Seeley/Anatomy and Physiology

Lecture Outline

CHAPTER OVERVIEW: This chapter introduces the muscular system. The structures and mechanisms that allow contraction of individual fibers are described in detail. The structural and functional connections between motor neurons and skeletal muscles are described. The properties of whole muscle contraction are described and the relation to the activity of motor units is explained. Differences in cellular structure and contractile properties among muscle types are explained.

OUTLINE (two or three fifty-min. lectures):

Chapt. Object.	Topic Outline, Chapter 10	Figures & Tables	Trnspcy. Acetates	Trnspcy. Masters
1	I. General Functional Characteristics of Muscle	Table 10.1, p.271
	a. Contractility b. Excitability c. Extensibility d. Elasticity
2	II. Skeletal Muscle: Structure	Fig. 10.1, p.272
	A. Connective Tissue	Fig. 10.2, p.272	TA-125
	1. External Lamina - Just Beyond Sarcolemma
	2. Endomysium
	3. Perimysium - Forms Fasciculi
	4. Epimysium
	5. Fascia
3	B. Muscle Fibers a. Develop from Myoblasts b. Sarcoplasm with Myofibrils	Fig. 10.3, p.274	TA-126
	1) Actin Myofilaments
	2) Myosin Myofilaments
	1. Sarcomeres	Fig. 10.4, p.275
	1) Z Disk	Fig. 10.5, p.275
	2) I Bands (Isotropic)
	3) A Bands (Anisotropic)
	4) H Zones
	5) M Lines
	2. Actin and Myosin Myofilaments a. Tropomyosin and Troponin b. Globular Actin (G protein) c. Heavy Myosin Molecules d. Crossbridges 3. T-Tubules and Sarcoplasmic Reticulum	Fig. 10.6a, p.276 Fig. 10.6b, p.276 Fig. 10.7, p.276	TA-127 TA-127 TA-128
	a. Terminal Cisternae & Triads
	III. Sliding Filament Model IV. Physiology of Skeletal Muscle Fibers	Predict Quest. 1: Fig. 10.8, p.277	TA-129
4	A. Neuromuscular Junction	Fig. 10.9, p.278; Predict Quest. 2	TA-130
	a. Synapse b. Presynaptic Terminal	Fig. 10.10, p.279	TA-131
	c. Synaptic Cleft
	d. Postsynaptic Membrane/Motor End Plate e. Acetylcholine as the Neurotransmitter f. Acetylcholinesterase	Fig. 10.11a, p.280 Fig. 10.11b, p.280	TA-132 TA-132
5	B. Excitation-Contraction Coupling	Fig. 10.12, p.281; Clinical Note, p.278-279; Predict Question 3	TA-133
	1. Action Potential in Sarcolemma
	2. Action Potential Along T-Tubule System
	3. Release of Calcium from Sarcoplasmic Reticulum	Fig. 10.12a, p.281
	4. Binding of Calcium to Troponin	Fig. 10.12b, p.281
	5. Shift in Troponin-Tropomyosin Complex
	6. Uncovering of Actin Active Sites
	7. Myosin Binding to Actin
	8. Cycles of Cross-Bridge Formation	Fig. 10.12c, p.281
	C. Energy Requirements for Muscle Contraction	Fig. 10.13, p.282	TA-134
	1. Power Strokes
	2. Recovery Strokes
	3. Cycles Require Ongoing Presence of ATP & Ca²⁺
5, 6	D. Muscle Relaxation	Predict Quest. 4
	1. Breaking of Cross-Bridges
	2. Active Transport of Ca²⁺ into Sarcoplasmic Reticulum

