Table At Glance

Points To Remember


Characteristics of Living Organisms : Growth, reproduction, metabolism, cellular organization, consciousness (ability to sense environment), self-replicating and self regulation.

  • Reproduction and growth are NOT defining properties.
  • Metabolism, cellular organization and consciousness are defining properties.

Biodiversity : Term used to refer to the number of varieties of plant and animals on earth.

Nomenclature: standardize the naming of living organism such that a particular organism is known by the name all over the world.

Identification: nomenclature or naming is only possible when the organism is described correctly and we known to what organism the name is attached to.

Need for classification: To organize the vast number of plants and animals into categories that could be named, remembered, studied and understood.

Rules for Nomenclature:

  • Latinized names are used, written in italics
  • First word represents the genus, second word is species name.
  • Printed in italics; if handwritten then underline   separately.
  • First word starts with capital letter while species name written in small letter.

ICBN: International Code of Botanical Nomenclature (for giving scientific name to plants.)

ICZN:  International Code of Zoological Nomenclature (for giving scientific name to animals.)

Taxonomy: Study of principles and procedures of classification.

Binomial Nomenclature: Given by Carolus Linnaeus. Each scientific name has two components – Generic name + Specific epithet.

Systematics:  It deals with classification of organisms based on their diversities and relationships among them. Term was proposed by Carolus Linnaeus who wrote ‘Systema Naturae’.

Taxonomic Hierarchy: Arrangement of various steps (categories or taxa Species → Genus → Family → Order → Class → Phylum (for animals) /Division (for plants) Kingdom→

Species: All the members that can interbreed among themselves and can produce fertile offsprings are the members of same species. This is the bio-logical concept of species proposed by Mayer.

Three Domains of Life: Proposed by Carl Woese in 1990 who also proposed the six kingdom classification for living organisms. The three Do-mains are Archaea, Eubacteria and Eukarya.

Herbarium: Storehouse of dried, pressed and preserved plant specimen on sheets.

Botanical Garden: Collection of living plants for reference.

Taxonomical aids: Zoological Park (Places where wild animals are kept in protected environment.)

  • Keys (Used  for identification of plant and animals on the basis of similarities and dissimilarities.)
  • Fauna: (Index to animal species found in a particular area)
  • Flora (Index to plant species found in a particular area.)
  • Manuals (Provide information for identification of name of species in an area.)
  • Monograph (Contain information on one taxon.)




  • Earliest Classification was given by Aristotle. Divided plants into herbs, shrubs and trees. Animals into those with RBC’s and those who do not have it.

Two kingdom classification :

  • Given by Carolous Linnaeus − Plant kingdom and Animal kingdom.

Five kingdom classification : 

  • By R.  H. Whittaker. Monera, Protista, Fungi, Plantae and Animalia are the five kingdoms.

Kingdom Monera :

Bacteria :

  • Have bacteria a sole member.
  • Bacteria can have shapes like: Coccus (spherical), Bacillus (rod-shaped), Vibrio comma shaped) and sprillum (spiral shaped).
  • Bacteria found almost everywhere and can be Photosynthetic autotrophs, Chemosynthetic autotrophs or Heterotrophs.

Archaebacteria :

  • Differs from bacteria having different cell wall structure.
  • They live in most harsh habitats
  • Halophiles (salt-loving)
  • Thermophiles (in hot springs)
  • Acidophiles (high acidic condition)
  • Methanogen (marshy area)
  • Methanogen are also found in the gut of ruminant and produces biogas.

Eubacteria :

  • Called true bacteria having a rigid cell wall, and if motile a flagellum.
  • They also known as blue green algae or Cyanobacteria.
  • Cyanobacteria are photosynthetic autotrophs.
  • Unicellular, colonial or filamentous, marine and terrestrial algae.
  • Colonies are surrounded by gelatinous sheath.
  • Some of these can fix atmospheric nitrogen by specialized cells called heterocyst, e.g. Nostoc and Anabaena.
  • Chemosynthetic autotrophs: Oxidize various   inorganic   substances   like nitrates/nitrites, ammonia and use released energy for their ATP production.
  • Heterotrophic bacteria:
    • Mostly decomposer
    • Helpful in making curd from milk
    • Produce antibiotics
    • Symbiotically associated with leguminous plant and fix nitrogen.
    • Some are pathogen causing diseases like cholera, typhoid, and tetanus.
  • Bacteria reproduce mainly by fission, also produce spore in unfavorable condition.
  • Reproduce sexually by transfer of DNA form one bacteria to other, the process called conjugation.

