Anatomy & Physiology
Ch. 7: Muscular System
Unit 4: Muscular System -Notes
I. Introduction

________________________ is the most abundant tissue in the body

It is always working:

Movement

Locomotion


Breathing
Sitting/standing upright

Beating heart
II. Muscular System Functions
A. Body ________________________

Via muscle ________________________; create overall body movements
B. ________________________ maintenance

Constant skeletal ________________________keeps us sitting or standing erect
C. ________________________

Thoracic muscles are responsible for the movements necessary for breathing.
D. ________________________production

Heat released as byproduct of skeletal muscles & is critical for maintenance of
________________________
E. ________________________

Speaking, writing, typing, gesturing, & facial expression
F. ___________________ & ________________ contraction

Move/mix food & water in GI tract, excrete secretions, regulate blood flow
G. ________________________

Cardiac muscle contraction; propels blood to body
III. Three Types of Muscle
A. ________________________ muscle
B. ________________________ muscle
C. ________________________ muscle
IV. Comparison of Muscle Types
A. Know these major differences on Table 7.2 (p. 171)
V. Characteristics of Skeletal Muscles

Approximately _______ % of body weight (with associated connective tissues)

Attached to ________________________
A. ________________________

Muscles can __________________ with force causing movement of structures to which they’re attached; lengthen passively (due to gravity or the force of an opposing muscle)
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Anatomy & Physiology
B. ________________________
Unit 4: Muscular System -Notes

Muscles respond to __________________ (usually nerves cause contraction of skeletal muscle)
C. ________________________

Skeletal muscle can be ________________________ to resting length and a little beyond
D. ________________________

Ability of muscles to ________________________ to original resting length after stretching
VI. Structure of Skeletal Muscle
A. Hierarchical organization:
1. Each muscle (organ) surrounded by ________________________ (upon + muscle)
/ fascia (fillet)
– connective tissue a. ________________________ (bundle) – bundles of muscle cells/fibers; surrounded by ________________________ (around + muscle)
– loose connective tissue i. Several ________________________ per fasciculus; surrounded by
________________________ (within + muscle) – loose connective tissue
VII. Structure of Skeletal Muscle Cells (muscle __________ = muscle ____________________ )
A. Microscopic structure
1. Each fiber composed of ____________________ – fine, longitudinal fibril within skeletal muscle fiber. Each muscle fiber has many myofibrils.
a. Myofibrils composed of ____________________ (protein filaments) arranged in
____________________ (flesh + part) i. ____________________ myofilaments (thin) ii. ____________________ myofilaments (thick)
2. Each muscle fiber has: a. ____________________ (muscle cell membrane) b. ____________________ (cytoplasm) (flesh + formed) c. ____________________ _____________________(ER)
– increased [Ca 2+ ] produces muscle contractions d. ____________________ ____________________ (T tubules) – network of tubes connecting sarcolemma to sarcoplasmic reticulum
Structure of Skeletal Muscle Cells
B. Banding Pattern (striations) (See 7.3 a)
1. ____________________ (I-LIGHT): thin myofilaments only (actin); from Z-disk to myosin
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Anatomy & Physiology Unit 4: Muscular System -Notes
2. ____________________ (A-DARK): thick & thin myofilaments (myosin & actin); dark, central region of sarcomere; length of myosin myofilaments
3. ____________________ : dark line in middle of I-band; site of actin attachment; make of protein fibers
4. ____________________ : lighter, central region in middle of A-band; thick myofilaments only (myosin)
5. ____________________ : dark line in middle of H-zone; site of myosin attachment
6. ____________________ : smallest functional contractile unit of muscle cell; runs from Z-disk to Z-disk; highly ordered units
VIII. Membrane Potentials
1. ____________________ of most cell membranes is positively charged relative to
____________________
2. A ________________________________________ is created = charge difference across the membrane of a resting cell
3. Occurs because: a. Higher [K + ] ____________________ inside than outside b. Cell membrane more ____________________ to K + than other ions (K + channels open)
4. ________________________________________ = change in membrane potential in an excitable tissue that is propagated as an electrical signal a. Made via ________________________________________ .
C reating an action potential…
1. ____________________ membrane potential.
Na + channels & some K + channels closed. A few K + diffuse down c.g. through open K + channels, making outside positive.
2. ____________________ . Na + channels open. A few Na + diffuse down c.g. through open Na+ channels, making ____________________ positive.
3. ____________________ .
Na + channels closed; Na + movement into cell stops. K + channels open. K + movement outside cell increases, making
____________________ positive.
Nerve supply
IX. Neuromuscular Communication

Muscle fibers contract when stimulated by motor neurons
A. ______________________________ - nerve cells that innervate all muscle tissue
1. pass along action potentials as ____________________ ____________________
2. axons form junctions with many muscle fibers called ____________________
____________________ (NMJ’s) or synapses)
B. The “ ____________________ ” = 1 motor neuron + all muscle fibers it stimulates
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Anatomy & Physiology Unit 4: Muscular System -Notes
1. From 2-3 fibers/unit (fine control) to 2000 fibers/unit (large power movements)
2. several motor units = 1 ____________________
C. Neuromuscular junction structures :

