Locomotion is the voluntary movements resulting in a elements like microfilaments also help for this. E.g.

change
in location. All locomotion are movements but all Macrophages & leucocytes.
movements are not locomotion. Both are interlinked. E.g. • Ciliary movement: By cilia. E.g. ciliary movements in
• In Paramoecium, cilia help in the movement of food trachea (to remove dust particles and foreign substances),
through cytopharynx and in locomotion. and oviducts (for the passage of ova).
• Hydra use tentacles to capture prey and for locomotion. • Muscular movement: By muscles. E.g. movement of limbs.
• Limbs help to change body postures and for locomotion. Flagellar movement helps in the swimming of spermatozoa,
Types of movement in human being maintenance of water current in the canal system of sponges
• Amoeboid movement: By pseudopodia formed by and in locomotion of Protozoans like Euglena.
streaming of protoplasm as in Amoeba. Cytoskeletal

HUMAN MUSCULAR SYSTEM

- It includes muscles which are mesodermal in origin.
- Muscles constitute 40-50% of the body weight.
- Muscles have excitability, contractility, extensibility &
elasticity.
- Based on location, muscles are 3 types:
Skeletal (striated)
muscles
Attached to skeleton
Visceral (Non-
striated) muscles
In visceral organs
Cardiac
muscles
In heart wall
E T
Striations present
Voluntary
Rich blood supply
Absent
Involuntary
Poor blood supply
Present
Involuntary
Rich blood supply
N E
e
Fatigue muscle Non-fatigue Non-fatigue
Multinucleate Uninucleate Uninucleate
More mitochondria Less mitochondria
STRUCTURE OF STRIATED MUSCLE
More mitochondria

n c
i e
- Skeletal muscle is made of muscle bundles (fascicles) held

sc
together by collagenous connective tissue layer (fascia).
Structure of contractile proteins

n O - An actin filament is made of 2 filamentous (F) actins

which form double helix.

ra i - F-actin is a polymer of monomeric Globular (G) actins.

B - Actin contains 2 other proteins (tropomyosin & troponin).

- Two filaments of tropomyosin run along the grooves of
the F-actin double helix.
- Each fascicle contains many muscle fibres (muscle cells).
- Muscle fibres are lined by plasma membrane - Troponin has 3 subunits. It is seen at regular intervals on
(sarcolemma) enclosing the sarcoplasm. tropomyosin. In the resting state, a subunit of troponin
- Each muscle fibre contains myofilaments (myofibrils). masks the binding sites for myosin on the actin filaments.
- Each myofibril has alternate dark (Anisotropic or A- - Each myosin filament is a polymer of many monomeric
proteins called Meromyosins.
band) and light striations (Isotropic or I-band). This is
due to the presence of 2 fibrous contractile proteins- thin
Actin filament and thick Myosin filament.
- I-bands contain actin. A-bands contain actin and myosin.
They are arranged parallel to each other.
- A-band bears a lighter middle region (H band) formed of - A meromyosin has 2 parts:
only myosin. A thin dark line (M-line) runs through the o Heavy meromyosin or HMM or cross arm (globular
centre of H-zone. head + short arm): It projects outwards.
- I-band is bisected by a dense dark band called Z-line. o Light meromyosin or LMM (tail).
Region between two Z-lines is called sarcomere. They are - The globular head is an active ATPase enzyme and has
the functional units of muscle contraction. binding sites for ATP and active sites for actin.

1
 MECHANISM OF MUSCLE CONTRACTION § The Z- line attached to actins is also pulled inwards. It
causes a shortening (contraction) of sarcomere.
According to sliding filament theory, contraction of a muscle
§ I-bands get shortened, whereas A-bands retain the length.
fibre occurs by the sliding of thin filaments over thick filaments.
§ Myosin releases ADP and Pi and goes back to its relaxed
The steps are given below:
state. A new ATP binds and the cross-bridge is broken.
§ An impulse from the CNS reaches the neuromuscular
§ The ATP is again hydrolyzed by the myosin head and the
junction (Motor-end plate) via motor neuron.
above processes are repeated causing further sliding.
Neuromuscular junction is the synapse between a motor
§ When Ca2+ ions are pumped back to sarcoplasmic cisternae,
neuron and the sarcolemma of the muscle fibre.
actin filaments are again masked. As a result, Z-lines return
A motor neuron + muscle fibres = a motor unit.
to their original position. It results in relaxation.
§ Synaptic vesicles release a neurotransmitter Acetylcholine.
It generates an action potential in the sarcolemma that
spreads through the muscle fibre. It causes the release of
Ca2+ ions from sarcoplasmic cisternae into sarcoplasm.
§ Ca binds with a subunit of troponin on actin filaments and
unmask the active sites for myosin.

