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)

AP Biology Animal Locomotion What are the advantages of locomotion? motilesessile

AP Biology Lots of ways to get around…

AP Biology Lots of ways to get around… molluskmammal birdreptile

AP Biology Lots of ways to get around… birdarthropod mammalbird

AP Biology Muscle voluntary, striated involuntary, striated auto-rhythmic involuntary, non-striated evolved first multi-nucleated digestive system arteries, veins heart moves bone

AP Biology  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

AP Biology Connective Tissue Wrappings of Skeletal Muscle Figure 6.1

AP Biology tendon skeletal muscle muscle fiber (cell) myofilaments myofibrils plasma membrane nuclei Organization of Skeletal muscle

AP Biology Human endoskeleton 206 bones

AP Biology 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

AP Biology

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

AP Biology 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?

AP Biology 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

AP Biology Muscle filaments & Sarcomere  Interacting proteins  thin filaments  braided strands  actin  tropomyosin  troponin  thick filaments  myosin

AP Biology Thin filaments: actin  Complex of proteins  braid of actin molecules & tropomyosin fibers  tropomyosin fibers secured with troponin molecules

AP Biology Thick filaments: myosin  Single protein  myosin molecule  long protein with globular head bundle of myosin proteins: globular heads aligned

AP Biology Thick & thin filaments  Myosin tails aligned together & heads pointed away from center of sarcomere

AP Biology 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?

AP Biology Learning Check  Using textbook, identify the following on your model:  I-band  A-band  H zone

AP Biology 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 ZZ ZZ

AP Biology Learning Check  Why are muscles cells said to contract if the muscle fibers themselves do not actually shorten?  Muscle contraction Muscle contraction

AP Biology Closer look at muscle cell multi-nucleated Mitochondrion Sarcoplasmic reticulum Transverse tubules (T-tubules)

AP Biology Muscle cell organelles  Sarcoplasm  muscle cell cytoplasm  contains many mitochondria  Sarcoplasmic reticulum (SR)  organelle similar to ER  network of tubes  stores Ca 2+  Ca 2+ released from SR through channels  Ca 2+ restored to SR by Ca 2+ pumps  pump Ca 2+ from cytosol  pumps use ATP Ca 2+ ATPase of SR ATP There’s the rest of the ATPs! But what does the Ca 2+ do?

AP Biology Muscle at rest  Interacting proteins  at rest, troponin molecules hold tropomyosin fibers so that they cover the myosin-binding sites on actin  troponin has Ca 2+ binding sites

AP Biology 1 ATP

AP Biology The Trigger: motor neurons  Motor neuron triggers muscle contraction  release acetylcholine (Ach) neurotransmitter 1

AP Biology  Nerve signal travels down T-tubule  stimulates sarcoplasmic reticulum (SR) of muscle cell to release stored Ca 2+  flooding muscle fibers with Ca 2+ Nerve trigger of muscle action 2 3 4

AP Biology  At rest, tropomyosin blocks myosin-binding sites on actin  secured by troponin  Ca 2+ binds to troponin  shape change causes movement of troponin  releasing tropomyosin  exposes myosin- binding sites on actin Ca 2+ triggers muscle action 5

AP Biology How Ca 2+ 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 Ca 2+ is pumped back into SR  requires ATP ATP 6

AP Biology Interaction of thick & thin filaments  Cross bridges  connections formed between myosin heads (thick filaments) & actin (thin filaments)  cause the muscle to shorten (contract) sarcomere

AP Biology Where is ATP needed? Cleaving ATP  ADP allows myosin head to release from actin filament thin filament (actin) thick filament (myosin) ATP myosin head form cross bridge binding site ADP release cross bridge shorten sarcomere 1 7

AP Biology Learning Check  Summarize the role neurotransmitters, Ca 2+, and ATP play in muscle movement.

AP Biology 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

AP Biology Put it all together… 1 ATP

AP Biology 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

AP Biology 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

AP Biology Learning Check  What determines the strength of a muscle?  How does a person build muscle strength?

AP Biology 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

AP Biology Botox  Bacteria Clostridium botulinum toxin  blocks release of acetylcholine  botulism can be fatal muscle

AP Biology Rigor mortis  So why are dead people “stiffs”?  no life, no breathing  no breathing, no O 2  no O 2, 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

AP Biology