Skip to main content

Nutrient cycle in environment

  BIO-GEO CHEMICAL CYCLE OR NUTRIENT CYCLE       Bio  -    Living organism       Geo  -    Rock, Soil, Air, Water Chemical   -  Material or Nutrients        Cycle   -   Path All the types of material required by ecosystem in addition of energy, are available continuously to system through recycling. Thus there is a constant exchange of materials between the living organism and their abiotic environment through the recyling of materials. This phenomenon is called Bio-geo chemical cycle. Note: Environment factors,e.g soil , moisture, ph, temperature etc, regulate the release of nutrients into the atmosphere. Biochemical cycle The following types of cycle are found in an ecosystem. (i) Gaseous Cycle - C, H, N. O cycles. Reservoir is in the atmosphere (air) or in Hydrosphere(water). Sedimentary cycle - P. S, Ca cycles reservoirs are in earth's crust (lithosphere). Note : ...
Post a Comment

MECHANISM OF MUSCLE CONTRACTION

  •  MECHANISM OF MUSCLE CONTRACTION


  1. Mechanism of muscle contraction is best explained by 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.
  2. Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron. A motor neuron alongwith the muscle fibres connected to it constitute a motor unit. The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate.

  3. A neural signal reaching this junction releases a neurotransmitter (Acetyl choline) which generates an action potential in the sarcolemma. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.
  4. 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. Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge. This pulls the attached actin filaments towards
  5. 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 (contraction), the T bands get reduced, whereas the 'A' bands retain the length.
  6. The myosin, releasing the ADP and P1, goes back to its relaxed state. A new ATP binds and the cross-bridge is broken.
  7. 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.
  8. Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen in them, causing fatigue.     
  9. Role of ATP :
  10. (i) The 'back & forth' movement of myosin head with in the groove.
  11. (ii) Deatatachment of myosin head from the actini


Labels:

Comments

Post a Comment

Popular posts from this blog

Composition White blood cells(WBC)

  WBC WBC (White Blood Corpuscles) are also called as leucocytes because they are colourless. TLC- Total leucocyte count Number of WBC /mm 6000 - 8000/mm (2000-3000) DLC :- Differential leucocyte count: number/ (%) of different type of leucocyte in per cubic mm. of blood. Acidophils    -    2-3% of TLC Basophils     -    0.5% -1% TLC Neutrophils   -    60 -65% TLC Monocytes    -    6-8% TLC Lymphocytes  -    20-25% TLC Leucocytosis :- Increase in TLC. This condition occur in bacterial & viral infection. Leucocytopenia :- Decrease in TLC. Normally TLC increases in bacterial & viral infection but in typhoid &  AIDS, TLC decreases. Leukemia :- Abnormal increase in TLC (more than 1 Lakh) it is called as blood cancer. On the basis of nucleus & nature of cytoplasm, Leucocyte are of two type 1. Granulocytes   a) In their cytoplasm granules are present which can be...
Post a Comment
Read more

Nutrient cycle in environment

  BIO-GEO CHEMICAL CYCLE OR NUTRIENT CYCLE       Bio  -    Living organism       Geo  -    Rock, Soil, Air, Water Chemical   -  Material or Nutrients        Cycle   -   Path All the types of material required by ecosystem in addition of energy, are available continuously to system through recycling. Thus there is a constant exchange of materials between the living organism and their abiotic environment through the recyling of materials. This phenomenon is called Bio-geo chemical cycle. Note: Environment factors,e.g soil , moisture, ph, temperature etc, regulate the release of nutrients into the atmosphere. Biochemical cycle The following types of cycle are found in an ecosystem. (i) Gaseous Cycle - C, H, N. O cycles. Reservoir is in the atmosphere (air) or in Hydrosphere(water). Sedimentary cycle - P. S, Ca cycles reservoirs are in earth's crust (lithosphere). Note : ...
Post a Comment
Read more

ORIGIN AND EVOLUTION OF MAN

Ramapithecus - Australopithecines - homo habilis - Homo erectus- Neanderthal man - Homo sapiens Modern primates are the end products of evolutionary process that began some 65 mya from shrew like insectivores. The firstly recognisabe anthropoid in the primate fossil record were discovered in the Fayum depression of Egypt. About 15 mya ,primate called Dryopithecus and Ramapithecus existing. About 3 - 5 mya, man like primates existed in Eastern Africa. They were probably 4 feet long and walked up right. About 2 mya Australopithecines  lived in East Africa grasslands. They hunted with stones and ate fruits. The first human like being was the hominoid the Homo Habilis.  Their brain capacities were between 650-800cc. About 1-5 mya fossils of next stage human the Homo erectus were discovered from java in 1891. Their brain capacities were 900cc and probably ate meat. About 100000-40000 years back Neandarthal man with brain capacities of 1400cc lived east and central Asia.  Abo...
Post a Comment
Read more