24 October 2011 This Week in Physiology: Lab: Frog Muscle Physiology Lectures: Ch. 9 Muscle Physiology Ch. 10 Control of Body Movement Next Week in Physiology: Lab: Human muscle physiology Abstracts due Monday Instructions on Website! Download JMP from on-campus About midterm grades…..

1QQ # 20 for 8:30 section 1.Which are characteristics of Slow-Oxidative myofibers? a)Abundant capillaries nearby b)ATP is hydrolyzed relatively quickly c)Abundant glycogen d)Abundant myoglobin e)Belong to large motor units. 2. Name the three classes of skeletal myofibers and indicate which type is best suited to serve as a postural muscle and why. Answer one question.

1QQ # 20 for 9:30 section 1.Which are characteristics of glycolytic myofibers? a)Abundant capillaries nearby b)ATP is hydrolyzed relatively quickly c)Abundant glycogen d)Abundant myoglobin e)Belong to large motor units. 2. Would a marathon runner benefit from supplementing with creatine? Why or why not? Answer one question.

So what are the ways a muscle (consisting of many myofibers) increases tension? S 1

Fig Motor unit = a single somatic motor neuron and all the muscle fibers in innervates S 2

S 3 But each motor unit has myofibers of the same type: I or IIA or IIB.

Increasing tension in a whole muscle Frequency of stimulation of motor neuron Activate larger motor units Recruitment: activate more motor units These factors also influence actual tension – Fiber length (length-tension) relationship – Fiber diameter (number of cross bridges) – Level of fatigue (state of activity) S 4

Fig Relationship between recruitment and motor unit type S 5 Size of somatic motoneuron cell body The Size Principle

Types of Contractions Isometric = Same length Isotonic = Same tension S 6 Aka Lengthening contraction

Response to training Resistance training Type II change enzyme profiles: II A to II B Type II add more actin and myosin Type II increase cross-sectional area (hypertrophy) Endurance training – Type I increases vascularity – Type I increase number of mitochondria S 7

Fig b Read section of King et al., 1999 that deals with analysis of muscle biopsy material in subjects taking Andro or placebo while resistance training. What changes were expected? What changes were observed? S 8

Consider blood flow to skeletal muscles during isometric contractions. Consider blood pressure during isometric contractions. S 9

The benefits of using trekking poles?

Chapter 9 B Properties of Smooth Muscle How does smooth muscle differ from skeletal muscle? (innervation, membrane potentials, excitation-contraction coupling, twitch duration, fatigue, etc. (Table 9-6 p.287) What are the features of membrane potential of smooth muscle? (pacemakers and slow waves) What are the differences between single-unit and multi-unit smooth muscle? (location, spread of excitation) S 10 Who cares about smooth muscles?

Figure 9.34 Special situation: Dephosphorylation & latch bridge from SR and influx during Action Potential or graded potential Graded potentials result in graded contractions S 11 Slow twitch of SM due to slow action of myosin ATPase. Lack troponin Excitation-contraction coupling in Smooth Muscles Ca ++

Latchbridge =latch state S 12 Comparison of Twitch Duration Thankful for latch state! Crucial for long-term tension of sphincters.

Control of membrane potential by neurotransmitters, hormones, local factors for some smooth muscles (0 2, NO, pH, stretch, vasodilators ….) S 13 Slow waves and pacemaker potentials Often with pacemaker cells Intestinal tract, uterus, small diameter blood vesselsLarge airways of lungs, large arteries, ciliary muscle Comparison of Single-Unit and Multi-Unit Smooth Muscles

Intercalated Discs: mechanical attachments of cardiac myofibers to each other, with gap junctions (electrical synapses) to conduct AP Analogy: Falling dominoes S 14 Cardiac Myofibers

Plateau phase S 15

S 16 Why no tetanic contractions of cardiac muscle?

Figure Calcium-induced calcium release Ca++ channels blockers: How and where do they work? When are they used? Excitation- Contraction Coupling What ends the twitch? S 17

Fig Know this table p. 287 S 18