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Renin Angiotensin Mechanism.

Muscular Tissue

 Tissue level of organization: Muscular Tissue.

Introduction:

  • Groups of cells having similar structure and performing similar functions are called “Tissue.”

  • Muscular tissue is specialized for contraction and brings movement.

  • There are three specialized muscular tissues present in the body as follows,

    • Skeletal Muscles.

    • Smooth Muscles.

    • Cardiac Muscles.

Skeletal Muscle:

  • The name is derived as they are attached to the skeleton and are responsible for skeletons movement or say Locomotion.

  • Also called “Striated muscle” or “Voluntary muscle”.

  • As they work under our will power they are called “Voluntary muscle”.

  • On Microscopic examination they appear striated due to precise arrangement of contractile proteins inside the cell.

  • The plasma membrane and endoplasmic reticulum are special and hence called “Sarcolemma and Sarcoplasmic reticulum” respectively.

  • Muscle cells are also called “Myocytes” , “Muscle Fibers”.

  • Each muscle fiber contains many rod-like structures :Myofibrils.

  • Skeletal muscle cells are cylindrical in structure and contain many nuclei.

  • In the cell there is a typical arrangement of proteins responsible for contraction which gives striated appearance.

  • The impulses for muscle contraction generate at the brain or spinal cord and end at neuromuscular junctions.

Functions:

  1. Movement.

  2. Body posture.

  3. Regulation of body temperature: Generate heat.

Smooth Muscle:

  • Also called “Non Striated Muscles” as they don't show striations.

  • Do not work under will power hence called as “Involuntary Muscles”.

  • They are present in internal organs hence called “Visceral Muscles.”

  • The cells contain a single central nucleus and are spindle shaped.

  • Contractions are slower and more sustained than skeletal muscles.

Functions:

  1. Wall of blood vessels: Regulation of diameter.

  2. Eye: Regulation of pupil size.

  3. Intestine: Peristalsis.

  4. Uterus: Contraction.

Cardiac Muscle:

  • This tissue is only found in myocardium of the heart and hence called “Cardiac Muscle.”

  • This tissue when observed under a microscope shows striations like voluntary muscles but works like involuntary muscle hence it is considered as a special type of muscle.

  • The cells are branched and have a single nucleus.

  • The cell membrane at end is folded and fits in matching folds of adjacent cell membranes forming “intercalated discs”.

  • Intercalated disc is an important feature of cardiac muscle as it makes passage of electric impulses faster.

  • Heart beats on its own, the nerve supply only increases or decreases rate and force of contraction as per need of the situation.

Functions:

  1. Contractions of heart.

Commonly Asked Questions.

  1. Write a note on “Muscular Tissue.”

  2. Draw a well labelled diagram of,

    1. Cardiac Muscle.

    2. Smooth Muscle.

    3. Skeletal Muscle.
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