Transcript Muscles - City College of San Francisco

Rheumatoid Arthritis is a condition
in which
1.
2.
3.
4.
5.
bones are unusually fragile and break easily.
the bone marrow does not develop properly.
there is an inflammation of the joints.
the epiphyses do not permit growth.
tendons are stretched.
Muscles
Bio 9
Spring 2009
Announcements
• Homework #1- Due today?
• Midterm 2: Avg- 70%
Outline
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Muscle tissue types
Skeletal muscle structure
Muscle function
Muscle control
Muscle power
Muscle disorders
Your muscular system allows
movement
• Mounted onto the
skeleton, skeletal
muscles move your
bones
• Other muscles beat
your heart and move
your food through the
digestive system
© 2001
2007 -Brooks/Cole
Thomson Higher..Education
©2005
©
Brooks/Cole
Thomson
Thomson
TRICEPS BRACHII
BICEPS BRACHII
PECTORALIS MAJOR
DELTOID
SERRATUS ANTERIOR
TRAPIZIUS
EXTERNAL OBLIQUE
LATISSIMUS
DORSI
RECTUS ABDOMINUS
GLUTEUS MAXIMUS
ADDUCTOR LONGUS
BICEPS FEMORIS
SARTORIUS
QUADRICEPS FEMORIS
GASTROCNEMIUS
TIBIALIS ANTERIOR
© 2007
- Thomson Higher
Education
© 2001
©2005
Brooks/Cole
Brooks/Cole
..Thomson
Thomson
Skeletal Muscles are attached with
tendons
• Tendons are connective
tissue attachments to
bone
• Origin of muscle is the
less movable
attachment
• Insertion is the more
movable attachment
flexor digitorum
superficialis
Fig. 6.20a, p.118
Some muscle groups work
antagonistically, others synergistically
• Since muscles can only
contract, they must
work in pairs to do
opposite movements
• Reciprocal innervation
ensures that
antagonistic muscle
pairs do not compete
triceps relaxes
origin
biceps contracts at
the same time, and
pulls forelimb up
triceps contracts,
pulls the forelimb
down
at the same time,
biceps relaxes
insertion
Fig.
Muscles do work through contraction
only
• No work is done when a
muscle relaxes
• Nor is energy spent
• Skeletal muscle is
voluntary; striated
• Muscle fiber= single
muscle cell
Cardiac muscle
• Involuntary muscle of
the heart
• Cells communicate with
each other closely to
allow simultaneous
contraction
• Irregular striations
Smooth muscle
• Involuntary muscle
• Forms contractile
linings of organs and
blood vessels
• Found in digestive
system, e. g. esophagus
Skeletal muscle
• Mounted on bones for
body movement
• Striated
• Mostly voluntary
(sometimes involuntary,
e. g. reflexes)
• Individual muscles
wrapped in connective
tissue sheath
Cardiac and smooth muscle
Smooth muscle is found in
1.
2.
3.
4.
5.
arms and legs.
the walls of hollow organs and tubes.
the heart.
the brain.
none of these.
Skeletal muscles are built on bundles
of bundles
• Individual cells of muscles
are called muscle fibers
• Bundles of Myofibrils
within cells help them
contract
• A fascicle is made of
several bound muscle
fibers
• Each contractile unit in a
myofibril is a sarcomere
Bundles are called fascicles
Fascicle design adds strength
Other things with fascicle design
The basic unit of contraction in a
muscle fiber is the sarcomere
• A single muscle fiber (cell)
consists of many myofibrils,
each containing hundreds of
sarcomeres along their
length
• Myofibrils are ringed by Ttubules and surrounded by
a net of sarcoplasmic
reticulum (SR), which hold
calcium ions (Ca++)
How Muscles Contract
• Muscle cells shorten when actin filaments
slide over myosin.
• Within each sarcomere there are two sets of
actin filaments, which are attached on
opposite sides of the sarcomere
• myosin filaments lie suspended between the
actin filaments.
Muscle contraction depends on actin
and myosin
• Myosin is a motor protein
• By binding ATP, myosin can
“pull” on an actin fiber
• Troponin and tropomyosin
control myosin’s ability to
bind to active sites on actin
• Troponin is moved in
presence of Calcium ions
How do actin and myosin
shorten muscles?
Skeletal, cardiac muscle striations are
bands of actin and myosin
The Sliding Filament model
How Muscles Contract
–
During contraction, the myosin filaments physically
slide along and pull the two sets of actin filaments
toward each other at the center of the sarcomere;
this is called the sliding-filament model of
contraction.
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When a myosin head is energized, it forms cross-bridges
with an adjacent actin filament and tilts in a power stroke
toward the sarcomere’s center.
Energy from ATP drives the power stroke as the heads pull
the actin filaments along.
After the power stroke the myosin heads detach and
prepare for another attachment (power stroke).
actin
myosin
actin
a Sarcomere when muscle cell is relaxed
Fig.
b Same sarcomere, contracted
actin
myosin
actin
p.116
myosin head
one of many myosin binding sites on actin
cross bridge
cross bridge
Fig. 6.9cd,
Fig. 6.9ef, p. 109
ATP
ATP
Fig. 6.9g, p. 109
When one muscle group is stimulated, no
nervous signals are sent to the opposing
group. This is due to
1.
2.
3.
4.
5.
reciprocal innervation.
lack of innervation.
hyperreflexia.
compensation.
depolarization.
Which of the following includes all
the others?
