Chapter 20 locomotion and movement

Biology by Kailash Sir,
Chapter20:locomotionandmovement.
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CHAPTER 20: LOCOMOTION AND MOVEMENT.
Locomotion
It is defined as the ability of the body to move from one place to another. For Example: Walking, Moving, Jumping,
Crawling, Propelling etc.
Difference between Movement and Locomotion
Movement can be at organism level, tissue level as well as cell level. For Example: Cell moves from one place to
another at the time of embryo formation. Whereas Locomotion is termed as movement of a body from one axis to
another (or many) in terms of co-ordinates.
It has to be noted that Movement of cell from one place to another cannot be considered as Locomotion. Movement, on
one hand, can be voluntary or involuntary. Whereas locomotion is always voluntary in nature.
Locomotor Movements
Movements that occur over some distance is known as locomotor Movements. For Example: walking, running, etc.
Locomotion always occurs at the organism level. Locomotion involves locomotory organs that help the body to move
from one place to another. Locomotion is always voluntary.
Types of Movement
The three main types of movements are as follows:
 Ciliary Movement occurs in internal organs that are lined by ciliated epithelium.
For Example: movement of ova in oviduct.
 Amoeboid Movement occurs by streaming of the protoplasm as observed in amoeba. It occurs in macrophages and
leucocytes (cells of the immune system).
 Muscular Movement occurs in humans that help them to move.
Types of Muscles
There are three types of muscles as given below:
 Skeletal Muscles appear striped/striations in the microscope. These are voluntary muscles as they are under the
control of our will. They help in locomotion and changes in body postures.
 Cardiac Muscles are muscles associated with the heart. They help in rhythmic contraction and relaxation of the
heart. They also appear striped/striations in the microscope similar to the skeletal muscles.
 Smooth Muscles are involuntary muscles and cannot be controlled by our will. They are present in lining of the
alimentary canal, reproductive system etc. They do not exhibit characteristic stripes/striations.

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Ciliary Movement
Cilia are made up of proteins known as microtubules that help them to move. Ciliary Movement is the rhythmic,
sweeping movement of epithelial cell cilia, of ciliate protozoans, or the sculling movement of flagella, affected possibly by
the alternate contraction and relaxation of contractile threads (myoids) on one side of the cilium or flagellum.

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B) Skeletal system
Definition:
The hard protective or supportive part of the animal constitutes the skeletal system; study of skeleton is called
osteology.
Skeletal system consists of a framework of bone and a few cartilages.
Bone and cartilage are specialised connective tissues. The former has a very hard matrix due to calcium salts
in it and the latter has slightly pliable matrix due to chondroitin salts. In human being: this system is made up
of 206 bones and a few cartilages. It is grouped into two principle division the axial and the appendicular
skeleton.

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Axial skeleton comprises 80 bones distributed along the main axis of the body. The skull, vertebral Colum
sternum and ribs constitute axial skeleton.
The skull is composed of two sets of bones - cranial and facial, that totals to 22 bones. Cranial bones are 8
in number. They form the hard protective outer covering, cranium for the brain. The facial region is made up
of 14 skeletal elements which form the front part of the skull. A single U-shaped bone called hyoid is present
at the base of the buccal cavity and it is also included in the skull.
Bones of Cranium
Frontal: Forms the fore head (anterior or front part of the top of cranium) and some upper parts (roofs) of eye
orbits or sockets and nasal cavities. A new-born infant displays a faint suture in midline of frontal, indication

