Download locomotion and movement

LOCOMOTION AND MOVEMENT
LOCOMOTION AND MOVEMENT
Chapter outline
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Prerequisites
Learning objectives
Types of Movement
Muscle
Skeletal System
Joints
Disorders of Muscular and SkeletalSystem
Summary
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LOCOMOTION AND MOVEMENT
Prerequisites
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Movement and locomotion takes place as a result of cooperation between the muscle and skeletal
system, hence the study of both is necessary. (Study of movement is called kinesiology).
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The two may be linked by stating that all locomotions are movements but all movements are not
locomotions.
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Movement is one of the important features of all living beings.
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Animals and plants exhibit a wide range of movements e.g. streaming of protoplasm in
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unicellular organisms like Amoeba is a simple form of movement.
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Movement of cilia, flagella and tentacles are shown by many organisms.
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Human beings can move limbs, jaws, eyelids & tongue etc.
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The power to move the body comes from contraction of skeleton muscles which contract by about
30-40% of their resting length.
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Levers in the body are rigid bones turning about a fixed point called pivot by means of muscle
contraction effort, resulting in the force which causes movement of load.
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Some of the movements result in a change of place. Such voluntary movements are called locomotion.
Walking, running, climbing, flying and swimming are all forms of locomotory movements. •
Locomotion involves the movement of whole body. Locomotory structures can also perform
movement (i.e.,) Dual role of locomotion and movement is performed by same structures.
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LOCOMOTION AND MOVEMENT
Example
1. Paramecium - cilia helps in the movement of food through cytopharynx and in locomotion.
2. Hydra uses tentacles for capturing prey and also locomotion.
3. Limbs are used for change in body posture and locomotion. Methods of locomotion in animals
vary with their habitats and the demand of the situation.
4. Locomotion is for search of food, shelter, mate, suitable breeding grounds, favourable
conditions or to escape from enemies.
Movement
Muscular movements
Locomotion
Non-muscular movements
Movement of body parts
Learning objectives
Study this chapter with the following learning objectives.
1. To recognize the need for movement and locomotion in living organisms.
2. To identify the types of movement and types of muscles.
3. To understand the mechanism of muscle contraction.
4. To know about the skeletal system.
5. To gain knowledge about the disorders of muscular and skeletal system.
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LOCOMOTION AND MOVEMENT
TYPES OF MOVEMENT
Cells of the human body exhibit 3 types of movements – amoeboid, ciliary and muscular.
1. Amoeboid Movement
some specialized cells in our body – macrophages
and leucocytes in blood exhibit amoeboid movement.
It is affected by pseudopodia formed by the streaming
of protoplasm (Amoeba). Cytoskeletal elements
like microfilaments are also involved in amoeboid
movement.
macrophages
leucocytes
2. Ciliary Movement
occurs in internal tubular organs which are lined by
ciliated epithelium. The co-ordinate 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 facilitated by ciliary movement.
3. Muscular Movement
ciliated epithelium
movement of limbs, jaws, tongue etc. require muscular movement. Contractile property of muscles is
effectively used for locomotion. Locomotion requires perfect coordinated activity of muscular, skeletal
and neural systems.
limbs
jaws
tongue
MUSCLE
Muscle is a specialized tissue of mesodermal origin. About 40-50% of the body weight of a human
is contributed by muscles. They have special properties like excitability, contractility, extensibility and
elasticity.
Muscles are responsible for the movements of hands and legs and several internal organs such as
intestine and heart. Small amount of muscle tissue is also present in blood vessels. They help in
increasing or decreasing the diameter of blood vessel and thus regulate the blood flow. Heart is made
of only muscle cells and they help in pumping the blood.
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LOCOMOTION AND MOVEMENT
Muscle cells have the capacity to shorten – this is
called contraction and generates enough force for
movement. The muscle remains contracted only for
a short time and returns to its original length. This is
called relaxation. Each muscle is supplied with a nerve.
Inside the muscle tissue, the nerve divides into several
branches so that each muscle cell is connected to
the nerve. When the nerve is stimulated, the stimulus
reaches each muscle cell in the tissue and the entire
muscle contracts at one time as a unit.
Fascicle
(muscle bundle)
Muscle fibre
(muscle cell)
Sarcolemma
Blood capillary
Muscle
1. Striated muscle
This is also called skeletal muscle as it is attached
to the bones by tendons in the skeleton and is
responsible for the movements. Movements of these
muscles are under our control. If we want, we can
move our hands or legs – hence these muscles are
also called voluntary muscles.
