muscularsystem.ppt

IV. Vocabulary

A. Origin

-Attachment of muscle to stationary bone B. Insertion

-Attachment of a tendon to a moveable bone C. Belly

-Fleshy portion of the muscle D. Prime mover (agonist)

IV. Vocabulary, cont.

F. Synergists

- group of muscles that help the agonist G. Fixators

Naming of Skeletal Muscles (added to pg. 39 orange book)

A. Direction – rectus means straight. Ex: Rectus femoris,

Transverse abdominis

B. Relative Size – maximus =

largest, minimus = smallest, longus = long, brevis = short. Ex: Gluteus

maximus & minimus, Peroneus longus (lateral side of the lower leg)

D. Number of Origins – Ex: Biceps (two heads of shoulder girdle), Triceps

(one on head of shoulder & 2 on humerus), Quadriceps (anterior thigh)

E. Location of Origin & Insertion – named for the muscle’s attachment site. Ex: Sternocleidomastoid – origin on sternum & clavicle, insertion on

Examples:

Movement – flexion of the forearm

PM – Biceps brachii Ant – Triceps brachii

I.

Muscles that move the head

(this is the only one we will study – orange bk pg.36)

A. Sternocleidomastoid (anterior and

superficial)

1. Origins – sternum and clavicle

2. Insertion – mastoid process

Neck and Torso Muscles

I. Abdominal Wall A. Rectus

abdominis (super) 1. Origin –

symphysis pubis 2. Insertion –

xiphoid

3. Action –

Neck and Torso muscles

B. External abdominal oblique (super)

1. Origin – ribs

2. Insertion – iliac crest

3. Action – compresses

Neck and Torso muscles

C. Internal abdominal oblique (deep)

1. Origin – iliac crest 2. Insertion – ribs

Neck and Torso muscles

D. Transverse abdominis

1. Origin – costal cartilage

II. Muscles that aid in breathing

A. Diaphragm (deep)

1. Origin – ribs, sternum, and vertebral column

2. Insertion- tendon of diaphragm

Muscles that aid in breathing

B. External Intercostals (deep)

1. Origin – rib 2. Insertion – rib

Muscles that aid in breathing

C. Internal Intercostals (deep)

1. Origin – ribs 2. Insertion – ribs

IV. Muscles that move the arm

A. Pectoralis major (anterior and

superficial)

1. Origin - clavicle and sternum

2. Insertion- humerus

B. Latissimus dorsi (posterior &

superficial)

1. Origin – vertebral column & iliac

2. Insertion – humerus

C. Deltoid

1. Origin – clavicle & scapula

2. Insertion – humerus

D. Teres major

1. Origin – scapula

2. Insertion – humerus

E. Subscapularis (deep – rotator cuff)

1. Origin – scapula 2. Insertion –

humerus

F. Infraspinatus

1. Origin – scapula 2. Insertion –

humerus

G. Supraspinatus

1. Origin – scapula 2. Insertion –

humerus

H. Teres minor ( deep – rotator cuff)

1. Origin – scapula 2. Insertion –

humerus

III. Muscles acting on scapula

A. Subclavius

1. Origin – rib

2. Insertion – scapula 3. Action – depress

B. Pectoralis minor (deep, anterior) 1. Origin – ribs

C. Serratus anterior 1. Origin – ribs

D. Trapezius (posterior, superficial)

1. Origin – occipital protrudance &

vertebral column

2. Insertion – clavicle and scapula

E. Levator scapulae (posterior, deep)

1. Origin – vertebral column

F. Rhomboideus Major 1. Origin – vertebral column

G. Rhomboideus minor 1. Origin – vertebral column

MUSCULAR SYSTEM

Overview Function –

- Movement of the body created by contraction and relaxation of muscles. Also generate heat.

- Muscles comprise 40-50% of entire body weight.

