Muscles
Muscles are elastic in nature. They are capable of contraction in
response to stimulus from the central nervous system.
The muscle cells function like biological machines that convert chemical energy into mechanical work.
The mechanical work involves various movements including vital processes like contraction of the heart and blood vessels.
Approximately 40% of the body is skeletal muscle and almost 10% is smooth
and cardiac muscles.
Structure of a skeletal muscles:
A striated muscle is composed of many fibres arranged in bundles. The diameter of each fibre varies from 10 to 100 microns. The length of fibres ranges from 1 to 20mm. Each fibre is surrounded by a membrane, called the sarcolemma.
Each muscle fibres is made up of 4 to 20 thread-like structures called myofibrils. They are parallel to each other. The myofibrils are 1 to 3 micron in diameter. In between the myofibrils, the sarcoplasm is present. A small segment of the myofibril is called as the sarcomere.
Structure of sarcomere :
When a sarcomere is observed under a microscope, we could see alternative dense ( A band ) and light bands ( I band). The central region of the A band is often less dense and is known as the “H Zone”.
The ‘I band’ is bisected by a dense narrow line, the Z line. Thus each sarcomere includes repeating units between two Z lines in linear order as Z line, I band, A band, I band and next Z line.
Electron microscopic studies have shown that the striations are due
to the regular arrangement of 2 types of protein filaments. ‘A band’ contains
a set of thick filaments formed of the contractile protein myosin. It may
range upto 110 Ao in diameter and 1.5 micron in length.
The second set of thin filaments ( 50 Ao diameter) overlap the long
filaments in ‘A band’. The second set of filaments extend partly in ‘I band’
and partly in ‘A band’. These filaments are formed of a substance called
Actin.
Myosin, actin, tropomyosin and troponin are the four major proteins
which constitute the contractile machinery of muscle fibre. The energy for
muscle action is provided by ATP molecules.
Related Topics in Zoology:
Bio Zoology All Important Topics
- Human Physiology Introduction
- Nutrition
- Carbohydrates Poly hydroxyaldehydes (or) ketones
- Proteins (Polypeptides)
- Lipids
- Vitamins – Functions Of Vitamins
- Deficiency of Vitamin
- Minerals – Water – Role of water
- Balanced diet
- Obesity
- Digestive System
- Dental Caries (Tooth decay)
- Root Canal Treatment
- Peptic ulcer
- Hernia and Types
- Appendicitis (Appendix)
- Gall Stones
- Hepatitis
- Fractures – Types of fractures
- Mechanism of fracture
- Dislocation of joints
- Arthiritis
- Rickets and Osteomalacia – Orthopedics
- Muscles
- Mechanism of muscle contraction
- Types of muscle contraction
- Myasthenia Gravis
- Respiration – Process of pulmonary respiration
- Mechanism of Breathing
- Regulation of Respiration
- Pneumonia Tuberculosis Symptoms Treatment
- Bronchitis – Acute bronchitis, Chronic Bronchitis Causes
- Circulatory System – Functioning of Human heart
- Cardiac Cycle
- Coronary blood vessel and its significance
- Myocardial infarction
- Angina pectoris
- Angiogram – Angioplasty
- Atherosclerosis
- Heart block Echo cardiography Heart Valves
- Rheumatic Heart Disease (RHD), ICCU – (Intensive Coronary Care Unit)
- Blood Pressure
- Heart transplantation
- Pulse rate
- Cardio Pulmonary Resuscitation (CPR)
- Blood – Composition of plasma – Blood cells
- Clotting of Blood or Haemostasis
- Thrombosis
- Nervous system Co-ordination systems
- The Brain – Fore Brain, Midbrain, Hindbrain
- Memory
- Sleep – Types of sleep
- Stroke – Brain haemorrhage
- Alzheimer – Meningitis (Brain fever)
- Conditioned reflex
- Electroencephalography EEG
- Right and Left brain concept
- Spinal cord functioning
- Chemical co-ordination – Functions of Endocrine glands
- Hypothalamus
- Pituitary gland – hormone
- Hormones of Neurohypophysis – vasopressin
- Thyroid gland
- Parathyroid Gland
- Pancreas
- Adrenal gland
- Gonads
- Receptor Organs – Eye
- Photochemistry of Retinal visual Pigments
- Errors of refraction
- Optometry – Retinopathy
- Cataract – Lens Replacement – Glaucoma – Nyctalopia
- Eye Infections and Eye Care
- Ear
- Mechanism of hearing
- Defects of the ear
- Hearing Aid – Noise pollution
- Skin and functions of skin
- Melanin functions
- Effects of solar radiation / UV radiation – Skin grafting
- Dermatitis
- Tongue – Mechanism of Stimulation
- Excretion Ureotelism Nephron
- Mechanism of urine formation
- Renal Failure, Dialysis, Kidney Machines
- Kidney stone – Kidney transplantation
- Diabetes mellitus
- Functioning of male reproductive system
- Functioning of female reproductive system
- Ovulation and fate of the ovum – Menstrual cycle
- Fertilization
- Birth control