A&P chapts 10&11

The muscular system and contractions

The muscular system

Only consists of skeletal muscles

muscle organization and function

Muscle organization affects power, range, and speed of muscle movement

fasciles

muscle fibers arranged (organized) in bundles

Classification of skeletal muscles are by

The way fascicles are organized (direction) and by the relationships of fascicles to tendons

Organization of Skeletal Muscle Fibers- 4 patterns of fascicle organization

Parallel, convergent, pennate (feather like), circular

parallel muscles

fibers parallel to the long axis of muscle

An example of parallel muscles would be

Biceps brachii

Parallel muscles depend on

Total number of myofibrilis

convergent muscles

broad area converges on attachment site (tendon, aponeurosis, or raphe); muscle fibers pull in different directions, depending on stimulation ex: pectoralis muscles

Another word for muscle cell

Muscle fiber

pennate muscles

form an angle with the tendon

pennate muscles

Do not move as far as parallel muscles, contain more myofibrilis than parallel muscles,Develop more tension than parallel muscles

Unipennate

Fibers on one side of tendon

Bipennate

Fibers in both sided of tendon

Multipennate

tendon branches within muscle

circular muscles

Aka Sphincters

Circular muscles

Open and close to guard entrances of body

Skeletal Motion

skeletal muscles attach to skeleton, produce motion

Skeletal motion is a type of

Muscle attachment that affects power, range, and speed of muscle movement

Levers

Mechanically, each bone is a lever (a rigid, moving structure), and each joint a fulcrum (a fixed point). Muscles provide applied force (AF), required to overcome load (L)

function of a lever

To change: direction of an AF, distance and speed of movement produced by an AF, effective strength of an AF

The three classes of levers

Depend on the relationship between AF, fulcrum, and resistance

The three classes of levers are

first, second, third class levers

First class levers

Center fulcrum between AF and load.

(1st class) Force and load are

Balanced

second class lever

Center resistance between AF and fulcrum

(2nd class) small force moves

A large weight

third class leverage most common levers in the body

Third class levers

Third class levers

Center applied forced between load and fulcrum. Greater force moves smaller load. Maximizes speed and distance traveled

Origins

Muscles have one fixed point of attachment

Insertion

Muscles have one moving point of attachment

Origins and insertions

Most muscles originate or insert on the skeleton

Origin is usually \____ to insertion

proximal

Actions

movements produced by muscle contraction

Actions are described in terms of

bone, joint, or region

Muscle Interactions

Muscles work in groups to maximize efficiency
Smaller muscles reach maximum tension first, followed by larger, primary muscles

Agonist (prime mover)

produces a particular movement

Antagonist

Opposes movement of a particular agonist

Synergist

A smaller muscle that assists a larger agonist. Helps start motion or stabilize origin of agonist (fixation)

Muscle Opposition

Agonists and antagonists work in pairs
When one contracts, the other stretches. Ex: flexors-extensors, abductors-adductors

The action by a muscle @ any one joint is largely dependent on

The structure of the joint and the location of the insertion of the muscle relative to the axis movement @ the joint

The direction/geometric paths of the action produced by a muscle are called

Lines of action

Muscles whose lines of action cross the medial side of the joint are

Adductors of that joint

Muscles whose lines of action cross the lateral side of the joint are

Abductors of that joint

lateral rotator

rotates the axis of the limb away from the midline

Medial rotator

rotates the axis of the limb toward the midline

The names of skeletal muscles

* Correct names of muscles include the term muscle
* Exceptions: Platysma, Diaphragm

Descriptive names for skeletal muscles

Location in the body
Origin and insertion
Fascicle organization
Relative position
Structural characteristics
Action

Location in the body

identifies body regions

origin and insertion

first part of name indicates origin, second part of name indicates insertion

Fascicle Organization

Describes fascicle orientation within muscle

Externus (superficialis)

visible at body surface

Internus (profundus)

