Download Slide 1

An Introduction to Muscle Tissue
 Muscle Tissue
 A primary tissue type, divided into
 Skeletal muscle
 Cardiac muscle
 Smooth muscle
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
An Introduction to Muscle Tissue
 Skeletal Muscles
 Are attached to the skeletal system
 Allow us to move
 The muscular system
 Includes only skeletal muscles
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Functions of Skeletal Muscles
 Produce skeletal movement
 Maintain body position
 Support soft tissues
 Guard openings
 Maintain body temperature
 Store nutrient reserves
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Structures
 Muscle tissue (muscle cells or fibers)
 Connective tissues
 Nerves
 Blood vessels
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Structures
 Organization of Connective Tissues
 Muscles have three layers of connective tissues
 Epimysium:
– exterior collagen layer
– connected to deep fascia
– Separates muscle from surrounding tissues
 Perimysium:
– surrounds muscle fiber bundles (fascicles)
– contains blood vessel and nerve supply to fascicles
 Endomysium:
– surrounds individual muscle cells (muscle fibers)
– contains capillaries and nerve fibers contacting muscle cells
– contains myosatellite cells (stem cells) that repair damage
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Structures
Figure 10–1 The Organization of Skeletal Muscles.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Structures
 Organization of Connective Tissues
 Muscle attachments
 Endomysium, perimysium, and epimysium come
together:
– at ends of muscles
– to form connective tissue attachment to bone matrix
– i.e., tendon (bundle) or aponeurosis (sheet)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Structures
 Nerves
 Skeletal muscles are voluntary muscles, controlled by
nerves of the central nervous system (brain and
spinal cord)
 Blood Vessels
 Muscles have extensive vascular systems that
 Supply large amounts of oxygen
 Supply nutrients
 Carry away wastes
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Are very long
 Develop through fusion of mesodermal
cells (myoblasts)
 Become very large
 Contain hundreds of nuclei
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–2 The Formation of a Multinucleate Skeletal Muscle Fiber.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–2a The Formation of a Multinucleate Skeletal Muscle Fiber.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–2b The Formation of a Multinucleate Skeletal Muscle Fiber.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 The sarcolemma
 The cell membrane of a muscle fiber (cell)
 Surrounds the sarcoplasm (cytoplasm of muscle
fiber)
 A change in transmembrane potential begins
contractions
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 Transverse tubules (T tubules)
 Transmit action potential through cell
 Allow entire muscle fiber to contract
simultaneously
 Have same properties as sarcolemma
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 Myofibrils
 Lengthwise subdivisions within muscle fiber
 Made up of bundles of protein filaments
(myofilaments)
 Myofilaments are responsible for muscle
contraction
 Types of myofilaments:
– thin filaments:
» made of the protein actin
– thick filaments:
» made of the protein myosin
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 Sarcoplasmic reticulum (SR)
 A membranous structure surrounding each
myofibril
 Helps transmit action potential to myofibril
 Similar in structure to smooth endoplasmic
reticulum
 Forms chambers (terminal cisternae) attached to
T tubules
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 Triad
 Is formed by one T tubule and two terminal
cisternae
 Cisternae:
– concentrate Ca2+ (via ion pumps)
– release Ca2+ into sarcomeres to begin muscle
contraction
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–3 The Structure of a Skeletal Muscle Fiber.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 Sarcomeres
 The contractile units of muscle
 Structural units of myofibrils
 Form visible patterns within myofibrils
 Muscle striations
 A striped or striated pattern within myofibrils:
– alternating dark, thick filaments (A bands) and light, thin
filaments (I bands)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 Sarcomeres
 M Lines and Z Lines:
– M line:
» the center of the A band
» at midline of sarcomere
– Z lines:
» the centers of the I bands
» at two ends of sarcomere
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 Sarcomeres
 Zone of overlap:
– the densest, darkest area on a light micrograph
– where thick and thin filaments overlap
 The H Band:
– the area around the M line
– has thick filaments but no thin filaments
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Internal Organization of Muscle Fibers
 Sarcomeres
 Titin:
– are strands of protein
– reach from tips of thick filaments to the Z line
– stabilize the filaments
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–4a Sarcomere Structure.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–4b Sarcomere Structure.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–5 Sarcomere Structure.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–6 Levels of Functional Organization in a Skeletal Muscle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–6 Levels of Functional Organization in a Skeletal Muscle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Sarcomere Function
 Transverse tubules encircle the sarcomere
near zones of overlap
 Ca2+ released by SR causes thin and thick
filaments to interact
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Muscle Contraction
 Is caused by interactions of thick and thin
filaments
 Structures of protein molecules determine
interactions
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Four Thin Filament Proteins
 F-actin (Filamentous actin)
 Is two twisted rows of globular G-actin
 The active sites on G-actin strands bind to myosin
 Nebulin
 Holds F-actin strands together
 Tropomyosin
 Is a double strand
 Prevents actin–myosin interaction
 Troponin
 A globular protein
 Binds tropomyosin to G-actin
 Controlled by Ca2+
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–7a, b Thick and Thin Filaments.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Initiating Contraction
