Physio Section 5

Skeletal muscle

responsible for supporting and moving the skeleton; under voluntary control

Cardiac muscle

Muscle of the heart; involuntary control

Smooth muscle

muscle surrounding hollow organs and other tissues; involuntary control

Skeletal and smooth muscle

What two types of muscles are striated?

Skeletal muscle cell

What is the other name for a skeletal muscle fiber?

Myoblasts

The fusion of what single-nuclei cell creates a muscle fiber?

It can be as little as a few, or as big as hundreds

How many nuclei does a skeletal muscle fiber contain?

Transverse tubules (T tubules)

deep inward folds of the muscle cell membrane (sarcolemma) that carry electrical signals deep inside the cell to trigger muscle contraction

Myofibril

Many fill each skeletal muscle fiber and give the muscle fibers their striated appearance

Sarcomere

The region between 2 Z lines

6 thin filaments

How many thin filaments surround each thick filament?

3 thick filaments

How many thick filaments surround each thin filament?

Parallel

Thick filaments are composed of _________ bundles of myosin.

Actin; actin monomers

Thin filaments are composed of a double strand of ______ that containes many _______________.

M line

In the middle of the sarcomere, myosin protrudes off of it

Z line

At the ends of each sarcomere, actin protrudes off of it

H zone

Contains the area of only the m line and myosin

A band

Contains the area where myosin and actin overlap

I band

Contains the area of only actin and the Z line

‘Contraction"‘

Refers to activation of the cross-bridges to create tension between the thick and thin filaments.

Isometrically

Every contraction begins __________ until the load requirement can be met.

By the myosin acting on the actin

How is force generated?

The H zone and the I band

What two zones of the sliding filament mechanism are reduced in length, while everything else stays the same?

Tropomyosin

A rod-shaped protein that wrap around each actin filament, overlaping the myosin binding sites in a relaxed state

Troponin

A small protein that controls the placement of tropomyosin

Ca²⁺

What binds to troponin irreversibly, and once binded causes tropomyosin to pull away from the myosin binding sites to allow myosin and actin to interact

The thin filament

Ca²⁺ is regulated at what level?

2 heavy chains (tails)

2 necks

2 heads

What are the 6 proteins of myosin?

ATP

Releases the myosin heads from actin

Excitation-Contraction Coupling (EC Coupling)

The series of events that occur between an action potential in the muscle fiber membrane and muscle contraction

It causes an increase in muscle cytosolic Ca²⁺

What occurs after an action potential is triggered?

The Ca²⁺ binding system reaction has to occur before the sliding filament theory occurs

Why is there a delay from a muscle fiber action potential to the muscle contraction?

DHP receptors (dihydropyridine)

voltage sensors in T-tubules

Ryanodine receptors

massive intracellular calcium release channels located on the membrane of the sarcoplasmic reticulum in muscle cells that regulate muscle contraction and cell signaling by releasing stored calcium ions into the cytoplasm

The action potential first has to be stopped, then the Ca²⁺ will get pumped back into the SR

What has to happen to relax muscle contraction?

Lateral sacs or terminal cisternae

Contain Ca²⁺ ions that will be released to trigger muscle contraction

Muscle contractions

Resulted from the tension created by thick and thin filament interaction

Ca²⁺, troponin, and tropomyosin

What regulates muscle contraction?