter 11: The Muscular System Flashcards
Muscular System
(Relationship: bones and skeletal muscles)
Voluntary controlled muscles of your body.
Skeletal muscles produce movements by exertion on tendons which in turns pulls bones and other structures (skin).
Muscle cross at least one joint that is attached to articulating bones that form joints.
Origin
Attachment of a muscles tendon to a stationary bone.
Insertion
Attachment of the muscles other tendons to the movable bone.
Belly
Fleshy portion of the muscle between tendons
Actions
Main movement in muscles that occur when muscles contract.
Reverse Muscle Action (RMA)
Certain muscles have this capability.
During specific movements of the body the actions of muscles are reversed. The position of the origin and insertion of the specific muscle are switched.
Lever Systems and Leverage for Movement
Bones act as levers and joints function as fulcrums of these levers.
Lever
A rigid structure that can move around a fixed point.
Falcrum
Symbolized by F inside a triangle.
Fixed point a lever moves around.
Lever System Action
A lever is acted on at 2 different points by 2 different forces:
The effort (E): causes movement
The load (L inside blue square): or resistance, opposes movement
The effort is the force exerted by muscle contraction.
The load is typically the weight of the body part that is moved, or some resistance that the moving body part is trying to overcome.
Mechanical Advantage
A small effort is required to move large loads over a small distance due to the load being closer to the fulcrum and the effort farther from the fulcrum.
Mechanical Disadvantage
A large effort is required to move a small load but at greater speed is due to the load is farther from the fulcrum and the effort is applied closer to the fulcrum.
Lever Categories
Categorized into 3 types according to the positions of the fulcrum, the effort and the load.
1. First Class Levers
2. Second Class Levers
3. Third Class Levers
First Class Lever
(think seesaw)
fulcrum is between the effort and the load. Can produce both mechanical advantages/disadvantages depending on wether the effort or load is closer to the fulcrum.
Second Class Levers
(think wheelbarrow)
The load is between the fulcrum and the effort. Always produce mechanical advantage as the load is always closer to fulcrum than the effort.
This type of arrangement gives up speed and range of motion to produce force. This type creates the most force. This lever is uncommon in the body.
Third Class Levers
(Think a pair of forceps)
Effort is between the fulcrum and the load.
Always produce mechanical disadvantages as the effort is always close to the fulcrum than the load.
This arrangement favors speed and range of motion over force. Most common levers in the body.
Fascicles
Bundles of skeletal muscle fibers within a muscle cells.
Patterns of Facicles
Can form 5 patterns with respect to the tendons
1. Parallel
2. Fusiform (spindle shaped)
3. Circular
4. Triangular
5. Pennate
Parallel Fascicles
Are parallel to longitudinal axis of muslce
Terminate at either end in flat tendons
Have fewer fascicles but have long fibers that extend the length of the muscle giving them a greater range of motion but less power.
(Ie) sternohyoid muscle
Fusiform Facicles
Nearly parallel to longitudinal axis of muscle
Terminates in flat tendons
Muscle tapers towards tendons where diameter is less than at belly.
(ie) digastric muscle
Circular Facicles
In a concentric circular arrangements
Forms sphincter muscles that enclose an orifice (opening).
( ie) orbicularis muscle
Triangular Fascicles
Spread over broad area
Converge at thick central tendon
Gives muscle a triangular appearance
( ie) pectoral is major muscle
Pennate Fascicles
Short fascicles in relation to total muscle length
Tendons extends nearly entire length of muscle giving them greater power but smaller range of motion.
1. Unipennate: arranged on only one side of tendon
(Ie) extensor digitorum longus muscle
2. Bipennate: arranged on both sides of centrally positioned tendons
(Ie) rectus femoirs muscle
3.Multipennate: attached obliquely from many directions to several tendons.
(Ie) deltoid muscle
Prime Mover - Producing Movement
Most muscles are arranged in opposing pairs at joints.
Within opposing pairs one muscle called prime mover (agonist) contracts to cause an action.
Antagonist- Producing Movement
Muscle action that stretches and yields to the effects of the prime mover.
Synergists
Prevents unwanted movements at intermediate joints or to otherwise aid the movement of the prime mover.
These muscles contract and stabilize the intermediate joints.
Fixators
Muscles in a group that stabilize the origin of the prime mover so that the prime mover can act more efficiently.
