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Class X - science: Control and Coordination
One Word Answer Questions:
Q) Which part of the brain maintains posture and equilibrium of the body?
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Q) Give an example of a plant hormone that promotes growth.
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Q) The substance that triggers the fall of mature leaves and fruits from plants is due to?
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Q) Iodine is necessary for the synthesis of which hormone?
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Q) The hormone which increases the fertility in males is called?
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Q) What type of organisms respond to stimuli?
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Q) What is the Abbreviation of PNS?
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Q) What is the abbreviation of CNS?
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Short Answer Questions:
Q) What is the role of the brain in reflex action?
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Q) What are plant hormones?
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Q) What happens at the synapse between two neurons?
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Q) How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
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Q) Name the hormone secreted by human testes. State its functions.
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Q) Write the name and the functions of any two parts of the hind brain.
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Q) How does our body respond when adrenaline is secreted into the blood?
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Q) What is the Adrenalin hormone?
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Q) What is Coordination?
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Q) What is myelin sheath?
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Q) What is the synapse?
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Q) Explain about Autonomus nervous system?
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Long Answer Questions:
Q) Differentiate between tropic and nastic movements in plants. Give one example of each.
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Q) What is reflex action? Describe the steps involved in reflex action?
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Q) Name a hormone secreted by :a) pancreas b)pituitary c)thyroid. state one function of each of the hormone.
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Q) Explain about Central Nervous System?
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Q) Explain about Peripheral nervous system?
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Q) Explain about Functions of the various parts of the brain?
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Q) Explain about Structure of nerve cell?
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A living being does not live in isolation. It has to constantly interact with its external environment and has to respond properly for its survival. For example;when a hungry lion spots a deer,the lion has to quickly make a move so that it can have its food. On the other hand,the deer needs to quickly make a move to run for its life. The responses which a living being makes in relation to external stimuli are controlled and coordinated by a system; especially in complex animals.

Nervous System

"Nervous system is the organ system present in the animals to control and coordinate different activities of the body".

  • Nervous system comprises of the brain, the spinal cord, and a huge network of nerves that are spread throughout the body.
  • The nervous system is responsible for sending, receiving and processing messages in the form of chemical signals called as impulses.
  • A neuron is the basic unit of the nervous system. Each neuron consists of three parts, namely, the cell body or cyton, branched projections called the dendrites, and the long process from the cell body, called the axon.
  • Synapse is a gap between two neurons.Nerves are thread like structures emerging out of the brain and spinal cord.
  • Nerves branch out to all parts of the body and are responsible of carrying messages in the body.
  1. Cyton or cell body: The cell body or cyton is somewhat star-shaped; with many hair-like structures protruding out of the margin. These hair-like structures are called dendrites. Dendrites receive the nerve impulses.
  2. Axon:This is the tail of the neuron. It ends in several hair-like structures; called axon terminals. The axon terminals relay nerve impulses.
  3. Myelin Sheath:There is an insulator cover around the axon. This is called myelin sheath. The myelin sheath insulates the axon against nerve impulses from the surroundings.
Types of nerves:

Different types of nerves present are sensory,motor and mixed.

  • Sensory nerves send messages from the sense organs to the brain or spinal cord.
  • Motor nerves carry messages back from the brain or spinal cord to all the muscles and glands in the body.
  • Mixed nerves carry both sensory and motor nerves.
Reflex action and Reflex arc:
Reflex action:

Reflex action is a special case of involuntary movement in voluntary organs. When a voluntary organ is in the vicinity of a sudden danger, it is immediately pulled away from the danger to save itself.

Example:When your hand touches a very hot electric iron, you move away your hand in a jerk. All of this happens in flash and your hand is saved from the imminent injury. This is an example of reflex action.

Reflex Arc:

The path through which nerves signals involved in a reflex action travel is called the reflex arc. The following flow chart shows the flow of signal in a reflex arc.
Receptor⇒Sensory Neuron⇒Relay neuron⇒Motor neuron⇒Effector(muscle)

  • The receptor is the organ which comes in the danger zone. The sensory neurons pick signals from the receptor and send them to the relay neuron. The relay neuron is present in the spinal cord.
  • The spinal cord sends signals to the effector through the motor neuron. The effector comes in action moves the receptor away from the danger.
  • The reflex arc passes at the level of the spinal cord and the signals involved in reflex action do not travel up to the brain. This is important because sending signals to the brain would involve more time.
  • Although every action is ultimately controlled by the brain, the reflex action is mainly controlled at the level of spinal cord.
Reflex Action
Nervous system in Humans

The nervous system in humans can be divided into two main parts:

  • The central nervous system and
  • The peripheral nervous system.
  • The peripheral nervous system can be further divided into the somatic nervous system and the autonomous nervous system.

