Muscles Flashcards
muscles: function
- provide force for movement
skeleton: function (3)
- support the body
- protect delicate body tissues
- provide levers for muscles to act on to produce movement
what happens when a muscle contracts
- it shortens and applies force by PULLING
skeletal muscles attachment sites
- origin
- insertion
skeletal muscles attachment sites: origin
- relatively fixed structure
skeletal muscles attachment sites: insertion
- relatively mobile site
antagonistic pairs
- pairs of muscles that pull the same body part in opposite directions
flexion (2)
- to bend one part relative to another about a joint
- decreases the angle between these two parts
extension
- to straighten one part relative to another about a joint
- increases the angle between these two parts
levators
- elevate (raise) a body part
depressors
- depress (lower) a body part
adduction (2)
- to move a body part towards the midline of the body
- to elevate the lower jaw, closing the mouth
abduction (2)
- to move a body part away from the midline of the body
- to depress the lower jaw, opening the mouth
protractors (2)
- projection of a part away from its base
- movement of an appendage in the anterior direction
retractors (2)
- withdrawal of a body part: pulling it back closer to its base
- movement of an appendage in the posterior direction
classification of skeletal muscles (4)
- branchiomeric
- hypobranchial
- axial
- appendicular
trunk somites
- myotome of trunk somites develop into axial and appendicular muscles
anterior somites (2)
- grow ventrally and anteriorly to form hypobranchial muscles
- ventral to pharyngeal slits
somitomeres
- epimere mesoderm forms connected clusters in the head
- develop into branchiomeric muscles
terrestrial locomotion: propulsive stroke (2)
- foot contacts the ground
- limb moves from anterior to posterior (retraction) propelling body forward
terrestrial locomotion: recovery stroke (2)
- foot is lifted (no contact with ground)
- limb moves from posterior to anterior (protraction), back into position for another propulsive stroke
sprawled limb posture (2)
- amphibia, testidunata, lepidosauria, and crocodilia
- limbs positioned laterally
erect limb posture (2)
- mammalia, aves
- limbs are positioned directly under the body
terrestrial locomotion: sprawled limb posture (3)
- walk or run with lateral undulations of the body, using feet as pivot points
- recovery stroke requires an overarm swing for each limb
- limb movement is both anterior/posterior and dorsal/ventral
terrestrial locomotion: erect limb posture (2)
- recovery stroke achieved with a pendulum-like swing
- limb movement is generally restricted to anterior/posterior direction
what posture is more efficient for terrestrial locomotion
- erect posture: higher proportion of energy used for limb movement will contribute to propelling the body forward than to moving the limbs back into position
what determines the amount of force generated by skeletal muscles (2)
- cross-sectional area of the muscle is directly related to force
- does not depend on length
axial muscles
- muscles of the body wall organized into myomeres separated by mysepta
- epaxial (T) and hypoaxial (B) separated by horizonatal septum
- chond, actin: attach to vetebral column (sarc: noto) to produce lateral udulations of body = powerful thrust to propel body forward in H2O
- tetrapod (sprawled): both appen and axia contributw to locomoton
- tetrapod (erect): epaxial (pull neural spines to stabilize column to bridge weight of internal organs to legs)
- tetrapods (hypaxial): form large portion of body wall and help protect internal organs
- amniotes: aspiration pump to expand/compress flexible ribcage
appendicular
- chond + actin = extend from gridles to fins; each find has forsal ad ventral muscle; smaller cross-sectional area as they are used for stability and steering more than axial muscles
- tetrapods: limbs provide main source of propulsive force, so relatively large; pectoral and pelvic adductor and abductor masses divded into many distinct muscles allowing for highly maneuverable limbs
- aves: muscle bunched proximally, connected to distal ends by long tendons; keep muscle mass close to centre of gravity for flight stability; muscles of pectoral girdle and forelimb relatively large (pectoralis attaches to sternum, adducts wings);
