Skeletal Muscle Contraction Flashcards
This is made up of multiple fascicles…
Muscle
What is the Epimysium?
Connective tissue surrounding the entire muscle
Perimysium
Connective tissue surrounding individual fascicle
What is a fascicle?
A bundle of myofibers
The delicate connective tissue surrounding each myofiber
Endomysium
What is the sarcolemma?
Cell membrane of muscle fiber
What is the myofiber?
Individual multinucleated muscle cell
A chain of sarcomere within a myofiber is?…
Myofibril
What is a Myofilament?
Actin and myosin filaments that make up a sarcomere
Invaginations of the sarcolemma, two per sarcomere, lie close to the cisternae of sarcoplasmic reticulum, and form triads with cisternae. I am?…
the T-tubules
Located at each end of the sarcomere that anchor actin filaments
Z discs
Composed entirely of actin and width changes during contraction
I-band
Composed of actin and myosin and the width does Not change during contraction
A-band
Composed entirely of myosin and width changes during contraction
H-band
Characteristic of skeletal muscle, sarcomeres are aligned to produce what?
A banding pattern
Excitation coupling of the muscle include which events?
1) action potential causing release of calcium ions
2) reuptake of calcium ions in repolarization
Voltage sensitive L type calcium channels arranged in quadruplets
Dihydropyridine receptors (DHP)
Causes a conformational change in the ryanodine receptor
DHP receptor
DHP receptors are located where?
Sarcolemma T-tubules
Opens in response to a conformational change by the DHP receptor
Ryanodine receptor
Ryanodine receptors are located?…
On the terminal cisternae of the sarcoplasmic reticulum
Ryanodine receptors release which ion into the cytosol from the SR?
Calcium
T/F is ATP required to pump calcium back into the SR?
True, using the SR calcium ATPase.
Which protein maintains an optimum concentration of Calcium in the SR?
Calsequestrin
What are the three uses of ATP required for muscle contraction?
- pump calcium back into the Sarcoplasmic reticulum
- pump sodium and potassium through the sarcolemma to reestablish resting potential
- used for the sliding filament mechanism
What is the concentration of ATP in a muscle fiber?
~4mmol, enough to maintain contraction for 1-2 seconds
There are three energies of rephosphorylation. What are they?
Oxidative metabolism
Glycolysis
Phosphocreatine
Provides energy for ~ 95% of all energy needed for long term contraction
Oxidative metabolism
Causes a lactic acid build up and can sustain contraction for up to 1min.
Glycolysis
Rapid release of energy using ATP to provide enough energy for 5-8 seconds of contraction
Phosphocreatine
What are the two types of muscle contractions?
Isometric and isotonic
When does isometric contraction occur?
When there is an increase in tension but not in length.
Ex: pushing against a brick wall
In isotonic contraction, the muscle length changes. What are the two definitions to describe this type?
Eccentric-occurs when muscle lengthens
Concentric- occurs when muscle shortens
Fiber types are classified mainly on?…
Endurance (resistance to fatigue) and speed of contraction
What are the two types of fibers?
Dark, slow fibers (red)
Light, fast fibers (white)
Myofiber types are determined by?
The innervating neuron
Contract rapidly, less endurance, fewer mitochondria, uses primarily anaerobic respiration, larger concentration of ATPases, little myoglobin
Fast twitch fibers
Contract slowly, more endurance, aerobic respiration, more mitochondria, less concentration of ATPase, more myoglobin
Slow twitch fibers
Lost muscle tissue is replaced by?
Scar tissue (fibrous connective)
Some muscles are almost entirely of one fiber type.
Soleus muscle is predominately? Gastrocnemius muscle is predominately?
Dark. Light
A neuron and the myofibers it innervates constitutes?…
A motor unit.
T/F all or none response refers to a motor unit.
True
Describe tetany?
The frequency of spikes is fast enough in which there is no time for relaxation. The muscle remains at maximal contraction
When electrical events occur faster than mechanical events. Additional spike can occur before previous Ca ions have been returned to the SR
Summation
This electrical event increases the total amt of Ca ions in the cytosol and increases the rate of cycling between the myosin and actin cross bridges thereby increasing muscle tension.
Summation
Lever systems are classified according to position of the fulcrum in relation to the in-force and the out-force. What is the first class? There are three total. Give an example
Fulcrum is in middle. In and out forces move in opposite directions.
Ex. Raising your chin using sternocleidomastoid or similar muscles.
Fulcrum= atlas/axis complex.
What is the second class lever system?
Resistance (out force) is in the middle
In and out force is on the same side of the fulcrum
Ex: raising the body on the ball of the foot
Fulcrum: ball of foot
Third class lever system?
Effort (in force) is in the middle
In and out force in on the same side of the fulcrum
Both forces move in the same direction
Ex: lifting a weight in the palm of your hand
