Lecture 3 - Muscles

Question 1

Muscles can only generate force by shortening. True or False?

Answer 1

True

Question 2

What is the difference between CIlia and Flagella?

Answer 2

Cilia are 0.2-0.5 um and are found in all animals except nematodes (and limited in some arthropods). Cilia beat asymmetrically. Fluid propelled parallel to surface.
Flagella are longer and beat symmetrically. Fluid propelled perpendicular to surface.

Question 3

Functions of muscles

Answer 3

Posture, movement, peristalsis, generation of heat and electricity, sound, internal organ function

Question 4

What are the four functional characteristics of muscle?

Answer 4

Contractility, excitability, extensibility, elasticity

Question 5

Contractility

Answer 5

Muscles can forcefully shorten

Question 6

Excitability

Answer 6

Muscles respond to a stimulus

Question 7

Extensibility

Answer 7

Muscles can be stretched

Question 8

Elasticity

Answer 8

Muscles recoil or bounce

Question 9

What are the types of invertebrate muscle?

Answer 9

Smooth (bivalve adductor muscle - slow), striated (e.g. bivalve closure muscle - fast), fibrillar (e.g. insect flight, very fast)

Question 10

Direct flight of insects

Answer 10

Muscles directly attach to wings

Question 11

Indirect flight in insects

Answer 11

Muscles attach to the thorax, rather than to wings, and cause flight by movement of the thorax.

Question 12

Types of vertebrate muscle

Answer 12

Smooth (gut and blood vessels)

Striated (skeletal and cardiac)

Question 13

Skeletal muscle

Answer 13

Attached to skeleton
Responsible for movement and posture
Striated, many nuclei, transverse tubules
Voluntary control
Fast contraction, relaxes and tires quickly

Question 14

Cardiac muscle

Answer 14

Located in walls of the heart
Role in the pumping of the heart
Striated, uninuclear, transverse tubules, intercalated discs
Involuntary control
Contracts as a unit, self-exciting, rhythmic

Question 15

Smooth muscle

Answer 15

Located in walls of hollow viscera in gut
Role in movement and peristalsis
Not striated, uninuclear, no transverse tubules
Involuntary control
Contracts and relaxes slowly, self exciting, rhythmic contractions

Question 16

True or false. Muscle can be attached to other muscle

Answer 16

True. e.g. Flehmen response

Question 17

Power is affected by

Answer 17

Type of fiber
Muscle cross-sectional area
Type of leverage

Question 18

Power formula

Answer 18

Force x speed

Question 19

Components of a lever

Answer 19

Resistance, Fulcrum, Effort

Question 20

Mechanical Advantage

Answer 20

High MA = high force but low speed

Low MA = low force but high speed

Question 21

In a muscle/joint attachment, the muscle provides

Answer 21

The effort

Question 22

1st class lever

Answer 22

Fulcrum in the middle. E.g. neck atlantooccipital joint.

Question 23

2nd class lever

Answer 23

Resistance in the middle. Example; jaw joint.

Question 24

3rd class lever

Answer 24

Effort in the middle. Most joints in body.

Question 25

Antagonistic muscle pairs

Answer 25

Act against each other and balance each other out. When one is stimulated, the other is not.

Question 26

Spongy bone

Answer 26

Open interlacing framework of bony tissue, trebeculi, lots of blood vessels, red blood cells

Question 27

Compact bone

Answer 27

On the outside of shafts, stronger than spongy bone, dense, supports more weight. Levers are usually attached to the spongy bone.

Question 28

Tendons

Answer 28

Attach muscle to bone

Question 29

Contraction of skeletal muscle

Answer 29

See slides. Actin and myosin filaments in a sarcomere (unit of a myofibril) slide towards each other due to the movement of the myosin head mediated by ATP.

Question 30

Contraction vs relaxation

Answer 30

Contraction requires energy. Relaxation is passive

Question 31

Muscle contraction requires

Answer 31

ATP, calcium, a stimulus

Question 32

Muscle contraction produces

Answer 32

Lactic acid

Question 33

Energy for muscle use is provided by

Answer 33

Cellular respiration, or anaerobic respiration with sustained use

Question 34

Motor unit

Answer 34

A neuron and all the muscle fibres it activates (a few to 2000). Higher force is achieved with more motor units.

Question 35

Neural control of muscle

Answer 35

Neuron releases ACH Fibre depolarises and relases Ca2+ Fibre contracts

Question 36

Vertebrate vs invertebrate muscle force

Answer 36

Vertebrate is an all-or-nothing response, where a threshold is met and then the muscle fibers contract. Invertebrate muscles can contract gradually.

Question 37

Vertebrate vs invertebrate muscle force

Answer 37

Vertebrate is an all-or-nothing response, where a threshold is met and then the muscle fibers contract. Invertebrate muscles can contract gradually.

Question 38

Variables in muscle performance

Answer 38

The trade-off between force and velocity The proportion of fast and slow-twitch fibres Physiological cross-sectional area Energy storage by tendons.

Question 39

Vmax

Answer 39

Occurs when there is no weight. The fastest rate of contraction.

Question 40

Type 1

Answer 40

Slow fibres which fatigue slowly, are well vascularised and have large oxygen stores

Question 41

Type IIa

Answer 41

Fast fibres - little force, slow fatigue, aerobic function

Question 42

Type IIb

Answer 42

Fast fibres - large force, fatigue quickly, can function unaerobically

Question 43

Fast-twitch vs slow twitch

Answer 43

Fast-twitch has higher Vmax, generates more force, but requires more energy.

Question 44

Compared with contraction at Vmax, biceps contracting at half Vmax generate

Answer 44

More force

Question 45

What occurs during a muscle contraction?

Answer 45

Generation of heat Shortening of sarcomeres Thickening of muscle due to contraction