The Muscular System · Contraction of a Skeletal Muscle Fiber Figure 7-3 (1 of 2) Anatomy of...

Essentials of Anatomy & Physiology, 4th EditionMartini / Bartholomew

PowerPoint® Lecture Outlines

prepared by Alan Magid, Duke University

The Muscular

System7

Slides 1 to 110

Overview of Muscular System

What are the Three Types of

Muscle Tissue?

• Under voluntary control

• Skeletal muscles

• The muscular system

• Under involuntary control

• Cardiac muscle

• Heart wall

• Smooth muscle

• Visceral organs

Overview of Muscular System

• Skeletal muscles attach to bones

directly or indirectly

• What are the five functions?

• Produce movement of skeleton

• Maintain posture and body position

• Support soft tissues

• Guard entrances and exits

• Maintain body temperature

Anatomy of Skeletal Muscles

What Is The Gross Anatomy?

• Connective tissue organization

• Epimysium

• Fibrous covering of whole muscle

• Perimysium

• Fibrous covering of fascicle

• Endomysium

• Fibrous covering of a single cell (a

muscle fiber)

• Tendons (or aponeurosis)

The Organization of a Skeletal Muscle

Figure 7-1

What is the Microanatomy of a

Muscle Fiber?

• Sarcolemma

• Muscle cell membrane

• Sarcoplasm

• Muscle cell cytoplasm

• Sarcoplasmic reticulum (SR)

• Like smooth ER

• Transverse tubules (T tubules)

• Myofibrils (contraction organelle)

Sarcomere—Repeating structural unit

of the myofibril

• Parts of a sarcomere

• Myofilaments

• Thin filaments (actin)

• Thick filaments (myosin)

• Z lines at each end

• Anchor for thin filaments

The Organization of a Single Muscle Fiber

Figure 7-2(a)

The Organization of a

Single Muscle Fiber

Figure 7-2(b)

The Organization of a Single Muscle Fiber

Figure 7-2(cde)Anatomy of Skeletal MusclesPLAY

Changes in the

Appearance of

a Sarcomere

During

Contraction of

a Skeletal

Muscle Fiber

Figure 7-3 (1 of 2)

Changes in the

Appearance of

a Sarcomere

During

Contraction of

a Skeletal

Muscle Fiber

Figure 7-3 (2 of 2)

Control of Muscle Contraction

The Structure and Function of the

Neuromuscular Junction

Figure 7-4(a)

Figure 7-4(b-c)

Synapticcleft

Vesicles in the synaptic terminal fuse

with the neuronal membrane and dump

their contents into the synaptic cleft.

The binding of ACh to the receptors

increases the membrane permeability to

sodium ions. Sodium ions then rush

into the cell.

An action potential spreads across the

surface of the sarcolemma. While this

occurs, AChE removes the ACh.

Appearance of an action potential in the sarcolemma

ACh binding at the motor and plate

Release of acetylcholine

Arrival of an action potential at the synaptic terminal

Sarcolemma ofmotor end plate

Arriving action potential

Vesicles

AChE molecules

AChreceptorsite

Action potential

Synaptic terminal

Sarcolemma

Musclefiber

Actionpotential

Figure 7-4(b-c)

Synapticcleft

Vesicles

AChE molecules

AChreceptorsite

Action potential

Synaptic terminal

Sarcolemma

Musclefiber

Figure 7-4(b-c)

Synapticcleft

Vesicles

AChE molecules

AChreceptorsite

Action potential

Synaptic terminal

Sarcolemma

Musclefiber

Figure 7-4(b-c)

Synapticcleft

into the cell.

Vesicles

AChE molecules

AChreceptorsite

Action potential

Synaptic terminal

Sarcolemma

Musclefiber

Figure 7-4(b-c)

Synapticcleft

into the cell.

An action potential spreads across the

surface of the sarcolemma. While this

occurs, AChE removes the ACh.

Appearance of an action potential in the sarcolemma

Vesicles

AChE molecules

AChreceptorsite

Action potential

Synaptic terminal

Sarcolemma

Musclefiber

Actionpotential

What is the Contraction Process?

• Actin active sites and myosin cross-bridges

interact

• Thin filaments slide past thick filaments

• Cross-bridges undergo a cycle of movement

• Attach, pivot, detach, return

Figure 7-5

1 of 7

Resting sarcomere

Myosin head

Myosin reactivation

Active-site exposure

Cross bridge detachment

Cross-bridge formation

Pivoting of myosin head

Troponin

ActinTropomyosin

Active site

Sarcoplasm

ADP + P

Figure 7-5

2 of 7

Resting sarcomere

Myosin head

Troponin

ActinTropomyosin

Figure 7-5

3 of 7

Resting sarcomere

Myosin head

Troponin

ActinTropomyosin

Active site

Sarcoplasm

Figure 7-5

4 of 7

Resting sarcomere

Myosin head

Active-site exposure Cross-bridge formation

Troponin

ActinTropomyosin

Active site

Sarcoplasm

Figure 7-5

5 of 7

Resting sarcomere

Myosin head

Active-site exposure Cross-bridge formation

Troponin

ActinTropomyosin

Active site

Sarcoplasm

ADP + P

Figure 7-5

6 of 7

Resting sarcomere

Myosin head

Troponin

ActinTropomyosin

Active site

Sarcoplasm

ADP + P

Control of Muscle Fiber ContractionPLAY

Figure 7-5

7 of 7

Resting sarcomere

Myosin head

Myosin reactivation

Troponin

ActinTropomyosin

Active site

Sarcoplasm

ADP + P

Table 7-1

Summary of Contraction Process

Key Note

Skeletal muscle fibers shorten as thin

filaments interact with thick filaments and

sliding occurs. The trigger for contraction

is the calcium ions released by the SR

when the muscle fiber is stimulated by its

motor neuron. Contraction is an active

process; relaxation and the return to

resting length is entirely passive.

