Chapter-7
Control Acid Coordination
• All the living organisms respond and react to changes in the environment.
• The changes in the environment to which the organisms respond and react are called stimuli such as light, heat, cold, sound, smell, touch etc.
• Both plants and animals respond to stimuli but in a different manner.
Control and Coordination in Animals :
It is bought about in all animals with the help to two main systems :
(a) Nervous system
(b) Endocrine system
NERVOUS SYSTEM
• Control and coordination are provided by nervous and muscular tissues.
• Nervous tissue is made up of an organized network of nerve cells or neurons, and is specialized for conducting information via electrical impulses from one part of the body to another.
Receptors : Are specialized tips of some nerve cells detect the information from the environment. These receptos are located in our sense organs.
| (a) Ear : | • Phonoreceptors |
| • Hearing | |
| • Balance of the body | |
| (b) Eyes : | • Photorecetors |
| • Seeing | |
| (c) Skin : | • Thermoreceptos |
| • Heat and cold | |
| • Touch | |
| (d) Nose : | • Olfactory receptos |
| • Smell detection | |
| (e) Tongue : | • Gustatory receptos |
| • Taste detection |
It is the structural and functional unit of nervous system
Parts of Neuron :
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(a) Dendrite : Acquries information.
(b) Cell body : Acquried information travels as an electrical impulse.
(c) Axon : Longest fibre on the cell is called axon. It transmits electrical impulse from cell body to dendrite of next neuron.
Synapse : It is the gap between the nerve ending of one neuron and dendrite of the other neuron. Here electrical signal is converted into chemical signal for onward transmission.
REFLEX ACTION
Reflex action is quickm sudden and immediate response of the body to a stimulus.
E.g., Knee jerkm withdrawal of hand on touching hot object.
Reflex are : The pathway through which nerve impulses pass during reflex action is called reflex are :
Response : Response are of three main types :
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(a) Voluntary : Cantrolled by fore brain. E.g., talking, writing.
(b) Involuntary : Controlled by mid hind brain. E.g., heartbeat, vomiting, respiration.
(c) Reflex action : Controlled by spinal cord. E.g., withdrawal of hand on touching a hot object.
Need of Reflex Actions : In some situations such as touching a hot object, pinching etc. we need to act quickly, otherwise our body would be harmed. Here response is generated from spinal cord instead of brain.
HUMAN BRAIN
Brain is the main coordinating centre of the body. It has three major parts:
(a) Force-brain (b) Mid-brain (c) Hind-brain
(a) Fore-brain : It is the most complex or specialized part of the brain. It consists of cerebrum.
Functions :
(i) Thinking part of the brain.
(ii) Control the voluntary actions.
(iii) Store information (Memory).
(iv) Receives sensory impulses from various parts of the body and integrate it.
(v) Centre associated with hunger.
(b) Mid-brain :
Controls involuntary actions such as:
• Change in pupil size.
• Reflex movements of head, neck and trunk.
(c) Hind-brain : It has three parts :
(i) Cerebellum : Controls posture and balance. Precision of voluntary actions e.g., picking pen.
(ii) Medualla : Controls involuntary actions e.g., blood pressure, salivation, vomiting.
(iii) Pons : Involuntary actions, regulation of respiration.
Protection of Brain and Spinal Cord
(a) Brain : Brain is protected by a fluid filled balloon which acts as shock absorber and is enclosed in cranium (skill or brain box).
(b) Spinal Cord : Spinal cord is enclosed in vertebral column.
Limitations of Electric Communication/ Nervous System :
(a) Electric impulse will reach only to these cells that are connected by nervous tissue.
(b) After generation adn transmission of an electrical impulse, the cell takes some time to reset its mechanism before transmitting another impulse. So cells continually create and transmit impulse.
(c) Plants do not have any nervous system.
Chemical Communication : To overcome the limitations of electric communication.
COORDINATION IN PLANTS
Movements in plants :-
(i) Independent of growth
(ii) Dependent on growth
(i) Independent of growth : Immediate response to stimulus.
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• Plants use electrical-chemical means to convey information from cell to cell.
• For mevement to happen, cells change their shape by changing the amount of water in them, resulting in swelling or shrinking of cells.
E.g., Drooping of leaves of 'Touch-me-not' plant on touching it.
(ii) Dependent on growth : These movements are tropic movements i.e., directional movements in response to stimulus.
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• Tendrills : The part of tendril away from the object grows more rapidly as compared to the part near the object. This causes circulating of tendril around the object.
• Phototropisum : Movements towards light.
• Geotropism : Movements towards/ away from gravity.
• Chemotropism : Growth of pollen tube towards ovule.
• Hydrotropism : Movements towards water.
Plant Hormones : Are chemical compounds which helps to coordinate growth, development and response to the environment.
Main Plant Hormones are :
| (a) Auxin : | • Synthesized at shoot tip |
| • Helps the cells to grow longer | |
| • Involved in phototropism | |
| (b) Gibberellin : | • Helps in the growth of the stem |
| (c) Cytokinins : | • Promotes cell division |
| • Present in greater concentration in fruits and seeds | |
| (d) Abscisic Acid : | • Inhibits growth |
| • Cause wilting of leaves | |
| • Stress hormone |
Hormones in Animals :
Hormones : Hormones are the chemical substances which coordinate the activities of living organisms and also their growth.
Endocrine glands : These glands secrete their product (hormone) into the blood.
Endocrine Gland, Hormones and their Functions
| S. No. | Hormone | Endocrine Gland | Location | Functions |
|---|---|---|---|---|
| 1. | Thyroxine | Thyroid | Neck/Throat region | Regulation of metabolism of carbohydrates, fats and proteins. |
| 2. | Growth hormone | Pituitary (master gland) | Mid brain | Regulates growth and development. |
| 3. | Adrenaline | Adrenal | Above both kidneys | Regulation (increasing) of blood pressure, heart beat, carbohydrates metabolism (during emergency) |
| 4. | Insulin | Pancreas | Below stomach | Reduced and regulates blood sugar level |
| 5. Sex Hormone | (a) Testosteron in Males
(b) Estrogen in Females |
Testis
Ovaries |
Genital lower abdomen area |
Change associated with puberty (Sexual maturity) |
| 6. | Releasing Hormone | Hypothalmus | Mid brain | Stimulates pituitary gland to release hormones |
Iodised salt is necessary because Iodine mineral is essential part of thyroxine hormone secreted secreted by thyroid gland. Thyroxine regulates metabolism of carbohydrates, fats and proteins. So, we must consumer iodised salt which is necessary for proper working of thyroid gland. It's deficiency causes a disease called goiter (Swollen neck).
Diabetes
Disease in which blood sugar level increase.
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Cause : Due to the deficiency of insulin hormone secreted by pancreas that is responsible to control blood sugar levels.
Treatment : Injections of insulin hormones.
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The excess or deficiency of hormones has a harmful effect on our body.
Feedback mechanism makes sure that hormones should be secreted in precise quantity and at right time.
E.g., Feedback mechanism to control the sugar level in blood is as follows :
