LOCOMOTION AND MOVEMENT (MUSCLES)

INTRODUCTION
• Movement is one of the significant features of living beings.
• Animals and plants exhibit a wide range of movements.
• Streaming of protoplasm in the unicellular organisms like Amoeba is a simple form of movement.

• Movement of cilia, flagella and tentacles are shown by many organisms.

• Human beings can move limbs, jaws, eyelids, tongue, etc.

Movement of limbs Movement of jaws Movement of eyelids Movement of tongue

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Locomotion and Movement (Muscles)

• Some of the movements result in a change of place or location. Such voluntary movements are
called locomotion. Walking, running, climbing, flying, swimming are all some forms of locomotory
movements.

Walking Running Climbing Flying Swimming

• Locomotory structures need not be different from those affecting other types of movements.
For example, in Paramoecium, cilia helps in the movement of food through cytopharynx and in
locomotion as well.
Ciliary movements in our respiratory tract.

• Hydra can use its tentacles for capturing its prey and also use them for locomotion.

• We use limbs for changes in body postures and locomotion as well.

• The above observations suggest that movements and locomotion cannot be studied separately.
• The two may be linked by stating that all locomotions are movements but all movements are not
locomotions.
• Locomotion is generally for search of food, shelter, mate, suitable breeding grounds, favourable
climatic conditions or to escape from enemies/predators.

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Locomotion and Movement (Muscles)

Question-1: Streaming of protoplasm is a movement exhibited by –

(1) Paramecium (2) Hydra
(3) Amoeba (4) Euglena
Answer: (3) Amoeba

Question-2: Locomotory structure in paramecium is.

(1) Flagella (2) Cilia
(3) Pseudopodia (4) Tentacles
Answer: (2) Cilia

Question-3: Some of the movements result in a change of place or location. Such voluntary
movements are called-
(1) movement (2) change of position
(3) translocation (4) locomotion
Answer: (4) locomotion

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Locomotion and Movement (Muscles)

TYPES OF MOVEMENTS
• Cells of human body exhibit mainly three types of movements
(1) Ciliary
(2) Amoeboid
(3) Muscular

(1) CILIARY MOVEMENT

• It occurs in most of our internal organs which are lined by ciliated epithelium.
e.g. The coordinated movements of cilia in the trachea help us in removing dust particles and
some of the foreign substances inhaled along with the atmospheric air.
Passage of ova through the female reproductive tract is also facilitated by the ciliary movement.

(2) AMOEBOID MOVEMENT

• Some specialised cells in our body like macrophages and leucocytes in blood exhibit amoeboid
movement.
• It is effected by pseudopodia formed by the streaming of protoplasm (as in Amoeba).
• Cytoskeletal elements like microfilaments are also involved in amoeboid movement.

(3) MUSCULAR MOVEMENT

• Locomotion requires a perfect coordinated activity of muscular, skeletal and neural systems.
• The contractile property of muscles are effectively used for locomotion and other movements by
human beings and majority of multicellular organisms.
• Movement of our limbs, jaws, tongue etc. require muscular movement.

Question-1: Cells of human body does not exhibit which of the following type of movement?
(1) flagellated (2) ciliary (3) muscular (4) amoeboid
Answer: (1) flagellated

Question-2: In the trachea __________ help us in removing dust particles and some of the foreign
substances inhaled along with the atmospheric air.
(1) villi (2) microvilli (3) cilia (4) brush border epithelium
Answer: (3) cilia

Question-3: Movement of our limbs, jaws, tongue etc. require -

(1) joints (2) muscles (3) tendons (4) ligaments
Answer: (2) muscles

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Locomotion and Movement (Muscles)

• Multicellular animals movements are the result of a special kind of tissue called muscular tissue
(muscle).
• Study of muscles known as Myology/Sarcology.

ORIGIN OF MUSCLES
• Origin of muscles is - mesoderm except few muscles.
• Muscle of Iris, ciliary body & myoepithelial cell of sweat gland develop from Ectoderm.
• Main characteristics of muscle are excitability, contractility and extensibility.
• Muscles constitutes around 40% to 50% of adult body mass in an average healthy person.
• Three types of muscles are found in the body. (On the basis of position/location)

Muscle

(i) Voluntary or (ii) Visceral (iii) Cardiac

skeletal muscles or muscles
muscles Involuntary or
smooth muscles

SKELETAL MUSCLES
• Skeletal muscles are closely associated with the skeletal components of the body.

• They have a striped appearance under the microscope and hence are called striated muscles.

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• As their activities are under the voluntary control of the nervous system, they are known as
voluntary muscles too.

• They are primarily involved in locomotory actions and changes of body postures.

