MUSCLES
I. GENERAL INFORMATION
HOW MUSCLES ARE NAMED
LOCATION
• Ex: TEMPORALIS
NUMBER OF ORIGINS
• Ex: BICEPS BRACHII & TRICEPS BRACHII
SIZE
• Ex: GLUTEUS MAXIMUS & ADDUCTOR MAGNUS
LOCATION OF ORIGIN & INSERTION
Ex: STERNOCLEIDOMASTOID
DIRECTION OF FIBERS
Ex: EXTERNAL & INTERNAL OBLIQUE
SHAPE OF MUSCLE
Ex: DELTOID & TRAPEZIUS
ACTION OF THE MUSCLE
Ex: LEVATOR SCAPULAE
TERMS
ACTION: WHAT A MUSCLE DOES
ORIGIN: THE END OF THE MUSCLE ATTACHED
TO THE BONE THAT DOES NOT MOVE
INSERTION: THE END OF THE MUSCLE
ATTACHED TO THE BONE THAT DOES MOVE
ANTAGONISTS: MUSCLES WITH OPPOSING
EFFECTS E.g.. BICEPS & TRICEPS
SYNERGISTS: MUSCLES WITH THE SAME
ACTION
TYPES OF MUSCLE TISSUE
• SKELETAL
• CARDIAC
• SMOOTH
SKELETAL MUSCLE
• ATTACHED TO BONES
• HAS STRIATIONS (stripes)
• VOLUNTARY
• CONTRACTS RAPIDLY
CARDIAC MUSCLE
• ONLY IN THE HEART
STRIATIONS
INVOLUNTARY
SMOOTH MUSCLE
• WALLS OF HOLLOW ORGANS
• NO STRIATIONS
• INVOLUNTARY
II. Muscle Tissue In Detail
• OVERVIEW:
• (you need about nine lines…..)
Myosin
Actin
Troponin
Tropomyosin
II. Muscle Tissue In Detail
• Skeletal Muscle
Outside covering = Fascia (at
muscle end may form into tendon
to attach to the bone or it may
form into flat sheets to connect to
other muscles. These sheets are
called aponeuroses.)
• Next layer = epimysium (CT –
connective tissue)
– Wrapping fasicle (fascicle is a
bundle of cells) = perimysium (CT)
– Wrapping each muscle fiber (cell) in
the fasicle = endomysium (CT)
(muscle fiber = muscle cell)
III. MUSCLE TISSUE
• Contributes to homeostasis by
producing heat to maintain normal
body temperature, storing and moving
substances throughout the body and
producing movement.
Functions
•
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1. Body movement
2. Stabilizing body position
3. Store substances like Ca2+, ATP,
4. Move substances (ex. Food)
5. Heat production – by muscle
contractions called thermogenesis
• (skip to contraction)
Properties
• 1. Electric Excitability - muscle cells
(and nerve cells) have the ability to
respond to certain stimuli by producing
electrical signals. Signals are called
action potential.
• 2. Contractility - the ability of muscle to
contract
• 3. Extensibility - the ability to stretch
4. Elasticity - ability to return to the
original shape
Anatomy of a Muscle Fiber (cell)
• 10 cm to 30 cm (4 in to 12 in)
• 1. Has 100 + nuclei
• 2. Has numerous mitochondria
• 3. The number of skeletal muscle fibers is
set at birth (they enlarge)
•
4. Sarcolemma - (flesh sheath) plasma
membrane
•
5. Sarcoplasm - cytoplasm
•
6. Sarcoplasmic reticulum - encircles
myofibrils it stores Ca2+
Anatomy of Muscle Con’t
• 7. Myoglobin - red protein only in muscles
- binds O2 and releases it when the
mitochondria needs it for ATP production
• 8. Myofibrils- are within the fibers (cells) in
the sarcoplasm. They are protein
filaments that are the contractile elements/
parts of the muscle. They are striated and
run the length of the muscle fiber.
Anatomy of Muscle Con’t
• 9. Myofilaments - bundles in myofibrils protein filaments made up of primarily
actin (protein) and myosin (protein)
– a. Thick Filaments - made up of myosin
(motor protein for pushing and pulling)
•
b. Thin Filaments - made up of actin
primarily. Also, troponin and tropormysin,
which are proteins.
• c. These filaments are arranged in
compartments called sarcomeres (mere =
parts)
Anatomy of Muscle Con’t
10. sarcomere - a contractile unit
composed of thick and thin filaments
Anatomy of a Sarcomere
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1.
Zone of Overlap = Thick and Thin
2.
A Band = mostly thick filaments
3.
I Band = mostly thin filaments
4.
M Line= Thickened because more
myosin
5.
Z Disk = Anchoring site for thin
filaments
6. H Zone – only Thick filaments (myosin)
P. 288
Muscle Contraction (Sliding
filament mechanism)
Page 295 Table 9.1 Quiz tomorrow!!!!!
Contraction
1. A nerve impulse travels down a motor neuron axon
2. The motor neuron terminal releases the neurotransmitter acetylcholine (Ach)
3. ACh binds to Ach receptors
4. The carcolemma is stimulated, and a muscle impulse travels over the surface of the muscle fiber and
deep into the fiber through the transverse tubules.
5. The muscle impulse reaches the sarcoplasmic reticulum, and calcium channels open.
6. Calcium ions diffuse from the sacroplasmic reticulum into the sarcoplasm and bind to troponin
molecules
7. Tropomyosin molecules move and expose specific sites on actin
8. Actin and myosin form linkages
9. Thin (actin) filaments are pulled toward the center of the sarcomere by myosin cross-bridges.
10. The muscle fiber shortens and contracts.
Muscle fiber Relaxation
1. Acetylcholinesterase decomposes acetylcholine, and the
muscle fiber membrane is no longer stimulated.
2. Calcium ions are actively transported into the
sarcoplasmic reticulum.
3. ATP breaks linkages between actin and myosin filaments
without breakdown of the ATP itself.
4. Breakdown of ATP “cocks” the cross-bridges.
5. Troponin and tropomyosin molecules inhibit the
interaction between myosin and actin filaments.
6. Muscle fiber remains relaxed, yet ready until stimulated
again.
• So What is really happening? This is called
the sliding filament mechanism (Theory):
– Remember the sarcomere is the “functional”
unit of muscle contractions
– (draw sarcomere)
Review: The sarcomere shortens not the
filaments!
Two additional items:
1. ATPase – catalyzes the breakdown of
ATP to ADP and P
2. Acetylcholinesterase – catalyzes the
breakdown of ACh in the synapsis so no more
Ca2+ is released from the SR.
• http://www.getbodysmart.com/ap/muscle
tissue/contraction/contractioncycle/tutori
al.html
• Shows contraction