ATP and Muscle Contraction Muscle Fatigue When muscles
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ATP and Muscle Contraction § Muscle Fatigue § When muscles can no longer perform a required activity, they are fatigued § Results of Muscle Fatigue § Depletion of metabolic reserves § Damage to sarcolemma and sarcoplasmic reticulum § Low p. H (lactic acid) § Muscle exhaustion and pain
ATP and Muscle Contraction § The Recovery Period § The time required after exertion for muscles to return to normal § Oxygen becomes available § Mitochondrial activity resumes
ATP and Muscle Contraction § The Cori Cycle § The removal and recycling of lactic acid by the liver § Liver converts lactic acid to pyruvic acid § Glucose is released to recharge muscle glycogen reserves § Oxygen Debt § After exercise or other exertion § The body needs more oxygen than usual to normalize metabolic activities § Resulting in heavy breathing
ATP and Muscle Contraction § Skeletal muscles at rest metabolize fatty acids and store glycogen § During light activity, muscles generate ATP through anaerobic breakdown of carbohydrates, lipids, or amino acids § At peak activity, energy is provided by anaerobic reactions that generate lactic acid as a byproduct
ATP and Muscle Contraction § Heat Production and Loss § Active muscles produce heat § Up to 70% of muscle energy can be lost as heat, raising body temperature § Hormones and Muscle Metabolism § Growth hormone § Testosterone § Thyroid hormones § Epinephrine
ATP and Muscle Contraction § Muscle Performance § Power § The maximum amount of tension produced § Endurance § The amount of time an activity can be sustained § Power and endurance depend on § The types of muscle fibers § Physical conditioning
Muscle Fiber Types § Three Types of Skeletal Muscle Fibers § Fast fibers § Slow fibers § Intermediate fibers
Muscle Fiber Types § Three Types of Skeletal Muscle Fibers § Fast fibers § Contract very quickly § Have large diameter, large glycogen reserves, few mitochondria § Have strong contractions, fatigue quickly
Muscle Fiber Types § Three Types of Skeletal Muscle Fibers § Slow fibers § Are slow to contract, slow to fatigue § Have small diameter, more mitochondria § Have high oxygen supply § Contain myoglobin (red pigment, binds oxygen)
Muscle Fiber Types § Three Types of Skeletal Muscle Fibers § Intermediate fibers § Are mid-sized § Have low myoglobin § Have more capillaries than fast fibers, slower to fatigue
Muscle Fiber Types Figure 10– 21 Fast versus Slow Fibers.
Muscle Fiber Types § Muscle Hypertrophy § Muscle growth from heavy training § Increases diameter of muscle fibers § Increases number of myofibrils § Increases mitochondria, glycogen reserves § Muscle Atrophy § Lack of muscle activity § Reduces muscle size, tone, and power
Muscle Fiber Types § Physical Conditioning § Improves both power and endurance § Anaerobic activities (e. g. , 50 -meter dash, weightlifting): – use fast fibers – fatigue quickly with strenuous activity § Improved by: – frequent, brief, intensive workouts – hypertrophy
Muscle Fiber Types § Physical Conditioning § Improves both power and endurance § Aerobic activities (prolonged activity): – supported by mitochondria – require oxygen and nutrients § Improved by: – repetitive training (neural responses) – cardiovascular training
Muscle Fiber Types § What you don’t use, you lose § Muscle tone indicates base activity in motor units of skeletal muscles § Muscles become flaccid when inactive for days or weeks § Muscle fibers break down proteins, become smaller and weaker § With prolonged inactivity, fibrous tissue may replace muscle fibers
Cardiac Muscle Tissue § Structure of Cardiac Tissue § Cardiac muscle is striated, found only in the heart
Cardiac Muscle Tissue § Seven Characteristics of Cardiocytes § Unlike skeletal muscle, cardiac muscle cells (cardiocytes) § Are small § Have a single nucleus § Have short, wide T tubules § Have no triads § Have SR with no terminal cisternae § Are aerobic (high in myoglobin, mitochondria) § Have intercalated discs
Cardiac Muscle Tissue § Intercalated Discs § Are specialized contact points between cardiocytes § Join cell membranes of adjacent cardiocytes (gap junctions, desmosomes) § Functions of intercalated discs § Maintain structure § Enhance molecular and electrical connections § Conduct action potentials
Cardiac Muscle Tissue Figure 10– 22 Cardiac Muscle Tissue.
Cardiac Muscle Tissue Figure 10– 22 a Cardiac Muscle Tissue.
Cardiac Muscle Tissue Figure 10– 22 c Cardiac Muscle Tissue.
Cardiac Muscle Tissue § Intercalated Discs § Coordination of cardiocytes § Because intercalated discs link heart cells mechanically, chemically, and electrically, the heart functions like a single, fused mass of cells
Cardiac Muscle Tissue § Four Functions of Cardiac Tissue § Automaticity § Contraction without neural stimulation § Controlled by pacemaker cells § Variable contraction tension § Controlled by nervous system § Extended contraction time § Ten times as long as skeletal muscle § Prevention of wave summation and tetanic contractions by cell membranes § Long refractory period
Smooth Muscle Tissue § Smooth Muscle in Body Systems § Forms around other tissues § In blood vessels § Regulates blood pressure and flow § In reproductive and glandular systems § Produces movements § In digestive and urinary systems § Forms sphincters § Produces contractions § In integumentary system § Arrector pili muscles cause “goose bumps”
Smooth Muscle Tissue § Structure of Smooth Muscle § Nonstriated tissue § Different internal organization of actin and myosin § Different functional characteristics
Smooth Muscle Tissue Figure 10– 23 a Smooth Muscle Tissue.
Smooth Muscle Tissue Figure 10– 23 b Smooth Muscle Tissue.
Smooth Muscle Tissue § Eight Characteristics of Smooth Muscle Cells § Long, slender, and spindle shaped § Have a single, central nucleus § Have no T tubules, myofibrils, or sarcomeres § Have no tendons or aponeuroses § Have scattered myosin fibers § Myosin fibers have more heads per thick filament § Have thin filaments attached to dense bodies § Dense bodies transmit contractions from cell to cell
Smooth Muscle Tissue § Functional Characteristics of Smooth Muscle § Excitation–contraction coupling § Length–tension relationships § Control of contractions § Smooth muscle tone
Smooth Muscle Tissue § Functional Characteristics of Smooth Muscle § Excitation–contraction coupling § Free Ca 2+ in cytoplasm triggers contraction § Ca 2+ binds with calmodulin: – in the sarcoplasm – activates myosin light–chain kinase § Enzyme breaks down ATP, initiates contraction
Smooth Muscle Tissue § Functional Characteristics of Smooth Muscle § Length–Tension Relationships § Thick and thin filaments are scattered § Resting length not related to tension development § Functions over a wide range of lengths (plasticity)
Smooth Muscle Tissue § Functional Characteristics of Smooth Muscle § Control of contractions § Multiunit smooth muscle cells: – connected to motor neurons § Visceral smooth muscle cells: – not connected to motor neurons – rhythmic cycles of activity controlled by pacesetter cells
Smooth Muscle Tissue § Functional Characteristics of Smooth Muscle § Smooth muscle tone § Maintains normal levels of activity § Modified by neural, hormonal, or chemical factors
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