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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