Ch.85 Biology and Management of Muscle Disorders and Diseases

Question 1

3 types of muscles

Answer 1

Smooth
Skeletal
Cardiac

Question 2

Which muscle type is most abundant

Answer 2

Skeletal

Question 3

% body weight is skeletal muscle

Answer 3

42%
55% in a tb racehorse

Question 4

Composition of skeletal muscle

Answer 4

90% myofibers
10% Nerves, blood vessels, fat, connective tissue

Question 5

What are the endomysium, perimysium, epimysium

Answer 5

Connective tissue surrounding
1. Muscle fibers - Endo
2. Fascicles - Peri
3. Muscles bellies - Epi

Question 6

What is the sarcolemma

Answer 6

Outer membrane of a myofiber

Question 7

What is a sarcomere

Answer 7

Basic contractile unit of the muscle fibre

Question 8

Myofibrils at the I-bands are composed of what proteins

Answer 8

Actin
Tropomyosin
Troponin

Question 9

Myofibrils at the A-bands are composed of what proteins

Answer 9

Myosin

Question 10

What is the sarcotubular system

Answer 10

Membrane in the form of tubules containing transverse tubular system and sarcoplasmic reticulum, surrounding the myofibrils

Question 11

Each muscle fibre in innervated by what

Answer 11

Terminal branch of an alpha motor nerve fibre

Question 12

All skeletal muscle fibres that are innervated by a single alpha motor neurone are called

Answer 12

A motor unit

• all fibres within a unit are excited simultaneously and contract in unison

Question 13

Action potential causes the release of what from the sarcoplasmic reticulum

Answer 13

Calcium ions

Question 14

What do calcium ions bind with and what is the outcome

Answer 14

• Troponin-C

-Conformational change of the troponin-tropomyosin complex

-Exposing myosin binding sites

Question 15

How is the length of the sarcomere shortened

Answer 15

Globular heads of myosin exposed
Interact with actin forming a crossbridge
Results in sliding of the actin in relation to the myosin molecules

Question 16

What is required for muscle contraction/sacromere shortening

Answer 16

• ATP
• Creatinine Phosphate used to replenish ATP from ADP
• Catalyzed by Creatine Phospokinase

Question 17

What % of energy is used for muscle contraction and what happens to the rest

Answer 17

40% muscle contraction
Rest lost as heat

Question 18

Muscle fibres are differentiated by what

Answer 18

Expression of the specific myosin heavy chain isoforms MyHC

Question 19

What are the adult skeletal muscle types

Answer 19

I - Slow fibers (Posture)
IIA - Fast
IIX - 3 times higher velocity of contraction than IIA

Present as single isoforms or hybrids

Question 20

How long does it take for new myofibres to form

Answer 20

They do not form after birth

Question 21

How do muscles grow

Answer 21

Additional myofibrils
and enlargement of myofibers