Human physio

• Purposes of locomotion

  • Search of food
  • Shelter
  • Mate
  • Suitable breeding grounds
  • Favourable climatic conditions
  • Escape from enemies/predators
• In Paramoecium

  Cilia help in the movement of food through cytopharynx and in locomotion
• Muscles have special properties like excitability, contractility, extensibility, and elasticity
• Muscular movement is required for movements of limbs, jaws, tongue, etc.
• Movements and locomotion are linked; all locomotions are movements but all movements are not locomotions
• Ciliary movement occurs in most internal tubular organs lined by ciliated epithelium
• Voluntary movements

  Result in a change of place or location and are called locomotion
• Hydra


  Uses tentacles for capturing prey and locomotion
• Locomotion requires a coordinated activity of muscular, skeletal, and neural systems
• Three types of muscles based on location are skeletal, visceral, and cardiac
• Movement

  One of the significant features of living beings. Animals and plants exhibit a wide range of movements
• Muscle is a specialised tissue of mesodermal origin contributing about 40-50% of the body weight of a human adult
• Visceral muscles are smooth in appearance, located in the inner walls of hollow visceral organs, and not under voluntary control
• Cells of the human body exhibit three main types of movements: amoeboid, ciliary, and muscular
• Forms of movement

  • Streaming of protoplasm in unicellular organisms like Amoeba
  • Movement of cilia, flagella, and tentacles in many organisms
  • Human movements like moving limbs, jaws, eyelids, tongue, etc.
• Flagellar movement helps in the swimming of spermatozoa, maintenance of water current in the canal system of sponges, and in locomotion of Protozoans like Euglena
• Skeletal muscles are striated, under voluntary control, and primarily involved in locomotory actions and changes of body postures
• Humans


  Use limbs for changes in body postures and locomotion
• Macrophages and leucocytes in blood exhibit amoeboid movement
• Each actin (thin) 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. A complex 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.
• Smooth muscles are located in the inner walls of hollow visceral organs of the body like the alimentary canal, reproductive tract, etc. They do not exhibit any striation and are smooth in appearance. Hence, they are called smooth muscles (nonstriated muscle). Their activities are not under the voluntary control of the nervous system and are therefore known as involuntary muscles. They assist, for example, in the transportation of food through the digestive tract and gametes through the genital tract.
• Let us examine a skeletal muscle in detail to understand the structure and mechanism of contraction. Each organised 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. 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 as the sarcoplasm contains many nuclei. The endoplasmic reticulum, i.e., sarcoplasmic reticulum of the muscle fibres is the storehouse of calcium ions. A characteristic feature of the muscle fibre is the presence of a large number of parallelly arranged filaments in the sarcoplasm called myofilaments or myofibrils. Each myofibril has alternate dark and light bands on it. A detailed study of the myofibril has established that the striated appearance is due to the distribution pattern of two important proteins – Actin and Myosin. The light bands contain actin and are called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains
• Muscle fibre is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm. Muscle fibre is a syncitium as the sarcoplasm contains many nuclei. The endoplasmic reticulum, i.e., sarcoplasmic reticulum of the muscle fibres is the storehouse of calcium ions. A characteristic feature of the muscle fibre is the presence of a large number of parallelly arranged filaments in the sarcoplasm called myofilaments or myofibrils. Each myofibril has alternate dark and light bands on it. A detailed study of the myofibril has established that the striated appearance is due to the distribution pattern of two important proteins – Actin and Myosin. The light bands contain actin and are called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains
• Each myosin (thick) filament is also a polymerised protein. Many monomeric proteins called Meromyosins constitute 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 HMM component, i.e.; the head a
• Cardiac muscles are the muscles of the heart. Many cardiac muscle cells assemble in a branching pattern to form a cardiac muscle. Based on appearance, cardiac muscles are striated. They are involuntary in nature as the nervous system does not control their activities directly.
• Meromyosin

  The globular head is an active ATPase enzyme with binding sites for ATP and active sites for actin
• Role of calcium ions in muscle contraction

  Ca++ binds with troponin on actin filaments, exposing active sites for myosin to form cross bridges
• Meromyosins


  • Constitute one thick filament, each with a globular head with a short arm and a tail (heavy meromyosin and light meromyosin)
• Muscles contain myoglobin, a red-coloured oxygen-storing pigment
• Muscle contraction initiation

  Signal sent by the central nervous system via a motor neuron, leading to the release of calcium ions into the sarcoplasm
• Repeated activation of muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen, causing fatigue
• Mechanism of Muscle Contraction

  Contraction occurs by the sliding of thin filaments over thick filaments
• Skeletal system consists of a framework of bones and a few cartilages, playing a significant role in body movement
• Cross bridge formation

  Myosin head binds to exposed active sites on actin, pulling actin filaments towards the centre of 'A' band, causing sarcomere shortening
• Red fibres have high myoglobin content, appear reddish, and are aerobic muscles with plenty of mitochondria for ATP production
• Protein

  A polymerised protein is made up of many monomeric proteins
• LOCOMOTION AND MOVEMENT

  2022-23
• Relaxation of muscle

  Return of 'Z' lines to original position, i.e., relaxation, due to pumping back of Ca++ ions to sarcoplasmic cisternae
• White fibres have low myoglobin content, appear pale, and depend on anaerobic processes for energy
• Bone

  Has a very hard matrix due to calcium salts in it