Anatomy & Physiology
Muscular System
I.
Muscles overview
A. Types of Muscles
1. _________________ – only in heart; striated; involuntary
2. _________________ – in walls of hollow organs; non-striated; involuntary
3. _________________ – attached to and covers the bones of the skeleton; striated;
voluntary
B. Muscle Functions
1. Produce ________________________
2. Maintain ________________________
3. ___________________ & _____________________ joints
4. Guard _________________& _______________ of the digestive & urinary tracts
5. Generate __________________
C. Muscle Characteristics
1. _____________________ – ability to respond to a stimulus (usually from an
associated nerve impulse)
2. _____________________ – ability to shorten & produce movement
3. _____________________ – ability to stretch when relaxed
4. _____________________ – ability to return to a normal length after being stretched
D. Muscle Information
1. Skeletal muscles account for ______% of the body weight.
2. There are over ________ muscles in the human body
II.
Skeletal Muscle
A. Gross Anatomy
1. Attachments
a. ___________________ – bone or tissue that moves as a result of contraction
b. ___________________ – bone or tissue that does not move
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c. ___________________ – fibrous connective tissue (FCT) that anchors the
muscle to a bone.
d. _____________________ – broad, flat sheet of FCT that connects a muscle to a
bone or other tissue.
2. Connective tissue coverings of a muscle
a. ____________________ – FCT that surrounds each individual muscle fiber (cell).
b. ____________________ – FCT that surround bundles of muscle fibers called
______________________________.
c. ____________________ – FCT that surrounds an entire muscle.
3. Muscle Fiber Anatomy
a. Each muscle cell is called a muscle ______________. Muscle cells are very long
(up to 12 inches) and have _____________________ in order to control them.
b. The outer cell membrane is called the ______________________.
c. The cytoplasm is called the ___________________________
d. The ER is called Sarcoplasmic Reticulum and contains extra
___________________________.
e. _________________________ is a red pigment molecule that contains extra
__________________ within the muscle cells.
f. Each muscle fiber has hundreds of ______________________
g. Myofibrils are composed of fibrous __________________ called
_________________________.
h. There are two types of myofilaments
1) ________________ – thin, white filaments
2) ________________ – thick, red filaments
i.
The myofilaments form repeating light and dark bands (which give skeletal
muscles their characteristic __________________ appearance)
j.
A single light-dark-light segment forms the Functional Unit of the muscle, which is
called a __________________________. It is at the microscopic sarcomeres
that muscle contraction occurs.
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4. Sarcomere (Draw the Picture)
5. Sarcomere contracted
a. I band disappears
b. A band remains unchanged
c. H zone disappears
d. Z lines drawn closer together
B. Sliding Filament Theory of skeletal muscle contraction
1. Thick myosin filaments are twisted together and have globular heads (proteins)
projecting from the surface. The heads are also called cross bridges.
2. Thin actin filaments contain active sites to which the heads attach during contraction.
3. During contraction the cross bridges of the myosin bind to the active sites on the
actin.
4. The myosin heads pivots and bends as it pulls the actin, thus sliding the actin toward
the M line.
5. The pivoting and bending of myosin heads requires ATP energy.
6. The myosin detaches from the actin, resets itself and then binds to a new active site
farther down the actin filament and pulls again.
7. When the muscle is resting, the proteins troponin and tropomyosin cover the active
sites on actin and prevent myosin cross bridges from binding.
8. Upon the signal to contract, the Sarcoplasmic Reticulum releases calcium. The
calcium binds to troponin, which causes the troponin & tropomyosin to uncover the
active site thus allowing contraction to occur.
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C. Neuromuscular Junction (NMJ)
1. Each muscle fiber (cell) is connected to the axon of a motor ________________.
2. The site where the nerve fiber and muscle fiber join is called the
___________________________ junction.
3. The Sarcolemma of the muscle is specialized at the NMJ and is called the
___________________________________.
4. When the signal to contract reaches the end of the axon, the neuron releases
_______________________________ (ACh) which is a neurotransmitter.
5. The ACh binds to receptors on the motor end plate and stimulates an electrical
reaction (__________________) to occur across the sarcolemma of the muscle fiber.
6. The depolarization causes the SR to release its ____________________ and thus
start the contraction.
7. After depolarization, the ACh is broken down by ______________________ (AChE).
8. A Motor Unit consists of the _______________________ and all the
_________________________ that it stimulates.
D. Contraction Physiology
1. Muscle response
a. ________________________ – A muscle fiber will contract fully or not at all.
b. ____________________ stimulus – the weakest signal (from the neuron) that will
cause contraction in the muscle fiber.
c. _____________________ – graphic recording of mechanical contractile activity.
2. Twitch – the response to a single threshold stimulus. Three phases
a. _________________ period (.01 sec.)
b. _________________ period (.05 sec.)
c. _________________ period (.05 sec.)
3. ____________________- sustained signals to contract, thus not giving the muscle
time to relax. Sustained muscle contractions eventually uses up all the _______ in
the muscle. The muscle therefore is unable to contract and its tension level drops to
zero (Muscle ____________________).
