[Audio] Physiology of Muscle Tissue
Vyomkesh ameta Akash kumar
Shailesh pahadiya
Vikas. 

Scene 1

[Audio] Muscle Tissue Types
• Skeletal
– Attached to bones
– Nuclei multiple and peripherally located
– During development, 100 or more myoblasts, a type of mesodermal cell, fuse to form a skeletal muscle fiber.
– Striated, Voluntary and involuntary ( reflexes)
• Smooth
– Walls of hollow organs, blood vessels, eye, glands, skin
– Single nucleus centrally located
– Not striated, involuntary, gap junctions in visceral smooth
• Cardiac- In the heart only.
– Single nucleus centrally located
– Striations, involuntary, intercalated disks. 

Scene 2

– Attached to bones
– Nuclei multiple and peripherally located
– During development, 100 or more myoblasts, a type of

mesodermal cell, fuse to form a skeletal muscle fiber.

– Striated, Voluntary and involuntary (reflexes)

– Walls of hollow organs, blood vessels, eye, glands, skin
– Single nucleus centrally located
– Not striated, involuntary, gap junctions in visceral smooth

– Single nucleus centrally located
– Striations, involuntary, intercalated disks

[Audio] Muscular System Functions
• Body movement
• Maintenance of posture
• Respiration
• Production of body heat
• Communication
• Constriction of organs and vessels
• Heart beat. 

Scene 3

• Body movement
• Maintenance of posture
• Respiration
• Production of body heat
• Communication
• Constriction of organs and vessels
• Heart beat

[Audio] Properties of Muscle
• Contractility
– Ability of a muscle to shorten with force
– It DOES NOT produce force by lengthening/pushing!
• Excitability
– Capacity of muscle to respond to a stimulus
• Extensibility
– Muscle can be stretched to its normal resting length and beyond to a limited degree
• Elasticity
– Ability of muscle to recoil to original resting length after stretched. 

Scene 4

– Ability of a muscle to shorten with force
– It DOES NOT produce force by lengthening/pushing!

– Capacity of muscle to respond to a stimulus

– Muscle can be stretched to its normal resting length and

– Ability of muscle to recoil to original resting length

[Audio] Cardiac Muscle
• Branching cells
• One/ two nuclei per cell
• Striated
• Involuntary
• Medium speed contractions. 

Scene 5

(b) musch
Description: Branching. striated. generally trinucleate
that •nterügnate at speoalized juncticns (intercalated ciscs).
Function: As it contracts, it blood into the circulatit:n;
involuntary control.
Locatbn: ot heart.
cell
[tractions
discs
11
C2Ø1 Cummings. an imprint ot AdOson Wesley Lctvnan. mc.

• Branching cells
• One/two nuclei per cell
• Striated
• Involuntary
• Medium speed contractions

. . Intercalated disks Cross-striations Myocytes Nuclei. 

Scene 6

Intercalated disks
Cross-striations Myocytes
Nuclei

. . Microscopic Anatomy of Cardiac Muscle Nucleus Intercalated discs Cardiac muscle cell Gap junctions (a) Cardiac muscle cell Intercalated disc i Nucleus Sarcolemma (b) Fasciae adherens Mitochondrion Nucleus Mitochondrion T tubule Sarcoplasmic reticulum. 

Scene 7

Microscopic Anatomy of Cardiac Muscle
Nucleus Intercalated discs Cardiac muscle cell
Gap junctions
(a)
Cardiac
muscle cell
Intercalated
disc
i
Nucleus
Sarcolemma
(b)
Fasciae adherens
Mitochondrion
Nucleus
Mitochondrion
T tubule
Sarcoplasmic
reticulum

Scene 8

[Audio] Smooth Muscle
• Fusiform cells
• One nucleus per cell
• Nonstriated
• Involuntary
• Slow, wave-like contractions. 

Scene 9

(c) Smooth muscle
Spindle-shar»d calls with central nuclO•. colts
arranged closely to form sheets: no striatms.
Function: Propels or Objects LÜ'ine,
a baby) along internal passageways; inveuntary control.
Locatm Mostly in the
walls ot hollow organs.
SmcOth
muscle
cell
Nuclé
C2Ø1 Cummings. an imprint ot AdOson Wesley Lctvnan. mc.

