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two ways muscles can work as a system

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together or in opposition whatever one muscle (or group of muscles) does, another muscle (or group of muscles) undoes

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terms list

two ways muscles can work as a system

together or in opposition whatever one muscle (or group of muscles) does, another muscle (or group of muscles) undoes

as muscles shorten, the ______ moves toward the _______

insertion origin

approximately how many muscles are there in the human body?

600

function of muscles

-move body parts -move contents of organs (smooth and cardiac muscle) -maintain posture and prevent movement -communication (speech, expressions and writing) -control body openings -heat production

prime movers

provide the major force for producing a specific movement

antagonists

oppose or reverse a particular movement

synergists

-add force to a movement -reduce undesirable or unnecessary movement

fixators

synergists that immobilize a bone or muscle's origin

naming of muscles based on relative size

maximus (largest), minimus (smallest), longus (long)

naming of muscles based on direction of fibers

rectus (fibers run straight), transversus, and oblique (fibers run at angles to a defined axis)

naming of muscles based on number of origins

biceps (two origins) and triceps (three origins)

fascicles

the bundles of myocytes surrounded by the perimysium membrane see p 4

parallel fascicles

fascicles run parallel to the long axis of the muscle (e.g. sartorius)

fusiform fascicles

spindle-shaped muscles (eg biceps brachii)

pennate fascicles

short fascicles that attach obliquely to a central tendon running the length of the muscle (e.g. rectus femoris)

convergent fascicles

fascicles converge from a broad origin to a single tendon insertion (e.g. pectoralis major)

circular fascicles

fascicles are arranged in concentric rings (e.g. obicularis oris-muscles around mouth, eyes)

direct attachment of muscle

epimysium of muscle is continuous with periosteum of bone relatively uncommon (intercostal muscles)

indirect attachment of muscle

epimysium collects into a tendon or aponeurosis that attaches to periosteum via perforating fibers most common (biceps brachii, gastrocnemius, etc)

intrinsic muscles

contained within the region that is moved by their contraction

extrinsic muscles

move body parts outside of the region where they are found

lever

a rigid bar that moves on a fulcrum, or fixed point

effort

force applied to a lever

load

resistance moved by the effort

effort x length of effort arm (force x distance) =

load x length of load arm (resistance x distance)

power lever

lever that operates at a mechanical advantage

speed lever

lever operates at a mechanical disadvantage

first class lever

fulcrum between load and effort, speed lever

second class lever

load between fulcrum and effort, speed lever

third class lever

effort is applied between fulcrum and load, speed lever

epicranius (occipitofrontalis)

bipartite muscle consisting of the: frontalis, occipitalis, galea aponeurotica (cranial aponeurosis connecting frontalis and occipitalis)

frontalis and occipitalis have what motions

alternate actions of pulling scalp forward and backward

how many muscles are involved in lifting the eyebrows, flaring the nostrils, opening and closing eyes and mouth, and smiling?

what are the facial muscles innervated by

cranial nerve VII (facial nerve)

where do facial muscles insert

skin (rather than bone)

see muscle diagrams in notes

major head flexor

sternocleidomastoid

synergists to head flexion

suprahyoid and infrahyoid

lateral head movements are accomplished by

sternocleidomastoid and scalene muscles

head extension accomplished by

deep splines muscles and superficial trapezius

prime mover of back extension

erector spinae

erector spinae consist of:

three columns on each side of the vertebrae- iliocostalis, longissimus, spinalis

lateral bending of the back is accomplished by unilateral contraction of what muscles

erector spinae muscles (iliocostalis, longissimus, spinalis)

other deep back extensors include the

semispinalis muscles and quadratus lumborum

primary function of deep thoracic muscles is to

promote movement for breathing

external intercostals

more superficial layer that lifts the rib cage and increases thoracic volume to allow inspiration

internal intercostals

deeper layer that aids in forced expiration

diaphragm

most important muscle for inspiration at rest

what is the abdominal wall made up of?

four paired muscles (internal and external obliques, transversus abdominus, and rectus abdominus), their fasciae, and their aponeuroses

fascicles of the abdominal muscles run at what angles to one another, giving the abdominal wall added strength

right and oblique

what do the abdominal muscles do

-involved with lateral flexion and rotation of trunk -help promote urination, defecation, childbirth, vomiting, coughing, and screaming

prime movers of shoulder elevation

trapezius and levator scapulae

how many muscles cross shoulder joint and insert into humerus

prime mover of arm flexion

pectoralis major

prime movers of arm extension

latissimus dorsi and posterior fibers of the deltoid

prime movers of arm abduction

middle fibers of the deltoid

rotator cuff muscles

supraspinatus, infraspinatus, teres minor, and subscapularis

functions of rotator cuff muscles

main: to reinforce the capsule of the shoulder secondary: as synergists and fixators

prime mover of forearm extension

triceps brachii

chief forearm flexors

brachialis and biceps brachii

what does brachioradialis of forearm do?

acts as a synergist and helps stabilize elbow

what do muscles of anterior forearm do?

primarily flexors of the wrist and fingers

what do muscles of posterior forearm do?

primarily extensors of the wrist and fingers

where in the hand are there muscles?

in the palm of the hand (none on the dorsal side)

what do muscles of the hand do?

control precise movements (e.g. threading a needle) main abductors and adductors of fingers produce opposition

what is opposition?

movement of thumb toward little finger

what motions does the ball-and-socket hip joint permit

flexion, extension, abduction, adduction, circumduction, and rotation

most important thigh flexors

iliopsoas (prime mover), tensor fasciae latae, and rectus femoris

muscles that assist in thigh flexion

medially located adductor muscles and sartorius

thigh extension is primarily effected by

the hamstring muscles (biceps femurs, semitendinosus, and semimembranosus) forceful extension is aided by the gluteus maximus

sole extensor of the knee

quadriceps femoris

what muscles flex the knee

hamstring muscles

anterior muscles of the leg and their functions

tibialis anterior, extensor digitorum longus, extensor hallucis longus, and fibularis tertius primary toe extensors and ankle dorsiflexors

function of lateral compartment muscles of the lower leg

plantar flex and evert the foot

lateral muscles of lower leg

fibularis longus and fibularis brevis

function of posterior muscles of lower leg

flex foot and toes

posterior muscles of lower leg

gastrocnemius, soleus, tibialis posterior, flexor digitorum longus, flexor hallucis longus

function of foot muscles

help flex, extend, abduct, and adduct the toes support the arch of the foot

what is the single, dorsal foot muscle, and what does it do

extensor digitorum brevis extends toes

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