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that adult frontal is actually formed of two completely fused frontal. Frontal suture between two frontal
disappear by age 6 years. It persists throughout life it is referred as metopic sutures.
Parietals: Articulated to and situated just behind frontal. Form the main parts of bulging top and sides of
cranium.
Occipital: Articulated to and situated just behind parietals, Forms posterior (back) and lower (base) parts of
cranium. Foramen magnum is a large perforation in this bone. On each side of the foramen, the occipital
bears a prominent elevation called occipital condyle. The condyles articulate the skull with first vertebra
(atlas). Thus, human skull is dicondylic,
Temporal: Form lower parts of right and left sides of cranium, as well as, the floor of cranial cavity. These
house structures of internal and middle ears and forma part of external auditory meatus. The middle ear of
each side encloses the three small ear ossicles' - malleus, incus and stapes. The mastoid process with
mastoid air cells in adult.
Sphenoid: A typically butterfly-shaped bone that forms the .middle and anterior parts of base of cranium in
front of occipital in the middle and temporals on the sides. It articulates with all skull bones, keeping these
firmly together. It also formsparts of lateral walls and floors of eye orbits.
Sphenoid with sella turcica depression for pituitary body.
Ethmoid: A small, irregular bone in front of sphenoid and behind nasal bones. It fashions the front (anterior)
extremity and closer of cranial cavity. It also contributes to the architecture of eye orbits and proximal parts of
nasal chambers.
Facial Bones
Nasals: Small, oblong bones in middle of upper part of face, forming proximal part of the bridge of our nose.
The remaining, lower part of our nose is formed of cartilage.
Inferior nasal conchae (Turbinales): Two highly coiled, scroll-like processes of ethmoid bone, called
conchae project into each nasal cavity from lateral wall of the proximal bony part of concerned nasal
chamber. One ethmoidal concha is superior (uppermost). The other one is called middle concha, because it is
followed by a thin, separate scroll like bone which is named inferior nasal concha or turbinate.
Vomer: A thin, elongated, plate like bone, forming a part of the septum which separates the two nasal
cavities.
Lachrymal: Small and thin, finger-shaped bones, each located in front part of the medial (inner) side of
corresponding eye orbit. These form a part of the passages of corresponding tear ducts.
Zygoma tics (Malars): Cheek-bones; form the prominences of our cheeks and parts of the floor and side
walls of eye orbits.
Palatines: L-shaped bones that form the back (posterior) part of our hard palate (roof of mouth). Also
contribute to the framework of nasal cavities and floor of eye orbits.
Maxillae: Large, upper jaw bones that form the major part of our face and upper jaw. Comprise entire front
(anterior) part of our hard palate. Also contribute to the architecture of eye orbits and nose. Bear the teeth of
upper jaw.

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Mandible: Largest bone of our face, and strongest of all bones of the body. Forms entire lower jaw and bears
all lower jaw teeth. Articulated with temporal bones of skull. Only skull bone that moves.
The skull region articulates with the superior region of the vertebral column with the help of two occipital
condyles (dicondylic skull).
Vertebral Column
It is our backbone which extends in the mid axis of the back (posterior) part of our trunk from head to the
lower (inferior) extremity of trunk. Together with the sternum and rib, it forms the supporting frame work of our
trunk. It support and rotate the head, suspends the viscera, protect vital organs, provides attachment to limb
girdles, facilitates some movement of the trunk and houses the spinal cord. Vertebral column makes two-fifth
of total weight of body.
Curvatures of vertebral column: In a foetus, there is only a Single anteriorly concave curve, in adult there
are 4 curves like, cervical, thoracic, lumber, and sacral. Cervical and lumber are anteriorly 'convex, while
thoracic and sacral are anteriorly concave. At approximately 3rd month after birth, when an infant begins to
hold its head erect, cervical curves develops, Later, when the child sits up, stands, and walks, the lumber
curves further develops. The thoracic and 'sacral curves retains anterior concavity of foetus, thus are called
'Primary curves'. The cervical and lumber curves are modification of the original foetal curves, are called'
"Secondary curves ".
The curves of vertebral column are important because they increases its strength, help maintain balance in
upright position absorb shock during walking and running and help protect the column from fracture. Certain
abnormalities of curvature are:
Kyphosis: Exaggeration of thoracic curve, resulting in "round-shouldered" appearance, also called hunch
back.
Lordosis: An exaggeration of lumber curve, also called sway back.
Scoliosis: An abnormal lateral curvature in any region of spine.
The Vestigeal notochord called nucleus pulposes is found in intervertebral disc. Inter-vertebral disc is fibro
cartilagenous disc present between centrum of vertebrate.
Our vertebral column is formed by 26 serially arranged units called vertebrae and is dorsally placed. It
extends from the base of the skull and constitutes the main framework of the trunk. The vertebral column is
differentiated into cervical (7), thoracic (12), lumbar (5); sacral (1- fused) and coccygeal (1-fused) regions
starting from the skull.

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Atlas Vertebra
(i) First cervical vertebra.
(ii) Body is formed of vertebral arch transverse process:
(iii) It supports the globe of the head like the earth by the atlas (super man).
(iv) Centrum is absent.
(v) Neural spine absent.
(vi) Transverse process are long with transverse foramen.

