Chapter 14 : CONTROL AND CO-ORDINATION IN ORGANISMS

1. Answer the following in short:
   
   1. Name a plant which shows thigmonasty.
   2. Give example of the movement of a plant which is caused by the loss of water.
   3. Name the two systems of control and co-ordination in higher animals.
   4. Name the three components of a nerve cell.
   5. Name the most important part of the human brain.
   6. State one function each of cerebellum and pons.
   7. Name one hormone secreted by the pituitary gland.
   8. Where are hormones synthesized in human body?
   9. Which gland secretes the growth hormone?
   10. Name the disease caused by the deficiency of insulin.
   11. What does CNS stand for?
   12. What is a stimulus?
   13. Mention some factors (stimuli) to which plants respond.
   14. Mention some plant hormones.
   15. What is sensory neuron?
   16. What is motor neuron?
   17. What is the function of cerebrospinal fluid?
   18. What does the fore-brain consist of?
   19. What does hind-brain consist of?
   20. Which gland is called the master galnd?
   21. What does a root do in response to gravity? What is this phenomenon known as?
   22. What does a stem do in response to gravity? What is this phenomenon known as?
   23. What does a stem do in response to light? What is this phenomenon known as?
   24. What does a root do in response to light? What is this phenomenon known as?
   
   ANS
   1. Mimosa
   2. Thigmonasty observed in plants like mimosa.
   3. (i) Nervous system (ii) Endocrine system.
   4. (i) Cell body (ii) Dendrite (iii) Axon
   5. Cerebrum
   6. • Cerebellum maintains body balance and posture.
      • Pons regulates the process of respiration.
   7. TSH (Thyroid Stimulating Hormone).
   8. Hormones are synthesized in endocrine glands like thyroid, pituitary, testes, etc.
   9. Pituitary gland.
   10. Diabetes
   11. Central Nervous System.
   12. Any environmental factor that affects a living organism by showing changes is called a stimulus.
   13. Light, touch, water, gravity and some chemicals.
   14. Auxin, Gibberellin, Cytokinin, Abscisic acid, Ethylene.
   15. Sensory neuron is a nerve cell which receives the stimuli from receptor and passes the message to the brain.
   16. Motor neuron is a nerve cell which receives information from brain, transmits it to the effector organ and stimulates it to respond.
   17. Cerebrospinal fluid acts as a cushion and protects brain from mechanical shock.
   18. Fore-brain consists of cerebrum (with olfactory lobes), thalamus and hypothalamus.
   19. Hind-brain consists of cerebellum, pons and medulla oblongata.
   20. Pituitary gland is called the master gland.
   21. Root grows in the direction of gravity. This phenomenon is known as positive geotropism.
   22. Stem grows in the direction opposite to gravity. This phenomenon is known as negative geotropism.
   23. Stem grows in the direction of light. This phenomenon is known as positive phototropism.
   24. Root grows in the direction opposite to light. This phenomenon is known as negative phototropism.
   
   
2. Give the scientific terms used to represent the following.
   1. Bending of a shoot towards light
   2. Growing of roots towards earth
   3. Growing of pollen tube towards ovule
   4. Bending of roots towards water
   5. Winding of tendril around a support
   
   ANS
   1. Phototropism
   2. Geotropism
   3. Chemotropism
   4. Hydrotropism
   5. Thigmotropism
   
   
3. What is spinal cord? What is its main function?
   ANS
   • Spinal cord is a cylindrical structure consisting of 31 pairs of nerves and it is the posterior extension of medulla oblongata.
   • Its main function is to conduct sensory information from organ to brain and motor information from brain to organ.
   • It also plays an important role in reflex action.
   
   
4. Write the functions of medulla oblongata.
   ANS
   • Medulla oblongata controls various involuntary activities like breathing, heart-beats, blood pressure. peristaltic movement of alimentary canal, etc.
   • Medulla oblongata also controls the centre of reflexes like coughing, sneezing, swallowing, vomiting and secretion of saliva.
   
   
5. Write a note on Tropism.
   ANS
   • TROPISM
     • The movement of curvature of plant organs in response to some external stimuli is known as tropism.
     • If the plant organ grows in the direction of the stimulus, then it is called positive tropism.
     • If the plant organ grows in the direction away from the stimulus, then it is called negative tropism.
     • The most common stimuli are: light, gravity, chemicals, water and touch.
   • TYPES OF TROPISM
     Depending upon the type of the stimulus, the types of tropism are: (i) phototropism (ii) geotropism (iii) chemotropism (iv) hydrotropism (v) thigmotropism.
   • PHOTOTROPISM
     • The movement of growth of a plant part in response to light is called phototropism.
     • Stem shows positive phototropism whereas roots show negative phototropism.
     
