Ch 12-13

20. List and describe the order in which motor units are recruited based on the need for increasing tension.

1) Type 1 m.u. (Red Slow) 2) Type 2A m.u. (Intermediate) 3) Type 2B m.u. (White Fast)

22. Explain how a muscle will develop if exercised regulary & "anaerobically" (strength-training, short burst type exercise).

An interesting fact is that the same exercises performed with different intensity can be called either aerobic or anaerobic. For example, jogging or riding a bicycle are usually considered to be aerobic exercises, while weight lifting is considered to be anaerobic. Increases strength, improves bone density, builds up muscles

24. Differentiate between Atrophy and Hypertrophy. Describe how each of these may occur and what takes place in the muscle/muscle cells during each process.

Atrophy: Decrease in muscle mass. - Due to disuse. Hypertrophy: Increase in muscle mass due to an increase in muscle cell size. - A bodybuilder or someone with overdeveloped muscles in their arms from using a wheelchair. - Repeated damage to the muscle cells; as long as the body can, it will try to compensate by increasing the size of the remaining cells.

Why are Muscle fascicles multi-nucleated?

Because the fibers are large, so more nuclei allows a closer nucleus to send signals where needed.

16. Explain why a muscle fiber can exhibit temporal summation but not spatial summation.

Because there has to be some sort of relaxation time between APs. If there is not, it results in tetanus.

2. Which two muscle types are striated?

Cardiac and SKM

Muscle Fascicles Characteristics

Composed of muscle fibers(cells) Contain: Sarcolemma(membrane), T-Tubules(continuation of sarcolemma and functionally linked to the SR), Sarcoplasm(the cytoplasm), and multiple nuclei

13. Explain why muscle fatigue occurs and the forms that it may take (use fig. 12-14 5th ed., 12.13 6th & 7th eds., for reference).

Fatigue: describes reversible condition in which an exercising muscle is no longer able to generate/ sustain the expected power output Influenced by: 1) intensity of contractile activity 2) duration of contractile activity 3) by whether the m fiber is using aerobic/anaerobic metabolism 4) by the composition of the muscle 5) by the fitness level of the indvl FORMS OF MUSCLE FATIGUE: Central fatigue: mechanisms that arise in CNS; includes subjective feelings of tiredness & desire to cease activity; thought to precede physiological fatigue & may be protective mechanism Peripheral fatigue: mechanisms that arise anywhere between neuromuscular jn & contractile elements of the muscle

Describe the characteristics of skeletal muscle as described in lecture and the introduction of chapter 12. Focus on the structural levels of a muscle as described in figure 12.3 (all editions).

From gross to Micro: Skeletal Muscle Connective Tissue and Never and Blood Vessels Muscle Fascicles: Bundle of fibers Connective Tissue Muscle Fiber Nucleus

31. Describe the characteristics of the golgi tendon organ (location, components & function).

GTO is found at the junction of tendons and muscle fibers, placed in series with the muscle fibers. They respond primarily to muscle tension created during the isometric phase of contraction and are relatively insensitive to muscle stretch. They are composed of free nerve endings that wind between collagen fibers inside a connective tissue capsule.

8. List the steps in the cross-bridge cycle and also describe in terms of the chemical events that utilize ATP. Be able to describe the roles of ATP and Calcium in skeletal muscle contraction (also refer to Figs. 12-9, 12-10 5th ed.; 12.8, 12.9 6th & 7th eds.).

Myosin head is charged with a fresh ATP and is ready to bind to the actin. It is inhibited by the Tm which blocks the binding. The myosin head binds to actin molecule after Tm moves aside. (Tm moves aside when Ca binds to Tn.) Power stroke takes place which moves actin filament toward M line. Myosin releases the ADP and must be recharged with a fresh ATP in order to release from the thin filament. If no ATP is available, a rigor state will develop. If ATP and Ca are available the head will detach and the cyle will continue. ATP provides the energy needed for the power stroke. Myosin converts the chemical bond energy of ATP into the mechanical energy of crossbridge motion. Energy released by ATP hydrolysis is trapped by myosin and stored as potential energy in the angle between the myosin head and the long axis of the myosin filament.