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Thoracic Vertebra
(i) Centrum acoelus.
(ii) Neural canal is formed by union of two neural arches.
(iii) Neural spine is a flat & long directed backward.
(iv) Club shaped transverse process.
(v) Neural arch with superior articular process.'
(vi) Twodemifacets for articulation of head of a rib are present.
Lumber Vertebra
(i) Centrum acoelus.
(ii) Neural spine well developed.
(iii) Transverse process are thin and long.

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(iv) Small accessory process present near the root of each transverse process.
(v) It is the largest vertebrae.
Sacrum: It is a triangular bone formed by fusion of 5 sacral vertebra.
(i) Fusion normally begins between 16 to 18 years of age and is completed by 30 yrs. of age.
(ii) Serves as strong foundation for pelvic girdle.
(iii) Sacrum with 4 pairs of anterior and posterior sacral "foramina.
(iv) Lateral part of sacrum articulate with ilium of hip bone.
(v) Female sacrum is shorter, wider and more curved between 52 and 53 the male sacrum is longer,
narrower, and less curved.
(vi) In birds some of the vertebrae are fuse to form synsacrum. [Last thoracic+ Lumber+ Sacral+ One or two
caudal]
Coccyx
(i) It is formed by fusion of four coccygeal vertebrae.
(ii) It is last section of backbone.
(iii) It is small triangular bone.
(iv) Rudimentary transverse process.
(vi) Fusion generally occurs between 20 and 30 years of age.

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The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for
the ribs and musculature of the back.
Ribs
The ribs are curved bars, which movably articulate with the thoracic vertebrae at the back and while with the
sternum in front.
All collectively forming a bony cage, the thoracic basket.
There are 12 pairs of ribs.
Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum.
It has two articulation surfaces on its dorsal end and is hence called bi-cephalic.
First seven pairs of ribs are called true ribs. Dorsally, they are attached to the thoracic vertebrae and ventrally
connected to the sternum with the help of hyaline cartilage.
The 8th, 9th and 10th- pairs of ribs do not articulate directly with the sternum but join the seventh rib with the
help of hyaline cartilage.
These are called vertebrochondral (false) ribs. Last 2 pairs (11th and 12th) of ribs are not connected ventrally
and are therefore, called floating ribs.
Thoracic vertebrae, ribs and sternum together form the rib cage.

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The ribs serve three important functions
a) They protect the heart, large blood vessels and lungs.
b) They bear respiratory muscle (external and internal intercostal muscle).
c) Lower two pair of ribs protect the kidney. (11th and 12th)
Sternum
It is bone of chest.
It is associated with pectoral girdle in amphibia.
In man it is made up of cervical manubrium (presternum), mesosternum and xiphoid process (Metasternum).
Manubrium is broad and thick.
Mesosternum is made up fine sternabae.
Metasternum is represent by xiphisternum which is smallest broad and thin. In mammal a cartilagenous plate
attached with xiphisternum is known as xiphoid cartilage (hyaline).
Sternum = Manubrium + 5 sternabrae + Xiphisternum.
The sternum has two functions:
o It takes part in the formation of the 'protective thoracic basket.
o It plays a role in the respiratory mechanism.
Bones of the limbs along with their girdles
The bones of the limbs along with their girdles constitute the appendicular skeleton. Each limb is made of 30
bones. The bones of the hand (fore limb) are humerus, radius and ulna, carpals (wrist bones - 8 in number),

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metacarpals (palm bones - 5 in number) and phalanges (digits -14 in number). Femur (thigh bone - the
longest bone), tibia and fibula, tarsals (ankle bones - 7 in number), metatarsals (5 in number) and phalanges
(digits - 14 in number) are the bones of the legs (hind limb). A cup shaped bone called patella covers the knee
ventrally (knee cap).
Pectoral and pelvic girdle bones
Pectoral and pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with
the axial skeleton. Each girdle is formed of two halves. Each half of pectoral girdle consists of a clavicle and a
scapula. Scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second
and the seventh ribs.
The dorsal, flat, triangular body of scapula has a slightly elevated ridge called the spine which projects as a
flat, expanded process called the acromion.
The clavicle articulates with this. Below the acromion is a depression called the glenoid cavity which
articulates with the head of the humerus to form the shoulder joint.
Each clavicle is a long slender bone with two curvatures. This bone is commonly called the collar bone.
Pelvic girdle consists of two coxal bones.
Each coxal bone is formed by the fusion of three bones - ilium, ischium and pubis. At the point of fusion of the
above bones is a cavity called acetabulum to which the thigh bone articulates.
The two halves of the pelvic girdle meet ventrally to form the pubic symphysis containing fibrous cartilage.