.
skeletal muscle
Each muscle has several long, thin and unbranched fibres like cells. Each cell is as long as the muscle.
These are several thin lines or striations across the muscle. Hence the name striated muscle. They are
involved in locomotion and changes of body postures.
Muscle contraction also produces heat. When the body is exposed to cold – we shiver, during shivering,
muscles contract and relax rapidly producing large amount of heat. This keeps the body warm.
2. Non-Striated Muscle
This muscle consists of short elongated spindle
shaped cells. These cells do not have striations.
Hence the name non-striated muscle or smooth
muscle. Contraction and relaxation of this muscle is
not under our control. Hence it is called involuntary
muscle. These muscles are present in the blood
vessels, intestine and other tissues which exhibit
involuntary movements. E.g: they assist in the
transportation of food through digestive tract and
gametes through genital tract.
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smooth muscle
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LOCOMOTION AND MOVEMENT
3. Cardiac muscle
As the name indicates, this muscle is present in the
heart and is responsible for pumping of blood. These
cells are long, branched and have nuclei. Cells are
joined to each other at their ends. All the muscle cells
in cardiac muscle have striations. Though it resembles
the striated muscle in its structure, it is involuntary
muscle.
Cardiac muscle
Structure of Skeletal Muscle
Each skeletal muscle is made of a number of
muscle bundles or fascicles held together by a
common collagenous connective tissue layer called
fascia. Each muscle bundle consists of a number
of muscle fibres. Each muscle fibre is lined by the
plasma membrane called sarcolemma enclosing the
sarcoplasm. Muscle fibre is a syncitium as
I band
A band
H zone
Sarcomere
the sarcoplasm contains many nuclei and mitochondria. The endoplasmic reticulum i.e., sarcoplasmic
reticulum of the muscle fibre is the store house of calcium ions.
A characteristic feature of the muscle fibre is the presence of large number of parallely arranged filaments
in the sarcoplasm called myofilaments or myofibrils. The myofibrils are stacked in compartments called
sarcomeres.
Each myofibril has alternate dark and light bands on it. The study of myofibril revealed that the striated
appearance is due to the distribution pattern of two proteins – Actin and Myosin. Both are contractile
proteins.
The light band contains Actin and is called ‘i’ band or isotropic band, whereas the dark band is called ‘A’
band or Anisotropic band and it 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. 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 2 successive ‘Z’ lines is considered as functional unit of
contraction and is called a sarcomere.
In the 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 filament. The central part of thick
filament, not overlapped by thin filaments is called the ‘H’ zone. 6
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Structure of Contractile Proteins
Each actin filament is made of 2 ‘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 ‘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. Skeletal muscle contains 70-100 mg of myosin / gm of fresh muscle weight. Myosin is a globular,
large asymmetric molecule. Each myosin filament is a polymerized protein. Many monomeric proteins
called meromyosins constitute one thick filament. Each meromyosin has 2 important parts a globular
head with a short arm and a tail, the former being called the heavy (HMM) meromyosin and the later,
the light meromyosin (LMM). The HMM component i.e,head and short arm projects outwards at regular
distance and angle from each other from the surface of a polymerized myosin filament and is known as
cross arm. The globular head has an active ATPase enzyme and has binding sites for ATP and active
sites for actin.
Actin binding
sites
ATP binding
sites
Troponin
F actin
Tropomyosin
Head
Cross arm
Myosin
actin
Actin filament
P
Myosin
filament
ADP
ATP
cross bridge
Breaking of cross bridge
Myosin head
Formation of cross bridge
P
ADP
Sliding/ rotation
Stages in cross bridge
Functions of Actin
1) Actin forms microfilament.
2) To give mechanical support to cells.
3) To allow motility in cells which undergo amoeboid motion and phagocytosis.
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Functions of Myosin
Biologically important properties of myosin are its ability to combine with actin. The complex is called
Actomyosin. The actin binding to myosin is highly specific. Physiologically when actin bind to myosin,
the muscle produces force.
Mechanism of Muscle Contraction
It is explained by sliding filament theory which states that contraction of a muscle fibre takes place by
the sliding of the thin filaments over thick filaments. Muscle contraction is initiated by a signal sent by central nervous system via motor neuron. A motor
neuron along with the muscle fibres connected to it constitutes a motor unit. The junction between a motor neuron and sarcolemma of muscle fibre is called neuromuscular junction
or motor end plate. A neural signal reaching this junction releases a neurotransmitter (Acetyl choline)
which generates action potential in the sarcolemma. This spreads through the muscle fibre and causes
the release of Calcium ions into sarcoplasm.