Function of Actin, Titin and Nebulin

Nebulin: Support rod of Thin Filament Actin: Pearls surrounding Nebulin Titin: Attaches thick filaments to Z line

Myofibrils Characteristics

Number of myofibrils determine strength/force produced by each muscle fiber Composed of proteins: Troponin, actin, tropomyosin, myosin, titin, nebulin

Describe the changes that occur within the sarcomere during contraction (sliding filament mechanism), with respect to the size of the A bands, the I bands and distance between z disks. (refer to fig. 12-8 5th ed., 12-6 6th ed.; 12.5 7th ed.)

Only I-Band and H-Zone contract. Filaments never change size. Moves Z disk closer to M Line

27. Explain the function and location of proprioceptors (p. 450 5th ed., p. 445 6th ed.; p. 420 7th ed. ).

Located in skeletal muscles, joint capsules, and ligaments. Their function is to monitor the position of our limbs in space, our movements, and the effort we exert in lifting objects.

21. Explain how a muscle will develop if exercised regularly & "aerobically" (endurance type exercise).

Mitochondrial potential can limit the supply of oxidative capacity. Endurance trained fibers have more/bigger mitochondria. Increase muscle mitochondria to AEROBICALLY generate ATP. Increase in total mitochondria= enzyme changes. increase in mitochondria exceeds typical increases in Vo2 max. Enzymatic changes allows one to keep a higher percentage of aerobic capacity w/o blood lactate accumulating

26. Distinguish between monosynaptic and polysynaptic reflexes (fig. 13.1).

Monosynaptic reflexes: consists of only two neurons and a single synapse. (A sensory afferent neuron and an efferent somatic motor neuron). These two neurons synapse in the spinal cord and only somatic motor reflexes can be monosynaptic. Polysynaptic reflexes: include one or more interneurons between the afferent and efferent neurons. All autonomic reflexes are polysynaptic because they have three neurons: one afferent and two efferent.

18. Define the terms motor unit and motor unit recruitment; then explain how depolarization of a neuron and muscle fiber are similar. (also refer to fig. 12-18 5th ed., 12.17 6th & 7th eds.)

Motor Unit: A collection of muscle fibers that share one motor neuron. Motor Unit Recruitment: As the stimulus increases in strength, additional motor neurons with higher thresholds begin to fire.

7. Describe the location and any unique physical features of the motor end plate in comparison to the rest of the sarcolemma.

Motor end plate is part of sarcolemma that has receptors for the ACh and the Na+ that will initiate the AP

29. Describe the characteristics of muscle spindles (location, components & function) (refer to figure 13.2 6th & 7th eds).

Muscle spindles are buried among the extrafusal fibers of the muscle. They send information about muscle stretch to the CNS. Each spindle consists of a connective tissue capsule that encloses a group of small muscle fibers known as intrafusal fibers.

14. Describe the relationship between cellular metabolism and the development of oxygen debt during exercise. Describe how oxygen debt is repaid. Read pp. 816-817 - 5th ed. Or in 6th ed.: pp.838-839; or 7th ed: pp. 789-790 (Chapter 25 - "oxygen consumption..." & "several factors....").

Oxygen Consumption: Oxygen is used up during oxidative phosphorylation when it combines with hydrogen in the mitochondria to form water. There is an increase in oxygen consumption even after the activity ceases. - When exercise begins, muscle oxygen consumption increases so rapidly that it is not immediately matched by the oxygen supplied to the muscles. - During this lag time, ATP is provided by muscle ATP reserves, phosphocreatine, and aerobic metabolism. Oxygen Debt: Respresents oxygen being used to metabolize lactate, restore ATP, and phosphocreatine levels, and replenish the oxygen bound to myoglobin.

11. Describe the relationship between the electrical events and development of tension in a muscle fiber during a twitch contraction (including latent period). (Also refer to Fig. 12-12 5th ed./ 12.11 6th & 7th eds.).

Phosphocreatin: Backup energy source of muscles. - This molecule's high energy phosphate bonds are created from creatine and ATP when muscles are at rest. - When the muscles become active, it is converted to ADP. Creatine Kinase: The enzyme that transfers the phosphate group from phosphocreatine to ADP. Aerobic Conditions: Pyruvate goes into Citric Acid Cycle. Anaerobic Conditions: Anaerobic glycolysis is a quicker source of ATP, but produces fewer ATP per glucose.

