TISSUES
Some important definitions:-
What is intercellular digestion- Every organism requires energy to be active. However, to obtain power from its outside environment, cells must not only retrieve molecules from their surroundings but also break them down. This process is known as intracellular digestion.
What is metabolism- Metabolism is defined as the bodily processes needed to maintain life.
What is osmoregulation- Osmoregulation is the active regulation of the osmotic pressure of an organisms body fluids, detected by osmoreceptors, to maintain the homeostasis of the organisms water content; that is, it supports the fluid balance and the concentration of electrolytes (salts in solution which in this case is represented by body fluid) to keep the body fluids from becoming too diluted or concentrated.
What is Neurons- The neuron is the basic working unit of the brain, a specialized cell designed to transmit information to other nerve cells, muscle, or gland cells.
What is Tissue- A group of cells similar in structure that work together to perform a particular function forms a tissue.
All living organisms are made up of cells. A unicellular organism (e.g., Amoeba, Paramecium, etc.)
Has a single cell in its body, i.e., a single cell performs all necessary life activities. For example, in Amoeba, movement of a cell, intake of food and respiratory gases (O2), intracellular digestion, metabolism, respiration, osmoregulation, and excretion are all done by the same cell. However, in multicellular organisms (e.g., a human being) there are millions of cells. Most of these cells are specialized to carry out a few functions efficiently. These functions are taken up by a different group of cells. Thus we can say that there a division of labor in the multicellular organisms, For example, in human beings muscle cells contract and relax to cause movement of a body part, nerve cells or neurons carry messages, blood flows to transport oxygen, food, hormones and waste materials (CO2, urea) and so on. Likewise, in plants, cells of phloem conduct food from leaves to other parts of the plant. Thus, we see that cells, which are specialized in a function, are grouped together and form a tissue. Blood, phloem, muscle, are all example of tissue. All cells of tissue have a common origin. For example, human nervous tissue (present in the brain, spinal cord, and nerves) has nerve cells or neurons which are basically same structurally and functionally. All nerve cells basically have a cell body or soma (the nucleus containing central part of a neuron) which has two types of branches, namely dendrites (to receive messages) and an axon to convey messages away from the soma). All neurons of nervous tissue are originated from the same germinal layer called ectoderm (more aptly the neural ectoderm).
A neuron
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