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Limb bones: Limb are of two types fore limb and hind limb,
Bones of Fore Limbs
a) Humerus or arm bone or bone of upper arm, is longest and largest bone of upper limb.
b) It articulates proximally with scapula and distally at the elbow with both ulna and radius.
c) Humerus proximal" end with greater and lesser tuberosity tubercle.
d) Both radius and' ulna are with nutrient foramina.
e) Radius present towards thumb side.
f) Ulna present towards little finger side.
g) It includes humerus + radius & ulna + carpals + meta .carpals + Phalanges.
h) Humerus is characterised by presence of deltoid tuberocity for the attachment of muscles.
i) Distal end of humerus at the elbow joint is like pully and called trochlea. Its groove is called olecranon
fossa whose basal part is marked by a supratrochlear foramen for the passage of brachial artery and nerve.
j) Humerus is characterised by arterial foramen.
k) Head of the humerus articulate with glenoid cavity of pectoral girdle.
l) Radius is smaller and ulna is larger, were bones of fore arm.
m) Sphinoid process is present in distal end of ulna and radius both.
n) Olecranon process is present in ulna. Proximally, which forms prominence of elbow.
o) Trochlear notch is formed by ulna which is also known as sigmoid notch.
p) Carpals or wrist bone are eight in number, joined to one another by ligaments. Carpals are arranged in 2
rows, with 4 bones in each row.
q) Metacarpals are five in number, and phalanges are - fourteen, phalanges formula = 2, 3, 3, 3, 3.

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Note:
(a) Arm - Brachium - Humerus = 1 bone
(b) Fore arm - Antibrachium - Radius + Ulna =-2 bone
(c) Wrist-Carpus = 4 + 4 carpals = 8 bone
(d) Palm - Metacarpals - 5 metacarpals = 5 bone
(e) Fingers - Phalangeal formula - 2 3 3 3 3 = 14 bone
Total = 30 bone
In upper arm total 30 bones are present.
Bones of Hind Limbs
a) It includes Femur + Tibia and Fibula + Tarsals + Metatarsals + Phalanges
b) Fovea capitis is depression in head of femur.
c) Femur is longest and strongest bone of body.
d) Femur is known as bone of thigh
e) Greater trochenter, lesser trochenter 3rd trochonter are present in femur, of thigh and buttock muscles.
f) Patellar groove in found in distal end of femur.
g) Fibula is smaller and associated with knee joint.
h) Tibia is larger, also called shin bone. It bears a weight of body.
i) Tarsal bones are seven.

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j) Metatarsals are five.
k) Phalanges are fourteen.
l) Phalanges formula = 2, 3, 3, 3, 3
m) Patella form knee cap.
n) Patella is formed by sesamoid bone. Fabella is also example of sesamoid bone.
o) Thumb of foot is called hallux.
p) Ankle bones have 7 tarsals and arranged in two rows then 1st row have talus and calcaneus, second row
with cuboid, Navicular, and I, II, III cuneiform.
Joints
Joints are points of contact between bones, or between bones and cartilages.
Force generated by the muscles is used to carry out movement through joints where the joint acts as a
fulcrum. The movability at these joints vary depending on different factors.
Joints have been classified into three major structural forms, namely, fibrous, cartilaginous and synovial.
Fibrous joints do not allow any movement. This type of joint is shown by the flat skull bones which fuse
end-to-end with the help of dense fibrous connective tissues in the form of sutures, to form the cranium.
In cartilaginous joints, the bones involved are joined together with the help of cartilages. The joint between
the adjacent vertebrae in the vertebral column is of this pattern and it permits limited movements.
Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating
surfaces of the two bones. Such an arrangement allows considerable movement.
These joints help in locomotion and many other movements.
Ball and socket joint (between humerus and pectoral girdle),

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Hinge joint (knee joint), Pivot joint (between atlas and axis),
Gliding joint (between the carpals) and
Saddle joint (between carpal and metacarpal of thumb) are some examples.
Synovial joint.
Movable joints are called synovial joints.