12. Explain how a steady supply of energy is provided to a contracting skeletal muscle through the use of stored ATP, phospho-creatine and finally under aerobic and anaerobic conditions.

Pools of ATP are stored and are sufficient for 8 twitches at a time. Otherwise, glycolysis and oxidatve phosphorylation to by synthesize ATP or from high energy phosphate bonds transfer energy The backup energy source of muscles is phosphocreatine, a molecule whose high-energy phosphate bonds are created from craetine and ATP when juscles are at rest. When muscles are activated, the energy is quickly transferred to ADP, creating more ATP. Creatine Kinase is the enzyme that transfers the phosphate group from phosphocreatine to ADP. Latent Period: Represents the time required for calcium release and binding to troponin.

32. Use figure 13-6(5th ed.) 13.5 (6th & 7th eds.) to describe reciprocal inhibition of antagonistic muscles during reflex, such as the knee-jerk reflex.

Reciprocal inhibition is for a reaction to happen one muscle must contract while another muscle relaxes. In the knee-jerk reflex, the sensory neuron synapses onto two pathways, one leading to the quadricep and making it contract (monosynaptic), the other leading to the hamstring (polysynaptic) and making it relax.

23. Identify regions of the body where we have muscles that are composed mostly of (a) white fast-twitch fibers, (b) red slow-twitch fibers.

Red muscle - Back, legs, butt White muscle - Arms, shoulders

3. Which type of muscle tissue is controlled only by somatic motor neurons?

SKM

Diagram a longitudinal section of the skeletal muscle fiber, including sarcolemma, sarcoplasm, myofibrils, location of sarcomeres, sarcoplasmic reticulum, terminal cisternae, T-tubules, and motor end plate.

SKM Muscle Fiber Anatomy: Nucleus SR Mitochondira Sarcolemma T-Tubules Thick/Thin Filament contained in myofibril

Sarcoplasm Characteristics

Sarcoplasmic Reticulum(SR)(Store Ca+2), Myofibrils, Mitochondria, Glycogen granules

19. Describe the characteristics of the 3 types of skeletal muscle fibers found in each skeletal muscle (Table 12.2) and their order of recruitment .

Slow-Twitch Oxydative, Red Muscle (Type 1): Slowest, Fatigue Resistance, Dark Red Fast-Twitch oxydative-glycolytic; Red Muscle (Type 2A): Intermediate, Fatigue Resistance, Red Fast-Twitch Glycolytic White Muscle (type 2x): Fastest, Easily Fatigued, Pale

1. The three types of muscle tissue found in the human body are , , and . Which type is attached to the bones, enabling it to control body movement?

Slow-twitch Oxidative (Red Muscle) Fast-twitch Oxidative Glycolytic Red (intermediate, pink) Fast-twitch Glycolytic (white muscle)

30. Use the standard steps of a reflex pathway to draw a reflex map of the stretch reflex activated by the muscle spindle. (fig. 13.3 6th & 7th eds.)

Stimulus (book being put onto hand) -> Sensory (muscle stretching) -> Input signal (increased afferent signals to spinal cord) -> Integrating center (spinal cord) -> Output signal (increased efferent output through alpha motor neurons) -> Target and response (muscle contracts)

6a. Describe the anatomy of the neuromuscular junction (synapse), and the roles that acetylcholine (Ach) and acetylcholinesterase play in the control of muscle fiber depolarization & contraction (ECC) Part 1

The neuromuscular junction consists of the axon terminals of a somatic motor neuron, the synaptic cleft and the motor end plate of the muscle fiber. ACh is released from somatic motor neuron and binds to receptor-channels on motor end plate of muscle fiber. When ACh -gated channels open, they allow Na and K to cross the membrane. This creates a net positive charge to the muscle fiber which depolarizes the membrane, creating an end plate potential (EPP). Usually EPPs initiate an AP in muscle fiber.

4. Describe the structure of myosin molecules and their organization in a thick filament; also describe the composition of a thin filament.

Thick Filaments: Composed of Myosin, contain M line down the middle of filament Anatomy: Mysoin Tail, Myosin hinge area, Myosin Head Thin Filaments: Composed of Troponin, Tropomyosin, Titin, Nebulin and Actin

What are Thin and Thick filamens composed of?