I. Types of Muscular Tissue

A. Skeletal – striated or voluntary

1. 40-50% of body weight (red meat) 2. microscopic stripes or striations are visible (multinucleated)

3. contractions voluntarily controlled via nervous system

B. Cardiac – heart muscle

1. cells branch frequently (uninucleate) 2. contain dark bands known as intercalated disks

3. cells are interconnected allowing for contraction as a unit

4. both the nervous system and hormones control the speed of

C. Nonstriated, involuntary, SMOOTH, or visceral

1. absence of stripes or striations

2. cells are fusiform (spindle-shaped, tapering toward the ends) and

uninucleate

3. located in the walls of hollow visceral structures: digestive tract, blood

vessels, and ureters

II. Function of muscle tissue

A. Motion – refers to the body being in

motion.

1. Gross movements – moving arms and legs

B. Movement – refers to the use of involuntary muscle tissue

1. Heart contractions

C. Stabilizing body positions and organ volume.

1. Muscles that give the body posture. 2. Organs ability to store food.

D. Heat production

1. Heat is a byproduct of the muscle contraction reaction.

III. Characteristics of muscle tissue

A. Excitability

- ability to receive and react to stimulus B. Contractility

- ability to shorten and thicken C. Extensibility

Muscle Tissue Histology

I. Skeletal Muscle Tissue

A. Connective tissue components

1. Fascia – sheet of fibrous connective tissue beneath skin or around muscles. Can be deep or superficial.

2. Epimysium – covering around the entire muscle.

4. Endomysium – covering around each individual muscle fiber.

5. Tendon – attaches muscle and bone. Extension of the epimysium, perimysium, and the

B. Nerve and blood supply

 _{The major characteristic of skeletal muscle}

is contraction.

 _{Muscle contractions require large amounts}

of oxygen, energy, and nutrients.

1. Muscle action potential – an electrical

signal that causes muscle to contract. The signal is delivered by a nerve cell

2. Artery – delivers blood to the muscle. Each muscle fiber makes two or three

connections at a capillary; this is how the muscle gets oxygen.

C. Basic Histology

1. Sarcolemma – plasma membrane of the muscle cell.

2. Sarcoplasm – cytoplasm of muscle cell

3. Sarcoplasmic reticulum – the endoplasmic reticulum of the muscle cell

4. Nucleus – skeletal muscle is multinucleated 5. Mitochondria – skeletal muscle tissue

contain a very large number

D. Advanced Histology

1. Myofibrils –

cylindrical structure that make up

muscle fibers a. Thin – called actin

2. Sarcomere – compartments that contain the myofilaments

3. Z-discs – areas that separate the sarcomeres.

4. A-band – darker band of muscle tissue, composed mostly of the thick filament (myosin)

5. H-zone – area in the center of A-band, consists of only myosin

II. Cardiac Muscle Tissue

• The appearance is similar to skeletal • Involuntary

A. Histology

1. Nucleus – each cell has one; centrally located

1. Muscle fibers

a. Shorter than skeletal b. Thicker than skeletal c. Squarish, not circular

B. Processes of the heart

1. Two networks of the heart

a. Muscular wall and the partition of the upper chambers b. Muscular wall and

2. Normal Heart Rhythm

a. 75 beats/min

- because of this constant

contraction/relaxatio n rhythm, the

III. Smooth muscle Tissue

 Involuntary

 Thicker and smaller than skeletal muscle tissue

 Fibers are tapered A. Histology

1. Myofilaments – no regular pattern; so it appears non-striated

2. Dense bodies – much like z-disc; serves as separation point

B. Types of smooth muscle

1. Visceral (most common)

a. Form – wraparound sheets of small arteries and veins, hollow viscera such as stomach, intestines, uterus, urinary bladder

2. Multiunit

a. Forms – single fibers found in wall of large arteries, in large airways to lungs, and internal eye muscles

b. Contraction – contraction of the single fiber

c. Differences to striated muscles

Histology: Contraction of Skeletal

Muscle

I. Neuromuscular Junction

- This is where the nerve meets the

muscle; muscles are stimulated by nerves. A. Motor Unit – is composed of

1. Motor Neuron – type of neuron that stimulates muscle tissue

B. A closer look at the junction

• The actual axon of the motor neuron doesn’t touch the sarcolemma of the muscle fiber. The gap is

called the synaptic cleft.synaptic cleft.

