A&P I: Muscular system Guided notes 3

will this be worth it..?

What are Sarcomeres..?

contractile units of skeletal muscle

Myofibrils are made up of many what..?

sarcomeres connected together

Key characteristics of Sarcomeres

• thick and thin filaments are arranged in a grid like pattern

• each sarcomere contains all the parts needed to perform contraction

• many thousands of Sarcomeres must contract for the whole muscle to contract

One muscle fiber has approx. how many Sarcomeres..?

100,000 sarcomeres

What is the name of the arrangement of Sarcomeres

straitions

What is straitions..?

visible patterns

What is the A band..?

a darker area that contains thick filaments and includes the Zone of Overlap

What is the I band..?

the lighter area that contains only thin filaments

What is the Zones of Overlap..?

where thick and thin filaments overlap

What type of area is the Zone of Overlap..?

the densest and darkest area of sarcomere

Why are they (zone of overlap) important..?

b/c the filaments must interact for concentration to occur and they cannot interact for concentration to occur (they cannot interact if they don’t overlap)

What is the M Line..?

consists of structural proteins located at the center of the sarcomere

What is the M Lines Function..?

• stabilizes and holds the sarcomeres together

• does not actively participate in contractions

What are Z lines..?

the structural proteins located at the two ends of the sarcomere

What happens when the sarcomere contracts..?

The Z lines get pulled closer together

What is the H band..?

is the are around the M line

Characteristics of the H band

• contains thick filaments but no thin filaments

• when a sarcomere contracts, thin filaments get pulled into the H band

• The size of the H band may determine how much the sarcomere can contract

What is Titin..?

made up of proteins that stabilize thick filaments

What is those Titin look like..?

they appear as wavy green lines in digrams

How do the Sarcomeres function..?

1. T-tubules encircle the sarcomere near the Zones of overlap

2. Terminal cisternae of the Sarcoplasmic Reticulum release Ca +2 hen an action potential arrives

3. The Ca+2 released causes the thick and thin filaments to interact with each other

4. These interactions of the filaments causes the contraction

Where are Calcium Ions stored and released from..?

the terminal cisternae