• Fusiform cells
• One nucleus per cell
• Nonstriated
• Involuntary
• Slow, wave-like

Scene 10

Copyright © 2008 
Pearson Education, 
Inc., publishing as

Autonomic
neuron
varicosity
Gap junction
(b) Single-unit smooth muscle

[Audio] Copyright © 2008 Pearson Education, Inc., publishing as
Multi-Unit Muscle Figure 12.35a. 

Scene 11

Autonomic
neuron
varicosity
(a) Multi-unit smooth muscle

Scene 12

(a) Multi-unit smooth muscle
(b) Single-unit smooth muscle
Autonomic
neuron
varicosity
Autonomic
neuron
varicosity
Gap junction

[Audio] Skeletal Muscle
• Long cylindrical cells
• Many nuclei per cell
• Striated
• Voluntary
• Rapid contractions. 

Scene 13

• Long cylindrical cells
• Many nuclei per cell
• Striated
• Voluntary
• Rapid contractions

(a) Skeletal
CylindriCd, munjntße,ate cells:
Striations.
Function: Voluntary movement: locomotion: manipulation ot
environrn«lt; tacjal expressm; voluntary c:cntre.
muøes
attachaj to bones or txcasionaIlY
to Skin.
tqucléi
part Of
muscle
Copy#t C 2CM Benjamin Curnmiru. an imprint Ot Addison Lonwnan. Inc.

[Audio] Muscle Muscle fibers
Muscle fiber Myofibril
Sarcomere
Modified from McMahon, Muscles, Reflexes and Locomotion
Princeton University Press, 1984.
A little less than half of the body's mass is composed of skeletal muscle, with most muscles linked to bones by tendons through which the forces and movements developed during contractions are transmitted to the skeleton.
Structural hierarchy of skeletal muscle. 

Scene 14

Muscle
Muscle fibers
Muscle fiber
Myofibril
Sarcomere

Modified from McMahon, Muscles, Reflexes and Locomotion
Princeton University Press, 1984.

A little less than half of the body’s
mass is composed of skeletal 
muscle, with most muscles linked
to bones by tendons through which 
the forces and movements 
developed during contractions
are transmitted to the skeleton.

[Audio] Muscle Proteins
• Contractile Proteins ( actin and myosin)
• Regulatory Proteins (i.e. tropomyosin and troponin)
• Structural Proteins (i.e. Titin). 

Scene 15

• Contractile Proteins (actin and myosin)

• Regulatory Proteins (i.e. tropomyosin and

[Audio] Myosin is a hexamer: 2 myosin heavy chains 4 myosin light chains C terminus
2 nm
Coiled coil of two a helices
Myosin is a molecular motor Myosin S1 fragment crystal structure Ruegg et al., ( 2002) News Physiol Sci 17: 213- 218. NH2-terminal catalytic
(motor) domain neck region/ lever arm Nucleotide binding site
Myosin head: retains all of the motor functions of myosin, i.e. the ability to produce movement and force.
Modified from Vander, Sherman, Luciano Human Physiology, McGraw-Hill.. 

Scene 16

Myosin is a hexamer:
2 myosin heavy chains
4 myosin light chains

Actin-binding sites
'lar motor
ATP binding site
Light chains
of two a helices
Heavy chains
O The 'EGraw-HlIl Coal —lea.
ATP
binding
site

Upper 50kDa domain
Actin binding
domain
Nucleotide
binding site
N-term.
Converter
domain
C-term.
Regulatory
light chain
Essential
light chain

Myosin head:  retains all of the motor functions of myosin,
i.e. the ability to produce movement and force.

Modified from Vander, Sherman, Luciano 
Human Physiology, McGraw-Hill.

