Muslces
Group 4
Classification
 Agonist:
prime mover
 Antagonist:
 Synergist:
 Fixator:
mover
reverses agonist
prevents rotation
stabilizes the origin of the prime
Naming (LADSNOR!)
 Direction of the muscle fibers
 Ex) transverse, rectus, oblique
 Relative size of
 Ex) major, minor
muscles
 Location
 Number
and location of origin
 Shape
 Action of the muscle
 Ex) extensor, flexor
Origin and Insertion
Origin:
immovable end
Insertion:
movable end
Characteristics
 Muscle
cells are elongated
 Contractions
are due to the movement of
microfilaments
Structure (skeletal muscle)
Structure (cont.)
 From
outermost to innermost
 Muscle>Fascicles>Muscle
fibers>Myofibril>Thick and thin filaments
 Fascia>Epimysium>Perimysium>Endomysiu
m
Tissue layers of a skeletal
muscle
 Fascia:
covering the whole muscle
 Epimysium:
lies beneath the fascia
 Perimysium:
separates cells of fascicle
 Endomysium:
fibers
separates individual muscle
Fascicle
 Collection
of muscle fibers
 Covered by blood vessels and axon of
motor neurons
 Each muscle fibers is separated by
endomysium
 It is surrounded by sarcolemma
 Contains nucleus and sarcoplasmic
reticulum
 Each muscle fibers is composed of
myofibril
Myofibril & Sarcomere
Sarcomere
 It
is a repeating pattern formed by
striations
Sarcomere (cont.)
 Troponin:
protein that works with
tropomyosin to block muscle contraction
until calcium ions are present
 Transverse
tubule: set of membranous
channels that contain extracellular fluid
Smooth muscle
 It
is shorter than skeletal muscle, and has
single centrally located nuclei
 It
 It
lacks troponin
alternates between a state of relaxation
and contraction
Cardiac muscle
 Composed
of striated cells, containing a
single nucleus
 It
has a well developed sarcoplasmic
reticulum
 Its
transverse tubule is larger than skeletal
muscle’s
Contraction
 Acetylcholine(ACh)
is the
neurotransmitter that contracts skeletal
muscles
 ACh binds with receptors on the motor
endplate, which causes muscle impulse
 Calcium ions diffuse from sarcoplasmic
reticulum to sarcoplasm and binds to
troponin
Contraction (cont.)
 Tropomyosin
moves, which allows actin
and myosin to link
 Actin is pulled to the center of the
sarcomere, which allows muscle fibers to
shorten
Threshold
Respiration
 Anaerobic
breaks down glucose
and releases ATP
 Aerobic
requires oxygen to
produce ATP
Oxygen debt
 When
cellular respiration is not able
to sustain the muscle, lactic acid
diffuses into the blood stream
 This
creates an oxygen debt, that
must be repaid later
Muscle fatigue
 When
a muscle loses its ability to
contract
 Most
likely occurs from
accumulation of lactic acid
Types of contraction