CH-17 Locomotion & movement
Locomotion: the movement which results in change of place or location
TYPES OF LOCOMOTION
Cells of human body exhibits mainly 3 types of movements
I) ameboid 2) ciliary 3) muscular
Macrophages & luecocytes, microfilaments
Internal tubular organs ( lined by ciliated epithelium)
Eg. Passage of ova through female reproductive tract
Movement of our limbs, jaws etc
The contractile property of muscle are effectively used for locomotion &
other movements
MUSCLE
I) mesodermal origin
2) abt. 40 - 50% of the body weight
3) properties - excitability, contractility, extensibility & elasticity
4) 3 types: a) skeletal b) visceral c) cardiac
SKELETAL
1) closely associated w/ skeletal components of the body
2) striped appearance under the microscope & are known as striated muscles
3) known as voluntary muscles too
4) involved in locomotory actions & changes in body posture
ii VISCERAL
I) located in the inner walls of hollow visceral organs of the body
2) smooth in appearance hence called smooth (non striated muscles)
3) aka involuntary muscles
4) assist in transportation of food through digestive tract & gametes through
genital tract
iii CARDIAC
1) muscles of heart
2) they are striated
3) involuntary
I) each organised skeletal muscle is made of a no. of muscle bundles or fascicles
held together by a common collagenous tissue layer called fascia
2) each muscle bundle contains a no. of muscle fibres
3) each muscle fibre is lined by the plasma membrane called sarcolemma
enclosing the sarcoplasm
4) the endoplasmic reticulum (sarcoplasmic reticulum) is the store house of
calcium ions
5) a large no. of parallely arranged filaments in the sarcoplasm called myofilaments
or myofibrils. each myofibril has alternate dark and light bands on it
6) striated appearance is due to distribution pattern of 2 proteins
i) actin ii) myosin
light bands contain actin & is dark bands contain myosin & is
called i-band or isotropic band called A or anisotropic band
thin filaments *thick filaments
1) in the centre of an each `i’ band is an elastic fibre called z line which bisects
it
2) the `a’ band are also held together in the middle of this band by a thin
fibrous membrane called m line
3) the portion of the myofibril b/w two successive z line is considered as
the functional unit of contraction & is called sarcomere
4) the central part of the thick filament, not overlapped by thin filaments is called
the h zone
STRUCTURE OF CONTRACTILE PROTEIN
ACTIN
1) each actin is made up of 2 f (filamentous) actins helically wound to each other
2) each f actin is a polymer of monomeric G (globular) actins
3) two filaments of another protein, tropomysin also run close to f actin
throughout its length
4) a complex protein troponin is distributed at regular intervals on tropomysin
5) in the resting state a subunit masks the active binding sites for myosin on
actin filaments
MYOSIN
1) many monomeric proteins called meromyosins constitute 1 myosin
2) each meromyosin has 2 imp parts
i) a globular head with short arm ii) tail
heavy meromyosin (HMM) light meromyosin (LMM)
3) the HMM projects outwards at regular dist & angle from each other from the
surface of polymerised myosin & is k/a cross arm
4) the globular head is an active ATPase enzyme & has binding sites for ATP and
active sites for actin
MECHANISM OF MUSCLE CONTRACTION
1) a motor neuron alongwith the muscle fibres connected to it constitute a motor
unit
2) the junction b/w a motor neuron and sarcolemma of the muscle fibre is called
the neuromuscular junction or motor-end plate
3) neural signal → neurotransmitter (acetyl choline) → action potential →
release of Ca(++) ions
this leads to binding of Ca with troponin and thereby remove the masking site
of active site for myosin
4) this pulls the attached filaments towards the centre of A band
5) the z line attached to these actins are pulled inwards thereby causing a
shortening of the sarcomere
6) I bands get reduced whereas A band retain length
7) repeated activation of muscles can lead to the accumulation of lactic acid due to
anaerobic breakdown of glycogen causing fatigue
8) muscle contains a red coloured oxygen storing pigment called myoglobin. it
gives a reddish appearance and such muscles are called red fibres
they also contain plenty of mitochondria which can utilise a large amount of
oxygen stored in them for ATP production
9) some of the muscles possess very less quantity of myoglobin and therefore
appear pale or whitish. these are called white fibres
SKELETAL SYSTEM
1) 206 bones
two divisions
axial skeleton appendicular skeleton
i) AXIAL SKELETON
1) 80 bones ( skull, vertebral column, sternum, ribs)
a) skull
1) two sets of bones- cranial (8) & facial (14). total= 22 bones
hard protective outer covering, forms the front part of the
cranium for the brain skull
2) a single U-shaped bone called hyoid is present at the base of the buccal cavity
3) each middle ear contains 3 tiny bones- malleus, incus & stapes (EAR OSSICLES )
b) vertebral column
1) formed by 26 serially vertebrae
2) 1st vertebra - atlas
cervical (7), thoracic (12), lumbar (5),
sacral (1-fused), coccygeal (1-fused)
3) func.- the vertebral column protects the spinal
cord, supports the head & serves as the point of
attachment for the ribs and musculature of the
back
c) sternum- flat bone on the ventral midline of thorax
d) ribs
1) 12 pairs
2) has 2 articulation surfaces on its dorsal end & is
hence called bicephalic
3) first 7 pairs - true ribs
dorsally- thoracic vertebrae
ventrally- sternum w/ hyaline cartilage
4) 8th, 9th & 10th pair- vertebrochondral (false)
ribs
5) 11th & 12th pair - floating ribs
APPENDICULAR SKELETON
1) each Limb is made up of 30 bones
hands (fore limbs)
1) humerus, radius, ulna, carpals (wrist bones- 8),
metacarpals (palm bones- 5),phalanges (14)
2) scapula is a large triangular bone situated in the
dorsal part of the thorax b/w 2nd & 7th ribs
3) scapula has a slightly elevated ridge called the
spine which projects as a flat, expanded process
called acromion
4) below the acromion, is the depression called glenoid
cavity which articulates with the head of the humerus
to form shoulder joint
5) each clavicle is a long slender bone with 2 curvatures
& is called collar bone
legs (hind limb)
1) femur (thigh bone- longest bone), tibia & fibula , tarsals (anklebones-7)
metatarsals (5), phalanges (14)
2) a cup shaped bone called patella cover the knee ventrally (knee cap)
3) consist of 2 coxal bones.
each coxal bone is formed by 3 bones - ilium, ischium & pubis
4) at the point of fusion of the above bones is a cavity called acetabulum
JOINTS
3 types
i) fibrous joints
do not allow any movement
shown by flat skull bones
ii) cartilaginous joints
joined together with the help of cartilages
eg. joint b/w adjacent vertebrae
iii) synovial joints
help in locomotion
ball & socket (b/w humerus & pectoral girdle), hinge joint (knee joint),
pivot joint (b/w atlas & axis), gliding joint (b/w the carpals), saddle joint (b/w
carpal & metacarpal of thumb)
DISORDERS OF MUSCULAR & SKELETAL SYSTEM
MYASTHENIA GRAVIS - auto immune disorder affecting neuromuscular
junction leading to fatigue, weakening & paralysis of skeletal muscle
MUSCULAR DYSTROPHY - progressive degeneration of skeletal muscle
due to genetic disorder
TETANY - rapid spasms in muscle due to low Ca(++) in body fluid
ARTHRITIS - inflammation of joints
OSTEOPOROSIS - age related disorder characterised by decreased bone mass
& increased chances of fractures
GOUT - inflammation of joints due to accumulation of uric acid crystals