Mycoplasma :

  • Completely lack cell wall.
  • Smallest living cells.
  • Can survive   without oxygen.
  • Pathogenic in animals and plants.

Kingdom Protista :

  • All are unicellular and eukaryotic.
  • Mostly aquatic, can live in moist places.
  • Forms a link between plants, animals and fungi.
  • The cell contain nucleus and membrane bound organelles.

Chrysophytes :

  • Includes diatoms and golden algae (desmids)
  • Found in freshwater or marine water.
  • Mostly planktonic ( passive swimmer)
  • Photosynthetic.
  • Cell walls overlap to fit together like a soap box.
  • Cell wall contains silica hence indestructible.
  • Their accumulation forms ‘Diatomaceous Earth’.
  • Used in polishing, filtration of oils and syrups.
  • Diatoms are the chief ‘producers’ in the oceans.

Dinoflagellates :

  • Marine, photosynthetic.
  • Cell wall has stiff cellulose plates.
  • Appears yellow, green, brown, blue or red depending on the pigments.
  • Have two flagella − one longitudinal and other transversely in a furrow between wall plates.
  • Red Dinoflagellates (Gonyaulax) form red tides.




Artificial System of Classification :

  • Used superficial morphological characters.
  • Based on a few characteristics like habit, colors, number and shape of leaf.
  • Mainly based on vegetative characters.
  • Such system developed by Linnaeus.

Natural System of Classification :

  • Based on natural affinities among organisms
  • Included external as well as internal features like anatomy, embryology and phytochemistry.
  • Developed by George Bentham and J. D. Hooker

Phylogenetic System of Classification :

  • Based on evolutionary relationships between the various organisms.
  • Organism belongs to same taxa have a common ancestors.
  • Developed by Hutchinson.

Numerical Taxonomy :        

  • Carried out using computers
  • Based on all observable characteristics
  • Data processed after assigning number and codes to all the characters.

Cytotaxonomy :       

  • Based on cytological information.
  • Gives importance to chromosome number, structure and behaviour.

Chemotaxonomy :

  • Based on chemical constituents of the plants.


  • Chlorophyll bearing, simple, thalloid, autotrophic and mostly aquatic organisms. Moist stone, soils and wood are the other habitat.
  • The size ranges from microscopic unicellular forms like Chlamydomonas, to colonial forms like Volvox and to filamentous forms like Ulothrix and Spirogyra. A few marine forms such as kelps, form massive plant bodies.
  • Reproduce vegetatively by fragmentation.
  • Reproduce asexually mostly by producing motile spore called zoospores.
  • Reproduce sexually by producing gametes.
  • Isogamous: both gametes are same size and motile
  • Anisogamous: both gametes are dissimilar in size but motile.
  • Oogamous: male gamete is smaller but motile, female gamete is large and non- motile.

Importance of Algae :

  • At least half of the total carbon dioxide fixation on earth carried out by them.
  • Increase oxygen level in the environment.
  • Many species like Laminaria, Sargassum etc. are used as food.
  • Agar obtained from Gelidium and Gracilaria is used in ice-creams and jellies and also used to culture bacteria.
  • Algin obtained from brown algae and carrageen from red algae used commercially.
  • Chlorella and Spirullina are unicellular algae, rich in protein and used as food supplement even by space travelers.



Levels of organization :

  • Cellular level
  • Tissue level
  • Organ level
  • Organ system level

Circulatory System :

Open type: Blood pumped out through heart. Cells and tissues are directly bathed in it.

Closed type: Blood is circulated through vessels.

