Human Anatomy and Physiology-Chapter 6:Muscular System Notes
I.Overview of Muscle Tissues
 Differ in cell structure,location, and how they are stimulated to
contract
 Smooth and skeletal muscle cells are elongated and called
________________________
 Contraction-shortening-depends on 2 types of myofilaments
 Terms myo-,sarco- and mys- refers to muscle-example-muscular
cytoplasm is called ___________________.
A. skeletal muscle
 attach to skeleton and form smoother contours of body
 huge,cigar shaped and ______________________
 largest of muscle fibers-as much as 30 cm in length
 __________________________with obvious stripes
 ______________________________since only muscle subject to conscious
control
 However,subject to involuntary reflexes
 Tire easily and requires rest
 Fairly fragile
 Bound by ___________________________which provides strength and
support
 Each muscle fiber contained in a declicate connective tissue sheath called
___________________________
 _________________________-connective tissue wrapping a bundle of
fibers called a _________________
 ___________________________= many fascicle bound together w/ this
tough coat
 Epimysia blend into the strong_,cordlike_________ or aponeurose that
connect muscle to bones,cartilages or connective tissue
 Other functions of tendons-besides movement-are durability and
conservation of space
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B. Smooth Muscle
 No striations and is involuntary
 Mainly in walls of hallow visceral organs such as
___________________________________________________
_________________________________
 Propel substances on a definite tract or pathway
 Spindle shaped and uninucleate
 Scant endomysium
 Most often in 2 layers-one running circularily and one running
longitudinally-alternately contract or relaxing changing size
and shape of organ
C. Cardiac Muscle
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




Only in heart
Forms most of heart walls
________________________but involuntary
Cushioned in bundles w/ small amount of endomysium
When heart contracts,internal chambers get smaller,forcing
blood into arteries leaving heart
 Branching cells joined by junctions___________________________________These traits and
spiral arrangement of bundles allow heart activity to be closely
coordinated,giving steady contraction rate
 ______________________can shift heart into “high gear”
****** We focus mostly on skeletal muscle here!
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D. Muscle Functions
1. _______________________as a result of muscle
contraction;quick response to environment
2. Maintaining _____________-maintain erect posture despite
gravity
3. Stabilizing ________________-esp. w/ poorly fitting
articulating surfaces as in shoulder
4. _________________________________-by –product of
muscle activity;ATP used for contractions and ~40% released
as heat to mostly maintain normal body temp for at least 40%
of body mass
II. Microscopic Anatomy of Skeletal Muscle
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a. ________________________ = plasma membrane of
muscle cells
b. Nuclei pushed aside by ________________-long
ribbonlike organelles;have alternating light (I) and
dark (D) bands along myofibrils-give striped
appearance
c. I band has midline interruption darker__________________
d. A band has lighter central area called
_____________-Its M line contains tiny protein rods
that hold thick filaments together
e. Myofibril actually chains of contractile units_____________________-line up end –to- end along
myofibril length
f. 2 type of protein myofilaments-larger is
___________________ made of bundled myosin
–extend length of A band
g. Also contain ATP enzymes to generate ATP or
energyh. Ends studded w/ small projections____________________________
i. Thin filaments composed of ______________-called
actin filaments-anchored to z disc-do not extend into
end of relaxed sarcomere,so central region_________________is sometimes called bare zone
j. In a contraction,bare zone does not appear because
actin and myosin completely overlapped
k. ______________________________(SR)-specialized
smooth ER-tubules and sacs surround every
myofibril-picture a crocheted sleeve-Role is
to_________________________________________
_________________________________
III. Skeletal Muscle Activity
A. Stimulation and Contraction of Single Muscle Cells
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 Functional properties include
1)___________________(irritability/responsiveness)-ability to receive
and respond to stimulus
2) _______________________-ability to forcibly shorten when stimulated
3) _________________________-ability of muscle cells to stretch
4)__________________________-ability to recoil and resume resting
length
Nerve stimulus and Action Potential:
 Must receive nerve stimulus
 May be a few or 100’s of muscles cells stimulated by a nerve
cell______________________
 _____________________= 1 neuron and all skeletal muscles
stimulated
 __________-long extension of nerve cell-branches into axon
terminals when it reaches muscle,each forming a junction
w/sarcolemma=_________________junctions
 Nerve and muscle are close but do not totally meet-forming
____________________(has interstitial fluid)
 When nerve impulse reaches terminals___________________________is released-Ach________________________in the case of skeletal muscles
 AAh attaches to receptors(membrane proteins)part of
sarcolemma.With enough Ach ,sarcolemma is more permeable to
Na+ that diffuse out of cell….more Na enters than K+ leaves---creates a current called ___________________________-now
unstoppable-result in muscle contraction
 Ach is broken down into ____________________________by
enzymes acetylcholinesterase-AChE-during action potential,so
one impulse makes one contraction
 Returns to resting state by…
1. diffusion of ___________out of cell
2. operations of ________________pumping NA+ and K+ ions back to
original position
B. Mechanism of Muscle Contraction
 _________________________TheoryWhen muscle fibers
are activated by nervous system,myosin heads attach to
binding sites on thin filaments and sliding begins.Each cross
bridge attach and detach several times during a contractionpulling filaments towards center of sacromere and cell
shortens
 The movement of myosin cross bridges is somewhat like that
of a centipede
 The attachment of myosin cross bridges to actin requires
Ca2+ ions,which come from inside the cell where action
potentials stimulate sarcoplasmic retuiculum to release Ca2+
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into cytoplasm.this triggers the binding of myosin to actin
causing filaments sliding
 When action potential ends,Ca2+ ions are reabsorbed into SR
storage areas and muscle cell relaxes
C. Contraction of skeletal muscles as a whole
 Whole muscle responds to “all or none principle”,but whole
muscle reacts in _____________________
 Can be changed by ________________________of muscle
stimulation and by changing # muscle fibers stimulated
 ____________________________=brief jerky contractions
 Normally,nerve impulses are delivered at a very fast rate w/o
much relaxation
 Smooth,rapid sustained contractions called _____________or
complete,tetanus
 Until complete tetanus is reached,the muscle is said to be
______________________________tetanus
 Muscle contractions can be slight or vigorous depending on
work to be done and thus innervation
 Energy for muscle contractions-needs to make ATP:
1. Direct phosphorylation of ADP by creatine phosphate(CP)found in ____________________but not other cell
types.As ATP is used,reactions between CP and ADP
generates more ATP.(CP supply quickly exhausted
2. _____________________-for light to moderate
exercise,95% ATP comes from aerobic-cellular respirationfrom mitochondrion….the collection of chemical pathways
are also called
____________________________________.Glucose
broken down to CO2 and H2O 36 ATP/1 g glucose-fairly
slow and requires continuous O2.
