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Slide 1
The Muscular System Note: Prefixes myo, mys, and sarco refer to
muscle
Slide 2
Naming Skeletal Muscles Direction of muscle fibers Rectus: The
muscles fascicles are parallel to the long axis of the body or
limb. Transverse: The muscles fascicles are perpendicular to the
long axis of the body or limb. Oblique: The muscles fascicles are
aligned at an angle to the long axis of the body or limb. Location
Location of a muscle Size Maximus: Large muscle Minimus: Small
muscle Longus: Long muscle Brevis: Short muscle Number of origins:
the end of the muscle that does not move. Biceps: Two origins
Triceps: Three origins Quadriceps: Four origins Shape (ie. Deltoid
is triangular) Origin (proximal less movable end) & insertion
(Insertion: the end of the muscle that moves) Action (What a muscle
does when it contracts)
Slide 3
Shapes of skeletal muscles: Parallel or fusiform: fibers run
parallel to each other contract over a great distance good
endurance but are not very strong. Examples: Sartorius muscle and
rectus abdominus muscle. Convergent: muscle fibers converge on the
insertion to maximize the force of muscle contraction Examples:
Deltoid muscle and Pectoralis Major muscle. Pennate: many fibers
per unit area. strong but they tire quickly. There are three types
of pennate muscle. unipennate bipennate multipennete Circular:
Muscle fibers surround an opening to act as a sphincter. Examples:
Orbicularis oris and Orbicularis oculi muscles.
Slide 4
Do Now: Grab your Clicker! Review your charts and diagrams for
names and locations of skeletal muscles
Id the sartorius muscle 1. 1 2. 2 3. 3 4. 4 5. 5 6. 6 7. 7
Slide 25
Id the vastus lateralis 1. 1 2. 2 3. 3 4. 4 5. 5 6. 6 7. 7
Slide 26
Id the rectus femoris 1. 1 2. 2 3. 3 4. 4 5. 5 6. 6 7. 7
Slide 27
Why do you think that muscle- enhancing supplements (steroids,
creatine) are so popular at all levels of fitness and athletics
(high school, college, pro, etc.) and do you see any problems with
this?
Slide 28
Muscle Tissues Cardiac Involuntary striated muscle Dinucleated
Communicate via intercalated disks Natural contraction cycle
determined by pacemaker cells Smooth Lines blood vessels, digestive
organs, urinary system, and parts of respiratory system Involuntary
nonstriated muscle Ca+ triggers contractions differently (lacks
sarcomeres) Skeletal Voluntary striated muscle Multinucleated cells
called muscle fibers Controlled by motor nerve cells 40% of your
body mass!
Slide 29
Functions of Skeletal Muscle Excitable Receive and respond to
stimulus Contractible Produce Movement Pull on tendons and move
bones Maintain posture and body position Continuous contractions
maintain posture Stabilize & strengthen joints Support/protect
soft tissues Abdominal wall Floor of pelvic cavity Guard entrances
and exits Voluntary control of swallowing, defecation, and
urination Maintain body temp Some energy from contractions lost as
heat Extensibility Can stretch beyond its resting length Elasticity
Recoils to resume resting length
Slide 30
Muscle Attachments Most muscles attach to bones in 2 places
Insertion- movable bone Origin immovable/less movable bone Direct
Attachments Epimysium of muscle fused to periosteum of bone
Indirect Attachments (more common) Tendons connect skeletal muscle
to periosteum of bones Aponeurosis layers of tendons that form a
sheet
Slide 31
Organization of Skeletal Muscle: Gross Anatomy Each elongated
cell is called a muscle fiber Contains several tissues Connective
Tissue Sheaths Epimysium dense irregular connective tissue
surrounding entire muscle Perimysium divide skeletal muscles into
bundles of fibers (fascicles) Endomysium areolar tissue that
surrounds ea/fiber Blood vessels 1 artery & 1 + veins Numerous
cross-linked capillaries Nerves Typically 1 nerve ending per muscle
fiber Skeletal muscle See next page for details.
Slide 32
Connective tissue coverings of a skeletal muscle listed from
superficial to deep are 1. Endomysium, perimysium, epimysium 2.
Endomysium, epimysium, perimysium, 3. Epimysium, Endomysium,
perimysium, 4. Epimysium, perimysium, Endomysium,
Slide 33
Microanatomy of Skeletal Muscle Sarcolemma plasma membrane T
tubules transverse invaginations Sarcoplasm cytoplasm Increased
myoglobin Increased gylcosomes Myofibrils bundles of myofilaments
parallel to cell Thin filaments actin proteins Thick filaments
myosin proteins Used for contraction Sarcoplasmic reticulum smooth
ER (stores Ca+) Sarcomeres repeating units of myofilaments
Slide 34
Sarcomere: functional contractile unit of a muscle fiber
Sarcomere- 2m region of myofibril between two Z-discs (Z-lines)
Striations - repeating units of dark A bands and light I bands H
zone light stripe in the middle of the A band, with dark vertical M
line Z disc or Z line in the I band All banding patterns are due to
myofilaments: Actin thin filament (blue) Myosin thick filament
(tan)
Slide 35
Actin (thin filaments) & Myosin (thick) Myosin globular
heads that face outwards to cross-bridge (link) to actin, and
contain ATPase Myosin tails form central part of molecule Cross
bridges act as motors to generate tension Regulatory proteins
Tropomyosin spirals around actin to block myosin binding sites in
relaxed muscle Troponin inhibitory helps position tropomyosin on
actin and binds to Calcium ions
Slide 36
Sarcoplasmic Reticulum & T Tubules Sarcoplasmic Reticulum
(SR) elaborate smooth ER like a sleeve along myofibril w/
perpendicular cross channels called terminal cisternae T Tubules
protrude deep into cell encircling each sarcomere
Slide 37
Sliding Filament Model of Contraction
Slide 38
Sliding Filament Theory 1. ACh (Acetylcholine) neurotransmitter
that released at neuromuscular junction (1 per muscle fiber) 2. SR
& T-tubules release Ca +2 into sarcoplasm 3. Ca +2 binds to
troponin, removing blocking action of tropomyosin 4. Myosin heads
attach to actin (cross bridge is formed) 5. Power Stroke: myosin
pulling actin towards midline of sarcomere powered by hydrolysis of
ATP ADP + P i 6. Acetylcholinesterase enzyme that breaks down Ach
to prevent continued contraction 7. Ca +2 recaptured by SR,
tropomysoin blocks binding site 8. Myosin heads release actin
relaxing sarcoemre
Slide 39
The command to contract is distributed deep into the muscle
fiber by 1. Sarcolemma 2. Sarcomere 3. Transverse tubules 4.
