Muscle
Tissue
Organization
of Skeletal
Muscle
(macroscopic
anatomy)
What do the following prefixes mean:
peri-, endo-, epi-, myo-, and sarco-?
Describe how a muscle attaches to a
bone, as shown in this figure.
Why is there such a large connective
tissue component to skeletal muscles?
Internal organization of a muscle cell:
What are cisternae
and what chemical
is stored within the
cisternae of muscle
cells?
What is a myofibril?
= actin
= myosin
What is the functional unit of contraction in a muscle
fiber? Circle and/or label one in this diagram.
Each t-tubule is an extension
of the ________________.
A Sarcomere within a Myofibril
Organization of Myofilaments in a
Sarcomere
Energy Metabolism in Muscle Cells
(pages 165 & 166 in the course packet)
1. The phosphagen system
2. Aerobic cellular respiration
3. Fermentation (anaerobic metabolism)
What molecule serves as the energy source for fermentation?
Where does the muscle cell get these molecules?
The ATP cycle
Energy
from food
molecules
• ATPase breaks the last phosphate bond, releasing energy
– leaves ADP (adenosine diphosphate) and Pi
• ATP synthase catalyzes the addition of the terminal phosphate
group back onto ADP
Name the two locations where ATP synthesis takes place in a cell.
Phosphagen System
(Creatine Phosphate)
Can cells store ATP? Can cells store CrP?
Name the enzyme that controls these reactions. Where would
you find this enzyme, and why?
Anaerobic ATP Synthesis
(Fermentation)
Which source of fuel
molecules is more
important, and why?
What are the
consequences of lactic
acid production?
Why is anaerobic muscle
work more powerful than
aerobic muscle work?
What is the relationship
between lactic acid in the
blood and “oxygen
debt”?
Aerobic Cellular Respiration
What’s wrong with
this figure?!
Write the summary equation for aerobic cellular respiration.
What are the benefits of aerobic cell metabolism?
What substrate(s) are available for aerobic energy metabolism?
… for anaerobic metabolism?
Motor Units:
The functional unit of movement
Describe at least two
How many muscle cells are ways that these
neurons controlled.
in motor unit 1?
How many neurons in
motor unit 1?
What is the functional
classification of the neuron
in motor unit 1?
The Neuromuscular
(Myoneural) Junction
The appropriate term to describe an axon branch (as shown in these figures)
is ___________________.
The appropriate stimulus for skeletal muscle cells is
_____________________.
The specialization of the sarcolemma that contains receptors for acetylcholine
(ACH) is called ___________________.
The Transmembrane Electrochemical Potential
K+ is often allowed to “leak” out of the cell.
How does the Na-K pump contribute to the “potential”?
Why is the cell membrane described as “polarized”?
The Action Potential
At time 0, does the membrane begin
to depolarize or repolarize?
Unlike the graded potentials that
get larger with increasing
stimulus strength (e.g. at the
motor end plate), the action
potential is an all-or-none*
response.
Will a stronger stimulus produce a
larger action potential? Explain.
Give an example of where a graded
potential would take place.
Refractory
Period
Differentiate between the
absolute refractory period
and the relative refractory
period.
Why is the refractory
period important in muscle
cells?
Why is the refractory
period important in
neurons?
Refractory Period
from L. = “stubborn”
Chemical Synapses
The calcium channels on the synaptic
terminal are
-gated.
The sodium channels on the postsynaptic membrane are
-gated.
The ion channels involved in the
propagation of the Action Potential
are
-gated.
Vesicle Transport in Exocytosis
Events at the
Neuromuscular
Junction
Is the release of neurotransmitter
active transport or passive
transport?
Is the influx of Na+ ions by active
transport or passive transport?
How does the influx of Na+ ions
change the transmembrane
electrochemical potential?
Are the calcium channels in cisternae voltage-gated or chemically-gated?
Besides Ca+2, what must also be present in order for myosin to bind to actin?
Study the outline beginning on page 170 in your packet.
Muscle fiber
Nucleus
Motor neuron
Sarcolemma
Myofibrils
Sarcoplasmic
reticulum (SR)
SR Cistern
T-tubule
(a portion of the sarcolemma is peeled away in this view)
Action potential reaches synaptic terminal of motor neuron
New AP generated at motor end-plate and propogated down Ttubules
Myofibrils (relaxed)
Sarcomere
(Sarcolemma and other structures not shown)
Myofibrils (contracted)
Sarcomere
Sarcomere (relaxed)
Myosin
(thick filaments)
Actin
(thin filaments)
Sarcomere (contracted)
Myosin
(thick filaments)
Actin
(thin filaments)
Myosin
heads
Myosin
(thick filaments)
Actin
(thin filament)
Actin
Protein
complex
Myosin head
ADP and
phosphate
Note that ATP is hydrolyzed at this point, but still attached to
myosin head.
Protein
complex
ADP and
phosphate
Calcium
ion
Myosin-binding
sites (exposed)
Actin
ADP and
phosphate
Myosin head
Actin
Myosin head
AD
P Pi
1. Release of Pi initiates the power stroke.
2. At the end of the power stroke, ADP is released.
3. A new ATP is required for myosin to release its hold on
Actin
Myosin head
ATP
ATP binds to the myosin head, causing it to detach
from actin.
Actin
Myosin head
ADP and
phosphate
When the ATP is broken down to ADP and phosphate,
the myosin head extends.
Actin
Myosin heads
The sequence repeats as long as calcium ions are present.
The combined work of many myosin heads causes the actin
filaments to slide past the myosin filaments.
Actin
Protein
complex
Myosin heads
When the action potentials stop, calcium ions are pumped
back into the ER, the myosin-binding sites on actin are again
blocked, and the muscle relaxes.
Calcium
(Ca+2 in
green)
Actin
Myosin
Sarcomere