1. BIOL 3151: Principles of Animal Physiology ANIMAL PHYSIOLOGY Dr. Tyler Evans Email: tyler.evans@csueastbay.edutyler.evans@csueastbay.edu Phone: 510-885-3475 Office Hours: M,W 10:30-12:00 or appointment Website: http://evanslabcsueb.weebly.com/

2. PROBLEM SET #1 IN-CLASS ASSIGNMENT WED OCT 16 will test on Lectures 1-9 will be in similar format to the midterm exam you will take on Fri Oct 18 th can use notes, textbook and discuss answers with classmates bring notes from all lectures have the entire class to complete the assignment

3. LAST LECTURE CELLULAR MOVEMENT AND MUSCLES MICROTUBULES cells use this microtubule network to control the movement of vesicles and other cargo to different parts of the cell e.g. color change in camouflaged animals Textbook Fig 5.3 pg 200 Xenopus frog darkens its skin by transporting pigment granules from the MICROTUBULE ORGANIZING CENTER to the periphery of the skin along microtubules

4. squid chromatophores use the same mechanism use the polarity (charge difference) between the each end of the microtubule to determine in which direction the pigment granules move (i.e. toward or away from skin) LAST LECTURE CELLULAR MOVEMENT AND MUSCLES MICROTUBULES

5. CELLULAR MOVEMENT AND MUSCLES motor proteins recognize this polarity and each motor protein moves in a characteristic direction: KINESIN: moves along the microtubule in the POSITIVE direction DYNEIN: moves along the microtubule in the NEGATIVE direction KINESIN DYNEIN TRANSPORT USING MICROTUBULES LAST LECTURE

6. CELLULAR MOVEMENT AND MUSCLES e.g. neurotransmitters transport down axons textbook Fig 4.16 pg 162 neurotransmitters are released at synapses to induce a response neurotransmitters are carried from the cell body (i.e. soma) down the axon on microtubules kinesin can transport neurotransmitters to the end of the synapse (+ direction) dynein then carries the empty synaptic vesicle back to the soma (- direction) textbook Fig 5.7 pg 204 TRANSPORT USING MICROTUBULES

7. CELLULAR MOVEMENT AND MUSCLES MICROFILAMENTS microfilaments are the other type of cytoskeletal element used in movement also involved in transport within cells, but in cell shape changes and moving from place to place microfilament based movement uses ACTIN and the motor protein MYOSIN microfilaments are composed of long string of ACTIN microfilaments form in much the same way microtubules: “+” and “-” ends of actin assemble actin monomers are termed G- ACTIN “G” stands for globular referred to as F-ACTIN when in polymers “F” stands for filamentous LAST LECTURE

8. CELLULAR MOVEMENT AND MUSCLES LAST LECTURE SLIDING FILAMENT MODEL the myosin molecule extends by straightening its NECK (i.e. arms extending) the myosin HEAD then forms a bond with the actin filament (i.e. hands grasping onto the rope) this strong interaction between actin and myosin is called a CROSS BRIDGE myosin bends and pulls the actin filament towards its tail (i.e. pull up) this step is called the POWER STROKE HEAD then uncouples from actin and myosin returns to the resting unattached position Actual movement depends on whether it is actin or myosin that is free to move if rope attached, you will pull yourself (myosin is mobile) If rope not attached, you will pull the rope (actin is mobile) Textbook Fig 5.12 pg 209

9. large forces generated during muscle contraction are the result of combining the actions of many polymers of myosin MUSCLE STRUCTURE AND REGULATION OF CONTRACTION TODAY’S LECTURE polymers of myosin are called THICK FILAMENTS thick filaments are doubled headed, meaning they have clusters of the myosin head at each end in muscle tissue, thick filaments of myosin slide along polymers of actin called THIN FILAMENTS textbook Fig 5.15 pg 212

10. MUSCLE STRUCTURE in vertebrate STRIATED MUSCLE, thick and thin filaments are arranged in a characteristic pattern cardiac (heart) and skeletal muscles are examples of striated muscle textbook Fig 5.16 pg 213 STRIATED MUSCLE

11. basic unit of striated muscle is called the SARCOMERE muscles are comprised of many sarcomeres arranged in a repeated pattern, that gives striated muscle striped appearance textbook Fig 5.17 pg 215 SARCOMERE MUSCLE STRUCTURE

12. areas occupied by thick filaments appear darker than those lacking thick filaments area occupied by thick filaments called the A-BAND lighter regions are areas lacking thick filaments and are comprised of thin filaments and other cytoskeletal proteins this region is referred to as the I-BAND middle region where forming gap between extending thin filaments forms the M-LINE Z-DISKS are plates that hold actin think filaments in place myosin actin M-line Z-disk MUSCLE STRUCTURE

13. basic unit of striated muscle is called the SARCOMERE sacromere is formed by a thick filament surrounded by an array of six thin filaments at each end of the sacromere is a protein plate called the Z-DISK thin filaments extend out from the Z-disk the double headed thick filaments are arranged between the two Z- disks thick filaments span two sets of thin filaments, so that one end of the thick filament can associate with one set of thin filaments and the other end with another set of thin filaments textbook Fig 5.18 pg 215 MUSCLE STRUCTURE

14. textbook Fig 5.17 pg 215 MUSCLE STRUCTURE

15. CHANGES IN ACTIN AND MYOSIN DURING MUSCLE CONTRACTION many myosin molecules extend their necks and attach to actin to form a CROSS BRIDGE hydrolysis of ATP provides energy for POWER STROKE that pulls thin filaments, which are attached to Z-disk, toward the M-line as a result, the sarcomere shortens or the muscle contract