E T
- The reaction time of the fibres varies in different muscles.
- Repeated activation of muscles leads to the accumulation

E
of the lactic acid causing muscle fatigue. This is due to
anaerobic breakdown of glycogen in muscles.

N
Red muscle fibres and white muscle fibres

ce
Red (Aerobic) muscles White muscle
Red coloured due to White coloured due to lesser
§ Using energy from ATP hydrolysis, myosin head binds to
active sites on the actin to form cross bridge. This pulls

e n myoglobin
More mitochondria
myoglobin
Less mitochondria

ci
actin filaments on both sides towards the centre of A-band. Aerobic metabolism Anaerobic metabolism
Actin filaments partially overlap so that H-zone disappears. Slow & sustained contraction Fast contraction for short period

s
HUMAN SKELETAL SYSTEM

n O
It consists of a framework of bones (206) & few cartilages.
Human skeletal system has 2 parts: axial & appendicular.
Skull articulates with First vertebra (atlas) with the help
of 2 occipital condyles (dicondylic skull).

ra i
1. Axial skeletal system (80 bones)
Includes bones of head, vertebral column, sternum & ribs.
o Hyoid bone (1): U-shaped bone seen below buccal cavity.
o Ear ossicles (3 x 2 = 6): Malleus (2), Incus (2) & stapes (2).

B
a. Bones of Head (29 bones)
It includes skull, Hyoid and Ear ossicles.
-
b. Vertebral column
Formed of 26 vertebrae. Includes Cervical vertebrae (7),
Thoracic vertebrae (12), Lumbar vertebrae (5), Sacral
vertebrae (1-fused) and Coccygeal vertebrae (1-fused).
- Vertebra has a central
hollow portion (neural
canal) through which the
spinal cord passes.
- Number of cervical
vertebrae are 7 in almost
all mammals.
- The vertebral column
protects the spinal cord,
supports the head and
o Skull (22): Include cranial bones and facial bones. serves as the point of
Cranial bones (8): Include Frontal (1), Parietals (2), attachment for the ribs and
Temporals (2), Occipital (1), Sphenoid (1) & Ethmoid (1). musculature of the back.
Facial bones (14): Include Nasals (2), Maxillae (2), c. Sternum or Breast bone (1)
Zygomatics (2), Lacrimals (2), Palatines (2), Inferior - Flat bone on the ventral midline of thorax.
nasals (2), Mandible (1) and Vomer (1).
2
 d. Ribs (12 pairs) b. Bones of hind-limbs (30 x 2 = 60)
Include Femur (thigh bone- 1), Patella (knee cap- 1), Tibia
(1) & fibula (1), Tarsals (ankle bones-7), Metatarsals (5) &
Phalanges (digits-14).
c. Pectoral girdles (2x2=4)
- Include clavicle (2) & scapula (2).
- Scapula is a large triangular flat bone situated in the dorsal
part of the thorax between the second and 7th ribs.
- Scapula (shoulder blade) has a slightly elevated ridge
(spine) which projects as a flat, expanded process
(acromion). The clavicle (collarbone) articulates with this.
o True ribs (first 7 pairs): They are attached to thoracic - Below the acromion is glenoid cavity which articulates
vertebrae and ventrally connected to sternum with the help with the head of humerus to form the shoulder joint.
of Hyaline cartilage. d. Pelvic girdles (2)
o Vertebrochondral (false) ribs (8th, 9th & 10th pairs): They - Formed of 2 coxal bones. Each coxal bone is formed by the
do not articulate directly with the sternum but join the 7th fusion of 3 bones- Ilium, Ischium & pubis.
rib with the help of Hyaline cartilage. - At the point of fusion of Ilium, Ischium and Pubis is a
o Floating ribs (11th & 12th pairs): They are not connected cavity (Acetabulum) to which the thigh bone articulates.
ventrally (no connection with sternum or other ribs). - The 2 halves of the pelvic girdle meet ventrally to form
- Each rib has 2 articulation surfaces on its dorsal end and is
hence called bicephalic.
2. Appendicular skeletal system (126 bones)
JOINTS
E T
pubic symphisis containing fibrous cartilage.

