Human muscular system, the voluntary muscles of the skeleton that regulate movement, posture, and balance. Human muscle is classified into striated (or skeletal), smooth, and cardiac muscle.
- Smooth muscle is present in blood vessel walls in the urinary bladder, intestines, and stomach.
- Cardiac muscle is involuntary and controls the heart's rhythmic contractions. Human smooth muscle and cardiac muscle are arranged similarly to other vertebrates.
This article discusses the skeletal muscles of the human body, focusing on muscular motions and alterations caused by upright position.
The article muscle discusses smooth muscle, cardiac muscle, and muscle contraction physiology. Muscular disease describes muscle problems.
The next sections describe significant muscle groups and their activities to help you comprehend gross human muscular anatomy. Coordinated muscle groups govern bodily motions.
- Neck: Neck motion includes rotation, flexion, extension, and sidebending (i.e., the motion used to touch the ear to the shoulder). Action might be ipsilateral or contralateral to the contracting muscle. Rotation is a key cervical (neck) spine motion.The sternocleidomastoid muscle turns the neck. The sternocleidomastoid muscles flex the neck and elevate the sternum to help with vigorous breathing.The anterior and middle scalene muscles on the sides of the neck rotate the neck and raise the first rib. Back of the neck muscles splenius capitis and cervicis rotate the head. The cervical spine also bends sideways.Cervical side bending involves the sternocleidomastoid muscles. The posterior scalene muscles bend the neck to the side and raise the second rib. Splenius capitis and cervicis help side bend the neck. Iliocostalis, longissimus, and spinalis are massive, deep back muscles. All three side-bend the neck ipsilaterally.
- Skeletal muscle: A muscle of this sort is responsible for generating bodily motion. Skeletal muscles, of which there are more than 600, account for around 40% of a person's total mass. Groups of muscles work together to move the skeleton in response to impulses from the neurological system. There is some degree of will involved in producing these signals and actions, but they are still not completely automatic. We humans, however, can move without paying attention to each individual muscle.
- Cardiac muscle: Muscle in the heart occurs automatically. The walls of the heart are made up of this kind, and in response to brain instructions, they beat steadily and rhythmically, pumping blood throughout the body. Although this muscle group is responsible for generating the electrical impulses that cause the heart to contract, they may be altered by other factors, such as hormones and nervous system stimulation (which is why, for example, a frightened person's heart rate rises).
- Smooth muscle: The walls of your hollow organs, airways, and blood arteries are all composed of smooth muscle. Moving like waves, it helps transport items like food and urine through the digestive and urinary systems. Similar to cardiac muscle, smooth muscle is involuntary and only contracts in reaction to external stimuli or nerve signals.