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Locomotion and Movement of Human
Body: Skeletal system explanation
Movement is one of the significant features of living beings
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Streaming of
protoplasm in the unicellular organisms like Amoeba is a simple form
of movement
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Human beings can move limbs, jaws, eyelids,
tongue, etc
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Such voluntary movements are called locomotion
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Locomotory structures need not be different from those
affecting other types of movements
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Hydra can use its tentacles for capturing its prey
and also use them for locomotion
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The above observations suggest
that movements and locomotion cannot be studied separately
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Methods of locomotion
performed by animals vary with their habitats and the demand of the
situation
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TYPES OF MOVEMENT:
Cells of the human body exhibit three main types of movements,
namely, amoeboid, ciliary and muscular
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It is effected by pseudopodia formed by the streaming of

protoplasm (as in Amoeba)
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Ciliary movement occurs in most of our internal tubular organs which
are lined by ciliated epithelium
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Passage of
ova through the female reproductive tract is also facilitated by the
ciliary movement
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The contractile property of muscles is
effectively used for locomotion and other movements by human
beings and majority of multicellular organisms
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MUSCLE:
The cilia and flagella are the outgrowths of the cell membrane
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Muscle is a specialised tissue
of mesodermal origin
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They have special properties
like excitability, contractility, extensibility and elasticity
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Based on their location,
three types of muscles are identified: (i) Skeletal (ii) Visceral and (iii)
Cardiac
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They have a striped appearance under the microscope
and hence are called striated muscles
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They are primarily involved in locomotory
actions and changes of body postures
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They do not exhibit any striation and are smooth in appearance
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Their
activities are not under the voluntary control of the nervous system
and are therefore known as involuntary muscles
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As the name suggests, Cardiac muscles are the muscles of heart
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Based on appearance, cardiac muscles are striated
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SKELETAL MUSCLE:
Each organised skeletal muscle in our body is made of a number of
muscle bundles or fascicles held together by a common collagenous
connective tissue layer called fascia
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Each muscle fibre is lined by the plasma
membrane called sarcolemma enclosing the sarcoplasm
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The
endoplasmic reticulum, i
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, sarcoplasmic reticulum of the muscle
fibres is the store house of calcium ions
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Each myofibril has alternate dark and light bands on it
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The light bands contain actin and is
called I-band or Isotropic band, whereas the dark band called ‘A’ or
Anisotropic band contains myosin
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Actin filaments are thinner as compared to the
myosin filaments, hence are commonly called thin and thick
filaments respectively
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The thin filaments are firmly attached
to the ‘Z’ line
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The ‘A’ and ‘I’ bands are arranged alternately
throughout the length of the myofibrils
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In a resting state, the edges
of thin filaments on either side of the thick filaments partially overlap
the free ends of the thick filaments leaving the central part of the
thick filaments
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Describe: Structure of Contractile Proteins
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Each ‘F’ actin is a polymer of
monomeric ‘G’ (Globular) actins
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A
complex protein Troponin is distributed at regular intervals on the
tropomyosin
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Each myosin (thick) filament is also a polymerised protein
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Each meromyosin has two important parts, a globular head

with a short arm and a tail, the former being called the heavy
meromyosin (HMM) and the latter, the light meromyosin (LMM)
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e
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The globular
head is an active ATPase enzyme and has binding sites for ATP and
active sites for actin
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Muscle contraction is initiated by a signal sent by the central nervous
system (CNS) via a motor neuron
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The junction
between a motor neuron and the sarcolemma of the muscle fibre is
called the neuromuscular junction or motor-end plate

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