MUSCLES

• http://www.gwc.maricopa.edu/class/bio201/muscle/mustut.htm

• http://www.meddean.luc.edu/lumen/meded/GrossAnatomy/dissector/mml/index.htm

THREE TYPES OF MUSCLES

• Cardiac

• Smooth

• Skeletal

PROPERTIES OF MUSCLES

• Ability to contract

• Extensibility – ability to be stretched

• Elasticity – ability to return it its original length

• Irritability – ability to receive and repord to stimuli

TERMS

• Myo – muscle

• Sacro - flesh

• Muscle fiber – individual muscle cell

SKELETAL MUSCLE

• Bundles of muscle fibers that are package to form the organ

CONNECTIVE TISSUE OF SKELETAL MUSCLE

• Warps or bundles up muscle fibers

• Provides support and strength to muscle

• Keeps muscles form being ripped apart under tremendous forces

PARTS OF MUSCLE FIBER

• Endomysium – connective tissue sheath that wraps each individual muscle fiber

• Perimysium – coarser fibrous membrane that surrounds several muscle fibers

• Fascicle – bundle of fibers• Epimysium – tougher layer of connective

tissue that covers many fascicles – covers entire muscle –

Epimysium

EPIMYSIUM

• Ends of it will blend into – Tendons– Aponeurosis – attaches muscles indirectly to

bones, cartilage or connective tissue

TERMS

Origin – muscle attaches to stationary bone

Insertion – muscle attaches to bone that moves

When muscle contracts, one bone moves and the other is stationary

MOVEMENT OF BODY PARTS

• Body part is moved by a group of muscles:– Prime mover– Synergists– fixators

• Antagonists - pairs that work opposite

• Tendon- connective tissue that attaches muscle to bone– Very tough – thus is gives muscles durability– Does not wear out next to rough projections of

bone– Usually tendon that passes over bony joint and

not muscle

• Muscles are arrange differently depending on where they are located

FUNCTIONS OF MUSCLES

• PRODUCE MOVEMENT

• MAINTAIN POSTURE

• STABALIZE JOINTS

• GENERATE BODY HEAT

COMPONENTS OF SKELETAL MUSCLE

• Saroclemma

• Sarcoplasmic reticulum

• Sarcoplasm

• sarcomere

Parts of Sarcomere

• Myofibril (fibril) 0 complex organelle composed of bundles of myofilaments. Fill the cytoplasm of muscles.

• Myofilaments – threadlike filaments – has alternating light and dark bonds - composed of 2 key proteins– Actin– myosin

PROTEINS OF MYOFILAMENTS

myosin

• Thick protein filament• Contains ATPase – splits ATP to generate

the energy needed for muscle contraction• Extends the entire length of the dark A

boand• Midpart is smooth• End are studded with projections called

myosin heads or cross bridges

actin

• Thin filament• Made up of contractile protein• Actin is anchored to the Z line• I band – 2 adjacent sarcomeres and contains

only actin• Actin does not extend into the middle of the

A band which makes the H zone appear lighter

• When contraction occurs – actin filament slide toward each other into the center of the sarcomeres

• Light zone disappears because actin and myosin totally overlap

SLIDING FILAMENT THEORY

• Relaxed muscle has regulatory proteins on the actin to prevent myosin from bending

• AP stimulates the sarcolemma of the muscle

• Ca ions are released from the sarcoplasmic reticulum

• Ca ions bind to the regulatory proteins on the actin

• This changes the shape and location of the regulatory proteins on the actin

• Binding sites on the actin become exposes• Myosin heads attach to the binding sites on

the actin (called cross bridge formation)• When heads attach, they snap toward center

of sarcomere (power stroke)• This pulls actin toward center of sarcomere• ATP provides Energy to release and recock

myosin heads

• Cross bridge is broken• Myosin head reattaches to another site

further along the actin (another cross bridge and power stroke)

• This is called walking of the myosin• AP ends• Ca ions reabsorbed by sarcoplasmic

reticulum

• Regulatory proteins return to their original shape and position

• Myosin can’t attach

• Muscle relaxes

MACROSCOPIC CONTRACTION

• Muscle cell - all or none response

• Thousands of muscle cells form the organ

• Skeletal muscle’s response is graded – different degrees of contraction

2 WAYS TO PRODUCE GRADED REPONSE

• 1 - Changing the speed of muscle stimulation

• 2 - Changing the number of muscle cells stimulated

Pat vs. slap

• If few cells (motor units) are stimulated, then the contraction of the muscle is slight.

• As more cells are stimulated, the grater the contraction

THE 5 GOLDEN RULES OF SKELETAL MUSCLE

ACTIVITY

• All muscles cross at least 1 joint

• The bulk of the muscle lies proximal to the joint crossed.

• All muscles have at least 2 attachments

• Muscles can only pull, they never push

• During contraction muscle moves toward the origion

DISEASES

• Tetanus

• Muscular dystrophy

• Duchenne muscular dystrophy

• Problems associated with steroid use.

• What is the proper way to lift a heavy object?

• Muscle twitch

• Bell’s palsy

• Inguinal hernia

• Muscle cramp

Pictures to label