Chapter 10, reviewed and continued • Gross and microscopic anatomy of skeletal muscles • Nerve to muscle: excitation-contraction coupling • Factors affecting how much force is exerted • Muscle diversity • fast-twitch vs. slow-twitch • skeletal vs. cardiac vs. smooth Muscle metabolism, continued… A new sports drink advertises, “Includes ATP for rapid fueling of exercising muscles!” Are you tempted to buy it? Why or why not? • We make ATP as we use it; we DON’T stockpile huge supplies • Absorption! Can’t absorb highly charge molecules without a specific transporter (which we don’t have) Fast-Twitch vs. Slow-Twitch Muscle Fibers Fast-Twitch Slow-Twitch Overall function (speed? Speedy! Not speedy, but good strength? endurance?) endurance! Myosin type Type II Type I (I? II?) SR abundance Somewhat more SR Somewhat less (low? high?) Mitochondrial density Low (ATP from glycolysis, Higher (low? high?) etc.) Capillary density low Higher (low? high?) Substrates used Glucose (carbs) Carbs AND lipids (carbs? lipids?) COLOR? White meat Dark meat (myoglobin) Can exercise training convert fast fibers to slow fibers or vice versa? (Or are we prisoners of our genes?) Mitochondria and capillary density CAN change a lot with training. But myosin type (II vs. I) can NOT be changed by any normal training program. The heart: the ultimate slow-twitch muscle Similar to skeletal muscle, but more mitochondria… Metabolism is “entirely” aerobic (no glycolysis to speak of, except to feed into mito; maximize ATP production) Similar activation of contraction via SR, calcium, and troponin 10th Martini, Figure 10-22 Intercalated discs • Intertwined cell membranes of adjacent cells • Gap junctions = channels between cells; ions can pass; no NMJ, but pacemaker cells spread depolarization via gap junctions (still under neural control for speeding up and slowing down) • Desmosomes = CAMs (proteins) lock adjacent cells together High levels of troponin have been found in a patient’s blood. What could this mean? Troponin could come from damaged skeletal muscle OR damaged cardiac muscle. So … need to be aware of context! (sedentary & chest pain vs. ultramarathon runner at mile 84) Could also take an EKG (ECG) – look for abnormal conduction through heart Cardiac and skeletal muscle troponins have similar but non-identical amino acid sequences Christine E. Genge et al., Physiological Genomics 2013 10th Martini, Smooth Relaxed (sectional view) Figure 10-23b muscle Spindle shape, No striations, (but does Relaxed (superficial view) shorten when conracting) Contracted (superficial view) Skeletal vs. Cardiac vs. Smooth (Table 10-3) Property Skeletal Muscle Cardiac Muscle Smooth Muscle Fiber size Thick & long Skinnier, shorter Like cardiac Nuclei Many per cell! 1* 1 Organization of Sarcomeres give sarcomeres No sarcomeres contractile proteins striated appearance Control mechanism NMJ, ACh – Pacemaker cells, Like cardiac voluntary control gap junctions Calcium source SR SR + extracellular Like cardiac Calcium regulation Calcium => Similar to skeletal Different calcium- troponin based mechanism Contraction Fast, not great Slower, super Like cardiac speed/endurance endurance endurance! Energy source Carbs/glycolysis, VERY aerobic (little Like cardiac fat glycolysis) Clinical Case: myasthenia gravis • Usually an autoimmune disease (can you think of others?) • Acetylcholine (Ach) receptors are attacked • Treatment strategies? AChE = acetylcholinesterase (enzyme) Strategy: inhibit AChE to prolong binding of ACh to the receptors that ARE available (not blocked by immune system); can also use steroid to damp down immune response Figure 10-9 Worksheet: end-of-chapter review questions 19. Areas of the body where you would NOT expect to find slow fibers include the (a) back and calf muscles (b) eye and hand – YES – short bursts of activity (c) chest and abdomen (d) a, b, and c 20. During relaxation, muscles return to their original length because of all of the following except (a) actin and myosin actively pushing away from one another – YES – doesn’t happen (b) the contraction of opposing muscles (c) the pull of gravity (d) the elastic nature of the sarcolemma (e) elastic forces 21. According to the length-tension relationship, (a) longer muscles can generate more tension than shorter muscles (b) the greater the zone of overlap in the sarcomere, the greater the tension the muscle can develop (c) the greatest tension is achieved in sarcomeres where actin and myosin initially do not overlap (d) there is an optimum range of actin and myosin overlap that will produce the greatest amount of tension (e) both b and d are correct – YES … or (d) if you rule out (b) based on the idea of too much overlap at short sarcomere lengths 26. Explain why a murder victim’s time of death can