Occur near ____________________ of muscle fiber

Tips of axons are enlarged (sticky) and rest in little pits on muscle fiber
1. ____________________ terminals
– bulbous ends of motor neuron (ends of axons)
2. NMJ or ____________________ – region of chemical communication between cells a. ____________________ ____________________ contain neurotransmitter
( ____________________ ) i. Neuron releases ACh to stimulate or inhibit a postsynaptic cell (muscle fiber) b. ________________________________________ – space between presynaptic terminals and postsynaptic ____________________ (sarcolemma of muscle fiber)
D. Basic events of ________________________________________ :

Role of ACh in muscle contraction

ACh inhibitors or stimulators (or molecules that affect acetylcholinesterase) affect muscle contractions – some poisons and insecticides do this (don’t allow muscles to contract/relax)
1. ____________________ ____________________ (nerve impulse) arrives at presynaptic terminals
2. Synaptic vesicles release ____________________ (ACh) into synaptic cleft via
____________________
3. ACh binds to receptors sites on Na + channels in ____________________ membrane, causing them to open
4. Na + moves into cell causing an ___________________________ which travels along sarcolemma & T-tubules
5. ACh triggers ____________________ release from sarcoplasmic reticulum
6. Ca 2+ inside muscle triggers ____________________ & ____________________
“sliding filament” action
7. ____________________ is spent
8. ____________________ degrades remaining ACh to limit contraction stimulus
E. ________________________________________

Mechanism by which actin and myosin myofilaments ____________________ over one another during muscle contraction
1. Actin & myosin myofilaments slide past one another causing
____________________ to shorten a. Sarcomere shortening (end to end) causes ____________________ shortening
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Anatomy & Physiology Unit 4: Muscular System -Notes i. Myofibril shortening causes ________________________________________ ii. Sarcomeres lengthen during ____________________ (due to opposing force of another muscle or gravity)
2. ____________________ and ____________________ shorten; A-bands maintain constant width (Fig 7.7)
3. ____________________ binds to troponin
4. Tropomysin molecules slide into groove
5. Myosin attaches to exposed sites on ____________________ myofilament
6. Energy from ____________________ stored in myosin heads
7. Myosin heads bind to actin forming ________________________________
8. Stored energy used to myosin heads causing actin myofilament to slide
9. ATP binds to myosin causing head to ________________ &
________________________ to resting position
10. Cycle repeats if Ca 2+ still bound to troponin & ____________________ still available
 ____________________ ______ – (stiffness + death) – no more ATP, therefore myosin heads remain attached and crossbridges are left intact, causing stiff muscles

ATP breakdown also releases ____________________ , therefore, increase in body temperature when exercising and shivering (homeostatic mechanism)
X. Muscle Twitch, Summation, Tetanus, & Recruitment (see 7.9)
A. ______________________________ - contraction of a muscle fiber in response to a stimulus; three phases:
1. ____________________ phase – time between stimulus application and beginning of contraction a. Action potential produced by at least 1 motor neuron and sent to a NMJ b. ACh is released and binds to receptors on Na + channels – creates another action potential c. Action potential travels along ____________________ &
____________________ membranes d. Ca 2+ released from sarcoplasmic reticulum into myofibrils e. Ca 2+ binds to troponin, causing tropomysin to expose myosin to actin’s attachment sites f. Crossbridges form
2. ____________________ phase – time of contraction a. Crossbridge movement and cycling b. Increased tension in muscle fibers
3. ____________________ phase – time of relaxation a. Ca 2+ actively transported back to sarcoplasmic reticulum b. Troponin without Ca 2+ causes tropomysin to slide back into groove, blocking attachment sites
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Anatomy & Physiology Unit 4: Muscular System -Notes
B. Strength of Muscle Contraction (increased by:) (See Fig. 7.10)
1. ____________________ – increasing force of contraction of muscle fibers in muscle
2. ____________________ – increasing number of muscle fibers contracting within muscle
3. ____________________ (convulsive tension)
– sustained muscular contraction caused by a series of nerve stimuli repeated so rapidly that there is no
____________________ , instead a sustain contraction results a. Caused by Ca 2+ buildup in myofibrils due to rapid action potential production (faster than transport back to sarcoplasmic reticulum)
XI. Energy Requirements for Muscle Contraction
A. ____________________ produce ATP
1. Multiple mitochondria in sarcoplasm produce ATP needed for muscular contractions
(lie between ____________________ ) a. Must constantly produce ATP (just for cell maintenance) b. ____________________ be stored (in sufficient amounts)
B. Creatine phosphate is energy storage
1. Used to generate ATP; high energy molecule (see 7.11)
C. ____________________ respiration (w/o O
2
)
1. Breakdown of glucose in absence of O
2
to produce ____________________ and
____________________ a. Glycolysis

pyruvic acid

lactic acid) b. Occurs in cytoplasm
2. Generates _______ ATP; short-lived, but faster than aerobic
– this is important when
O
2
is limited.
3. ____________________ as waste product (irritant to muscle fibers)
4. Sprinting: first uses ____________________ respiration, uses up creatine phosphate, then switches to ____________________ respiration
D. ____________________ respiration (w/ O
2
)
1. Breakdown of glucose in the presence of O2 to produce CO2, H2O, & ~38 ATP a. Glycolysis

