Muscles Flashcards
When a myofiber is damaged it is replaced by ___________, but when the muscle grows it increases in_______________.
A). Scar tissue, myofiber
B). Myofiber, Myofiber
C). Scar tissue, myofibrils
D). Myofiber, myofibrils
C). Scar tissue, Myofibrils
Scar tissue fills in the crack, it is a non-contractile fibrous connective tissue
Myofibrils - increase in myofibrils increases the mass of the muscle but the amount of myofiber is never increased
Myofiber is synonymous with muscle cell
A muscle fiber contracts slowly, is innervated by more than one nerve cell but cannot propogtate an action potential, what type of muscle fiber is it? What type of vertebrate is it found in?
A). Tonic fiber, all vertebrates
B). Tonic fiber, all but Mammals
C). Phasic fiber, all vertebrates
D). Phasic fiber, all but Mammals
B). Tonic fibers, all but mammals
Tonic fibers:
Found in non-mammalian vert.
Slow, sustained posture activities
Single nerve cell innervates many fibers but each fiber is innervated by more than one nerve cell
Contract slowly but do not propagate an action potential
What are the 3 types of skeletal muscle?
Axial, Braniomeric and Appendicular
Axial subs into epaxial and hypaxial, what are each innervated by?
Why is it important to know what innervates the axial muscles?
Epaxial is innervated by dorsal rami of the spinal nerves
Hypaxial is innervated by ventral rami of the spinal nerves
It’s important because the innervation is how you tell which muscle is epaxial and which is hypaxial
Where is Axial muscle derived from? What’s it’s defining characteristic?
(Hint: chordata character)
Embryonic somites
Metameric
What are Myomeres? In what organism are myomeres found? Why does this organism use them for? How are they arranged and split?
Myomeres derive from the myotome of somites, they are segments of axial musculature. They are found in fish, who use it for locomotion - swimming - their trunk muscles.
In gnathostomes the axial mytomes are split into hypaxial and epaxial.
Epaxial is the upper portion and are seperated from hypaxial by horozontal septum. -not cyclostomes
Hypaxial is the lower portion and are separated by transverse septa- which seperates entire myotomes.
What is characteristic of the transition from fish to tetrapods in terms of epaxial Musculature?
A reduction in epaxial musculature is see in tetrapods. This is because (most) tetrapods rely on their limb for locomotion rather than their trunks.
Axial muscle of Amphibians
-epaxial and hypaxial
Salamanders, necturus, still retain epaxial muscle because they do a lot of living in water so it is still needed for locomotion.
Limb muscles see an increase in mass and complexity
Hypaxial muscle functionally specializes/divided into layers:
-subvertebral
-lateral flank muscle: external oblique, internal oblique and
transversus
-Rectus abdominus (our ‘abs’)
(Have more hypaxial muscle that is divided and speacialized and less epaxial mucsle than fish but still more epaxial muscle than other tetrapods and less specialized hypaxial muscle.)
Axial muscle in Amniotes
-reptiles and mammals
Segmented epaxial: -Dorsalis truncus: arranged longitudinally \+ Spinalis \+ Longissimus \+ Iliocostals -quadrate lumborum: paired.
Segmented hypaxial:
-External and Internal obliques (intercostals)
+ Disrupted by ribs in the thoracic area, assist in breathing
By raising and lowering the ribs. -> why they are called
Intercostal muscles
-Transversus (subcostals)
-Rectus abdominus
Epaxial muscle is reduced in Turtles
What is the general trend(s) observed in the complexity of Axial muscles in the evolution of fish to amphibians to amniotes?
A general reduction in epaxial muscle.
In amphibians the hypaxial muscle is segmented
In amniotes (reptiles and mammals) both epaxial and hypaxial muscle is segmented. W/ particularly reduced expansion musculture in Turtles.
What are the subdivisions of mammalian back muscles and how are the instrinsic muscle(s) further subdivided?
How are they innervated?
Superficial
Intermediate
-Extrinsic
-Hypaxial: innervated by ventral rami
Deep
-intrinsic
-epaxial: innervated by dorsal rami
Deep intrinsic subgrouping:
- Superficial intrinsic - Intermidiate intrinsic - Deep intrinsic
These CN’s innervate which eye muscles?
Trochlear Nerve (CN IV) Abductens Nerve (CN VI Oculomotor Nerve (CN III)
Trochlear Nerve (CN IV) -superior oblique Abductens Nerve (CN VI) -Lateral rectus Oculomotor Nerve (CN III) -inferior rectus -medial rectus -superior rectus -inferior oblique
These extrinsic muscles of the eye are innervated by which CN’s?
Superior Oblique Inferior Oblique Superior Rectus Medial Rectus Inferior Rectus Lateral Rectus
Superior Oblique - Trochlear Nerve (CN VI)
Inferior Oblique - Oculomotor Nerve (CN III)
Superior Rectus - Oculomotor Nerve
Medial Rectus - Oculomotor Nerve
Inferior Rectus - Oculomotor Nerve
Lateral Rectus - Abductens Nerve (CN VI)
Branchiomeric Musculature
-What are it associations and CN innervations?
Branchiomeric Musculature is associated with the pharengeal gill arches.
Each gill arch is innervated by a cranial nerve.
Embroyonically arises from Mesenchyme.
Gill Arch I: Mandibular Arch - innervated by CN V
-trigeminal nerve
Gill Arch II: Hyoid Arch - Innervated by CN VII
-facial nerve
Gill Arch III: innervated by CN IX
-Glossopharyngeal nerve via Herring’s nerves
Remaining Gill Arches are innervated by the Vagus Nerve which is CN X
What are the muscles of mastication, what are their functions and what is their innervation?
Massenter - elevates and protracts mandible
temporalis - elevates and retracts mandible
Lateral pterygoid -portraits mandible, depresses chin. Grinding teeth
Medial pterygoid - elevates, protracts and grinding of teeth.
-innervated by CN V
-grinding is a unilateral motion.
Why is the anterior digastric muscle in mammals double innervated?
because it is derived from 2 pharengeal arches
What are the four types of muscle?
Skeletal - striated and typically voluntary. Nuclei peripheral and cells multinucleated
Smooth - spindle-shaped mononucleated cells with central nuclei
Cardiac - striated and involuntary, chains of cells that are mononucleated. Intercalated discs
Branchiomeric - associated with pharyngeal arches and innervated by cranial nerves.
What are tendons?
Attachments between muscle fibers and bone
They are dense collagen fibers and dense collagenous connective tissues
Poorly vascularized and surrounded by peritendineum