   • GEOTROPISM
     • The movement of growth of a plant part in response to gravity is called geotropism.
     • Roots show positive geotropism as they grow in the direction of gravity.
     • Stem shows negative geotropism as it grows in the direction opposite to gravity.
   • CHEMOTROPISM
     The movement of growth of a plant part in response to a chemical is called chemotropism. The growth of pollen tube towards ovule in a flower is an example of chemotropism.
   • HYDROTROPISM
     • The movement of growth of a plant part in response to water is called hydrotropism.
     • Roots of a plant grow towards water
     
   • THIGMOTROPISM
     The movement of growth of a plant part in response to touch is called thigmotropism. For example, tendrils of a plant.
   
   
   
   
   
6. Write a note on human brain with neat diagram.
   ANS
   • Human brain is a part of the central nervous system(CNS).
   • It is the main coordinating centre for all activities of the human body.
   • It is protected by a box called cranium in the skull and three membranes called meninges.
   • The space between meninges is filled with cerebrospinal fluid which acts as a cushion and protects the brain from mechanical shock.
   • The brain of an adult human weighs about 1350 gram.
   • The brain is divided into three regions: (i) Fore-brain (ii) Mid-brain (iii) Hind-brain.
     
     
     
     
   • FORE-BRAIN
     • Fore-brain consists of cerebrum (with olfactory lobe), thalamus and hypothalamus.
     • Cerebrum is the most complex and specialized part of the brain.
     • It consists of two cerebral hemispheres joined together by a band called corpus callosum.
     • It has sensory area to receive impulse from the sense organs and motor area to send impulse to muscles and effector organs.
     • The outer region of cerebral hemispheres is densely packed with nerve cells and is called cerebral cortex. It is highly convoluted so that its surface area gets increased.
     • Each cerebral hemisphere is divided into four lobes.
       
       
     • Frontal lobe controls both voluntary and involuntary activities including thought, speech and memory.
     • Parietal lobe possesses centres for sensation like smell, touch and temperature.
     • Occipital lobe has centre for visual reception.
     • Temporal lobe controls activities of auditory recepation.
     • Thalamus is located at the centre of the fore-brain. All sensory information reaching cerebrum passes through thalamus.
     • Hypothalamus lies below thalamus and it controls and regulates blood pressure, hunger, body temperature and thirst.
   • MID-BRAIN
     Mid-brain possesses the regions for controlling functions of eyes (visual reception) and ears (auditory reception). Corpora quadrigemina is a part of mid-brain. Mid-brain connects fore-brain and hind-brain.
   • HIND-BRAIN
     • Hind-brain consists of three regions: Cerebellumon the dorsal side and pons and medulla oblongata on the ventral side.
     • Cerebellum maintains balance and posture of the body. It coordinates movements like dancing, walking and riding a bicycle.
     • Pons regulates the process of respiration.
     • Medulla oblongata controls involuntary activities like breathing, heartbeats, blood pressure, peristaltic movement of alimentary canal, etc.
     • Medulla oblongata also controls the centres of reflexes like coughing, sneezing, vomiting, secretion of saliva, etc.
   
   
7. Write a brief note on spinal cord.
   ANS
   • Spinal cord is a cylindrical structure and it is the posterior extension of medulla oblongata.
   • It is protected by three membranes called meninges.
   • Its central part consists of grey matter in 'H' shape. The grey matter contains non-medullated nerve fibres and neurons possessing short processes.
   • White matter forms the periphery of spinal cord. White matter contains medullated nerve fibres and neurons possessing long processes.
   • Cerebrospinal fluid is present in the central canal of spinal cord.
   • 31 pairs of nerves arise from spinal cord.
   • Bundles of nerves run ascending and descending in tracts and link the spinal cord with brain.
   • Ascending tracts conduct sensory information from spinal cord to brain and descending tracts conduct motor information from brain to spinal cord.
   • Spinal cord plays an important role in reflex action.
   
   
8. What is autonomous nervous system? What is its function?
   ANS
   • Autonomous nervous system means 'self-governing' nervous system.
   • It controls the activity of body organs like heart, blood vessels, glands, uterus, etc., automatically (i.e. without our thinking and without the awareness of brain).
   • Autonomous nervous system is of two types: (i) Sympathetic (ii) Parasympathetic.
   • The involuntary actions of the body are controlled and regulated by the coordination of these two systems.
   • The effects of sympathetic and parasympathetic nervous systems are complementary and contradictory to each other.
   • For example, if the sympathetic system increases the heart-beats abnormally, the parasympathetic system decreases it and brings it back to normal.
   
