Download Muscle Phys. & Histology

BIOL 2010 Human Anatomy & Physiology I
What are the functions of muscles?
Muscle are the machines converting
____________ energy to
____________energy!
BI 201 Human Anatomy & Physiology
What are the types of muscle tissue?
* Smooth
* Cardiac
* Skeletal
What are the attributes of muscles tissue?
All muscle tissue has 4 common
characteristics:
____________ Respond to stimuli with electric current
____________ Ability to shorten when stimulated
____________ Can be stretched up to 3 times contracted length
____________ Recoils to resting length after tension released
What are muscles made of?
Muscles are comprised of
different components:
1) ___________________
These are connective tissue in a
hierarchical structure that attach
individual muscle cells to each
other, to other bundles
(__________), to tendons to
periostea and bone itself
These are _____ excitable and
NOT _______________
Will force of contraction be
totally exerted on target part?
What are muscles made of?
2) _________________
Vessels necessary for
transporting blood to
and from muscle
tissue travel through
the connective tissue.
Nerves necessary for
________________
__________to initiate
muscle contraction
also travel through the
connective tissue
What are muscles made of?
3) Contractile components
Muscles (whole) are
comprised of…
Fasciculi, which are…
Many individual muscle
cells (muscle fibers)…
Each with a cell
membrane
(____________),
cytoplasm
(______________),
organelles and
___________…made of _____________
What are myofilaments and how are they
different?
Structure of the
2 myofilaments:
Thin (Actin)
3 parts…
Thick (Myosin)
A.D.A.M. sliding filament theory #3-16)
What are muscles made of?
What are muscles made of?
Another View…
Now how do we convert an action potential
(electric signal) into a contraction?
Ca2+ ions
bind with
__________
which causes
___________t
o “slide off”
the active sites
on the actin
Exposed active sites are bound to heads
of myosin forming a ______________
Now how do we convert an action potential
(electric signal) into a contraction?
When cross-bridges
form, then energy
stored in myosin
heads is released as
mechanical motion
of heads “snapping
back” pulling thin
filaments towards
each other
(____________).
Now how do we convert an action potential
(electric signal) into a contraction?
ATP is used to
release cross-bridge
ATP is then
converted to ADP to
“re-cock” the
myosin head
(____________)
How does an action potential in a motor
neuron result in an “action” in the muscle
fiber?
Where the motor neuron and the
muscle fiber interact is called the
________________________
How does excitation-contraction coupling occur?
1)
1
2) Ca2+ triggers release of
neurotransmitters from
synaptic vesicles.
3) Acetylcholine diffuses
across cleft & binds with
receptor on Na+ channels.
4)
2
3
4
How do you stop this thing?
____________________ is an
enzyme that breaks down
Acetylcholine into acetic acid
and choline.
_________ is pumped back
into presyntapic terminal.
_______________… What
results?
Curare (plant extract)
Now how do we convert an action potential
into a contraction?
(Excitation-contraction
coupling)
Muscle fibers are covered
with invagination called
____________________
(T tubules), which
functionally bring the
plasma membrane
(sarcolemma) and
extracellular fluid into the
interior of the cell.
Now how do we convert an action potential
into a contraction?
On either side of the T
tubules is an enlarged
area of the
___________________
(smooth endoplasmic
reticulum) called
cisternae.
A T tubule and the
__________ on either
side make up a triad.
Now how do we convert an action potential
into a contraction?
Ca2+ ions are
pumped into the
lumen (cavity),
up to 2000 times
conc. grad.
When action
potential reaches
T tubules…
_________diffuse towards the
myofibrils and their
myofilaments
Now how do we convert an action potential
into a contraction?
Ca2+ ions
bind with
troponin
which causes
tropomyosin
to…
Exposed active sites are bound to heads
of myosin forming a ________________
Now how do we convert an action potential
into a contraction?
When cross-bridges
form, then energy
stored in ________
_______ is released
as mechanical
motion of heads
“snapping back”
pulling thin
filaments towards
each other (Power
stroke).
Now how do we convert an action potential
into a contraction?
ATP is used to
release cross-bridge
ATP is then
converted to ADP to
“re-cock” the
myosin head
(_______________)
What about relaxation?
Myofibrils CAN NOT exert a
force in two directions!!!
So in this sense relaxation is
passive. It depends on:
1) Series-Elastic components
(elasticity)
2)
However, relaxation
DOES require
energy!
Where and Why?
3)
?Rigor mortis?
How do we get a whole muscle response based
on individual muscle fibers?
Muscle fibers contract
in an “All-or-none”
fashion.
