Muscle Physiology

Question 1

What are the two major classes of muscle?

Answer 1

Striated and smooth.

Question 2

What are the three major types of muscle?

Answer 2

Skeletal, cardiac and smooth.

Question 3

What muscle types are voluntary?

Answer 3

Skeletal.

Question 4

What muscle types are involuntary?

Answer 4

Cardiac & smooth.

Question 5

What muscle types are straited?

Answer 5

Skeletal and cardiac.

Question 6

What muscle typed are unstraited?

Answer 6

Smooth.

Question 7

What is the role of skeletal muscle?

Answer 7

• Locomotion
• Heat production
• Energy store/management
• Sound production
• Electricity production
• Primary food for predators.

Question 8

What is the role of cardiac muscle?

Answer 8

Regulates blood circulation.

Question 9

What is the role of smooth muscle?

Answer 9

Movement of fluids, gases and solids through internal organs e.g. digestion.

Question 10

Define myomere.

Answer 10

Separated sheets of connective tissue called myosepta.

Question 11

What is the approximate diameter of a skeletal muscle fibre/ muscle cell?

Answer 11

5um - 10um.

Question 12

Define sarcolemma.

Answer 12

Striated muscle cell membrane.

Question 13

Define myofibrilis.

Answer 13

Main contracting unit of skeletal muscle fibre.

Question 14

Define T tubule.

Answer 14

An infolding of the sarcolemma.

Question 15

Define terminal cisternae.

Answer 15

Enlarged part of sarcoplasmic reticulum that sits either side of T tubule.

Question 16

Apart from muscle cells, what other cells do you get in muscles?

Answer 16

• Endothelial cells
• Immune cells
• Fibroblasts
• Stem/progenitor cells.

Question 17

What three stages does skeletal muscle contraction depend on?

Answer 17

• Events at the neuromuscular junction
• Excitation contraction (EC) - coupling
• The cross-bridge cycle.

Question 18

Define triad.

Answer 18

One portion of a T tubule plus the two adjacent terminal cisternae.

Question 19

Define tetanus contraction.

Answer 19

The maximal contraction a muscle fibre can achieve i.e. maximal number of actin binding sites available for myosin heads.

Question 20

Define motor units.

Answer 20

A group of muscle fibres that all get their signals from the same, single motor neuron.

Question 21

Define fatigue.

Answer 21

Inability to maintain muscle contraction at a given level of exertion.

Question 22

Define asynchronous recruitment.

Answer 22

During sustained sub-maximal contraction - motor units take turns to be recruited. This optimises the overall time that an activity can occur.

Question 23

What factors influence the level of muscle contraction?

Answer 23

• Size of muscle group
• Starting muscle length sets maximum tension possible
• Specialisation of muscle fibre characteristics.

Question 24

What level of activity can type 1/slow oxidative fibres produce?

Answer 24

Endurance low-power activity.

Question 25

What level of activity can type 2a/fast oxidative fibres produce?

Answer 25

Sustained power activity (sub-maximal).

Question 26

What level of activity can type 2b/fast glycolytic fibres produce?

Answer 26

Short bursts of maximal or near maximal activity.

Question 27

What do muscles use energy for?

Answer 27

ATP used in cross bridge cycle, to re-establish ion gradients across muscle membrane and transport Ca2+ back to sarcoplasmic reticulum.

Question 28

How can ATP be generated for muscle contraction?

Answer 28

- Oxidative phosphorylation - Glycolysis in muscle - Glycogenolysis in muscle and liver.

Question 29

What method of ATP generation do muscles use when resting or recovering?

Answer 29

Oxidative phosphorylation.

Question 30

What method of ATP generation do muscles use when undergoing intense exercise?

Answer 30

Glycolysis.

Question 31

Why is muscle recovery crucial?

Answer 31

- Replenish glycogen, ATP and creatine phosphate - Re-establish normal ion gradients, Ca2+ stores and pH - Deal with lactate accumulation - Repair damaged muscle fibres and stimulate growth.

Question 32

What is the Bohr effect?

Answer 32

Haemoglobin's oxygen binding affinity inversely related both to acidity and to the concentration of carbon dioxide.

Question 33

What structural and biochemical features of skeletal muscle make it efficient at oxygen delivery?

Answer 33

- Muscle capillaries are organised in a weaving pattern optimising transit time for blood - Activity induces muscle blood vessel vasodilation increasing blood flow during exercise - Muscle activity increases oxygen release by haemoglobin, mainly by reducing the partial pressure of oxygen and reducing pH (Bohr effect).

Question 34

What is myoglobin?

Answer 34

- Its what makes muscles red - found in striated muscle - aids delivery and storage of oxygen.

Question 35

What are thin filaments made of?

Answer 35

Actin.

Question 36

What are thick filaments made of?

Answer 36

Myosin.

Question 37

What do troponin and tropomyosin do?

Answer 37

Prevent myosin from binding to actin. When Ca2+ binds to troponin it stops tropomyosin from preventing myosin binding to actin.

Question 38

What do skeletal and cardiac muscles have in common?

Answer 38

- Have same sarcomere organisation (overlapping thin/thick filaments) - Have extensive SR & T tubules - Identical contraction mechanism.

Question 39

How do skeletal and cardiac muscles differ?

Answer 39

- Cardiac muscles contract regularly, slowly and involuntary - Possess pacemaker cells - Possess gap junctions - Possess desmosomes.

Question 40

What are the similarities between skeletal and smooth muscle?

Answer 40

Have thick and thin actin and mysoin filaments.

Question 41

What are the similarities between smooth and cardiac muscles?

Answer 41

- Smooth and mononucleated | - May have gap junctions and desmosomes.

Question 42

What are the differences between striated and smooth muscle?

Answer 42

- Spindle shaped cells in sheets - Lack T tubules and SR - Lack troponin.

Question 43

Define neurogenic and myogenic.

Answer 43

Neurogenic - contraction originates from external innervation Myogenic - Contraction originates from within muscle.

Question 44

Define tonic and phasic.

Answer 44

Tonic - continuous state of partial contraction | Phasic - Pronounced rhythmic increase in contraction.

Question 45

Define excitation contraction coupling.

Answer 45

The process linking an action potential to muscle contraction.