lecture 11 Flashcards
skeletal muscle anatomy
what is muscle origin also known as?
proximal attachment
what is muscle insertion also known as?
distal attachment
define muscle origin?
usually the proximal end of the muscle which remains fixed during muscular contraction
define muscle insertion?
usually the distal end of the muscle which is movable
define agonist and give an example?
the main muscle responsible for producing a specific movement of the body. It contracts concentrically to produce the desired movement, doing the most work required. In most movements there is a single prime mover but some movements involve two prime movers working in equal measure
define antagonist and give an example?
a muscle that opposes the action of another muscle. A primary antagonist directly opposes the prime mover but synergists may also be opposed by secondary antagonist. As the active movers concentrically contract to produce a movement, antagonists eccentrically contract relaxing progressively in coordination to produce a smooth movement. Examples include quadriceps and hamstrings in the leg and the biceps and triceps in the arm.
define synergists and give an example?
complements the action of a prime mover; examples include the brachioradialis and brachialis which assist biceps flexion
May be active
define fixator and give an example?
a muscle movement that stabilizes proximally and agonist and joint that muscle origin spans in order to assist agonist function most effectively. Like for a biceps curl, fixators are rotator cuff muscle movements which stabilize to protect shoulder joint
describe the hierarchy of muscle organization from cell to organ level
so muscle attach to bone by a connective tissue sheath called a tendon and this tendon is the coalition of connective tissue that surrounds each of the groups of muscle fibers that make up a muscle. A collection of muscle fibers then makes up a muscle. Nerves innervate the muscle fibers and it becomes a motor unit because when the motor unit fires, the muscles that are plugged into it contract
what are the five basic fascicle arrangements that give rise to the basic shape of a muscle?
circular, convergent, parallel, fusiform, and pennate
what is the circular fascicle arrangement?
these surround a body opening or orifice constricting it when contracted, examples include the obicularis oculi which closes the eyelid
what is the convergent fascicle arrangement?
these arise from a broad area and converge to form a single tendon like the pectorals major
what is the parallel fascicle arrangement?
muscles that run parallel to each other and can sometimes be called strap muscles. These are long muscles that cause large movements that are not very strong but have good endurance. Examples include the sartorius and sternocleidomastoid
what is the fusiform fascicle arrangement?
spindle shaped with a round, thick belly and tapered end like the biceps brachii
what is the pennate fascicle arrangement?
feather liken the arrangement of their fascicles and may be unipennate, bipennate, or mulitpennate like the extensor digitorum longus (unipennate), rectus femoris (bipennate), and the deltoid (mulipennate)
what are the three types of muscle contraction?
reflexive, tonic, and phasic contraction
what is reflexive contraction?
when aspects of the skeletal muscle are automatic and not voluntarily controlled
what is tonic contraction?
no movement produced or active resistance but gives the muscle a certain firmness, assisting the stability of joints and the maintenance of posture while keeping the muscle ready to respond to stimuli
what are the subtypes of phasic contraction?
isotonic and isometric contraction
what are the two types of isotonic contractions?
concentric contraction and eccentric contraction
what is isotonic contraction?
the muscle changes length in relationship to production of movement
what is isometric contraction?
in which the muscle length remains the same-no movement occurs but the force is increased above tonic levels to resist gravity or other antagonistic forces
what is concentric contraction?
movement occurs as a result of the muscle shortening
what is eccentric contraction?
in which a contracting muscle lengthens undergoing a controlled and gradual relaxation which continually exerting a diminishing force
how is a muscle attachment defined?
by its origin and insertion
what is the attachment site that remains stationary when muscle contracts?
origin
what is the attachment site that moves when muscle contracts?
insertion
how do muscles produce movement?
attachments and contractions
the belly of the muscle is not necessarily positioned on that bone, T/F?
T
what percent do muscles shorten?
70% resting length
how do we group muscles by function?
agonists, antagonists, synergists, fixators
what is a group of muscles the work together to produce a specific movement?
agonists
what is a prime mover?
most forceful muscle of an agonist grouping
what is an antagonist? name an example?
a muscle or muscle group that produces opposite action; biceps and triceps
what are synergists? name examples
muscles that prevent unwanted movement in a joint (often an intermediate joint) when muscle contracts, flexion of fingers and unilateral and bilateral action of sternocleidomastoids
what are fixators? example?
muscles that stabilize origin of the primary mover; muscles that prevent movement of scapula allowing biceps to work more efficiently
what is the hierarchy of muscle organization?
muscle cell becomes a fiber grouped together become a fascicles which when grouped together become a skeletal muscle
all fascicles parallel to long axis of muscle terminating at both ends in a flat tendon
parallel
fascicles roughly parallel to long axis with muscle tapering toward tendons
fusiform
fascicles in concentric arrangement»_space; can close an opening
circular
fascicles spread over a broad origin and converge at a thick central tendon
convergent
short fascicles in comparison to length of muscle and tendon courses nearly the entire length of muscle
pennate
name the three types of pennate?
unipennate, bipennate, multipennate
fascicles arranged on only 1 side of tendon
unipennate
fascicles arranged on both sides of a central tendon
bipennate
fascicles arranged around multiple tendons that insert into multiple directions
multipennate
