Class 10th Reference notes (control and coordination)

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Control and Coordination

Importance of control and coordination

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.

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Nervous System

The nervous system is composed of specialized tissues; called nervous tissue. The nerve cell or neuron is the functional unit of the nervous system. It is the nervous system which is mainly responsible for control and coordination in complex animals.

Neuron: Neuron is a highly specialized cell which is responsible for transmission of nerve impulses. The neuron consists of the following parts:

Fig: Neuron

a.    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.

b.    Axon: This is the tail of the neuron. It ends in several hair-like structures; called axon terminals. The axon terminals relay nerve impulses.

c.    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 Neuron

a.    Sensory neuron: These neurons receive signals from a sense organ.

b.    Motor neuron: These neurons send signals to a muscle or a gland.

c.    Association neuron: These neurons relay the signals between sensory neuron and motor neuron.

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Nervous System in Humans

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

a.    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.

b.    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.

Control and Coordination

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.

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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.

Some main structures of the human brain are explained below.

Cerebrum: 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.

Hypothalamus: 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: 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: 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.

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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. For 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 via 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.

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.

Control and Coordination

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.

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Endocrine gland	Location	Hormones Produced	Functions
Pituitary gland (Also known as the master gland)	At the base of brain	Growth 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 Gland	Neck	Thyroxine	Controls general metabolism and growth in the body.
Adrenal gland	Above kidneys	Adrenalin	Prepares the body for emergency situations and hence is also called ‘Fight and flight’ hormone.
Pancreas	Near stomach	Insulin	Controls blood sugar level
Testis (male)	In scrotum	Testosterone	Sperm production, development of secondary sexual characters during puberty.
Ovary (female)	Near uterus	Oestrogen	Egg production, development of secondary sexual characters during puberty.

Coordination in Plants:

Unlike animals, plants do not have a nervous system. Plants use chemical means for control and coordination. Many plant hormones are responsible for various kinds of movements in plants.

Movements in plants can be divided into two main types, viz. 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 four types of tropic movements, viz. geotropic, phototropic, hydrotropic and thigmotropic.

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a.    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.

b.    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.

c.    Hydrotropic Movement: When roots grow in the soil, they usually grow towards the nearest source of water. This shows a positive hydrotrophic movement.

d.    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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Nastic Movement:

The movements which do not depend on the direction from the stimulus acts are called nastic movement. For example; 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.

Some Plant Hormones: Auxin, gibberellins and cytokinin promote growth in plant parts. Abscissic acid inhibits growth in a particular plant part.

Test Your Knowledge

1.    Which hormone prepares a lion when it is about to attack a deer?
Answer: Adrenaline

2.    Which hormone plays an important role in ovulation?
Answer: Oestrogen

Control and Coordination

Solution NCERT Questions

Which signals will get disrupted in case of a spinal cord injury?

Answer: The spinal nerves go to the organs which are below the head region. Moreover, the autonomous nervous system is also connected to the spinal cord. In case of spinal cord injury, communication between the spinal nerves and the brain would be disturbed. Similarly, the communication between the autonomous nervous system and brain would also be disturbed; in case of spinal cord injury.

What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Answer: Receptors provide information about the external environment so that the brain can instruct a related to organ to take necessary action. Receptors play an important role in our survival. Let us take the example of a person with hearing impairment. Certain ordinary task would be very difficult for that person. For example; while walking on the road, the person needs to hear the sound of vehicles moving near him. Without hearing those sounds, he would not be in a position to move safely on the road.

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1.    Which of the following is a plant hormone?

a.    Insulin

b.    Thyroxin

c.    Oestrogen

d.    Cytokinin
Answer: (d) Ctyokinin

2.    The gap between two neurons is called a

a.    Dendrite

b.    Synapse

c.    Axon

d.    Impulse
Answer: (b) Synapse

3.    The brain is responsible for

a.    Thinking

b.    Regulating the heart beat

c.    Balancing the body

d.    All of the above
Answer: (d) All of the above

4.    Draw the structure of a neuron and explain its function.
Answer: Function of Neuron: Neuron transmits the nerve impulses.

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1.    How does phototropism occur in plants?
Answer: Concentration of auxin changes in a particular plant part, in response to the direction of light. For example; in a stem, concentration of auxin increases in those parts which are away from light. This increases cell division in that part and thus the stem bends towards light. That is how phototropism occurs in plants.

2.    How does chemical coordination occur in plants?
Answer: Plant hormones play their roles in chemical coordination. Most of the plant hormones promote growth in certain plant parts, e.g. auxin, gibberellins and cytokinin. Abscissic acid is a plant hormone which inhibits growth. Shedding of leaves or ripe fruits is facilitated by abscissic acid.

3.    What is the need for a system of control and coordination in an organism?
Answer: 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.

4.    How are involuntary actions and reflex actions different from each other?
Answer: Involuntary actions are part of routine activities, while reflex actions are in response to a sudden danger. Moreover, involuntary actions happen in involuntary organs, while reflex action happens in a voluntary organ.

5.    Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Answer: Nervous control is fast, while hormonal control is slow. Nervous control is facilitated by neurotransmitters, while hormonal control is facilitated by hormones.

6.    What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Answer: The movement in a sensitive plant is facilitated by chemical control, while the movement in our legs is facilitated by nervous control.