Muscle Mechanics

What are Some Basic Muscle

Definitions?

• Muscle tension—The pulling force on the

tendons that muscle cells generate when

contracting

• Muscle twitch—A brief contraction-relaxation

response to a single action potential

Muscle Mechanics

The Twitch and Development of Tension

Figure 7-6

Muscle Mechanics

The Effects of Repeated Stimulations

Figure 7-7

Muscle Mechanics

What are Motor Units?

• Motor Unit —A motor neuron and all

the muscle cells it controls

• Recruitment—To increase muscle

tension by activating more motor units

Muscle Mechanics

Motor Units

Figure 7-8

Muscle Mechanics

Key Note

All voluntary (intentional) movements

involve the sustained, sub-tetanic

contractions of skeletal muscle fibers

organized into distinct motor units. The

force generated can be increased by

increasing the frequency of action

potentials or by recruiting additional

motor units.

Muscle Mechanics

What are the Two Types of

Contractions?

• Isotonic contraction

The tension (load) on a muscle stays

constant (iso = same, tonic = tension)

during a movement. (Example: lifting a

• Isometric contraction

The length of a muscle stays constant

(iso = same, metric = length) during a

“contraction” (Example: holding a baby

Energetics of Muscle Contraction

Muscle Metabolism

Figure 7-9(a)

Muscle Metabolism

Figure 7-9(b)

Muscle Metabolism

Figure 7-9(c)

Muscle Fatigue—When a muscle

loses ability to contract due to a low

pH (lactic acid buildup), low ATP

levels, or other problems

Key Note

Skeletal muscles at rest metabolize

fatty acids and store glycogen. During

light activity, muscles can generate ATP

through the aerobic breakdown of

carbohydrates, lipids, or amino acids.

At peak levels of activity, most of the

energy is provided by anaerobic

reactions that generate lactic acid.

Muscle Performance

Physical Conditioning

• Hypertrophy

Increase in muscle bulk. Can result from

anerobic training.

Muscle Performance

Key Note

What you don’t use, you lose. When

motor units are inactive for days or

weeks, muscle fibers break down their

contractile proteins and grow smaller

and weaker. If inactive for long periods,

muscle fibers may be replaced by

fibrous tissue.

Cardiac and Smooth Muscle

Figure 7-10(a)

Cardiac

Muscle

Tissue

Figure 7-10(b)

Smooth Muscle Tissue

Table 7-2

Anatomy of the Muscular System

An Overview

of the Major

Skeletal

Muscles

Figure 7-11(a)

An Overview

of the Major

Skeletal

Muscles

Figure 7-11(b)

What Are the Origins, Insertions, and

Actions?

• Origin

Muscle attachment that remains fixed

• Insertion

Muscle attachment that moves

• Action

What joint movement a muscle produces

What are the Primary Action

Categories?

• Prime mover (agonist)

• Main muscle in an action

• Synergist

• Helper muscle in an action

• Antagonist

• Opposed muscle to an action

What are the Selected Muscles

of the Head?

• Frontalis

• Orbicularis oris

• Buccinator

• Masseter

• Temporalis

Muscles of the Head and Neck

Figure 7-12(a)

Muscles of the

Head and

Figure 7-12(b)

Muscles of the Head and Neck

Figure 7-12(c)

Muscles of the Anterior Neck

Figure 7-13

Muscles of

the Spine

Figure 7-14

What are the Axial Muscles

of the Trunk?

• Abdominal region

• Rectus abdominis

• External oblique

• Internal oblique

• Transversus abdominis

Figure 7-15(a)

Oblique and Rectus

Muscles and the

Diaphragm

Oblique and Rectus Muscles and

the Diaphragm

Figure 7-15(b)

Oblique and Rectus Muscles and

the Diaphragm

Figure 7-15(c)

Muscles of the Perineum—Female

Figure 7-16(a)

Muscles of the Perineum—Male

Figure 7-16(b)

Muscles of the Shoulder

Figure 7-17(a)

Muscles of the Shoulder

Figure 7-17(b)

Muscles that Move the Arm

Figure 7-18(a)

Muscles that Move the Arm

Figure 7-18(b)

Muscles That Move the Forearm and Wrist

Figure 7-19

Muscles That Move the Thigh

Figure 7-20(a)

Muscles That Move

the Thigh

Figure 7-20(b)

Figure 7-21

Muscles That Move the Leg

Muscles That Move the Foot and Toes

Figure 7-22(a)

Figure 7-22(b)

Muscles That Move

the Foot and Toes

Figure 7-22(c)

Muscles That Move

the Foot and Toes

Figure 7-22(d)

Muscles That

Move the Foot

and Toes

Aging and the Muscular System

What are Age-Related

Reductions?

• Muscle size

• Muscle elasticity

• Muscle strength

• Exercise tolerance

• Injury recovery ability

The Muscular System · Contraction of a Skeletal Muscle Fiber Figure 7-3 (1 of 2) Anatomy of...

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