Chapter 10 Part 2

Question 1

Convergent msucle shape

Answer 1

fibers roughly parallel, converge at either end of muscle

Question 2

Pennate muscle

Answer 2

oblique fiber arrangement inserting into tendons

Question 3

Unipennate

Answer 3

• pennate
  fibers insert into one side of a tendon insertion

Question 4

Bipennate

Answer 4

fibers insert into both sides of a centrally-located tendon

Question 5

Multipennate

Answer 5

– fibers insert into several tendons
o Best for moving a heavy load a short distance
o Pinnate orientation permits the packing of more fibers within the same volume than the parallel arrangement does

Question 6

Fiber orientation in muscle shapes

Answer 6

o Pinnate orientation permits the packing of more fibers within the same volume than the parallel arrangement does
o The oblique orientation of fibers in pinnate muscles reduces the effective distance through which the insertion can be moved and slightly reduces the force that each fiber can direct along the line of action
o The greater overall number of fibers compensates and makes pinnate muscles especially suited for moving heavy loads short distances

Question 7

Muscle lengths

Answer 7

o A short muscle that contracts to half its resting length shortens by the distance x1
o A long muscle contracting to half its length will do so in the same amount of time if it is made up of the same type of sarcomeres
o The contraction speed of chains of sarcomeres is additive, producing a faster speed over a longer distance (x2)
o When fast displacement is required, long muscles are often involved

Question 8

Describe how the placement of the distal insertion influences strength and speed

Answer 8

• A muscle inserted on different points in a lever system produces different mechanical advantages
• Distal insertion influences strength, proximal insertion influences speed
• Proximal insertion of muscle allows more movement than distal insertion of muscle

Question 9

Muscles being synergists or Antagonists

Answer 9

Synergists: Muscles that act together to produce motion in the same general direction, The biceps brachii and brachialis muscles of the upper human arm are synergists in the action of flexing the forearm
Antagonists: Muscles that produce opposing motions
The biceps brachii on one side of the upper arm and the triceps brachii on the other are antagonists.

Question 10

Muscle homology

Answer 10

• Similar function between muscles suggests homology:
• The posterior shank muscles of the frog and reptile extend the foot. Although this muscle is thought to be the gastrocnemius, the insertions are slightly different in each animal
• The depressor mandibulae and the digastric muscles depress the lower jaws of reptiles (alligator) and mammals (opossum), but the nerve supply to these muscles is different, suggesting that the two are not homologous
• A common embryonic pattern of development is often used to establish muscle homologies.

Question 11

Name the three different developmental origins of muscle

Answer 11

somatic , visceral, and branchiomeric

Question 12

Somatic

Answer 12

Derived from myotomes ; include body wall, tail, hypobranchial, tongue, extrinsic eye, and most of the appendicular muscles

Question 13

Visceral

Answer 13

Derived from from the splanchnic layer of the hypomere (lateral plate);includes erectors of feathers and hair, muscles of the gut, blood vessels, and viscera, and heart muscle

Question 14

BRanchiomeric

Answer 14

from pharyngeal arches and their derivatives

Question 15

Axial muscles

Answer 15

• of fishes: supplies the major propulsive forces for locomotion, constitutes the bulk of the body’s musculature

Question 16

What are 2 groups of axial muscles?

Answer 16

epaxial and hypaxial

Question 17

Epaxial muscles in fish

Answer 17

o Myomeres are folded into zigzag blocks that often look V- or W-shaped
o Muscle fibers \are short - this folded shape of each myomere extends over several axial segments, giving it and its short fibers control over an extended length of the body

Question 18

Epaxial muscles in urodeles, lizards

Answer 18

relatively undifferentiated muscle mass, the dorsalis trunci
o more seen in salamanders than frogs

Question 19

Epaxial muscles in tetrapods

Answer 19

iliocostalis, longissimus, spinalis

Differentiated into several specialized roups of muscles o	Elongated bundles that extend through multiple body segments o	Deep groups still segmented

Question 20

Name three major epaxial muscles

Answer 20

• Spinalis: attached to vertebral spines; cervicis part by head and dorsi by pelvic region
• Longissimus: middle muscle down back, longest; cervicis part by head and dorsi by pelvic region
• Iliocostalis:

Question 21

Name hypaxial muscles in urodeles

Answer 21

external intercostals, internal intercostals, transversus, rectus abdominis