Symmetry :

  • Asymmetrical: Cannot be divided into equal halves through median plane. e.g., Sponges.
  • Radial symmetry: Any plane passing through central axis can divide organism into equal halves. e.g., Hydra.
  • Bilateral symmetry: Only one plane can divide the organism into equal halves. e.g., Annelids and Arthropods.


  • Diploblastic: Cells arranged in two embryonic layers i.e. external ectoderm and internal endoderm. (Mesoglea may be present in between ectoderm and endoderm) e.g., Coelenterates. (Cnidarians)
  • Triploblastic: Three layers present in developing embryo i.e., ectoderm, endoderm and mesoderm. e.g., Chordates.
  • Coelom (Body cavity which is lined by mesoderm)
  • Coelomates: Have coelom e.g., Annelids, Chordates etc.
  • Pseudocoelomates: No true coelom as mesoderm is present in scattered pouches between ectoderm and endoderm. e.g., Aschelminthes.
  • Acoelomates: Body cavity is absent. E.g. Platyhelminthes.
  • Metamerism: If body is externally and internally divided into segments with serial repetition of at least some organs then phenomenon is called metamerism.        e.g., Earthworm.
  • Notochord: Rod-like structure of mesodermal origin, formed during embryonic development on the dorsal side.  e.g., Chordates.


  • Also called sponges.
  • Are usually marine and asymmetrical.
  • Have cellular level of organization.
  • Food gathering, respiratory exchange and removal of wastes occur through water canal system.
  • Digestion intracellular.
  • Ostia (minute pores on body), spongocoel (body cavity) and osculum help in water transport. They are lined bychoanocytes (collar cells).
  • Body wall has spicules and spongin fibers.
  • Animals are hermaphrodite.
  • Fertilization internal.
  • Development is indirect, with larval stage which metamorphoses to adult. e.g., Sycon, Euspongia.


  • Also called Cnidarians.
  • Are usually marine and radially symmetrical.
  • Sessile or free-swimming.
  • Have tissue level of organization
  • Diploblastic.
  • Presence of cnidoblast, for anchorage, defense and capture of prey.
  • Central body cavity called gastro-vascular cavity or coelenterone.
  • Digestion extracellular and intracellular.
  • Blind sac type body plan, with one opening called hypostome.
  • Body wall composed of calcium carbonate.
  • Exhibit two body forms: polyp and medusa e.g., Hydra, Aurelia.
  • Alternation of generation between body forms called Metagenesis occurs in Obelia where Medusa sexually   reproduced and polyp asexually reproduced. •e.g., Physalia, Adamsia.


  • Also called as sea walnuts or comb jellies.
  • Are exclusively marine, radially symmetrical.
  • Have tissue level organisation, are diploblastic.
  • Digestion both extra and intracellular.
  • Body has eight external rows of ciliated comb plates for locomotion.
  • Show Bioluminescence (living organism emit light).
  • Sexes are not separate i.e. hermaphrodite.
  • Reproduce only by sexual methods.
  • External fertilization.
  • Indirect development

e.g., Ctenoplana. Pleurobranchia




  • Morphology: The study of various external features of the organism is known as morphology.
  • Adaptation: Any alteration in the structure or function of an organism or any of its part that results from natural selection and by which the organism becomes better fitted to survive and multiply in its environment.
  • The Root: The root is underground part of the plant and develops from elongation of radicle of the embryo.

Various types of root :

  • Tap root:
    • Originated from the radicle.
    • Persistent in dicot plant. E.g. gram, pea , mango
  • Fibrous root
    • Originates from the base of the stem.
    • Large number of roots replaces the primary root.
    • This type of root found in monocot plant. E.g. wheat, paddy, grass.
  • Adventitious root
    • Roots developed from any part of the plant other than radicle.
    • Found in grass, Monstera and the banyan tree.

Function of root :

  • Absorption of water and mineral from soil
  • Anchorage of the plant body
  • Storing reserve food material.
  • Synthesis of plant growth regulators.

