lec 10A: muscular system

functions of muscles

• movement

• stability

• control of body openings

• heat production

• hormone secretion

• glycemic control

prime mover/PM (agonist)

muscle that produces most of the force of a movement

• contracts actively to drive the desired motion

ex: when biceps brachialis acts as the agonist during an elbow curl

anatgonist

muscle that opposes the prime mover

ex: the triceps brachii acts antagonist during elbow flexion

synergist

muscle that assists the prime mover

ex: the brachialis assits the biceps brachii during elbow flexion

fixator

stabilizer — prevents a bone from moving

ex: scapular fixators hold the shoulder blade steady while arm moves

anterior side does…

… flexion

posterior side does…

… extension

lateral to joint does…

…abduction

medial to joint…

… adduction

muscle location

bone or body region with which muscle associated

muscle shape

e.g. deltoid muscle (deltoid = triangle)

muscle size

e.g. maximus (largest), minimus (smallest), longus (long)

rectus

fibers run straight

transversus

fibers run at right angles

ex: transversus abdominis = deepest

oblique

fibers run at angles to imaginary dedfined axis

ex: external oblique = superficial

internal oblique w rectus abdominis = under ex. oblique

5 patterns of fascicle arrangement

• parallel

• fusiform

• circular (sphincters)

• convergent (triangular)

• pennate

muscle fascicles

strength of a muscle and the direction of its pull are determined partly by the orientation of its fascicles

• longer fibers produce greater range of motion

• power of muscle depends on its cross-sectional area

fusiform muscles

thick in the middle with fascicles converging on each tapered end (biceps)

parallel muscles

uniform width and parallel fascicles (sartorius)

triangular (convergent) muscle

broad at one end with fascicles convering on the other, narrower end (pectoralis major)

pennate muscles

feather shaped fascicles attach obliquely on a central tendon that runs full length of muscle

• unipennate

• bipennate

• multipennate

unipennate

fascicles approach tendon from one side

ex: extensor digitorum longus

bipennate

fascicles approach tendon from both sides

ex: rectus femoris

multipennate

bunches of feathers converge to single point

ex: deltoid

circular (sphincters) muscles

fascicles form rings around body openings and passages into the body

ex: eye (orbicularis oculi, mouth (orbicularis oris)

3 classes of levers

• first class lever (LFE)

• second class lever (ELF)

• third class lever (LEF)

fulcrum

in the body is the joint—balance

effort

the muscle

resistance

the weight of the body moved

first class lever (LFE)

the fulcrum located inbetween the effort and resistance (load)

ex: scissor

second class lever (ELF)

the resistance is inbetween effort and fulcrum

ex: carrying a wheelbarrow

third class lever (LEF)

the effort is inbetween resistance and fulcrum

ex: bicep curls/lifting your hand

muscles of facial expression

• zygomaticus

• orbicular oculi

• orbicularis oris

• platysma

zygomaticus

smile

orbicular oculi

closes eyelids

orbicularis oris

puckers lips

platsyma

pulls corners of mouth down

mm for chewing

• temporalis

• masseter

• pterygoids

• buccinator

temporalis

helps chewing

masseter

cheek

pterygoids

grinding your food — moving your jaw back and forth

buccinator

contrating your cheek—proventing food from catching in your teeth/gums

sternocleidomastoid

major head flexor

scalenes

group of 3 paired muscles located on the lateral sides of the neck

• middle

• anterior

• posterior

3 muscles anchor and move tongue

• genioglossus

• hyoglossus

• styloglossus

…glossus = tongue muscle

extrinsic tongue muscle

.

intrinsic tongue muscle

.

middle scalene

directly synchronzied relationship while sniffing

• primary muscle activated during forced nasal inspiration

transverse process of C1-C7

anterior scalene

bilaterally flexes the neck and rotates it uniaxially and elevates the first rib

C3-C6

posterior scalene

laterally flexes the neck to the same side and elevates the second rib

erector spinae/sacrospinalis

deep intrinsic back muscles (vertebral column)

• group prime movers of back extension and lateral bending

iliocostalis

most lateral

longissimus

inbetween iliocostalis and spinalis

spinalis

most medial

deep muscles of the thorax

• external intercostals

• internal intercostals

• diaphragm

intercostals

muscles between the ribs—-located in the 11 spaces between 12 ribs

external intercostals

more superficial muscles —- elevate ribs for inspiration (blow in)

internal intercostals

deeper muscles; aid forced expiration (blow out)

diaphragm

main muscle for respiration—sits on the 12th rib

• most important muscle in inspiration

• upper cevical innervation

breathe in: CONTRACTS
breathe out: RELAXES

valsalva maneuver

forcedful exhalation against a closed airway or glottis

used to:

• stop rapid heart rates

• ear and sinus pressure

• medical exams

• physical exertion

pelvic floor

pelvic diaphragm: MOST SUPERIOR

• levator ani

• cooccygeus

urogential diaphragm (most anterior):

• contains external urethral sphincter

levator ani

broad, funnel shaped muscle group that forms the main part of the pelvic floor and pelvic diaphragm

coccygenus

small triangular skeletal muscle located in the deep posterior pelvic floor

posterior extrinsic shoulder muscles

• trapeziues

  • upper

  • middle

  • lower

• rhomboids

upper trapezius

elevation of scap (shrug)

middle trapezius

retration of scap

lower trapezius

depression of scap

rhomboids

major and minor — retration and downward rotation

muscles crossing the shoulder joint

• pectoralis major

• latissimus dorsi

• deltoid

  • anterior fibers

  • middle fibers

  • posterior fibers

pectoralis major

adduction and flexion

• raising hand

latissimus dorsi

adduction and extension

• pull ups

anterior fibers

flexion: lifts and draws the arm forward

ex: push ups

middle fibers

abduction

ex: lat pull down

posterior fibers

extension

ex: bent over lateral raises

coracobrachialis

scapula and the brachiallis

rotator cuff muscles

stabilized the humerus into the glenoid

• supraspinatus

• infraspinatus

• teres minor

• subscapularis

supraspinatus

assists deltoid in abduction

ex: helps lift the arm away from the side of the body

infraspinatus

shoulder external rotator & stabilizes humeral head into glenoid cavity

ex: when you turn your forearm outward like opening a door

teres minor

shoudler external lateral rotator of the humerus at the shoulder joint

ex: reaching for your back pocket

subscapularis

shoulder internal rotator

ex: pulling the arm towards the body

brachialis

• palm down exercise: pull ups

• under the biceps

biceps brachii

• palm up exercises: chin ups

• enter in the radius

brahioradial

synergist and stabilizer

enters into the ulner

triceps brachii

prime mover of elbow extension:

• triceps brachii medius

• triceps brachii lateral

• triceps brachii longus

triceps brachii medius

posterior surface of the humerus — below radial groove

triceps brachii lateral

posterior surface of the humerus — above the radial groove

triceps brachii long

tubercle of the scapula

muscles of the forearm

• pronator teres

• supinator

pronator teres

and pronator quadratus pronate forearm — palms down

supinator

synergist with biceps brachii in forearm supination —- palms up