Krebs

ETC b. Occurs in ____________________
2. Generates up to ________ ATP; long-term a. More efficient (up to 18x more ATP than anaerobic respiration)
3. Uses other nutrient molecules (F.A., a.a.) a. ____________________________ – must be repaid after labor i. Amount of oxygen needed in chemical reactions to:

Convert lactic acid to ____________________

Replenish ATP and creatine phosphate in muscle fibers
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Anatomy & Physiology Unit 4: Muscular System -Notes

Replenish O
2
stores in lungs, blood, and muscles ii. Explains high heart rate & breathing rate for extended period of time after exercise
4. Long-distance/endurance uses ____________________ respiration (fatty acids important)
XII. Fatigue
A. ____________________ fatigue – CNS causes the perception that continued muscle contraction is impossible
1. can be overcome – last sprint at end of race
B. ____________________ fatigue
– force of muscle contractions become increasingly weak when ATP is used faster than can be produced and lactic acid builds up faster than it can be removed
1. ____________________ contracture – muscles cannot contract or relax (not enough ATP to bind to myosin for crossbridging or to release the myosin heads) a. Occurs with extreme muscle fatigue
XIII. Types of Muscle Contractions
A. ____________________ contractions (equal distance)
– muscle contraction in which the length of the muscle does not change, but the amount of tension increases
B. ____________________ contractions (equal tension) – muscle contraction in which the amount of tension is constant and the muscle shortens
1. Movement of arms and fingers
2. Most muscle contractions are a combination of isometric & isotonic
3. ____________________ – isotonic contraction in which muscle tension increases while muscle shortens
4. ____________________ – isotonic contraction in which muscle tension is maintained (constant) while muscle lengthens a. Ex. – letting a weight down slowly
 ____________________ – constant tone produced by muscles over long periods of time

Ex – back & leg muscles tight; heat up right; abdomen in
XIV. Smooth & Cardiac Muscle
Smooth Muscle Cardiac Muscle
Small, spindle-shaped Long, striated, branching
1 nucleus/cell
<actin & myosin
Usually 1 nucleus/cell
Irregular distribution of actin & myosin
No sarcomeres (striations)
Slower contraction
Autorhythmicity
– periodic spontaneous
Less distinct striations
Intermediate rate of contractions
Autorhythmicity
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Anatomy & Physiology contraction of smooth muscle (peristalsis)
Unit 4: Muscular System -Notes
Involuntary motor control Involuntary motor control
Aerobic (no O
2
debt)
Layers of smooth muscle tissue act together as one unit to produce simultaneous contractions
Aerobic (limited anaerobic capacity)
Intercalated disks – communication between cells
XV. Disorders & Other Conditions of Muscle Tissue
A. ____________________ – painful, spastic contractions of muscle
1. Caused by muscle irritation a. Lactic acid buildup or inflammation of connective tissue
B. Hypertrophy and Atrophy
1. ____________________ – enlargement of muscle from an increase in number of myofibrils within muscle fibers a. From exercise b. Greater in males (more testosterone)
2. ____________________ – decrease in muscle size from a decrease in myofilaments within muscle fibers a. Severe atrophy = permanent loss of skeletal muscle and subsequent replacement with connective tissue i. Can be caused by long-term immobility or nervous system damage
C. ____________________ ____________________ (bad + nourishment)
– group of inherited muscle disorders in which the skeletal muscle degenerates accompanied by progressive weakness in the person. Progressive degeneration of muscle fibers with atrophy and eventual tissue replacement with fat or other connective tissue.
1. ____________________ muscular dystrophy – slow motor development, progressive weakness & muscle wasting beginning in the pelvic girdle. First identified in children ~3 years of age. Leads to replacement of muscle tissue with connective tissue, muscular atrophy, and skeletal deformity.
2. ____________________ muscular dystrophy – failure of muscles to relax after a forceful contraction and muscular weakness. Dominant trait in both sexes. 1 in
20,000 births. Slow progression first affecting face and neck muscles, then the hands.
D. ____________________ ____________________ (muscle + weakness) – muscular weakness that is not accompanied by atrophy. Chronic, progressive disease caused by destruction of acetylcholine receptors in NMJ. Neuronal stimulation is hindered, thus, weaker muscles.
E. ____________________ – inflammation of the tendon or its attachment point. Usually from overtraining in athletes.
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