the muscular system - rcboe.org · for body movements, stabilizing joints, and generating heat. how...

The Muscular System

WHAT

Muscles are responsible

for body movements,

stabilizing joints, and

generating heat.

HOW

Muscles generate the force

required to cause movement

by contracting, a process in

which proteins inside the

muscle fibers overlap more

than when they are at rest.

WHYIn addition to whole body

movements, muscles are needed

to move substances inside our

bodies: for example, air into and

out of our lungs, food through

our digestive tracts, and blood

through our heart and blood

vessels.

OVERVIEW OF

MUSCLE TISSUESThere are three types of muscle

tissue: skeletal, smooth and

cardiac

These differ in their cell structure,

body location, and how they are

stimulated to contract.

- Skeletal and smooth muscle cells

are elongated

- the ability of muscle to shorten or

contract

- myo- or mys- or sarco- terminology

HOW ARE THEY

SIMILAR?

Packaged into organs called

skeletal muscles that attach

to the skeleton.

SKELETAL

MUSCLE FIBERS

- Large, cigar-shaped,

multinucleate cells.

- Largest muscle fibers

SKELETAL

MUSCLE FIBERS

Also known as:

Striated Muscle

Because its fibers have

obvious stripes

Voluntary Muscle

Because only muscle type

subject to voluntary control

SKELETAL

MUSCLE FIBERS

VOCABULARY

ENDOMYSIUMA delicate connective tissue sheath

that encloses each muscle fiber

VOCABULARY

PERIMYSIUMCoarser fibrous membrane

that wraps several sheathed

muscle fibers

VOCABULARY

FASCICLEA bundle of fibers

VOCABULARY

EPIMYSIUMTough "overcoat" of

connective tissue that binds

many fascicles together;

covers the entire muscle

The ends of the epimysium which

extend beyond the muscle blend

either into a strong, cordlike tendon

or a sheet-like aponeurosis

TENDON OR

APONEUROSIS

Functions:

- anchoring muscles

- providing durability

- conserving space

TENDON

WORKSHEETLabel the skeletal muscle diagram

and color it

Ticket Out The DoorName two tendons in the body

besides the Achiles tendon

- Has no striations

- Involuntary

- Found mainly in the walls of

hollow visceral organs (stomach,

Urinary bladder, respiratory

passages

SMOOTH

MUSCLE

Propels substances along a

pathway

SMOOTH

MUSCLE

Fibers are:

- spindle shaped

- uni-nucleate

- scant endomysium

- two layers, one running circularly

and one running longitudinally

SMOOTH

MUSCLE

Moving food through the digestive

tract and emptying the bowels and

bladder are examples of activities

normally handled by smooth

muscles

SMOOTH

MUSCLE

Smooth muscle contractions are

slow and sustained

SMOOTH

MUSCLE

Found only the heart, where it

forms the bulk of the heart walls

CARDIAC MUSCLE

- Striated

- Uninucleated

- Involuntary

CARDIAC MUSCLE

Cushioned by small amounts of

endomysium and are arranged in

spiral or figure-8-shaped bundles

CARDIAC MUSCLE

Fibers are branching cells joined by

special gap junctions called

intercalated discs

CARDIAC MUSCLE

These two structural features and

the spiral arrangement of the

muscle bundles in the heart allow

heart activity to be closely

coordinated

CARDIAC MUSCLE

CHART

Ticket Out The DoorWhat is the meaning of epi? Of mys? How do

these word roots relate to the role and

position of the epimysium?

CHARACTERISTIC SKELETAL CARDIAC SMOOTH

BODY LOCATION

CELL SHAPE & APPEARANCE

VOLUNTARY/INVOLUNTARY

1. Produce movement

MUSCLE FUNCTIONS

Skeletal muscles are

responsible for our body's

mobility, including all

locomotion

2. Maintain posture

and body position

MUSCLE FUNCTIONS

3. Stabilize joints

MUSCLE FUNCTIONS

Muscles and tendons are

extremely important in

reinforcing and stabilizing

joints that have poorly

articulating surfaces

4. Generate Heat

MUSCLE FUNCTIONS

Muscle activity generates body

heat as a by-product; skeletal

muscle accounts for at least 40%

of body mass, so it is the muscle

type most responsible for

generating heat.

