CHAPTER – 7

CONTROL AND COORDINATION

INTRODUCTION

As the complexity of the individuals, plants or animals increases the different cells and organs
become separated from each other by greater distance. Thus it becomes necessary to have a
system by which the different parts of the organisms can function as a single unit. This is
possible only if the different parts can coordinate with each other and carry out a particular
function.

To carry out a simple function such as picking up an object from the ground there has to be
coordination of the eyes, hands, legs and the vertebral column. The eyes have to focus on the
object, the hands have to pick it up and grasp it, the legs have to bend and so does the back
bone (vertebral column). All these actions have to be coordinated in such a manner that they
follow a particular sequence and the action is completed. A similar mechanism is also needed
for internal functions of the body.

The individuals also have to adjust to the changing conditions around them and vary their
responses. At the same time, the internal conditions of the body should be maintained
constant. This is called homeostasis. Homeostasis is derived from 'homeo' meaning same and
'stasis' meaning standing still. The internal conditions of the body are maintained at a constant
by controlling the physiology of the organism. Just as in animals, plants also have to control
and coordinate their various functions.

NERVOUS SYSTEM
The nervous system of an animal is composed of
i) Specialized cells called neurons or nerve cells which can detect, receive and transmit
different kinds of stimuli.
ii) The nerve fibres which are certain bundles of extended processes of nerve cells.
NERVE CELLS
Nerve cells or neurons are the structural and functional units of the nervous system. Billions of
nerve cells make up our brain.
A nerve cell is a microscopic structure consisting of three major parts namely cell body,
dendrites and axon.

CELL BODY
It is the cell structure irregular in shape or polyhedral structure, it is also called as cyton. Cell
body contains cytoplasm with typical cell organelles and certain granular bodies are called
Nissl granules .

DENDRITES
Dendrites or Dendrons are shorter fibres which branch repeatedly and project out of the cell
body. Dendrites transmit electrical impulses towards the cyton.

AXON
One of the fibres arising from the cell body is very long with a branched distal end and it is
called as Axon.

The distal branches terminate as bulb like structures called synaptic knob filled with chemicals
called neuro transmitters. Axon contains axoplasm inside and is covered by a membrane called
neurilemma. Neurilemma encloses the axon except at the branched distal ends. In some
neurons called myelinated neurons an additional white fatty fibre called myelin sheath covers
the neurilemma. Myelin sheath is not continous over the neurilemma. The gaps left by the
myelin sheath on the axon are called Nodes of Ranvier. Over the myelin sheath are found
certain cells called Schwann cells.

TYPES OF NERVE CELLS

a) Myelinated or Medullated or White neurons:
When the axon is enclosed by the white fatty myelin cover it is called Myelinated or
Medullated or White neurons. This forms the cerebral cortex of our brain. b) Non- Myelinated
or Non-Medullated or Grey neurons:
This neuron is not enclosed by myelin sheath; so it appears greyish in colour. The axon is
covered by only neurilemma and Schwann cells. This type of neuron is found in the white
matter of cerebrum.
c) Unipolar neurons:
The embryonic nervous tissue contains unipolar neurons. An unipolar
neuron has a nerve cell body with a single process or fibre, which will act both as axon and
Dendron.

d) Bipolar neurons:
The sensory hair cells of the sense organs like rods and cones of retina are made up of bipolar
neurons. Each bipolar neuron has a cell body and two process at the ends, one acting as axon
and the other acting as Dendron.

e) Multipolar neuron:
The cerebral cortex contains the multipolar neurons; each multipolar neuron has a cell body
with many dendrites and an axon.
Synapse: The dendrites and the synaptic knobs of the axons of neighbouring neurons are in
physical contact with one another without fusing. This point of contact between the
neighbouring nerve cells is called synapse.

NERVE IMPULSE
The conduction of stimuli by the nerve cells is called nerve impulse. The dendrites will receive
the stimuli from the receptor (sense organ) and conduct the same as electrical impulse to the
axon through the cyton. At the synapse, the synaptic knobs release out chemical substances
called neuro transmitters which convert the electrical impulse into chemical impulse and pass
it to the neighbouring neuron.

TYPES OF NEURON

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

∙ Motor neuron: These neurons send signals to a muscle or a gland.
∙ Association neuron: These neurons relay the signals between sensory neuron and motor
neuron.

Pathways: From stimulus to response

In the holding stick activity you observed that there is coordination between eye and finger.
Different pathways are taken by nerves to bring about this coordinated activity. On the basis of
pathways followed, nerves are classified mainly into three different types.

AFFERENT NEURONS:
Afferent (or ferrying towards) which carry messages towards the central nervous system
(spinal cord or brain) from nerve endings on the muscles of different sense organs that sense
the change in surroundings are called stimulus detectors. These are also called ‘sensory’
nerves.

EFFERENT NEURON:
Efferent (or ferrying away) which carry messages from the central nervous system to parts that
shall carry out the response or the effectors (nerve endings). They are also called ‘motor’
nerves.

ASSOCIATION NERVES:
Association nerves, which link together the afferent and efferent nerves.

