Download B. Sliding Filament Theory of Muscle Contraction

Outline of Lecture on Muscle Physiology 2010
(with focus on Physiology of Skeletal Muscle Contraction)
Lecturer: D.G. Simbulan, Jr., Ph.D.
-----------------------------------------------------------------------------------------------------------Introduction: Types and Function of Muscle Tissue
I.
Muscle Architecture: Review of Skeletal Muscle Fiber Structure and
Filaments; Molecular Composition
a. From Muscle to Fascicles to Muscle Fibers (Myofiber) to Myofibrils to
Sarcomeres/Myofilaments
b. What constitutes a Muscle Fiber ? Sarcolemma, Sarcoplasmic reticulum and
Myofibrils
c. Myofibrils and Sarcomeres; Myofilaments - Thick and Thin Filaments; What
proteins constitute the thick and thin filaments; relation to each other ? Know the
A-band, I-band, H-zone, M-line/region, Z-line/ disk.
d. How are actin filaments anchored to the Z-line ? Role of Nebulin in stabilizing
the actin filaments
e. How are Myosin filaments stabilized to the Z-line/disk ? to the M line/ M-region
? Role of Titin
f. Molecular structure of Actin; Myosin; acessory or regulatory proteins of actin:
troponin, tropomyosin
g. The T-system (transverse tubules), SR, terminal cisternae of SR, and relation to
Sarcomeres; the DHP receptor in the T-tubules; the Ryanodine receptor in the
terminal cisternae; which receptor is the voltage-sensor in ExcitationContraction coupling ? which receptor is the Ca++ release channel ? what is
the triad ?
h. Role of calsequestrin (mainly skeletal muscle, also cardiac and smooth) and
calreticulin (mainly high concentration , smooth musde) in the sarcoplasmic
reticulum; Ca++ pump in the SR/ terminal cisternae
i. What makes calsequestrin unload its Ca++ ?
II.
How Does Skeletal Muscle Perform its Contractile Functions
Having known muscle cytoarchitecture and molecular structure, you should be able
to discuss the following:
A. Excitation-Contraction Coupling
a. Describe how wave of depolarization from the sarcolemma initiates muscle
contraction.
b. Describe relationship of DHP receptor and the Ryanodine receptor.
c. Role of intracellular stores of Ca++ in SR/terminal cisternae
B. Sliding Filament Theory of Muscle Contraction
a. Role of thick and thin filaments
b. Role of Ca++
c. Take note of the various stages/ states of the cross-bridge cycle (Berne and
Levy, 5th edition, Fig. 12-11, p. 232 ). Optional see also Fig. 9-7 (Boron, p.
239). [Compare this with Figure 58-6, p. 720, Harper’s Biochemistry, note
that you have to change the numbering of the steps to coincide with that of
Boron (Fig. 9-7, p. 239). To do that, read the descriptions in Boron and
Harper’s and the chemical reactions taking place. This is so you don’t get
confused in reviewing for your Physiology and Biochemistry component of
the Evals.
C. Termination of Contraction;
a. role of ATP
b. role of Ca++ pump
c. role of neuro-muscular junctional transmission
What happens during muscle fatigue/ cramps ? during rigor mortis ? why ?
III.
Overview: Comparative Physiology of Skeletal, Cardiac, and Smooth Muscles
1. Role of calcium in initiating muscle contraction in the three muscle
types
2. Where does calcium come from in the initiation of skeletal muscle
contraction ? Where does calcium come from, in the initiation of
cardiac and smooth muscle contraction ?
3. Principal calcium sensors in striated muscle which initiates muscle
contraction ?
4. Principal calcium sensor in smooth muscle which initiates muscle
contraction
5. For summary tables: see also
a. Table of Some Differences Among Different Muscle Types (Harper’s
Biochemistry, 25th edition, p. 725)
b. Summary of Comparisons Between Muscle Types (Boron, Medical
Physiology, p. 253).
Others:
Be able to tie up this lecture module with the Lecture topics on Electrophysiology I (Resting
Membrane Poténtials and Action Potentials) and Electrophysiology II (Synaptic and Junctional
Transmission). See also Table 3-2 Sequence of Events in Contraction and Relaxation of
Skeletal Muscle, p. 70 in Ganong (21st/ 22nd edition, or earlier editions) , Review of Medical
Physiology.
References:
Principally: *Guyton and Hall, Chapter 6 Contraction of Skeletal Muscle, pp. 72 – 83
Secondarily, for comparison with smooth and cardiac muscle, see:
*Guyton and Hall, Chapter 8 Contraction and Excitation of Smooth Muscle, pp. 92 – 99
*Guyton and Hall, Chapter 9 Contraction and Excitation of Smooth Muscle, pp. 103 - 104
See also pre-lecture Handout for other references.
Main: Berne and Levy, PHYSIOLOGY, 5th edition, Chapter 12
Boron and Boulpaep, Chapter 9, “Cellular Physiology of Skeletal, Cardiac and Smooth
Muscle,”MEDICAL PHYSIOLOGY pp. 230 – 254.
Ganong, Chapter 3, Ëxcitable Tissue: Muscle, pp,. 65 – 85, with focus on Skeletal Muscle, pp. 65
– 78