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3 kinds of muscle
- skeletal muscle
- cardiac muscle
- smooth muscle
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what is skeletal muscle? what does it connect?
voluntary muscle tissue
connects one bone to another via tendon
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tendon v. ligament
tendon = muscle to bone
ligament = bone to bone
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agonist and antagonist
agonist = muslce repsonsible for movement (contracts)
antagonist = second muscle (stretches)
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when antagonist contracts, in what direction does the muscle move?
opposite direction as to when it was move when the agonist was contracted
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synergistice muscle
assists agonist by stabilizing the origin bone
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Skeletal muscle can squeeze blood and lymph vessels, what advantages does this have?
aids circulation
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muscle is like what kind of machine?
lever:
muscle = leverage to apply force to the bone to move
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Is greater or lesser force required to move the bone?
greater
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contraction of skeletal muscle - releases energy?
yes, heat!
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what is shivering?
rapid contraction of skeletal muscle to warm the body
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skeletal muscle contraction: sacromere
composed of thick and thin filaments
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sacromere lumen is filled with
Ca2+ ions
mitochondria and nuceli
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does sacromere have a single or many nuclei?
many -
only type of muscle like this
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thick and thin filament - actin and myosin
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thick = myosin
thin = actin
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contraction involves
5 stage cycle -
actin and myosin work together to.....
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1st stage in contraction
preventing myosin head from bonding-
tropomyosin covers the active site on actin
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why would we not want the myosin head to bind?
head has high energy position with P and ADP attached
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2nd stage in contraction
exposing the active site
troponin pulls the tropomyosin back
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3rd stage in contraction
myosin head expels a P and ADP (low energy position)
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what is this 3rd stage called (when myosin head expels a P and ADP)?
power stroke
it causes shortening of the sacromere and the muscle contraction
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4th stage of contraction
ATP reaches to myosin head from active site
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5th stage of contraction
ATP splits into P and ADP causing myosin head to cock in high-energy position
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overall scheme of contraction
tropomyosin covers active site and has troponin attached
when Ca2+ bind to troponin, it changes conformation and moves the tropomyosin
mvmt. opens myosin binding sites on the actin
when they bind the move (contract)
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How is the muscle contraction initiated?
action potential
neron attaches to muscle cell and releases neurotransmitter into synapse
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what neurotransmitter is released into begin muscle contraction?
ACh
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how does the action potential reach deep into the muscle?
T-tubules
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stimulated T-tubules spread action potentially rapidly to
sacroplasmic reticulum
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what does an activated sacroplasmic reticulum do
becomes permeable to Ca2+ ions
calcium begins 5-stage cycle
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what happens to Ca2+ after contraction?
it is actively pumped back to sacroplasmic reticulum
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in contraction what sections reduce in size and which stay the same?
H and I get smaller
A band doesn't change
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does skeletal muscle contract all at once?
no, single neuron innervates each muscle fiber
they contract independently of each other
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skeletal muscle types
1. slow oxidative muscle
2. fast oxidative muscle
3. fast glycolytic fibers
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slow-twitch: color, rate to split ATP
red - large amounts of myoglobin
larger mitochondria
split ATP at a slower rate
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slow to split ATP means....
- slow to fatigue
- slow contraction velocity
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fast-twitch: color? rate to split ATP
red
split ATP at high rate
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split ATP at fast rate
fast contraction
resistant to fatigue
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fast-glycolytic color and rate of contraction
white (b/c of low myoglobin content)
- contract very rapidly
- contain large amounts of glycogen
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what does myoglobin do?
stores O2 inside muscle cell
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do muscle cells undergo mitosis?
no
instead, change over time when exposed to repetitive contraction
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cardiac muscle: striate? nuclei, mitochondria? voluntary?
striated
contains only 1 nucleus
much more mitochondria - stronger
involuntary
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how are action potentials spread in a cardiac muscle?
gap junctions
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smooth muscle: voluntary? nuclei?
involuntary - innervated by ANS
single nucleus
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does smooth muscle contain thick and thin filaments if it has only one nucleus?
yes, but not organized into sacromeres
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intermediate filaments and dense bodies in smooth muscle: picture
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2 types
single unit and multi unit
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single unit
cells connected by gap junctions spreading action potential from a single neuron
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single unit: do cells contract separately? where are they found?
no contracts as a whole
intestines, arteries, veins, stomach, uterus, urinary bladder
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multi unit
each unit fiber is directly attached to a neuron
fibers contract independently
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is bone living tissue?
yes
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3 types of cells are:
what are they surrounded by?
surrounded by extensive matrix
- 1. osteoblasts
- 2. osteocytes
- 3. osteoclasts
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osteoblasts
secrete collagen and organic compounds that form bone
differentiate into osteocytes
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do osteoblasts undergo mitosis?
no
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osteocytes
exchange nutrients and waste with blood
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do osteocytes undergo mitosis?
no
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osteoclasts
- reabsorb bone matrix,
- releasing materials back into blood
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where do osteoclasts develop from
white blood cells: monocytes
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