Ca²⁺ plays a critical role in the regulation of muscle cell contraction and relaxation. Motor neuron stimulation and subsequent the action potential signals the release of Ca²⁺ from the sarcoplasmic reticulum. The ions bind to troponin—a protein found in a complex with tropomyosin and bound to actin filaments—and exposes the myosin-binding sites on the actin filament by shifting the troponin-tropomyosin complex. With the myosin-binding sites revealed, the myocyte will be able to contract.

In the absence of calcium in the cell, the binding sites on the actin filament cannot be made available and myosin will not bind. No contraction will occur.

There are three types of muscle tissue: skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscle is under voluntary control and is mainly responsible for locomotion and skeletal movement. Smooth muscle is involuntary and surrounds the viscera to aid in vascular constriction and organ movement. Cardiac muscle is found only in the heart and is responsible for pumping the blood.

The smooth muscle of the digestive tract is responsible for the wavelike movement of peristalsis. In humans, peristalsis is primarily responsible for helping move food down the digestive tract. It is important to understand that peristalisis is an involuntary movement.

The three types of muscle in the body are smooth, skeletal, and cardiac muscle. The type of muscle lining artery walls is smooth muscle, which is also present in many organs such as the intestines and the urinary bladder. Unlike skeletal muscle, smooth muscle control is involuntary and, unlike both skeletal and cardiac muscle, it is non-striated. Smooth muscle around the arteries and arterioles is important for regulating blood pressure and directing blood flow in the body.

Muscle is a major type of tissue in the human body. They contract and enable movement. The three major types of muscle tissues include skeletal, cardiac, and smooth tissues.

Skeletal muscle tissue is a categorization of muscle tissue that controls skeletal movement and posture. Skeletal muscle tissue is striated and made up of myocytes, which are organized into myofibrils. Skeletal muscle tissue can be categorized further into type I, type IIa, type IIx, and type IIb. These types include red—oxygenated—and white—deoxygenated—tissues.

Skeletal muscle tissue is involved in voluntary skeletal movement. Skeletal muscle can be divided into type I, type IIa, type IIx, and type IIb categories. Type I tissues exhibit slow contractions and type II are involved in fast contractions.

Skeletal muscle tissue is one of three types of muscle tissue. Skeletal muscle, as the name implies, is anchored to bones by tendons and controls skeletal movement and posture.

Smooth muscle tissue is a categorization of muscle tissue that is involved in involuntary contractions. Smooth muscle tissue can be found within the walls of organs such as the bladder, intestines, and stomach.

Smooth muscle tissue is involved in involuntary contractions. This type of muscle tissue is not striated and is bundled by connective tissue.

In smooth muscle tissue, contraction is involuntary and is caused by the sliding of actin and myosin filaments over one another. The function and mechanics of these contractions are generally the same in every organ; however, the physiological impact of each contraction may differ.