Ch 9 Muscles Part 1 Flashcards
Muscle Tissues All contractile muscles
Skeletal, Smooth, Cardiac
Muscle action and interaction
Pull, Never push
what one group does one undoes
Skeletal muscles produce movements by exerting force on tendons. Tendons attach to and pull on bones, and movement occurs
Muscle functional group
Prime mover (agonist)- major responsibility for producing specific movement
Antagonist - Opposes or reverses particular movement
Prime mover and antagonist on opposite sides of joint across which they act
Skeletal Muscle functional group
Synergist- helps prime movers
Adds extra force to same movement
Reduces undesirable or unnecessary movement
Fixator- Synergist that immobilizes bone or muscle’s origin
Gives prime mover stable base on which to act
Same muscle may be
Prime mover of one movement
Antagonist for different movement
Synergist for third movement
Origin and Insertion
Most muscles cross at least one joint and are attached at the articulating bones
When a muscle contracts, it draws one articulating bone toward the other
Origin – the attachment to the stationary bone
Insertion – the attachment to the moveable bone
Naming Skeletal Muscle
Muscle location- bone or body region with which muscle associated
Muscle shape- deltoid muscle (deltoid = triangle)
Muscle size- maximus (largest), minimus (smallest), longus (long)
Direction of muscle fibers or fascicles-
rectus (fibers run straight), transversus (fibers run at right angles), and oblique (fibers run at angles)
Number of origins- Biceps (2 origins) and triceps (3 origins)
Location of attachments- named according to point of origin and insertion (origin named first)
Muscle action- named for action they produce (flexor or extensor)
Muscle Mechanic
Additional factors contributing to muscle force and speed
- Fascicle arrangement
- Lever systems
Most common patterns – circular, convergent, parallel, fusiform, pennate
Important of Fascicle arrangement
Muscle fibers are arranged in parallel bundles within fascicles but the arrangement of fasciculi in relation to the tendon can vary
Fascicular arrangement is correlated with:
The amount of power of a muscle can produce
The range of motion a muscle can produce
Arrangement of Fasicle
Determines muscle’s range of motion-
Amount of movement when muscle shortens
Determines muscle’s power-
Long fibers more parallel to long axis shorten more; usually not powerful
Power depends on number of muscle fibers-
Bipennate, multipennate muscles have most fibers shorten little but powerful
Muscle Mechanic Lever System
Components of lever system
Lever—rigid bar (bone) that moves on a fixed point called fulcrum (joint)
Effort—force (supplied by muscle contraction) applied to lever to move resistance (load)
Load—resistance (bone + tissues + any added weight) moved by the effort
Bones serve as levers and joint serve as fulcrums
The lever is acted on by:
-Resistance
-Effort
Lever: Power vs Speed
Levers allow given effort to move heavier load; move load farther or faster
Depends on fulcrum position relative to load and effort
Mechanical advantage (power lever) – load close to fulcrum; effort far from fulcrum Small effort can move large load
Mechanical disadvantage (speed lever) – load far from fulcrum; effort close to fulcrum Load moved rapidly over large distance; wide range of motion
Classes of Levers
Effort farther than load from fulcrum = lever operates at mechanical advantage
Effort nearer than load to fulcrum = lever operates at mechanical disadvantage
Major Skeletal Muscles of the Body
> 700 in body; grouped by function and location
Information for each muscle:
Shape
Location relative to other muscles
Origin and insertion—usually a joint between origin and insertion
Actions—insertion moves toward origin
Innervation—name of major nerve that supplies muscle
Muscles of the Head
Two groups
- Muscles of facial expression
- Muscles of mastication and tongue movement
Muscles of Facial Expression
Insert into skin
Important in nonverbal communication
All innervated by cranial nerve VII (facial nerve)
Muscles of Facial Expression: The Scalp
Epicranius (occipitofrontalis)
Bipartite muscle consisting of
Galea aponeurotica—cranial aponeurosis connecting two bellys
Frontal belly; occipital belly
Have alternate actions; pull scalp forward and backward
Muscles of Mastication
Four pairs involved in mastication;
all innervated by cranial nerve V (trigeminal nerve)
Prime movers of jaw closure Temporalis and masseter Grinding movements Medial and lateral pterygoids Chewing role - holds food between teeth Buccinator
Muscles of Mastication and Tongue Movement
Three muscles anchor and move tongue Genioglossus Hyoglossus Styloglossus All innervated by cranial nerve XII - hypoglossal nerve
Muscles of the Anterior Neck and Throat
Two groups -
- Suprahyoid muscles
- Infrahyoid muscles
Most involved in swallowing
Suprahyoid Muscles of the Anterior Neck and Throat
Elevate the hyoid and widen the esophagus during swallowing
Digastric, geniohyoid, stylohyoid, mylohyoid
Infrahyoid Muscles of the Anterior Neck and Throat
Four deep muscles involved in swallowing (move hyoid bone and larynx)
Form floor of oral cavity
Anchor tongue
Move hyoid bone and larynx
Sternohyoid, sternothyroid, thyrohyoid, omohyoid
Muscles of the Neck and Vertebral Column
Two functional groups:
- Muscles that move head
- Muscles that extend trunk and maintain posture
Sternocleidomastoid—major head flexor
Suprahyoid and infrahyoid—synergists to head flexion
Sternocleidomastoid and scalenes—lateral head movements
Splenius capitis and cervicis portions - head extension, rotation, and lateral bending
Semispinalis capitis—synergist with sternocleidomastoid
Muscles of the Neck and Vertebral Column: Trunk Extension
Deep (intrinsic) back muscles- Erector spinae (sacrospinalis) group—prime movers of back extension and lateral bending
Iliocostalis
Longissimus
Spinalis
Semispinalis and quadratus lumborum—synergists in extension and rotation