    Central Nervous System:

    The central nervous system is composed of the brain and the spinal cord. The brain controls all the functions in the human body. The spinal cord works as the relay channel for signals between the brain and the peripheral nervous system.

    Peripheral Nervous System:

    The peripheral nervous system is composed of the cranial nerves and spinal nerves. There are 12 pairs of cranial nerves. The cranial nerves come out of the brain and go to the organs in the head region. There are 31 pairs of spinal nerves. The spinal nerves come out of the spinal cord and go to the organs which are below the head region.

    Autonomous Nervous System:

    The autonomous nervous system is composed of a chain of nerve ganglion which runs along the spinal cord. It controls all the involuntary actions in the human body. The autonomous nervous system can be divided into two parts:

    Sympathetic Nervous System:

    This part of the autonomous nervous system heightens the activity of an organ as per the need. For example; during running, there is an increased demand for oxygen by the body. This is fulfilled by an increased breathing rate and increased heart rate. The sympathetic nervous system works to increase the breathing rate and the heart rate; in this case.

    Parasympathetic Nervous System:

    This part of the autonomous nervous system slows the down the activity of an organ and thus has a calming effect. During sleep, the breathing rate slows down and so does the heart rate. This is facilitated by the parasympathetic nervous system. It can be said that the parasympathetic nervous system helps in conservation of energy.

    Human Brain
    • Human brain is a highly complex organ; which is mainly composed of the nervous tissue.
    • The tissues are highly folded to accommodate a larger surface area in less space.
    • The brain is covered by a three layered system of membranes; called meninges. Cerebrospinal fluid is filled between the meninges.
    • The CSF provides cushion to the brain against mechanical shocks.
    • Furthermore, the brain is housed inside the skull for optimum protection. The human brain can be divided into three regions, viz. forebrain, midbrain and hindbrain.
    Human Brain

    Parts of Human Brain

    • Forebrain:It is composed of the cerebrum.
    • Midbrain:It is composed of the hypothalamus.
    • Hindbrain:It is composed of the cerebellum, pons and medulla oblongata.

    The cerebrum is the largest part in the human brain. It is divided into two hemispheres; called cerebral hemispheres.

    Functions of cerebrum:
    • The cerebrum controls the voluntary motor actions.
    • It is the site of sensory perceptions; like tactile and auditory perceptions.
    • It is the seat of learning and memory.

    The hypothalamus lies at the base of the cerebrum. It controls sleep and wake cycle (circadian rhythm) of the body. It also controls the urges for eating and drinking.


    Cerebellum lies below the cerebrum and at the back of the whole structure. It coordinates the motor functions. When you are riding your bicycle; the perfect coordination between your pedaling and steering control is achieved by the cerebellum.


    Medulla forms the brain stem; along with the pons. It lies at the base of the brain and continues into the spinal cord. Medulla controls various involuntary functions; like hear beat, respiration, etc.

    Protection of tissues in the brain:

    Brain is a delicate organ which needs proper protection, and our body is designed so that the brain sits inside a bony box called skull. Inside the skull, the brain is contained in a fluid-filled balloon which provides further shock absorption. If you run your hand down the middle of your back, you will feel a hard, bumpy structure. This is the vertebral column or backbone which protects the spinal cord.

    Muscular Movements and Nervous Control:
    • Muscle tissues have special filaments called actin and myosin.
    • When a muscle receives a nerve signal; a series of events is triggered in the muscle. Calcium ions enter the muscle cells.
    • It results in actin and myosin filaments sliding towards each other and that is how a muscle contracts. Contraction in a muscle brings movement in the related organ.
Coordination In Plants

Unlike animals, plants do not have a nervous system. Plants use chemical means for control and coordination.