1.
2.
3.
4.
5.
Actin
Myofibril
myosin
myofilament
muscle cell
muscle’s outer sheath
(connective tissue)
two bundles of muscle
cells (each has its own
connective tissue sheath)
one muscle cell
one myofibril
Fig.
One myofibril
inside cell:
a. Skeletal muscle cell, longitudinal section. All
bands of its myofibrils are in register and give the
cell a striped appearance.
Fig.
sarcomere
Z band
b. Sarcomeres. Many
thick and thin filaments
overlap in an A band.
Only thick filaments
extend across the H
zone. Only thin filaments
extend across I bands
to the Z bands.
sarcomere
Z band
I band
H zone
A band
Z band
I band
Fig. 6.7b, p.108
How is the contraction of
sarcomeres controlled?
In other words, what controls your
muscle contractions?
The Neuromuscular Junction
• Where nerve cells tell
muscle cells to
contract
• Nerves control
voluntary and
involuntary muscles
• Neurons use a special
neurotransmitter for
muscles- acetylcholine
T-tubules and SR release calcium to
allow muscle contraction
• T-tubules and SR are
reservoirs of Calcium
ions(Ca++)
• Calcium channels line
the SR
• The neural
acetylcholine stimulus
opens calcium ion
channels in response
How do Calcium ions allow
muscle contraction?
Without Calcium,tropomyosin
blocks active sites on actin
Troponin controls the movement
of tropomyosin
troponin
Ca++ binds troponin,
moving it from active
a Actin molecule
sites on actin
myosin
binding site
blocked
b Cross-section of (a). Red dots
are calcium ions bound to
troponin (green).
c Calcium ions flow in; troponin
binds additional calcium.
myosin head
d Troponin changes shape,moving
away from the myosin binding site.
e The binding site is now exposed;
actin can bind the myosin head.
myosin head
Fig.
f Cross-bridge forms between
actin and myosin.
The sliding filament mechanism
1. supplies the energy needed for muscle
contraction.
2. provides a flexing action for the muscle fibers.
3. describes the action of the actin and myosin
in a muscle cell.
4. explains muscle fatigue.
5. only explains how muscles contract, not how
they relax.
The protein that directly blocks the myosin
binding site on the actin filament is
1.
2.
3.
4.
5.
troponin.
calsequestrin.
tropomyosin.
acetylcholine.
albumin.
Repeated signals from a neuron
cause muscle tetanus
• A single neural stimulus
may recruit only a few
muscle fibers
• When all muscle fibers
are recruited, the
muscle attains
maximum tetanic force
• Sustained tetanus
causes muscle fatiuge
Tetanus is also the term used for
the disease aka lockjaw
• Caused by Clostridium
tetani, an anaerobic
bacterium
• Deep puncture wounds
can allow penetration
of C. tetani into hypoxic
muscle tissue
• Tetanospasmin toxin
prevents inibitory
neuron responses
Recruitment of motor units
influences strength of response
• A motor unit is a group
of muscle cells all
activated by the same
neuron
• Neuron/muscle fiber
ratio varies with degree
of control required
• Motor units should be
greater in your hamstring
or your finger?
Slow twitch muscles have more
myoglobin
• Also called “red muscle”
(type I)
• Myoglobin stores oxygen
• Also more mitochondria
• Fast-twitch “white muscle”
(Type IIa, IIb, etc.)
responds more quickly and
powerfully, fatigues more
quickly
• Compare to chickens…
Contraction speeds vary with muscle type
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IR= internal rectus (eye muscles)
G= gastrocnemius
S= soleus
What can we infer about the composition of these muscles?
Muscular system disorders
Tearing of muscle fibers is a strain
• Also called a “muscle
pull”
• Swelling, bruising occur
from internal bleeding
Muscular dystrophies destroy
muscle fibers
• They are heritable
• Duchenne muscular
dystrophy- protein
dystrophin malfunctions
• Symptoms appear
infancy age 6
• Myotonic muscular
dystrophy- symptoms
appear in adulthood
• Which do you think is more
common?
The benefits of exercise
Strength and endurance training
benefit muscles in different ways
• Which type should
confer which benefit?
• More mitochondria
• More myofibrils/muscle
fiber
• Upregulation of
myoglobin
• Capilarization
• No exercise is isolated…
For maximum effect, one should
1. perform strength training only.
2. perform aerobic exercise only.
3. perform both aerobic exercises and strength
training.
4. perform much strength training and only a
little aerobic exercise.
5. perform much aerobic exercise and only a
little strength training.
During muscle contractions
1. the myofibrils shorten.
2. the actin and myosin filaments slide over
each other.
3. the actin filaments move toward the middle
of the sarcomere during contraction and
away on relaxation.
4. the muscle thickens.
5. all of these.
Muscle tissue
• Contractile tissue
• For movement of
body, blood,
organs
• Three major kinds
– Smooth
– Skeletal
– Cardiac
• All contain actin
and myosin fibers
for contraction
Synovial Joint Movements
Figure 5.14 (1 of 7)
Synovial Joint Movements
Figure 5.14 (2 of 7)
Synovial Joint Movements
Figure 5.14 (3 of 7)
Synovial Joint Movements
Figure 5.14 (4 of 7)
Synovial Joint Movements
Figure 5.14 (5 of 7)
Synovial Joint Movements
Figure 5.14 (6 of 7)
Synovial Joint Movements
Figure 5.14 (7 of 7)