25 October 2010 This Week in Physiology: Lab: Frog Muscle Twitches Lectures: Ch. 9 Muscle Physiology & Ch. 10 Body Movement Friday: Abstracts Due Next Week in Physiology: Monday: Test # 2 Lectures: Ch. 12 Cardiovascular Physiology

1QQ # 21 for 8:30 Compare and contrast EPPs and EPSPs. Which are characteristics of smooth muscle? Cylindrical shape Multinucleated Attached to tendons Connected to each other by intercalated disks Can be excited or inhibited

1QQ # 21 for 9:30 What is the cause of myasthenia gravis and what are the symptoms? Which are characteristics of cardiac muscle? Cylindrical shape Multinucleated Attached to tendons Connected to each other by intercalated disks Can be excited or inhibited

How does AP in sarcolemma cause twitch? Fig. 09.01a S 5 Capillaries Oxygen, Nutrients, hormones, waste How does AP in sarcolemma cause twitch? 09.01a.jpg

Types of Contractions S1 Isotonic = Same tension Isometric = Same length Look at contractile properties of individual skeletal myofiber and then at whole muscles (hundreds or thousands of myofibers.)

Terms: Myofiber, myofibril, myofilament Fig. 09.11b Terms: Myofiber, myofibril, myofilament 09.11b.jpg Thick myofilament = myosin Thin myofilament = actin

Fig. 09.11a S 3 09.11a.jpg

Fig. 09.12 S 4 High fAP leads to accumulation of Ca++ in sarcoplasm because Ca++ ATPase doesn’t return all Ca++ to SR quickly enough. The concentration of free calcium is directly related to force of contraction in skeletal muscle Thus we need to understand the cellular mechanism of contraction… cell biology flashbacks… 09.12.jpg

S5 YouTube Videos Role of ATP in muscle Creepy Muscle demo Sarcomere contraction Powerstoke in muscle I Powerstroke in muscle II 09.09.jpg

Energy for powerstroke & Necessary for detaching myosin from actin Fig. 09.08 S 6 2 roles of ATP: Energy for powerstroke & Necessary for detaching myosin from actin Crossbridge cycling continues as long as ATP and Ca++ present. 09.08.jpg

dArk band = aligned myosin filaments Fig. 09.02 S 7 dArk band = aligned myosin filaments lIght band = absence of myosin filaments 09.02.jpg

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Fig. 09.03 S 9 09.03.jpg

Fig. 09.04 S 10 09.04.jpg

Fig. 09.05a S 11 09.05a.jpg

Fig. 09.05b S 12 Contracted 09.05b.jpg

Fig. 09.05a S 13 09.05a.jpg Image if the sarcomeres were stretched? How would the number of cross bridges be affected? And the tension produced?

Length-tension Relationship 09.21.jpg So….. Tension produced by a single myofiber varies depending on sarcomere length.

Muscle kinetics Link to cytosolic calcium concentration, release, and reuptake? S 15 09.10.jpg

Fig. 09.16 S 16 09.16.jpg

Fig. 09.19a S 17 Twitch Twitch Twitch 09.19a.jpg

Fig. 09.19b S 18 Summation 09.19b.jpg Tension is a result of the temporal control of cytosolic calcium concentration

Fig. 09.19c S 19 09.19c.jpg

S 20 Fig. 09.20 Why does this plateau? 09.20.jpg So….. Tension produced by a single myofiber varies depending on frequency of Action Potentials.

S 21 So what are the ways a muscle (consisting of many myofibers) increases tension (force)?

Fig. 09.13 S 22 Motor unit = a single somatic motor neuron and all the muscle fibers in innervates 09.13.jpg

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Increasing tension in a whole muscle Frequency of stimulation of motor neuron Activate larger motor units Recruitment: activate more motor units These factors influence actual tension Fiber length (length-tension) relationship Fiber diameter Level of fatigue (state of activity)

Increasing tension in a whole muscle Frequency of stimulation of motor neuron Activate larger motor units Recruitment: activate more motor units These factors influence actual tension Fiber length (length-tension) relationship Fiber diameter Level of fatigue (state of activity)

Muscle Metabolism Fiber types Muscles in action Speed of myosin ATPase Metabolic sources of ATP Timing of fatigue Muscles in action Causes of Fatigue Training and fiber type Creatine supplements

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