anatomy - muscular system

types of muscle

• skeletal

• smooth

• cardiac

skeletal muscle

made of skeletal muscle, nervous, blood & connective tissue

• found on skeleton

• voluntary

• striated

smooth muscle

• found in organs, skin, blood vessels, & other passages

• involuntary

• nonstriated

cardiac muscle

• found in the heart

• involuntary

• striated

• has intercalated discs

muscular system function

1. movement of the body (skeletal)

2. maintain posture (skeletal)

3. respiration (skeletal)

4. production of body heat (skeletal)

5. communication → talking, writing, facial expressions (skeletal)

6. constriction of organs & vessels (smooth)

7. contraction of the muscles of the heart (cardiac)

characteristics of muscle tissue

• contractility

• excitability

• extensibility

• elasticity

contractility

shorten or contract muscle

excitability

muscle responds to an electrical stimulus

extensibility

muscle can stretch beyond its normal limits & be able to contract

elasticity

ability to spring back to its original shape after being stretched

fascia

dense CT, separate & surround muscles

deep fascia

fascia around muscle & bone

tendon

attach muscle to bone

aponeuroses

sheet of fibrous tissue

tendon sheath

encloses tendon, synovial membrane-allows tendon to move with it

epismysium

closely surrounds skeletal muscle

perimysium

separate muscles into smaller sections

fasicles

bundles of skeletal muscle fibers (muscle cells) in each section

endomysium

CT that covers each muscle fiber

muscle fibers

each is single & elongated - 1-40mm long

sarcolemma

• cell membrane of muscle cell

• surrounds sarcoplasm (cytoplasm of muscle cell) - has nuclei & mitochondria

myofibrils

• parallel & threadlike in sarcoplasm

• role in muscle contraction

• made of thick & thin filaments

• ~1,000 per muscle fiber

• together form alternating light and dark bands of muscle fibers

thick filaments of muscle fiber

• made mostly of the protein myosin

• shaped like golf clubs (heads are called cross bridges)

thin filaments of muscle fibers

• made of globular actin together like pearls

• tropomyosin lies in grooves & are held in place by troponin molecule

sarcomere

repeating units of striations along each muscle fiber

I band

light band made of thin actin filaments

Z line

in center, hold I bands together

A band

dark band - myosin overlapping actin, relatively wide

H zone

lighter central region, only myosin (thick)

M line

center of sarcomere - protein holding thick filaments in place

Z line to Z line

sarcomere

cross bridges

project outward along length of filament

troponin

• protein

• 3 subunits attached to actin

tropomyosin

• rod shaped protein

• in grooves of actin

troponin-tropomyosin complex

tropomyosin is held by troponin in actin helix

sarcoplasmic reticulum

networks of tubules & sacs within sarcoplasm

• channels that surround each myofibril

sarcoplasm

• pumps calcium ions and stores them in the sacs

transverse tubules

• extend into sarcoplasm & contains extracellular fluid

• allow electrical impulses deep into muscle

cisternae

surrounds the t-tubules and forms a triad

skeletal muscle contraction

• movement of myofibrils

• actin & myosin slide past one another & shorten sarcomere

neuromuscular junction

• neuron

• axon

• motor neuron

motor neuron

control effector