Notes: Functional Anatomy of Muscles

1. What are the six functions of the muscular system?

Produce skeletal movement By contraction of muscle

fibers True of all = cardiac,

smooth, skeletal Maintain posture/body

position Some muscles are always

“on” – fight against gravity Support Tissues/Stabilize

joints Shoulder joint is VERY

unstable – needs muscle and tendons to keep it steady

1. What are the six functions of the muscular system?

Maintain Body Temp/Generate heat Large amount of energy is

given off as heat during muscle contraction

Guard Entrances and Exits Openings of tracts

encircled by skeletal muscles

Store Nutrient Reserves Muscle broken down when

there is an inadequate amount proteins

2. What are the 3 types of connective tissues found in muscles? What structure does each one surround? Epimysium

Surrounds entire skeletal muscles

separates muscles from tissues and organs

Perimysium Surround

muscle fascicle Endomysium

Surround muscle fibers

3. Components of a skeletal muscle fiber:

Sarcolemma The cell

membrane of a muscle fiber

Sarcoplasm Cytoplasm of a

muscle fiber Transverse Tubules

Narrow tubes continuous with sarcolemma

Passageways that the action potential travels through

3. Components of a skeletal muscle fiber:

Myofibrils Bundles of

myofilament Separated by

sarcoplasmic reticulum

Contractile orgalles of skeletal muscle

Extend entire length of muscle fiber

3. Components of a skeletal muscle fiber:

Myofilaments Bundles of

myofilament Separated by

sarcoplasmic reticulum

Contractile orgalles of skeletal muscle

Extend entire length of muscle fiber

Myofilaments Contractile proteins of the muscle Thick and thin filaments overlap

each other in a pattern that creates striations I band – only thin filaments

Figure 6.3b

3. Components of a skeletal muscle fiber:

3. Components of a skeletal muscle fiber:

Myofilaments continued

The protein fibers that actually compose the myofibrils

Thick filaments Made of protein

myosin Cross bridges link

to thin filaments Thin filaments

Made of protein actin

Sarcoplasmic reticulum (SR) fluid-filled system of

membranous sacs surrounds each

myofibril stores Ca2+

Release of calcium into Sarcoplasm signals the beginning of a muscle contraction Figure 6.3a

4. What is the sarcoplasmic reticulum? What is its role in a muscle contraction?

Basic functional unit of a myofilament A band (darker) – extends the entire

length of thick filaments I band (lighter) – thin filaments thin

ments Proteins that stabilize the filaments Proteins that regulate the interaction

between filaments

5. What is a sarcomere? What are the four things it contains?

A band (dark band)

M-line: central part of the

thick filament stabilize position of

thick filament H-zone: Contains thick

filaments only Zone of overlap: Where the think and

thick filaments overlap

6. Components of a sarcomere:

I-band (light band)

Z-lines: Boundaries

between sarcomere

Titin: Elastic protein Keeps filaments in

proper alignment Helps muscle fiber

resist extreme stretching

6. Components of a sarcomere:

During a muscle contraction thin filaments are sliding toward the center of each sarcomere

Sliding occur within every sarcomere in a muscle fiber

7. What is the sliding filament theory?

When a skeletal muscle fiber contracts

The H zones and I bands get smaller

The zones of overlap get larger

The Z lines move closer together

The width of the A band remains constant

7. What is the sliding filament theory?