MICROSCOPIC ANATOMY

OF SKELETAL MUSCLE

Multinucleate

Nucleus

Nucleus

Nucleus

Plasma membrane

of muscle fibers

SARCOLEMMA

Contractile

organelles found in

the cytoplasm of

muscle cells

MYOFIBRILS

LIGHT (I) BANDS

DARK (A) BANDS

SARCOMERESContractile units

that are the

structural and

functional units

of skeletal

muscle

THICK FILAMENTSMyofilaments in sarcomere made up of

myosin. Extend the entire length of dark

band

THIN FILAMENTSMyofilaments in sarcomere made up of

actin. Anchored to the z-disc

SARCOPLASMIC

RETICULUMSpecialized smooth endoplasmic reticulum.

Major role is to store calcium and to release

it on demand when the muscle fiber is

stimulated to contract.

SKELETAL MUSCLE

ACTIVITYSTIMULATION AND CONTRACTION OF

SINGLE SKELETAL MUSCLE FIBERS

SKELETAL MUSCLE

ACTIVITYMuscle fibers have several special

functional properties that enable them to

perform their duties.

#1. Irritability

The ability to receive and respond to a

stimulus

#2. Contractility

The ability to forcibly shorten when

adequately stimulated

#3. Extensibility

The ability of muscle fibers to stretch

#4. Elasticity

The ability to recoil and resume

their resting length after being

stretched

THE NERVE STIMULUS

AND THE ACTION

POTENTIALTo contract, skeletal muscle

fibers must be stimulated by

nerve impulses.

One motor neuron (nerve cell) may

stimulate a few muscle fibers or

hundreds of them, depending on

the particular muscle and the

work it does

VOCABULARY

MOTOR UNITConsists of one neuron and all the skeletal muscle fibers it stimulates.

VOCABULARY

AXONLong, thread-like extension of the neuron

VOCABULARY

AXONTERMINALSAxon branches into multiple terminals that interface with the muscle fiber

VOCABULARY

Neuromuscular JunctionsThe union of axon terminals and the muscle

VOCABULARY

NeurotransmitterA chemical that stimulates a response in another tissue. In this case, acetylcholine (Ach) stimulates muscle tissues

VOCABULARY

Synaptic CleftThe space between the axon terminal and the muscle sarcolemma; it is filled with interstitial fluid

Steps of an Action Potential

Nerve impulse reaches axon terminal of motor neuron#1


Calcium (Ca2+) channels open, and Ca2+ enters the axon terminal

#2


Ca2+ entry causes some synaptic vesicles to release their contents (the neurotransmitter acetylcholine) by exocytosis

#3


Acetylcholine diffuses across the synaptic cleft and binds to receptors in the sarcolemma

#4


ACh binds and opens channels that allow simultaneous passage of Na+ into the muscle fiber and K+ out of the muscle fiber. More Na+ ions enter than K+ ions leave, causing depolarization. This eventually leads to an action potential.

#5


The enzyme acetylcholinesterase breaks down ACh in the synaptic cleft, ending the process.

#6

MAKE A GAME!Steps? Chemicals? Anatomy?

SLIDING FILAMENT THEORY

What causes muscle contractions?

- Myosin (thick filaments) and Actin (thin filaments) slide along each other- This occurs when "cross-bridges" are formed by Myosin heads attaching to Actin

CONTRACTION OF A SKELETAL MUSCLE AS A WHOLE

GRADED RESPONSES

- Different degrees of shortening which generate different amounts of force

CONTRACTION OF A SKELETAL MUSCLE AS A WHOLE

GRADED MUSCLE CONTRACTIONS CAN BE PRODUCED TWO WAYS

1. by changing the frequency of muscle stimulation2. by changing the number of muscle fibers being stimulated at one time

MUSCLE RESPONSE TO INCREASINGLY RAPID STIMULATION

MUSCLE TWITCHES

Single, brief, jerky contractions


Usually nerve impulses are delivered to the muscle at a very rapid rate, so fast that the muscle does not get a change to relax completely between stimuli


As a result, the effects of the successive contractions are "summed" (Added) together and the contractions of the muscle get stronger and smoother.

