Summarizing Muscle Contraction and Locomotion

Summary

The body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Skeleton muscle tissue is composed of sarcomeres, the functional units of muscle tissue. Muscle contraction occurs when sarcomeres shorten, as thick and thin filaments slide past each other, which is called the sliding filament model of muscle contraction. ATP provides the energy for cross-bridge formation and filament sliding. Regulatory proteins, such as troponin and tropomyosin, control cross-bridge formation. Excitation–contraction coupling transduces the electrical signal of the neuron, via acetylcholine, to an electrical signal on the muscle membrane, which initiates force production. The number of muscle fibers contracting determines how much force the whole muscle produces.

Glossary

actin

globular contractile protein that interacts with myosin for muscle contraction

acetylcholinesterase

(AChE) enzyme that breaks down ACh into acetyl and choline

cardiac muscle

tissue muscle tissue found only in the heart; cardiac contractions pump blood throughout the body and maintain blood pressure

motor end plate

sarcolemma of the muscle fiber that interacts with the neuron

myofibril

long cylindrical structures that lie parallel to the muscle fiber

myofilament

small structures that make up myofibrils

myosin

contractile protein that interacts with actin for muscle contraction

sarcolemma

plasma membrane of a skeletal muscle fiber

sarcomere

functional unit of skeletal muscle

skeletal muscle tissue

forms skeletal muscles, which attach to bones and control locomotion and any movement that can be consciously controlled

smooth muscle

tissue occurs in the walls of hollow organs such as the intestines, stomach, and urinary bladder, and around passages such as the respiratory tract and blood vessels

thick filament

a group of myosin molecules

thin filament

two polymers of actin wound together along with tropomyosin and troponin

tropomyosin

acts to block myosin binding sites on actin molecules, preventing cross-bridge formation and preventing contraction until a muscle receives a neuron signal

troponin

binds to tropomyosin and helps to position it on the actin molecule, and also binds calcium ions