Muscle Physiology

Question 1

Briefly describe skeletal muscle tissue

Answer 1

Multinucleated long cylindrical cells

Many parallel fibres

Question 2

Briefly describe cardiac muscle tissue

Answer 2

Mononuclear

Branching network

Question 3

Briefly describe smooth muscle tissue

Answer 3

Viscera and blood vessels
Mononuclear
Spindle shaped

Question 4

What system innervates the different types of muscle?

Answer 4

Skeletal - Somatic
Cardiac - Autonomic
Smooth - Autonomic

Question 5

What is the differences in speed of contraction of different types of muscle?

Answer 5

Skeletal - Fast contraction
Cardiac - Slow rhythmical contraction
Smooth - Very slow rhythmical contraction

Question 6

From what cell does a muscle fibre form?

Answer 6

Fusion of myoblasts (mesodermal cells)

Question 7

What is the sacrolemma?

Answer 7

Membrane of a muscle fibre which surrounds sacroplasm

Question 8

What are T-tubules?

Answer 8

Extensions of the sacrolemma into the muscle fibre bound tightly to sacroplasmic reticulum

Question 9

What is the sacroplasmic reticulum?

Answer 9

Tubular network around myofibrils

Question 10

What is a Triad?

Answer 10

Pair of terminal cisternae (Ca2+ storage) and a T tubule

Question 11

What is the differenc ein uniformity between an I-band and an A-band?

Answer 11

I-band is isotropic, A-band is anisotropic

Question 12

What are the thick and thin filaments of a sacromere primarily made of?

Answer 12

Myosin (thick) and actin (thin)

Question 13

What is titin?

Answer 13

Elastic material

Binds myosin to Z-line

Question 14

Describe the structure of a thin filament

Answer 14

Two twisted rows of globular F-Actin
Surrounded by strand of tropomyosin
With troponin to bind together

Question 15

Describe the structure of a thick filament

Answer 15

300 myosin subunits
Tails towards M-line
Heads are two globular proteins

Question 16

On muscle contraction, which zones change size and which do not?

Answer 16

A zone stays same
I zone shrinks
Z lines move closer together

Question 17

What are the steps involved in muscle contraction following an action potential from the neuromuscular junction?

Answer 17

See Notes

Question 18

What does skeletal muscle relaxation depend on?

Answer 18

Duration of stimulus
Quantity of free Ca2+
Availability of ATP
AchE breaks down ACh and sarcoplasmic reticulum recaptures Ca2+

Question 19

Explain rigor mortis

Answer 19

ATP regeneration stops, so Ca2+ pump does not work and myosin heads remain cross bridged

Question 20

What dictates fibre tension?

Answer 20

Sum of tension from fibres
Total number fibres
Length of fibres
Cross-sectional area of fibres
Tension exerted on muscle elastic compartments

Question 21

When is fibre tension optimal?

Answer 21

Muscle at resting length (tense, but not shortened)

Question 22

What are the three phases of a muscular twitch?

Answer 22

Latent period
Contraction phase
Relaxation phase

Question 23

What is treppe?

Answer 23

Increase in twitch tension with successive twitches

Question 24

What is wave summation?

Answer 24

Twitches occur before relaxation phase completes

Question 25

What is incomplete tetanus?

Answer 25

Increased twitch frequency with brief relaxation phases

Question 26

What is complete tetanus?

Answer 26

Twitch frequency high enough to eliminate relaxation phase

Question 27

What is a motor unit?

Answer 27

Motor neuron which controls all fibres in a muscle

Question 28

What determines muscle precision, speed and force?

Answer 28

Innervation ratio | Size of units (smaller is slower with lower force)

Question 29

What are Type 1 muscle fibres?

Answer 29

Slow, small, oxidative capacity, low fatigue | RED

Question 30

What are Type 2a muscle fibres?

Answer 30

Intermediate size and speed, moderate fatigue, oxidative and anaerobic capacity

Question 31

What are Type 2b muscle fibres?

Answer 31

Fast, large in size, high force, poor oxidative capabilities, high anaerobic capacity, fatigue quickly, few mitochondria, scarce capillary size WHITE

Question 32

What are the three types of contractions?

Answer 32

Isometric (muscle active but no change in length) Isotonic (muscle shortens) Eccentric (muscle lengthens)