Regions of root :

  • Root Cap : The root is covered at the apex by the thimble-like structure which protects the tender apical part.
  • Region of meristematic activity :
    • Cells of this region have the capability to divide.
    • The cells of this region are very small, thin-walled and with dense protoplasm.
  • Region of elongation :
    • Cells of this region are elongated and enlarged.
  • Region of Maturation :
    • This region has differentiated into matured cells.
    • Some of the epidermal cells of this region form thread-like root hairs, which absorbs water and minerals from the soil.

Modifications of Root :

  • Roots are modified for support, storage of food, respiration.
  • For  support  :  Prop  roots  in  banyan  tree,  stilt  roots  in  maize  and sugarcane.
  • For respiration: pneumatophores in Rhizophora (Mangrove).
  • For storage of food:  Fusiform (radish), Napiform (turnip), Conical (carrot).

The Stem :

  • Stem is the aerial part of the plant and develops from plumule of the embryo.
  • It bears nodes and internodes.
  • Bears bud, may be axillary or terminal
  • Main function is to spreading branches bearing leaves, flower and fruits.

Modifications of Stem :

  • For food storage: Rhizome (ginger), Tuber (potato), Bulb (onion), Corm and Colocasia).
  • For support: Stem tendrils of watermelon, grapevine, and cucumber.
  • For protection: Axillary buds of stem of citrus, Bougainvillea get modified into pointed thorns. They protect the plants from animals.
  • For vegetative propagation: Underground stems of grass, strawberry, lateral branches of mint and jasmine.
  • For assimilation of food: Flattened stem of opuntia contains chlorophyll and performs photosynthesis.

The Leaf :

  • Developed from shoot apical meristem, flattened, green structure.
  • Manufacture the food by photosynthesis. It has bud in axil.
  • A typical leaf has leaf base, petiole and lamina.
  • Leaf attached to the stem by leaf base.
  • May bear two small leaves like structure called stipules.
  • Leaf base may swollen to form pulvinus.
  • The structure that holds the leaf called petiole.
  • The green expanded part of the leaf is called lamina or leaf blade.

Venation :

  • The arrangement of veins and the veinlets in the lamina of leaf is termed as venation.
  • Veinlets form a network – reticulate venation. (dicot leaf)
  • Vein runs parallel to each other – parallel venation. (monocot leaf)



  • Study of internal structure of plant is called anatomy.
  • In plants cells are the basic unit.
  • Cells organized into tissues and tissues organized into organs.


  • A group of cells having common origin and perform one function.
  • Plant tissues are classified into two types:-
    • Meristematic tissue.
    • Permanent tissue

Meristematic tissues :

  • Growth in plants is restricted to specific regions with active cell division called meristems.


  • Different types of meristems are:-
    • Apical meristem:
      • Occurs in the shoot and root tips.
      • Primary meristem
      • Increase the length of plant
  • Intercalary meristem :
    • Present in-between mature tissues.
    • Primary meristem
    • Occurs in grasses and regenerate parts removed by grazing.
  • Lateral meristem:
    • Occurs in the mature regions of roots and shoots.
    • Also known as secondary meristem.
    • Responsible for producing secondary tissues.
    • Fascicular vascular cambium, interfascicular cambium and cork cambium are example of lateral meristem.
  • Axillary bud :
    • During formation of leaves and elongation of stem, some cells ‘left behind’ from shoot apical meristem, constitute the axillary bud.
    • Present in the axils of leaves and are capable for forming a branch or a flower.
  • Permanent tissues :

    • Cells produced from primary or secondary meristem stop dividing and differentiated structurally and functionally, termed as permanent cells.
    • A group of permanent cell constitutes the permanent tissues.
    • Permanent tissues having similar in structure and function are called simple tissues.
    • Permanent tissues having many different types of cells are called complex tissues.

    Simple tissues :

    • Simple tissues made of only one type of cells.

    Parenchyma :

    • Forms major component within organs.
    • Cells are isodiametric.
    • Thin cell wall made of cellulose.
    • Cells may be spherical, oval, round, polygonal or elongated shape.
    • Cells are closely packed or have small intercellular space.
    • Perform various functions such as photosynthesis, storage, secretion.

