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Kerala Plus One Zoology Notes Chapter 9 Locomotion and Movement
What is locomotion?
The movements result in a change of place or location. Such voluntary movements are called locomotion. Walking, running, climbing, flying, swimming are all some forms of locomotory movements.
Locomotory Movements In Lower Organisms
- Paramoecium, cilia helps in the movement of food through cytopharynx and locomotion.
- Hydra use its tentacles for capturing its prey and also use them for locomotion.
All locomotions are movements but all movements are not locomotions.
Types Of Movement
The three main types of movements of cells of the human body are
1. Macrophages and leucocytes in blood exhibit amoeboid movement
2. pseudopodia formed by the streaming of protoplasm (as in Amoeba).
3. Cytoskeletal elements like microfiiaments exhibit amoeboid movement
1. Internal tubular organs which are lined by ciliated epithelium.
2. The coordinated movements of cilia in the trachea help us in removing dust particles and foreign Substances
3. Passage of ova through the female reproductive tract.is also facilitated by the ciliary movement.
1. Movement of our limbs, jaws, tongue, etc, require muscular movement.
2. The muscles are used for locomotion.
Locomotion requires a coordinated activity of muscular, skeletal and neural systems.
About 40-50 perent of the body weight of a human adult is contributed by muscles. Muscles are classified based on their location, three types of muscles are identified.
1. Skeletal muscles:
They have a striped appearance and called as striated muscles. They are voluntary muscles because their activities are under the voluntary control of the nervous system. They are involved in locomotory actions and changes of body postures.
2. Visceral muscles:
- They are located in the innerwalls alimentary canal, reproductive tract, etc. They are called smooth muscles (non striated muscle).
- Their activities are not underthe voluntary controlcalled as involuntary muscles.
- They helps in transportation of food through the digestive tract and gametes through the genital tract.
3. Cardiac muscles:
- They are found in the muscles of heart. Based on appearance, cardiac muscles are striated and involuntary.
- 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 contains a number of muscle fibres. Each muscle fibre is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm.
- Muscle fibre is a syncitium because it contains many nuclei.
- The endoplasmic reticulum, i.e., sarcoplasmic reticulum of the muscle fibres is the store house of calcium ions.
|The muscle fibre consists of parallelly arranged filaments in the sarcoplasm called myofilaments or myofibrils. Each myofibril has alternate dark and light bands on it. The striated appearance is due to two important proteins – Actin and Myosin. The light bands contain actin and is called l-band or Isotropic band, whereas the dark band called A’ or Anisotropic band contains myosin.
The A and T bands are arranged alternately. Actin filaments are thinner as compared to the myosin filaments.In the centre of each T 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 attached in the middle of this band by a thin fibrous membrane called ‘M’ line.
The myofibril between two successive ‘Z’ lines is the functional unit of contraction and is called a sarcomere In a resting state, the edges of thin filaments on either side of the thick filaments partially overlap the free ends of the thick filaments. The central part of thick filament, not overlapped by thin filaments is called the ‘H’ zone.
Structure of Contractile Proteins
Each actin filament is made of two ‘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 the ‘F’ actins throughout its length.
Acomplex 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.
Monomeric proteins called Meromyosins forms one thick filament. Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.
Mechanism of Muscle Contraction
The sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments.
Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron. The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate.
- In the junction, the neurotransmitter (Acetyl choline) is released which generates an action potential in the sarcolemma. This spreads and release of calcium ions into the sarcoplasm.
- Increase in Ca++ level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin.
- The energy from ATP hydrolysis is used to bind the myosin head with 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, i.e. contraction.
- During shortening of the muscle the T bands get reduced, whereas the ‘A’ bands retain the length The myosin, releasing the ADP and P1 goes back to its relaxed state.
- The ATP is again hydrolysed by the myosin head and the cycle of cross bridge formation and breakage is repeated causing further sliding.
- The process continues till the 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.
What is muscle fatigue?
Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen causing fatigue. Muscle contains a red coloured oxygen storing pigment called myoglobin. These muscles contain plenty of mitochondria which helps in ATP production.
