Wednesday, July 29, 2020

Structural Organisation In Animals - Notes | Class 11 | Part 3: Animal Tissues | Muscle and Neural Tissues

7. STRUCTURAL ORGANISATION IN ANIMALS

ANIMAL TISSUES


III. MUSCLE TISSUE


-    The tissues made of many muscle fibres (muscle cells).

-    Muscle fibres are composed of numerous fine myofibrils.

-    Muscle fibres can contract (shorten) and relax (lengthen).

-    Muscles take part in locomotion and movements.

-    Muscles are 3 types: skeletal, smooth and cardiac.


  1. Skeletal (striated or voluntary) muscle


-    They are attached to bones. E.g. Biceps.

-    Striations are present in muscle fibres.

-    Muscle fibres are bundled together in a parallel fashion.

-    A sheath of tough connective tissue encloses several bundles of muscle fibres.


2. Smooth (non-striated or visceral) muscle


-    Involuntary and fusiform (Fibres taper at both ends).

-    No striations.

-    Cell junctions hold them together and they are bundled together in a connective tissue sheath.

-    They are seen in the wall of internal organs such as the blood vessels, stomach and intestine.


3. Cardiac muscle


-    Involuntary muscle seen only in the heart.

-    Cell junctions fuse the plasma membranes of cardiac muscle cells and make them stick together.

-    Communication (gap) junctions (intercalated discs) at some fusion points allow cells to contract as a unit, i.e., when a cell receives signal to contract, other cells also contract.


IV. NEURAL TISSUE


·   Made up of neurons (unit of neural system).

·   Responsible for control and co-ordination of the body.

·   Neurons are excitable cells. They carry impulses.

·   Neurons are protected and supported by neuroglial cells.

·   Neuroglia make up more than half the volume of neural tissue.


ORGAN AND ORGAN SYSTEM


·   Cells → tissues → organs → organ systems.

·   This organization is essential for better coordinated activities of cells.

·   An organ is made of one or more type of tissues. E.g. Heart has epithelial, connective, muscular & neural tissues.

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