1. Chapter 9 Muscular System
Three Types of Muscle Tissues
Cardiac Muscle
Skeletal Muscle
Smooth Muscle
9-2

2. Structure of a Skeletal Muscle
organ of the muscular system
skeletal muscle tissue
nervous tissue
blood
connective tissues
fascia
tendon
9-3

3. Structure of a Skeletal Muscle
fascicles
muscle fibers
myofibrils
thick and thin filaments
9-4

4. Skeletal Muscle Fiber sarcolemma sacroplasm triad myofibril sarcomere
cisterna of sarcoplasmic reticulum
transverse tubule
myofibril
sarcomere
9-5

5. Sarcomere
I band
A band
H zone
Z line
M line
9-6

6. Myofilaments Muscle 3.mov Thin Filaments Thick Filaments
associated with troponin and tropomyosin
Thick Filaments
Muscle 3.mov
9-7

7. Neuromuscular Junction
site where axon and muscle fiber communicate
motor end plate
synaptic vesicles
9-8

8. Motor Unit
9-9

9. Stimulus for Contraction
acetylcholine (ACh)
binds to acetylcholine receptors on motor end plate
Muscle 2.mov
9-10

10. Excitation Contraction Coupling
position of tropomyosin is altered
9-11

11. Sliding Filament Theory
When sarcromeres shorten, thick and thin filaments slide past one another
9-12

12. Cross-bridge Cycling Muscle 4.mov 0010.exe
myosin cross-bridge pulls actin
ADP and phosphate released from myosin
linkage between actin and myosin cross-bridge break
ATP splits
Muscle 4.mov
0010.exe
9-13

13. Relaxation
acetylcholinesterase –
Muscle 4.mov
9-14

14. Energy Sources for Contraction
1) Creatine phosphate 2) Cellular respiration
creatine phosphate –
9-15

15. Oxygen Debt Oxygen debt – oxygen not available glycolysis continues
liver converts lactic acid to glucose
9-17

16. Muscle Fatigue
commonly caused from
decreased blood flow
cramp –
9-18

17. Heat Production by-product of cellular respiration
muscle cells are major source of body heat
blood transports heat throughout body
9-19

18. Muscular Responses Threshold Stimulus Recording a Muscle Contraction
twitch
latent period
period of contraction
period of relaxation
refractory period
all-or-none response
9-20

19. Summation process by which individual twitches combine
produces sustained contractions
can lead to tetanic contractions
9-21

20. Recruitment of Motor Units
whole muscle composed of many motor units
as intensity of stimulation increases, recruitment of motor units continues until all motor units are activated
9-22

21. Sustained Contractions
smaller motor units recruited first
larger motor units recruited later
muscle tone –
9-23

22. Types of Contractions isotonic – concentric – isometric – eccentric –
9-24

23. Fast and Slow Twitch Muscle Fibers
Slow-twitch fibers (type I)
most myoglobin
good blood supply
Fast-twitch fatigue-resistant fibers (type IIb)
intermediate fibers
Fast-twitch glycolytic fibers (type II)
9-25

24. Smooth Muscle Fibers Compared to skeletal muscle fibers single nucleus
elongated with tapering ends
myofilaments randomly organized
lack transverse tubules
sarcoplasmic reticula not well developed
9-26

25. Smooth Muscle Contraction
Resembles skeletal muscle contraction
interaction between actin and myosin
both use calcium and ATP
both depend on impulses
Different from skeletal muscle contraction
smooth muscle lacks troponin
two neurotransmitters affect smooth muscle
stretching can trigger smooth muscle contraction
9-28

26. Cardiac Muscle muscle fibers joined together by intercalated discs
fibers branch
network of fibers contracts as a unit
self-exciting and rhythmic
longer refractory period than skeletal muscle
9-29

27. Skeletal Muscle Actions
origin –
insertion –
prime mover (agonist) – primarily responsible for movement
synergists – assist prime mover
antagonist – resist prime mover’s action and cause movement in the opposite direction
9-30

28. Major Skeletal Muscles
9-31

29. Major Skeletal Muscles
9-32

30. Life-Span Changes myoglobin, ATP, and creatine phosphate decline
by age 80, half of muscle mass has atrophied
adipose cells and connective tissues replace muscle tissue
exercise helps to maintain muscle mass and function
9-65

31. Clinical Application Myasthenia Gravis autoimmune disorder
receptors for acetylcholine on muscle cells are attacked
weak and easily fatigued muscles result
difficulty swallowing and chewing
ventilator needed if respiratory muscles are affected
treatments include
drugs that boost acetylcholine
removing thymus gland
immunosuppressant drugs
antibodies
9-66