Locomotor - Muscles

Question 1

What is the order of skeletal muscles? (smallest to largest)

Answer 1

Myofilaments > Sarcomeres > Myofibril > Muscle fibres > Fascicle > Muscle belly

Question 2

What is the epimysium?

Answer 2

Surrounds whole muscle belly

Question 3

What is the perimysium?

Answer 3

Surrounds whole muscle fascicle

Question 4

What is the endomysium?

Answer 4

Surrounds muscle fibres

Question 5

What is the sarcolemma?

Answer 5

Surrounds myofibrils

Question 6

What is the appearance of skeletal muscle?

Answer 6

Multiple peripheral nuclei
Appears striated with regular parallel bundles
Under voluntary control
Highest sarcoplasmic reticulum development

Question 7

What is the appearance of cardiac muscle?

Answer 7

Striated
Single nucleus
Irregular arrangement of intercalated discs

Question 8

What are the features of cardiac muscle?

Answer 8

Involuntary control
High mitochondrial density (high metabolic demand)
Low electric resistance

Question 9

What are the types of cell junctions in cardiac muscles?

Answer 9

Joined at Z line

Desmosome - joins together and stops separation
Gap junction - allows AP to flow
Fascia adherens - provides an anchorage for actin
Transitional junction - where myocytes join

Question 10

What are the features/appearance of smooth muscle?

Answer 10

No striations
Single nucleus
Longer contractions
Involuntary

Question 11

What is the equation for muscle strength?

Answer 11

Work = force x distance

Power = work/ time

Question 12

What are the features of parallel muscles?

Answer 12

Fibres run parallel with line of the pull.

Longer fibres = more sarcomeres = greater shortening ability aka distance increases

e.g. Sartorius and Semitendinous and Latissimus dorsi

Question 13

What are the features of pennate muscles?

Answer 13

Shorter muscle fibres at angle to internal tendon.

Allows more sarcomeres in smaller space = increase cross sectional area = increase force created

More economical and linked to stabilisation

e.g. Serratus ventralis

Question 14

Which is better, pennate or parallel?

Answer 14

If pennate and parallel are same length, pennate produces more force, but parallel produces more power

Question 15

Whats the all or nothing system?

Answer 15

One nerve per muscle fibre with all or nothing, once AP threshold is met all fibres innervated will contract

Question 16

What makes up a sarcomere?

Answer 16

Between Z discs are actin myofilaments surrounding a myosin filament, joined by cross bridges. The middle is the M line.

Question 17

What is the sliding filament theory?

Answer 17

1. AP travels down T-tubule opening Ca2+. Ca2+ interacts with DHP and ryanodine receptors inducing the SR to release Ca2+
2. Ca2+ binds to Troponin C on the actin filament, exposing the myosin binding site
3. Myosin head forms a cross bridge and performs a power stroke pulling actin closer
4. Myosin head previously had ADP + Pi attached, which is hydrolysed and becomes ATP
5. ATP binds back to the head and the power stroke will continue until ATP is depleted and/or Ca2+ is decreaased.
6. Ca2+ is removed by Ca-ATPase pump

Question 18

What are type I muscle fibres?

Answer 18

Slow oxidative

Uses oxidative phosphorylation in mitochondria to produce ATP

Slow and fatigue resistant

Lots of capillaries and smaller in diameter, darker looking

Question 19

What are type IIa?

Answer 19

Glycotic oxidative fibres

Works via glycolytic phosphorylation of ADP via creatine but limited supply

Question 20

What are type IIb?

Answer 20

Glycolytic fibres

Uses glycolytic phosphorylation of ADP in cytosol and requires glycogen store. Produces lactic acid as bproduct

Short lived and large amount of force but fatigue quickly

Large in diameter and less capillaries, appear lighter