	V. Physiology of Skeletal Muscle
	A. Muscle Twitch	Table 10.2, p.283; Fig. 10.14, p.283
	1. Lag (Latent) Phase
	2. Contraction Phase
	3. Relaxation Phase
	B. Stimulus Strength and Muscle Contraction
	1. All-or None Law of Skeletal Muscle Fiber Contraction
	a. Subthreshold Stimulus Produces no Contraction
	b. Stimuli of Threshold or Higher Strength Produce Similar Contraction
	2. Motor Units
	a. Structure b. All-or-None Fashion	Fig. 10.15, p.284 Fig. 10.16, p.285	TA-135
	c. Multiple Motor Unit Summation	Predict Quest. 5
	1) Graded Response to Stimulus Strength
	2) Submaximal Stimulus Intensity Possible
	3) Recruitment of Motor Units
6	C. Stimulus Frequency and Muscle Contraction
	1. Multiple Wave Summation (Little or no Relaxation Between Contractions)	Fig. 10.17, p.286
	a. Incomplete Tetanus
	b. Complete Tetanus
	2. Relaxation Between Contractions and Treppe	Fig. 10.18, p.286
	3. Intracellular Events Responsible for These Phenomena
	D. Types of Whole Muscle Contractions	Table 10.3, p.287
	1. Isometric Contractions
	2. Isotonic Contractions
6	3. Muscle Tone	Predict Quest. 6
	4. Concentric Contractions
	5. Eccentric Contractions
7	E. Length versus Tension	Fig. 10.19, p.289	TA-136
	1. Active Tension and Active Tension Curve
	2. Passive Tension
	3. Total Tension
	4. Relation of Active Tension to Sarcomere Length
8	F. Fatigue	Clinical Note, p.288
	1. Psychological
	2. Muscular
	3. Synaptic
9	G. Physiological Contracture and Rigor Mortis
	1. Role of Ca²⁺
	2. Role of ATP Availability
	H. Energy Sources
	1. Creatine Phosphate a. Most Rapid
	b. Supply Quickly Exhausted (10-15 Sec.)
	2. Anaerobic Respiration
	a. Occurs in Absence of O₂
	b. Lactic Acid Waste Product
	c. Faster, but Less Efficient than Aerobic Respiration
	3. Aerobic Respiration
	a. Slower, but Many More ATP Produced
	b. CO₂ waste Product
10	I. An Oxygen Debt	Clinical Note,p.291; Predict Quest. 7
11	J. Slow and Fast Fibers
	1. Slow-Twitch or High Oxidative Fibers
	a. Contain Myoglobin
	b. Many Mitochondria
	c. Fibers are Resistant to Muscular Fatigue
	d. Slow Speed of Contraction
	2. Fast-Twitch or Low Oxidative Fibers
	a. Rapid Turn-Over of ATP
	b. Contain Much Glycogen
	c. Fibers Fatigue Quickly
	3. Distribution in the Body of Each Type
	a. Most Muscles Contain Both Types of Cells
	b. Proportion Established Developmentally
12	K. Effects of Exercise
	1. Cannot Change the Type of a Cell
	a. Can Improve Blood Supply
	b. Can Train to Produce Fatigue-Resistant Fast-Twitch Muscles	Predict Quest. 8
	2. Cell Hypertrophy in Response to Use	Clinical Note, p.292
	3. Cell Atrophy in Response to Disuse
13	L. Heat Production
	1. Increased During and Immediately After Exercise
	2. Shivering Increases Body Temperature

	VI. Smooth Muscle
	A. Cell Structure 1. Myofilaments Not Arranged in Sarcomeres	Fig. 10.20, p.293
	a. Intermediate Filaments
	b. Dense Bodies	Fig. 10.21, p.293
	2. Sarcoplasmic Reticulum Less Abundant
	3. Caveolae Rather than T-Tubules
	5. Different Mechanism for Cross-Bridge Formation
	a. Have Calmodulin as Ca²⁺Binding Site
	b. Myosin Kinase
	c. Myosin Phosphatase	Fig. 10.22, p.294	TA-137
14	B. Types of Smooth Muscle
	1. Visceral or Unitary Smooth Muscle
	a. Many Gap Junctions
	b. Form Functional Syncytia
	2. Multiunit Smooth Muscle
	a. Few Gap Junctions
	b. Act as Independent Units
15	C. Electrical Properties of Smooth Muscle
	1. Smaller Resting Membrane Potential
	2. Slow Waves of Depolarization and Repolarization	Fig. 10.23a, p.295
	3. Spontaneous Action Potentials Result	Fig. 10.23b, p.295
	4. Mechanical Response is not All-or-None
	5. Pacemaker Cells Have Fastest Rates of Spontaneous Depolarization
	6. Opening of Ligand-Gated Ca²⁺ Channels also Initiates Contraction Without an Action Potential	Predict Quest. 9
16	D. Functional Properties of Smooth Muscle
	1. Some Visceral Smooth Muscle has Autorhythmic Contractions
	2. Smooth Muscle Contracts in Response to Sudden Stretch but not Slow Increase in Length
	3. Smooth Muscle Tone Relatively Constant in Response to Gradual Increase in Length
	4. Amplitude of Contraction Constant, Although Muscle Length Varies
	E. Regulation of Smooth Muscle
	1. Autonomic Nervous System Innervation = Involuntary Control
	2. Hormones Important
	a. Epinephrine
	b. Oxytocin
	c. Local Factors - Histamine & Prostaglandins

17	VII. Cardiac Muscle (Detail in Chapter 20)
	A. Found Only in Heart
	B. Specialized Cell-to-Cell Attachments, the Intercalated Disks	Clinical Focus, p.297
	VIII. Systems Pathology	Predict Quest. 10 Systemic Interactions, p.299

IMPORTANT CONSIDERATIONS:: To separate this material into three segments, the logical breaks come after the discussion of the structure and explanation of excitation/contraction coupling, and then between summation and miscellaneous characteristics of muscles. Students may need to be lead through the sequential processes of contraction. The dimension of time and the involvement of multiple cellular components are important organizing concepts which students will have to sort out to achieve understanding of the physiology of muscle contraction.

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