1.02 Muscular System

Lecturer: Dr. Nilson Gelbolingo

longest muscle

sartorius

• runs from outside of the hip, down and across inside of the knee

• twists and pulls thigh outwards

smallest muscle

stapedius

• middle ear

biggest muscle

gluteus maximus

muscular system

1. consists of all the muscles of the body

2. made of different types of muscles and has several functions

3. majority: voluntary skeletal muscles

   • one specific type of tissue

muscle function

1. movement

   • muscles attach to move

   • occurs during contraction of muscles

   • muscles not attached to bone:

     • arrector pili

     • heart

     • gastrointestinal tract

2. stability

   • muscles attached to bones support the body and keep balance

   • tendons attach muscles to bones

   • tendons work with muscles to keep joints in place when body moves

   • correct shape and posture

3. protection

   • they cover most of skeleton

   • covers most of the internal organs

   • like a layer of padding that protects internal organs

4. temperature regulation

   • help body keep internal temperature

   • shivering = muscles rapidly contracting

     • changes chemical energy to thermal

     • released thermal energy help maintain temperature

   • human body must stay around 37 degree Celsius in order to function properly

properties of muscle

1. excitability

2. contractility

3. extensibility

4. elasticity

excitability

capacity of muscle to respond to a stimulus

contractility

ability of a muscle to shorten and generate pulling force

extensibility

muscle can be stretched back to its original length

elasticity

ability of muscle to recoil to original resting length after stretch

three types of muscles

1. skeletal striated muscles

2. cardiac striated muscles

3. smooth muscles (unstriated)

skeletal striated muscles

1. voluntary somatic muscles that features a striated appearance

2. makes up the gross skeletal muscles that form the muscular system

3. moves or stabilizes bones and other structures (such as the eyeballs)

4. type of activity: intermittent (phasic) contraction

cardiac striated muscles

1. involuntary visceral muscle with a striated appearance

2. forms most of the heart walls (myocardium) and adjacent portions of the great vessels (e.g. the aorta)

3. strong, quick, continuous rhythmic contraction

4. pumps blood throughout the circulatory system

5. single central nucleus

smooth muscles (unstriated)

1. involuntary visceral muscle that is non-striated (unstriated)

2. forms part of the walls of most blood vessels and hollow organs (viscera)

3. moves substances through vessels and organs via coordination, sequential contractions (pulsations or peristaltic contractions)

4. weak, slow, rhythmic, or sustained tonic contraction

skeletal muscle

1. commonly referred to as “muscles”

2. fleshly, reddish, contractile portions (belly)

3. composed of skeletal straited muscles

4. also have white noncontractile portions (tendons)

5. muscle length = distance between attachments

6. directly or indirectly attach to bones, cartilages, ligaments, or fascia

7. mostly are named on the basis of their functions or body attachments or positions or length

parts of skeletal muscle

1. origin: relatively fixed during contraction, proximally located

2. insertion: moves during contraction; distally located

tendon

1. fibrous, cord-like, noncontractile

2. composed of bundles of collagen fibers

3. surrounded by epi-tendineum

4. supplied by sensory nerve

5. minimal vascular needs

   • if tendons are injured, they heal very slow

6. tendon transfer & transplantation

aponeurosis

1. flattened sheet of fibrous tissue

2. composed of parallel bundles of collagen fibers

raphe

1. fibrous band; interdigitating fibers of aponeurosis

2. stretchable

example: myelohyoid raphe

naming of skeletal muscle

1. location of the muscle

2. shape of the muscle

3. relative size of the muscle

4. direction/orientation of the muscle fibers/cells

5. number of origins

6. location of attachment

7. action of the muscles

muscles named by shape

1. deltoid - triangle

2. trapezius - trapezoid, parallel sides

3. serratus - saw-toothed

4. rhomboideus - rhomboid, 4 parallel sides

5. orbicularis and sphincters - circular

muscles named by size

1. maximus (largest)

