Title: Structure and Function of the Muscular, Neuromuscular, Cardiovascular, and Respiratory Systems
1Structure and Function of the Muscular,
Neuromuscular, Cardiovascular, and Respiratory
Systems
chapter 1
Structure and Function of the Muscular,
Neuromuscular, Cardiovascular, and Respiratory
Systems
Gary R. Hunter, PhD, CSCS, FACSMRobert T.
Harris, PhD
2Chapter Objectives
- Describe the macrostructure and micro-structure
of muscle. - Describe the sliding-filament theory.
- Describe the characteristics of different muscle
fiber types. - Describe the characteristics of the
cardio-vascular and respiratory systems.
3Section Outline
- Muscular System
- Macrostructure and Microstructure
- Sliding-Filament Theory of Muscular Contraction
- Resting Phase
- Excitation-Contraction Coupling Phase
- Contraction Phase
- Recharge Phase
- Relaxation Phase
4Muscular System
- Macrostructure and Microstructure
- Each skeletal muscle is an organ that contains
muscle tissue, connective tissue, nerves, and
blood vessels. - Fibrous connective tissue, or epimysium, covers
the body's more than 430 skeletal muscles.
5Schematic Drawing of a Muscle
- Figure 1.1 (next slide)
- Schematic drawing of a muscle illustrating three
types of connective tissue - Epimysium (the outer layer)
- Perimysium (surrounding each fasciculus, or group
of fibers) - Endomysium (surrounding individual fibers)
6Figure 1.1
7Motor Unit
- Figure 1.2 (next slide)
- A motor unit consists of a motor neuron and the
muscle fibers it innervates. - There are typically several hundred muscle fibers
in a single motor unit.
8Figure 1.2
9Muscle Fiber
- Figure 1.3 (next slide)
- Sectional view of a muscle fiber
10Figure 1.3
11Microstructure
Modified from Squire, pg. 66
12Myosin and Actin
- Figure 1.4 (next slide)
- The slide shows a detailed view of the myosin and
actin protein filaments in muscle. - The arrangement of myosin (thick) and actin
(thin) filaments gives skeletal muscle its
striated appearance.
13Figure 1.4
14Sarcomere functional unit of striated muscle
Z line
Electron micrograph
15(No Transcript)
16Figure 5. Main Intermediate Filaments and
Cytoskeletal Proteins Linking the Extracellular
Matrix with the Structural Muscle Proteins
Associated with Mutations Causing Cardiac and
Skeletal Myopathy. In the mature cardiac and
skeletal muscle, the Z bands hold together the
actin filaments and have a fundamental role in
the transmission of tension throughout the
myofibril. The desmin filaments, consisting of
10-nm-wide intermediate filaments, encircle the Z
bands and are fastened to them and to one another
by plectin filaments.619 Desmin (from the Greek
noun desmos, meaning link or bond) mechanically
integrates the contractile actions of the muscle
fiber laterally by linking the individual
myofibrils at the Z-band level, as shown for
three adjacent myofibrils, and longitudinally by
linking the Z bands to the sarcolemma and nuclei
(along with other intermediate-filamentassociated
proteins).6 The heat-shock protein B-crystallin
protects, or chaperones, the desmin filaments
from stress-induced damage. Desmin, along with
B-crystallin and plectin, forms an organized
network at the Z-band level that protects the
structural integrity of the myofibrils during
mechanical stress.16 Mutations in desmin,
B-crystallin, and plectin1420 cause fragility of
the myofibrils and lead to their destruction
after repetitive mechanical stress. Mutations in
other cytoskeletal proteins, including
dystrophin, actin, the sarcoglycan complex,21 the
nuclear protein emerin, and the intermediate
nuclear filaments lamin A and C,22 are also
associated with cardiomyopathy and skeletal
myopathy. Dalakas et al. 342 (11) 770, Figure
5 March 16, 2000
cytoskeleton
17- Figure 1. Functional Bypass of Genetic Defect by
Enhanced Glycosylation. - Under normal conditions, glycoproteins gain
complex carbohydrate moieties during processing
as they are transported to the cell membrane
(Panel A). There, the carbohydrate components
help bind to ligands in the extracellular milieu.
