NCERT Solutions Class 11th Biology Chapter – 20 Locomotion and Movement
| Textbook | NCERT |
| class | Class – 11th |
| Subject | Biology |
| Chapter | Chapter – 20 |
| Chapter Name | Locomotion and Movement |
| Category | Class 11th Biology Notes |
| Medium | English |
| Source | last doubt |
NCERT Solutions Class 11th Biology Chapter – 20 Locomotion and Movement
?Chapter – 17?
✍Locomotion and Movement✍
?Notes?
Movement is an essential feature of all living beings.
Protoplasmic streaming, ciliary movements, movements of fin, limbs, wings, etc., are some forms exhibited by animals,
A voluntary movement that causes the animal to change its place is called locomotion.
Animals move generally in search of food, shelter, mate, breeding ground, a better climate or to protect themselves.
The cell of the human body exhibit amoeboid, ciliary, and muscular movements.
Locomotion and many other movements require coordinated muscular activities.
Three types of muscles are present in our body.
Skeletal muscles are attached to skeletal elements. They appear united and are voluntary in nature.
Visceral muscles, present in the inner walls of visceral organs are nonstriated and involuntary.
Cardiac muscles are the muscles of the heart. They are striated, branched, and involuntary.
Muscles possess excitability, contractility, extensibility, and elasticity.
A muscle fiber is the anatomical unit of muscle. Each muscle fiber has many parallelly arranged myofibrils. Each myofibril .contain many serially arranged units called sarcomere which is the functional unit.
Each sarcomere has a central A-bond made of thick myosin filaments, and two half I-bands made of thin actin filaments on either side of it marked by Z lines.
Actin and myosin are polymerized proteins with contractility, the active sites for myosin on resting actin filament are masked by a protein- troponin.
Myosin head contains ATP phase and has ATP binding sites and active sites for actin.
A motor neuron carries the signal to the muscle fiber which generates action potential in it. This causes the release of Ca++ from the sarcoplasmic reticulum.
Ca++ activates actin which binds to the myosin head to form a cross bridge. These cross bridges pull the actin filaments causing them to slide over the myosin filaments and thereby causing contraction.
Ca are then returned to the sarcoplasmic reticulum which inactivates the actin. Cross bridges are broken and the muscles relax.
Repeated stimulation of muscle leads to fatigue. Muscles are classified as Red and White fibers based primarily on the amount of red-colored myoglobin pigment in them.
Bones and cartilages constitute our skeletal system. The skeletal system is divisible into axial and appendicular.
Skull, vertebral column, ribs, and sternum constitute the axial skeleton. Limb bones and girdles form the appendicular skeleton.
Three types of joints are formed between bones or between bone and cartilage:
- Fibrous,
- cartilaginous, and
- synovial.
Synovial joints allow considerable movements and therefore, play a significant role in locomotion.
Locomotion – Such voluntary movements i.e., limbs, jaws, eyelids, tongue, etc. are called locomotion.
Striated muscles – Skeletal muscles have a striped appearance under the microscope and hence are called striated muscles.
Voluntary muscles – As striated muscle activities are under the voluntary control of the nervous system, they are known as voluntary muscles too.
Smooth muscles (nonstriated muscle) – Visceral muscles do not exhibit any striation and are smooth in appearance. Hence, they are called smooth muscles (non-striated muscles).
Involuntary muscles – Smooth muscle activities are not under the voluntary control of the nervous system and are therefore known as in-voluntary muscles.
Fascia – Each organized 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.
Myofilaments or myofibrils – A characteristic feature of the muscle fiber is the presence of a large number of parallelly arranged filaments in the sarcoplasm called myofilaments or myofibrils.
‘I’ band and ‘A’ band – The light bands contain actin and are called T band or Isotropic band whereas the dark band called ‘A’ or Anisotropic band contain myosin.
Thin and thick filaments – Actin filaments are thinner as compared to the myosin filaments, hence are commonly called thin and thick filaments respectively.
‘M’ Line – The thick filaments in the ‘A’ band are also held together in the middle of this band by a thin fibrous membrane called the ‘M’ line.
Sarcomere – The portion of the myofibril between two successive ‘Z’ lines is considered as the functional unit of contraction and is called a sarcomere.
‘H’ Zone – Central part of thick filament, not overlapped by thin filaments is called the ‘H’ zone.
Meromyosins – Each myosin (thick) filament is also a polymerized protein. Many monomeric proteins called meromyosins constitute one thick filament.
Myoglobin – Muscle contains a red-colored oxygen storing pigment called myoglobin.
Red muscles – Myoglobin content is high in some of the muscles which give a reddish appearance. Such muscles are called the Red muscles.
Aerobic muscles – Red muscles also contain plenty of mitochondria that can utilize a large amount of oxygen stored in them for ATP production. These muscles, therefore, can also be called aerobic muscles.
Hyoid – A single ‘U’ shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull.
Spine and Acromion – The posterior, flat, triangular body of the scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion.
Glenoid Cavity – Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint.
Collar bone – Each clavicle is a long slender bone with two curvatures. This bone is commonly called the collar bone.