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Synovial joints have a synovial or joint cavity, a space between articulating bones.
Articular cartilage covers the surface of articulating bones.
Articular cartilage of synovial joints is hyaline cartilage.
Synovial joints are surrounded by a tubular articular capsule.
The articular capsule consists of two layers; outer fibrous capsule and inner synovial membrane.
The synovial membrane secretes synovial fluid which lubricates and provides nourishment to articular
cartilage.
In old age, stiffness of joints is due to the decrease in synovial fluid.
Structural arrangement of a perfect joint permits considerable movement of articulating bones without danger
of friction.
Due to the elasticity of the ligaments of the wall of joint capsule, articulating bones automatically return back
to their normal positions after movements.
Sprain is caused by excessive stretching of ligament at the joint. It causes pain and swelling,
Dislocation between two bones may occur when ligament ruptures or it is turned and the bones are
displaced.
In human vertebrae are grouped into five groups namely cervical, thoracic, lumber, sacrum, coccygeal
Fig. Typical synovial joint

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Muscles system
Muscle is a specialised tissue of mesodermal origin. About 40-50 per cent of the body weight of a human adult is
contributed by muscles. They have special properties like excitability, contractility, extensibility and elasticity.
Muscles have been classified using different criteria namely location, appearance and nature of regula Han of their
activities. Based on their location, three types of muscles are identified:
Types of Muscles
 Skeletal
 Visceral
 Cardiac
Skeletal Muscles
 Unbranched.
 Multinucleated,
 Skeletal Muscles are closely associated with the skeletal components of the body.
 They have alternate light and dark bands, (striations) and hence are caned striated muscles
 As their activities are under the voluntary control of the nervous system, they are known as voluntary muscles
too.
 These muscles are attached to skeleton with help of tendons.
 They are primarily involved in locomotory actions and changes of body postures.
 Dark bands are known as A- Bands, and light bands are known as I-Bands.
 Cytoplasm present in the cell is known as sarcoplasm.
 Plasma membrane of muscle cell known as sarcollema.
 Endoplasmic reticum present in the cell known as sarcoplasmic reticulum.
 sarcoplasmic reticulum acts as storage place for calcium ions which are required for muscle contraction.

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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 (non-striated 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.
Cardiac Muscles
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.
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.
Each muscle bundle contains a number or muscle fibres, Each muscle fibre is lined by the plasma membrane called
sarcolemma enclosing the sarcoplasm.
Muscle fibre is a syncytium as the sarcoplasm contains many nuclei. The endoplasmic reticulum, i.e., sarcoplasmic
reticulum of the muscle fibres is the store house of calcium ions.
Structure of Muscles
Structure of myosin & actin.
Sliding filament theory of muscle contraction.
Mechanism of muscle contraction.
Energy for muscle contraction.
Cories cycle.
Red and white muscle fibre.

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A characteristic feature of the muscle fibre is the presence of a large number of parallelly arranged filaments in the
sarcoplasm called myofilaments or myofibrils.
Each myofibril has alternate dark and light bands on it. A detailed study of the myofibril has established that the striated
appearance is due to the distribution pattern of two important proteins - Actin and Myosin.
The light bands contain actin and is called I-band or Isotropic band, whereas the dark band called 'A' or Anisotropic
band and contains myosin.
Both the proteins are arranged as rod-like structures, parallel to each other and also to the longitudinal axis of the
myofibrils.
Actin filaments are thinner as compared to the myosin filaments, hence are commonly called thin and thick filaments
respectively.
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.

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Structure of contractile protein.
Each actin (thin) filament is made 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. Each myosin (thick) filament
is also a polymerisedprotein,
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). The HMM component, i.e.; the head and short arm projects outwards at regular distance and angle
from each other from the surface of a polymerised myosin 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.

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Mechanism of Muscle Contraction
Mechanism of muscle contraction is best explained by the sliding filament theory which 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 constitutes 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 (Acetyl choline) which generates an action potential
in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.
Increase in Ca++
level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove
the masking of active sites for myosin.

