Download Skeletal Muscles

The Muscular System and
Homeostasis
What are muscles?
• Muscles act like rope
pulling bones and
other muscles
together
• They convert chemical
energy into kinetic
energy (movement)
• There are 3 types of
muscle tissues in the
body
Types of Muscles
Skeletal Muscles
• Responsible for
voluntary
movement
•
Attached to
bones
Skeletal muscle
Actin
Myosin
Bundle of muscle fibers
Sarcomere
•Striated/Stripped
•600 in the body
Z disc
Myfibril
•Long
Muscle fiber
(cell)
Types of Muscles
Smooth Muscles
• Not voluntary control
• Found in hollow
structures: stomach,
intestines, veins
• Not striated
Types of Muscles
Cardiac Muscle
• voluntary
contractions
• Found only in
the heart
• Striated/Stripped
• Does not fatigue
easily
How do muscles
contract?
• Muscles contract when thin filaments in the muscle
fiber slide over the thick filaments
Relaxed Muscle
Myosin
Movement of Actin Filament
Actin
Z disc
Actin
Sarcomere
Binding sites
Myosin
Contracted Muscle
Cross-bridges
Z disc
Crossbridge
Where are calories
burned?
• The ATP provides the power to move the Myosin
• ATP to cell: gas to car
• ATP come from food you eat
• It combines with O2 to burn and give energy
Steps of muscle
contraction
• 1. Myosin head binds to actin.
• 2. ATP causes bend in myosin head
• 3 myosin contracts muscle
• Actin binding sites are blocked by tropomyosin when the
muscles is relaxed
• When calcium ion concentrations in the muscle fiber increase,
they form a troponin-tropomyosin complex that shifts away
from the binding sites on the actin allowing the muscle to
contract
• Calcium ions are regulated by the nerves that connect to the
sarcoplasmic reticulum surrounding the muscle fiber
• The calcium ions are removed by active transport when the
nerve impulse stops, relaxing the muscle
Creatine
Creatine phosphate
phosphate builds
builds up
up and
and
is
is stored
stored in
in resting
resting muscle
muscle (purple
(purple
box).
box). For
For the
the muscle
muscle to
to contract
contract
(green
(green area),
area), it
it needs
needs to
to acquire
acquire
ATP.
ATP. (A)
(A) When
When the
the muscle
muscle starts
starts
contracting,
contracting, it
it breaks
breaks down
down stored
stored
creatine
creatine phosphate.
phosphate. This
This generates
generates
some
some ATP
ATP that
that is
is used
used
immediately.
immediately. (B)
(B) To
To continue
continue
contracting,
contracting, the
the muscle
muscle carries
carries out
out
aerobic
aerobic cellular
cellular respiration
respiration as
as long
long
as
as oxygen
oxygen is
is available.
available. When
When the
the
oxygen
oxygen has
has been
been used
used up,
up, the
the
muscle
muscle can
can carry
carry out
out fermentation
fermentation
for
for aa limited
limited period
period of
of time.
time.
Fermentation
Fermentation results
results in
in only
only aa
small
small amount
amount of
of ATP
ATP compared
compared
with
with the
the amount
amount produced
produced by
by
aerobic
aerobic cellular
cellular respiration,
respiration, and
and
lactate
lactate builds
builds up.
up. Once
Once the
the muscle
muscle
resumes
resumes resting
resting (purple
(purple box),
box),
creatine
creatine phosphate
phosphate builds
builds up
up again.
again.
Muscle Energy
• ATP provides energy for the flexing of the myosin heads
• The ATP is produce in one of three ways
• 1) Creatine Phosphate Breakdown –the creatine gives up a
phosphate to DPTÆATP
• 2) Aerobic Respiration – glucose and oxygen are required in
the muscle for this to occur, the products are carbon dioxide
and heat
• 3) Fermentation – If oxygen is consumed faster then it can
be supplied aerobic respiration is replaced by fermentation
the product of which is lactic acid
Controlling Muscle
Contraction
• Nerve cells (motor neurons) control muscle contraction
Muscle fiber
neuron
Muscles, Health and
Homeostasis
Muscle & Bone
Interaction
• Muscles are attached to tendons.
• Tendons anchor to bone
• pull on the bone to allow for movements
Movement
Movement
Biceps (relaxed)
Triceps (relaxed)
Biceps (contracted)
Triceps (relaxed)
Complications and
Disorders
• Most are caused by sudden pressure and intense pressure
place onto the muscles and tendons.
• Many can be caused by a lack of use if the muscles (atrophy)
• Complete Though Lab 10.2
• These graphs show the force of
muscle contraction with time.
(A) A simple muscle twitch has
three periods: latent, contraction,
and relaxation. (B) When a
muscle is not allowed to relax
completely between stimuli, the
contraction gradually increases
in intensity until it reaches a
maximum, which is sustained
until the muscle fatigues.
• Skeletal muscles have different proportions of fasttwitch and slow-twitch fibres. Thus, the force and
response times of their contractions differ.
Importance of
Physical Activity