Seminars in biomechanics-1 for physio students.pdf

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2. Subject title and
Code
Credit
Hours
Theoretical
Marks
Course work Total
Seminar in
Biomechanics
( E5 )
2 40 60 100
Welcome To
Seminar In Biomechanics

4. After completing this chapter, you will be able to:
Identify the basic behavioral properties of the musculotendinous unit.
Explain the relationships of fiber types and fiber architecture to muscle
function.
Explain how skeletal muscles function to produce coordinated
movement of the human body.
Discuss the effects of the force–velocity and length–tension
relationships and electromechanical delay on muscle function.
Discuss the concepts of strength, power, and endurance.

5. First part:
Introduction
Elements of muscle structure:
contracile proteins and structural proteins
The contracile unit :
Organization of contracile unit
Cross bridge interaction
Types of muscle contraction

7. Muscle:
Skeletal muscles contraction produces the force that are responsible for
movement of the body and all its joints.

Muscles also provide both dynamic stability of joints and protection,
contribute to posture and support, and produce a major portion of total
body heat.

There are over 600 skeletal muscles, which constitute approximately
40% to 50% of body weight.

8. Muscle:
Of these, there are 215 pairs of skeletal muscles. These pairs of muscles
usually work in cooperation with each other to perform opposite actions
at the joints they cross.

In most cases, muscles work in groups rather than independently to
achieve a given joint motion. This is known as aggregate muscle action.

Contains 50-75% of all body proteins .

Account for 30-50 %of whole body protein turnover

9. Composed of :
75% water .
20% protein
Inorganic salts ,minerals ,fat ,carbohydrates 5%





(Wolfe RR (2006) The underappreciated role of muscle in health
and disease. Am J Clin Nutr 84:475–482)

10. Function:
Mechanical point of view :
Convert chemical energy to mechanical energy to generate force ,power
,maintain posture and produce movement.
Metabolic point of view :
Maintain basal energy metabolism
Act as storage for important substrates such as amino acids and
carbohydrates.

(Wolfe RR (2006) The underappreciated role of muscle in health
and disease. Am J Clin Nutr 84:475–482)

11. Continue of metabolic function:
Of particular interest is the role of skeletal muscle as are reservoir of
amino acids needed by other tissues such as skin , brain, and heart for the
synthesis of organ-specific proteins .
 amino acid released from muscles maintain blood glucose level in case of
starvation .
For maintenance of health , you have to keep your muscle mass to make
body respond well to chronic illness and stresses.

(Wolfe RR (2006) The underappreciated role of muscle in health and disease. Am J Clin Nutr 84:475–482)

12. General Anatomy of Muscles
•They attach to bones through tendon, as they work on bones (levers) to produce movement
• The muscle must cross (act on) a joint to produce movement at that joint
• The direction of the movement produced is determined by the line of pull (LOP)
•Some muscles are divided into parts (anterior, posterior and middle) with each part having
different functions because of the different lines of pull
•Origin
–Proximal attachment is usually the origin;
– stationary attachment
•Insertion
- the distal attachment is usually the insertion
- mobile attachment
•Belly or Bulk
–thicker, middle region

13. How muscles are named:
Shape—deltoid, rhomboid
Size—gluteus maximus, teres minor
Number of divisions—triceps brachii
Direction of fibers—external abdominal oblique
Location—rectus femoris, palmaris longus
Points of attachment—coracobrachialis, extensor hallucis longus, flexor
digitorum longus

14. How muscles are named:
Action—erector spinae, supinator, extensor digiti minimi
Action and shape—pronator quadratus
Action and size—adductor magnus
Shape and location—serratus anterior
Location and attachment—brachioradialis
Location and number of divisions—biceps femoris

15. The behavioral properties of muscle:
Excitability Or Irritability: ability to respond to stimulation either:
-electrochemical, such as action potential
- mechanical, such as tendon reflex .
- internal stimulus
- external stimulus
Contractility- ability to shorten actively and exert a pull and to develop tension
Extensibility- ability to continue to extend (range of lengths)
Elasticity- ability to rebound to original length (like a rubber band)

16. The behavioral properties of muscle:

17. The elastic behavior of muscle
 Muscle is consisting of two major components:

The parallel elastic component (PEC), provided by the muscle
membranes, supplies resistance when a muscle is passively stretched.