[Audio] Working stroke produced by opening and closing of the nucleotide binding site, resulting in rotation of the regulatory domain ( neck) about a fulcrum
( converter domain).
Sub-nanometer rearrangements at active site are geared up to give 510 nm displacement at the end of the lever arm.
Hypothetical model of the swinging lever arm Ruegg et al., ( 2002) News Physiol Sci 17: 213- 218.. 

Scene 17

Working stroke produced by 
opening and closing of the
nucleotide binding site, resulting
in rotation of the regulatory 
domain (neck) about a fulcrum
(converter domain).

Sub-nanometer rearrangements at
active site are geared up to give 5-
10 nm displacement at the end of 
the lever arm.

Hypothetical model of the
swinging lever arm

Ruegg et al., (2002) News Physiol Sci 17:213-218.

[Audio] Skeletal Muscle
• Produce movement
• Maintain posture & body position
• Support Soft Tissues
• Guard entrance / exits
• Maintain body temperature
• Store nutrient reserves
• Makes up aprox. 40% of body weight. 

Scene 18

• Produce movement
• Maintain posture & body position
• Support Soft Tissues
• Guard entrance / exits
• Maintain body temperature
• Store nutrient reserves
• Makes up aprox. 40% of body weight

. . TABLE 12.2 Comparison of Skeletal, Smooth, and Cardiac Muscle Property Striations (sarcomeres) Actin and myosin Level of control Neural input Neuroeffector junction Hormonal control Source of calcium Regulatory protein that binds calcium Gap junctions Pacemaker activity Myosin ATPase activity Recruitment Skeletal Yes Yes Voluntary Somatic Neuromuscular junction—specific None Troponin Fastest Yes Smooth (single-unit) No Yes Involuntary Autonomic Varicosities—diffuse Several, depending on location SR and ECF Calmodulin Yes Yes Slowest No Smooth (multi-unit) No Yes Involuntary Autonomic Varicosities—diffuse Several, depending on location SR and ECF Calmodulin No (or few) No Slowest Yes Cardiac Yes Yes Involuntary Autonomic Varicosities—diffuse Epinephrine SR and ECF Troponin Yes Yes Intermediate. 

Scene 19

TABLE 12.2
Comparison of Skeletal, Smooth, and Cardiac Muscle
Property
Striations (sarcomeres)
Actin and myosin
Level of control
Neural input
Neuroeffector junction
Hormonal control
Source of calcium
Regulatory protein that
binds calcium
Gap junctions
Pacemaker activity
Myosin ATPase activity
Recruitment
Skeletal
Yes
Yes
Voluntary
Somatic
Neuromuscular
junction—specific
None
Troponin
Fastest
Yes
Smooth (single-unit)
No
Yes
Involuntary
Autonomic
Varicosities—diffuse
Several, depending
on location
SR and ECF
Calmodulin
Yes
Yes
Slowest
No
Smooth (multi-unit)
No
Yes
Involuntary
Autonomic
Varicosities—diffuse
Several, depending
on location
SR and ECF
Calmodulin
No (or few)
No
Slowest
Yes
Cardiac
Yes
Yes
Involuntary
Autonomic
Varicosities—diffuse
Epinephrine
SR and ECF
Troponin
Yes
Yes
Intermediate

[Audio] Skeletal Muscle Structure. . . Skeletal Muscle Structure. 

Scene 20

Epimysium
Muscle fascicle
Endomysium
Perimysium
SKELETAL MUSCLE
(organ)
Epimysium
Blood vessels
and nerves
Nerve
Muscle fibers
Blood vessels
MUSCLE FASCICLE
(bundle of cells)
Mitochondria
Perimysium
Muscle fiber
Endomysium
Capillary
Tendon
Perimysium
Endomysium Sarcolemma .
Myofibril
Axon —9
Sarcoplasm
MUSCLE FIBER
(cell)
Endomysium
Myosatellite
cell
Nucleus

[Audio] - Sarcoplamsic Reticulum ( SR): Fluid filled sacks that encircle each myofibril. It is similar to the smooth endoplasmic reticulum in other cells. -Terminal cisterns ( cistern-reservoir): Dilated ends of SR, butt against T tubule from both sides. -T bubule and 2 terminal cisterns on either side of it form a TRIAD. -In relaxed muscle fiber, SR stores calcium ions
- Release of calcium ions from terminal cisterns of SR triggers muscle contraction.. 

