(08) Skeletal Muscle II Flashcards
(Types of Muscle Contraction)
_____ - Force generation with no change in muscle length (pushing hands together)
_____ - Shortening of a muscle against a constant load (it moves something)
- isometric
- isotonic
(Isometric Contractions)
Relationship between _____ and _____ intensity.
This bypasses the _____ and only acts on the _____.
- If a muscle is electrically stimulated a small pulse will illicit a _____ contraction. Increasing the _____ of the stimulus with increase the _____ produced.
The increase in force is due to _____.
The force will continue to increase until all of the fibers ____. Further increases in stimulation amplitude will _____ the amount of force produced.
- force, stimulus
- neuromuscular junction, voltage gated Na channels
- small, amplitude, force
- recruitment of additional muscle fibers (cells)
- have been engaged, not change
Isometric Contractions
- Relationship between force and stimulus frequency
- If a muscle is electrically stimulated by a single it will illicit a _____.
- Two simuli that ocur close together in time will produce a ____ force than produced during a single twitch.
- Increasing the frequency of stimulation will continue to _____ the force until _____ is reached.
What do you call the process of these individual forces being added together?
- twitch response
- greater
- increase, tetanus (maximum force)
- summation
Time course of force generation
Duration of a motor neuron actional potential?
Duration of a muscle action potential?
Duration of a muscle twitch?
Note the calcium levels here
- 1 ms
- 10 ms
- 100 ms
Note the calcium levels here (this is what makes the constant signals increase force - allows summation)
egg
(Engagement of Elastic Elements)
- Muscle has both ____ and ____ elastic elements - give examples of each - What do these do?
High frequency stimulation
- ______ the elastic recoil between contractions
- _______ force loss required to stretch elastic elements
- _______ the force measured at the end of the muscle
- internal (titin and nebulin filaments), external (tendons and connective tissue) - provide elasticity that must be overcome to cause movement
- decreases
- decreases
- increases
What is the basic contractile component of the muscle cell?
(just look at picture)
titin is the squiggly running from a-z-line to myosin (3 per myosin) - is a huge protein - may also be force sensor - will tell muscle cell to grow if it needs to
Nebulin is on the thin filament - also very long
- the sarcomere
just look at this
for a spell
(Contractie Proteins)
- Myosin is made up of _____ protein, _____ tail, two _____ domain called _____.
- On the actin filaments you have a couple of regulatroy proteins, _____ and _____ - these are important because this is where _____ sensitivity comes in
- assymetric, alpha-helical, globular, heads
- tropomysin, troponin, calcium
(The Molecular Mechanism of Muscle Contraction)
- What binds the ATP? What can it be described as?
What happens to myosin when i hydrolyzes ATP? Does it hold on to ATP (ADP and Phosphate)?
What happens when Ca+ is released?
Will it keep going if Ca is present?
Why are asynchronous attachements the best?
- globular part of myosin, a mechanoenzyme (it hyrdorolizes ATP)
- it stores energy (like cocking a gun), yes (by holding onto it it is ready for contraction)
- It returns to original conformation (power stroke), and releases its stuff
- yes
- this allows for a better sustainment of force (rather than off/on)
(Control of Muscle Contraction)
What is calcium signal due to? What does this cause?
What are the other two components? What do they do?
In the relaxed state (free of Ca), tropomysoin ______ with myosin head binding
- In smooth muscle, calcium interacts directly with the ______
- troponin-C (a calcium binding protein), causes troponin and tropomyosin to move on surface of the thin filament
- troponin T and troponin I - they transmit the Calcium binding to the tropomyosin filament
- intereferes
- myosin
(Length-Tension Relationship)
Look at this
The blue line is due to elastic element stretching (nothing to do with myosin)
We get maximum force when there is optimum overlap of the thick and thin filaments (L0)
If stretched enough cross bridges can’t interact even if calcium is present
When it gets too short - can’t generate a lot of force - due to disorder - thin filaments cross over into next sarcomere - myosin go to z line
- Our skeletons kind of keep muscles in the gold zone - but if a tendon fucks up you can get too short or too long
yep
(Length-Tension Relationship)
Ascending Limb - Force reduced due to _____ (disorder)
Plateau - maximal _____ force
Descending Limb - Force Reduced due to _____
- Steric interference
- isometric
- overlap
(Isotonic Contractions)
more about the ____ of contraction
Factors that Affect Muscle Shortening
_____ - the force that sets the ______ of and establishes the degree of _____ at the initiation of muscle contraction.
_____ - the force that _____ the muscles shortening. The load the muscle is _____ to move. This will affect the _____.
(The Force-Velocity Relationship)
(Look at picture) As afterload increases the velocity decreases until we reach a position where it will stop.
When you reach the point where you can no longer move it - that is _____ contraction.
- speed
- Preload, initial length, crossbridge
- Afterload, opposes, attempting, velocity
- isometric
What is a motor unit?
Large Motor neurons innervate ____ muscle cells.
Small motor neurons innervate _____ muscle cells.
- A motor unit consists of a motor neuron and the collection of muscles it innervates
- large
- small