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VISCERAL MUSCLES
• Visceral muscles are located in the inner walls of hollow visceral organs of the body like the
alimentary canal, reproductive tract, etc.

• They do not exhibit any striation and are smooth in appearance. Hence, they are called smooth
muscles (nonstriated muscle).
• Their activities are not under the voluntary control of the nervous system and are therefore known
as involuntary muscles.
• They assist, for example, in the transportation of food through the digestive tract and gametes
through the genital tract.

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CARDIAC MUSCLES
• As the name suggests, Cardiac muscles are the muscles of heart.
• Many cardiac muscle cells assemble in a branching pattern to form a cardiac muscle.
• Based on appearance, cardiac muscles are striated.
• They are involuntary in nature as the nervous system does not control their activities directly.
• It is special type of muscle which found only in heart so it is also called as cardiac muscle. On the
basis of structure it is striated type of muscle. Intercalated disc, helps in the propagation of impulse
& contraction.
• Their muscle fibres are long, cylindrical and branched.
• Many transverse septa are found in the muscle fibre which are called as intercalated disc.
• Due to septa fibres are divided into many segments each segment is uninucleated. Each segment
called individuals cells.
• Dark & light line also found in the Muscle fibre. It is also non-fatigue type muscle.
• Its contraction is not controlled by will power of animal.
• On the basis of function it is smooth muscle type.

Cardiac muscle fibres

Question-1: Origin of Muscles is-

(1) ectodermal (2) endodermal
(3) mesodermal (4) ecto-Endodermal
Answer: (3) mesodermal

Question-2: Activities of Smooth muscles is classified as-

(1) voluntary (2) involuntary
(3) both (4) none of the above
Answer: (1) involuntary

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STRUCTURE OF SKELETAL MUSCLES

Diagrammatic cross sectional view of a muscle showing muscle bundles and muscle fibres

Diagrammatic representation of anatomy of a muscle fibre showing a sarcomere

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Fine structure of muscle fibre :-

• Skeletal muscle fibre is cylindrical or tubular in shape and is long and Unbranched.
• The outer membrane of muscle fibre is called sarcolemma.
• This cell membrane contain collagen fibres.
• Each muscle fibre contain multinucleated sarcoplasm.
• Nucleus & sarcoplasm are found in peripheral part.
• Myofibril are arranged in parallel rows & form the dark & light line.
• These lines are found in alternate order.
• These lines are made up of actin & myosin protein. Both proteins are filamentous proteins.
• Actin filaments are thin while myosin filaments are thick.
• Light line or band is made up of only actin filament, these band are mono-refractive in polarised
light so it is called Isotropic band (I band).
• In the centre of each ‘I’ band is an elastic fibre called ‘Z’ line which bisects it.
• The thin filaments are firmly attached to the ‘Z’ line. The thick filaments in the ‘A’ band are also held
together in the middle of this band by a thin fibrous membrane called ‘M’ line.
• The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils. The portion of
the myofibril between two successive ‘Z’ lines is considered as the functional unit of contraction and
is called a Sarcomere.
• 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.
• This central part of thick filament, not overlapped by thin filaments is called the ‘H’ zone.
• Sarcomere is considered as the functional unit of contraction.
A-band
Z-Line Z-Line
H-ZONE

I- band M-line I- band

Actin filament Myosin filament
(thin filament) (thick filament)
Sarcomere
Sarcomere = 1A band + two half I band
The Length of Sarcomere is 2.5 µm.
(I band = 1µm, myosin = 1.5 µm)
• 1 Myosin filament is surrounded by 6 Actin filaments & 1 Actin filament is surrounded by 3 Myosin
filaments.
• Z-disc is made up of actinin protein.

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STRUCTURE OF CONTRACTILE PROTEIN

1. Actin (Thin) filament)
• Each actin (thin) filament is made up of two ‘F’ (filamentous) actins helically wound to each other.

• Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins.

• Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length.
• A complex protein Troponin is distributed at regular intervals on the tropomyosin.
• In the resting state a subunit of troponin masks the active binding sites for myosin on the actin
filaments.

An actin (thin) filament

Troponin is made up of three subunit.

(a) Troponin I (Inhibitory site)
(b) Troponin T (Tropomyosin site)
(c) Troponin C (Ca+2 binding site)

2. Myosin (Thick) Filament

• Each myosin (thick) filament is also a polymerised protein.
• Many monomeric proteins called Meromyosins constitute one thick filament.
• 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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Locomotion and Movement (Muscles)

• The HMM component, i.e.; the head and short arm projects outwards at regular filament and is
known as cross arm.
• The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for
actin.

