Smooth - Cardiac Muscle - Lecture 9

Chapter Links and Quizzes

 

Energy requirements

Skeletal Muscle fiber types

Effect of exercise training

Smooth muscle

Cardiac muscle

Audio - Lecture - - Review 

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Smooth Muscle - internal organs, stomach, blood vessels

1. Structure of fibers

a. smaller than skeletal; 0.2 mm long; no t-tubules required

b. individual fibers - no fusion of cells therefore only 1 nuclei

c. gap junctions - therefore each cell does not require innervation electrical activity can spread from cell to cell

d. they have actin and myosin but arrangement is different

no striations since elements overlap

e. autonomic innervation - involuntary

2. Function - regulation is via Ca⁺⁺

a. depends on external - extracellular and intracellular Ca⁺⁺ little sarcoplasmic reticulum; no t-tubules

b. Ca⁺⁺ binds to calmodulin; similar to troponin C, but located on myosin head

c. with Ca⁺⁺ attached a protein kinase will phosphorylate myosin head enabling it to interact with actin - sliding filament

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d. activate smooth muscle by stretching it - worm stretch - depolarization-contraction

e. some types have inherent pacemaker spontaneous electrical depolarization

pacemaker activity is due to increase permeability for Ca⁺⁺ or Na⁺ or

decreased permeability for K⁺ --- not completely known

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Cardiac Muscle - intermediate between smooth and skeletal

structure :

a. has striations - not as pronounced

b. smaller fibers, like smooth - has branches

c. single nucleus

d. gap junctions - called intercalated discs

Function:

a. similar mechanism to skeletal (troponin and tropomyosin)

b. requires extra and intracellular Ca⁺⁺

c. some cells have spontaneous; electrical activity - pacemaker

Audio - Lecture - - Exam Review

REVIEW QUESTIONS

1. Calcium is the internal activator substance in:
   1. skeletal muscle
   2. cardiac muscle
   3. smooth muscle
   4. a and b are correct
   5. a, b and c are correct
2. In a smooth muscle, energy produced by the hydrolysis of ATP is used:
   1. Allow cross bridges to pivot.
   2. move K⁺ out of the cell.
   3. Break cross bridges.
   4. all of the above.
   5. none of the above.
3. Muscle that has a banding pattern when observed under the microscope and is voluntary is
   1. skeletal
   2. cardiac
   3. smooth
   4. all of the above
   5. both A and C

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