Ch 12: Muscles

Question 1

Cardiac & skeletal muscles contain?

Answer 1

• Striations
• Muscle fiber
• Nucleus

Question 2

“How you interact with external environment” is due to?

Answer 2

Skeletal muscle

Question 3

Smooth muscles is found where?

Answer 3

Where you have an interior & want muscle around it to contract it
- By uterus, bladder

Question 4

What does smooth muscle lack?

Answer 4

Striations

Question 5

Types of muscles

Answer 5

1. Skeletal
2. Cardiac
3. Smooth

Question 6

Skeletal muscle - Antagonistic muscles: Flexion

Answer 6

Triceps - muscle relaxes
Biceps - muscle contracts (flexor)

Question 7

Skeletal muscle - Antagonistic muscles: Extension

Answer 7

Triceps - muscle contracts (extensor)
Biceps - muscle relaxes

Question 8

Muscle contraction is energetically ___________?

Answer 8

Expensive

Question 9

Muscle fiber

Answer 9

Muscle cell
- can be long, but NOT as long as neurons

Question 10

Modified ER

Answer 10

Sarcoplasmic reticulum
- stores Ca2+

Question 11

Cytoplasm

Answer 11

Sarcoplasm

Question 12

Cell membrane

Answer 12

Sarcolemma

Question 13

Striated (skeletal) muscle occupies how much of the adult human body by mass?

Answer 13

40-50%

Question 14

At rest, skeletal muscle accounts for ____ of oxygen consumed?

Answer 14

25%, can triple during exercise

Question 15

Sarco

Answer 15

Muscle

Question 16

Ultrastructure of Muscle

Answer 16

A. Contractile proteins
B. Regulatory proteins

Question 17

Contractile proteins

Answer 17

1. Myosin
2. Actin

Question 18

Myosin

Answer 18

Part of thick filament
- approx. 250 individual myosin molecules join to form thick filament
- each single myosin molecule has 4 subunits: 2 heavy chains forming a tail, 2 lighter chains forming the head

Question 19

Actin

Answer 19

Part of the thin filament
- double helix of G-actin (globular) molecules
- each G-actin has binding site for myosin (convenient)
- strand of G-actin called F-actin (fibrous)

Question 20

Regulatory proteins

Answer 20

Both found on thin filament
1. Tropomyosin
2. Troponin

Question 21

Tropomyosin

Answer 21

Regulatory protein that covers the binding sites on F-actin (covers 7 actin molecules)

Question 22

Troponin

Answer 22

Regulatory protein (composed of 3 subunits) bound to tropomyosin & has a binding site for Ca2+

Question 23

Actin-Myosin Cross Bridge Cycle

Answer 23

1. Increased intracellular Ca2+ levels, Ca2+ binds to troponin
2. Troponin changes shape & pulls tropomyosin off binding sites
3. Actin & myosin attach
4. Pi is released
5. Power strokes occurs, shortens sarcomere
6. ADP is released
7. Fresh ATP, if available, binds to myosin head
8. Myosin detaches from actin
9. ATP hydrolyzed, energy re-cocks myosin head
10. If Ca2+ still present, myosin attaches to actin, cycle repeats
11. If Ca2+ is removed, tropomyosin covers binding sites preventing actin-myosin cross bridge

Question 24

Skeletal muscle group composed of?

Answer 24

Fibers aka cells

Question 25

Why is skeletal muscle multi-nucleated?

Answer 25

Due to fusion of myoblasts during development - cannot undergo mitosis

Question 26

Epimysium

Answer 26

Connective tissue

Question 27

Perimysium

Answer 27

Fascicle - bundle of muscle fibers

Question 28

Endomysium

Answer 28

muscle fiber (cell)

Question 29

Myofibril

Answer 29

Contains thin and thick filament

Question 30

T-tubule

Answer 30

Brings action potentials into interior of muscle fiber

Question 31

Terminal cisterna

Answer 31

Big place for storage - lateral sacs - regions of SR that are T-tubules

Question 32

Sarcomere

Answer 32

Functional unit of skeletal muscle - Z line to Z line - the contractile unit of striated muscles

Question 33

Each myosin head contains a binding site for?

Answer 33

Actin & ATPase site - can only bind to ONE, NOT BOTH

Question 34

A flexible hinge allows the head to undergo _________

Answer 34

The powerstroke

Question 35

Actin attached to?

Answer 35

Z-line

Question 36

Actin helix

Answer 36

Backbone of thin filament

Question 37

Sliding filament theory

Answer 37

Force is generated as fixed-length filaments slide pass one another