Scene 21

-Sarcoplamsic Reticulum (SR): Fluid filled sacks that encircle each 
myofibril. It is similar to the smooth endoplasmic reticulum in 
other cells. 
-Terminal cisterns (cistern-reservoir): Dilated ends of SR, butt 
against T tubule from both sides. 
-T bubule and 2 terminal cisterns on either side of it form a 
TRIAD. 
-In relaxed muscle fiber, SR stores calcium ions
-Release of calcium ions from terminal cisterns of SR triggers 
muscle contraction.

[Audio] Skeletal Muscle Fiber. . . Skeletal Muscle Fiber. 

Scene 22

MUSCLE FIBER
Myofibril
Myofibril
Sarcolemma
Mitochondria
Sarcolemma
Thin filament
Thick filament
000
0 000 00
o
0000 0000
Sarcoplasm
Triad Sarcoplasmic
reticulum
Nuclei
Terminal
cisterna
Sarcolemma
Sarcoplasm
Myofibrils

[Audio] Connective Tissue, Nerve, Blood Vessels
• Connective tissue
– External lamina
– Endomysium
– Perimysium
– Fasciculus
– Epimysium
• Fascia
• Nerve and blood vessels
– Abundant. 

Scene 23

– External lamina
– Endomysium
– Perimysium
– Fasciculus
– Epimysium

Copyn#V C' The McGrawHiII COTW•mies, req•uled reproduction "*lay.
Epimysium (fascia;
surrounds muscles)
Axon of motor neuron
Sarcolemma
Perimysium
(surrounds fasciculi)
Endomysium (surrounds
muscle fibers)
Muscle fiber
Artery
Nerve
Vein
Fasciculus
Capillary
Synapse or
neuromuscular
junction
Muscle fiber

[Audio] -Some myoblasts (the cells that congegrate to form skeletal muscle fibers in the embryo) remain, they are referred to as satellite cells. - Satellite cells maintain ( repair, etc.) skeletal muscle fibers. They can divide and they can fuse with one another and with muscle fibers to repair them, etc.
-Mature muscle fibers range from between 10 to 100 micrometers in diameter. The "typical" muscle fiber is around 4 inches (10cm). There are muscle fibers that are up to a foot ( 30cm) long.. 

Scene 24

-Some myoblasts (the cells that congegrate to form skeletal 
muscle fibers in the embryo) remain, they are referred to as 
satellite cells. 
-Satellite cells maintain (repair, etc.) skeletal muscle fibers. 
They can divide and they can fuse with one another and with 
muscle fibers to repair them, etc.

-Mature muscle fibers range from between 10 to 100 
micrometers in diameter. The “typical” muscle fiber is 
around 4 inches (10cm). There are muscle fibers that are 
up to a foot (30cm) long.

[Audio] Embryologic origin:. . . Embryologic origin:. 

Scene 25

Myoblasts
Muscle
develop through
the fusion of
mesodermal cells
called myoblasts.
Satellite cell
Nuclei
Immature
muscle

[Audio] -The plasma membrane of a muscle cell is referred to as the sarcolemma. The nuclei of skeletal muscle fibers lie just below the sarcolemma.
-There are numerous invaginations of the sarcolemma that tunnel from the surface of the fiber to the center of the muscle fiber. They are open to the outside of the fiber and filled with interstitial fluid. These are called transverse tubules or T tubules.
- Action potentials propagate along sarcolemma and T tubules, this insures a uniform contraction of a given muscle fiber.
- Sarcoplasm: cytoplasm of the muscle fiber. - Glycogen is abundant in the sarcoplasmplasm that can quickly be split via hydrolysis into glucose which can be used to generate ATP.. 

Scene 26

-The plasma membrane of a muscle cell is referred to as the 
sarcolemma. The nuclei of skeletal muscle fibers lie just below the 
sarcolemma.