The series elastic component (SEC), residing in the tendons, acts as
a spring to store elastic energy when a tensed muscle is stretched.

18. The elastic behavior of muscle

19. Muscle structure

20. `
Structure of skeletal muscle (From:
Raven et al. [82, Fig. 3.6]; original in
Sherwood [83, Fig. 8.2])

21. Muscle layers:
Epimysium
muscle
perimysium
bundles of muscle fibres

endomysium muscle fibre
sacrolemma
myofibres sacromeres myofilaments actin and myosin .

22. Muscle contractile VS non-contractile proteins

Actin:
Actin filaments are composed of: actin , tropomyosin and troponin.

-Double stranded f-actin protein molecules in helix form.
- Tropomyosin wrapped spirally around the sides of f –actin helix and
cover active sites of ADP in the actin filament.

23. Continue Actin:
Troponin : attached along sides of tropomyosin molecules .
It has 3 subunits : troponin I >>>attache to actin .
troponin T>>>attached to tropomyosin .
troponin C >>>attached to it calcium ions .





(guton and hall text book medical physiology chapter 6 contraction of skeletal muscle :pages 74-75)

24. Myosin :
Myosin filaments composed of multiple myosin molecules .
Myosin molecule composed of 6 polypeptide chains (2 heavy and
4 light chains ).
2 heavy chains wrapped around each other which called tail of myosin
molecule then at the end of the heavy chain , a globular of polypeptide
chain called myosin head which angulated about 120 degrees from heavy
chain to extend along whole length of myosin filament.
4 light chains are a part of myosin head .


(guton and hall text book medical physiology chapter 6 contraction of skeletal muscle :pages 74-75)

25. Myosin:

26. Continue of myosin:
Function of :
ATP BINDING SITE : ATPase enzyme to give energy for the myosin
head transfer to actin filament.
Essential light chain and Regulatory light chain : stabilize the head during
head transfer to actin and conformational changes for motor domain
generating force (transfer the compacted form to elongated one).

- Removal of light chains from myosin reduces the velocity of actin
filaments from 8.8 µm s
–
to 0.8 µm s.(for both essential and regulatory).

27. Titin :

It is a structural protein ,moves from z-line to myosin filament .
The largest protein in the body.
It is responsible for passive tension of muscle to stretch by
make it stiff as it bind to ca++ .
Responsible for maintaining position of myosin.

28. Titin:

30. Nebulin :
It is a huge protein which is highly expressed in skeletal muscle, was
thought to function as a molecular ruler specifying thin filament length.
 Nebulin stabilizes actin filaments, thereby regulating filament
length as by increase in length of actin …increase cross bridging
….increase overlap of actin filament increase its contraction.
nebulin contributes to sustaining the lateral alignment of myofibrils, an
essential component of coordinated contractile activity.


(Chu, Miensheng, Carol C. Gregorio, and Christopher T. Pappas. "Nebulin, a multi-functional giant." Journal of Experimental
Biology 219.2 (2016): 146-152.)

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32. (sliding filament theory)

33. Release of calcium from sarcoplasmic reticulum:

34. As Ca++ released from sacroplasmic reticulum
and bind to troponin c (TnC):

35. ATP bind to myosin head at ATP binding site then bind to
actin active site and start contraction :

36. (without oxygen)
Muscle Fibers Type
(with oxygen)
­© Dr. James T. Bell, IFPA

43. Epimysium CT that cover the outermost layer of muscle
CT that cover grouped of muscles fibers perimysium
fascicles a bundle of muscles fibers
Endomysium is fine sheath of
connective tissue that surrounds
each muscle fiber
fiber
myofibrils
myofiliment
(actin and
myosin)

47. Recruitment Ability
Basic Muscle Physiology
­© Dr. James T. Bell, IFPA

52. How Muscles Contract
Basic Muscle Physiology
­© Dr. James T. Bell, IFPA

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