Muscular System Overview in Anatomy & Physiology

Movement

Gross muscle movement, smooth muscle (peristalsis, blood vessels)

Stability

Postural muscles

Control of Body Openings

Sphincters

Heat Production

The process by which muscles generate heat.

Origin

Point where muscle attaches to stationary bone.

Insertion

Point where muscle attaches to moving bone.

Belly

Thick, middle region of the muscle.

Characteristics of Skeletal Muscle

Work in opposition; muscles pull (never push); muscle tendons cross the joint(s) they have actions at.

Prime Movers (Agonist)

Provides the major force for a specific movement.

Antagonists

Muscle opposite to agonist that relaxes.

Synergists

Muscle(s) that assist agonist.

Stabilizer

Contracts to support the body segment so the main action can be completed.

Neutralizers

Muscle that acts to prevent an undesired motion.

Example - Leg Curl

Agonist - Hamstrings; Synergist - Gastrocnemius; Antagonist - Quadriceps; Stabilizer - Abdominal muscles (core); Neutralizer - Adductors (to prevent hip from abducting).

Location

Bone or body region associated with the muscle.

Shape

e.g., deltoid muscle (deltoid = triangle).

Relative Size

Maximus (largest), minimus (smallest), longus (long).

Direction of Fibers

Rectus (fibers run straight), oblique (fibers run at angles to an imaginary defined axis).

Number of Origins

Biceps (two origins), triceps (three origins).

Action

Flexor or extensor, as in the names of muscles that flex or extend, respectively.

Hamstring to quad ratio

Quads are 20-40% stronger; hamstring:Quads 60-80%.

Rotator cuffs

Stabilizes the shoulder.