 Ca2+ binds to receptor on troponin molecule
 Troponin–tropomyosin complex changes
 Exposes active site of F-actin
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Thick Filaments
 Contain twisted myosin subunits
 Contain titin strands that recoil after
stretching
 The mysosin molecule
 Tail:
– binds to other myosin molecules
 Head:
– made of two globular protein subunits
– reaches the nearest thin filament
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–7c, d Thick and Thin Filaments.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Myosin Action
 During contraction, myosin heads
 Interact with actin filaments, forming cross-bridges
 Pivot, producing motion
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Skeletal Muscle Contraction
 Sliding filament theory
 Thin filaments of sarcomere slide toward M line,
alongside thick filaments
 The width of A zone stays the same
 Z lines move closer together
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–8a Changes in the Appearance of a Sarcomere during the
Contraction of a Skeletal Muscle Fiber.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–8b Changes in the Appearance of a Sarcomere during the
Contraction of a Skeletal Muscle Fiber.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
 Skeletal Muscle Contraction
 The process of contraction
 Neural stimulation of sarcolemma:
– causes excitation–contraction coupling
 Cisternae of SR release Ca2+:
– which triggers interaction of thick and thin filaments
– consuming ATP and producing tension
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Skeletal Muscle Fibers
Figure 10–9 An Overview of Skeletal Muscle Contraction.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Neuromuscular Junction
 Is the location of neural stimulation
 Action potential (electrical signal)
 Travels along nerve axon
 Ends at synaptic terminal
 Synaptic terminal:
– releases neurotransmitter (acetylcholine or
ACh)
– into the synaptic cleft (gap between synaptic
terminal and motor end plate)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Neuromuscular Junction
Figure 10–10a, b Skeletal Muscle Innervation.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Neuromuscular Junction
Figure 10–10c Skeletal Muscle Innervation.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Neuromuscular Junction
Figure 10–10c Skeletal Muscle Innervation.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Neuromuscular Junction
 The Neurotransmitter
 Acetylcholine or ACh
 Travels across the synaptic cleft
 Binds to membrane receptors on sarcolemma
(motor end plate)
 Causes sodium–ion rush into sarcoplasm
 Is quickly broken down by enzyme
(acetylcholinesterase or AChE)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Neuromuscular Junction
Figure 10–10c Skeletal Muscle Innervation.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Neuromuscular Junction
 Action Potential
 Generated by increase in sodium ions in
sarcolemma
 Travels along the T tubules
 Leads to excitation–contraction coupling
 Excitation–contraction coupling:
– action potential reaches a triad:
» releasing Ca2+
» triggering contraction
– requires myosin heads to be in “cocked” position:
» loaded by ATP energy
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Neuromuscular Junction
Figure 10–11 The Exposure of Active Sites.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
 Five Steps of the Contraction Cycle
 Exposure of active sites
 Formation of cross-bridges
 Pivoting of myosin heads
 Detachment of cross-bridges
 Reactivation of myosin
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
Figure 10–12 The Contraction Cycle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
[INSERT FIG. 10.12, step 1]
Figure 10–12 The Contraction Cycle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
Figure 10–12 The Contraction Cycle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
Figure 10–12 The Contraction Cycle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
Figure 10–12 The Contraction Cycle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
Figure 10–12 The Contraction Cycle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
 Fiber Shortening
 As sarcomeres shorten, muscle pulls together,
producing tension
 Contraction Duration
 Depends on
 Duration of neural stimulus
 Number of free calcium ions in sarcoplasm
 Availability of ATP
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
Figure 10–13 Shortening during a Contraction.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
 Relaxation
 Ca2+ concentrations fall
 Ca2+ detaches from troponin
 Active sites are re-covered by tropomyosin
 Sarcomeres remain contracted
 Rigor Mortis
 A fixed muscular contraction after death
 Caused when
 Ion pumps cease to function; ran out of ATP
 Calcium builds up in the sarcoplasm
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
 Skeletal muscle fibers shorten as thin filaments
slide between thick filaments
 Free Ca2+ in the sarcoplasm triggers contraction
 SR releases Ca2+ when a motor neuron
stimulates the muscle fiber
 Contraction is an active process
 Relaxation and return to resting length are
passive
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Contraction Cycle
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 The all–or–none principle
 As a whole, a muscle fiber is either contracted or
relaxed
 Tension of a Single Muscle Fiber
 Depends on
 The number of pivoting cross-bridges
 The fiber’s resting length at the time of stimulation
 The frequency of stimulation
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Tension of a Single Muscle Fiber
 Length–tension relationship
 Number of pivoting cross-bridges depends on:
– amount of overlap between thick and thin fibers
 Optimum overlap produces greatest amount of tension:
– too much or too little reduces efficiency
 Normal resting sarcomere length:
– is 75% to 130% of optimal length
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–14 The Effect of Sarcomere Length on Active Tension.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Tension of a Single Muscle Fiber
 Frequency of stimulation
 A single neural stimulation produces:
– a single contraction or twitch
– which lasts about 7–100 msec.
