METHODS OF STUDY OF SKELETAL MUSCLE – ACTIONS Following methods are employed for study of skeletal muscle actions:
I.ELECTROMYOGRAPHY
It is throwing much new light about the functions of an individual muscle or groups of muscles.
It consists of putting electrodes into the muscle to be tested. After this, the individual is asked to perform a motion. The difference of electrical action potentials of the muscles are amplified and recorded mechanically.
There is a direct relationship between the electrical activity (ie., action potential and tension produced in the muscle during contraction. By this we can know that at what particular stage a muscle starts acting and at what stage the activity becomes maximum.
By using a large number of amplifiers, the simultaneous actions of a of muscles could be ascertained.
MUSCLE TRANSPLANTATION EXPERIMENTS:
This method is currently in experimental stage mainly in animals. INSPECTION AND PALPATION:
The person is asked to do the movements and the region under investigation could be inspected and palpated to note the activity of different muscles during various movements. The activity becomes visible due to swelling of the muscle and increase in the tension which could be seen and palpated. Utmost care should be exercised in differentiating a prime mover from the synergists.
DUCHENNE’S METHOD:
In this method a muscle is electrically stimulated and its actions are noted. This method forms the foundation for under-standing the muscular actions.
CADAVERIC METHOD:
In dead bodies the muscle could be freed from surrounding structures and thus pulled upon. By doing so the general course and action of the muscle may be observed.
NOMENCLATURE OF SKELETAL MUSCLES:
Before the 18th century few muscles had names. Galen and Vesalius used the numbers to designate the muscles in their illustrations. Various letters were used to designate the muscles by Leonardo da Vinci.
At present all muscles are named and these names convey useful information about the position, function, structure, etc. of muscles.
Unfortunately, there is no common method for naming the muscles. Various criteria used in naming the muscles (Nomenclature) are given below:-
Shape of the muscle :
A muscle may be named according to its shape.
Examples:
i)Trapezius
ii)Trapezoid in shape.
iii)Teres
iv)Rhomboid
v)Latissimus
vi)Round in shape
vii)Diamond or rhomboid in shape Widest and broad in appearance
viii)Rectus
Location:
A muscle may be named according to its location:-
Examples:
- Pectoralis
- Located in chest
- Brachii
- Located in arm
- Femoris
- Located in Thigh
- Temporalis
Muscles could be named according to their size :-
Examples:
- Gluteus maximus
- Gluteus medius
- Gluteus minimus
- The largest gluteal muscle
- A medium-sized gluteal muscle
- The smallest gluteal muscle
Number of Heads :-A muscle may be named according to the number of heads of
origin.
Examples:
i)Biceps
ii)Triceps
iii)Quadriceps
iv) Multicipital
- Two heads (Bicipital).
- Three heads (Tricipital)
- Four heads (Quadricipital).
Serratus anterior muscle arises by eight digitations or heads.
Origin and Insertions or Attachments :-
Muscles may be named according to their attachments. Examples:
i) Coracobra-chialis muscle
ii) Sternocleidomas-toid muscle
Direction of muscle cells:
- It is attached to coracoid process of scapula & humerus bone (the bone of brachium or arm)
- It is attached to sternum; clavicle and mastoid process of skull bone.
- Muscles are named according to the direction of constituent muscle cells in relation to axis of pull.
Examples:
i) Rectus
ii) Transversus
iii) Oblique
It is composed of muscle cells arranged longitudinally, parallel to the axis of the pull It is composed of transversally orientated muscle cells.It is composed of diagonal or obliquely oriented muscle.
Gross Morphology:
According to naked-eye appearance the muscles could be named
Examples:
i) Semimembran-osus
ii) Semitendino-sus
It is partly membranous in appearance
It is partly tendinous in appearance
Function or Action :
Depending upon the main actions, the muscle could be named.
Examples:
i) Supinator
It causes supination of the fore-arm
ii) Pronator
It causes pronation of the fore-arm
Combination of Various Criteria:
Following examples illustrate this criteria of naming the
muscle:
This muscle derives its name as follows:
| uscle Name | Derivation |
|---|
| Pronator Teres | a) According to action: It is the pronator of the forearm. |
| Flexor Digitorum Profundus | a) According to action: It is the flexor of the digits. b) According to location: It is deeply placed in the forearm (i.e., profundus). |
| Adductor Magnus | a) According to action: It is the adductor of the thigh. b) According to size: It is the largest in size compared with other adductors (i.e., magnus). |
| Adductor Longus | a) According to action: It is the adductor of the thigh. b) According to size: It is longer in comparison to other adductors (i.e., longus). |