Muscles and Movement Flashcards
What is muscle tissue?
long cells called muscle fibers that contract in response to nerve signals
responsible for most forms of movement in complex animals
What are the three types of muscle tissue?
skeletal: voluntary movement
smooth: involuntary movement
cardiac: heart contraction
What are the general properties of muscle cells?
contractility: interaction of action and myosin to shorten cells
excitability: muscle cells rapidly change ion charge to respond
What is a muscle fiber?
a single cell with many nuclei (multinucleate) but with just a single plasma membrane (Sarcolemma)
innervated by a motor neuron to cause contraction
What are myofibrils?
bundles of actin and myosin in a muscle fiber
segmented in sarcomeres and highly ordered
Where is actin anchored?
the z-line
Where is myosin held?
the m-line
How does contraction work?
atp driven motors
motors pull actin along myosin
filaments stay the same length, they do not shorten
What is a neuromuscular junction?
synapse between neuron and muscle cell
What is acetylcholine?
neurotransmitter released by presynaptic neuron
What are t-tubules?
extensions of plasma membrane that go deep into the cell
What is the sarcoplasmic reticulum?
special ER lining myofibrils; stores Ca2+
releases Ca2+ which inactivates proteins that block myosin-actin binding
What is tropomyosin?
a regulatory protein that binds to actin and blocks binding of myosin heads
What determines the precision of movement?
the amount of motor units that are recruited
rate at which fibers are stimulated
What is a motor unit?
single motor neuron, and all muscle fibers it innervates
