Types of Movement :
- Amoeboid movement: This movement takes place in phagocytes where leucocytes and macrophages migrate through tissue. It is affected by pseudopodia formed by the streaming of protoplasm (as in amoeba)
- Ciliary movement: These movements occur in internal organs which are lined by ciliary epithelium.
- Muscular Movement: This movement involves the muscle fibers, which have the ability to contract and relax.
MUSCLES :
Properties of Muscle :
- Excitability
- Contractility
- Extensibility
- Elasticity
Types of Muscles :
- Skeletal muscles or striated muscles –
- Closely associated with skeleton.
- They are striped appearance under the microscope and called Striated muscles.
- They are under voluntary control of nervous system, hence called voluntary muscles.
- These involved in locomotion and change of body postures.
- Unbranched and multinucleated.
- Visceral muscles or smooth muscles
- These are located in inner wall of hollow visceral organ.
- Spindle shaped and uni-nucleated.
- They do not exhibit any striation and are smooth in appearance.
- They are called smooth muscles or non-striated muscles.
- Their activities are not under voluntary control of nervous system hence called as involuntary muscles.
- They assist in transport of food through digestive tract and gametes through the genital tract.
- Cardiac muscles –
- The muscles of heart, involuntary in nature.
- Cardiac muscle cells assemble in a branching pattern to form a cardiac muscle.
- These are uni-nucleated with characteristic intercalated disc.
Structure of skeletal muscle :
- Each organized skeletal muscle in our body is made of a number of muscle bundles called fascicles held together by common fibrous covering called fascia.
- Each fascicle consists of a number of muscle fibres (cell) covered by a common fibrous perimysium.
- Each muscle fibre is lined by the plasma membrane called sarcolemma, enclosing cytoplasm called sarcoplasm.
- The sarcoplasm contain endoplasmic reticulum, called sarcoplasmic reticulum is the store house of calcium ion.
- Muscle fibre is a syncitium as the sarcoplasm contain many nuclei.
- Muscle fibres contain a large number of parallelly arranged filaments in the sarcoplasm called myofilaments or myofibrils.
- There are two types of myofibrils are present in the sarcoplasm –
- Thin filament – Actin
- Thick filament – Myosin.
- The arrangement of thick and thin filament gives the characteristic striated appearance.
- The light bands contain only actin filaments and are called I-band or isotropic band.
- The dark band called ‘A’ or anisotropic band contains both actin and myosin.
- In the centre of each ‘I’ band is an elastic fibre called ‘Z’ line which bisects it.
- The thin filaments or actin are firmly attached with the ‘Z’ line.
- The thick filaments or myosin in the ‘A’ band are also held together in the middle by a thin fibrous membrane called ‘M’ line.
- The portion between two successive ‘Z’ lines is considered as the functional unit of the muscle called sarcomere.
- Each ‘A’ band contains two overlap zone of thick and thin filament called ‘O’ band.
- The central part of thick filament, not overlapped by thin filament is called ‘H’ band.
- ‘A’ band = 2(O) + H.