To control force of a
whole muscle
contraction, you must
control the _________
of muscle fibers
contracting.
Each motor neuron and the
muscle fibers it innervates is
called a _____________
Take 5!!!
Not all skeletal muscles are
organized with the same # of muscle
fibers per motor unit.
Which muscles would you expect
to have >#s of muscle fibers/motor
unit?
Eye muscles
or
Quadriceps muscles
Why?
Discuss with your
neighbor and predict
an answer.
What are the attributes of a single muscle twitch?
A single muscle
twitch can be
divided into distinct
phases:
Lag phase
Contraction phase
Relaxation phase
(Refer to table 9.2 for
specific events
associated with each
phase)
What happens when frequency of stimulus
increases?
_________________
Increase in tension
due to 2 things:
1) additional ____ in
sarcoplasm
2) ___________
________ already
stretched
What happens when the strength of the stimulus
increases?
Spatial Summation
Increased stimulus
strength results in
additional motor
units being
recruited.
Subthreshold
Threshold
Submaximal
Maximal
Can muscles exhibit more
than one type of
contraction?
__________
?
(metri~length)
The muscle length doesn’t
change… but tension does!
_______
(iso~equal)
The muscle tension doesn’t
change but the length does!
_______________
Muscle shortens under
tension
_______________
Muscle lengthens under
tension
How does muscle performance relate to
initial length of muscle?
Muscles have an optimum length for maximal contraction
force (tension).
Where do muscles get their energy?
Immediate: (6 seconds of sprinting)
Use up small amount of ____ present,
then phosphorylation of ____ with
other ADP and creatine phosphate (CP)
Short-term: (30-40 seconds - 3 min.)
_____________, using blood glucose and glycogen in
the glycogen-lactic acid system
Long-term: (Hours?!?)
Respiratory and Cardiovascular systems catch up…
_________________________
What are the ways in which muscles can fatigue?
1) ___________ As the term implies, brain’s influence on
motor neuron and muscular activity
2) ___________ Fatigue resulting directly from muscle’s
energy supply:
ATP shortage
Lactic acid build-up
3) ___________ Depletion of What?
Acetylcholine
How can you increase endurance?
Since after several minutes,
muscles depend mostly (90%) on
aerobic respiration for ATP
production, Endurance is
dependent on…
Also depends on organic
nutrients particularly glucose
and fatty acids… Carbohydrate
loading can “pack” 4-5g/100g
of muscle BUT also
2.7gH2O/1g glycogen
With high VO2 max, can you exert indefinitely?
Definitely NOT!
Even with great lung capacity,
sustained activity will exceed
O2 supply…
•
Resulting in _______
•
(Exercise rate - Resting rate).
•
Breathing continues after
exercise for the following
reasons
•
Are all muscle fibers created equal?
Slow twitch
Fast twitch
(high-oxidative fibers, type I)
(low-oxidative fibers,
fast glycolytic, type II)
As name implies slower
“twitch” time
Fast “twitch” time
Larger in diameter
Numerous mitochondria
Poorer blood supply
Myoglobin
Fatigue rapidly
Take 5!!!
What kind of exercise regimen is
appropriate for people who are
training to be endurance runners?
What effect will the composition
of their muscles, in terms of
muscle fiber type, have on their
ability to perform in an
endurance race?
Discuss with your
neighbor and predict
an answer.
What are the effects of exercise?
High intensity (anaerobic) affects fasttwitch fibers greater than slow-twitch.
Aerobic exercise improves vascularity
and mass of slow-twitch fibers.
Can you convert one fiber type to
another? If so, which types are
“convertible”? (Read the handouts and
discuss these questions).
You can’t add more muscle fibers, so
how do muscles increase in size?
What is Muscular Dystrophy?
Group of diseases that result in muscular
atrophy and conversion to connective tissue.
Duchenne’s MD is sex-linked
The faulty gene is responsible for the
production of dystrophin, which is found in
the sarcolemma and is thought to be involved
with resistance to mechanical stress AND/OR
allows Ca2+ to leak from sarcoplasmic
reticulum causing the activation of
Phospholipase A, an enzyme that breaks
down plasma membranes destroying the cell.
How is smooth muscle different?
_________
Spindle shaped
____________
Non-striated… Why?
Ca2+ works differently to
regulate muscle contraction
NOT an “All or None”
contraction
How is smooth muscle different?
Hormone binds
with receptor
G proteins cause
Ca2+ channels to
open
…
How is smooth muscle different?
Myosin kinase
becomes active
Catalyzes ATP to
ADP
P used to “cock”
myosin head
___________
removes phosphate