    Collenchyma :

    • Found either in homogeneous layer of in patches.
    • Cell wall thickened in the corner due to deposition of cellulose, hemicelluloses and pectin.
    • Cells are oval, spherical or polygonal in shape
    • Often contain chloroplasts.
    • No intercellular spaces.
    • Provide mechanical support to the growing part of the plant such as young stem and petiole of a leaf.

    Sclerenchyma :

    • Consists of long, narrow cells
    • Cell wall is thick and lignified.
    • Cell wall with few or numerous pits.
    • Cells are usually dead and without protoplast.
    • Provides mechanical support to the organs.
    • Sclerenchymas are of two types on the basis of origin, form, structure.

    Fibres :

    • Thick walled
    • Elongated and pointed cells
    • Generally occurs in group in various parts of the plant.



    Tissue : A group of similar cells along with intercellular substances which perform a specific function.

    Animal tissues are classified into four types:

    • Epithelial tissues.
    • Connective tissues.
    • Muscular tissues.
    • Neural tissues.

    Epithelial tissues :

    • These tissues commonly called epithelium.
    • Has free surface, which faces either a body fluid or the outside environment.
    • Cells are compactly packed with little intercellular matrix.
    • There are two types of epithelial tissues:
      • Simple epithelium.
      • Compound or stratified epithelium.
    • Simple epithelium is composed of a single layer of cells and functions as a lining for body cavities, ducts and tubes.
    • The compound epithelium consists of two or more cell layers and has protective function as it does in our skin.

    Simple epithelium, on the basis of modification, divided into three types:

    • Squamous
    • Cuboidal
    • Columnar.

    Squamous epithelium :

    • Made of single thin layer of flattened cells with irregular boundaries.
    • Found in the wall of blood vessels and air sacs of lungs.
    • Functions as diffusion boundary.

    Cuboidal epithelium :

    • Composed of a single layer cube – like cells.
    • Found in ducts of glands and tubular part of nephrons in kidneys.
    • Main function is secretion and absorption.

    Columnar epithelium :

    • Composed of a single layer of tall and slender cells.
    • Their nuclei located at the base.
    • Free surface may have microvilli.
    • Found in the lining of stomach and intestine
    • Helps in absorption and secretion.

    Ciliated epithelium :

    • It is a modified Cuboidal or columnar epithelium.
    • Cell bears cilia on their free surfaces.
    • Found in the inner surface of hollow organs like bronchioles and fallopian tubes.
    • Their function is to move particles or mucus in a specific direction over the epithelium.

    Glandular epithelium :

    • It is a modified Cuboidal or columnar epithelium.
    • Get specialized for secretion.
    • Simple glands having unicellular and isolated cells of alimentary canal.
    • Multicellular glands: consisting of cluster of cells, as in salivary gland.
    • Exocrine gland: the secretory product transported to a point by means of a duct. These glands secrete mucus, saliva, ear wax, milk, digestive enzymes etc
    • Endocrine gland: commonly called as ductless gland, because the secretory products directly poured into blood. The glands secretes hormone.

    Compound epithelium :

    • Made of more than one layer of cells.
    • Limited role in absorption and secretion.
    • Main function is to provide protection against chemical and mechanical stresses.
    • They cover the dry surface of skin, moist surface of buccal cavity, pharynx, inner lining of duct of salivary gland and pancreatic duct.




    Digestion : enzymatic conversion of complex food substances to simple absorbable forms in the alimentary canal.



    • Alimentary canal
    • Digestive glands or associated glands.

    Alimentary canal :

    • The alimentary canal begins with mouth and ends with anus.
    • Mouth leads to buccal cavity or oral cavity.
    • Oral cavity has teeth and muscular tongue.
    • Each tooth embedded in a socket of jaw bone: such attachment called thecodont.
    • Diphyodont : human has two sets of teeth in their life time:
      • Milk teeth or deciduous teeth
      • Permanent teeth.
    • Heterodont : teeth are of unequal shape and size.
      • Incisor (I)
      • Canine (C)
      • Premolar (PM)
      • Molar (M).
    • Dental formula : arrangement of teeth in each half of the upper jaw and lower jaw.


