What type of muscle excitable?

Excitable muscle refers to muscle tissue that has the ability to respond to stimuli by generating an action potential, leading to muscle contraction. There are two main types of excitable muscle tissue: skeletal muscle and cardiac muscle.

Skeletal muscle is voluntary muscle, meaning it is consciously controlled by the somatic nervous system. It consists of individual muscle fibers, each surrounded by a sarcolemma, which is the muscle cell membrane. When a nerve impulse reaches the skeletal muscle, it causes the sarcolemma to depolarize, leading to an action potential that propagates along the muscle fiber. This depolarization triggers the release of calcium ions from the sarcoplasmic reticulum, which bind to troponin and change the shape of the troponin-tropomyosin complex. This allows myosin heads to bind to actin filaments and form cross-bridges, leading to muscle contraction.

Cardiac muscle is involuntary muscle, meaning it is not consciously controlled. It is found in the heart and is responsible for the pumping action that circulates blood throughout the body. Cardiac muscle fibers are interconnected by specialized structures called intercalated discs, which allow for rapid and coordinated propagation of action potentials throughout the heart. When an action potential reaches the cardiac muscle, it causes the release of calcium ions from the sarcoplasmic reticulum, leading to the same sequence of events as in skeletal muscle contraction, resulting in the contraction of the heart muscle.

Both skeletal muscle and cardiac muscle are excitable, meaning they can generate action potentials in response to specific stimuli. However, skeletal muscle is controlled voluntarily by the nervous system, while cardiac muscle contracts involuntarily and is regulated by specialized cardiac conduction pathways.