Lecture 7: Muscles

Question 1

what are striated muscles associated with?

Answer 1

skeleton, external musculature of limbs, trunks, and jaws
- has the most massive cells in the body
- strong contractions
- voluntary activation

Question 2

what are red muscles?

Answer 2

rich in myoglobin, gives endurance due to the oxygen-storing protein

Question 3

what are white muscles?

Answer 3

poor in myoglobin, better for contraction

Question 4

what are smooth muscles associated with?

Answer 4

viscera
- activation by hormonal signals
- mononucleate cells that form around organs

Question 5

what are cardiac muscles?

Answer 5

striated muscles that occur in the heart
- coordinated contractions
- activation by hormonal signals

Question 6

what muscles develop from mesenchyme?

Answer 6

smooth muscles of blood vessels

Question 7

what muscles develop from sphlanchnic layer of the hypomere?

Answer 7

• smooth muscles of digestive tract
• cardiac muscle of heart

Question 8

what muscles develop from somatic layer fo hypomere?

Answer 8

skeletal muscles of limbs

Question 9

what muscles develop from somitomeres?

Answer 9

skeletal muscle of head and branchial arches

Question 10

what muscles develop from myotomes of somites?

Answer 10

most skeletal muscles

Question 11

how are limb muscles produced?

Answer 11

myotome and hypomere cells migrate into the developing limb

Question 12

how are skeletal muscles organized?

Answer 12

muscles > fascicles > muscle cells (fibres) > myofibrils

Question 13

what are examples of collagenous sheaths?

Answer 13

• epimysium around muscles
• perimysium around fascicles
• endomysium around cells

Question 14

how are contractions caused in skeletal muscles?

Answer 14

sliding of filaments against one another

Question 15

how does the striated appearance form in skeletal muscles?

Answer 15

alternation between myosin-bearing and myosin-free parts of sarcomere

Question 16

what are tendons?

Answer 16

extensions of skeletal muscle membranes that connect muscle to bones
- help save weight and energy
- cursorial tetrapods

Question 17

define resting state

Answer 17

no force is produced

Question 18

define active state

Answer 18

force is produced - muscles contract if tension is able to overcome resistance

Question 19

define tetanus

Answer 19

sustained maximal activation

Question 20

how does passive force occur?

Answer 20

muscles are stretched beyond resting length

Question 21

define motor units

Answer 21

one motor neuron and the set of muscle fibres it innervates

Question 22

what are examples of fibre orientations?

Answer 22

• parallel: parallel to the line of tension
• pinnate: oblique to the line of tension

Question 23

muscle names are based on..

Answer 23

direction of fibres, shape, position, number of divisions, and function

Question 24

actions performed by muscles: change in joint angle

Answer 24

flexion: decreases angle
extension: increases angle

Question 25

actions performed by muscles: motion relative to body midline

Answer 25

abduction: moves away adduction: moves towards

Question 26

actions performed by muscles: motion relative to horizontal

Answer 26

elevation: raises body part depression: lowers body part

Question 27

actions performed by muscles: forward and backward movement

Answer 27

protraction: forward retraction: backward

Question 28

actions performed by muscles: rotation of a body part

Answer 28

supination: turns palms upward pronation: turns palms downward

Question 29

actions performed by muscles: diameter of an opening

Answer 29

dilation: widens constriction: narrows

Question 30

define torque

Answer 30

- muscle force x muscle arm movement - "moment"

Question 31

define moment arm

Answer 31

distance from joint's centre of rotation to muscle's line of action - large = slow, limited joint rotation - trade off between torque and speed

Question 32

interactions: define synergists

Answer 32

promote the same motion

Question 33

interactions: define antagonist

Answer 33

promote opposite motions

Question 34

interactions: define fixators

Answer 34

stabilize a joint being acted on by other muscles

Question 35

multiple function: they can..

Answer 35

cross multiple joints, merge, bifurcate, share a tendon, and give rise to multiple tendons

Question 36

what are branchiomeric muscles?

Answer 36

- jaw and pharyngeal walls - from somitomeres

Question 37

what are hypobranchial muscles?

Answer 37

- median part of pharyngeal floor - from anteroventral extensions of cervical somites

Question 38

what are three branchiomeric muscles?

Answer 38

mandibular arch muscles, hyoid arch muscles, and branchial arch muscles

Question 39

where can you find hypobranchial muscles?

Answer 39

- fish: connect pectoral girdle to pharyngeal arches - tetrapods: throat, hyoid, larynx, tongue

Question 40

what are the functions of extrinsic eye muscles?

Answer 40

rotate eye - from preotic somitomeres - extend from bony wall to outer surface of eye

Question 41

how are axial musculature formed?

Answer 41

1. develops from myotome 2. myotome extends ventrally during development 3. splits into a dorsal and ventral block

Question 42

what separates the epaxial and hypaxial in fish?

Answer 42

horizontal septum myomeres are separated by myosepta

Question 43

what are the axial are present in salamanders?

Answer 43

epaxial: dorsalis trunci hypaxial: distinct muscles myosepta and septum present

Question 44

what are the axial are present in reptiles?

Answer 44

septum is lost and myosepta is reduced hypaxial: intercostal axial: reduced in birds

Question 45

what are the axial are present in mammals?

Answer 45

muscles are reduced

Question 46

what is an example of a hypaxial muscle?

Answer 46

rectus abdominis

Question 47

what is the development of appendicular musculature in fish?

Answer 47

ventral tips of myotomes extend into developing fin

Question 48

what is the development of appendicular musculature in teleosts and tetrapods?

Answer 48

mesenchyme from ventral tips of myotomes migrate into developing fin

Question 49

what are examples of dorsal muscles?

Answer 49

- scapula - posterior surface of upper arm - wrist - digit extensors

Question 50

what are examples of ventral muscles?

Answer 50

- chest - anterior surface of upper arm - wrist - digit flexors

Question 51

what are examples of superficial shoulder muscles?

Answer 51

- branchiomeric - ventral appendicular - dorsal appendicular

Question 52

how does the supracoracoideus facilitate locomotion?

Answer 52

scc tendon uses the coracoid as a pulley to elevate the humerus

Question 53

what does the pectoral "muscular sling" do?

Answer 53

suspends anterior part of trunk from pectoral girdle and humerus

Question 54

why are there no muscular slings in pelvic girdle?

Answer 54

because they're fixed to vertebral column by sacral ribs

Question 55

what specialized muscles do anurans have?

Answer 55

large hindlimbs for jumping and stout pectoral limbs for landing

Question 56

what specialized muscles do cursorials have?

Answer 56

appendicular muscles and long tendons

Question 57

what specialized muscles do birds have?

Answer 57

reduced axial and enlarges appendicular pectoral muscles proximal large ventral appendicular pectoral muscles