In the case of skeletal muscle, the glycosylation
of -dystroglycan is critical to its binding to
laminin, agrin, and perlecan. Defects in
glycosylation lead to truncated carbohydrate
chains (Panel B). Abnormal glycosylation
interferes with the interactions between normal
-dystroglycan and matrix proteins and may be the
reason for muscle cell degeneration in this group
of muscular dystrophies. Barresi et al.2 showed
that overexpression of a glycosyltransferase
(LARGE) can hyperglycosylate -dystroglycan and
thereby enhance its binding to matrix proteins,
even though the pattern of glycosylation may be
abnormal (Panel C). This restoration of function
as a result of enhanced glycosylation may be an
effective treatment for a variety of muscular
dystrophies. Rando 351 (12) 1254, Figure
1 September 16, 2004
18Figure 1. Components of Myocyte Cytoarchitecture
(Panel A) and Mutations Causing Dilated
Cardiomyopathy and Conduction-System Disease or
Autosomal Dominant EmeryDreifuss Muscular
Dystrophy (Panel B). Mutations in the rod domain
of the lamin A/C gene cause isolated dilated
cardiomyopathy and conduction-system disease,
presumably through perturbed interactions with
nuclear or cytoplasmic constituents (Panel A).
Other cytoskeletal molecules implicated in the
pathophysiology of human dilated cardiomyopathy
include actin, dystrophin, and the
dystrophin-associated glycoprotein
complex.12,23,24,25,26,27,28 Interactions between
lamins A and C and cytoskeletal or sarcomere
proteins are unknown. Conduction-system disease
is a common feature of EmeryDreifuss muscular
dystrophy caused by defects in the head or tail
domain of the lamin gene or by emerin mutations.
Mutations causing dilated cardiomyopathy and
conduction-system disease or autosomal dominant
EmeryDreifuss muscular dystrophy are distributed
in distinct domains of the lamin dimer (Panel B).
Lamins A and C have identical structures
throughout the amino-terminal head (NH3),
-helical rod domain, and proximal
carboxyl-terminal tail (COOH), but they differ in
their distal amino acids (lamin A is shown in
gray, and lamin C is shown in black). Mutations
in the rod domain (Arg60Gly, Leu85Arg, Asn195Lys,
and Glu203Gly) cause dilated cardiomyopathy and
conduction-system disease without skeletal
myopathy the mutation at the carboxyl terminal
(Arg571Ser) is associated with subclinical
skeletal-muscle disease. Mutations that cause
EmeryDreifuss muscular dystrophy (Gln6Stop,
Arg453Trp, Arg527Pro, and Leu530Pro) do not
affect the -helical rod domain. Fatkin et al.
341 (23) 1715, Figure 1 December 2, 1999
19Hunter and Chien 341 (17) 1276, Figure
3 October 21, 1999
Figure 3. Primary Structural Components of the
Linkage between the Cytoskeleton and the
Extracellular Matrix, Including Actin, the
DystrophinGlycoprotein Complex, and Laminin-2
(Merosin). Genetic defects in these components
lead to dilated cardiomyopathy, with or without
associated skeletal myopathy. This complex is
physically associated with the Z-disk of cardiac
myocytes, the Z-disk components desmin
(associated with dilated cardiomyopathy in humans
and mice) and -actinin, and a muscle-specific
cytoskeletal protein (MLP) (associated with
dilated cardiomyopathy in mice).23 The question
mark indicates an unknown factor.
20Muscular Dystrophy A frequently fatal disease of
muscle deterioration
- Muscular dystrophies have in the past been
classified based on subjective and sometimes - subtle differences in clinical presentation, such
as age of onset, involvement of particular - muscles, rate of progression of pathology, mode
of inheritance.
- Since the discovery of dystrophin, numerous
genetic disease loci have been linked to protein - products and to cellular phenotypes, generating
models for studying the pathogenesis of the - dystrophies.
- Proteins localized in the nucleus, cytosol,
cytoskeleton, sarcolemma, and ECM.
Cohn and Campbell (2000) Muscle Nerve
231459-1471.
21Dystrophin function transmission of force to
extracellular matrix
DGC dystrophin dystroglycan (a and
b) sarcoglycans (a, b, g, d) syntrophins (a,
b1) dystrobrevins (a, b) sarcospan laminin-a2
(merosin)
(Some components of the dystrophin
glycoprotein complex are relatively recent
discoveries, so one cannot assume that all
players are yet known.)
Cohn and Campbell (2000) Muscle Nerve
231459-1471.
22Key Point
- The discharge of an action potential from a motor
nerve signals the release of calcium from the
sarcoplasmic reticulum into the myofibril,
causing tension development in muscle.
23Muscular System
- Sliding-Filament Theory of Muscular Contraction
- The sliding-filament theory states that the actin
filaments at each end of the sarcomere slide
inward on myosin filaments, pulling the Z-lines
toward the center of the sarcomere and thus
shortening the muscle fiber.