1. Axon terminal – end of the axon gets close to the sarcolemma

2. Motor end plate – sarcolemma closest to the axon

3. Synaptic end bulb – portion of the axon that swells at the end

Synaptic end bulb

C. Physiology

• When a nerve impulse reaches the synaptic end bulb, Ca2+ triggers the

release of Acetylcholine (Ach), the neurotransmitter

• Ach binds with the Ach receptors on the sarcolemma

• This deals with the interaction between the actin and myosin myofilaments

• For this mechanism to work there needs to be adequate Ca2+ and energy

A. Myosin

1. Head – also called cross bridges, pulls on thin filaments

B. Sarcomere

1. The sliding of the myofilaments brings the z-discs closer together

2. The myosin can pull the thin filaments so far inward that they overlap

III. Contraction of the Muscle A. Energy for contraction

2. ATP →ADP + P + energy

3. When creatine phosphate is depleted,

glucose is broken down through processes called glycolysis and cellular respiration

and ATP is made

B. Stimulus

1. Threshold stimulus – any stimulus that causes a contraction

C. Physiology

• When a muscle fiber is relaxed, there is low concentration of Ca2+ in the sarcoplasm it is held in the sarcoplasmic reticulum

(SpR)

• When a muscle fiber is contracted the SpR releases Ca2+ in to

D. Relaxation (2 major changes)

• Ach is broken down by acetylcholinase (AChE), this stops the muscle action

potentials.

• Ca2+ is rapidly removed from the

sarcoplasm and returned to the SpR. This stops the myosin head from attaching to

IV. Kinds of contractions

• Myogram – measurement of a muscle

contraction

–Latent – when Ca2+ released

–Contraction – when muscle contracts

–Relaxation – when muscle is relaxing

• After a muscle fiber contracts, there is a short period of time that it loses its excitability

A. Twitch – brief contraction of all the muscle fibers in a motor unit.

B. Tetanus – two stimuli are applied but the second one is delayed until after the

refractory period.

• D. Isometric –

minimal shortening of muscle; tension is

Steps of Sliding filament sequence

• Myosin head becomes activated as it splits ATP into ADP + phosphate using ATPase

• Ca2+ enters the sarcoplasm from the SpR,

binding to troponin and moving the tropomyosin • The activated myosin can attach to exposed

actin filaments

• When power stroke is complete ATP binds to the myosin head and it detaches from

actin

• ATP splits and returns the myosin head to original position

II. Microscopic Structure

A. Each muscle cell is referred to as a contractile cell or fiber, grouped into sausages

C. Basic functional (contractile) unit is called a sarcomere; sarcomeres are separated from each other by dark bands called Z-lines

- Sliding filament model is used to explain the mechanism of contraction

III. Skeletal Muscle Structure

A. Each skeletal muscle is an organ composed mainly of skeletal muscle cells and connective tissue

- endomysium – encloses each muscle cell (fiber)

- perimysium – wraps several fibers, making a fascicle

B. Most skeletal muscles extend from one bone across a joint to another bone

C. Parts

1. Origin – attachment to the bone that

remains relatively stationary or fixed

when joint movement occurs

2. Insertion – point of attachment to the

bone that moves when a muscle

contracts

D. Muscles attach to bone with

tendons (which are formed from the epimysium connective tissue that binds the underlying fascicles together)

V. Functions of Skeletal Muscles

A. Movement – involves pulling the insertion bone closer to the origin bone. Actual

movement occurs at the joint and involves groups of muscles to produce a single

movement

1. Prime mover – muscle whose contraction is mainly responsible for producing a given movement

2. Synergist – muscle whose contractions help the prime mover (fixators)

B. Posture – a specialized type of muscle

contraction, called tonic contraction (“muscle tone”), enables us to maintain body position