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Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross
bridge. 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, i.e., contraction, the ‘I’ bands get reduced, whereas the' A' bands retain the length.
The myosin, releasing the ADP and P 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. Repeated activation of the muscles
can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen in them, causing fatigue.
Muscle contains a red coloured oxygen storing pigment called myoglobin. Myoglobin content is high in some of the
muscles which give 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.
Some of the muscles possess very less quantity of myoglobin and therefore, appear pale or whitish.
These 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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The muscles that act together to produce a movement are called synergists and the muscle that act in opposition to each
other are antagonists.
The muscles that act most powerfully during any given movements are called prime movers.
Flexor and Extensor: Muscles that bend one part over another joint is called flexor. Extensor muscle is antagonist of
flexor muscle. The contraction of an extensor extends a joint by pulling one of the articulating bone apart from another.
(ii) Pronator and Supinator: The contraction of a pronator rotates the forearm to turn the palm downward or backward.
Supinator is antagonist of pronator. A supinator contracts to rotate the forearm and thus to make palm face upward or
forward.
(iii) Abductor and Adductor: An abductor contracts to draw a bone away from the body midline. Muscle that brings the
limb away from midline is called abductor. An adductor draws a bone towards the body midline. Muscles that brings the
limb towards midline is called adductor. Abductor muscle is antagonist of adductor muscle. Abduction is elevation and
adduction is depression.

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(iv) Protractor and Retractor: Protractor muscle pulls the lower jaw, tongue and the head forward. Retraction is
opposite to protaction. Retractor muscle draws the lower jaw, tongue and the head backward.
(v) Inversion and Eversion: Turning of feet so that the soles face one another in inversion. Eversion is the opposite of
inversion. In this movement, the soles of the feet face laterally.
(vi) Rotation: Rotation is term that indicates the partial revolving of a body .part on the part's long axis.
(vii) Arrector: Raises hairs of skin.

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Disorders of Muscular and Skeletal System
Myasthenia gravis: Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening
and paralysis of skeletal muscle.
Muscular dystrophy: Progressive degeneration of skeletal muscle mostly due to genetic disorder.
Tetany: Rapid spasms (wild contractions) in muscle due to-low Ca++
in body fluid.
Arthritis: Inflammation of joints.
Osteoporosis: Age-related disorder characterised by decreased bone mass and increased chances of
fractures. Decreased levels of oestrogen are a common cause.
Gout: Inflammation of joints due to accumulation of uric acid crystals.
Sprain: Sprain refers to injury to a joint capsule, typically involving a stretching or tearing of tendons or
ligaments. Unfortunately, both these structures have much poorer regenerative power than bone, and once
stretched often remain weak. Sprain is often considered a minor disorder, but it may become chronic.
Fracture: Fracture is a break of a bone. Fracture occurs rarely in children. The bones of children have a large
quantity of organic matter and are, therefore, very flexible and less likely to break. With advancing age,
mineral matter (calcium phosphate) is deposited in the bones. This decreases the organic matter, making the
bones hard and brittle. Thus, old people are more liable to fracture of bones. Bones fractures are of many
types.
(a) Green-stick fracture or complete: It is merely a crack. The bones remains partly intact, occurs only in
children.
(b) Simple or complete fracture: Bone breaks completely into two parts which remain close to each other.
(c) Comminuted fracture: Bone breaks into more than two pieces (smaller fragments between two main
fragments)
(d) Compound fracture: Bone breaks completely but a fragment pierces out through the skin.
(e) Evulsive fracture: A small piece breaks off fully from the bone but remains attached to the ligament.
Fractures need surgical treatment for healing and should be promptly and properly attended to.
Note
In man total no. of muscles presents 656 muscles
Bone of lower jaw - Mandible.
Strongest - bone of axial skeleton = Mandible (Lower jaw)
Neurocranium - A part of skull having brain and sensory capsules.
Sellaturcica - Depression in sphenoid of skull that lodges pituitary body.
Wish bone - It is V-shaped bone formed by the fusion of clavicle and inter clavicle in bird. It is also named as
Merry thought bone.)
Largest foramen - Foramen of magnum at the base of cranium from where brain enters into spinal cord.
Weberian Ossicles - Small bones developed from 1st four vertebrae of bony fishes like carp and cat fish.
These connect air bladder to internal ear and act as a barometer)
Smallest bone - Stapes
Longest bone – Femur

Chapter 20 locomotion and movement

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