Download Ch 7 Muscular System Guided Notes

Anatomy & Physiology
Unit 4: Muscular System -Notes
Ch. 7: Muscular System
I. Introduction
 ________________________ is the most abundant tissue in the body
 It is always working:
 Movement
 Breathing
 Beating heart
 Locomotion
 Sitting/standing upright
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
Unit 4: Muscular System -Notes
B. ________________________
 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 [Ca2+]
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 ________________________________________.
Creating 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. Ca2+ 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 Ca2+ 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. Ca2+ released from sarcoplasmic reticulum into myofibrils
e. Ca2+ 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. Ca2+ actively transported back to sarcoplasmic reticulum
b. Troponin without Ca2+ 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 Ca2+ 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 O2)
1. Breakdown of glucose in absence of O2 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
O2 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/ O2)
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 O2 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
Usually 1 nucleus/cell
<actin & myosin
Irregular distribution of actin & myosin
No sarcomeres (striations)
Less distinct striations
Slower contraction
Intermediate rate of contractions
Autorhythmicity – periodic spontaneous
Autorhythmicity
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Anatomy & Physiology
Unit 4: Muscular System -Notes
contraction of smooth muscle (peristalsis)
Involuntary motor control
Involuntary motor control
Aerobic (no O2 debt)
Aerobic (limited anaerobic capacity)
Layers of smooth muscle tissue act together
as one unit to produce simultaneous
contractions
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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