[2] Lecture 12: Comp. Anatomy Of Musculature I Flashcards
All movements in the human body involves
Muscular contraction
All muscular contractions consist of:
Motor actions
Contractions of heart and vessels
Actions in the intestines
Muscle tissue classified based on characteristics such as:
Appearance, arrangement of nucleus, function
Most common classification system is based on what 2 characteristics:
Microscopic appearance
And
What organ it is asso. W/
4 types of muscle tissue:
Skeletal, cardiac, smooth, branchiomeric
Striated or band subunit appearance
Voluntary control
Attached to sketch system directly/indirectly
Mononucleated cells (myoblasts)
Skeletal muscle
Not striated Generally involvuntary Spindle-shaped mononucleated cells Centrally located nuclei Most commonly asso. W/ viscera
Smooth muscle
Shares characteristics w/ skeletal and smooth muscle Striated Involuntary Mononucleated and striated Specialized junctions for syncytium
Cardiac muscle
Specialized intercellular junctions in cardiac muscle
Intercalated discs
Asso. W/ pharyngeal arches
Transition btw smooth muscle and striated muscle
Innervated by cranial nerves
Branchiomeric muscle
Shapes of muscle involved in naming:
Fusiform (spindle-shaped) Pinnate: -unipennate -bipennate -multipennate
Besides shape, what’re some other ways of naming muscle:
Action Location Number of heads Fiber direction Relative size Origin-insertion
Proximal attachement
Usually…
May be fixed w. Regard to movement
Origin
Distal attachement
Usually…
Usually more movable
Insertion
Attachement btw muscle and bone Dense collagenous CT Surrounded by peritendineum Bundles of collagen fibers Poorly vascularized
Tendons
Flat, fan-shaped tendons typically giving rise to other tendons
Aponeuroses
Consists of sarcomeres:
Which consist of myosin-thick and actin-thin
Myofilament
Chain of sarcomeres
Myofibril
Bundle of myofibrils
Often referred to as muscle cell
Each fiber formed from many fused myoblasts
Myofiber
Bundle of myofibers
Fascicle
Composed of varying numbers of fascicles
Muscle
Surrounds each muscle fiber
Lies outside sarcolemma
Endomysium
Surrounds each fascicle
Perimysium
surrounds each muscle
Becomes continuous w/ tendons
Attached to periosteum
Epimysium
What makes up myofilament?
Actin and myosin
Muscle fiber will either contract completely or not at all
All or none principle
After birth the number of myofibers:
Can not be increased
What can be increased in muscle?
You can increase number of myofibrils…there for a myofiber and muscle may beincreased in size
What happens to lost muscle?
Replaced by scar tissue (fibrous CT)
A single nerve cell may innervate from a few to several hundred myofibers:
Motor units — all or none
Want maximal contraction of muscle?
More recruitment=more motor units incvolved
All or none really refers to:
Motor unit involvement
Myofiber type is determined by:
Innervation neuron
All myofibers in a single motor unit will be same ____
Type
Fiber type is based on :
Endurance
2 types of muscle fibers
Dark-slow fibers (red)
Light-Fast (white)
Found in all vertebrate groups
Not multiple innervated
Do not propagate AP
Phasic fibers
Found in non-mammalian vertebrates
Involved in slow, sustained postural activities **
Single nerve cell innervates many fibers- each fiber is INNERVATED MULTIPLE TIMES (>1 innervation)
Contract slowly
Do not propagate an AP
Tonic fibers
We do not have….
Dark fibers ex of muscle:
Soleus
Stroll w/ the sol
Predominantly composed light fibers:
Gastrocnemius
contraction length of muscle doesnt change
Isometric, but force of contraction increases
Contraction length of muscle does change:
Isotonic contraction
contraction muscle gets shorter:
Concentric
Contraction muscle get longer:
Eccentric contraction
Basis for names of muscles:
Shape, origin-insertion, function, relative size, fiber arrangement, location
Fiber arrangement:
Straight, fusiform, unipennate, bipennate, multipennate
Result of the muscle contraction depends on:
Muscle attachment
Which end of muscle is fixed
Force of contraction r/t force of distance
Simultaneous action of muscles around other muscles asso. W/ same structure
How is stability of a bone at a given time is determined by:
Contractions of muscles acting as stabilizers
Muscle doing desired action
Agonist
Muscle that opposes the agonist
Antagonist
Muscle that stabilizes base of attachment of agonist
Fixator
Muscle that crosses only one joint
Unijoint
Muscle that crosses more than one joint
Multijoint
Inability of a multijoint muscle to contract maximally over all joints crossed simultaneously:
Insufficiency
Muscle that eliminates unwanted action by the agonist
Synergist
Insufficiency r/t the reference of agonist
Active insufficiency
Insufficiency r/t the reference of the antagonist
Passive insufficiency
Insufficiency doesnt affect what type muscle?
Unijoint…..only multijoint
Prime movers and assistant movers
Agonist muscles
A muscle primary function is to cause the particular movement and a strong contributor to that movement:
Prime mover
Has the ability to assist in the movement but is only of secondary importance to the movement
Assistant mover
Acting as a stabilaizer (fixator) usually contracts as:
Isometrically
Muscles that pass anterior to the axis of a joint are
Flexors
Muscles that pass posterior to axis of a joint are
Extensor
Muscles that pas lateral to a joint are:
Abductors
Muscle flexor can shorten about:
1/2 total length
Muscles that nullify one or more actions of another muscle:
Synergist— Neutralizer
Cause opposite motion of the prime mover w.o assisting in the movement:
Synergistic-neutralizer
One that extends across more than one joint and potentially can contribute to movement at each joint it crosses
Multijoint muscle