3. ________________________________________________
_________________________- occurs to provide pyruvic
acid fro cell respiration---occuring in cytosol.After this
,w/o O2,fermentation via production of
_______________________occurs-5% of ATP from each
glucose-promotes muscle fatigue and soreness
 ___________________________occurs if muscle is unable to contract
even though it is still innervated…usually caused from
___________________________________________ during prolonged
muscle activity….alot dependent on muscle supply….breathing rapidly
and deeply will generate more ATP
 Types of Muscle contractions:
1. ________________________________-myofilaments are
successful in sliding movements,muscle shortens and causes
movement-eg. Knee bending
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2. _______________________________________-myosin
myofilaments are “spinning their wheels”and tensions
continually increases
-trying to slide but you are attempting to move something
immovable
 ____________________________--state of continuous partial
contraction-firm and ready for action
 ____________________- muscle is not innervated and becomes soft and
flabby
 ___________wasting away of a muscle
 Aerobic –or endurance-exercise-results in stronger,more flexible muscles
and subjected to less fatigue(jogging,biking)-results partly because of
greater blood supply-also enhances metabolism in general-improving
digestion,elimination,coordination and cardiovascular system………..but
does not increase muscle size mush
 Resistance –or ______________________exercises increases muscle sizeincrease individual muscle cell size(make more contractile filaments and
increases connective tissue)
IV.Muscle Movements,Types and names
A. Types of Body Movement
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1.
2.
3.
4.
 Every one of our 660+skeletal muscles is attached to bone or
other connective tissue at no fewer than 2 points:
1. ____________attached to immovable or less movable
bone
2. ______________attached to more movable bone
 Muscle moves toward origin in contraction
 Most common movements:
1. ___________________movement mainly in sagittal plane
that decreases < of joint and brings 2 bones closer togethereg.knee and elbow
2. ____________________opposite of flexion and increases
>-eg straightening knee
3. ________________________movement of bone around
longitudinal axis-eg in ball- and- socket joints
4. __________________________-moving limb away from
midline
5. ___________________________opposite of abductiontoward bodyline
6. ___________________________-combination of
flexion,extension,abduction,adduction commonly seen in
ball-and socket-proximal end of limb is stationary,and its
distal end moves in a circle-outlines a cone
B.Special Movements
____________________________-Up and Down movement of foot at ankle:pulled
toward shin is dorsiflexion and pointing towards toe is plantar flexion
_____________________________invert turn sole medially and evert,turn sole
laterally
___________________________________-supination-turn backwards @ radius and
ulna-forearm rotates laterally to turn palm anterior laterally-radius and ulna
parallel/pronation when forearm rotates medially-palm faces posterior-radius and ulna
form X.
___________________________-opposition from saddle joint in hand-moves ththumb
to touch other fingers
C. Interactions of Skeletal Muscles in the Body
 Muscles can only pull
 ____________________________-major muscle responsible for designated
movement
 _________________________ -oppose or reverse a movement
 __________________________-help prime movers by doing same movement
or reducing undesirable movement-example:making a fist w/o moving wrist
 Fixators-specialized synergists-hold a bone still or stabilize origin of prime
mover so all tension used to move insertion bone
D. Naming skeletal muscles
1. Direction of muscle fibers-in re to an imaginary line-examplerectus(straight)-rectus femoris-straight muscle of thigh
2. _____________________________________-maximus,minimus,longus
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3. location of muscle-associated bone used in name often eg-temporalis
muscle overlies temporal bone
4. _____________________________________-eg. Biceps-2 origins
5. Location of muscle’s origin and insertion-eg.sternocleidomatstoid-origin
in sternum and clavicle-inserts in mastoid process of temporal bone
6. _________________________________-eg.deltoid means triangular
7. _________________________________-eg-flexor
E. Arrangement of Fascicles
1. ________________-fascicles in concentric circles(spinchters)
2. __________________-meet at a single insertion-triangular or fan shaped
3. ________________________-parallel to long axis of muscle
4. __________________________-spindle –shaped muscle w/expanded center(biceps
brachii)
5. _____________________-short fascicles attach obliquely to a central tendon
V.MAJOR MUSCLES TO REMEMBER
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