Control And Coordination notes - Endocrine system in Animals , Coordination in plants

Need for Endocrine System/ Chemical communication

    Chemical communication by hormones is needed because of limitations of electrical

         communication:

(i) Electrical impulses have their limitations because they reach only those cells connected

      to the nervous tissue.

(ii) Also the nerve cells cannot generate & transmit impulses continuously. They need resting  

        time.

 Chemical communication also has a disadvantage : It is slower communication as compared to 

    electrical communication.

ENDOCRINE SYSTEM IN ANIMALS

Endocrine System helps in control and coordination through chemical compounds called HORMONES

˜ Hormones : These are the chemical messengers secreted by endocrine glands, in very small amounts, into the blood stream. They act on target tissues/organs usually away from their source.

They do not take part in the reaction & are not destroyed immediately.

 Hormones are secreted by- Endocrine glands

S. No.      Endocrine glands                      Exocrine glands

1.      Ducts absent                                         Ducts present

2.      Secrete hormones                                Secrete enzymes

3.     Secreted in blood                                 Secreted in ducts of glands

4. Situated away from the site of action      Situated near the site of action

 Some glands which act as both endocrine & exocrine

Gland                            Endocrine function                             Exocrine function

Pancreas             Produces insulin & Glucagon hormone        Produces digestive enzyme.                                  

                                         .                                                          (pancreatic amylase)

Testes                 Produces hormone Testosterone                   Produces male gametes

Ovaries               Produces hormone Oestrogen                       Produces female gametes                    

                                                                                                   (reproductive cells)

 Important Endocrine glands, the hormone they secrete & their function

                Refer to figure 7.7 page no. 124 of N.C.E.R.T Text book)

Endocrine gland        Hormone                                   Function

1. Pituitary gland      Growth hormone      Body growth, development of bones & muscles

                                                                                    (If excess- Gigantism)

                                                                                     (If less- Dwarfism)

2.Thyroid gland            Thyroxine             Regulates carbohydrate, protein & fat metabolism

                                                                                    ( If less- Goitre)

3.Pancreas                    Insulin and              Regulates blood sugar levels

                               Glucagon hormone               (if less diabetes is caused) 

 4.Testes                      Testosterone          Development of secondary male characters like

   in males                                                        deep voice, beard, etc.

5.Ovaries in                 Oestrogen           Development of secondary female characters like

   Females                                                mammary glands, menstrual cycle, maintenance

                                                                    of pregnancy.

6. Adrenal gland        Adrenaline         Regulation (increasing) blood pressure, heart beat, 

                                                                   carbohydrate metabolism (during emergency)

7. Pineal gland           Melatonin                           Biological Clock

8.  Thymus                 Thymosin                       Immunity of body

9. Parathyroid            Parathyroid                 Maintains calcium level in blood

       Gland                   hormone

Iodised Salt is Necessary Because :

Iodine mineral is essential part of thyronine hormone so it is important

that we must consume iodised salt as in turn it is essential for thyroid gland

as it controls carbohydrate, proteins and fat metabolism for best balance of

growth. Deficiency of iodine cause disease called goiter.

Diabetes

Cause : It is due to deficiency of Insulin hormone secreted by Pancreas

that is responsible to lower/control the blood sugar levels.

Treatment : Patients have to internally administer injections of insulin

hormone ® which helps in regulating blood-sugar level.

Feedback Mechanism

The excess or deficiency of hormones has a harmful effect on our body.

Feedback mechanism makes sure that hormones should be secreted in

precise quantities and at right time.

                             Coordination in Plants

    Plants also show movement in response to stimulus, So they also need coordination in different parts . In plants only chemical coordination is possible as they don’t have nervous tissue.

      Movements in plants is not due to contraction of muscles as they donot have muscular tissue. But in plants, cells change their shape by either gaining water (swelling of cell) or losing water (shrinking) thus making plant movements possible.

Movement in Plants

Two types of movements are shown by plants:

1.      Tropic movements                                                 2.  Nastic Movements

    Movement dependent                                                   Movement independent

      on growth                                                                            of growth

      (slow response)                                                     [immediate response                                                                                                                                          to stimulus]

                                                                                       eg. dropping of leaves

                                                                                             of Touch-me-not

                                                                                            plant on touching it

                                                                                               (Thigmonasty)

Tropic movements [growth dependent directional movements in response to stimulus]

These may be in direction of stimulus (+ve tropism) or away from stimulus (-ve tropism)

Phototropism                    Geotropism           Chemotropism                  Hydrotropism

Movement                        Movement                 Movement                    Movement

towards light                   towards gravity       towards Chemicals         towards water

( +ve in shoot)                ( +ve in roots)           (growth of pollen           (+ve in roots)

(-ve in root)                     (-ve in shoot)           tube towards ovule)

Refer to figure 7.4 & 7.5 page no. 121 of N.C.E.R.T Text book)

   

Plant Hormones (Phytohormones)

Are chemical compounds which help to coordinate growth, development and responses to the environment.

˜ Plant hormones : Main plant hormones are :

(a) Auxin : [Synthesized at shoot tip]

   Function : Helps in growth

     Phototropism : more growth of cells towards shady/ darker side.

 (b) Gibberellin : Helps in the growth of the stem

(c) Cytokinins : Promotes cell division

(d) Abscisic acid : Inhibits growth, cause wilting (falling) of leaves. (Stress hormone)

 e) Ethylene: Fruit ripening.

v Important diagrams-

1. Structure of neuron (nerve cell)   2. Reflex arc   3.Human brain    4.Endocrine glands .