Muscular System Notes

Muscular System Notes Part 5

Types of Body Movements • Muscles are attached to no less than two points • Origin – The attachment to the immovable or less movable bone • Insertion – The attachment to the movable bone • When the muscle contracts the insertion moves towards the origin

Common Types of Body Movements • Flexion – A movement that decreases the angle of the joint and brings two bones closer together • Example – Bending the knee or elbow, bending forward at the hip

Common Types of Body Movements • Extension – Opposite of flexion; Movement that increases the angle, or the distance, between two bones or parts of the body • Example – Straightening the knee or elbow • If extension is greater than 180 degrees, it is hyperextension

Common Types of Body Movements • Rotation – The movement of a bone around its longitudinal axis • Common movement of ball-and- socket joints • Example – Movement of the atlas around the dens of the axis (as in shaking your head “no”)

Common Types of Body Movements • Abduction – The movement of a limb away from the midline of the body • Example – Moving your leg laterally away from your body; Also applies to the fanning movement of the fingers and toes when they are spread apart

Common Types of Body Movements • Adduction – Opposite of abduction; The movement of a limb towards the midline of the body • Example – Moving your leg medially toward your body

Special Types of Body Movements • Dorsiflexion and Plantar Flexion– Up and down movements of the foot at the ankle • Dorsiflexion – Lifting the foot so that its superior surface approaches the shin (standing on your heels) • Plantar Flexion– Depressing the foot (pointing the toes)

Special Types of Body Movements • Inversion and Eversion – Also special movements of the foot • Inversion – The turning of the sole medially • Eversion – The turning of the sole laterally

Special Types of Body Movements • Supination and Pronation– Refer to movements of the radius around the ulna • Supination – Movement that occurs when the forearm rotates laterally so that the palm faces anteriorly, and the radius and ulna are parallel • Pronation – Movement that occurs when the forearm rotates medially so that the palm faces posteriorly, and the radius and ulna form an “X”

Special Types of Body Movements • Opposition – Refers to the action of the saddle joint between metacarpal 1 and the carpals; The action by which you move your thumb to touch the tips of the other fingers on the same hand • It is this unique action that makes the human hand such a fine tool for grasping and manipulating things

Types of Muscles • Muscles can’t push, they can only pull as they contract. • Most often body movements are the result of the activity of two or more muscles acting together or against each other. • Muscles are arranged in such a way that whatever one muscle can do, other muscles can reverse.

Types of Muscles • Muscles work in pairs: • Prime Mover (Agonist)– The muscle that has the major responsibility for causing a particular movement • Antagonist – Muscles that oppose or reverse a movement • When a prime mover is active, its antagonist is stretched and relaxed. • Antagonists can be movers in their own right • For example, the biceps of the arm (prime mover of elbow flexion) is antagonized by the triceps (a prime mover of elbow extension).

Types of Muscles • Synergists – Help prime movers by producing the same movement or by reducing undesirable movements • When a muscle crosses two or more joints, its contraction will cause movement in all joints crossed unless synergists are there to stabilize them. • Example – The finger-flexor muscles cross both the wrist and the finger joints. You can make a fist without bending your wrist because synergist muscles stabilize the wrist joints and allow the prime mover to act on the finger joints.

Types of Muscles • Fixators – Specialized synergists; Hold bones still or stabilize the origin of a prime mover so all the tension can be used to move the insertion bone • Examples – • The postural muscles that stabilize the vertebral column • The muscles that anchor the scapula to the thorax

Naming Skeletal Muscles • Muscles are named on the basis of several criteria: • Direction of muscle fibers • Rectus (straight) – Its fibers run parallel to that imaginary line • Oblique (slanted) – Its fibers run slanted to the imaginary line • Relative size of the muscle • Maximus (largest), Minimus (smallest), Longus (long) • For example, the gluteus maximus is the largest muscle of the gluteus muscle group

Naming Skeletal Muscles • Muscles are named on the basis of several criteria: • Location of the skull • Some muscles are named for the bone with which they are associated • For example, the temporalis and the frontalis muscles overlie the temporal and frontal bones of the skull

Naming Skeletal Muscles • Muscles are named on the basis of several criteria: • Number of origins • When the term biceps, triceps, or quadriceps forms part of a muscle name, one can assume that the muscle has 2, 3, or 4 origins, respectively. • For example, the biceps muscle of the arm has two heads, or origins, and the triceps muscle has three.

Naming Skeletal Muscles • Muscles are named on the basis of several criteria: • Location of the muscle’s origin and insertion • Occasionally, muscles are named for their attachment sites. • For example, the sternocleidomastoid muscle has its origin on the sternum (sterno) and inserts on the mastoid process of the temporal bone

Naming Skeletal Muscles • Muscles are named on the basis of several criteria: • Shape of the muscle • Some muscles have a distinctive shape that helps to identify them • For example, the deltoid muscle is roughly triangular (deltoid means triangular)

Naming Skeletal Muscles • Muscles are named on the basis of several criteria: • Action of the muscle • When muscles are named for their actions, terms such as flexor, extensor, and adductor appear in their names. • Examples - The adductor muscles of the thigh all bring about its adduction; The extensor muscles of the wrist all extend the wrist

Muscular System Notes