-There are numerous invaginations of the sarcolemma that tunnel 
from the surface of the fiber to the center of the muscle fiber. They 
are open to the outside of the fiber and filled with interstitial fluid. 
These are called transverse tubules or T tubules.
-Action potentials propagate along sarcolemma and T tubules, this 
insures a uniform contraction of a given muscle fiber.
-Sarcoplasm: cytoplasm of the muscle fiber. 
-Glycogen is abundant in the sarcoplasmplasm that can quickly be 
split via hydrolysis into glucose which can be used to generate 
ATP.

[Audio] - Myoglibin is also abundant in the sarcoplasm. Myoglobin is red in color. It is found only in muscle tissue. It binds free oxygen molecules that diffuse into muscle fibers from interstitial fluid, which obtained the free oxygen from the capillaries in the blood.
- Mitochondria are abundant in muscle tissue. They lie very close to muscle proteins that utilize ATP during muscle contractions.
- Myofibrils: contractile element of the skeletal muscle fibers. -They are about 2 micrometers in diameter and extend the entire length of the muscle fiber that they are in.
-Myofibrils have prominent striations ( stripes), thus the name " striated muscle tissue." These striations make the entire muscle appear striated.. 

Scene 27

-Myoglibin is also abundant in the sarcoplasm. Myoglobin is red in 
color. It is found only in muscle tissue. It binds free oxygen 
molecules that diffuse into muscle fibers from interstitial fluid, 
which obtained the free oxygen from the capillaries in the blood.

-Mitochondria are abundant in muscle tissue. They lie very close to 
muscle proteins that utilize ATP during muscle contractions.

-Myofibrils: contractile element of the skeletal muscle fibers. 
-They are about 2 micrometers in diameter and extend the entire 
length of the muscle fiber that they are in.

-Myofibrils have prominent striations (stripes), thus the name 
“striated muscle tissue.” These striations make the entire muscle 
appear striated.

. . Striations:. I band I band A band H zone Zone ot overla Sarcomere A band M line Z line Z line Titin Thin filament Thick filament Z line M line Zone of overlap Sarcomere. 

Scene 28

I band
I band
A band
H zone
Zone ot overla
Sarcomere
A band
M line
Z line
Z line
Titin
Thin
filament
Thick
filament
Z line
M line
Zone of overlap
Sarcomere

. . I band (a) A band H band Zone of overlap M line Sarcomere Sarcomere Z line Titin Thin Thick filament filament. 

Scene 29

I band
(a)
A band
H band
Zone of overlap M line
Sarcomere
Sarcomere
Z line Titin
Thin
Thick
filament filament

[Audio] - Myofibrils are composed of filaments. These are 1 to 2 micrometers long. The diameter of the THIN FILAMENTS is about 8 nanometers and those of the THICK FILAMENTS are around 16 nanometers. -In general, there are 2 thin filaments for each thick filament. - Filaments inside of the miofibril do not extend the entire muscle length. They are arranged in small compartments known as sarcomeres. These are the basic functional unit of the miofibril.
-Z discs are narrow plate-shaped regions of dense material that separate sarcomeres from each other.. 

Scene 30

-Myofibrils are composed of filaments. These are 1 to 2 
micrometers long. The diameter of the THIN FILAMENTS is 
about 8 nanometers and those of the THICK FILAMENTS are 
around 16 nanometers. 
-In general, there are 2 thin filaments for each thick filament. 
-Filaments inside of the miofibril do not extend the entire muscle 
length. They are arranged in small compartments known as 
sarcomeres. These are the basic functional unit of the miofibril.
-Z discs are narrow plate-shaped regions of dense material that 
separate sarcomeres from each other.

[Audio] -Thick and thin filaments overlap one another to varying degrees. This is dependent on whether the muscle is contracted, relaxed or stretched. -The pattern of this overlap, that consists of a variety of zones and bands creates the striations that are characteristic of skeletal muscle.. 

Scene 31

-Thick and thin filaments overlap one another to varying degrees. 
This is dependent on whether the muscle is contracted, relaxed or 
stretched. 
-The pattern of this overlap, that consists of a variety of zones and 
bands creates the striations that are characteristic of skeletal 
muscle.