   
9. Mention properties (characteristics) of hormones.
   ANS
   • Each hormone is produced by a specific kind of cells.
   • Generally, the hormones are not effective at the site of their synthesis (i.e. the target area is different than origin).
   • They are directly poured into the blood and carried by blood to the specific organ.
   • Their influence may be stimulatory or regulatory. Thus, they are 'regulatory chemicals'.
   • Hormones are used up in producing their regulatory effect.
   • They are chemical messengers in the form of peptides, steroids and biogenic amines.
   
   
10. What is voluntary nervous system? Explain its working with an example.
    ANS
    • Actions which need thinking and which we perform knowingly are called voluntary actions.For example, speaking to a friend, putting on shoes, reading a book, drawing a picture, etc. are called voluntary actions.
    • The system which helps us do voluntary actions consciously under the control of brain is called voluntary nervous system.
    • Suppose we have to go somewhere by plane. We first choose a flight, book out seat, and then at the time of journey we leave for airport some time before departure of plane and after reaching airport we follow certain procedure and then board the flight. Voluntary nervous system is directly in this sequence of actions. When we leave for airport we frequently see our watch and if need be we speed up our vehicle so that we do not miss the plane.
    • Our eyes see the time in watch and that information is sent to brain through sensory nerves. The brain on analysis realizes the risk of missing the flight so it decides that we should speed up.
    • The brain gives instructions to muscles of our legs through motor nerves and the muscles accordingly press accelerator to uncrease the speed of our vehicle.
    • This is an example of how the voluntary nervous system works.
    
    
11. Write a detailed note on endocrine glands of human body.
    ANS
    • GENERAL
      • Endocrine glands situated in different parts of the body form the endocrine system and play an important role in coordination.
      • These are ductless glands which secrete specific hormones into the blood stream.
      • The main endocrine glands are hypothalamus, pituitary, thyroid, parathyroid, pancreas, adrenal, testis and ovary.
    • HYPOTHALAMUS
      • Hypothalamus is located in brain below the thalamus and above the pituitary gland.
      • Its neurosecretory cells produce releasing hormones (RH) that stimulate the anterior pituitary gland to secrete specific hormones.
      • TSH releasing hormone activates pituitary gland to release TSH (Thyroid Stimulating Hormone).
      • GH releasing hormone activates pituitary gland to release growth hormone (GH).
      • ACTH releasing hormone activates pituitary gland to release Adrino Cortico Trophic Hormone (ACTH).
      • Gonadotrophic releasing hormone activates pituitary gland to release FSH (Follicle Stimulating Hormone) and LH (Leutenizing hormone).
      • Hypothalamus also releases two inhibitory hormones: (i) GH inhibitory factor inhibits the release of GH. (ii) PIF (Prolactin Inhibitor Factor) inhibits the release of prolactin from pituitary gland.
    • PITUITARY
      • Pituitary gland is located just below the hypothalamus.
      • It is divided into three lobes: (i) anterior lobe (ii) intermediate lobe (iii) posterior lobe.
      • Anterior pituitary lobe releases TSH, ACTH, FSH, LH, GH and prolactin. Secretion of all these hormones is controlled by hypothalamus.
      • Intermediate pituitary lobe secretes MSH (Melanocyte Stimulating Hormone).
      • Posterior pituitary lobe secretes vasopressin and oxytocin.
      • Vasopressin is anti-diuretic hormone (ADH) and it stimulates re-absorption of water and thus controls the loss of water through urine. It also acts as vasoconstrictor and increases arterial blood pressure.
      • Oxytocin (in female) causes contraction of uterine muscles during child birth and ejection of milk from mammary glands.
      • Since pituitary gland controls the secretion of hormones from other glands it is called the master gland.
    • PANCREAS
      • Pancreas lies just below stomach.
      • It secretes hormone insulin which lowers the sugar level in blood.
      • Deficiency of insulin results in large amount of sugar in blood and urine. This disorder is called diabetes.
      • Diabetes, if not controlled, causes many harmful effects.
      • A diabetic person should consume less amount of sugar.
      • To control diabetes, one should control diet, do physical exercise, reduce body weight and take necessary medicines and insulin regularly.
    • THYROID
      Thyroid gland is attached to the wind pipe and it secretes hormone thyroxine which contains iodine.
      • Thyroxine controls the metabolic rate of carbohydrates, proteins and fat.
      • Deficiency of iodine in our diet results in hypothyroidism (deficiency of thyroxine) and enlargement of thyroid gland. This disorder is called goitre.
      • Hyperthyroidism (over-secretion of thyroxine) is called exophthalmic goitre which results in bulging of the eyeball.
      • Deficiency of iodine can be set off by consuming iodized salt (salt containing small amount of iodine).
    • PARATHYROID
      Parathyroid glands are four small glands embedded in the thyroid gland. These glands secrete parahormone which regulates calcium and phosphate level in blood.
    • ADRENAL
      • There are two adrenal glands.
      • Adrenal gland is small, conical in shape and composed of two distinct regions: (i) outer cortex (ii) inner medulla.
      • Adrenal cortex secretes three types of steroid hormones.
      • Mineral corticoids regulate balance of water and ions like Na⁺, K⁺ and Cl^- in our body.
      • Glucocorticoids stimulate metabolism of carbohydrates, proteins and fats.
      • Sex corticoids induce secondary sexual characters.
      • Adrenal medulla secretes adrenaline and non-adrenaline.
      • Adrenaline is called 'fight or flight' hormone.
      • Adrenal glands are also called glands of 'emergency'.
    • TESTIS
      • Testes are in pair and they produce male sex hormone testosterone and sperms.
      • Testosterone controls the development of sex organs in male.
      • The secondary sexual characters like deeper voice, beard and moustache are induced by testosterone.
    • OVARY
      • Ovaries produce female sex hormones estrogen and progesterone.
      • Estrogen controls development of female sex organs and secondary sexual characters like feminine voice, soft skin and mammary glands.
      • Progesterone controls changes in uterus during menstrual cycle and regulates the production of ova in ovaries.
    