Movement due to growth:

Many plant hormones are responsible for various kinds of movements in plants.
Movements in plants can be divided into two main types:

  • Tropic movement and
  • Nastic movement.
Tropic Movement

"The movements which are in a particular direction in relation to the stimulus are called tropic movements".
Tropic movements happen as a result of growth of a plant part in a particular direction. There are five types of tropic movements:

  1. Geotropic
  2. Phototropic
  3. Hydrotropic
  4. Thigmotropic
  5. Chemotropic
  1. Geotropic Movement:"The growth in a plant part in response to the gravity is called geotropic movement". Roots usually show positive geotropic movement, i.e. they grow in the direction of the gravity. Stems usually show negative geotropic movement.
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  3. Phototropic Movement:"The growth in a plant part in response to light is called phototropic movement". Stems usually show positive phototropic movement, while roots usually show negative phototropic movement. If a plant is kept in a container in which no sunlight reaches and a hole in the container allows some sunlight; the stem finally grows in the direction of the sunlight. This happens because of a higher rate of cell division in the part of stem which is away from the sunlight. As a result, the stem bends towards the light. The heightened rate of cell division is attained by increased secretion of the plant hormone auxin in the part which is away from sunlight.

  4. Hydrotropic Movement:"When roots grow in the soil, they usually grow towards the nearest source of water. This shows a positive hydrotropic movement".
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  6. Thigmotropic Movement:"The growth in a plant part in response to touch is called thigmotropic movement".Such movements are seen in tendrils of climbers. The tendril grows in a way so as it can coil around a support. The differential rate of cell division in different parts of the tendril happens due to action of auxin.
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  8. Chemotropism:It is a growth movement of a plant part in response to chemical stimulus. e.g. Growth of pollen tubes towards ovules.
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    Response to stimulus:
    Nastic Movement:

    "The movements which do not depend on the direction from the stimulus acts are called nastic movement".
    These are exactly the movement of plant parts.

    • These movements are independent of growth.
    • Plant cells must change their shape for this movement to happen.
    • The movement in plants occurs in the direction opposite to the stimulus.
    • When someone touches the leaves of mimosa,the leaves droop.
    • The drooping is independent of the direction from which the leaves are touched.
    • Such movements usually happen because of changing water balance in the cells.
    • When leaves of mimosa are touched, the cells in the leaves lose water and become flaccid; resulting in drooping of leaves.
    The Sensitive Plant
    Plant hormones

    Plants have various hormones, which help to coordinate growth,development and response to the environment.
    "Hormones are the chemical compounds released by stimulated cells". Hormones diffuse all around the cell. Different hormones secreted by the plant are auxins,gibberellins,cytokinins,abscisic acid.

    • Auxins are the hormones synthesised at the tip of the stem.These help the plant in growth by cell elongation.
    • Gibberellins are hormones that help in the growth of the stem,seed germination,bolting,and flowering.
    • Cytokinins are hormones present in the areas of rapid cell division, such as fruits and seeds.They also promote the opening of the stomata.
    • Abscisic acid is a hormone that inhibits the growth in various parts.It is also responsible for the closure of stomata.
Hormones In Animals
Endocrine System:
  • The endocrine system is composed of several endocrine glands.A ductless gland is called endocrine gland.
  • Endocrine gland secretes its product directly into the bloodstream.Hormones are produced in the endocrine glands.
  • Hormone is mainly composed of protein. Hormones assist the nervous system in control and coordination.
  • Nerves do not reach to every nook and corner of the body and hence hormones are needed to affect control and coordination in those parts.
  • Moreover, unlike nervous control; hormonal control is somewhat slower.
Endocrine Glands:

Different types of endocrine glands present in our body are the pituitary gland,the pineal gland,the hypothalamus, the thyroid, the parathyroid,the thymus,the adrenal gland, the pancreas,the testes and the ovary.

Let us discuss some of these glands

Endocrine GlandLocationHormones ProducedFunctions
Pituitary gland(Also known as the master gland)At the base of brainGrowth hormone (GH), thyroid stimulating hormone (TSH), Follicle stimulating hormone (FSH)GH stimulates growth, TSH stimulates functioning of thyroid gland, FSH stimulates the follicles during ovulation.
Thyroid GlandNeckthyroxineControls general metabolism and growth in the body
Adrenal glandAbove KidneysAdrenalinPrepares the body for emergency situations and hence is also called'Fight and flight'hormone.
PancreasNear StomachInsulinControls blood sugar level
Testis(Male)In ScrotumTestosteroneSperm production, development of secondary sexual characters during puberty
Ovary (Female)Near UterusOestrogenEgg production, development of secondary sexual characters during puberty

Endocrine Glands In Human Beings:

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