16. the arrangement of the sarcomere determines contraction force if the sarcomere is too short, thin filaments will collide and there will be little space for the muscle to contract the force generated will decrease Normal Sarcomere Too Short Sarcomere textbook Fig 5.17 pg 215 MUSCLE STRUCTURE & CONTRACTION FORCE CHANGES IN ACTIN AND MYOSIN DURING MUSCLE CONTRACTION

17. if sarcomere is too long, some myosin heads will not overlap with thin filaments and be unable to form cross-bridges fewer cross-bridges means less force generated during contraction Normal Sarcomere Too Long Sarcomere textbook Fig 5.17 pg 215 MUSCLE STRUCTURE & CONTRACTION FORCE CHANGES IN ACTIN AND MYOSIN DURING MUSCLE CONTRACTION

18. the arrangement of the sarcomere effects contraction force textbook Fig 5.19 pg 216 MUSCLE STRUCTURE

19. muscle cells incorporate hundreds of thousands of repeating sarcomeres a single continuous stretch of interconnected sarcomeres is called a MYOFIBRIL MUSCLE CELLS are made of groups of myofibrils encased in a plasma membrane called a SARCOLEMMA MUSCLE CELL STRUCTURE

20. REGULATION OF MUSCLE CONTRACTION textbook Fig 4.16 pg 162 textbook Fig 5.7 pg 204 first steps toward muscle contraction occur when action potentials from the brain travel down motor neuron to the neuromuscular junction this triggers release of neurotransmitter ACETYLCHOLINE, which binds to a receptor on the sarcolemma (muscle cell membrane) this binding induces an action potential to spread throughout the muscle cell

21. action potential generated when ACETYLCHOLINE binds to receptors spreads across the SARCOLEMMA (muscle cell membrane) the sarcolemma has a unique feature important for contraction it is covered with pores called T-TUBULES that provide a pathway for action potentials to spread across the muscle cell as the action potential spread across the muscle cell, it causes large amounts of calcium (Ca +2 ) to be released from storage units called the SARCOPLASMIC RETICULUM (in blue below) REGULATION OF MUSCLE CONTRACTION

22. the released Ca +2 is then used to regulate actin-myosin binding the Ca +2 signal is transmitted to actin and myosin by two proteins that associate with the actin thin filaments: TROPONIN and TROPOMYOSIN textbook Fig 5.21 pg 220 when intracellular Ca +2 is low the complex of troponin and tropomyosin block myosin binding sites on the thin filament increases in intracellular Ca +2 causes complex of troponin and tropomyosin to roll out of the way and allow myosin to bind to actin filament

23. TROPONIN is composed of three subunits (i.e. smaller proteins that group together to form one large protein) TnC- is a Ca +2 sensor and can bind Ca +2 with high affinity TnI- blocks the myosin binding site TnT- binds tropomyosin and keeps complex associated with actin textbook Fig 5.21 pg 220 REGULATION OF MUSCLE CONTRACTION C = calcium I = inhibitory T = tropomyosin

24. REGULATION OF MUSCLE CONTRACTION in a typical muscle cell, intracellular Ca +2 is very low and binding site on TnC are empty. empty TnC interacts with TnI to block myosin from binding to actin when muscle is activated, intracellular Ca +2 spikes (100-fold) and binds to TnC binding of Ca +2 to TnC induces a change in conformation in TnI that exposes the myosin binding site on actin because TnT is bound to tropomyosin the complex exposes the myosin binding site by sliding down tropomyosin tropomyosin Troponin complex (TnC, TnI, TnT) Myosin head actin = exposed myosin binding site INACTIVE ACTIVE textbook Fig 5.22 pg 220

25. SLIDING FILAMENT MODEL the myosin molecule extends by straightening its NECK (i.e. arms extending) the myosin HEAD then forms a bond with the actin filament (i.e. hands grasping onto the rope) this strong interaction between actin and myosin is called a CROSS BRIDGE myosin bends and pulls the actin filament towards its tail (i.e. pull up) this step is called the POWER STROKE HEAD then uncouples from actin and myosin returns to the resting unattached position Actual movement depends on whether it is actin or myosin that is free to move if rope attached, you will pull yourself (myosin is mobile) If rope not attached, you will pull the rope (actin is mobile) Textbook Fig 5.12 pg 209 REGULATION OF MUSCLE CONTRACTION

26. actin-myosin activity stops when action potentials from brain stop and intracellular Ca +2 falls back to resting levels causes Ca +2 binding sites on TnC to be vacant again myosin binding sites in actin are once again blocked by TnI textbook Fig 5.22 pg 220 Ca +2 and myosin binding

27. REGULATION OF MUSCLE CONTRACTION this relaxation phase is dependent on ACETYLCHOLINESTERASE, that breaks the down acetylcholine to acetic acid and choline this stops action potential from triggering the release of Ca +2 from sarcoplasmic reticulum

28. LECTURE SUMMARY large forces generated during muscle contraction are the result of combining the actions of many polymers of myosin (THICK FILAMENTS) and actin (THIN FILAMENTS) basic unit of striated muscle is called the SARCOMERE, which is highly patterned and gives this type of muscle its striped appearance (know the structure) binding of acetylcholine to its receptor causes action potential to spread across muscle cell membrane called the SARCOLEMMA aided by pores called T-TUBULES striated muscle contracts when action potential causes calcium (Ca +2 ) levels increase within the myofibril the Ca +2 signal is transmitted to the contractile apparatus by two proteins associated with thin filaments: TROPONIN and TROPOMYOSIN this relaxation phase is dependent on ACETYLCHOLINESTERASE that stops action potential from triggering the release of Ca +2 from sarcoplasmic reticulum

29. NEXT LECTURE MUSCLE DIVESITY IN VERTEBRATES AND INVERTEBRATES textbook Fig 5.34 pg 239