AP class one

first lecture, need to do last page of notes still!

what are the major fxns of skeletal muscle?

produce skeletal movement, maintain posture, body position, balance, supports soft tissue, guard entrance and exits (sphincters), helps maintain normal body temp, and provides nutrient reserves

how does skeletal muscle produce movement

skeletal musccle contractions pull on tendons to move bones

how does muscle maintian posture, body position and balance

continous isometric contractions create constant tension (muscle tone) that stabilizes joints against gravity

waht soft tissue is supported by skeletal muscle?

abdominal wall, pelvic floor, shields tissue from injury

how does skeletal muscle guard sphincters?

provide voluntary control over swallowing, urination, defecation

how does skeletal muscle help to maintain normal body temp?

heart relaxed from 5m contractions

how does skeletal muscle provide nutrient resources?

during starvation or inadequate protein/caloric intake, contractile proteins are broken down into amino acids to be used for energy or converted into glucose

4 major components of skeletal muscle

1 skeletal muscle tissue 2 connective tissue 3 blood vessels 4 nerves -allow 4 properties that contribute to homeostasis

electrical excitability

helps to prepare action potentials

contracility

because of action potentials muscle will contract (shorten)

extensibility

muscle tissue naturally sticks without damage

elasticity

skeletal muscle tissue returns to original shape after contractions

what are the connective tissue components?

1. Epimysium (surrounds the entire muscle)

2. Perimysium (surrounds muscle fascicles/bundles of fibers)

3. Endomysium (surrounds individual muscle fibers)

epimysium

dense layer of collagen fibers, surrounds entire muscle, helps to seperate skeletal muscle from surrounding tissues and organs, connected to fascia

fascia

holds muscle of similar fxn together

tendons

join muscle to bone

ligaments

join bone to bone

fascicles

bundles of muscle fibers seperated from one another by the perimysium

preimysium contain and do:

collagen, moves blood vessels, divide skeletal muscle into compartments

each cell in skeletal muscle:

is a single muscle fiber, sheathed in endomysium

endomysium

loosely interconnects adjacent muscle fibers

tendons are:

bundles of connective tissue that join muscle to bone,and transmitt force of muscle contraction

what are tendons formed from

all 3 connective tissue layers epimysium, perimysium, and endomysium

where does the tendon attach muscle to on the bone

to the periosteum at a specific point on bone

what is aponeurosis

tendon bands- 2 layers (outer,inner) broad, flat sheets of connective tissue, involves more than one bone, isololated bone from surrounding tissues, participate in bone growth/repair

how are muscles formed

1. embryonic cells(myoblasts) from mutinucleate cells

2. over time fuse together. some remain as satelite cells

3. fusion produces very long muscle fibers.

what are satelite cells

stem cells that fxn in repair of damaged muscle tissue, remians in endomysium

what is a multinucleate cell

mature muscle fiber, regulating a large cytoplasm

What are the 3 types of muscular tissue?

Skeletal muscle; cardiac muscle; smooth/visceral muscle

What is the primary function of skeletal muscle?

Move bones

What is the primary function of cardiac muscle?

Pump blood

What is an example of smooth muscle function?

Peristalsis and other functions of organs

Which muscle type is voluntary?

Skeletal muscle

Which two muscle types are involuntary?

Cardiac and smooth muscle

Which muscle type is multinucleated and striated?

Skeletal muscle

Which muscle type has one nucleus, striations, and intercalated discs?

Cardiac muscle

Which muscle type has one nucleus and no striations?

Smooth muscle

Approximately how many skeletal muscles are in the human body?

About 700

What four major components make up skeletal muscles?

Skeletal muscle tissue; connective tissue; blood vessels; nerves

Put these in order from largest to smallest: muscle, fascicle, muscle fiber

Muscle → fascicle → muscle fiber

What is a fascicle?

A bundle of muscle fibers

What is a muscle fiber?

A skeletal muscle cell

What are the three connective tissue layers of skeletal muscle?

Epimysium; perimysium; endomysium

What surrounds the entire muscle?