24Contraction of a Myofibril
- Figure 1.5 (next slide)
- (a) In stretched muscle the I-bands and H-zone
are elongated, and there is low force potential
due to reduced cross-bridgeactin alignment. - (b) When muscle contracts (here partially), the
I-bands and H-zone are shortened. - (c) With completely contracted muscle, there is
low force potential due to reduced
cross-bridgeactin alignment.
25Figure 1.5
26Myosin is a molecular motor
Myosin is a hexamer 2 myosin heavy chains 4
myosin light chains
27Shortening velocity dependent on ATPase
activity Different myosin heavy chains (MHCs)
have different ATPase activities. There are at
least 7 separate skeletal muscle MHC
genesarranged in series on chromosome 17. Two
cardiac MHC genes located in tandem on chromosome
14. The slow b cardiac MHC is the predominant
gene expressed in slow fibers of mammals.
Goldspink (1999) J Anat 194323-334.
28http//health.howstuffworks.com/muscle2.htm
29Muscular System
- Sliding-Filament Theory of Muscular Contraction
- Resting Phase
- Excitation-Contraction Coupling Phase
- Contraction Phase
- Recharge Phase
- Relaxation Phase
30Section Outline
- Neuromuscular System
- Activation of Muscles
- Muscle Fiber Types
- Motor Unit Recruitment Patterns During Exercise
- Preloading
- Proprioception
- Muscle Spindles
- Golgi Tendon Organs
- Older Muscle
31Neuromuscular System
- Activation of Muscles
- Arrival of the action potential at the nerve
terminal causes the release of acetylcholine.
Once a sufficient amount of acetylcholine is
released, an action potential is generated across
the sarco-lemma, and the fiber contracts. - The extent of control of a muscle depends on the
number of muscle fibers within each motor unit. - Muscles that function with great precision may
have as few as one muscle fiber per motor
neuron. - Muscles that require less precision may have
several hundred fibers served by one motor
neuron.
32Key Term
- all-or-none principle All of the muscle fibers
in the motor unit contract and develop force at
the same time. There is no such thing as a motor
neuron stimulus that causes only some of the
fibers to contract. Similarly, a stronger action
potential cannot produce a stronger contraction.
33Stimulated Motor Unit
- Figure 1.6 (next slide)
- Twitch, twitch summation, and tetanus of a motor
unit - a single twitch
- b force resulting from summation of two
twitches - c unfused tetanus
- d fused tetanus
34Figure 1.6
35Neuromuscular System
- Muscle Fiber Types
- Type I (slow-twitch)
- Type IIa (fast-twitch)
- Type IIab (fast-twitch) now named as Type IIax
- Type IIb (fast-twitch) now named as Type IIx
36Table 1.1
37Key Point
- Motor units are composed of muscle fibers with
specific morphological and physio-logical
characteristics that determine their functional
capacity.
38Neuromuscular System
- Motor Unit Recruitment Patterns During Exercise
- The force output of a muscle can be varied
through change in the frequency of activation of
individual motor units or change in the number of
activated motor units.
39Table 1.2
40Neuromuscular System
- Preloading
- Occurs when a load is lifted, since sufficient
force must be developed to overcome the inertia
of the load - Proprioception
- Information concerning kinesthetic sense, or
conscious appreciation of the position of body
parts with respect to gravity - Processed at subconscious levels
41Key Point
- Proprioceptors are specialized sensory receptors
that provide the central nervous system with
information needed to maintain muscle tone and
perform complex coordi-nated movements.
42Neuromuscular System
- How Can Athletes Improve Force Production?
- Recruit large muscles or muscle groups during an
activity. - Increase the cross-sectional area of muscles
involved in the desired activity. - Preload a muscle just before a concentric action
to enhance force production during the subsequent
muscle action. - Use preloading during training to develop
strength early in the range of motion.
43Force Production Influencing Factors
- Motor Unit Recruitment
- Rate of stimulation of the motor unit (rate
coding) - Type of motor units activated (FT or ST)
- Preloading
- Cross-sectional area (Muscle size)
- Velocity of shortening
- Angle of pennation (acute or joint angle and
fixed or inherent) - Sarcomere and muscle length
- Initial muscle length
- Speed of muscle action
- Shortening or lengthening contractions
44Neuromuscular System
- Proprioception
- Muscle Spindles
- Muscle spindles are proprioceptors that consist
of several modified muscle fibers enclosed in a
sheath of connective tissue.