INCOMPLETE TETANUS


The muscle is stimulated so rapidly that no evidence of relaxation is seen and the contractions are completely smooth and sustained

COMPLETE TETANUS

MUSCLE RESPONSE TO STRONGER STIMULI

How forcefully a muscle contracts depends on how many of its cells are stimulated

MUSCLE RESPONSE TO STRONGER STIMULI

- only a few cells are stimulated and the muscle contracts only slightly- when all the motor units are active and all the muscle fibers are stimulated the muscle contraction is as strong as it can get

PROVIDING ENERGY FOR MUSCLE CONTRACTION

#1. Direct phosphorylation of ADP by creatine phosphate


#2. Aerobic pathway


#3. Anaerobic glycolysis and lactic acid formation

MUSCLE MOVEMENTS, ROLES AND NAMES

ORIGIN

End of a muscle that is attached to the immoveable or less moveable bone


INSERTION

Attached to the moveable bone.


FLEXIONDecreases the angle of the joint and brings two bones closer together.


EXTENSIONIncreases the angle between two bones or parts of the body


ROTATIONA movement of a bone around its longitudinal axis


ABDUCTION

Moving a limb away from the midline of the body


ADDUCTION

Movement of a limb toward the body midline


CIRCUMDUCTION

A combination of flexion, extension, abduction and adduction


DORSIFLEXION

Lifting the foot so that its superior surface approaches the shin


PLANTAR FLEXION

Pointing the toes away from your head


INVERSION

Turning the sole of the foot medially


EVERSION

Turning the sole of the foot laterally


SUPINATION

Forearm rotates laterally so the palm faces up


PRONATION

Forearm rotates medially so the palm faces down


OPPOSITION

Moving your thumb to touch the tips of other fingers on the same hand

QUIZ TUESDAY OVER MOVEMENTS

INTERACTIONS OF SKELETAL MUSCLES IN THE BODY

PRIME MOVER

The muscle that has the major responsibility for causing a particular movement


Muscles can only pull, so most often body movements result from two or more muscles acting together or against each other. Muscles are arranged so that whatever one muscle can do, other muscles can reverse.


Because of this arrangement, muscles are able to bring about an immense variety of movements


ANTAGONISTS

Muscles that oppose or reverse a movement


SYNERGISTS

Help prime movers by producing the same movement or by reducing undesirable movements


FIXATORS

Specialized synergists; they hold a bone still or stabilize the origin of a prime mover so all the tension can be used to move the insertion bone

NAMING SKELETAL MUSCLES

DIRECTION OF THE MUSCLE FIBERS

- RECTUS – fibers run parallel to some line- OBLIQUE – fibers run obliquely (at a slant) to the imaginary line


RELATIVE SIZE OF THE MUSCLE

- MAXIMUS – largest- MINIMUS – smallest- LONGUS - long


LOCATION OF THE MUSCLE

- some are named for the bone with which they are associated


NUMBER OF ORIGINS

- biceps, triceps, or quadriceps


LOCATION OF THE MUSCLE'S ORIGIN AND INSERTION

- occasionally, muscles are named for their attachment site. Ex. Sternocleidomastoid muscle


SHAPE OF THE MUSCLE

- some muscles have a distinctive shape that helps to identify them. Ex. Deltoid is roughly triangular


ACTION OF THE MUSCLE

- When muscles are named for their actions, terms such as flexor, extensor, and adductor appear in their names

COURSEWORK

BASED ON THEIR NAMES, DEDUCE SOME CHARACTERISTICS OF THE FOLLOWING MUSCLES:- tibialis anterior- erector spinae- rectus abdominis- extensor carpi radialis longus

BELLRINGERA skeletal muscle is attached to bones at two points. Name each of these attachment points, and indicate which is movable and which is immovable.

ARRANGEMENT OF FASCICLES

Skeletal muscles consist of fascicles, but fascicle arrangements vary, producing muscles with different structures and functional properties


CIRCULAR – the fascicles are arranged in concentric rings


CONVERGENT – the fascicles converge toward a single insertion tendon


PARALLEL – the length of the fascicles run parallel to the long axis of the muscle


FUSIFORM – a modification of the parallel arrangement; results in a spindle-shaped muscle with an expanded belly


PENNATE – short fascicles attached obliquely to a central tendon.UNIPENNATE - the fascicles insert into only one side of the tendon


BIPENNATE - fascicles insert into opposite sides of the tendon


MULTIPENNATE - fascicles insert from several different sides

COURSEWORK

NAME TWO DIFFERENT MUSCLES FOR EACH TYPE OF FASCICLE ARRANGEMENT

BELLRINGERName the eight fascicle arrangements and list two places where circular fascicle arrangements can be found.