Myosin monomer (Meromyosin)

Question-1: The store house of calcium ions in the muscle fibres is -

(1) epimysium (2) fascicle
(3) collagen fibres (4) sarcoplasmic reticulum
Answer: (4) sarcoplasmic reticulum

Question-2: Identify the correct labelling in the following diagram-

A

(1) fascicle (2) epimysium

(3) perimysium (4) syncitium
Answer: (3) perimysium

Question-3: This central part of thick filament, not overlapped by thin filaments is called-
(1) ‘H’ zone (2) ‘I’ zone
(3) ‘M’ Line (4) ‘A’ Band
Answer: (1) ‘H’ zone

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MECHANISM OF MUSCLE CONTRACTION :-

• Sliding filament theory - states that contraction
of a muscle fibre takes place by the sliding of the
thin filaments over the thick filaments.
• Muscle contraction is initiated by a signal sent by
the central nervous system (CNS) via a motor
neuron.
• A motor neuron along with the muscle fibres
connected to it constitute a motor unit.
• The junction between a motor neuron and the
sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate.
• A neural signal reaching this junction releases a neurotransmitter (Acetylcholine) which generates
an action potential in the sarcolemma.

• This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.
• This pulls the attached actin filaments towards the centre of ‘A’ band. The ‘Z’ line attached to these
actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction.
• During shortening of the muscle (contraction), the ‘I’ bands get reduced, whereas the ‘A’ bands
retain the length.

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Locomotion and Movement (Muscles)

• The binding of calcium with a subunit of troponin on actin filaments removes the masking of
active sites for myosin.
• Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on
actin to form a cross bridge.
• The myosin, releasing the ADP and P1 goes back to its relaxed state. A new ATP binds and the cross-
bridge is broken.
• The ATP is again hydrolysed by the myosin head and the cycle of cross bridge formation and
breakage is repeated causing further sliding.
• The process continues till the Ca++ ions are pumped back to the sarcoplasmic cisternae resulting in
the masking of actin filaments.
• This causes the return of ‘Z’ lines back to their original position, i.e., relaxation.

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ROLE OF ATP :-
(i) The 'back & forth' movement of myosin head with in the groove.
(ii) Detachment of myosin head from the actin.
• Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic
breakdown of glycogen in them, causing fatigue.

RED MUSCLE :-
• Myoglobin- A red coloured oxygen storing pigment.
• High myoglobin content of the muscles gives a reddish appearance. Such muscles are called the
Red fibres.
• These muscles also contain plenty of mitochondria which can utilise the large amount of oxygen
stored in them for ATP production.
• These muscles, therefore, can also be called aerobic muscles.

WHITE MUSCLE :-
• Absence of myoglobin gives it a pale or whitish appearance.
• Some of the muscles possess very less quantity of myoglobin and therefore are the White fibres.
• Number of mitochondria are also few in them, but the amount of sarcoplasmic reticulum is high.
• They depend on anaerobic process for energy.

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DIFFERENCE BETWEEN RED MUSCLE AND WHITE MUSCLE :-

Red (slow) muscle White (fast) muscle

1. Myoglobin content is high. So, it is 1. Myoglobin content is less So, it is
red pale
2. Sarcoplasmic reticulum is less 2. Sarcoplasmic reticulum is more
extensive extensive
3. Blood vessels are more extensive 3. Blood vessels are less extensive
4. Mitochondria are more in number 4. Mitochondria are less in number
5. Response is slow with long latent 5. Response is rapid with short latent
period period
6. Contraction is less powerful 6. Contraction is more powerful
7. This muscle is involved in prolonged 7. This muscle is not involved in
and continued activity as it undergoes prolonged and continued activity
sustained contraction as it relaxes immediately
8. Fatigue occurs slowly 8. Fatigue occur quickly
9. Depends on cellular respiration for 9. Depends on anaerobic process for
ATP production so also called aerobic energy.

Question-1: The neuromuscular junction or motor-end plate comprises of :-

(1) The junction between a sensory neuron and the sarcolemma of the muscle fibre
(2) The junction between a motor neuron and the sarcolemma of the muscle fibre
(3) The junction between a motor neuron and sensory neuron
(4) The junction between two muscle fibres
Answer: (2) The junction between a motor neuron and the sarcolemma of the muscle fibre

Question-2: A neural signal reaching this junction releases a neurotransmitter (_______) which
generates an action potential in the sarcolemma. Identify the neurotransmitter :-
(1) Adrenaline (2) Serotonin
(2) Glutamate (4) Acetylcholine
Answer: (4) Acetylcholine

Question-3: The binding of calcium with a subunit of (__A__) on actin filaments removes the
masking of active sites for (__B__).
A B
(1) Troponin - Myosin
(2) Myosin - Tropomyosin
(3) Actin - Tropomyosin
(4) Troponin - Actin
Answer: (1) Troponin - Myosin

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