    • Dental formula of human adult is
    • The hard chewing surface of the teeth made up of enamel.
    • The tongue is a freely movable muscular organ attached to the floor of the oral cavity by the frenulum.
    • The upper surface of tongue has small projections called papillae, some of which bears taste buds.
    • The oral cavity leads into a short pharynx which serves as a common passage for food and air.
    • Oesophagus and the trachea open into the pharynx.
    • Opening of wind pipe or trachea called glottis, and that of oesophagus is called gullet.
    • The cartilaginous epiglottis prevents the entry of food into the glottis during swallowing.
    • Oesophagus connects pharynx with stomach.
    • Opening of oesophagus is regulated by gastro-oesophageal sphincter.
    • The stomach has three parts:
      • Cardiac: into which oesophagus opens.
      • Fundus: air filled portion of stomach.
      • Pyloric: portion opens into the small intestine.
    • Small intestine distinguished into three parts:
      • Duodenum: ‘U’ shaped first part.
      • Jejunum: longer, coiled middle portion.
      • Ileum: highly coiled posterior part.
    • The opening of stomach into the duodenum is guarded by pyloric sphincter.
    • Large intestine consists of three parts:
      • Caecum
      • Colon
      • Rectum.
    • Caecum is a small blind sac which hosts some symbiotic micro-organisms.
    • Caecum has a finger-like blind tubular projection called vermiform appendix.
    • The Caecum opens into colon, which has three distinct part-
      • Ascending colon
      • Transverse colon
      • Descending colon
    • The descending colon opens into rectum which opens to out through anus.

    Histolology of alimentary canal :

    • Alimentary canal from oesophagus to rectum has four layers.
      • Serosa.
      • Muscularis.
      • Sub mucosa.
      • Mucosa.
    • Serosa is the outermost layer and is made up of a thin mesothelium with some connective tissues.
    • Muscularis is formed by smooth muscles arranged outer longitudinal and inner circular layers.
    • Sub-mucosa is formed by loose connective tissues containing nerves, blood and lymph vessels.
    • Mucosa is the innermost layer made of endothelium.
    • Mucosa forms irregular folds (rugae) in the stomach and small finger like folding called villi in the small intestine.
    • The cells lining the villi produce numerous microscopic projections called microvilli giving a brush border appearance.
    • These modifications increase the surface area for absorption.
    • Villi are supplied with a network of capillaries and a central lymphatic vessel called lacteal.
    • Epithelial cells of mucosa contain secretory cells which secretes digestive enzymes.
    • Mucosa also forms glands in the stomach (gastric gland)
    • Mucosa forms crypts in between the bases of villi in the intestine called Crypts of Lieberkuhn.


    Blood: A special connective tissue that circulates in principal vascular system of man and other vertebrates consisting of fluid matrix, plasma and formed elements.
    Plasma :

    The liquid part of blood or lymph which is straw coloured, viscous fluid constituting nearly 55 per cent of blood.
    90-92 percent of plasma is water and 6-8% proteins.
    Fibrinogen, globulin and albumins are the major protein found in plasma.
    Fibrinogen is required in blood clotting or coagulation of blood.
    Globulins involved in defense mechanism of the body.
    Albumin helps in osmotic balance of blood.
    Plasma also contains small amounts of minerals, glucose, amino acids, lipids etc.
    Plasma without the clotting factors is called serum.
    Formed elements :

    Erythrocytes :

    Also known as RBC (red blood cells) is the most abundant of all the cells of blood.
    5 – 5.5 million RBC found per mm-3 of the blood.
    Produced from the red bone marrow in the adult.
    RBCs devoid of nucleus in most of mammals.
    Biconcave in shape
    Red in color due presence of complex conjugated protein called haemoglobin.
    12-16 gm of haemoglobin present per 100 ml of blood in a healthy adult.
    RBCs have average life span of 120 days after which is destroyed in the spleen.
    Spleen is commonly known as the graveyard of RBCs.
    Leukocytes :

