Excitability

the ability to respond to stimulus

Conductivity

electrical changes that travels along the plasma membrane opening voltage-gated channels

Contractility

contractile proteins within in the muscle slide past one another (sliding
filament)

Elasticity

ability to return to its original length

Extensibility

Lengthening of a muscle fiber

skeletal Muscle Functions

-Body Movement

-Maintenance of posture
-Protection and Support
-Regulating elimination
of materials (sphincters at orifices)
-Heat Production

Muscle Fiber

muscle cell

Fascicle

group of
bound muscle fibers

Myofibril

small tubules with in the muscle fiber that contain the contractile unit called
sarcomere

Connective Tissue Functions

-Protection

-Sites for distribution of blood vessels and nerves

-Attachment to the skeleton

3 Layers of Connective Tissue

-Epimysium

-Perimysium

-Endomysium

Epimysium

-Surrounds the whole muscle

-Dense irregular tissue

Perimysium

-Surrounds the fascicle

-Dense irregular tissue

-Contains lots of blood vessels and nerves

Endomysium

-Surrounds and electrically insulates each individual muscle fiber

-Areolar tissue

-Contains reticular fibers to help bind together muscle fibers

Tendon

-Thick cord like structure

-Formed by three layers of connective tissue

-Dense irregular tissue

-Attach muscle to bone

Aponeurosis

-A thin flattened sheet of dense irregular tissue

-Connects two muscle bellies

Muscle Fiber Structure

-Multi nucleated

-Special cell membrane

-Sarcoplasmic reticulum

-Myofibrils

-Myofilaments

-Sarcomere

Multinucleated

Myoblasts fuse to form a single muscle fiber

Satellite Cells

Myoblasts that do not fuse

-Remain in muscle tissue to repair damaged muscle tissue

Sarcolemma

Conducts electrical impulses

T-tubules

deep invaginations of the sarcolemma that extend into the skeletal muscle fiber to stimulate the sarcoplasmic reticulum

Sarcoplasmic Reticulum (SER)

Internal membrane complex that is similar to smooth ER

Terminal Cisternae

Sacs at the end of the SER that store calcium

Calcium pumps vs calcium channels

Pumps: Move calcium into SER

Channel: Move calcium out of SER

Calcmodulin and Calsquestrin

Proteins that bind calcium with the SER

Myofibrils

-Long, cylindrical structures that extend the length of the muscle fiber

-80% of the skeletal muscle volume

-Composed of the myofilaments

Myofilaments

-Contractile proteins that are bundled within the myofibrils

2 Types of Myofilaments

Myosin=thick

Actin=thin

Thick

-200 to 500 myosin proteins

-Myosin: globular head and elongated tail (golf club)

Thin

-Composed of 2 strands of actin protein

-Actin: 2 protein strands that are twisted around each other

Tropomyosin

regulatory protein that covers the myosin binding sites of actin until

Troponin

regulatory protein that binds with calcium to move tropomyosin off of the myosin binding sites of actin

Sarcomere

-Repeating units within the myofilaments

-The contractile unit

Z Disc

proteins that are positioned perpendicular to the myofilaments and serve as anchors for the thin filaments

-separates sarcomeres

I Bands

extend in both directions of a Z disc

-thin filaments only

-disappears during maximal contraction

A Band

central region that contains the entire
thick filament

-thin overlaps thick slightly

-does not change shape during contraction

H Zone

most central portion of the A band

-NO thin filament over lapping! Thick filaments only!

-disappears as well

M Line

thin transverse protein meshwork in the center of the H zone

-attachment for thick filaments

Connection (green coil on diagram)

extends from the Z disc to the M line through the core of each thick filament

-stabilizes thick filaments

-has coiled section to help with recoil; able to return to normal shape after contraction

Dystrophin

a complex protein that anchors myofibrils to other proteins with in the
sarcolemma that extend to the endomysium

GO OVER MUSCLE CONTRACTION STEPS!!!

Find them in slides on #33 and after that.

Skeletal Muscle Fiber Types

-Fast-twitch

-Slow-twitch

-Fast Glycolytic

Fast-twitch

-Anaerobic

-Larger in diameter

-Strength and speed

-Light in color

-Contains medium amounts of mitochondria and myoglbin

Slow-twitch

-Aerobic

-Small in diameter

-appear red

-contain lots of mitochondria and myoglobin

-endurance

Fast Glycolytic (anaerobic fibers)

-anaerobic

-largest fibers

-white in color

-contains few mitochondria or myoglobin

-short duration (sprinting and weight lifting)

Factors affecting tension

-length-tension relationship

-length-tension curve

Length-tension relationship

the amount of overlap of thick and thin filaments when the muscle begins its contraction

length-tension curve

muscle generates different amounts of tension dependent upon its length at the time of stimulation

Muscle Tension

resting tension in a muscle generated by involuntary nervous stimulation of the muscle

Muscle Fatigue

The reduced ability to inability of the muscle to produce muscle tension

Isometric contraction

contraction of a muscle where no movement is created

Isotonic contraction

muscle tension results in movement of the muscle

Concentric contraction

shortening of the muscle length

(Occurs when the muscle tension is greater than resistance)

Eccentric contraction

lengthening of the muscle

(Muscle exerts less force than needed to move the load)

Cardiac Muscle Cells

-Short

-Y branching

-1 or 2 nuclei

-striated

-joined by intercalated disc

Autorhythmic

Specialized muscle cells that are
responsible for repetitious, rhythmic
contractions

Compare smooth vs skeletal muscle

SMOOTH

-Thick filaments have myosin heads along entire length

-Myosin heads have a modification to latch-on to thin filament (latchbridging)

-NO troponin, instead has MLCK (myosin light-chain kinase) and myosin light chain phophatase

Compare smooth vs skeletal muscle

SKELETAL

-Thick filaments have myosin heads along the ends

-No latchbridging

-Has troponin

Compare smooth vs skeletal muscle

BOTH

-Calcium stimulates contraction

-Myosin uses ATP for power stroke

-Thin filament slides
past the thick filament