1. only a few of the muscle’s fibers shorten at one time

2. produces no movement of body parts

a. good posture reduces strain on muscles, tendons, ligaments, & bones

b. poor posture causes fatigue and may lead to deformity

C. Heat Production – survival depends on the body’s ability to maintain a constant body

temperature. Contraction of muscle fibers produces the heat required to maintain a normal body

VI. Muscle Fatigue – reduced strength of muscle contractions

A. caused by repeated muscle stimulation

without adequate periods of rest

B. repeated muscular contraction depletes

cellular ATP stores and outstrips the ability of the blood to replenish oxygen & nutrients

C. contraction in the absence of adequate

oxygen produces lactic acid, which contributes to muscle soreness

D. Oxygen debt – term used to describe the metabolic effort required to burn excess lactic

VII. Muscle Stimulus – stimulation of a muscle by a nerve impulse is required before a muscle can shorten and produce movement

A. Structures making up a motor unit:

1. motor neuron – specialized nerve

that transmits impulse to a muscle causing

contraction

2. neuromuscular junction – specialized

point of contact between a nerve ending

and the fiber it innervates

3. synaptic cleft – gap between a nerve

B. Process of Stimulation

1. A muscle will only contract if stimulation

reaches the threshold stimulus; different muscle fibers have different thresholds.

2. The neurotransmitter acetylcholine (ACh) is released into the synaptic cleft.

3. If enough ACh is released, the sarcolemma becomes permeable to sodium ions (Na+) and they

rush into the muscle cell. This upsets the

electrical conditions and produces an action potential which travels from one end of the cell to the other.

4. The action potential causes the muscle fiber to contract completely, a response referred to as all or none.

VIII.

Types of Skeletal Contractions

A.

Twitch – a single contraction of

a muscle fiber caused by a

single

threshold stimulus

(laboratory

phenomena – not

the way our

muscles normally

operate)

B.

Tetanic (tetanus) – sustained

smooth and steady

contractions

caused by a series of stimuli

bombarding a

muscle in rapid

C. Isotonic

1. Contraction that produces muscle

movement at a joint

2. Muscle shortens, insertion moves

toward the origin

3. Most body movements such as walking and running

D. Isometric

1. Contractions do not produce

movement

Muscles of the Head

• We will study the muscles of the head in three groups: The muscles of facial

I. Muscles of facial expressions

A. Frontalis

1. Origin: frontal bone

2. Insertion: skin above eyes

B. Orbicular oris

1. Origin: maxilla and mandible

2. Insertion: other lip muscles

3. Action: close lips, make lips

C. Zygomaticus major

1. Origin: zygomatic bone 2. Insertion: angle of the mouth

3. Action: elevates upper lip (smiling)

D. Buccinator

1. Origin: mandible and maxilla

2. Insertion: angle of mouth 3. Action: retract angle of

E. Platysma

1. Origin: deltoid and pectoralis major

2. Insertion: skin on mandible

3. Action: pouting and depresses mandible; depress lower lip

F. Orbicula occuli

1. Origin: frontal bone 2. Insertion: maxilla & frontal bone

G. Levator palpebrae superioris

1. Origin – Lesser wing of sphenoid 2. Insertion –

eyelid

3. Action –

H. Depressor anguli oris

1. Origin – mandible

2. Insertion – lip

I. Levator anguli oris

1. Origin – maxilla 2. Insertion – skin at angle of mouth 3. Action –

II. Muscles that move the mandible

*Also known as muscles of

mastication

A. Masseter 1. Origin –

zygomatic arch 2. Insertion – mandible

3. Action – Elevates, protracts, and

B. Temporalis

1. Origin – temporal bone

2. Insertion – mandible

III. Muscles that move the Eye

• These muscles are extrinsic muscles of the eye (on the

outside of the eyeball)

A. Superior rectus

1. Action: rotates the eye upward and

B. Inferior rectus

Action – rotates the eye downward and to the side of the head

C. Lateral rectus

D. Medial rectus

Action – adducts eye

E. Superior oblique

Action – rotates the eye downward and

F. Inferior oblique

Action – rotates the eye upwards and