1.    Which of the following statements is correct about receptors?

a.    Gustatory receptors detect taste while olfactory receptors detect smell

b.    Both gustatory and olfactory receptors detect smell

c.    Auditory receptors detect smell and olfactory receptors detect taste

d.    Olfactory receptors detect taste and gustatory receptors smell
Answer: (a) Gustatory receptors detect taste while olfactory receptors detect smell

2.    Electrical impulse travels in a neuron from

a.    Dendrite ⇨ axon ⇨ axonal end ⇨ cell body

b.    Cell body ⇨ dendrite ⇨ axon ⇨ axonal end

c.    Dendrite ⇨ cell body ⇨ axon ⇨ axonal end

d.    Axonal end ⇨ axon ⇨ cell body ⇨ dendrite
Answer: (c) Dendrite ⇨ Cell body ⇨ Axon ⇨ Axonal end

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1.    In a synapse, chemical signal is transmitted from

a.    Dendritic end of one neuron to axonal end of another neuron

b.    Axon to cell body of the same neuron

c.    Cell body to axonal end of the same neuron

d.    Axonal end of one neuron to dendritic end of another neuron
Answer: (d) Axonal end of one neuron to dendritic end of another neuron

2.    In a neuron, conversion of electrical signal to a chemical signal occurs at/in

a.    Cell body

b.    Axonal end

c.    Dendritic end

d.    Axon
Answer: (b) Axonal end

3.    Which is the correct sequence of the components of a reflex arc?

a.    Receptors ⇨ Muscles ⇨ Sensory neuron ⇨ Motor neuron ⇨ Spinal cord

b.    Receptors ⇨ Motor neuron ⇨ Spinal cord ⇨ Sensory neuron ⇨ Muscle

c.    Receptors ⇨ Spinal cord ⇨ Sensory neuron ⇨ Motor neuron ⇨ Muscle

d.    Receptors ⇨ Sensory neuron ⇨ Spinal cord ⇨ Motor neuron ⇨ Muscle
Answer: (d) Receptors ⇨ Sensory neuron ⇨ Spinal cord ⇨ Motor neuron ⇨ Muscle

4.    Which of the following statements are true?

                                i.        Sudden action in response to something in the environment is called reflex action

                               ii.        Sensory neurons carry signals from spinal cord to muscles

                              iii.        Motor neurons carry signals from receptors to spinal cord

                              iv.        The path through which signals are transmitted from a receptor to a muscle or a gland is called reflex arc

                               e.        (i) and (ii)

                                f.        (i) and (iii)

                               g.        (i) and (iv)

                               h.        (i), (ii) and (iii)
Answer: (c) (i) and (iv)

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1.    Which of the following statements are true about the brain?

                                i.        The main thinking part of brain is hind brain

                               ii.        Centres of hearing, smell, memory, sight, etc. are located in forebrain.

                              iii.        Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the hind brain

                              iv.        Cerebellum does not control posture and balance of the body

e.    (i) and (ii)

f.     (i), (ii) and (iii)

g.    (ii) and (iii)

h.    (iii) and (iv)
Answer: (c) (ii) and (iii)

2.    Posture and balance of the body is controlled by

 .     Cerebrum

a.    Cerebellum

b.    Medulla

c.    Pons
Answer: (b) Cerebellum

3.    Spinal cord originates from

 .     Cerebrum

a.    Medulla

b.    Pons

c.    Cerebellum
Answer: (b) Medulla

4.    The movement of shoot towards light is

 .     Geotropism

a.    Hydrotropism

b.    Chemotropism

c.    Phototropism
Answer: (d) Phototropism

Control & Coordination

Exemplar Problems MCQ II

1.    The main function of abscissic acid in plants is to

a.    Increase the length of cells

b.    Promote cell division

c.    Inhibit growth

d.    Promote growth of stem
Answer: (c) Inhibit growth

2.    The growth of tendril in pea plants is due to

a.    Effect of light

b.    Effect of gravity

c.    Rapid cell divisions in tendrillar cells that are away from the support

d.    Rapid cell divisions in tendrillar cells in contact with the support
Answer: (c) Rapid cell divisions in tendrillar cells that are away from the support

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1.    The growth of pollen tubes towards ovules is due to

a.    Hydrotropism

b.    Chemotropism

c.    Geotropism

d.    Phototropism
Answer: (b) Chemotropism

2.    The movement of sunflower in accordance with the path of sun is due to

a.    Phototropism

b.    Geotropism

c.    Chemotropism

d.    Hydrotropism
Answer: (a) Phototropism

3.    The substance that triggers the fall of mature leaves and fruits from plants is due to

a.    Auxin

b.    Gibberellin

c.    Abscissic acid

d.    Cytokinin
Answer: (c) Abscissic acid

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1.    Which of the following is not associated with growth of plant?

a.    Auxin

b.    Gibberellins

c.    Cytokinins

d.    Abscissic acid
Answer: (d) Abscissic acid

2.    Iodine is necessary for the synthesis of which hormone?

a.    Adrenaline

b.    Thyroxin

c.    Auxin

d.    Insulin
Answer: (b) Thyroxine

3.    Choose the incorrect statement about insulin

a.    It is produced from pancreas

b.    It regulates growth and development of the body

c.    It regulates blood sugar level

d.    Insufficient secretion of insulin will cause diabetes
Answer: (b) It regulates growth and development of the body

4.    Select the mis-matched pair

a.    Adrenaline: Pituitary gland

b.    Testosterone: Testes

c.    Estrogen: Ovary

d.    Thyroxin: Thyroid gland
Answer: (a) Adrenaline: Pituitary gland

5.    The shape of guard cells changes due to change in the

a.    Protein composition of cells

b.    Temperature of cells

c.    Amount of water in cells

d.    Position of nucleus in the cells
Answer: (c) Amount of water in cells