Increase in Ca++ level lead to the binding of Calcium with the subunit of troponin on actin filaments and
there by remove the masking of active sites for Myosin. Utilizing 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 and thus ‘i’ bands get reduced.
Whereas ‘A’ bands retain the length. The Myosin, releasing the ADP and Pi (inorganic phosphate) goes
back to its released state.
A new ATP binds and the cross bridge is broken. The ATP is hydrolysed by Myosin head and the cycle
of cross bridge formation and breakage is repeated causing further sliding. The process continues till
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. The reaction time of the fibres can vary in different muscles. 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 red colored O2 storing pigment called Myoglobin.
Myoglobin content is high in some of the muscles which give a reddish appearance. Such muscles are
called red fibres. These muscles contain plenty of mitochondria which can utilize large amount of O2
stored in them for ATP production. These muscles, therefore can also be called aerobic muscles.
On the other hand, 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 of energy.
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H zone
I band
A band
Relaxed
Z line
Contracting
Maximally
Contracting
Two sarcomeres
Mechanism of Muscle Contraction
Skeletal System
The vast majority of animals and human beings possess supportive structures. The design of supporting
structure contributes towards specific shape of the organism. Human body is supported by endoskeleton
composed of bones and cartilages. In human beings skeletal system is made up 206 bones and few
cartilages.
The functions of skeletal system are as follows:
1. Support: The skeleton provides a rigid frame work for the body and helps to maintain the shape
of the body; organs are attached to, and suspended from the skeleton.
2. Protection: The skeleton protects the delicate internal organs of the body. Cranium protects
the brain, vertebral column protects the spinal cord, ribs and sternum protects heart, lungs
and blood vessels.
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3. Locomotion: Skeleton serves as the basis for attachment of muscles. Parts of the skeleton acts
as levers on which muscles can pull.
4. Storage: Skeleton serves as store house of minerals such as Calcium and Phosphorus.
5. Formation of blood cells: The bone marrow forms RBC and WBC. In order to perform these functions, the skeleton should be strong and light that is why it is made up of hallow bones, which are
much stronger and save great deal of weight.
The skeleton can be divided into 2 main parts.
Axial skeleton and Appendicular skeleton
AXIAL SKELETON
It comprises of 80 bones distributed along the main axis of the body. The skull, vertebral column,
sternum and ribs constitute axial skeleton.
Skull
In skull, bones are 22 in number. The skull is a bony box consisting of cranium and face.
Cranium: Cranium consists of 8 flattened bones which are tightly interlocking forming a series of
immovable joints. They form a hard, protective outer covering for the brain. It also protects the olfactory
organs, middle and inner ear and the eyes. At the posterior end of the skull, there is a large opening, the
Foramen magnum through which the spinal cord passes. On either side of the Foramen magnum, there
is smooth rounded projection, the condyle that articulates with the first vertebra(Atlas).
Face: The front portion of the skull is the face. It is made up of 14 bones. A single U-shaped bone called
hyoid is present at the base of buccal cavity and is also included in the skull.
The skull region articulates with the superior region of the vertebral column with the help of two occipital
condyles.
Frontal bone
Sphenoid bone
Parietal bone
Ethmoid bone
Lacrimal bone
Nasal bone
Zygomatic bone
Maxilla
Temporal bone
Occipital bone
Occipital condyle
Mandible
Hyoid bone
Skull
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Vertebral column
It is commonly known as back bone and it is the main axis of the body. It is formed by serially arranged
bones called vertebrae and is dorsally placed. Vertebrae are placed end to end and separated by
intervertebral discs which are cushioning pads of fibrous cartilage. The vertebrae are held together by
ligaments which prevent their dislocation but permit a degree of movement, so that the vertebral column
as a whole is flexible. The vertebral column gives protection to the spinal cord. In man, there are 33 vertebrae. Each vertebra has central hallow portion (neural canal) through which
the spinal cord passes. The vertebrae are basically five types named according to the region they
occupy. These are as follows.
1)Cervical: Neck vertebrae (7) - the first, the Atlas
Cervical vertebra
support the skull and allow a nodding movement,
the second, and the Axis allows skull rotation.
2)Thoracic: Chest vertebrae (12) - connect with ribs
and the sternum, forming thoracic cage,
protecting heart and lungs and allowing respiratory
Thoracic
movements.
vertebra
3)Lumbar: Waist vertebrae (5) - strongly built.