2. minimus (smallest)

3. longus (longest)

4. brevis (shortest)

5. major (large)

6. minor (small)

direction of fibers

1. rectus - straight (ex. rectus abdominis)

2. transverse

3. oblique

arrangement of fascicles

1. parallel: strap-like (ex. sartorius)

2. fusiform: spindle-shaped (ex. biceps femoris)

3. pennate: feather-shaped

   • unipennate

   • bipennate

   • multipennate

4. convergent (ex. pectoralis major)

5. circular (ex. sphincters)

number of origins

1. biceps (2)

2. triceps (3)

3. quadriceps (4)

named for origin and insertion

example: sternocleidomastoid

• origin: sternum + clavicle

• insertion: mastoid process of temporal bone

based on action

1. flexor carpi radialis: extensor carpi radialis) = flexes wrist

2. abductor pollicis brevis: adductor pollicis brevis = flexes thumb

3. abductor magnus = abducts high

4. extensor digitorum = extends fingers

muscle contraction

1. skeletal muscles function by contracting

2. they pull distal portion but never push

3. when muscle contracts and shortens = movement

types of muscle contraction

1. reflexive contraction

2. tonic contraction

3. phasic contraction (active)

reflexive contraction

1. response to a certain stimuli

2. automatic

3. not voluntarily controlled

example: respiratory movement of diaphragm, tendon reflex

tonic contraction

1. slight contraction (muscle tone)

2. does NOT produce movement or active resistance

3. gives muscle certain firmness assisting joint stability and posture maintenance

4. keep muscle ready to respond to a stimuli

phasic contraction (active)

1. isotonic contraction

2. isometric contraction

isotonic contaction

muscle length changes in relation to the movement

• concentric

• eccentric

isometric contraction

muscle length remains the same; no movement

concentric contraction

1. movement occurs as a result of the muscle shortening

2. force generated by muscles EXCEEDS force of gravity

example: lifting a cup, pushing door, striking a blow

eccentric contraction

1. contracting muscles lengthen

2. force generated become less than gravity

example: walking, running, setting objects down

specific muscle functions in bodily movements and positions

1. prime mover (agonist)

2. fixator

3. synergist

4. antagonist

prime mover (agonist)

1. main muscles for producing movement

2. contacts concentrically (shortening)

example: brachialis

fixator

1. steadies proximal part of limb while movement are occurring in distal part

2. isometric contraction

example: rhomboids holds scapula firmly in place

synergist

1. complements action of prime mover by assisting directly or indirectly for a particular movement

example: biceps brachii

antagonist

1. muscle that opposes action of another muscle

2. eccentrically contract

example: triceps brachii

paralysis

loss of movement

paresis

weakness of movement

paralysis/paresis

1. loss of power of movement

2. muscles are unable to contract

3. damage to neural pathways:

   • upper motor neuron

   • lower motor neuron

4. s/sx:

   • inability to wrinkle brow

   • dropping eyelid

   • inability to close eye

   • inability to puff cheek

   • asymmetrical smile

   • drooping corner of mouth

muscular spams

1. spontaneous/involuntary contraction

2. may be:

   • localized = commonly caused by a “muscle pull”

   • generalized = seen in tetanus and epilepsy

3. commonly seen in atheletes

4. factors:

   • infants

   • young children

   • people over age of 65

   • certain medications

   • being overweight

   • overexerting during exercise

disuse atrophy

1. muscles are not used for a long time = thin and weak

2. reduces in size (muscle wasting)

3. seen in paralysis (generalized debility)

hypertrophy

excessive use of a particular muscle results in better development for hypertrophy (body builders and athletes)

regeneration

1. capable of limited regeneration

2. large regions damaged - regeneration does not occur and replaced by CT

muscular dystrophy

1. inherent defect in cell membrane of muscle

2. rupture of muscle fibers

3. X-linked recessive defect

example: duchene’s and bakers