deep muscles

Extrinsic

muscles outside an organ

instrinsic

Muscle inside of an organ

Position includes

Externus, internus, extrinsic, intrinsic

structural characteristics include

Number of tendons, shape, size

Number of tendons

bi\=2, tri\=3

Shape

Trapezius, deltoid, rhomboid

size

Many terms refer to muscle size

Action includes

Movements, occupations or habits

Movements

Ex: flexor, extension, retractor

Occupations or habits

Ex: risor\=laughter

Terms indicating specific regions of the body

* Abdominal (abdomen)
* Ancon (elbow)
* Auricular (ear)
* Brachial (arm)
* Capitis (head)
* Carpi (wrist)
* Cervicis (neck)
* Coccygeal (coccyx)
* Costal (rib)
* Cutaneous (skin)
* Femoris (thigh)
* Glossal (tongue)
* Hallux (great toe)
* Ilium (groin)
* Inguinal (groin)
* Lumbar (lumbar region)
* Nasalis (nose)
* Nuchal (back of neck)
* Ocular (eye)
* Oris (mouth)
* Palpebra (eyelid)
* Pollex (thumb)
* Popliteal (posterior to knee)
* Psoas (loin)
* Radial (forearm)
* Scapular (scapula)
* Temporal (temple)
* Thoracic (thorax)
* Tibial (tibia;shin)
* Ulnar (ulna)

Terms indicating position, direction, or fascicle organization

-anterior (front)
-external(on the outside)
-extrinsic (outside the structure)
-inferior(below)
-intrinsic(within the structure)
-lateral(on the side)
-medial(middle)
-oblique(slanting)
-posterior(back)
-profundus(deep)
-rectus (straight)
-superficial(toward the surface)
-superior (toward the head)
-transverse (crosswise)

Terms indicating structural characteristics of the muscle

-Nature of origin
-shape
-other striking features

Shape

-Rhomboid (parallelogram)
-serratus (serrated)
-splenius (bandage)
-teres (round and long)
-trapezius (trapezoid)

Other Striking Features

Alba (white)
Brevis (short)
Gracilis (slender)
Lata (wide)
Latissimus (widest)
Longissimus (longest)
Longus (long)
Magnus (large)
Major (larger)
Maximus (largest)
Minimus (smallest)
Minor (smaller)
Vastus (great)

General

Abductor (movement away)
Adductor (movement toward)
Depressor (lowering movement)
Extensor (straightening movement)
Flexor (bending movement)
Levator (raising movement)
Pronator (turning to prone position)
Supinator (turning into supine position)
Tensor (tensing movement)

Specific

Buccinator (trumpeter)
Risorius (laughter)
Sartorius (like a tailor)

Divisions of the Muscular System

Axial muscles and appendicular muscles

axial muscles

position head and spinal column; move rib cage; 60% of skeletal muscles

appendicular muscles

Support pectoral and pelvic girdles
Support limbs
40% of skeletal muscles

The axial muscles

Divisions based in location and function

The axial muscles

Muscles of the head and neck
Muscles of the spine
Muscles of the trunk
Muscles of the pelvic floor

muscles of facial expression

originate on skull

extrinsic eye muscles

Originate on the surface of the orbit and control the position of the eye

muscles of mastication

move the mandible

Muscles of the tongue

names end in glossus

Muscles of the Pharynx

begin swallowing process

anterior muscles of the neck

-control position of larynx
-depress the mandible
-support tongue and pharynx

orbicularis oris

constricts the mouth opening

Buccinnator

Moves food around the cheeks

Muscles of the epicranium (scalp)

Temporoparietalis
Occipitofrontalis

Temporoparietalis and occipitofrontalis

Frontal and occipital bellies
Separated by epicranial aponeurosis

Platysma

covers anterior surface of neck

Six extrinsic eye muscles

superior rectus, inferior rectus, lateral rectus, medial rectus, superior oblique, inferior oblique

muscles of mastication

masseter, temporalis, pterygoid muscles

Masseter

strongest jaw muscle

Temporalisis

Helps lift the mandible

pterygoid muscles

positions mandible for chewing

Muscles of the tongue

\-All named for origin and insertion

•Palatoglossus

•Styloglossus

•Genioglossus

•hyoglossus

The Control of Skeletal Muscle Activity

• **The neuromuscular junction (NMJ)**
• Special intercellular connection between the nervous system and skeletal muscle fiber
• Controls calcium ion release into the sarcoplasm

A single axon may branch to control more than one skeletal muscle fiber, but

each muscle fiber has only one neuromuscular junction (NMJ).

At the NMJ, the axon terminal of the neuron lies near the

motor end plate of the muscle fiber.

Acetylcholine is a

neurotransmitter

neurotransmitter

a chemical released by a neuron to change the permeability or other properties of another cell’s plasma membrane

synaptic cleft

a narrow space that separates the axon terminal of the neuron from the opposing motor end plate.

The stimulus for ACh release is the arrival of an

electrical impulse, or action potential, at the axon terminal.

An action potential is a

sudden change in the membrane potential that travels along the length of the axon.