N
and cartilages. 3 types:
E
Joints are points of contact between bones, or between bones

1. Fibrous (immovable) joints: E.g. sutures b/w skull bones.

c e
2. Cartilaginous joints (Slightly movable joints): Bones
are joined together with the help of cartilages. E.g. Joints

i e n
between the adjacent vertebrae.
3. Synovial (movable) joints: They have a fluid filled

sc
synovial cavity between articulating surfaces of 2 bones.
Types of synovial joint

O
Joint Examples
Ball & socket Shoulder joint & hip joints.

i n Hinge joint Knee joint, elbow joint, phalanges joints

ra
Pivot joint Joints b/w atlas & axis.
Gliding joint Joints b/w carpals

B
a. Bones of fore-limbs (30 x 2 = 60) Saddle joint Joints b/w carpal & metacarpal of thumb
Include Humerus (1), Radius (1), Ulna (1), Carpals (wrist bones-
8), Metacarpals (palm bones-5) & Phalanges (digits-14).

DISORDERS OF MUSCULAR & SKELETAL SYSTEMS

• Myasthenia gravis: An auto immune disorder that affects • Arthritis: Inflammation of joints.
neuromuscular junction. It leads to fatigue, weakening and • Osteoporosis: Age-related disorder characterized by
paralysis of skeletal muscles. decreased bone mass and increased chances of fractures.
• Muscular dystrophy: Progressive degeneration of Decreased level of estrogen is a common cause.
skeletal muscles. Mostly due to genetic disorder. • Gout: Inflammation of joints due to accumulation of uric
• Tetany: Rapid muscle spasm due to low Ca2+ in body fluid. acid crystals.

3
 MODEL QUESTIONS
1. When a muscle cell is viewed under a microscope, it has the following characters
Striations present, Multi nucleate, Sarcolemma present
a) Identify the tissue b) Mention the function of the tissue
2. Observe the relaxed unit of a muscle given below.
a) Label A, B & C.
b) Redraw the diagram when the muscle unit is maximally
contracted.
c) Repeated activation of the muscle can lead to fatigue. Justify.
3. Arrange the following flow chart in the correct sequence of events:
Generation of action potential in the sarcolemma → Release of Ca2+ ions from sarcoplasmic cisternae into
sarcoplasm → Active sites of actin are exposed → Impulse from the CNS → Neuromuscular junction → Shortening
(contraction) of sarcomere → Synaptic vesicles release Acetylcholine → Actin filaments are pulled towards H-zone
→ Ca binds with troponin on actin filaments → Myosin head binds to active sites to form cross bridge → H-zone
disappears.
4. Suppose a person is suffering from calcium deficiency for a prolonged time. How does it affect muscular contraction?
5. Diagram of a joint is given below:

a)
b)
Identify the joint.
Name three major structural forms of joints.

E T
6. Complete the following chart
N E
c e
Axial skeletal system

Bones of head

i e n A Sternum B

Cranial
bones C Facial
bones
sc
Hyoid
bone
Cervical
vertebra
Thoracic
vertebra D Saccrum &
Coccyx

7. Match the following

n O
ra i Type of joints
i. Ball and socket
ii. Pivot joint
a)
b)
Examples
Joints of skull bone
Between carpals and metacarpals of the thumb

B iii. Saddle joint

iv. Gliding joint
c)
d)
e)
Between humerus and pectoral girdle
Between atlas and axis
Between the carpals