Hence they are called aerobic muscles. Some of the muscles possess very less quantity of myoglobin and gives whitish appearance . These are the White fibres. Number of mitochondria are also few in them. They depend on anaerobic process for energy.
1. Skeletal system consists of a framework of bones and a few cartilages.
2. Bone and cartilage are specialised connective tissues.
3. The former has a very hard matrix due to calcium salts in it and the latter has slightly pliable matrix due to chondroitin salts. In human beings, this system is made up of 206 bones and a few cartilages. It is grouped into two divisions.
- It comprises 80 bones distributed along the main axis of the body.
- The skull, vertebral column, sternum and ribs constitute axial skeleton.
The skull is composed of two sets of bones – Cranial bones are 8 in number. The facial region is made up of 14 skeletal elements which form the front part of the skull.
Diagrammatic view of human skull:
A single U-shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull.
What is ear ossicles ?
Each middle ear contains three tiny bones – Malleus, Incus and Stapes, collectively called Ear Ossicles.
It is formed by 26 serially arranged units called vertebrae and is dorsally placed. Each vertebra has a central hollow portion (neural canal) through which the spinal cord passes. First vertebra is the atlas and it articulates with the occipital condyles. The vertebral column is differentiated into cervical (7), thoracic (12), lumbar (5), sacral (1-fused)and coccygeal (1-fused) regions starting from the skull.
Vertebral column (right lateral view) Ribs and rib cage. The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back.
It is a flat bone on the ventral midline of thorax.
There are 12 pairs of ribs.
1. First seven pairs of ribs are called true ribs. Dorsaily, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage.
2. 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 (false) ribs.
3. Last 2 pairs (11th and 12th) of ribs are not connected ventrally and are called floating ribs. Thoracic vertebrae, ribs and sternum together form the rib cage.
It includes bones of the limbs alongwith their girdles Each limb is made of 30 bones. The bones of the 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) Femur (thigh bone – the longest bone), tibia and fibula, tarsals (ankle bones – 7 in number), metatarsals (5 in number) and phalanges (digits -14 in number) are the bones of the legs (hind limb).
A cup shaped bone called patella cover the knee ventrally (knee cap). Pectoral and Pelvic girdle bones help in the articulation of the upper and the lower limbs respectively with the axial skeleton.
Each half of pectoral girdle consists of a clavicle and a scapula. Scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second and the seventh 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.
Below the acromion is a depression called the glenoid cavity which articulates with the head of the 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 consists of two coxal bones Each coxal bone is formed by the fusion of three bones
Joints are points of contact between bones, or between bones and cartilages. The movability of joints vary depending on different factors.
Joints are classified into three,
|1. Fibrous joints
This type of joint is found in the flat skull bones which fuse end-to-end with the help of dense fibrous connective tissues in the form of sutures, to form the cranium. They do not allow any movement.
2. Cartilaginous joints
The bones are joined together with the help of cartilages. It allows limited movements.
3. Synovial joints
It has fluid filled synovial cavity between the articulating surfaces of the two bones. These joints help in locomotion and many other movements.(box)
|Ball and socket joint (between humerus and pectoral girdle), Hinge joint (knee joint), Pivot joint (between atlas and axis), Gliding joint (between the carpals) and Saddle joint (between carpal and metacarpal of thumb) are some examples.|
Disorders Of Muscular And Skeletal System
Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.
Progressive degeneration of skeletal muscle mostly due to genetic disorder.
Rapid spasms (wild contractions) in muscle due to low Ca++ in body fluid.
Inflammation of joints.
Age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased levels of estrogen is a common cause.
Inflammation of joints due to accumulation of uric acid crystals.
NCERT SUPPLEMENTARY SYLLABUS
Types of movements: Flagellar movement
The three main types of movements shown by the cells of the human body are amoeboid, ciliary and muscular. Human sperms shows type of movement called the flagellar movement. The flagellum is the propulsion equipment (due to whip like movement of the tail and the middle piece of the sperm) forthe movement of sperm towards the ovum.