ap biology february 6, 2011 bellringer list the 3 types of muscle tissue and provide 1 unique...
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AP Biology
February 6, 2011 BellRinger
List the 3 types of muscle tissue and provide 1 unique feature of each
Objective Describe how the structure of muscle
tissue makes it responsive to the nervous system
Homework Chp 45 notes (tomorrow) Chp 51 notes (Wed)
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Animal LocomotionWhat are the advantages of locomotion?
motilesessile
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Lots of ways to get around…
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Lots of ways to get around…
mollusk mammalbird reptile
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Lots of ways to get around…
bird arthropodmammal bird
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Muscle
voluntary, striated
involuntary, striated
auto-rhythmic
involuntary,
non-striated
evolved first
multi-nucleated
digestive systemarteries, veins
heartmoves bone
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How is an orange similar to the organization of skeletal muscle?
Use the image on pg. 180 of the anatomy book to relate the organization of muscle to an orange.
Connective Tissue Wrappings of Skeletal Muscle
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Connective Tissue Wrappings of Skeletal Muscle
Figure 6.1
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tendon
skeletal muscle
muscle fiber (cell)
myofilamentsmyofibrils
plasma membrane
nuclei
Organization of Skeletal muscle
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Human endoskeleton
206 bones
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Muscles movement Muscles do work by contracting
skeletal muscles come in antagonistic pairs flexor vs. extensor
contracting = shortening move skeletal parts
tendons connect bone to muscle
ligaments connect bone to bone
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Observation of muscle tissue In groups of 4, you will observe the gross
structures (structures you can see with your eye) of muscle tissue
Pick up a dissection tray, tools, and a chicken wing
On your wing, identify and sketch the following structures: Tendon Ligament Opposing muscle groups Muscle attachments to the bone
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Muscles How did you determine a tendon from a
ligament? How are the bones of a wing able to
move one way, then the other? Where were most of the muscle
attachments…close to the joint, far away, or somewhere in the middle?
Why does the location of muscle attachment affect strength and range of movement?
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Structure of striated skeletal muscle Muscle Fiber
muscle cell divided into sections = sarcomeres
Sarcomere functional unit of muscle
contraction alternating bands of
thin (actin) & thick (myosin) protein filaments
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Muscle filaments & Sarcomere
Interacting proteins thin filaments
braided strands actin tropomyosin troponin
thick filaments myosin
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Thin filaments: actin Complex of proteins
braid of actin molecules & tropomyosin fibers tropomyosin fibers secured with troponin molecules
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Thick filaments: myosin Single protein
myosin molecule long protein with globular head
bundle of myosin proteins:globular heads aligned
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Thick & thin filaments Myosin tails aligned together & heads pointed
away from center of sarcomere
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How do muscles contract? Before we discuss the process of
muscle contraction, you will model it Each team of 2 students will grab
3 pieces of licorice 4 pipe cleaners 2 match sticks
What does the licorice represent? What do the pipe cleaners represent? What do the match sticks represent?
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Learning Check Using textbook, identify the following
on your model: I-band A-band H zone
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Shortening sarcomere Myosin pulls actin chain
along toward center of sarcomere
Sarcomere shortens (Z lines move closer together)
What limits the distance the sarcomere can contract?
Muscle contracts energy from:
ATP glycogen
Z Z
Z Z
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Learning Check Why are muscles cells said to contract
if the muscle fibers themselves do not actually shorten?
Muscle contraction
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Closer look at muscle cell
multi-nucleated
Mitochondrion
Sarcoplasmicreticulum
Transverse tubules(T-tubules)
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Muscle cell organelles Sarcoplasm
muscle cell cytoplasm contains many mitochondria
Sarcoplasmic reticulum (SR) organelle similar to ER
network of tubes stores Ca2+
Ca2+ released from SR through channels Ca2+ restored to SR by Ca2+ pumps
pump Ca2+ from cytosol pumps use ATP
Ca2+ ATPase of SR
ATP
There’sthe restof theATPs!
But whatdoes theCa2+ do?
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Muscle at rest Interacting proteins
at rest, troponin molecules hold tropomyosin fibers so that they cover the myosin-binding sites on actin troponin has Ca2+ binding sites
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1
ATP
2
3
4
5
7 6
ATP
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The Trigger: motor neurons Motor neuron triggers muscle contraction
release acetylcholine (Ach) neurotransmitter
1
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Nerve signal travels down T-tubule
stimulates sarcoplasmic reticulum (SR) of muscle cell to release stored Ca2+
flooding muscle fibers with Ca2+
Nerve trigger of muscle action2
3
4
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At rest, tropomyosin blocks myosin-binding sites on actin secured by troponin
Ca2+ binds to troponin shape change
causes movement of troponin
releasing tropomyosin exposes myosin-
binding sites on actin
Ca2+ triggers muscle action
5
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How Ca2+ controls muscle Sliding filament
model exposed actin binds
to myosin fibers slide past each
other ratchet system
shorten muscle cell muscle contraction
muscle doesn’t relax until Ca2+ is pumped back into SR requires ATP
ATP
ATP
6
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Interaction of thick & thin filaments Cross bridges
connections formed between myosin heads (thick filaments) & actin (thin filaments)
cause the muscle to shorten (contract)
sarcomere
sarcomere
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Where is ATP needed?
3
4
12
1
1
1
Cleaving ATP ADP allows myosin head to release from actin filament
thin filament(actin)
thick filament(myosin)
ATP
myosin head
formcrossbridge
binding site
ADP
releasecrossbridge
shortensarcomere
1
7
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Learning Check Summarize the role neurotransmitters,
Ca2+ , and ATP play in muscle movement.
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How it all works… Action potential reaches the end of a motor neuron
and acetylcholine is released A new action potetial is generated in the muscle cell Action potential causes Ca2+ release from SR
Ca2+ binds to troponin Troponin moves tropomyosin uncovering myosin
binding site on actin Myosin binds actin and pulls actin chain along
Uses ATP to release, "unratchets" & binds to next actin Sarcomere shortens (Z discs move closer together) Whole fiber shortens contraction!
Ca2+ pumps restore Ca2+ to SR relaxation! pumps use ATP
ATP
ATP
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Put it all together…1
ATP
2
3
4
5
76
ATP
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Fast twitch & slow twitch muscles Slow twitch muscle fibers
contract slowly, but keep going for a long time more mitochondria for aerobic respiration less SR Ca2+ remains in cytosol longer
long distance runner “dark” meat = more blood vessels
Fast twitch muscle fibers contract quickly, but get tired rapidly
store more glycogen for anaerobic respiration sprinter “white” meat
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Muscle limits Muscle fatigue
lack of sugar lack of ATP to restore Ca2+ gradient
low O2 lactic acid drops pH which
interferes with protein function synaptic fatigue
loss of acetylcholine Muscle cramps
build up of lactic acid ATP depletion ion imbalance
massage or stretching increases circulation
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Learning Check What determines the strength of a
muscle? How does a person build muscle
strength?
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Diseases of Muscle tissue ALS
amyotrophic lateral sclerosis Lou Gehrig’s disease motor neurons degenerate
Myasthenia gravis auto-immune antibodies to
acetylcholine receptors
Stephen Hawking
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Botox Bacteria Clostridium botulinum toxin
blocks release of acetylcholine botulism can be fatal muscle
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Rigor mortis So why are dead people “stiffs”?
no life, no breathing no breathing, no O2
no O2, no aerobic respiration no aerobic respiration, no ATP no ATP, myosin remains connected to actin muscle fibers continually
contract tetany or rigor mortis
eventually tissues breakdown& relax measure of time of death
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