    Also known as white blood cells (WBC).
    They are colorless due to lack of haemoglobin.
    They are nucleated and relatively lesser in number which averages 6000-8000 mm-3 of blood.
    We have two main category of WBC;


    Neutrophils (60-65%) of the total WBCs are phogocytic in nature.
    Basophils (0.5-1 %), secretes histamine, serotonin and heparin and also involved in inflammatory reactions.
    Eosinophils (2-3 %) resist infection and also associated with allergic reaction.
    Lymphocytes (T cells and B cells) constitute 20-25 percent and involved in the immune response of the body.
    Monocytes (10-15%), becomes macrophages.
    Thrombocytes :

    Also known as blood platelets.
    Produced from fragmentation of megakaryocytes.
    Blood normally contain 1, 500, 00 – 3, 500, 00 platelets mm-3.
    Involved in releasing thromboplastin required to initiate blood coagulation.

    Two blood grouping mechanisms ABO and Rh system.
    ABO grouping :

    ABO grouping is based on the presence or absence of two surface antigens on the RBCs namely A and B.
    Plasma of different individuals contains two natural antibodies, anti ‘A’ and ‘B’.
    In a mismatched transfusion the antigen of the donor reacts with antibody of the recipient to cause a reaction called clumping of agglutination.
    Person with blood group ‘O’ has no antigen hence can donate blood anybody, called universal donor.
    Person with blood group ‘AB’ has no antibody in his plasma hence can receive blood from anybody, called universal recipient.



    The human neural system divided into two parts –
    The central nervous system (CNS)
    The peripheral nervous system (PNS)

    The CNS includes the brain and spinal cord and is the site of information processing and control.
    The PNS comprises all nerves of the body associated with CNS.
    Cranial nerves: nerves arises from the brain (12 pairs)
    Spinal nerves: nerves arises from the spinal cord (33 pairs)

    The nerve fibres (Cranial and spinal nerves) are of two types –
    Afferent fibres: transmits impulses from the tissues to the CNS
    Efferent fibres: transmits impulses from the CNS to the tissues.

    The PNS is divided into two divisions –
    Somatic neural system.
    Autonomic neural system.
    Sympathetic neural system.
    Parasympathetic neural system.

    The somatic neural system relays impulses from the CNS to skeletal muscles.
    The autonomic neural system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body.

    A neuron composed of three major parts –
    Cell body

    The cell body contains cytoplasm with typical cell organelles and specific granular body called Nissl’s granules.
    Short fibres which profusely branched projects out of cell body called dendrites.
    The axon is a long fibre, branched at the end.
    Each branch terminates as a bulb-like structure called synaptic knob.
    Based on the number of axon and dendrites the neurons are of following types –
    Multipolar: one axon and several dendrites – found in cerebral cortex.
    Bipolar: one axon and one dendrite – found in retina of eye.
    Unipolar: cell body with one axon only – found in embryonic stage.

    The axon may be myelinated or non-myelinated.
    The myelinated nerve fibres are enveloped with Schwann cells, which form myelin sheath around the axon. The gaps between two adjacent myelin sheath are called Nodes of Ranvier.
    Cranial and spinal nerves are myelinated.
    Autonomic and somatic neural fibres are non-myelinated.

    Polarized membrane/Resting Potential :

    In resting phase when neuron is not conducting an impulse, the axonal membrane is called polarized. This is due to difference in concentration of ions across the axonal membrane.
    At Rest :
    Axoplasm inside the axon contains high conc. of K+ and low conc. of Na+.
    The fluid outside the axon contains low conc. of K+ and high conc. of Na+.