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4. Muscle _____________ – the constant contraction of __________ muscle fibers in a
muscle at all times. Muscle tone does not produce movement, but keeps muscles
______________ & healthy & helps maintain ______________________.
5. _____________________ contraction – contraction that shortens the length of the
muscle thus causing movement.
6. _____________________ contractions – contraction in which the muscle neither
shortens of lengthens.
E. Energy for Contraction
1. _____________ is the energy needed for muscle contraction. Your muscles have a
limited store of ATP.
2. As ATP is used up it is converted to __________.
ATP
ADP + P + Energy
3. The muscles also store ______________________________ (CP) that can bind with
ADP to produce more ATP.
ADP + CP
ATP + creatin
4. When the muscles work vigorously and burn energy, they begin to breakdown
___________________ to produce ATP.
5. The first step in the breakdown of glucose is called ___________________. This is
an anaerobic process that splits glucose into two pyruvic acids and produces
_______ ATP molecules.
Glucose
2 Pyruvic Acid + 2 ATP
6. Normally, pyruvic acid will then enter the _____________________ and go through
the ___________ Cycle, which is an _______________ method of breaking down
the pyruvic acid into _________ ATP.
7. As the muscle cell continues to burn energy, it begins to run out of
________________and the circulatory system cannot supply the _______________
to the muscle cells fast enough to continue aerobic respiration.
8. When your muscles run out of oxygen, they begin to break down pyruvic acid using
______________________ respiration called ____________________________
Fermentation.
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9. Lactic acid Fermentation breaks down pyruvic acid into ______ ATP and lactic acid
(which gives muscles that _______________ sensation after hard exercise.)
F. Oxygen Debt
1. Oxygen debt is the extra amount of _______________ that must be taken into the
body after vigorous exercise to restore the anaerobic processes (CP, & lactic acid).
2. Basically, ___________________ is needed to convert creatin back into CP& lactic
acid back into pyruvate.
3. For this reason, your body breaths heavily after working out in order to supply extra
oxygen to the cells until the oxygen debt is paid back.
G. Muscle Fatigue
1. Muscle Fatigue is the physiological ____________________ to contract.
2. Muscle fatigue is caused by:
a. lack of ____________
b. __________________ supply interruption (heart attack)
c. exhaustion of _____________
d. build up of ________________________________
H. Muscle Mechanics
1. Muscles are attached to bones in a lever system.
2. The lever is a rigid bar that moves on a fixed point or ___________________. The
resistance is called the ____________, and the work to move the load is called the
__________________.
3. There are three categories of levers
a. _______________ (____) Class Lever – the Fulcrum is located between the Load
and the Effort.
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b. ________________ (____) Class Lever -the Fulcrum is at one end and the Effort
at the other end of the lever with the Load in the middle.
c. _________________(____) Class Lever – the Effort is applied at a point between
the Fulcrum and the Load.
4. First class levers are at a mechanical advantage and are also called
______________ Levers. They provide the greatest amount of work per effort
applied. These levers are predominately found in ________________ and account
for their ability to lift many times their body weight.
5. Third class levers are at a mechanical disadvantage but are also called
________________ Levers. They allow the load to be moved rapidly though a large
distance. These levers are predominately found in _______________ and other
mammals.
G. Muscle Arrangements in the Body
1. Because muscles can ONLY “___________”, muscles are arranged in the body in
__________________ pairs. Therefore, whatever action one muscle group causes
you to “do”, the opposing group causes you to “undo”.
2. ___________________ – prime mover
3. ___________________ – muscle that is opposite the agonist and reverses a
particular movement.
4. ___________________ – assist the agonist in producing a desired movement.
III.
Disorders of the Muscular System
A. ___________________________________(_____) – group of inherited muscledestroying diseases that appear during childhood. The muscle fibers slowly degenerate
and atrophy (reduction in size and strength).
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1. ______________________ MD – most common type. Sex-linked. Carried by
female, but expressed in males. Appears in boys from 2-6 years of age. Die by early
20’s due to respiratory failure.
B. ________________________ – autoimmune disease where the immune system
destroys __________________________ thus preventing ACh from signaling muscle
contraction. A common symptom is droopy eyelids, although other effects include
weakness of arm, head, and chest muscles.
C. ___________________________ – viral disease that destroys ___________________.
The affected muscles atrophy. Sever cases cause death due to respiratory failure.
There is no cure for polio, however there is a vaccination. The virus is still in the
environment – so get kids immunized.
D. ____________________ – a bacterial toxin that prevents the release of ACh. Botulism
is usually linked to improper ___________________________ followed by failure to
adequately cook the food. In sever cases respiratory failure may cause death (10%).
E. ____________________ – bacterial infection that causes sustained contraction of some
muscles. Usually begin in the neck and jaw (______________________). Can be fatal
due to resp. failure.
F. ___________________ – sustained contraction of a muscle usually at night after
strenuous exercise. Due to a low blood sugar, dehydration, or low electrolyte levels.
G. ___________________ – pulled muscle.
H. ____ ____ ____ ____ -Rest, Ice, Compression, & Elevation. Standard treatment of
excessively pulled muscle, ligament or tendons.
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