Epimysium

What does the epimysium separate the muscle from?

Surrounding tissues

What surrounds a fascicle?

Perimysium

What does the perimysium contain?

Blood vessels and nerves

What surrounds an individual muscle fiber?

Endomysium

What does the endomysium do?

Ties adjacent muscle fibers together

What are tendons made from?

Bands of collagen fibers extending from the epimysium, perimysium, and endomysium

What do tendons attach?

Skeletal muscles to bone

How do tendons attach firmly to bone?

Their fibers interweave into the periosteum of the bone

What is another name for a skeletal muscle cell?

Muscle fiber

What does multinucleate mean?

Having multiple nuclei

What is the plasma membrane of a muscle fiber called?

Sarcolemma

What is the cytoplasm of a muscle fiber called?

Sarcoplasm

What major structures are found inside a muscle fiber?

Myofibrils; sarcoplasmic reticulum; T-tubules; mitochondria

What are myofibrils?

Structures inside muscle fibers containing bundles of protein filaments responsible for contraction

What is the sarcoplasmic reticulum?

A specialized structure that stores and releases calcium ions

What are transverse/T-tubules?

Tubules that carry the muscle action potential inward through the muscle fiber

What are terminal cisternae?

Expanded chambers of the sarcoplasmic reticulum located on both sides of T-tubules

What is a triad?

1 T-tubule + 2 terminal cisternae

What is stored in high concentration inside terminal cisternae?

Ca2+

What are myofilaments?

Protein filaments within myofibrils

What are the two major types of myofilaments?

Thick and thin

What protein primarily makes up thick myofilaments?

Myosin

What protein primarily makes up thin myofilaments?

Actin

What is titin?

A structural protein associated with thick filaments that connects to the Z line and recoils after stretching

What produces the striated appearance of skeletal muscle?

The overlapping arrangement of thick and thin filaments

What is the A band?

The wide, dark stripe corresponding to the location of thick filaments

Does the A band change length during contraction?

No

What is the M line?

A thin, dark strip in the center of the A band that stabilizes thick filaments

What is the H zone?

The lighter region around the M line containing thick but no thin filaments

What is the zone of overlap?

The darker region where thick and thin filaments overlap

What is the I band?

The wide, pale stripe containing thin filaments

What happens to the I band during contraction?

It shortens

What is the Z line/Z disc?

A thin, dark structure containing actinin proteins that attaches the ends of thin and titin filaments

What is a sarcomere?

The basic contractile unit of a myofibril

From where to where does a sarcomere extend?

Z disc to Z disc

Approximately how many sarcomeres are in a myofibril?

About 10,000 arranged end-to-end

What are the major proteins associated with thin filaments?

Actin; nebulin; tropomyosin; troponin

What is G-actin?

Individual actin molecules

What is F-actin?

A strand formed from G-actin molecules

What is an active site on actin?

A binding site where a myosin head can attach

What does tropomyosin do at rest?

Blocks the active sites on actin

What does troponin do when Ca2+ binds to it?

It changes position and moves tropomyosin, exposing actin's active sites

What are the major proteins associated with thick filaments?

Myosin; titin; M-line proteins

What are the three major regions of a myosin molecule?

Tail; hinge; head

What does the myosin head do?

Attaches to actin and pulls the thin filament toward the M line

What does the hinge of myosin allow?

It allows the myosin head to pivot

What does titin do?

Forms part of the thick filament core, connects to the Z line, and recoils after stretching

What do M-line proteins do?

Stabilize the position of thick filaments

Which muscle proteins are contractile?

Myosin and actin

Which muscle proteins are regulatory?

Troponin and tropomyosin

Name structural muscle proteins from the slides.

Titin; nebulin; alpha-actin; myomesin; dystrophin

What is the sliding filament theory?

Thin filaments slide past thick filaments toward the M line, causing the sarcomere to shorten

What happens to the H zone during contraction?

It shortens

What happens to the I band during contraction?

It shortens

What happens to the zone of overlap during contraction?

It increases/lengthens

What happens to the Z discs during contraction?

They move toward each other