[Audio] Organization of myofilaments I:. . . Organization of myofilaments I:. 

Scene 32

I band
Z line
A band
SARCOMERE
Contains:
Thick filaments
M line
—•——..—-U.UY
Titin
Thin filaments
Z line

[Audio] Organization of myofilaments II:. . . Organization of myofilaments II:. 

Scene 33

Connectin
filaments
Myofibril
Attachment
of titin
Z line
Sarcomere
Thick filament
Titin
filament
M line
Thin filament
ooo
I band
o ooo
0 0 0 00
0 00
H zone
0.0.0
Zone of overlap

. . Myofibril LTJ Z line Sarcomere H band nr UUUUU nnr M line Actinin Z line Titin (a) Z line and thin filaments Troponin Active site Nebulin Tropomyosin G-actin molecules F-actin strand (b) Thin filament. 

Scene 34

Myofibril
LTJ
Z line
Sarcomere
H band
nr
UUUUU
nnr
M line
Actinin Z line Titin
(a) Z line and thin filaments
Troponin Active site Nebulin Tropomyosin G-actin
molecules
F-actin
strand
(b) Thin filament

. . Myofibril (c) Thick filaments LTJ Z line M line Sarcomere H band nr UUUUU nnr M line Myosin tail (d) Myosin molecule Titin Myosin head Hinge. 

Scene 35

Myofibril
(c) Thick filaments
LTJ
Z line
M line
Sarcomere
H band
nr
UUUUU
nnr
M line
Myosin tail
(d) Myosin molecule
Titin
Myosin
head
Hinge

[Audio] Sliding Filament Model I:
• Actin myofilaments sliding over myosin to shorten sarcomeres
– Actin and myosin DO NOT change length
– Shortening sarcomeres responsible for skeletal muscle contraction
• During relaxation, sarcomeres lengthen. 

Scene 36

• Actin myofilaments sliding over myosin to

shorten sarcomeres
– Actin and myosin DO NOT change length
– Shortening sarcomeres responsible for skeletal

• During relaxation, sarcomeres lengthen

[Audio] Z line
Z line. . . . Z line
Z line. 

Scene 37

[Audio] -Some components of muscle tissue are elastic. They stretch slightly before they transfer tension generated by sliding filaments.
-Elastic components include titin molecules, connective tissue around muscle fibers ( endomysium, perimysium and epimysium, as well as tendons.. 

Scene 38

-Some components of muscle tissue are elastic. They stretch slightly 
before they transfer tension generated by sliding filaments.

-Elastic components include titin molecules, connective tissue around 
muscle fibers (endomysium, perimysium and epimysium, as well as 
tendons.

[Audio] -As skeletal muscles shorten, the elastic components are stretched and become taut. The tension then pulls the body part that it is attached to, resulting in movement.
- Contractions do not always result in shortening of muscle fibers: Isometric contractions are where the myosin heads rotate and generate tension but thin filaments are unable to slide toward M line due to excessive opposing tension. Isotonic contractions result in the shortening of the muscle.. 

Scene 39

-As skeletal muscles shorten, the elastic components are stretched 
and become taut. The tension then pulls the body part that it is 
attached to, resulting in movement.

-Contractions do not always result in shortening of muscle fibers: 
Isometric contractions are where the myosin heads rotate and 
generate tension but thin filaments are unable to slide toward M line 
due to excessive opposing tension. Isotonic contractions result in the 
shortening of the muscle.

[Audio] Sarcomere Relaxed. . . . Sarcomere Relaxed. 

Scene 40

[Audio] Sarcomere Partially
Contracted. . . . Sarcomere Partially. 

Scene 41

[Audio] Sarcomere Completely
Contracted. . . . Sarcomere Completely. 

Scene 42

Scene 43

[Audio] Sliding filament model II:. . . Sliding filament model II:. 

Scene 44

Sarcomere
at rest
Contraction and
filament sliding

[Audio] Sarcomere Shortening. . . Sarcomere Shortening. 

