The Muscular System

Functions of the Muscular System Movement -what examples can you think of? Maintaining posture and body position Stabilizing joints Heat generation (generates 85% of the body’s heat…especially skeletal muscle) How does this happen?

Structures of the Muscular System Muscle fibers Long, slender cells that make up the muscle Each muscle consists of a group of fibers that are held together by a connective tissue and enclosed in a fibrous sheath Fascia Sheet of connective tissue that covers, supports, and separates muscles or groups of muscles Flexible tissue but not elastic. Crush injuries can cause compartment syndrome

Structures of the Muscular System Tendons Narrow band of non-elastic, dense fibrous connective tissue that attaches a muscle to a bone ***do not confuse with a ligament! Ligaments connect bone to bone

Types of Muscle Tissue Smooth Located in the walls of internal organs like the digestive tract and blood vessels, and ducts Move and control the flow of fluids through these structures Unstriated Involuntary

Types of Muscle Tissue Skeletal Attached to the bones of the skeleton and make movement possible Voluntary Striated (appear striped)

Types of Muscle Tissue Myocardial (Cardiac) Form the muscular walls of the heart Striated Involuntary

How do Muscle Move? Muscle innervation Muscles are supplied with motor nerves Motor nerves enable the brain to stimulate a muscle to contract When the stimulus stops, the muscle relaxes If nerve impulse is interrupted due to injury or disease, paralysis occurs

Muscle Innervation

Antagonistic Muscle Pairs Muscles are arranged into antagonistic pairs When one muscle contracts, it’s antagonist relaxes Example: Biceps and Triceps work as a pair to make arm movement possible Contraction: The tightening of a muscle. As a muscle contracts, it shortens and thickens causing the belly of the muscle to enlarge Relaxation: Occurs when a muscle returns to its original form. As the muscle relaxes, it elongates, thins and the belly is no longer enlarged

Contrasting Muscle Motion Abduction: moves away from the midline Adduction: moves toward the midline Flexion: decreases an angle as in bending a joint Extension: increases an angle, as in straightening a joint Elevation: raises a body part. Ex. Smiling Depression: lowers a body part. Ex. Frowning Rotation: turns a bone on its own axis Circumduction: the circular movement at the far end of a limb Supination: turns the palm of the hand upward or forward Pronation: turns the palm of the hand downward or backward Dorsiflexion: bends the foot upward at the ankle Plantar flexion: bends the foot downward at the ankle Hyperextension: extreme overextension of a limb or body part beyond its normal limit

How Muscles are Named Muscles can be named for their insertion and origin points Origin: the less moveable attachment. The place where the muscle begins Insertion: the more moveable attachment. This is the place where the muscle ends by attaching to a bone or tendon. Example: the sternocleidomastoid (SCM) muscle is named for its two points of origin (sternum and clavicle) and the one point of insertion (mastoid process).

Example: the sternocleidomastoid (SCM) muscle is named for its two points of origin (sternum and clavicle) and the one point of insertion (mastoid process).

How Muscles are Named Some muscles can be named for their location on the body or the organ they are near: Example: pectoralis major Pectoral means pertaining to the chest and the Pectoralis major is the large, fan shaped muscle of the chest.

How Muscles are Named Muscles may be named for their action Flexor carpi muscles flex the wrist Extensor carpi muscles extend the wrist Muscle may be named for fiber direction Oblique means slanted or at an angle Rectus means in strait alignment Transverse means in a crosswise fashion Sphincter is a ring-like muscle that constricts the opening of a passageway. Ex. Anal sphincter

How Muscles are Named Some muscles are named for the number of divisions forming them. Biceps brachii is formed from 2 divisions Tricps brachii is formed from 3 divisions Muscles may be named for their size or shape Gluteus maximus is the larges of the gluteal muscles The Deltoid muscle is shaped like an inverted triangle or the Greek letter Delta

How Muscles are Named Some muscles are just named for strange reasons… Example: the hamstring group is the group of muscles located at the back of the upper leg and these are the muscles by which a butcher hangs a slaughtered pig!