Steadies the proximal end of a limb while movement occurs at the distal end.
Limb Compartment
A group of skeletal muscles, their associated blood vessels/nerves all of which have a common function.
Seven Features used in Naming Skeletal Muscles
Know the names of a muscle will then give you clues about its features.
1. Direction: orientation of the muscle fascicles relative to the body’s midline
2. Size: Relative size of the muscle
3. Shape: Relative shape of the muscle
4. Action: Principle action of the muslce
5. Number of origin: Number of tendons of origin
6. Location: Structure neat which a muslce is found
7. Origin and Insertion: Sites where muscle originates and inserts.
Frontal Belly
Scalp Muscle: Occipitofrontalis
Draws scalp anteriorly, raises eyebrows and wrinkles the skin of the forehead.
Occipital Belly
Scalp Muscle: Occipitofrontalis
(Back of Head)
Draws scalp posteriorly
Orbicularis Oris
Mouth Muscle
Closes and protrudes lips, as in kissing.
Compresses lips against teeth and shapes lips durning speech.
Zygomaticus Major
Mouth Muscle
Draws angle of mouth superiority and laterally, as in smiling.
Buccinator
Mouth Muscle
Presses cheek against teeth and lips as in whistling, blowing and sucking.
Draws corner of mouth laterally and assists in mastication (chewing) by keeping food between the teeth.
Orbicularis Oculi
Orbit and Eyebrow Muscle
Closes eyes.
Muscles of Mastication
Muscles that move the mandible at the temporomandibular joint.
4 pairs of muscles (insert at the mandible) are involve and account for strength of bite:
Masseter: Most powerful closer of the jaw
Temporalis: powerful closer
Medial Pterygoid: powerful closer
Lateral Pyergoid: moves the mandible from side to side to help grind food and opens the mouth.
Masseter
Mastication and Speech
Strongest closer of jaw
The Temporalis is the synergistic, assists by reducing unnecessary movements.
Origin: Maxilla and zygomatic arch
Insertions: angle and ramus of mandible
Action: elevated mandible as in closing the mouth
Rectus Sheaths
Enclose the rectus abdominis muscles.
Formed by aponeuroses (stealth like tendons) of external/internal oblique and transversus Abdominis.
Lines Alba
Formed by sheaths that meet at the midline of the abdomen.
A tough, fibrous band that extends from the xiphoid process of the sternum to the pubic symphysis.
In latter stages of pregnancy, these muscle stretch to increase the distance between the rectus abdominis muscles.
Diaphragm
Most important muscle that powers breathing.
Action: contraction of diaphragm causes it to flatten and increases vertical dimension of thoracic cavity, results in inhalation.
Relaxation of diaphragm causes it to move superiorly and decreases vertical dimension of thoracic cavity, results in exhalation
Central Tendon
A strong aponeurosis that is located neat the center of the muscular portion of diaphragm.
Intercostals
Other muscles that are invokes in breathing, span the intercostal spaces between ribs.
External Intercostals
Muscle of thorax, assists in breathing
11 pairs occupy superficial layer of breathing muscles
Contraction elevates ribs and increases (expand) anteroposterior and lateral dimensions of thoracic cavity, results in inhalation.
Relaxation depresses ribs and decreases anteroposterior and lateral dimension of thoracic cavity, results in exhalation
Internal Intercostals
Muscles of Thorax, assist in Breathing
11 pairs, occupy the intermediate layer of intercostal space.
Action: contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimension of thoracic cavity during forced exhalation.
Oblique Muscles
The internal and external oblique muscles can act singly (unilaterally) or together (bilaterally).
Singly: can rotate and laterally flex the vertebral column.
Together: function to compress the abdomen and flex the vertebral column.
Sartorius
Is superior to the acetabulum. This muscle weakly flexes the leg at the knee joint.
Scalenes
Accessory muscles of inspiration. Muscles are located on lateral area of neck.
Responsible for elevation during respiration.
3 gluteal Muscles- superficial to deep
Gluteus Maximus
Gluteus medius
Gluteus minimus
Trapezius
Function aids to elevate the scapula and shrug the shoulders.
Serratus Anterior
Known as boxer muscle.
Responsible for move int the scapula when throwing a punch. On anterior lateral surface of ribs.
Brixism
Grinding of teeth
Causes hypertrophy of Masseter.