Scene 45

O The McGraw-Hill
A nd
Z disk
Relaxed
muscle
Myosin myofilament Actin
reproduction display.
I band
Z disk Z disk
Z disk
Contracting
muscle
Contracting
muscle
move toward
as Z disks move
toward each other
H zone narrows I band A baåd does
narrows not narrow
A band
Fully contracted
muscle
H zone
I band
A band
I band A band remains
narrows unchanged
further

[Audio] Structure of Actin and Myosin. . . Structure of Actin and Myosin. 

Scene 46

Cown$t O The McGraw-Hill Cct•roanies, Inc. Permission fix reproduction display.
Sarcomere
Cross-bridge
Actin
(a)
Z disk myofilament
Myosin
myofilament
Tropomyosin
G actin
molecules
(b)
Troponin
Z disk
Rod portion
Heads
Coiled-portion of
the two u helices Light chains
Two heavy chains Hinge region
of myosin
Myosin
molecule
F actin strands Active site
(c) Actin myofilament (thin)
Myosin myofilament (thick)

. . d dav unov u!soKtuod0J1 d dav u!uodou peeq u!soKn auanoouvs ONUS2U t.Jt.Ä. 

Scene 47

d
dav
unov
u!soKtuod0J1
d
dav
u!uodou
peeq u!soKn
auanoouvs ONUS2U
t.Jt.Ä

. . STEP I ADP ACTIVE-SITE EXPOSURE Sarcoplasm Active site Ca2+ ADP. 

Scene 48

STEP I
ADP
ACTIVE-SITE EXPOSURE
Sarcoplasm
Active
site
Ca2+
ADP

. . STEP 2 ADP Ca2+ CROSS-BRIDGE FORMATION ADP ca2+. 

Scene 49

STEP 2
ADP
Ca2+
CROSS-BRIDGE FORMATION
ADP ca2+

. . STEP 3 PIVOTING OF MYOSIN HEAD Ca2+ ADp+ p. 

Scene 50

STEP 3
PIVOTING OF MYOSIN HEAD
Ca2+
ADp+ p

muscle_tissue_powerpoint_that56684531

Scene 0

avatar

– Nuclei multiple and peripherally located

– During development, 100 or more myoblasts, a type of mesodermal cell, fuse to form a skeletal muscle fiber.

– Walls of hollow organs, blood vessels, eye, glands, skin

– Not striated, involuntary, gap junctions in visceral smooth

– Striations, involuntary, intercalated disks

– Ability of a muscle to shorten with force

– It DOES NOT produce force by lengthening/pushing!

– Muscle can be stretched to its normal resting length and beyond to a limited degree

– Ability of muscle to recoil to original resting length after stretched

Muscles, Reflexes and Locomotion
Princeton University Press

Modified from McMahon, Muscles, Reflexes and Locomotion

A little less than half of the body's mass is composed of skeletal  muscle, with most muscles linked to bones by tendons through which  the forces and movements  developed during contractions are transmitted to the skeleton.

• Regulatory Proteins (in other words tropomyosin and troponin)

• Structural Proteins (in other words Titin)

retains all of the motor functions of myosin, in other words the ability to produce movement and force.

Working stroke produced by  opening and closing of the nucleotide binding site, resulting in rotation of the regulatory  domain (neck) about a fulcrum

Sub-nanometer rearrangements at active site are geared up to give 510 nm displacement at the end of  the lever arm.

Hypothetical model of the swinging lever arm

Ruegg and others, (2002) News Physiol Sci 17:213-218.

Fluid filled sacks that encircle each  myofibril

It is similar to the smooth endoplasmic reticulum in  other cells

Dilated ends of SR, butt  against T tubule from both sides

-T bubule and 2 terminal cisterns on either side of it form a

-In relaxed muscle fiber, SR stores calcium ions

-Release of calcium ions from terminal cisterns of SR triggers  muscle contraction.

-Some myoblasts (the cells that congegrate to form skeletal  muscle fibers in the embryo) remain, they are referred to as  satellite cells