 Sustained muscular contractions:
– require many repeated stimuli
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Three Phases of Twitch
 Latent period before contraction
 The action potential moves through sarcolemma
 Causing Ca2+ release
 Contraction phase
 Calcium ions bind
 Tension builds to peak
 Relaxation phase
 Ca2+ levels fall
 Active sites are covered
 Tension falls to resting levels
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–15 The Development of Tension in a Twitch.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–15 The Development of Tension in a Twitch.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Treppe
 A stair-step increase in twitch tension
 Repeated stimulations immediately after relaxation
phase
 Stimulus frequency <50/second
 Causes a series of contractions with increasing
tension
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Tension of a Single Muscle Fiber
 Wave summation
 Increasing tension or summation of twitches
 Repeated stimulations before the end of relaxation
phase:
– stimulus frequency >50/second
 Causes increasing tension or summation of
twitches
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Tension of a Single Muscle Fiber
 Incomplete tetanus
 Twitches reach maximum tension
 If rapid stimulation continues and muscle is not
allowed to relax, twitches reach maximum level of
tension
 Complete Tetanus
 If stimulation frequency is high enough, muscle
never begins to relax, and is in continuous
contraction
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–16 Effects of Repeated Stimulations.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–16 Effects of Repeated Stimulations.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Tension Produced by Whole Skeletal
Muscles
 Depends on
 Internal tension produced by muscle fibers
 External tension exerted by muscle fibers on
elastic extracellular fibers
 Total number of muscle fibers stimulated
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Tension Produced by Whole Skeletal Muscles
 Motor units in a skeletal muscle
 Contain hundreds of muscle fibers
 That contract at the same time
 Controlled by a single motor neuron
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Tension Produced by Whole Skeletal Muscles
 Recruitment (multiple motor unit summation)
 In a whole muscle or group of muscles, smooth motion and
increasing tension are produced by slowly increasing the size or
number of motor units stimulated
 Maximum tension
 Achieved when all motor units reach tetanus
 Can be sustained only a very short time
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–17 The Arrangement and Activity of Motor Units in a Skeletal
Muscle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–17 The Arrangement and Activity of Motor Units in a Skeletal
Muscle.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Tension Produced by Whole Skeletal Muscles
 Sustained tension
 Less than maximum tension
 Allows motor units rest in rotation
 Muscle tone
 The normal tension and firmness of a muscle at rest
 Muscle units actively maintain body position, without motion
 Increasing muscle tone increases metabolic energy used,
even at rest
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Two Types of Skeletal Muscle Tension
 Isotonic contraction
 Isometric contraction
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Two Types of Skeletal Muscle Tension
 Isotonic Contraction
 Skeletal muscle changes length:
– resulting in motion
 If muscle tension > load (resistance):
– muscle shortens (concentric contraction)
 If muscle tension < load (resistance):
– muscle lengthens (eccentric contraction)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Two Types of Skeletal Muscle Tension
 Isometric contraction
 Skeletal muscle develops tension, but is prevented
from changing length
Note: iso- = same, metric = measure
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–18a, b Isotonic and Isometric Contractions.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–18c, d Isotonic and Isometric Contractions.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Resistance and Speed of Contraction
 Are inversely related
 The heavier the load (resistance) on a muscle
 The longer it takes for shortening to begin
 And the less the muscle will shorten
 Muscle Relaxation
 After contraction, a muscle fiber returns to resting
length by
 Elastic forces
 Opposing muscle contractions
 Gravity
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
Figure 10–19 Load and Speed of Contraction.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Elastic Forces
 The pull of elastic elements (tendons and ligaments)
 Expands the sarcomeres to resting length
 Opposing Muscle Contractions
 Reverse the direction of the original motion
 Are the work of opposing skeletal muscle pairs
