Smooth Muscle. Spindle shaped 1/10 th Skel. Musc. cell width 1/1000s Skel. Musc. cell length Some endomysium (No Peri- or Epi-) Organized into sheets

Transcription

1 Smooth Muscle Spindle shaped 1/10 th Skel. Musc. cell width 1/1000s Skel. Musc. cell length Some endomysium (No Peri- or Epi-) Organized into sheets Typically two outside [longi] inside [circ]

2 Innervation of Smooth Muscle No NMJ Instead Varicosities bulbous swellings of nerve fibers release neurotransmitter into diffuse junctions

3 Varicosities

4 Innervation of Smooth Muscle Reduced SR No T-tubules instead Caveolae (Latin Little Caves )

5 Caveolae Caveolae sequester Ca 2+ from ECF Striations on cell? No No sarcomeres

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10 Myofilaments in Smooth Muscle Three main differences in microanatomy 1. No troponin Instead: protein calmodulin 2. Myofilaments spirally arranged contract in corkscrew manner

11 Nucleus Dense bodies Contracted smooth muscle fiber 2013 Pearson Education, Inc.

12 Intermediate filament Dense bodies 3. Intermediate Filaments Dense bodies network Dense bodies anchor intermediate filaments to sarcolemma Cable-like structure harnesses contraction syncs all cells to each other

13 Contraction of Smooth Muscle Slow, low energy, synchronized contractions Some pacemakers Neural control excitatory/inhibitory effects depends on NT Hormonal control diff organs excited by diff hormones i.e. gastrin à stomach; insulinà blood vessels

14 Smooth M. can stretch/shorten more Three characteristics of smooth m. stretching: 1. Stretch response First, stretch à contraction Then, stress-relaxation response important for stomach 2. Length & Tension Δs Stretched Smooth M. Tension>> Stretched Skel. M. Tension

15 Skeletal Muscle Smooth Muscle Tension (percent of maximum) Sarcomeres greatly shortened Sarcomeres at resting length Sarcomeres excessively stretched 75% 100% 170% Percent of resting sarcomere length Why? diag. arrangement of myofilaments Result: large Δs in volume, w/o flabbiness when empty

16 Smooth M. can stretch/shorten more Three characteristics (Cont.): 3. Hyperplasia Over + formation SM can divide to increase greatly in numbers Puberty: estrogen à adult-sized uterus Pregnancy estrogen à fit-11lb-baby uterus!

17 Smooth Muscle Types SM varies across organs in: 1. fiber arrangement & organization 2. innervation 3. stimulus responsiveness Two Types

18 Smooth Muscle Types Unitary SM aka visceral muscle very common charactersitics: all the stuff we ve been talking about SM up until now

19 Smooth Muscle Types Multi Unit SM e.g.: bronchi large arteries pupil adjuster muscles few gap junctions direct nerve connections autonomic control

20 Cardiac Muscle Tissue Cardiac Muscle Tissue striated and found only in the heart cardiocytes: Small single nucleus no terminal cisternae aerobic (high in myoglobin, mitochondria)

21 Cardiac muscle cell (intact) Intercalated disc (sectioned) Nucleus Myofibrils

22 Cardiac Muscle Tissue Intercalated discs specialized contact points between cardiocytes Many gap junctions coordinate cardiocytes Therefore heart acts like a fused mass

23 Cardiac Muscle Tissue Functional Characteristics Automaticity pacemaker cells Long contractions 10X skeletal muscle contraction

24 mv Skeletal: Tension msec Cardiac: No summation No tetanus mv Tension More next quarter! msec

25 Muscle Deterioration

26 Developmental Aspects Age > 30 y.o. Normal loss of muscle mass & strength Sarcopenia (remember Osteopenia?) penia = poverty If muscle mass ê, body é connective tissue why? New genes differentiate myosatellites à fibroblasts strength ê + atherosclerosis à intermittent claudication (claudicare = limp )

27 Developmental Aspects Sarcopenia can be slowed or reversed with exercise

28 Abnormal Muscle Loss

29 Abnormal muscle loss Myopathies muscular diseases, muscle fibers do not function Many reasons acquired drugs Glucocorticoids alcohol Acute; chronic impact accidents genetic many types, let s focus on Dystrophies

30 Muscular Dystrophy Dystrophy = degeneration of tissue Mostly appear in childhood Fat and connective tissue deposits Eventually fibers atrophy and degenerate Gastrocnemius M.

31 Muscular Dystrophy Duchenne muscular dystrophy (DMD): Most common and severe type Inherited, sex-linked

32 Sex-linked wut???

33 What happens if one X is damaged on mom? Daughter OK! (carrier)

34 What happens if one X is damaged on mom? Son NOT OK!

35 Muscular Dystrophy Incidence: 1/3500 boys Damaged code for largest human gene: dystrophin cytoplasmic protein stabilizes sarcolemma anchors cytoskeleton Dystrophin So, structural role

36 Muscular Dystrophy Fragile sarcolemma tears/dammaged à ECF Ca 2+ entry à damaged contractile fibers à inflammatory cells à muscle mass drops

37 Duchenne s Muscular Dystrophy Weak hip extensors à Wabble extra lordosis Tip toe walking? Tibialis anterior m. wastes away before Gastrocnemius m. walking stops by 3 7 y.o. Death of respiratory failure in 20s

38 Muscular Dystrophy No cure Prednisone é muscle strength and function immunosuppressant cancer drug problems? Gene Therapy: infuse genomes of viruses with human dystrophin infect human with virus problems?

39 Muscular Dystrophy Produce more utrophin successful in mice NOW shift gears LEVERS