Biol 3455 Intro to Muscular System

Muscular System

organ system that allows body to move, maintain posture, circulate blood

• consists only of skeletal muscles

How is movement brought in muscular system

muscles working with/against each other

What affects power, range, and speed of movement

muscle organization

How are skeletal muscles named

• muscle location

• muscle shape

• muscle size

• Direction of muscle fibers

• # of origins

• Location of the attachments

• muscle action

Muscle fibers form bundles

fascicles

Parallel Muscles

• fascicles r parallel to long axis of muscle

• when parallel muscle contracts, it shortens and gets larger in diameter

• spindle shaped with a central body

What is attached at the origin and insertion point of parallel muscle

aponeuroses (Flat Bands)

Convergent Muscles

Muscle Fascicles extending over a broad area come together, or converge, on a common attachment site

• muscle may pull on a tendon or a slender band of collagen fibers known as a raphe

Pennate Muscles

fasicles form a common angle with tendon

• muscle fibers pull at an angle relative to tendon

How does Pennate Muscles compare with parallel muscles

• do not move their tendons as far

• contain more muscle fibers > more myofibrils

• develop more tension

3 types of Pennate Muscles

1. Unipennate Muscle

2. Bipennate Muscle

3. Multipennate Muscle

Unipennate Muscle

all muscle fibers on the same side of the tendon

Bipennate Muscles

Muscle Fibers on both sides of the tendon

Multipennate

tendons branches within muscle

Circular Muscles (Sphincters)

• fascicles are concentrically arranged around an opening

• act as valves in digestive and urinary tracts

• surround body openings and hollow organs

• contraction makes diameter of opening smaller

Lever

Simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or fulcrum

• amplifies an input force to provide a greater output

  force, which is said to provide leverage, which is mechanical

  advantage gained in the system, equal to the ratio of the output

  force to the input force.

Fulcrum

lever is a rigid structure—such as a board, a crowbar, or a bone—that moves on a fixed point

• joint

Applied Force

sufficient to overcome any load that would otherwise oppose or prevent such

movement.

What do Levers change

(1) The direction of an applied force. ▪

(2) The distance and speed of movement produced by an applied force. ▪

(3) The effective strength of an applied force.

How are levers classified

based on these 3 elements

1. applied force

2. fulcrum

3. load

Mechanical Advantage

applied force is farther from the fulcrum than the load.

Mechanical Disadvantage

applied force is closer to the load than the fulcrum.

First-Class lever

fulcrum lies btwn Applied force and Load

Second-class lever

load is btwn AF a Fulcrum

Third Lever

Applied Force is between Load and Fulcrum

Origin of muscle

less movable end

Proximal end

Insertion of the Muscle

More movable end

distal end

Examples of connective tissue sheaths that originate at Muscles

▪ Intermuscular septa (components of the deep fascia that may separate adjacent skeletal muscles).

▪ Tendinous inscriptions that join muscle fibers to form long muscles such as the rectus abdominis

▪ The interosseous membranes of the forearm or leg.

▪ The fibrous sheet that spans the obturator foramen of the pelvis.

Different muscle movements

• Flexion or extension.

▪ Adduction or abduction.

▪ Protraction or retraction.

▪ Elevation or depression

▪ Rotation or circumduction.

▪ Pronation or supination.

▪ Inversion or eversion.

▪ lateral flexion, opposition, or reposition