2. Location Function Appearance Control
Skeletal
Skeletal Move bones Multinucleated
and striated
Voluntary
Cardiac
Heart Pump blood 1nucleus, striated,
and intercalated
discs
Involuntary
Visceral
(smooth muscle)
Various organs,
example:
GI tract
Various functions,
example:
peristalsis
1nucleus and
no striations
Involuntary
3 Types of Muscular Tissue
OpenStax College, Skeletal Smooth Cardiac, https://commons.wikimedia.org/wiki/File:414_Skeletal_Smooth_Cardiac.jpg, CC BY 3.0
3. Functions of Muscular Tissue
Producing body movements Stabilizing body positions
Generating heat
Storing and mobilizing
substances within the body
5. Levels of Organization within a Skeletal Muscle
Skeletalmuscle
Skeletal muscle Epimysium
Muscle fascicle
Organ made up of fascicles that contain muscle
fibers (cells), blood vessels, and nerves; wrapped
in epimysium
Fascicle
Muscle fascicle Perimysium
Endomysium
Muscle fiber
Bundle of muscle fibers wrapped in perimysium
6. Levels of Organization within a Skeletal Muscle
Muscle fiber (cell)
Muscle fiber
Sarcolemma
Myofibrils
⢠Long, cylindrical cell covered by endomysium and
sarcolemma
⢠Contains sarcoplasm, myofibrils, peripherally located
nuclei, mitochondria, transverse tubules, sarcoplasmic
reticulum, and terminal cisterns
⢠Striated appearance
Myofibril
Sarcoplasmic Thin (actin) Sarcomere H zone Thick
reticulum filament (myosin)
filament
I band A band Z disc M line
⢠Threadlike contractile elements within the sarcoplasm
of muscle fiber that extend for the entire length of the
fiber
⢠Composed of filaments
7. Filaments (myofilaments
)
2 types of contractile proteins within myofibrils are:
⢠Thick filaments composed of myosin
⢠Thin filaments composed of actin, tropomyosin
and troponin
⢠Sliding of thin filaments past thick filaments produces
muscle shortening
Levels of Organization within a Skeletal Muscle
Myofibrils
Portion of a thick filament
Myosin head
Portion of a thin filament
Tropomyosin Actin Troponin
8. Muscle Myofibril
fiber
Microscopic Anatomy of a Muscle Fiber
Sarcomere Thick (myosin)
filament
Thin (actin)
filament
I band A band M line
Z disc
H zone
Sarcoplasmic
reticulum
10. Components of a Sarcomere
Z discs Narrow, plate-shaped regions of dense material that
separate one sarcomere
from the next
A band Dark, middle part of the sarcomere that extends for
the entire length of the thick filaments and includes
those parts of the thin filament that overlap them
I band Lighter, less dense area of the sarcomere that
contains the remainder of the thin filaments but no
thick ones. A Z disc passes through the center of
each I band.
H zone Narrow region in the center of each A band that
contains thick filaments but no thin filaments
M line Region in the center of the H zone that contains
proteins that hold thick filaments together at the
center of the sarcomere
13. Muscle Proteins Structural
Alpha-actinin
(structural protein
of Z disc)
Nebulin
(anchors thin
filaments to Z disc)
Dystrophin
(links thin filament
to integral
membrane
proteins)
Myomesin
(forms M line
proteins)
Titin
(connects Z disc
to M line)
14. Skeletal Muscle Fiber Proteins
Type Description
Contractile
proteins:
Proteins that generate force during muscle contractions
Myosin Contractile protein that makes up a thick filament; molecule consists of a tail and 2 myosin
heads, which bind to myosin-binding sites on actin molecules of a thin filament during muscle
contraction
Actin Contractile protein that is the main component of a thin filament; each actin molecule has a
myosin-binding site where the myosin head of a thick filament binds during muscle contraction
Regulatory
proteins:
Proteins that help switch the muscle contraction process on and off
Tropomyosin Regulatory protein that is a component of a thin filament; when skeletal muscle fiber is relaxed,
tropomyosin covers myosin-binding sites on actin molecules, thereby preventing myosin from
binding to actin
Troponin Regulatory protein that is a component of a thin filament; when calcium ions (Ca2+) bind to
troponin, it changes shape; this conformational change moves tropomyosin away from myosin-
binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds
to actin
15. Skeletal Muscle Fiber Proteins
Type Description
Structural
proteins:
Proteins that keep thick and thin filaments of myofibrils in proper alignment, give myofibrils
elasticity and extensibility, and link myofibrils to the sarcolemma and the extracellular matrix
Titin Structural protein that connects the Z disc to the M line of a sarcomere, thereby helping to
stabilize the thick filament position; can stretch and then spring back unharmed, and thus
accounts for much of the elasticity and extensibility of myofibrils
ďĄ-Actinin Structural protein of Z discs that attaches to actin molecules of a thin filament; helps anchor thin
filaments to Z discs and regulates the length of thin filaments during development
Myomesin Structural protein that wraps around the entire length of each thin filament; helps anchor thin
filaments to Z discs and regulates the length of the thin filaments during development
Nebulin Structural protein that wraps around entire length of each thin filament; helps anchor thin
filaments to Z discs and regulates length of thin filaments during development
Dystrophin Structural protein that links thin filaments of a sarcomere to integral membrane proteins in the
sarcolemma, which are attached in turn to proteins in the connective tissue matrix that surrounds
muscle fibers; thought to help reinforce the sarcolemma and help transmit tension generated by
sarcomeres to tendons
16. The Sliding Filament Mechanism
Myosin pulls on actin
Thin filament slides inward
Z discs move toward each
other, and the sarcomere
shortens
Muscle contraction
H
H
M
M
Z Z
Z Z
17. Cocking of
myosin head
The Contraction Cycle
Crossbridgedetachment
Calcium Actin
Thin
filament
Crossbridge
Thick
filament
Myosin
head
ATP attaches
and myosin
head detaches
Power
stroke
ADPand Pi
released
Thin
filament
Myosin head
Thick
filament
Troponin
Calcium binding
ADPand Pi
28. Creation of Creatine Phosphate (CP)
Creatine kinase catalyzes the transfer of a phosphate group
from CP to ADP to rapidly yieldATP
.