Thin: Troponin and Tropomyosin Thick: Myosin

10. Outline the process of rigor mortis.

Tight binding between actin and myosin in the absence of ATP. It only occurs for a very brief period in living muscles. After death when metabolism stops and ATP supplies are exhausted, muscles are unable to bind more ATP, so they remain in the tightly bound rigor state. AKA rigor mortis. The muscles "freeze" owing to immovable crossbridges.

5. List six proteins that make up the myofibrils. Which protein creates the power stroke for contraction?

Titin Nebulin Myosin Actin Troponin Tropomyosin

Draw a sarcomere and describe the arrangement of the molecular components: A band, I bands, z disk ( z-line), H zone, M line, thick (myosin) filament, thin (actin) filament, titin, nebulin (refer to Fig. 12.3).

A band - Length of thick filament (includes thick and thin, length does not change) I band - Length between thick filaments (includes only thin, length does change) Z disk - vertical line between sacromeres, connects to thin filaments H zone - Length between thin filaments (includes thick only, length does change) M line - vertical line down center of thick filament Thick (myosin filament) - motor protein with the ability to create movement. Composed of protein chains that intertwine to form a long tail and a pair of tadpole-like heads. Thin (actin) filament - globular protein (G-actin) molecules polymerize to form long filaments (F-actin). Two F-actin twist together like a double strand of beads, creating the thin filament. Titin - huge elastic molecule and the largest known protein. It stretches from one Z disk to the neighboring M line. It stabilizes position of filaments and returns stretched muscles to their resting length. Nebulin - an inelastic giant protein that lies alongside thin filaments and attaches to the Z disk. Helps align the actin filaments of the sarcomere.

6b. Describe the anatomy of the neuromuscular junction (synapse), and the roles that acetylcholine (Ach) and acetylcholinesterase play in the control of muscle fiber depolarization & contraction (ECC) Part 2

AP travels across surface of the fiber and into the t-tubules by the sequential opening of the voltage-gated Na channels. When the depolarization of the AP reaches a DHP receptor, the receptor changes conformation, which opens the RyR Ca release channels in the SR. Ca is released from the SR, which then binds to Tn...and contraction occurs.

4. T-tubules allow ______________ to move to the interior of the muscle fiber.

Action Potentials

25. FOR THOUGHT: Describe the means by which a motor unit is inhibited from contracting. Contrast this to the means by which neurons are inhibited from initiating an action potential. (further discussed in chap 13)

IPSP vs EPSP

17. Describe 3 types of skeletal muscle contraction: isometric, isotonic- concentric & isotonic-eccentric contractions. Use the terms "tension" and "load" in your definitions. (also refer to fig. 12-19 5th ed., 12.18, 12.19 6th & 7th eds.).

Isometric: Contractions that create force without moving a load. Isotonic Contractions: Any contraction that creates force and moves a load. -Concentric contraction: Cause muscles to shorten, thereby generating force. - Eccentric contractions: Cause muscles to elongate in response to a greater opposing force.

28. Describe the location and function of joint receptors.

Joint receptors are found in the capsules and ligaments around joints in the body. They are stimulated by mechanical distortion that accompanies changes in the relative positioning of bones linked by flexible joints. Sensory information from joint receptors is integrated primarily in the cerebellum.

9. Discuss the role of regulatory proteins (troponin - Tn & tropomyosin - Tm) in the cross bridge cycle.

Tm wraps around actin filaments and partially covers actin's myosin-binding sites. Tn controls the positioning of Tm. When calcium binds to Tn, the Tm shifts away from the actin's myosin-binding site and allows the actin to bind.

15. Describe and distinguish between twitch summation, unfused tetanus and tetanus (also refer to Fig. 12-17 5th ed., 12.16 6th & 7th eds.).

Twitch Summation: If a second stimulus is applied while the effects of the first stimulus are still present, then the second twitch adds to the remaining force of the first twitch. Tetanus: As the frequency of the stimuli increase, the individual twitches fuse to form a smooth sustained contraction. Unfused Tetanus: The relaxation time between successive twitches will get shorter as the strength of contraction increases in amplitude. - Wavelike