HEAD AND NECK MUSCLES

The head muscles are an interesting group. They have many specific functions but are usually grouped into two large categories – facial muscles and chewing muscles.Facial muscles are unique because they insert into soft tissues like other muscles or skin.

FACIAL MUSCLES

FRONTALIS- runs from the

cranial aponeurosis to the skin of the eyebrows where it inserts. Allows you to raise your eyebrows and to wrinkle your forehead.

FACIAL MUSCLES

ORBICULARIS OCULI- The fibers of this muscle run in circles around the eyes. Allows you to close your eyes, squint, blink, and wink.

FACIAL MUSCLES

ORBICULARIS ORIS- The circular muscle of the lips. Often called the kissing muscle, it closes the mouth and protrudes the lips.

FACIAL MUSCLES

BUCCINATOR- runs horizontally across the cheek and inserts into the orbicularis oris. Flattens the cheek as in whistling. Also listed as a chewing muscle because it compresses the cheek to hold food between the teeth during chewing.

FACIAL MUSCLES

ZYGOMATICUS- extends from the corner of the mouth to the cheekbone. Often referred to as the smiling muscle because it raises the corners of the mouth.

FACIAL MUSCLES

MASSETER- As it runs from the zygomatic process of the temporal bone to the mandible, the masseter covers the angle of the lower jaw. Closes the jaw by elevating the mandible.

FACIAL MUSCLES

TEMPORALIS- Fan-shaped muscle overlying the temporal bone. Inserts into the mandible and acts as a synergist of the masseter in closing the jaw.

NECK MUSCLES

PLATYSMA- single sheetlike muscle that covers the anterolateral neck. Originates from the connective tissue covering of the chest muscles and inserts into the area around the mouth. Its action is to pull the corners of the mouth inferiorly, producing a downward sag of the mouth.

NECK MUSCLES

STERNOCLEIDOMASTOID- two headed muscles, one found on each side of the neck. One arises from the sternum and the other from the clavicle; used to flex the neck, bowing the head.

QUIZ TOMORROW ON FACIAL AND NECK MUSCLES

BELLRINGER1. Which muscle is called the kissing muscle?2. Which muscle is used for smiling?3. Which muscle is used to wrinkle the forehead?

TRUNK MUSCLES

Include:1. Muscles that move the vertebral column (most of which are posterior antigravity muscles)2. Anterior thorax muscles which move the ribs, head, and arms3. Muscles of the abdominal wall, which "hold your guts in" by forming a natural girdle and help to move the vertebral column.

ANTERIOR TRUNK MUSCLES

Pectoralis Major- a large fan-shaped muscle covering the upper part of the chest. Its origin is from the sternum, shoulder girdle, and the first six ribs. It inserts on the proximal end of the humerus. This muscle forms the anterior wall of the axilla (armpit) and acts to adduct and flex the arm.

ANTERIOR TRUNK MUSCLES

Intercostal Muscles- Deep muscles found between the ribs. External intercostals are important in breathing because they help to raise the ribcage when inhaling. Internal intercostals depress the rib cage helping to move air out of the lungs.

MUSCLES OF THE ABDOMINAL GIRDLE

Rectus abdominis- Most superficial muscles of the abdomen. Run from the pubis to ribcage. Main function is to flex the vertebral column.


External Oblique- Paired superficial muscles that make up the lateral walls of the abdomen. Flex vertebral column, rotate the trunk and bend it laterally.


Internal Oblique- Paired muscles deep to the External Oblique. Same function as External Oblique.


Transversus Abdominis- Deepest muscle of the abdominal wall. Arises from the lower ribs and iliac crest and inserts into the pubis. Compresses the abdominal contents

POSTERIOR TRUNK MUSCLES

Trapezius- Most superficial muscles of the posterior neck and upper trunk. Extend the head and elevate, depress, adduct and stabilize the scapula.


Latissimus Dorsi- two large, flat muscles that cover the lower back. Originate in lower spine and ilium and insert into proximal end of humerus. Extends and adducts the humerus.


Erector Spinae- Prime mover of back extension.


Quadratus Lumborum- form part of the posterior abdominal wall. Flexes and extends the lumbar spine.


Deltoid- fleshy, triangle-shaped muscles that form the rounded shape of the shoulders. Prime movers of arm abduction.

the muscular system - rcboe.org · for body movements, stabilizing joints, and generating heat. how...

Documents