Duration of energy provided: 15 seconds
Creatine Creatine phosphate
Creatine kinase
+
ADP
Restingmuscle
+
ATP
Energy for muscle
contraction
Active muscle
ATP
+
Creatine
29. When CP stores are depleted, glucose is converted into pyruvic acid to generate ATP.
Glycolysis
Anaerobic Glycolysis
Duration of energy provided: 2 minutes
ATP
ATP
Pyruvate
Pyruvate
Lactic acid
to blood
No oxygen
Blood
glucose
Muscle
glycogen
Glucose
30. Under aerobic conditions, pyruvic acid can
enter the mitochondria and undergo a series
of oxygen-requiring reactions to generate
large amounts of ATP
.
Cellular Respiration
31. Cellular Respiration
Duration of energy provided: minutes up to hours
Pyruvic
acid
Fatty
acids
Heat
CO2
H2O
Pyruvic acid can enter the mitochondria and undergo a series of oxygen-requiring
reactions to generate large amounts of ATP
.
O2
Blood
glucose
Cellular respiration
in mitochondria
28 34 ATPmolecules
32. Muscle fatigueis the inability to maintain the
force of contraction after prolonged activity.
Muscle Fatigue
33. The onset of fatigue is due to:
⢠Inadequate release of Ca2+ from SR
⢠Depletion of CP
, oxygen, and nutrients
⢠Build-up of lactic acid and ADP
⢠Insufficient release of ACh at the
neuromuscular junction (NMJ)
Muscle Fatigue
34. Central fatigue is the type of fatigue
associated with the concentration of
neurotransmitters within the central nervous
system,which affects muscle function.
Central Fatigue
35. oxygen debt
Oxygen Consumption after Exercise
Why do people continue to breathe heavily for
a time after stopping exercise?
36. The extra oxygen goes toward:
Oxygen Consumption after Exercise
Replenishing
CPstores
Converting lactate
into pyruvate
Reloading O2
onto myoglobin
37. Control of Muscle Tension
Somatic motor
neuron
Muscle fibers
Spinal cord
The strength of a muscle contraction depends on how many motor units are activated.
Weak muscle contraction
Activation of a few motor units
Strong muscle contraction
Activation of many motor units
39. Wave summation
â results in a stronger
contraction
Frequency of Stimulation
Unfused tetanus Fused tetanus
Time Time Time
T
ension
40. Factors that Influence Tension
3. Sarcomere length
1. Size of motor unit 2. Recruitment of motor units
4. Frequency of stimulation
41. Even when at rest, a skeletal muscle exhibits a
small amount of tension, called tone. Tone is
established by the alternating, involuntary action
of small groups of motor units in a muscle.
Muscle Tone
42. Isotonic Isometric
Tension is constant while muscle length changes. A muscle contracts but
does not change in length.
Isotonic vs. Isometric Contractions
Concentric Eccentric
44. Functional Characteristics
Functional
characteristics
Slow oxidativefibers Fast oxidative-
glycolyticfibers
Fast glycolyticfibers
Capacity for
generating ATP
and method used
High, by aerobic
respiration
Intermediate,by both
aerobic respiration and
anaerobic glycolysis
Low, by anaerobic
glycolysis
Rate of ATP hydrolysis
by myosin ATPase
Slow Fast Fast
Contraction velocity Slow Fast Fast
Fatigue resistance High Intermediate Low
Creatine kinase Lowest amount Intermediate amount Highest amount
Glycogen stores Low Intermediate High
Primaryfunction of
fibers
Maintaining posture
and aerobic endurance
activities
Walking,sprinting Rapid,intense
movements of short
duration
45. Exercise and Skeletal Muscle Tissue
What fiber type does a marathonermost
heavily rely on?
