Ch. 50 D Flashcards
What does a response in muscle activity come from?
input from the nervous system
what does muscle contraction rely on?
interactions between thin filaments (actin) and thick filaments (myosin)
What does skeletal muscle do?
moves bones and the body
What are the units of hierarchy in muscles? (5)
1) Muscle
2) fascicle
3) muscle fiber
4) myofibrals
5) sarcomere
what is a fascicle?
bundle of muscle fibers
how are myofibrils arranged?
longitudinally
What is a sarcomere?
smallest functional unit of muscle
bordered by z lines
What is special about z lines?
where thin filaments attach
explain the basics of the sliding filament model
thin and thick filaments ratchet past each other longitudinally, powered by myosin molecules
Why are skeletal muscles called striated?
arrangement of myofilaments create dark and light band patterns
Explain the simple process of muscle contraction? (4)
1) head of myosin binds to actin filament
2) cross-bridge is formed
3) cross bridge pulls thin filaments towards sarcomere
4) cycle of binding and releasing is repeated
What is the term for the binding of the head of myosin to actin filament?
cross-bridge
What inhibits actin and myosin from interacting? How?
tropomyosin and troponin complex, by covering myosin binding sites on actin
What binds to the troponin complex to expose myosin binding sites?
Ca2+
explain the signaling process (6)
1) stimulus from motor neuron action potential makes a synapse with muscle fiber
2) The synaptic terminal releases acetylcholine
3) acetylcholine depolarizes muscle cell
4) action potential travel to interior muscle fiber along the transverse tubules
5) causes sarcoplasmic reticulum to release Ca2+ initiating muscle fiber contraction
6) motor input stops
What are the 2 diseases associated with muscle contractions?
1) amyotrophic lateral sclerosis (ALS)
2) Myasthenia gravis
What are the characteristics of amyotrophic lateral sclerosis?
1) interfere with the excitation of muscle fibers
2) usually fatal
What are the characteristics of myasthenia gravis?
2) autoimmune disease that attacks acetylcholine receptors on muscle fibers
2) treatments exist
Contraction of whole muscle is _______. Why?
graded; extent and strength can be voluntarily altered
What are the 2 mechanisms for producing graded contractions?
1) varying the number of fiber contractions
2) varying the rate at which fibers are stimulated
What are some characteristics of muscles and motor neurons in vertebrates? (2)
1) one motor neuron synapses with multiple muscle fibers
2) each fiber is controlled by only 1 motor neuron
What is a motor unit?
consists of a single motor neuron and all the muscle fibers it controls
What is recruitment?
process which more and more neurons are activated
What does recruitment cause?
increase in force developed by a muscle
What is twitch?
results from a single action potential in a motor neuron
more rapid _______ produce a graded contraction through _______.
action potentials; summation
What is tetanus?
a state of smooth and sustained contraction produced when stimulation is so high that muscle fibers cant relax between stimuli
What is tetany?
the strongest muscle contraction
What is origin? (regarding muscle)
point of attachment of a muscle that remains relatively fixed during contraction
What is incersion? (regarding muscle)
point of attachment that moves towards the origin during muscle contraction