45Muscle Spindle
- Figure 1.7 (next slide)
- When a muscle is stretched, deformation of the
muscle spindle activates the sensory neuron,
which sends an impulse to the spinal cord, where
it synapses with a motor neuron, causing the
muscleto contract.
46Figure 1.7
47Neuromuscular System
- Proprioception
- Golgi Tendon Organs (GTO)
- Golgi tendon organs are proprioceptors located in
tendons near the myotendinous junction. - They occur in series (i.e., attached end to end)
with extrafusal muscle fibers.
48Golgi Tendon Organ
- Figure 1.8 (next slide)
- When an extremely heavy load is placed on the
muscle, discharge of the GTO occurs. - The sensory neuron of the GTO activates an
inhibitory interneuron in the spinal cord, which
in turn synapses with and inhibits a motor neuron
serving the same muscle.
49Figure 1.8
50Neuromuscular System
- Older Muscle
- Muscle function is reduced in older adults.
- Reductions in muscle size and strength are
amplified in weight-bearing extensor muscles. - Muscle atrophy with aging results from losses in
both number and size of muscle fibers, especially
Type II muscle fibers. - Inactivity plays a major role but cannot account
for all of the age-related loss of muscle and
function.
51Section Outline
- Cardiovascular System
- Heart
- Valves
- Conduction System
- Electrocardiogram
- Blood Vessels
- Arteries
- Capillaries
- Veins
- Blood
52Cardiovascular System
- Heart
- The heart is a muscular organ made up of two
interconnected but separate pumps. - The right ventricle pumps blood to the lungs.
- The left ventricle pumps blood to the rest of the
body.
53Heart and Blood Flow
- Figure 1.9 (next slide)
- Structure of the human heart and course of blood
flow through its chambers
54Figure 1.9
55Cardiovascular System
- Heart
- Valves
- Tricuspid valve and mitral (bicuspid) valve
- Aortic valve and pulmonary valve
- Valves open and close passively, depending on the
pressure gradient - Conduction System
- Controls the mechanical contraction of the heart
56Electrical Conduction System
- Figure 1.10 (next slide)
- The electrical conduction system of the heart
57Figure 1.10
58Cardiac Impulse
- Figure 1.11 (next slide)
- Transmission of the cardiac impulse through the
heart, showing the time of appearance (in
fractionsof a second) of the impulse in
different parts of the heart
59Figure 1.11
60Cardiovascular System
- Heart
- Electrocardiogram
- Recorded at the surface of the body
- A graphic representation of the electrical
activity of the heart
61Electrocardiogram
- Figure 1.12 (next slide)
- Normal electrocardiogram
62Figure 1.12
63Cardiovascular System
- Blood Vessels
- Blood vessels operate in a closed-circuit system.
- The arterial system carries blood away from the
heart. - The venous system returns blood toward the heart.
64Distribution of Blood
- Figure 1.13 (next slide)
- The slide shows the arterial (right) and venous
(left) components of the circulatory system. - The percent values indicate the distribution of
blood volume throughout the circulatory system at
rest.
65Figure 1.13
66Cardiovascular System
- Blood Vessels
- Arteries
- Capillaries
- Veins
67Cardiovascular System
- Blood
- Hemoglobin transports oxygen and serves as an
acidbase buffer. - Red blood cells facilitate carbon dioxide removal.
68Key Point
- The cardiovascular system transports nutrients
and removes waste products while helping to
maintain the environment for all the bodys
functions. The blood transports oxygen from the
lungs to the tissues for use in cellular
metabolism, and it transports carbon dioxide from
the tissues to the lungs, where it is removed
from the body.
69Section Outline
- Respiratory System
- Exchange of Air
- Exchange of Respiratory Gases
70Respiratory System
- Figure 1.14 (next slide)
- Gross anatomy of the human respiratory system
71Figure 1.14
72Respiratory System
- Exchange of Air
- The amount and movement of air and expired gases
in and out of the lungs are controlled by
expansion and recoil of the lungs.
73Expiration and Inspiration
- Figure 1.15 (next slide)
- The slide shows contraction and expansion of the
thoracic cage during expiration and inspiration,
illustrating diaphragmatic contraction, elevation
of the rib cage, and function of the
intercostals. - The vertical and anteroposterior diameters
increase during inspiration.
74Figure 1.15
75Respiratory System
- Exchange of Respiratory Gases
- The primary function of the respiratory system is
the basic exchange of oxygen and carbon dioxide.