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MCDB 111 -Midterm 1
Week 3 Material
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Cards (52)
What are the
3 types
of muscle cells?
skeletal
,
cardiac
,
smooth
Which muscle type has the
largest diameter
?
Skeletal
Which muscle type has the
longest length
?
Smooth
Which muscle type is
multinucleated
?
Skeletal
Which nervous system controls skeletal muscle?
somatic
nervous system (
voluntary
)
Motor neurons
Cell body in
spinal cord
or
brain stem
each one can
innervate
multiple muscle cells
acetylcholine
is neurotransmitter
neuromuscular junction
only
1
synapse per muscle cell (fiber)
always
excitatory
usually, one synaptic event will provoke
action potential
in the muscle fiber
End plate potential
a single firing of the
motor neuron
will cause a local
graded
potential
Muscle fibers
composed of multiple
myofibrils
that extend the
length
of the muscle fiber
Myofibrils
bundles of contractile
proteins
When does muscles contract?
When
myofibrils shorten
Sarcomere
consists of a bundle of
myofibrils
extending from one Z line to the next and composed of
overlapping actin
and myosin filaments
I
band
actin filaments only
A band
region of
overlapping myosin
and
actin
filaments
H
band
zone
within A-band
where myosin filaments
don't overlap
with actin
Z line
line separating two
neighboring sarcomeres
made up primarily of
alpha actinin
What protein makes up the
Z line
alpha-actinin
M line
band of
connections
between myosin filaments
primary protein is
myomesin
What protein makes up the
M line
myomesin
Contraction in sarcomere
sliding of actin over myosin which
shortens
structure
Titin
elastic protein which extends
from the Z line to the M line
and is linked to the
myosin filaments
to keep them centered
Nebulin
Is associated with the
actin filaments
and is essential for regulating
thin filament length
Dystrophin
links
actin
to the
extracellular matrix
and is a large
X-linked
protein
Duschenne Muscular Dystrophy
Individuals
homozygous
for loss of functional alleles of
dystrophin
Cell membranes of muscle fibers become
damaged
and leaky, leading to
death
of muscle cells and weakened skeletal muscles
Myasthenia gravis
Cause:
autoantibodies
to
nicotinic
AChRs
Symptoms:
Skeletal muscle weakness
Treatment:
Immunosuppressant
drugs
Spinal muscular atrophy
(
SMA
)
Cause:
mutations
in
SMN1 gene
Symptoms:
skeletal muscle weakness
and
atrophy
Treatments:
Antisense RNA
, gene therapy, and enhanced expression of
full length SMN2 protein
Rigor configuration
Starting position of muscle contraction cycle;
myosin
is bound tightly to
actin
Role of Ca2+ in skeletal muscle contraction
Ca2+ binds to
troponin
→ shifts
tropomysoin
→ exposes
myosin
binding site → muscle contraction
Where is calcium stored
sarcoplasmic reticulum
how is calcium released from sarcoplasmic reticulum?
interaction of two receptors (
DHP
receptor and
Ryanodine
receptor)
What are the mechanics of single-fiber contraction?
isometric
contraction and
isotonic
contraction
isometric contraction
Length
of muscle stays the
same
but
change
in
tension
isotonic contraction
tension
stays the
same
but
change
in
length
What are the
two types of isotonic contraction
?
concentric
contraction and
eccentric
contraction
Concentric contraction
type of isotonic contraction where
tension exceeds load
and causes muscle to
shorten
Eccentric contraction
type of isotonic contraction where
load exceeds tension
and causes muscle to be
stretched
out
Fatigue from
short term
exercise
lactic acid
build up
ATP
depletion
Fatigue from
long term
exercise
ryanodyne
R leakage
Glycogen
depletion
Central command
fatigue
What are the three types of muscle fibers?
slow oxidative
fibers,
fast oxidative-glycolytic
fibers, and
fast glycolytic
fibers
primary source of atp production in
slow oxidative fibers
oxidative phosphorylation
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