Chapter 10 Anatomy - Muscles

What four things distinguish muscle tissue from other tissues?

Contractility (myofilaments shorten muscle cells),

excitability (nerve signals excite muscle cells),

extensibility (contraction of skeletal muscle stretches opposing muscle),

elasticity (recoils after being stretched)

What are the plasma membranes and cytoplasm of muscle cells called?

Sarcolemma and sarcoplasm

How do skeletal muscle attachments work? What is the origin and insertion?

Most skeletal muscles run from one bone to another, generally over a joint. One bone moves and the other remains fixed. The origin is the less moveable attachment and the insertion is the more moveable attachment.

Describe muscle cells. What else are they called?

Muscle cells are also called muscle fibers. Fibers are long and cylindrical and are multinucleate. 

What are myofibrils? What are they made of?

Myofibrils are specialized contractile organelles found in muscle tissue. They are made of a long row of repeating segments called sarcomeres which are the functional unit of skeletal muscle tissue.

Define Z disc, M line, sarcoplasmic reticulum, motor unit, motor neuron, neuromuscular junction, terminal bouton (axon terminal), synaptic cleft

Z disc - boundaries of each sarcomere, looks like a Z

M line - the line thick filaments are anchored to

Sarcoplasmic reticulum - a specialized smooth ER for holding a lot of calcium ions. Interconnecting tubules surround each myofibril. When it is stimulated, it releases calcium which triggers contraction.

Motor neuron - nerve cell that innervates muscle fibers

Motor unit - a motor neuron and all muscle fibers it innervates

Neuromuscular junction - the point where nerve ending and muscle fiber meet

Terminal boutons/axon terminals - located at end of axons and stores neurotransmitters

Synaptic cleft: space between axon terminal and sarcolemma

Skeletal muscle

Striation	Striated
Nucleus	Multinucleate
Control	voluntary
Location	Most attach to bones

Smooth muscle

Striation	Not striated
Nucleus	One nucleus
Control	involuntary
Location	Walls of internal organs

Cardiac muscle

Striation	Striated
Nucleus	One nucleus
Control	involuntary
Location	Walls of the heart