Chapter 50 (Muscle and Skeleton)

Smooth muscle

(not striated )muscle tissue in which the contractile fibrils are not highly ordered, occurring in the gut and other internal organs and not under voluntary control.

Hydrostatic skeleton

A fluid skeleton in many soft-bodied invertebrates, including annelids, that allows an organism to change shape but not volume.

How is energy provided for contraction?

ATP

sliding-filament model of contraction

In the relaxed state, thin and thick filaments overlap only slightly. During contraction, myosin heads bind to actin, detach, and bind again, to propel the thin filaments toward the M line. As H zones shorten and disappear, sarcomeres shorten, muscle cells shorten, and the whole muscle shortens

Which protein does the work? (sliding-filament)

Myosin

What are the roles of actin, myosin, and troponin?

Myosin is the motor and runs along the fixed Acton (rope) filament and troponin stops or allows the myosin to attach to the Acton.

What is a myofibril?

The myofibrils in muscle fibers are made up of repeating sections called sarcomeres, which are the basic contractile units of skeletal muscle.

neurotransmitter

a chemical substance that is released at the end of a nerve fiber by the arrival of a nerve impulse and, by diffusing across the synapse or junction, causes the transfer of the impulse to another nerve fiber, a muscle fiber, or some other structure.

A sarcomere?

contractile unit of a muscle fiber

Exoskeleton

external skeleton; tough external covering that protects and supports the body of many invertebrates

Skeletal muscle

has striations (from sarcomeres), voluntary, controlled by nerves

Endoskeleton

internal skeleton or supporting framework in an animal

Cardiac muscle

striated, involuntary, contains pacemaker cells; influenced by nerves and hormones