Muscles

Question 1

Three types of muscles

Answer 1

Smooth
Skeletal
Cardiac

Question 2

Striated Voluntary Muscle type

Answer 2

Skeletal Muscle

Question 3

Striated involuntary muscle type

Answer 3

Cardiac Muscle

Question 4

Unstriated involuntary muscle type

Answer 4

Smooth muscle

Question 5

Connective tissue anchoring muscle at each end

Answer 5

Tendon

Question 6

Each muscle consists of?

Answer 6

Muscle fibers

Question 7

Each muscle fiber is composed of?

Answer 7

Myofibrils

Question 8

Myofibrils consist of?

Answer 8

Myofilaments:
Thin (Actin) and Thick (Myosin)

Question 9

What is the functional unit of a striated muscle?

Answer 9

Sarcomere

Question 10

Boundaries of a sarcomere.

Answer 10

Z-Line

Question 11

Term for the dark bands

Answer 11

A-bands

Question 12

Term for the light bands that have the z-line in the middle. This is also considered the distance between thick filaments

Answer 12

I-band

Question 13

Line visible in the middle of the a-band

Answer 13

M-line

Question 14

Area that contains the M-line

Answer 14

H-Zone

Question 15

Densest portion of the sarcomere

Answer 15

A-Band

Question 16

Lighter portion of the a band

Answer 16

H-zone

Question 17

Portion between a-bands

Answer 17

I-Band

Question 18

Middle of H-Zone

Answer 18

M-line

Question 19

Projection outward of thick filament (myosin) that makes contact with the actin during contraction

Answer 19

Cross Bridges

Question 20

In a myofibril, each thin filament is surrounded by how many thick filaments?

Answer 20

3

Question 21

Two sites on the globular heads of myosin molecules that form the cross bridges

Answer 21

Actin-Binding site and Myosin ATPase site

Question 22

Main structural components of skeletal thin filaments

Answer 22

Actin molecules, Troponin (Globular) and Tropomyosin (thread-like)

Question 23

What is the function and mechanism of tropomyosin and troponin

Answer 23

Actin molecules have binding sites for myosin crossbridge. Troponin attached to tropomyosin wrap around the actin molecules to cover these binding sites.

Question 24

How does cross-bridge interaction between actin and myosin bring about muscle contraction? What is this called?

Answer 24

During contraction of striated muscle, thin filaments on each side of a sarcomere slide inward toward the A band’s center.
They pull closer together the Z discs to which they are attached, so the sarcomere shortens and the entire fiber becomes shorter.

Sliding Filament Theory

Question 25

What is the role of Calcium 2+ Ion in cross bridge activity

Answer 25

Calcium binds to troponin causing troponin to slide the tropomyosin away allowing for binding of actin and myosin at the now unblocked cross-bridge binding sites.

Question 26

This is triggered by the binding of actin and myosin

Answer 26

Power stroke

Question 27

T/F A-band gets shorter during muscle contraction

Answer 27

False, I-band and H-zone become shorter

Question 28

During muscle contraction, what happens to A band? Shorten, lengthen?

Answer 28

It stays the same

Question 29

Bending of the crossbridge upon contact with actin

Answer 29

Power stroke

Question 30

This is needed to achieve desired extent of muscle shortening

Answer 30

Repeated power stroke

Question 31

4 steps of the crossbridge cycle

Answer 31

Binding Power Stroke Detachment Repeat

Question 32

T/F All cross-bridge strokes are directed toward the center of the thin filament

Answer 32

F. All towards thick filament

Question 33

T/F Cross bridges are asynchronously cycling leading to some holding on while others are letting go causing the "ladder-like" climb

Answer 33

True

Question 34

extensions of the surface membrane that dip deep into the muscle fiber at the junctions between the A and I bands

Answer 34

Transverse (T) Tubules

Question 35

runs longitudinally and surrounds each myofibril, with separate segments encircling each A band and I band

Answer 35

Sarcoplasmic Reticulum

Question 36

saclike regions at the end of each sarcoplasmic reticulum segment

Answer 36

Lateral Sacs (Terminal Cisternae)

Question 37

T tubule membrane allows spread of _______ from surface membrane transmitting surface electric activity

Answer 37

Action Potential

Question 38

Action potential triggers what?

Answer 38

Release of Ca2+ from the lateral sacs

Question 39

What are the effects of Ca2+ movement to the musccle?

Answer 39

Release: Contraction Re-uptake: Relaxation

Question 40

Type of voltage-gated calcium channel, meaning they open in response to changes in membrane potential. These channels allow the influx of calcium ions (Ca2+) into cells Long-lasting currents

Answer 40

L-type calcium channels or Ryanodine receptors

Question 41

Steps in excitation-contraction coupling and muscle relaxation (8)

Answer 41

1. Action potential triggers acetylcholine release and muscle fiber action potential. 2. T tubule action potential releases Ca2+ from sarcoplasmic reticulum. 3. Ca2+ binds to troponin on thin filaments. 4. Ca2+ on troponin alters tropomyosin shape, exposing actin binding sites. 5. Myosin cross bridges attach to exposed actin binding sites. 6. Cross bridge binding initiates power stroke, pulling thin filament. 7. After power stroke, cross bridge detaches from actin. 8. Action potential cessation leads to Ca2+ uptake, tropomyosin blocks actin binding sites.

Question 42

Tension in cardiac muscle depends on?

Answer 42

The amount of calcium ions in the myoplasm

Question 43

What is the difference in appearance of smooth muscle and skeletal muscle

Answer 43

Smooth muscle cells are nucleated

Question 44

T/F Contraction and relaxation occurs slowly in smooth muscle compared to skeletal muscle leading to more contractions

Answer 44

True

Question 45

T/F Calcium Binds to Troponin in smooth muscle cells to cause the myosin cross bridge

Answer 45

False, Calcium binds to calmodulin due to absence of troponin

Question 46

What are the steps in the calcium activation in smooth muscle cells

Answer 46

Ca2+ binds with calmodulin -> activates Myosin Light Chain Kinase -> myosin light chain phosphorylation -> Phosphorylated myosin cross bridge can bind with actin

Question 47

Read the summary on the final 3 pages of the Muscle and movement pdf

Answer 47

Gl