Muscular System

Some of the muscles of the body… click for larger image

The muscular system includes all muscle tissues of the body.  A few specific organs of the muscular system include the biceps brachii muscles, the pectoralis muscles, and the rectus abdominis muscle.

In terms of the general physiology of muscle…  All muscle tissues have one thing in common, they all contract when stimulated (the cells get shorter and pull on whatever they are attached to); in this way muscle converts chemical energy (ATP) into kinetic energy (movement).  The major job of all muscle is to create movement of various body parts, including movement inside the body.  We use muscle that are attached to bones to move our limbs and to breath, the muscle tissue in our hearts moves our blood, and smooth muscle in the walls of our digestive organs move food along our digestive tracts.  Muscles are also important for helping maintain body temperature as they generate heat when they contract.  Muscle is also important for opening and closing passages within the body and between the body and the outside world (sphincters between organs as well as the mouth and other openings).

Side note on body temperature control: In broad terms body temperature homeostasis is maintained by the interaction of four body systems: The muscular system generates heat, the cardiovascular system moves that heat throughout the body, the integumentary system releases heat as needed and the nervous system adjusts the activity of the other systems (through various negative feedback mechanisms) in order to maintain a relatively constant body temperature.

There are three different muscle tissue types, each with different cellular anatomy and physiology.

Below is a table comparing and contrasting the three forms of muscle tissue…

Type of Muscle TissueSkeletal MuscleCardiac MuscleSmooth Muscle
Type of Muscle TissueSkeletal MuscleCardiac MuscleSmooth Muscle
Cell ShapeLong tubesShort branched tubesFusiform shape (tapering at both ends), thinnest of the three.
Nucleimultiple nuclei outer edges of cellsingle nucleussingle nucleus
Striations?striatedstriatednot striated
Location in bodyMost attached to bonesOnly in heartfound throughout the body, usually wrapped around tubed organs
Voluntary or Involuntary?voluntaryinvoluntaryinvoluntary
Autorhythmic?not autorhythmic, only stimulated by nervous system.autorhythmicsome are autorhythmic
Innervation requirementsmust be innervated. Cells will atrophy and eventually die without innervationCan function without innervation, though innervation helps control heart ratesome require innervation and some do not
All have in commonall three contract when stimulated and use the same basic mechanism to create contraction

More for muscular system:

Muscular System in the lab

Connective tissues of muscle and muscle compartments

Muscle attachments (indirect vs fleshy)

Origin, belly, and insertion

Gross functions of muscle (prime mover, synergists, etc.)

Carpal tunnel syndrome

Muscle innervation and its clinical significance


Muscle injuries

Anatomy of a skeletal muscle cells

Myofilaments and the sarcomere

The neuromuscular junction

Motor units and recruitment

Excitation contraction coupling

Sliding filament theory

Length tension relationship

Twitch, summation, and tetanus

Isometric and isotonic contractions

Muscle metabolism

Classes of muscle fibers

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