4)Sacral: Hip vertebrae (5) - these are joined together
Intervertebral
to strengthen the sacrum.
disc
5)Caudal: Tail vertebrae (4) - these are fused in the
Lumbar
adult to form coccyx
vertebra
Sacrum
The complete vertebral column is arched in mammals
resembling bridge arch.
The limbs can be compared to the bridge pillar
Coccyx
supports.
Vertebral column
Structure of Typical Vertebra
The main body of the vertebra is called Centrum. Over the Centrum is the neural arch that provides
protection to the spinal cord which runs beneath it. The neural arch bears a median neural spine to which
strong muscles are attached. Two transverse processes project laterally from the base of the neural
arch. These processes provide additional surface for the attachment of muscles. The articular facets
arise from the anterior and the posterior ends of the Centrum. They provide surfaces for articulation with
the adjacent vertebrae.
Neural spine
transverse processes
Neural arch
articular Facets
spinal cord
Centrum
Typical Vertebra
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Sternum and Ribs
Sternum (Breast bone): Sternum is a flat narrow bone
located in the middle of the front part of the chest. The
first 10 pairs of ribs are directly or indirectly attached
to the sternum.
Ribs: There are 12 pairs of ribs which are flat, long
and curved. The thoracic vertebrae at the dorsal side,
the sternum or the breast bone on the ventral side and
the ribs on the sides together form thorax or ribcage.
Each rib articulates with vertebra by double head and is
attached to sternum by flexible cartilage. The first seven
pairs of ribs are called true ribs. They are attached to
the thoracic vertebrae dorsally and ventrally connected
to the sternum with the help of hyaline cartilage.
Sternum
Ribs
Ribs
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 or false ribs. Last 2 pairs (11th and 12th)
of ribs are connected ventrally and are therefore called floating ribs.
APPENDICULAR SKELETON
The bones of the limbs along with their girdles constitute appendicular skeleton. Each limb is made of
30 bones. This consists of 2 girdles (pectoral and pelvic) and limbs.
Pectoral girdle
Each girdle is formed of two halves. Each half of pectoral girdle consists of a clavicle or collar
bone and flat scapula or shoulder bone. Scapula is a large triangular flat bone situated in the dorsal
part of the thorax between the 2nd and 7th 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
process. The clavicle articulates with this.
Below the acromion is a depression called glenoid cavity which articulates with the head of 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 (hip girdle)
It consists of two coxal bones. Each coxal bone is formed by the fusion of 3 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 pubic symphysis containing
fibrous cartilage.
Pentadactyl limbs
The skeleton structure of the forelimbs and hind limbs follows a similar general plan seen in the limbs
of amphibia, reptiles, birds and mammal. The bones of hand (fore limb) are humerus, radius and ulna.
Carpals (wrist bones – 8 in number). Metacarpals (palm bones – 5 in number) and phalanges (digits –
14 in number).
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Femur (thigh bone – longest bone), Tibia and Fibula, Tarsals (ankle bones – 7 in number), Metatarsals
– (5 in number), Phalanges (digits – 14 in number) are the bones of legs (hind limb). A cup shaped bone
called patella cover the knee ventrally (knee - cap). The limbs have five (penta) fingers or toes and
are pentadactyl limbs. There is some variation in the number of digits and terminal bones in different
vertebrates.
Clavicle
Ilium
Coxal bone
Sacrum
Pubis
Ischium
Femur
Scapula
Humerus
Patella
Radius
Ulna
Tibia
Fibula
Carpals
Metacarpals
Tarsals
Metatarsals
Phalanges
Phalanges
Pectoral girdle
Pelvic girdle
Joints
The places where two or more bones meet are termed joints. Joints are essential for all types of
movements involving the bony parts of the body. Force generated by the muscles is used to carry
out movement through joints, where the joint acts as fulcrum. The movability of these joints varies
depending on different factors. In vertebrates joints have been classified into 3 different structural forms.
They are fibrous, cartilaginous and synovial joints.
1.Fibrous joints: These joints allow no movement. For example: the flat skull bones which fuse end to
end with the help of dense fibrous connective tissue in the form of sutures to form the cranium.
2.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.
3.Synovial joints: These joints allow free movement in various directions. These joints are characterized
by the presence of fluid filled synovial cavity between the articular surfaces of the adjoining bones which
are covered with thin layer of cartilage. The synovial cavity is lined by thin synovial membrane.
A strong ligament, the capsular ligament, closely covers the exposed portions of the joint and serves
to strengthen the joint and prevents dislocation. The tearing or over stretching of these ligaments
results in a sprain. Dislocation occurs when the bones are forced out of place.
