ZLGY-MM: XI 17.

LOCOMOTION & MOVEMENT

 Movement is the displacement of one or more parts of body. STRUCTURE OF SKELETAL MUSCLE
 Locomotion is the displacement of the entire body.  Skeletal muscle is made of muscle bundles (fascicles) held
Locomotion is generally for search of food, shelter, mate, together by collagenous connective tissue layer (fascia).
suitable breeding grounds, favourable climatic conditions or to  Each fascicle contains number of muscle fibres. Muscle fibres are
escape from enemies / predators. lined by plasma membrane (sarcolemma) enclosing the
Types of Movement sarcoplasm.
Movt. Mechanism Seen in- Cell Muscle fibre
Effected by pseudopodia formed due to Plasma Membrane Sarcolemma
Protoplasm Sarcoplasm
Amoeboid

streaming of protoplasm and microfilaments. Amoeba, Endoplasmic Reticulum Sarcoplasmic Reticulum

Macrophages,
Leucocytes.  Each muscle fibre contains parallely arranged myofilaments (myofibril).
Each myofibril has alternate dark (Anisotropic or A-band 
light rays are refracted in different directions) and light striations
Movement of cilia cause the movement of either
the cell or the surrounding fluid. (Isotropic or I-band same angle). This is due to the presence of
2 fibrous contractile proteins- thin Actin and thick Myosin.
Paramoecium, - I-bands contain actin only.
Ciliary

In trachea, - A-bands contain myosin & ends of actin.

in oviducts The ‘A’ and ‘I’ bands are arranged alternately throughout the
length of the myofibrils.
 A-band bears a lighter middle region (H-zone: hellerGer = brighter)
formed of only myosin. A thin fibrous membrane (M-line:
Sponges, MittelscheibeGer = middle) runs through the centre of H-zone.
Flagellar

Euglena,  I-band is bisected by an elastic fibre called Z-line (ZwischenGer =

Trypanosoma, between). The actin filaments are firmly attached to the ‘Z’ line.
In sperm
Region between two Z-lines is called sarcomere. They are the
functional units of a muscle contraction. Sarcomere = ½ I + A + ½ I
Tentacular

Hydra

By the help of muscles and skeleton

Movt. of
Muscular

limbs,
jaws,
eye-lid,
tongue etc.

HUMAN MUSCULAR SYSTEM

 There are over 600 muscles in the human body
 Origin: mesodermal.
Properties: Excitability, contractility, extensibility &elasticity. M-line
Definitions at last
Types of Muscles
Skeletal muscle Visceral muscle Cardiac
Criteria (Striated / voluntary (Non-striated/ Smooth /
muscle) involuntary muscle) muscle

In the wall of internal Present only

Location Attached to skeleton
organs (viscera) in the heart
Voluntary (activities
Nature of
are under the control of Involuntary Involuntary
regulatn
nervous system) Structure of Contractile Proteins
Appeara Cylindrical,
Spindle shaped, Striations are  Each actin filament is made of 3 proteins-
Striations absent present, Actin proteins
nce Striations present
(⸫ smooth in appearance) Branched
Locomotory actions and Responsible for movt. of Pumping
Functn 2 F-actins 2 filaments of 3 subunits of
changes of body postures internal organs. action of heart
Tropomyosin Troponin
2 filamentous
actins form Runs along the Seen at regular intervals
double helix. grooves of the on tropomyosin.
* F-actin is a F-actin double * In the resting state, a
polymer of helix subunit of troponin
Globular (G) masks the binding sites
actins. for myosin on the actin
filaments.

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 Each myosin filament is a polymer of protein Meromyosins. Muscle Fatigue
Parts of Meromyosin  Repeated activation of the muscles leads to the accumulation of
the lactic acid causing muscle fatigue. This is due to anaerobic
Heavy meromyosin (HMM) Light meromyosin (LMM) breakdown of glycogen in muscles.
Anaerobic respiration
/ Cross arm - tail Glycogen lactic acid
(globular head + short arm)
Types of Muscles fibres:-
Projects outwards at regular distance
 Muscle contains a red coloured O2 storing pigment called myoglobin.
Head is an active ATPase enzyme and has
Based on the amount of myoglobin present, muscles are 2 types-
binding sites for ATP and active sites for actin

Mechanism of muscle contraction

According to sliding filament theory, contraction of a muscle
fibre takes place by the sliding of actin over the myosin.
Neuro-muscular jn. / Motor neuron
Motor-end plate Motor unit
Muscle fibre Criteria Red (Aerobic) fibre White fibre
Sarcolemma
Myoglobin  Less (so white
Muscle Contraction:  High (gives a Red colour)
content in colour)
CNS
 High (can utilise the large
Signal via motor neuron Amount of
amount of O2 stored in  Low
release Acetyl choline at motor-end plate mitochondria
them for ATP production).
Generate an action potential in sarcolemma Amount of
Spread through muscle fibre sarcoplasmic  Low  High
Sarcoplasmic reticulum release Ca2+ into Sarcoplasm reticulum / Ca2+
Metabolism  Aerobic  Anaerobic
Ca2+ binds with troponin  cause shifting of tropomyosin
Found in
 Back, neck, leg etc.  Eyeball, calf
Actin exposes its myosin binding sites (active sites) muscles of
ATP hydrolysed by myosin head
Myosin head bind to actin  form a cross bridge HUMAN SKELETAL SYSTEM
 Human skeletal system consists of a framework of 206 bones
Myosin pull (slide) actin filaments towards centre of A-band and a few cartilages.
(i.e., Inward pulling of Z-line) - Bone has a hard matrix due to calcium salts in it
Repeat

