Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: The Muscular System

Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

Chapter 8:The Muscular

System


Cohen: Memmler’s The Human Body in Health and Disease

Key Terms

acetylcholine insertion spasm

actin synapse

myalgia

myoglobin tendon

bursitis myosin tonus

neuromuscular junction tropomyosin

neurotransmitter troponin

origin

glycogen



Types of Muscle

Learning Outcome

1. Compare the three types of muscle tissue.



Types of Muscle



Types of Muscle

✓Checkpoint

8-1 What are the three types of muscle?

Exam Question: Which ones are voluntary?

Which one is visceral?

Which one is in heart?

Which ones are striated?



Types of Muscle

?Pop Quiz

8.1 Which type of muscle tissue is striated and involuntary?

A)Cardiac

B)Intercalated

C)Smooth

D)Skeletal



Types of Muscle

?Pop Quiz Answer

8.1 Which type of muscle tissue is striated and involuntary?

A)Cardiac

B)Intercalated

C)Smooth

D)Skeletal



The Muscular System

Skeletal Muscle Has Three Primary Functions:

•Skeletal movement

•Posture maintenance

•Heat generation



The Muscular System

Muscle Cells in Action

•Neuromuscular junction (NMJ): The point at which a nerve fiber contacts a muscle fiber

– A type of synapse

– NMJ anatomy

• Motor neuron

• Neurotransmitter (acetylcholine; ACh)

• Motor end plate (on muscle fiber)

Contains acetylcholine receptors



The Muscular System


•NMJ allows motor neuron to stimulate muscle fiber to become electrically excited (action potential)

•Action potential stimulates muscle contraction

•Events at the NMJ

– Ach is released from motor neuron into synaptic cleft

– Ach diffuses across synaptic cleft towards motor end plate

– Ach binds to receptors on motor end plate and stimulates action potential



Figure 8-2 Nerve supply to a skeletal muscle and the NMJ.



The Muscular System

✓Checkpoints

8-2 What are the three main functions of skeletal muscle?

8-3 What is the name of the special synapse in which a nerve cell makes contact with a muscle cell?

8-4 What neurotransmitter is involved in the stimulation of skeletal muscle cells?



The Muscular System


•The sarcomere is the functional unit of contraction in the skeletal muscle fiber

•Sarcomere anatomy:

– Thick filaments (myosin)

– Thin filaments (actin)

– Regulatory proteins

• Troponin

• Tropomyosin



Figure 8-3 Detailed structure of a skeletal muscle cell.



The Muscular System


•Sarcomeres contract via the sliding filament mechanism:

– Myosin heads bind to actin, forming cross-bridges

– Using stored energy, myosin heads pull actin filaments together within the sarcomeres and the cell shortens

– New ATP is used to detach myosin heads and move them back into position for another “power stroke”



Figure 8-4 Sliding filament mechanism of skeletal muscle contraction.

Sliding filament mechanism of skeletal muscle contraction.



The Muscular System


•Calcium regulates sarcomeric contraction within the muscle cell:

– Action potential from NMJ travels to sarcoplasmic reticulum (SR)

– SR releases calcium into cytoplasm

– Calcium shifts troponin and tropomyosin off of thin filament so that binding sites on actin are exposed

– Sliding filament mechanism now able to proceed

– Muscle relaxes when stimulation ends and calcium is pumped back into SR



Figure 8-5 Role of calcium in muscle contraction.



The Muscular System

Summary of Events in a Muscle Contraction

1.ACh is released from neuron ending into synaptic cleft at NMJ

2.ACh binds to motor end plate and produces action potential

3.Action potential travels to sarcoplasmic reticulum (SR)

4.SR releases calcium into cytoplasm

5.Calcium shifts troponin and tropomyosin so that binding sites on actin are exposed



The Muscular System

Summary of Events in a Muscle Contraction (continued)

6.Myosin heads bind to actin, forming cross-bridges

7.Using stored energy, myosin heads pull actin filaments together within sarcomeres and cell shortens

8.New ATP is used to detach myosin heads and move them back to position for another “power stroke”

9.Muscle relaxes when stimulation ends and calcium is pumped back into SR



The Muscular System

✓Checkpoints

8-6 What filaments interact to produce muscle contraction?

8-7 What mineral is needed for interaction of the contractile filaments?

Exam Question: What are the regulatory proteins in muscle fibers?

What is the source of Energy for contraction?



The Muscular System

?Pop Quiz

8.3 The two filaments that form cross-bridges are

A)Actin and troponin

B)Tropomyosin and myosin

C)Actin and myosin

D)Troponin and tropomyosin



The Muscular System

?Pop Quiz Answer

8.3 The two filaments that form cross-bridges are

A)Actin and troponin

B)Tropomyosin and myosin

C)Actin and myosin

D)Troponin and tropomyosin



The Muscular System

Energy Sources

•Muscle contraction requires ATP

•Skeletal muscle prefers to produces ATP via aerobic metabolism, which requires

– Oxygen

– Glucose

•Storage compounds ensure an adequate supply of oxygen and glucose for aerobic ATP metabolism

– Myoglobin

– Glycogen



The Muscular System

Energy Sources

•During strenuous activity, muscle cells use anaerobic ATP metabolism, which does not require ATP

– Breakdown of creatine phosphate

– Anaerobic glycolysis

• Lactic acid accumulation and oxygen debt

• Excess postexercise oxygen consumption

– After strenuous exercise, person takes in extra oxygen (via rapid breathing) to remove lactic acid and replenish energy stores



The Muscular System

Effects of Exercise

•Improved balance, joint flexibility

•Increased muscle size (hypertrophy)

•Improved muscle tissue

•Vasodilation

•Strengthened heart muscle

•Improved breathing and respiratory efficiency

•Weight control

•Stronger bones



The Muscular System

✓Checkpoints

8-8 What compound is formed in oxidation of nutrients that supplies the energy for contraction?

8-9 What acid accumulates during anaerobic metabolism?



The Mechanics of Muscle Movement

• Tendons attach muscles to bones.

– Origin: Attached to more fixed part of skeleton

– Insertion: Attached to more movable part of skeleton



Figure 8-6 Muscle attachments to bones.



Figure 8-8 Superficial muscles, anterior view.



Figure 8-9 Superficial muscles, posterior view.



Skeletal Muscle Groups

Muscles That Move the Shoulder and Arm




Muscles That Move the Forearm and Hand



Figure 8-11 Muscles that move the forearm and hand.

What does carpi refer to in the names of muscles? Digitorum?




Muscles of the Trunk



Figure 8-12 Muscles of respiration.



What does rectus mean? Oblique?

Figure 8-13 Muscles of the abdominal wall.




Muscles That Move the Leg and Thigh




Muscles That Move the Leg and Thigh (continued)



Figure 8-15 Muscles of the thigh.

How many muscles make up the quadriceps femoris?




✓Checkpoints

8-14 What muscle is most important in breathing?



Muscular Disorders

Common Terms Used When Describing Muscular Disorders

•Spasms

– Colic

– Seizure

– Convulsion

•Cramps

•Atrophy



Muscular Disorders

Muscle Injuries

•Strains

•Sprains



Muscular Disorders

Diseases of Muscle

•Muscular dystrophy

•Myalgia

– Myositis

•Fibromyalgia syndrome (FMS)

•Bursitis





Muscular Disorders

Disorders of Associated Structures

•Bursitis

•Tendinitis

•Carpal tunnel syndrome



Figure 8-17 Carpal tunnel syndrome.

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Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: The Muscular System