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These joints are of 4 types. They are Ball and socket joint, Hinge joint, Pivot joint and Gliding joint.
A. Ball and socket joint: The rounded head of one bone fits into a cup shaped cavity formed by the
other bone. This allows movement in all directions. E.g: joint between humerus and pectoral girdle.
B. Hinge joint: The hinge joints allow the movements like those of a door or the lid of a box.
E.g: Knee joint, elbow joint (joints between upper and lower arm).
C. Pivot joint: Such joints allow rotation only. It is because of this joint the head is able to turn from
side to side. Pivot joint occurs between first vertebra and axis vertebra.
D. Gliding joint: In these joints, the bones slide over each other. E.g: Tarsal bones in the ankle, carpal
bones in the wrist and between sternum and clavicle.
Synovial joints
Ball and socket
joint
Synovial membrane
Articular cartilage
Fibrous joint capsule
Joint cavity filled
with synovial fluid Ligaments
Cranium
Pivot joint
clavicle
pectoral girdle
sternum
humerus
elbow joint
vertebral column
wrist joint
carpal bones
Knee joint
Tarsal bones
Joints
Disorders of Muscular and SkeletalSystem 1. Arthritis
(GK – Arthro = joint; itis = inflammation) (Plural - arthritides) It is a form of joint disorder that involves
inflammation of one or more joints. There are 100 different forms of arthritis. The most common form –
osteoarthritis (degenerative joint disease) is a result of trauma to the joint, infection of the joint, or age.
Other arthritis forms are rheumatoid arthritis, psoriatic arthritis, septic arthritis etc.
The major complaint by individuals who have arthritis is joint pain. Pain is constant and may be localized
to the joint affected. The pain from arthritis is due to inflammation that occurs around the joint, damage
to the joint from disease, daily wear and tear of joint, muscle strains caused by forceful movements
against stiff, painful joints and fatigue.
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Arthritis
psoriatic arthritis
Rheumatoid arthritis
septic arthritis
2. Gout
It is caused by deposition of uric acid crystals in the
joint, causing inflammation. In early stages, gouty
arthritis occurs in one joint, but with time, it can occur
in many joints and be quite crippling. The joints in
gout can become swollen and lose function. Once it is
attacked it remains for hours. The main locations are
great toe, ankles, knees and elbows.
Gout
3. Myasthenia gravis
It is an autoimmune neuromuscular disease leading to
fluctuating muscle weakness and fatiguability.
Symptoms: The first noticeable symptom is the
weakness of eye muscles. In other cases difficulty in
swallowing and slurred speech may be the first signs.
4. Muscular dystrophy
Myasthenia gravis
It is a group of muscle diseases that weakens the
musculo skeletal system and hampers locomotion.
Muscular dystrophies are characterized by progressive
skeletal muscle cells and tissues. It is mostly due to
genetic disorder.
5. Tetany
Muscular dystrophy
It is involuntary contraction of muscles which may be
caused by disease or other conditions that increase
the action potential frequency.
The usual cause of tetany is lack of calcium. Tetany is
a symptom characterized by muscle cramps, spasms.
These repetitive actions of muscles happen when
muscle contracts uncontrollably. It may occur in any
muscle in body. The muscle cramping is long lasting
and painful.
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Tetany
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6. Osteoporosis
It is a disease of bone that leads to an increased
risk of fracture. The bone mineral density is reduced.
Osteoporosis itself has no symptoms. Bone mass
decreases after 35 years of ages and occurs more
rapidly in women after menopause.
Risk factors include lack of exercise, lack of Calcium,
deficiency of vitamin - D & family history etc.
Osteoporosis
Summary
•
Movement is an essential feature of all living beings. Locomotion involves the movement of whole
body.
•
Cells of the human body exhibit 3 types of movements – amoeboid, ciliary and muscular.
•
Muscles are a specialized tissue and have special properties like excitability, contractility, extensibility
and elasticity.
•
Based on their structure, location and function, muscles are of 3 types – striated, non-striated and
cardiac muscles.
•
Muscle fibre is unit of muscle. Each muscle fibre has parallely arranged myofibrils.
•
Each myofibril contains many serially arranged units called sarcomeres.
•
Each sarcoma has central ‘A’ band made of thick myosin filaments and 2 half I bands made of thin
actin filaments on either side of it marked by Z lines.
•
Actin and Myosin are proteins. The active sites for myosin on resting actin filament are masked by
protein called troponin.
•
Myosin head contains ATPase, ATP binding sites and active sites for Actin.
•
A motor neuron carries signal to the muscle fibre which generates action potential.
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