Slow oxidativefibers
⢠Slow enough pace for cellular respiration to occur
⢠Needs a lot of energy
46. Exercise and Skeletal Muscle Tissue
What fiber type does a shot-putter most
heavily rely on?
Fast glycolyticfibers
⢠Needs short bursts of energy
47. Exercise and Skeletal Muscle Tissue
What fiber type does a soccer playermost
heavily rely on?
Fast oxidative-glycolyticfibers
⢠Has periods where more energy and periods of
rest are needed, with slower cellular respiration
48. Cardiac muscle has the same arrangement as skeletal muscle, but also has intercalateddiscs.
Cardiac Muscle
Intercalated discs
Cardiac
muscle fiber
Desmosome
Gap junction
Mitochondria
Nucleus
49. Cardiac muscle cells have more mitochondria,
and their contractions last 10 15 times longer
than skeletal muscle contractions.
Cardiac Muscle
51. Smooth Muscle
Skeletal muscle Cardiac muscle
Smooth muscle
⢠Found in most visceral organs
(e.g., intestines, stomach)
⢠Work automatically without
you being aware of them
⢠Involved in many
'housekeeping' functions
53. ⢠Can shorten/stretch more than skeletal
and cardiac muscle
⢠Fibers shorten in response to stretch!
Smooth Muscle
Relaxed muscle cell
⢠Contracts slower and for longer than
skeletal and cardiac muscle
⢠No sarcomeres, troponin, or tropomyosin
⢠Proteins contract like a corkscrew, using
calmodulin and myosin light chain kinase
Contracted muscle cell
54. Major Features of the 3 Types of Muscle Tissue
Characteristic Skeletal muscle Cardiac muscle Smooth muscle
Microscopic appearance
and features
Long, cylindrical fiber with
many peripherally located
nuclei; unbranched; striated
Branched cylindrical fiber with 1
centrally located nucleus; intercalated
discs join neighboring fibers; striated
Fiber thickest in the middle, tapered
at each end, and with 1centrally
positioned nucleus; not striated
Location Most commonly attached by
tendon to bones
Heart Walls of hollow viscera, airways,
blood vessels, iris and ciliary body of
eye, arrector pili muscles of hair
follicles
Fiber diameter Very large (10 100 ďm) Large (19 20 ďm) Small (3 8 ďm)
Connective tissue
components
Endomysium, perimysium,
and epimysium
Endomysium and perimysium Endomysium
Contractile proteins
organized into sarcomeres
Yes Yes No
Transverse tubules present Yes, aligned with each Yes, aligned with each Z disc No
55. Major Features of the 3 Types of Muscle Tissue
Characteristic Skeletal muscle Cardiac muscle Smooth muscle
Sarcoplasmic reticulum Abundant Some Very little
Junctions between fibers None Intercalated discs contain gap
junctions and desmosomes
Gap junctions in visceral smooth
muscle; none in multi-unit smooth
muscle
Source of Ca2+ for
contraction
Sarcoplasmic reticulum Sarcoplasmic reticulum and interstitial
fluid
Sarcoplasmic reticulum and
interstitial fluid
Regulator proteins for
contraction
Troponin and tropomyosin Troponin and tropomyosin Calmodulin and myosin light-chain
kinase
Speed of contraction Fast Moderate Slow
Nervouscontrol Voluntary (somatic nervous
system)
Involuntary (autonomic nervous
system)
Involuntary (autonomic nervous
system)
Contraction regulation Acetylcholine released by
somatic motor neurons
Acetylcholine and norepinephrine
released by autonomic motor
neurons, several hormones
Acetylcholine and norepinephrine
released by autonomic motor
neurons; several hormones; local
chemical change; stretching
Capacity for regeneration Limited, via satellite cells Limited, under certain conditions Considerable (compared with other
muscle tissues, but limited compared
with epithelium), via pericytes
56. Mature skeletal muscle fibers cannot undergo mitosis.
Regeneration of Muscle Tissue
Hypertrophy Hyperplasia
Increase in cell size Increase in cell number
57. In a Nutshell
â The muscular system is made up of 3 types
of muscles: skeletal, cardiac, and smooth.
â Skeletal muscle cells are referred to as
muscle fibers and are multinucleated and
striated.
â Major functional properties of skeletal
muscle fibers include electrical excitability,
contractility, extensibility, and elasticity.
â The contractility of muscle fibers involves
the sliding of microfilaments in the skeletal
muscle fiber.
â Contraction is coupled with electrical
excitation of the skeletal muscle fiber.
58. In a Nutshell
â Impulses come from the nervous system to
the muscular system at the neuromuscular
junction (NMJ).
â Cardiac muscles differ from the skeletal
muscles because they are involuntary.
Although there are many similarities, cardiac
muscles also exhibit differences in structure
and function.
â Smooth muscles also differ from skeletal
muscles. They are also involuntary, and they
use different regulatory proteins during their
contractions.