Lecture 7: Muscles Flashcards
what are striated muscles associated with?
skeleton, external musculature of limbs, trunks, and jaws
- has the most massive cells in the body
- strong contractions
- voluntary activation
what are red muscles?
rich in myoglobin, gives endurance due to the oxygen-storing protein
what are white muscles?
poor in myoglobin, better for contraction
what are smooth muscles associated with?
viscera
- activation by hormonal signals
- mononucleate cells that form around organs
what are cardiac muscles?
striated muscles that occur in the heart
- coordinated contractions
- activation by hormonal signals
what muscles develop from mesenchyme?
smooth muscles of blood vessels
what muscles develop from sphlanchnic layer of the hypomere?
- smooth muscles of digestive tract
- cardiac muscle of heart
what muscles develop from somatic layer fo hypomere?
skeletal muscles of limbs
what muscles develop from somitomeres?
skeletal muscle of head and branchial arches
what muscles develop from myotomes of somites?
most skeletal muscles
how are limb muscles produced?
myotome and hypomere cells migrate into the developing limb
how are skeletal muscles organized?
muscles > fascicles > muscle cells (fibres) > myofibrils
what are examples of collagenous sheaths?
- epimysium around muscles
- perimysium around fascicles
- endomysium around cells
how are contractions caused in skeletal muscles?
sliding of filaments against one another
how does the striated appearance form in skeletal muscles?
alternation between myosin-bearing and myosin-free parts of sarcomere
what are tendons?
extensions of skeletal muscle membranes that connect muscle to bones
- help save weight and energy
- cursorial tetrapods
define resting state
no force is produced
define active state
force is produced - muscles contract if tension is able to overcome resistance
define tetanus
sustained maximal activation
how does passive force occur?
muscles are stretched beyond resting length
define motor units
one motor neuron and the set of muscle fibres it innervates
what are examples of fibre orientations?
- parallel: parallel to the line of tension
- pinnate: oblique to the line of tension
muscle names are based on..
direction of fibres, shape, position, number of divisions, and function
actions performed by muscles: change in joint angle
flexion: decreases angle
extension: increases angle
actions performed by muscles: motion relative to body midline
abduction: moves away
adduction: moves towards
actions performed by muscles: motion relative to horizontal
elevation: raises body part
depression: lowers body part
actions performed by muscles: forward and backward movement
protraction: forward
retraction: backward
actions performed by muscles: rotation of a body part
supination: turns palms upward
pronation: turns palms downward
actions performed by muscles: diameter of an opening
dilation: widens
constriction: narrows
define torque
- muscle force x muscle arm movement
- “moment”
define moment arm
distance from joint’s centre of rotation to muscle’s line of action
- large = slow, limited joint rotation
- trade off between torque and speed
interactions: define synergists
promote the same motion
interactions: define antagonist
promote opposite motions
interactions: define fixators
stabilize a joint being acted on by other muscles
multiple function: they can..
cross multiple joints, merge, bifurcate, share a tendon, and give rise to multiple tendons
what are branchiomeric muscles?
- jaw and pharyngeal walls
- from somitomeres
what are hypobranchial muscles?
- median part of pharyngeal floor
- from anteroventral extensions of cervical somites
what are three branchiomeric muscles?
mandibular arch muscles, hyoid arch muscles, and branchial arch muscles
where can you find hypobranchial muscles?
- fish: connect pectoral girdle to pharyngeal arches
- tetrapods: throat, hyoid, larynx, tongue
what are the functions of extrinsic eye muscles?
rotate eye
- from preotic somitomeres
- extend from bony wall to outer surface of eye
how are axial musculature formed?
- develops from myotome
- myotome extends ventrally during development
- splits into a dorsal and ventral block
what separates the epaxial and hypaxial in fish?
horizontal septum
myomeres are separated by myosepta
what are the axial are present in salamanders?
epaxial: dorsalis trunci
hypaxial: distinct muscles
myosepta and septum present
what are the axial are present in reptiles?
septum is lost and myosepta is reduced
hypaxial: intercostal
axial: reduced in birds
what are the axial are present in mammals?
muscles are reduced
what is an example of a hypaxial muscle?
rectus abdominis
what is the development of appendicular musculature in fish?
ventral tips of myotomes extend into developing fin
what is the development of appendicular musculature in teleosts and tetrapods?
mesenchyme from ventral tips of myotomes migrate into developing fin
what are examples of dorsal muscles?
- scapula
- posterior surface of upper arm
- wrist
- digit extensors
what are examples of ventral muscles?
- chest
- anterior surface of upper arm
- wrist
- digit flexors
what are examples of superficial shoulder muscles?
- branchiomeric
- ventral appendicular
- dorsal appendicular
how does the supracoracoideus facilitate locomotion?
scc tendon uses the coracoid as a pulley to elevate the humerus
what does the pectoral “muscular sling” do?
suspends anterior part of trunk from pectoral girdle and humerus
why are there no muscular slings in pelvic girdle?
because they’re fixed to vertebral column by sacral ribs
what specialized muscles do anurans have?
large hindlimbs for jumping and stout pectoral limbs for landing
what specialized muscles do cursorials have?
appendicular muscles and long tendons
what specialized muscles do birds have?
reduced axial and enlarges appendicular
pectoral muscles proximal
large ventral appendicular pectoral muscles