    As a result the outer surface of axonal membrane is positively charged and inner surface is negatively charged. The electric potential difference across the resting plasma membrane is called resting potential.
    Action Potential :

    When a nerve fibre is stimulated, the permeability of membrane to Na+ is greatly increased at the point of stimulus (rapid influx of Na+) and hence polarity of membrane is reversed and now membrane is said to be depolarized.
    The electric potential difference across the plasma membrane at that site is called action potential, which in fact termed as nerve impulse.
    Depolarization is very rapid, so that conduction of nerve impulse along the entire length of axon occurs in fractions of second.
    Depolarization is followed by the increase in permeability of K+ to the membrane leads to change in polarization i.e. +ve charge outside and –ve charge inside. It is called repolarization.
    Regain of resting potential takes place due to action of Na+/K+ ATPase enzyme which transports three Na+ inside and two K+ inside with expense of one ATP. It continues till the resting potential becomes -70 mv.
    Transmission of impulses through synapse :

    The functional junction between two neurons is called synapse.
    A synapse is formed by the membranes of a pre-synaptic neuron and a post-synaptic neuron, which may or may not be separated by a gap called synaptic cleft.
    There are two types of synapses:
    Electrical synapse: pre and post synaptic membrane with close proximity without any synaptic cleft.
    Chemical synapse: the pre and post synaptic membrane is separated by a fluid filled synaptic cleft.



    Endocrine glands lacks ducts and are hence, called duct less glands.
    The chemicals secreted by endocrine gland is called hormone.
    Hormones are the chemical synthesized in the endocrine gland, acts as chemical messengers, transported in blood to distance place, where it acts on specific cells/tissue/organs, called target organ.
    Current specific definition of hormone is- hormones are non-nutritional chemicals which act as intercellular messengers and are produced in trace amount.
    The hypothalamus :

    It is the basal part of the diencephalon, fore brain.
    It contains several groups of neurosecretory cells called nuclei which produce hormones.
    These hormones regulate the synthesis and secretory activity of pituitary gland.
    Hormones produced by it are two types –
    Releasing hormone (which stimulate secretion of pituitary hormone)
    Inhibiting hormone( which inhibit secretion of pituitary hormone)

    GnRH (gonadotrophins releasing hormone) from hypothalamus stimulate the pituitary gland to release gonadotrophins)
    Somatostatin from the hypothalamus inhibits the secretion of growth hormone from pituitary gland.
    Hormones secreted from the hypothalamus reach the pituitary gland through a portal circulation and regulate the anterior pituitary gland.
    Posterior pituitary is under the direct neural regulation of the hypothalamus.
    The pituitary gland :

    Pituitary gland is located in a bony cavity called sella tursica and is attached to the hypothalamus by a stalk.
    Anatomically pituitary gland divided into two parts –

    Adenohypophysis consists of two portions –
    Pars distalis
    Pars intermedia.

    Pars distalis commonly called anterior pituitary produce following hormones –
    Growth hormone (GH)
    Prolactin (PRL)
    Thyroid stimulating hormone (TSH)
    Adrenocorticotrophic hormone (ACTH)
    Luteinizing hormone (LH)
    Follicle stimulating hormone (FSH)

    Pars intermedia secrete one hormone called melanocyte stimulating hormone.
    Neurohypophysis (pars nervosa) also known as posterior pituitary store and release two hormone called Oxytocin and vasopressin, which are actually synthesized by the hypothalamus and are transported to neurohypophysis.
    Growth hormone :

    Regulate normal growth of the body.
    Over secretion of GH leads to overgrowth called gigantism.
    Hypos-secretion of GH leads to dwarfism.
    Prolactin :

    Regulates the growth of mammary gland.
    Stimulates formation of milk in the mammary gland.
    Thyroid stimulating hormone (TSH) :

    Stimulates the synthesis and secretion of thyroid hormone from thyroid gland.
    Adrenocorticotrophic hormone (ACTH) :

    Stimulates the synthesis and secretion of hormones from adrenal cortex called glucocorticoids and mineralocorticoids.
    Luteinizing hormone (LH) :

    In male LH stimulate the synthesis and secretion of hormone called androgens from testes.
    In female LH induces ovulation of fully mature follicles (Graafian follicle).
    Maintain the corpus luteum formed from the remnants of Graafian follicle after ovulation.
    Follicle stimulating hormone (FSH) :

    In male FSH along with androgen regulate spermatogenesis.
    FSH regulates the development of ovarian follicle.
    Melanocyte stimulating hormone :

    MSH acts on the melanocyte (melanin containing cell)
    Regulates the pigmentation of the skin.

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