The Muscular System Functions of the Muscular System

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!