Excitation Contraction Coupling Flashcards
What property of muscle refers to its ability to shorten and generate force?
Contractility
What property of muscle refers to its ability to receive an electrical stimulus and generate an action potential from its resting potential?
Excitability
What property of muscle refers to its ability to return to its resting length after being stretched?
Elasticity
What property of muscle refers to its ability to be stretched back to its resting length?
Extensibility
What type of muscle makes up 40% of body weight, attaches to bones, and is under voluntary control via somatic motor neurons?
Skeletal muscle
What type of muscle is involuntary, auto-rhythmic but influenced by autonomic nervous system?
Cardiac muscle
What type of muscle lines the walls of hollow organs, blood vessels, eyes, glands, uterus, and skin, is involuntary with endocrine and autonomic nervous system inputs?
Smooth muscle
________ neurons stimulate muscle fibers to contract, axons branch so each muscle fiber is innervated, and form a neuromuscular junction
Motor
_______ is the plasma membrane of the muscle cell, which has invaginations of sarcolemma through the muscle fibers called ___________
The _______ _______ is the calcium storage site for the muscle cell.
Sarcolemma; T-tubules
Sarcoplasmic reticulum
______ is a sarcomere structure that serves as the attachment for thin filaments
Z-disk
______ is a sarcomere structure that serves as the attachment for thick filaments
M-line
Which part of the myosin has ATPase activity?
Heavy chain
What are the 3 subunits of troponin?
Troponin T - binds tropomyosin
Troponin C - binds calcium
Troponin I - inhibits actin binding to myosin
______ covers the myosin binding sites until troponin binds calcium and removes it so that actin can bind
Tropomyosin
If the heavy chain of myosin has the ATPase activity, what does the light chain do?
Regulatory activity
______ is the elastic protein responsible for binding myosin to the Z-discs
Titin
______ is the protein that serves as a scaffold for actin in the sarcomere
Nebulin
What part of the sarcomere serves as the attachment site for actin? How does this area change during sarcomere shortening?
Z-disc - the z-discs move closer together during contraction of the sarcomere
What part of the sarcomere serves as the attachment site for myosin?
M-line
What part of the sarcomere is made up of mostly myosin? Does this part change length during contraction of the sarcomere?
A-band - does NOT change length!
What part of the sarcomere is made up of actin only? Does this part change during contraction?
I-band; YES it shrinks during contraction of the sarcomere because actin filaments are pulled closer together
What part of the sarcomere is composed of myosin only and changes length during contraction?
H band (center of sarcomere, shrinks when actin filaments get closer together)
Briefly describe the events leading up to a depolarization at the sarcolemma
Action potential travels from motor neuron to muscle fiber at the neuromuscular junction
ACh is secreted into synaptic cleft and binds to nicotinic ACh receptors, increasing sarcolemma permeability to Na+, which opens the voltage gated sodium channels, initiating depolarization on the sarcolemma
Once a depolarization/AP occurs on the sarcolemma, what events follow?
Calcium from the EC space enters through the voltage gated calcium channels (DHP receptors), which lie in close proximity to the ryanodine receptors on the sarcoplasmic reticulum.
Calcium exits the SR through the RyR into the cytosol, helping to initiate contraction in the sarcomere.
The action potential ends, and calcium is pumped out of the cytosol via SERCA and the Na+/Ca++ exchanger
