Muscle Contraction Flashcards
Type I fibers are also called…
Slow twitch
Type IIa fibers are also called…
Fast twitch intermediate
Type IIb fibers are also called…
Fast twitch
Describe the characteristics of type I fibers
Fatigue resistant, contain myoglobin (red), oxidative metabolism, high mitochondria count, low glycogen
Describe the characteristics of type IIa fibers(Intermediate)
Fatigue resistant, lesser amt of myoglobin (red and white), oxidative metabolism, higher mitochondria, high glycogen
Describe the characteristics of type IIb fibers
Easily fatigued, low myoglobin(white), Glycolytic metabolism, fewer mitochondria, high glycogen
Describe the steps in skeletal muscle contraction (7 steps hint)
1) ACh neurotransmitters are released from presynaptic cleft and diffuses across the synaptic cleft; they attach to ACh receptors on the sarcolemma
2) AP is generated along sarcolemma and down the T-tubules
3) Ca2+ release from terminal cisternae of SR is triggered by AP
4) Ca2+ ions bind to troponin(TnC) causing it to move from its actin active site blocking position and exposing the binding sites
5) Contraction; the myosin cross bridges attach to actin and detach which pulls the actin filaments towards sarcomere center. ATP is releasing energy which powers this process
6) Ca2+ is removed by active transport into the SR after end of AP
7) Tropomyosin moves back to its original actin active site blocking position. Contraction ends.
Describe the 3 steps of termination of skeletal muscle contraction
1) Ca2+ pump and Na-Ca exchanger on plasma membrane pump Ca2+ out of cell
2) Ca2+ pump isolated some Ca2+ in the SR
3) Ca2+ is bound in SR by calreticulin and calsequestrin
What three phases make up a muscle twitch?
Latent period, contraction, and relaxation
A muscle twitch is…
A contraction generated by a single AP
Describe the latent pd
A 1-2msec delay from when the AP reaches the muscle until tension is observed
The random firing of motor units is responsible for
Muscle tone
What is “unfused tetany”?
When the stimuli frequency increases causing successive muscle contractions to blend almost appearing as a single, large contraction
What is “complete/fused tetany”?
When the frequency of stimuli continues to increase causing the muscle contractions to fuse together and create one contraction
Recruitment/spatial summation is…
When multiple neurons are weakly stimulated simultaneously and impulses are converted into a single, larger neuron
Temporal summation is…
When a single neuron is rapidly stimulated
Isometric contractions are when…
The muscle contracts but there is no change in muscle length nor any motion. When the muscle is contracted the tension is high
Isotonic contractions are when…
The muscle contracts and changes length, resulting in motion.
Describe the 7 steps of slow wave generation in smooth muscle
1) voltage gated Ca2+ channels open
2) AP spike occurs
3) Ca2+ influx causing increase in Ca2+ ICF conc.
4) Ca2+ dependent K+ channels open
5) slow hyperpolarization
6) voltage-gated Ca2+ channels close; Ca2+ ICF conc decreases
7) Ca2+ dependent K+ channels close
Name the 3 types of smooth muscle APs
1) Spike
2) Plateau
3) Slow waves
Describe the steps of cross bridge cycling
1) Ca2+ enters ECF through SR and membrane proteins
2) Ca2+ binds to and activates calmodulin
3) Activated calmodulin activates kinase
4) Contraction is stimulated by activated(PHOSPHORYLATED) myosin molecule
How are muscle spindles arranged and what do they detect?
Parallel to contracting skeletal muscle; detects muscle length
How are golgi tendon organs arranged and what do they detect?
Arranged in series with contracting muscle fibers, detects muscle tension
Intrafusal muscle fibers are another name for…
Muscle spindles