Shortening of sarcomere (contraction) - Cartilage has slightly pliable matrix due to chondroitin salts.
 The skeletal system is divisible into axial and appendicular.
Myosin release the ADP + Pi and new ATP binds

Cross-bridge between actin and myosin breaks

ATP hydrolysed by myosin head
Cross bridge formation
Muscle Relaxation:
Signal from CNS stops
Ca2+ is returned to
sarcoplasmic cisternae
Tropomysin mask the active sites on actin filaments

‘Z’ lines return back to their original position (relaxation)

On muscle contraction:
Z-line come closer (Sarcomere shortens)
H-zone decrease & disappear
A-band remains same
I-band shortens

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204
 Facial
Maxilla (2) – Upper jaw
Zygomatic (2)- prominence of cheek
Mandible- Lower jaw
Cranial bones: Form cranium protective Cranial Nasal (2)- bridges of nose
Cranial (8) Platine (2)- hard palate
covering for the brain Lacrimal (2)- orbit
Frontal, Parietal (2), Temporal (2),
Facial (14) Form the front part of the skull Occipital, Ethmoid, Sphenoid
Inferior nasal concha (2)- nasal cavity
Vomer (triangular)
U-shaped bone present at the base of the
Hyoid bone
buccal cavity
Skull-29 Malleus Each middle ear contains 3 tiny bones

Ear ossicles (3 x 2)
Incus

Stapes

Vertebrae- unit of vertebral column.

Cervical (7) Each vertebra has a central hollow portion
80 bones distributed along the axis of the body

(neural canal) through which the spinal

cord passes.
Thoracic (12)
Vertebrae

Vertebral
Axial skeleton

column- 26 Lumbar (5)

First vertebra (atlas) articulates with the
Sacral occipital condyles of skull
Functions of VC
(5 in embryonic
- Protects the spinal cord
stage fused to 1)
- Supports the head
Coccygeal - Serves as the point of attachment for
(4 1) the ribs and musculature of the back.
Sternum-1 -- A flat bone on the ventral midline of thorax
Dorsally ribs are attached to the thoracic
vertebrae at 2 points (bicephalic) &
ventrally connected to the sternum with the
True ribs / help of hyaline cartilage.
Vertebrosternal ribs
(1-7 pairs)

Ribs- 12 x 2
thin flat bone

False ribs /
Ribs join the 7th rib with the help of hyaline
Vertebrochondral
cartilage
ribs (8-10 pairs)
Floating ribs /
Vertebral ribs Ribs are not connected ventrally
(11- 12 pairs)
Humerus
126 bones of the limbs along with their girdles (connecting limbs to

Radius (towards
thumb)
Ulna
Hand- 30 x 2
Carpals (8) /
/ Fore limb --
Wrist bones
Metacarpals (5) /
Appendicular skeleton

Palm bones
Phalanges (14) /
the axial skeleton)

Digits
Femur /Thigh bone The longest bone
Patella / Knee cap A cup shaped bone cover the knee ventrally
Tibia
Leg- 30 x 2 / Fibula
Hind limb Tarsals (7) /
Ankle bones --
Metatarsals (5)
Phalanges (14) /
digits

Pectoral Clavicle / A long slender bone with two curvatures

girdle- 2 x 2 Collar bone attached to sternum & scapula

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205
 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.
Scapula The clavicle articulates (attach) with this.
Below the acromion is a depression called the 2nd rib
glenoid cavity which articulates with the
head of the humerus to form the shoulder
joint.
7th rib

Ilium At the point of fusion of the bones is a cavity

Coxal bone

called acetabulum to which the femur

Pelvic articulates.
Ischium
girdle- 1 x 2 The two halves of the pelvic girdle meet
ventrally to form the pubic symphysis
Pubis containing fibrous cartilage.

JOINTS MUSCULAR AND SKELETAL DISORDERS

 Joints are points of contact between bones, or between bones
and cartilages- 3 types:- Disorder Cause Symptoms
Auto immune disorder
Joints Features
affecting neuromuscular
 Bones which fuse end-to-end with the help Myasthenia junction
Fatigue, weakening and
paralysis of skeletal
of dense fibrous connective tissues gravis (antibodies formed here
a. Fibrous muscle
 Do not allow any movement. attack acetylcholine
Ex: In the flat skull bones receptor)
 The bones involved are joined together with Muscular Genetic disorder Progressive degeneration
dystrophy (dystrophin gene damaged) of skeletal muscle
the help of cartilages.
 It permits limited movements. Tetany Low Ca2+ in body fluid
Rapid spasms (wild
b. Cartilaginous contractions) in muscle
Ex: The joint between the adjacent
vertebrae in the vertebral column, joint b/w Arthritis -- Inflammation of joints
ribs & sternum.
Decreased bone mass and
 A fluid filled synovial cavity is present Osteoporosis
Decreased level of estrogen
increased chances of
between the articulating surfaces of the two due to aging.
fractures
bones.
Accumulation of uric acid
 Allows considerable movement. Gout
crystals in joints
Inflammation of joints
Types:
c. Synovial i. Ball and socket joint (e.g.: between
humerus and pectoral girdle)
ii. Hinge joint (e.g.: knee joint)
iii. Pivot joint (e.g.: between atlas and axis)
iv. Gliding joint (e.g.: between the carpals)
v. Saddle joint (e.g.: between carpal and
metacarpal of thumb)

Properties of muscle tissue:

 Excitability- The ability to respond to stimuli, such as hormones or motor neurons.
 Contractility- The ability to shorten or contract forcefully.
 Extensibility- The ability to stretch or be extended.
 Elasticity- The ability to return to its original length when relaxed.

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