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Chapter 12b Muscles.

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Presentation on theme: "Chapter 12b Muscles."— Presentation transcript:

1 Chapter 12b Muscles

2 Summation of Contractions
Figure 12-17a

3 Summation of Contractions
Figure 12-17b

4 Summation of Contractions
Figure 12-17c

5 Summation of Contractions
Figure 12-17d

6 Motor Units One muscle may have many motor units of different fiber types. SPINAL CORD Neuron 1 Neuron 2 Neuron 3 Motor nerve KEY Muscle fibers Motor unit 1 Motor unit 2 Motor unit 3 Interactive Physiology® Animation: Muscular System: Contraction of Motor Units PLAY Figure 12-18

7 Mechanics of Body Movement
Isotonic contractions create force and move load Concentric action is a shortening action climbing Eccentric action is a lengthening action Downhill skiing, going down stairs Isometric contractions create force without moving a load Series elastic elements; sarcomeres shorten while elastic elements stretch resulting in little change in overall length

8 Isotonic Contraction Figure 12-19a

9 Isometric Contraction
Figure 12-19b

10 Series Elastic Elements in Muscle
Schematic of the series elastic elements Elastic components Triceps muscle 1 2 3 Contractile components Biceps muscle Elastic element Muscle length Sarcomeres 1 Muscle at rest 2 Isometric contraction: Muscle has not shortened. Sarcomeres shorten, generating force, but elastic elements stretch, allowing muscle length to remain the same. 3 Isotonic contraction: Sarcomeres shorten more but, because elastic elements are already stretched, the entire muscle must shorten. Figure 12-20

11 The Arm is a Lever and Fulcrum System
Biceps muscle Lever Load Fulcrum Figure 12-21a

12 The Arm is a Lever and Fulcrum System
(b) F1 F2 = 2 kg 5 cm 15 cm Figure 12-21b

13 The Arm is a Lever and Fulcrum System
A 7-kg load is added to the hand 25 cm from the elbow. D1 5 cm D2 25 cm Figure 12-21c

14 The Arm Amplifies Speed of Movement of the Load
Lever 5 cm Fulcrum 1 cm Figure 12-22

15 Load-Velocity Relationship in Skeletal Muscle
Figure 12-23

16 Muscle cramp: sustained painful contraction Overuse Disuse/Atrophy
Muscle Disorders Muscle cramp: sustained painful contraction Overuse Disuse/Atrophy Acquired disorders Inherited disorders Duchenne’s muscular dystrophy Dystrophin McArdle’s disease Myophosphorylase deficiency glycogenosis – glycogen not converted to glucose 6-phosphate

17 Duration of Muscle Contraction in the Three Types of Muscle
Skeletal Cardiac Smooth Tension 1 2 3 4 5 Time (sec) Figure 12-24

18 Contraction and relaxation slower Uses less energy
Smooth Muscle Contraction and relaxation slower Uses less energy Maintains force for long periods Low oxygen consumption

19 Smooth muscle is not studied as much as skeletal muscle because
It has more variety Anatomy makes functional studies difficult It is controlled by hormones, paracrines, and neurotransmitters It has variable electrical properties Multiple pathways influence contraction and relaxation

20 Types of Smooth Muscle Autonomic neuron varicosity Gap junctions
Small intestine Gap junctions Neuro- transmitter Smooth muscle cell Receptor (a) Single-unit smooth muscle cells Figure 12-25a

21 Much smaller than skeletal muscle fibers
Smooth Muscle Much smaller than skeletal muscle fibers Has longer actin and myosin filaments Myosin ATPase activity much slower Myosin light chain plays regulatory role Not arranged in sarcomeres Has less sarcoplasmic reticulum IP3-receptor channel is the primary calcium channel Calcium also enters cell from extracellular fluid

22 Shares features with both skeletal and smooth muscle
Cardiac Muscle Shares features with both skeletal and smooth muscle Like skeletal: Striated; sarcomere structure Unlike skeletal: Muscle fibers shorter; may be branched; have single nucleus Like smooth: Electrically linked to one another; some exhibit pacemaker potentials; under sympathetic and parasympathetic control as well as hormone control

23 Muscle Summary Table 12-3

24 Skeletal muscles Muscle Summary
Origin, insertion, flexors, extensors, and antagonistic muscles T-tubules, sarcoplasmic reticulum, myofibrils, thick filament, thin filament, actin, myosin, and crossbridges Sarcomere, Z disks, I bands, A band, H zone, and M line Muscle tension, load, sliding filament theory, tropomyosin, troponin, Ca2+-ATPase, myosin ATPase, power stroke, rigor state

25 Mechanics of body movement
Summary Skeletal muscle Excitation-contraction coupling, DHP receptors, and Ca2+ release channels Twitch, latent period, phosphocreatine, and muscle fatigue Muscle fiber types, myoglobin, tetanus, and motor unit Mechanics of body movement Isotonic versus isometric contractions Series elastic elements, levers, and fulcrums

26 Smooth muscle Cardiac muscle Summary
Types of smooth muscle, IP3-receptor channel, calmodulin, myosin light chain kinase, myosin light protein chains, and myosin phosphatase Myogenic contraction, slow wave or pacemaker potentials, and pharmacomechanical coupling Cardiac muscle Comparison to other muscle types

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