be estimated according to the flexibility or rigidity of the body. (rigor mortis lasts from 2-7 hours post-death to 1-6 days) 27.Which of the following activities would employ isometric contractions? (a) flexing the elbow (b) chewing food (c) maintaining an upright posture - YES (d) running (e) writing 28. Many potent insecticides contain toxins, called organophosphates, that interfere with the action of the enzyme acetylcholinesterase. Ivan is using an insecticide containing organophosphates and is very careless. Because he does not use gloves or a dust mask, he absorbs some of the chemical through his skin and inhales a large amount as well. What signs would you expect to observe in Ivan as a result of organophosphate poisoning? Intense contractions => death (overstimulation of respiratory muscles leads to suffocation) 10th Martini, Chapter 11: An Introduction to the Muscular System • General concepts • Fascicle arrangements • Levers • Naming conventions • Lots and lots of muscles! Muscle PARALLEL CONVERGENT fascicles are arranged in different ways PENNATE CIRCULAR = form angle with tendon contracted relaxed 10th Martini, Figure 11-1 11-1 Fascicle Arrangement • Circular Muscles • Also called sphincters • Open and close to guard entrances of body • For example, orbicularis oris muscle of the mouth © 2015 Pearson Education, Inc. Parallel vs. Pennate: How does this affect muscle function? On page 334, your textbook says: “A pennate muscle contains more muscle fibers – and thus more myofibrils – than does a parallel muscle of the same size. For this reason, the pennate muscle produces more tension.” This is confusing and unhelpful! Parallel vs. Pennate Muscles: a better explanation? = 1 “unit” of muscle proteins (relaxed) bone bone bone bone contract bone bone High force, little change of position contract bone bone bone contract Large change of bone bone position, little Sortbone of intermediate – more force force than just 1 unit pulling on tendon (but less shortening - tradeoff) Muscles and Levers • Lever = “a rigid structure … that moves on a fixed point called a fulcrum” • Levers move when an applied force (AF) overcomes any load (L) that would prevent movement • Bones are levers • Joints are fulcrums • Muscles provide applied force 10th Martini, Figure 11-2 10th Martini, Optimized for speed, or for effective force? Figure 11-2 Optimized for exerting lots of force (speed of position change is small) Optimized for rapid position change (effective force is small) – most common 11-3 Muscle Attachments to Other Tissues • Origins and Insertions • Origin: fixed point of attachment • Insertion: moving point of attachment • Most muscles originate or insert on the skeleton • Origin is usually proximal to insertion “Knowing which end is the origin and which is the insertion is ultimately less important than knowing where the two ends attach and what the muscle accomplishes when it contracts.” © 2015 Pearson Education, Inc. 11-3 Muscle Attachments to Other Tissues • Remember the movement terms from the previous lab? (abduction/adduction, pronation/supination, etc.) • Now we can see how muscles achieve these movements! 11-3 Muscle Attachments to Other Tissues • Muscle Terminology Based on Function • Agonist (or prime mover) = the main cause of a particular movement (e.g., biceps brachii for elbow flexion) • Antagonist = opposes the agonist (e.g., triceps oppose/antagonize the biceps) • - stimulate both simultaneously for stability • Synergist = helps/works with agonist (e.g., brachialis for elbow flexion) Muscles you will need to know (Exercise 13) • Muscles of Facial Expression: • occipitofrontalis (frontalis) • orbicularis oris • levator labii • zygomaticus • lateral rectus • Muscles of Mastication: • temporalis • Muscles of Tongue, Throat, and Anterior Neck: • sternohyoid • sternocleidomastoid • Muscles of the Neck and Vertebral Column: • longissimus cervicis • semispinalis thoracis Muscles you will need to know (Exercise 13) • Muscles of the Thorax: Movement of the Scapula: • levator scapulae • rhomboideus major • serratus anterior • trapezius • Muscles of the Shoulder and Arm: • pectoralis major • flexor carpi radialis • deltoid • palmaris longus • supraspinatus • extensor digitorum • coracobrachialis • adductor pollicis • triceps brachii • biceps brachii • brachioradialis Muscles you will need to know (Exercise 13) • Muscles of the Hip and Leg: • iliacus • gluteus medius • sartorius • adductor longus • adductor magnus • quadriceps femoris: • rectus femoris, vastus lateralis, vastus medialis, vastus intermedius • hamstrings: • biceps femoris, semitendinosus, semimembranosus • tibialis anterior • flexor digitorum longus • gastrocnemius 11-4 Naming Skeletal Muscles • Names for skeletal muscles can indicate any of the