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Martini et al. Chapter 9
Study of muscular tissue
(mus = mouse, -cle = little)
What are the Muscular Tissues like?
Excitability (irritability)
Skeletal* muscle tissue
striated & voluntary
studied as the muscular system
Cardiac muscle tissue
striated & autorhythmic
Smooth muscle tissue
nonstriated & involuntary
body parts (or substances in body)
body parts (or substances in body)
Heat production
basal metabolic rate & shivering
Skeletal muscles are organs
Muscle cells are called “fibers”
Nervous tissue -> sensory & motor neurons
Blood vessels (lined by epithelia)
Connective tissues wrappers
Each cell/fiber is covered by C.T. endomysium
bundles of cells are “fascicles”
Fascicles are surrounded by perimysium
Whole muscles are held together by epimysium
Tendons or aponeuroses extend from muscles
direct or indirect attachments usu. to bone
Deep fascia fills in between muscles
Superficial fascia fills in between muscle & skin
myosin & actin
Muscle cells are “excited” by nervous tissue
A motor neuron stimulates multiple cells
Small units are for precise movements
Large units are for powerful movements
Muscles have many dif. sized motor units
Point of excitement = neuromuscular junction
Distal tips of motor neuron = axon terminals
neurotransmitter (ACh) crosses synaptic cleft
acetylcholine binds to motor end plates of
A very long slender cylindrical cell
Cell membrane = sarcolemma
Cytoplasm = sarcoplasm
containing lots of mitochondria & glycogen
multiple* peripheral nuclei
myofibrils: contractile organelles
striated & made of sarcomeres
sarcoplasmic reticulum: SER filled w/Ca
transverse tubules: connect sl to sr
Sarcomere: a section of a myofibril
Striations = pattern of myofilaments
thick “myosin” & thin “actin”
Z discs
A & I bands
H zone
M line
Calcium “frees-up” the myosin heads
they repeatedly “pull actin” toward M-line
Z discs also move toward M-line
I bands & H zone disappear
A band length remains constant
Lack of Ca = relaxed muscle
antagonist can extend sarcomeres
Red/Slow twitch (posture)
aerobic: needs oxygen & glucose to make ATP
lots of blood, myoglobin & mitochondria
White/Fast Twitch (power)
anaerobic: works briefly from stored supplies
less blood, glycogen inclusions
Intermediate Fast Twitch (lower limbs)
All muscle have combination of types
Shorter branched cells
branched myofibrils = harder to see striations
Intercalated discs
Long refractory period, no tetanus
No parallel myofilaments
intermediate filaments maintain cell shape
Single-unit vs. multiunit types
sheet all contracts due to gap junctions
groups of cells are innervated (arrector pili
Muscle changes throughout life