myofibrils
Slide 40
Homework: Compare Pallor mortis, Algor mortis,, Rigor mortis,
Liver mortis, and putrification Describe how this relates to the
muscular system Cite your source (informal URL is fine) -OR- Draw a
diagram depicting stages of muscle contraction and relaxation
labeling structural components
Slide 41
Do Now: What is Rigor Mortis? Stiffness of Death Begins 3-4
hours after death, peaks at 12 hours postmortem and slowly
dissipates over the next 48-60 hours Calcium influx into muscle
cells promotes cross-bridge formation ATP is no longer produced,
therefore detachment is impossible Creates a state of muscular
contraction until the breakdown of muscle tissue by enzymes
(endogenous or bacterial) during decomposition. The myosin heads
are eaten off by the enzymes, allowing the muscle contraction to
release and the body to relax.
Slide 42
Energetics of Muscle Activity Active Skeletal Muscle fiber
requires 600 trillion ATP/sec! Stored ATP- lasts 4-6 seconds
Quickly regenerated by: Creatine Phosphate (CP) ADP + Creatine-P
ATP + creatine Lasts 15 sec (replenishes during inactivity) Aerobic
Metabolism ( Glycolysis Krebs Oxidative Phosphorylation) Provides
30% of ATP needed during peak exertion, 95% of ATP during prolonged
exertion Glycogen, blood glucose, after 30 mins fatty acids High
yield ATP (38 ATP), but slow Anaerobic Metabolism (glycolysis) Main
E source Lactic acid builds up (gone 30 mins after exercise stops)
Faster but ineffective only 2ATP Muscle Fatigue physiological
inability to contract despite stimulation lactic acid build up
Ioinc imbalances Recovery Period returns to pre-exertion
levels
Slide 43
Please make your selection... 1. Choice One 2. Choice Two
Slide 44
Aerobic Respiration
Slide 45
EPOC: Excess Postexcercise Oxygen Consumption Oxygen debt extra
O 2 needed by body to restore all nonaerobic sources of ATP
Replenish O 2 reserves in myoglobin Liver must convert lactic acid
to pyruvic acid Glycogen stores must be replaced ATP and creatine-P
reserves must be resynthesized Only 25-40% of energy released is
used for work, remainder is released as heat
Slide 46
Muscle Mechanics Motor unit - # muscle fibers controlled by
singe motor neuron Fine control of movement determined by size of
motor unit Ex. Eye vs. Leg muscles During sustained contraction
motor units activated on a rotating basis (some rest/some contract)
Muscle tone -slightly contracted relaxed muscles to maintain
posture and stabilize joints Muscle twitch response of motor unit
to a single motor neuron (in lab) Each twitch has 3 phases: Latent
period (2msec) action pot. & release of Ca +2 Contraction phase
(peak) (10-100 msec) cross bridges active Relaxation phase (10-100
msec) reuptake of Ca +2 sarcomere returns to original length
Slide 47
Types of Contractions Isotonic Contractions Concentric muscle
shortens and does work Eccentric muscle generates force as it
lengthens Isometric Contractions Tension builds but muscle neither
shortens or lengthens Maintains posture
Slide 48
Muscle Tone Tone resting tension (slightly contracted) Spinal
reflexes alternate contractions of motor units Stabilizes the
position of your joints and maintains posture Any skeletal muscle
not stimulated on a regular basis will atrophy fibers become
smaller and weaker Decreases 5% per day of inactivity! Initially
atrophy is reversible Extreme atrophy is permanent Paralyzed muscle
may be reduced by 25% of its initial size
Slide 49
Muscle Performance Force and endurance depends on: Types of
muscle fibers (most muscles contain a mixture of both but genetic
variation) Fast Twitch (white) Powerful rapid contractions Glycogen
used quickly Fatigue rapidly (few mitochondria) Anaerobic, few
mitochondria Little myoglobin Lactic acid builds up quickly Slow
Twitch (red) Slow contraction Aerobic, high endurance Many
mitochondria Extensive capillary supply Myoglobin - binds O 2
reserves in muscle cell
Slide 50
Exercise Anaerobic (Resistance) Frequent, brief intense
workouts Weightlifting, isometric exercise Results in Hypertrophy
of muscle fibers More mitochondria More myofilaments and myofibrils
Store more glycogen Aerobic (Endurance) Sustained low levels of
activity Walking, swimming, biking, jogging Results in: Increases #
capillaries Increases # mitochondria Increases myoglobin synthesis
Carb-load the day before; drink glucose rich sports drinks
Slide 51
An activity that would require anaerobic endurance is 1.
50-meter dash 2. Pole vault 3. Weight lifting competition 4. All of
the above