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Tension Production
 Gravity
 Can take the place of opposing muscle
contraction to return a muscle to its resting
state
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
 Sustained muscle contraction uses a lot of
ATP energy
 Muscles store enough energy to start
contraction
 Muscle fibers must manufacture more ATP
as needed
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
 ATP and CP Reserves
 Adenosine triphosphate (ATP)
 The active energy molecule
 Creatine phosphate (CP)
 The storage molecule for excess ATP energy in resting
muscle
 Energy recharges ADP to ATP
 Using the enzyme creatine phosphokinase (CPK or
CK)
 When CP is used up, other mechanisms generate
ATP
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
 ATP Generation
 Cells produce ATP in two ways
 Aerobic metabolism of fatty acids in the
mitochondria
 Anaerobic glycolysis in the cytoplasm
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
 ATP Generation
 Aerobic metabolism
 Is the primary energy source of resting muscles
 Breaks down fatty acids
 Produces 34 ATP molecules per glucose molecule
 Anaerobic glycolysis
 Is the primary energy source for peak muscular activity
 Produces two ATP molecules per molecule of glucose
 Breaks down glucose from glycogen stored in skeletal
muscles
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
 Energy Use and Muscle Activity
 At peak exertion
 Muscles lack oxygen to support mitochondria
 Muscles rely on glycolysis for ATP
 Pyruvic acid builds up, is converted to lactic acid
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
Figure 10–20 Muscle Metabolism.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
Figure 10–20a Muscle Metabolism.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
Figure 10–20b Muscle Metabolism.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
Figure 10–20c Muscle Metabolism.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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 pH (lactic acid)
 Muscle exhaustion and pain
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
ATP and Muscle Contraction
 The Recovery Period
 The time required after exertion for muscles to
return to normal
 Oxygen becomes available
 Mitochondrial activity resumes
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Muscle Fiber Types
 Three Types of Skeletal Muscle Fibers
 Fast fibers
 Slow fibers
 Intermediate fibers
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Muscle Fiber Types
Figure 10–21 Fast versus Slow Fibers.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Muscle Fiber Types
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Muscle Fiber Types
 Muscles and Fiber Types
 White muscle
 Mostly fast fibers
 Pale (e.g., chicken breast)
 Red muscle
 Mostly slow fibers
 Dark (e.g., chicken legs)
 Most human muscles
 Mixed fibers
 Pink
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiac Muscle Tissue
 Structure of Cardiac Tissue
 Cardiac muscle is striated, found only in
the heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiac Muscle Tissue
Figure 10–22 Cardiac Muscle Tissue.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiac Muscle Tissue
Figure 10–22a Cardiac Muscle Tissue.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiac Muscle Tissue
Figure 10–22c Cardiac Muscle Tissue.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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”
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Smooth Muscle Tissue
 Structure of Smooth Muscle
 Nonstriated tissue
 Different internal organization of actin and
myosin
 Different functional characteristics
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Smooth Muscle Tissue
Figure 10–23a Smooth Muscle Tissue.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Smooth Muscle Tissue
Figure 10–23b Smooth Muscle Tissue.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Smooth Muscle Tissue
 Functional Characteristics of Smooth
Muscle
 Excitation–contraction coupling
 Length–tension relationships
 Control of contractions
 Smooth muscle tone
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Smooth Muscle Tissue
 Functional Characteristics of Smooth Muscle
 Excitation–contraction coupling
 Free Ca2+ in cytoplasm triggers contraction
 Ca2+ binds with calmodulin:
– in the sarcoplasm
– activates myosin light–chain kinase
 Enzyme breaks down ATP, initiates contraction
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Smooth Muscle Tissue
 Functional Characteristics of Smooth
Muscle
 Smooth muscle tone
 Maintains normal levels of activity
 Modified by neural, hormonal, or chemical factors
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Comparing Muscle Tissues
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Comparing Muscle Tissues
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings