BIO21010 MUSCLE TISSUE
I.Introduction
A.three types
1.skeletal muscle
a.over boney skeleton
b.longest muscle
fibers
c.striations
d.voluntary control
2.cardiac
a.only heart
b.striated
c.involuntary
d.contraction at
steady rate by heart's pacemaker
3.smooth
a.walls of hollow
organs
b.stomach,bladder,respiratory
blood
vessels
c.nonstriated
d.involuntary
e.slow, sustained
contractions
B.functions
1.skeletal
a.movement
b.posture
c.stabilizes joints
d.thermogenesis
e.others (speech,
vision)
2.smooth
a.contract and relax
to move substances
through
body
II.functional properties
of muscle
A.excitability
1.receives, responds to stimuli
B.contractility
1.shortens when stimulated
C.extensibility
1.stretch
D.elasticity
1.recoil
III.Skeletal Muscle (Sk M)
A.muscle
cells
1.long, muscle fibers
2.myo- and sarco- refer to muscles
B.Superficial
fascia
1.Connective tissue (CT)
coverings
2. between hypodermis and
muscle
C. Deep fascia
3.endomysium
a.loose CT
b.around a muscle
fiber
4.perimysium
a.bundles of muscle
fibers form a fascicle
b.perimysium covers a
fascicle
5.epimysium
a.covers many
fascicles bundled together
C.Connective
tissue attachments of muscle - Tendons
1.origin
a.on bone which is
less movable
2.insertion
a.on the movable bone
E. Vasculature
1.arteries take blood from
heart to muscles and veins take blood from muscles to heart
2. capillaries are smallest
vessels and are near each muscle cell
3. blood needed to deliver
oxygen and nutrients
F. Nerves
1. innervation
of each muscle cell
2. neuromuscular
junction
a. axon
branch from a somatic motor neuron meets the muscle cell
b. synapse
3. axons to
skeletal muscle are from a somatic motor neuron and are myelinated to send the
signal fast
G.Histology of skeletal
muscle fiber
1.plasma membrane
b.sarcolemma
2.T-Tubules
a.tube extending from
sarcolemma into cell
3. cytoplasm
a.sarcoplasm
3.glycogen
a.storage of glucose
units
4.myoglobin
a.red pigment that
stores oxygen
b.similar to
hemoglobin
5.mitochondria
a.more if active
6. sarcoplasmic reticulum
(SR)
b.storage of calcium
in SER
b.regulates
calcium
7.myofibrils
a.densely packed
b.contractile elements
c. SR surrounds
myofibril
8.sarcomere
a.contractile unit of
myofibril
b.thick filament
(1)protein is myosin
c.thin filament
(1)protein is actin
d.A band
(1)all thick filaments
(2)some overlap of thin
e.I band
(1)only thin filaments
f.H zone
(1)only thick filaments
g.Z line
(1)connecting thin
(2)Z to Z is the sarcomere
h.M line
(1)middle of thick
H. Specializations for contraction
1.myofibril
a.made of sarcomere
units
(1)sarcomere units are made
of filaments also
called myofilaments
2.Thick filaments
a.each myosin molecule
has a tail and 2 heads
b.forms crossbridges
with thin filaments during
contraction
3.Thin filaments
a.actin and troponin
and tropomyosin
b.troponin binds to
calcium
c.all help to bind
thin filaments to thick
4. Calcium
in SR and higher outside cell
5. T-tubules
help in releasing calcium
I.Sliding Filament theory
1.for muscle contraction
2.sarcomeres shorten
3.distance between 2 Z bands decreases
4.thin filament slides past thick filaments
and overlaps
5.calcium binds to troponin and changes the
shape of thin filaments to pull to
medially in the sarcomere
6.formation of cross bridges between myosin
heads and actin pulls thin filament more center of sarcomere
7.requires ATP to release myosin binding
8.rigor mortis
a.cross bridge
detachment requires ATP
b.muscles stay
contracted without ATP
J. Depolarization necessary for contraction
1.resting sarcolemma
a.polarized
2.nervous impulse from
brain
3.axon goes to skeletal muscle
a. each muscle fiber
has one axon branch synapsing near center of fiber
4.terminal end of axon is
located at the muscle
a.neuromuscular
junction
b.forms a synaptic
cleft
5.a substance is released
in the synaptic cleft to get
the message across (for the muscle to contract)
a.neurotransmitter
(1)acetylcholine on Sk M
6.The sarcolemma
depolarizes
a.sodium rushes in and
at given mv calcium channels open Ca
enters muscle fiber
7.The depolarization
extends into T-tubules
a.this acts as signal
to SER to release calcium
8.Excitation-contraction
coupling
a.links electrical
signal to contraction
9.enzyme degrades
acetylcholine and signal stops
a.acetylcholine
esterase
10.sarcolemma repolarizes,
muscle relaxes
a.potassium moves back
into cell
11.refractory period
a.muscle cannot be
stimulated to contract until it is repolarized
12.Draw a graph that
represents the association between the action potential and muscle contraction
label
= stimulus applied, latent period, contraction, relaxation
K .Muscle metabolism
1.ATP
a.for cross bridge
movement and detachment
b.ATP for calcium pump
2.uses stored ATP first
3.ADP interacts with creatine phosphate
creatine phosphate +ADP->
creatine + ATP
4.aerobic respiration
a.making ATP with
oxygen present
b.from blood and
myoglobin
5.anaerobic respeiration
a.in absence of oxygen
b.lactic acid builds
up in working muscles
(1)contributes to muscle
fatigue
(2)oxygen debt
(a)must be repaid by
restoring oxygen as myoglobin
6.carbon dioxide is waste
product of cell metabolism
L.Types of contraction
1.motor unit
athe motor neuron
and all the muscle fibers it innervates that will contract when stimulated
(1)want a smooth sustained contraction
a.threshold stimulus
(1)nervous impulse must be
of sufficient strength for muscle to respond
(2)will get no greater
contraction of muscle
if exceed threshold strength
3.muscle twitch
(a)1 stimuli
(b)quick
contraction, relaxation
4.tetany
a. many successive
impulses delivered to muscle to get a
smooth sustained contraction
b. nerves normally
fire this way to keep a longer
contraction
5.muscle tone
a.keeps muscle in
slightly contracted form
b.posture
c.stabilizes joints
6. isotonic contraction
a.muscle shortens to
do work
7.isometric contraction
a.contraction without
much shortening
b.developes tension
c.but does not move
the load
M.Force of contraction
depends on
1.# muscle fibers
d.more fibers greater
contraction
2.size
a.larger, greater
contraction
b.hypertrophy
3.series elastic elements
a.noncontractile
elements
b.connective tissue
4.degree of muscle
stretch
a.too much or too
little actin/myosin won't bind
5.load
a.work of muscle
b.muscle attached to
bone always has a load
c.greater load, slower
contraction
N.Different muscle fiber
types
1. Slow oxidative (SO)
a. resist
fatigue
b. mitochondria
for aerobic metabolism
c. red,
more myoglobin
2. Fast Oxidative-glycolytic
(FOG)
a. glycogen
b. anaerobic
metabolism
3. Fast glycolytic (FG)
a. largest
diameter fiber and most powerful contraction
b. white