Life Sciences Glossary: SI. No Red Muscle Fibres White Muscle Fibres

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Circumduction is a composite movement that involves successive flexion, extension and medial and lateral rotation.

General Points

  • The biceps is a flexor for the elbow joints.
  • The triceps is biceps antagonist and an extensor for elbow joint.
  • Arthritis or inflammation of a joint makes the joint painful and even immobilize the movements at the joints.
  • Red and White Muscle Fibers
  • The human skeletal muscles contain two major types of striated muscles fibers red and white.

SI. No Red Muscle Fibres White Muscle Fibers

  • Red muscle fibers are thinner.
  • White muscle fibers are thicker.
  • Darker in colour. Lighter in colour.
  • Slower in contraction rate.
  • Faster in contraction rate.
  • Rich in mitochondria poor in mitochondria.
  • Rich in red harem- protein myoglobin absent.
  • Depend mainly on aerobic metabolism Depend mainly on anaerobic glycolysis.
  • Perform slow and sustained contraction for long periods without fatigue.
  • Perform fast and strenuous work for short periods with fatigue.
  • Carry out aerobic contraction without accumulating much lactic acid. e. g. Extensor muscle on back of the body avian flight muscles used for prolonged slow flying, kite. Carry out anaerobic contraction with accumulating much lactic acid. e. g. Muscles of eyeball movement avian flight muscle used in short fast flying, sparrow.

Important Terms About Functioning of Muscle

  • Muscle Twitch: A single muscle contraction resulting from a single stimulus. It consists of 1. Latent period; 2. Contraction phase; and 3. Relaxation phase.
  • Tetanus: It is a continued state of contraction caused by rapid succession of many stimuli.
  • Contracture: Contracture is the extremely slow relaxation of a muscle due to over stimulation.
  • Fatigue: Fatigue is the inability of a muscle to contract due to depletion of its chemicals and lactic acid accumulation by repeated contraction.
  • Sub threshold Stimuli: Stimuli too weak to bring about a detectable response.
  • Threshold Stimuli: Stimuli strong enough to cause a response.
  • All or None Law: If a muscle fiber contracts in response to a stimulus, it contracts maximally or not at all.
  • Kymograph: Apparatus used to record muscle contraction are kymograph and polygraph.

Composition of Muscle

Muscle tissue is about 75 % water, 20 % protein and 5 % non-protein organics and minerals. Important non-protein organics include ATP, phosphocreatine, creating, urea and glycogen. Potassium is the most abundant mineral element in muscle. The oxygen carrying iron-protein pigment of muscle is called myoglobin.


Myoglobin is an important harem- containing globular protein; it is an oxygen storing protein in red- muscle fibers of vertebrate muscles. Myoglobin is especially abundant in the muscles of diving mammals such as whales, porpoises, dolphins and seals and in diving birds like penguins. Myoglobin stores oxygen as ox myoglobin. Ox myoglobin releases oxygen for utilization during muscle contraction. Myoglobin has only one harem group. The oxygen dissociation curve of myoglobin is a simple hyperbola (sigmoid for Oxyhaemoglobin) .

Skeleton Systems

  • Human endoskeleton includes elements made of living skeletal connective tissues called cartilages and bones. Osteology Isa the study of bones and choreology is the study of cartilages. Endoskeleton is mesodermal in origin.
  • Animals possess two forms of movements: locomotion and movement of body parts. In higher animals, movements and locomotion depend on the association of skeletal muscles with skeletal system. The scientific study of body movements is known as kinesiology.

Human Skeleton

  • The total number of bones in adult human is 206. The axial skeleton of adult man consists of 80 bones. The appendicular skeleton of adult man consists of 126 bones.
  • The number of bones in the skull of man is 28 (cranium bones 8. , facial bones 14 and ear icicles 3x2 = 6) . The bone common to cranium and face is frontal. Number of bones present in the human cranium is 8. The skull bones fit together by sutures. Sinuses are air spaces within skull bones. They only movable bone in the skull of man is mandible.
  • The vertebral column of man consists of 33 vertebrae. Human vertebral formula is . The number of bones in the vertebral column is 26. Vertebral column gives support to the trunk, provides places for the attachment of the ribs and bones of pelvis. Vertebral column permits movements and protects the spinal cord.
  • Usually, there are 12 pairs of ribs, but occasionally, there may be 11,13 or even 14 pairs. The first seven pairs of ribs known as ‘true ribs’ , the only one to reach the sternum directly pairs 8,9 and 10 are ‘false ribs’ , they are attached indirectly to sternum by means of cartilages. Last two pairs (11 and 12) fall far short of the sternum and are known as ‘floating ribs’ ‘Gorilla ribs’ are the extra floating ribs, if any.
  • Sternum or breastbone of man consists of three portions՚: manubrium, body and xiphoid process. Clavicles or the Human Skeleton.
Human Skeleton
(A) Anterior View(B) posterior View
CoracoidCervical vertebra
HummersThoraces vertebra

Collar bones articulate with the manubrium of the sternum. The sternum is a favored site for obtaining samples of hematopoietic (blood forming) tissue during diagnosis of suspected blood diseases.

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