    
12. Explain: Reflex Action.
    ANS
    • Reflex action is a rapid automatic response without thinking like pulling our hand away on pricking a pin or unknowingly touching a very hot object.
    • A knee-jerk, coughing, yawning, blinking of eyes, sneezing and movement of diaphragm, etc. are examples of reflex action.
    • Reflex action is an automatic process and is an unconscious and involuntary response of the effectors to a stimulus.
      
    • REFLEX ARC: The nerve impulse pathway in a reflex action is called reflex arc.
    • Suppose we touch a hot plate. We immediately pull our hand away without thinking. This happens because the thermoreceptors in our hand sense the heat. An impulse triggered by the receptor in sensory neuron transmits to the spinal cord. Spinal cord transmits the impulse to motor neuron which sends it to the muscle which contracts and pulls the hand away from the hot plate. The pathway of transmission of impulse ia called reflex arc.
    • Reflex action is performed by the spinal cord without the knowledge of brain.
    
    
13. Describe disorders of growth hormone (GH).
    ANS
    • Dwarfism, gigantism and acromegaly are disorders of growth hormone.
    • Hypo or under-secretion of growth hormone during childhood leads to dwarfism.
    • Hyper or over-secretion of growth hormone during childhood leads to gigantism (giant height).
    • Too much secretion of growth hormone during adolescence causes enlargement of certain body parts like hands, feet and jaws and gives appearance like a gorilla.
    
    
14. Distinguish between tropism and nastism (or tropic movement and nastic movement).
    ANS
    
    
    
15. How does our body respond when adrenaline is secreted in large amounts into blood?
    ANS
    • Adrenaline is secreted by adrenal gland in small amounts all the time but in large amount if a person is in critical (or frightening) situation.
    • Secretion of adrenaline in large amounts increases the energy level of the body suddenly and the person either fights the situation or runs away from it (flight).
    • Thus, adrenal is 'fight or flight' gland or 'gland of emergency'.
    
    
16. Explain structure of a nerve cell (neuron) with diagram.
    ANS
    • Nerve cell is the structural and functional unit of the nervous system.
    • Cell body, dendrites and axon are the three components of a nerve cell.
    • The cell body contains cytoplasm and nucleus.
    • The short fibres extending from the cell body are called dendrites.
    • The long fibre extending from the cell body is called axon.
    • An insulating sheath of myelin around axon is made of fat and protein and it protects axon.
      
      
    • The dendrite receives message from receptors, sets off a chemical reaction and creates an electrical impulse called nerve impulse.
    • The message is passed to the cell body and then to axon. Axon passes the message to another nerve cell through a junction.
    • At the junction, there is a small gap between two nerve cells. This gap is called synapse.
    • The nerve cell acquires a message which travels as an electric impulse. This impulse is converted into a chemical signal for onward transmission.
    
    
17. 
    ANS