NERVOUS SYSTEM IN HUMANS

The nervous system can be divided into two major regions: the central and peripheral nervous
systems. The central nervous system (CNS) is the brain and spinal cord, and the peripheral
nervous system (PNS) is everything else. The brain is contained within the cranial cavity of the
skull, and the spinal cord is contained within the vertebral cavity of the vertebral column. It is a
bit of an oversimplification to say that the CNS is what is inside these two cavities and the
peripheral nervous system is outside of them, but that is one way to start to think about it. In
actuality, there are some elements of the peripheral nervous system that are within the cranial
or vertebral cavities. The peripheral nervous system is so named because it is on the
periphery—meaning beyond the brain and spinal cord. Depending on different aspects of the
nervous system, the dividing line between central and peripheral is not necessarily universal.

The nervous system can be divided into two parts mostly on the basis of a functional difference
in responses. The somatic nervous system (SNS) is responsible for conscious perception and
voluntary motor responses. Voluntary motor response means the contraction of skeletal
muscle, but those contractions are not always voluntary in the sense that you have to want to
perform them. Some somatic motor responses are reflexes, and often happen without a
conscious decision to perform them. If your friend jumps out from behind a corner and yells
“Boo!” you will be startled and you might scream or leap back. You didn’t decide to do that,
and you may not have wanted to give your friend a reason to laugh at your expense, but it is a
reflex involving skeletal muscle contractions. Other motor responses become automatic (in
other words, unconscious) as a person learns motor skills (referred to as “habit learning” or
“procedural memory”).

The autonomic nervous system (ANS) is responsible for involuntary control of the body, usually
for the sake of homeostasis (regulation of the internal environment). Sensory input for
autonomic functions can be from sensory structures tuned to external or internal
environmental stimuli. The motor output extends to smooth and cardiac muscle as well as
glandular tissue. The role of the autonomic system is to regulate the organ systems of the
body, which usually means to control homeostasis. Sweat glands, for example, are controlled
by the autonomic system. When you are hot, sweating helps cool your body down. That is a
homeostatic mechanism. But when you are nervous, you might start sweating also. That is not
homeostatic, it is the physiological response to an emotional state.

There is another division of the nervous system that describes functional responses. The
enteric nervous system (ENS) is responsible for controlling the smooth muscle and glandular
tissue in your digestive system. It is a large part of the PNS, and is not dependent on the CNS.
It is sometimes valid, however, to consider the enteric system to be a part of the autonomic
system because the neural structures that make up the enteric system are a component of the
autonomic output that regulates digestion. There are some differences between the two, but
for our purposes here there will be a good bit of overlap. See Figure for examples of where
these divisions of the nervous system can be found.

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.

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.

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.

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.

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.
INTEXT QUESTIONS
Question 1: What is the difference between a reflex action and walking?
Answer :
A reflex action is a rapid, automatic response to a stimulus. It does not involve any thinking.
For example, we close our eyes immediately when the bright light is focused. Walking, on the
other hand, is a voluntary action. It is under our conscious control.

Question 2: What happens at the synapse between two neurons?

Answer :
A very small gap that occurs between the last portion of axon of one neuron and the dendron
of the other neuron is known as a synapse. It acts as a one way valve to transmit impulses in
one direction only. This uni-direction transfer of impulses occurs as the chemicals are
produced in only one side of the neuron i.e., the axon’s side. From axon, the impulses travel
across the synapse to the dendron of the other neuron.

Question 3: Which part of the brain maintains posture and equilibrium of the body? Answer
: Cerebellum, a part of the hindbrain is responsible for maintaining posture and equilibrium of
the body.
Question 4: How do we detect the smell of an agarbatti (incense stick)?
Answer : The thinking part of our brain is the forebrain. It has separate areas that are
specialized for hearing, smelling, sight, taste, touch, etc. The forebrain also has regions that
collect information or impulses from the various receptors. When the smell of an incense stick
reaches us, our forebrain detects it. Then, the forebrain interprets it by putting it together with
the information received from other receptors and also with the information already stored in
the brain.
Question 5: What is the role of the brain in reflex action?
Answer : Reflex actions are sudden responses, which do not involve any thinking. For example,
when we touch a hot object, we withdraw our hand immediately without thinking as thinking
may take time which would be enough to get us burnt.
The sensory nerves that detect the heat are connected to the nerves that move the muscles of
the hand. Such a connection of detecting the signal from the nerves (input) and responding to
it quickly (output) is called a reflex arc. The reflex arcs −connections present between the
input and output nerves − meet in a bundle in the spinal cord.
REFLEX ARC: Reflex arcs are formed in the spinal cord and the information (input) reaches the
brain. The brain is only aware of the signal and the response that has taken place. However,
the brain has no role to play in the creation of the response.

FLOWCHART OF HUMAN BRAIN

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.

∙ 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.
 ∙ 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.

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

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.
INTEXT QUESTIONS

Question 1: What are plant hormones?

Answer : Plant hormones or phytohormones arenaturally-occurring organic substances. These
are synthesized in one part of the plant body (in minute quantities) and are translocated to
other parts when required. The five major types of phytohormones are auxins, gibberellins,
cytokinins, abscisic acid, and ethylene.

Question 2: How is the movement of leaves of the sensitive plant different from the
movement of a shoot towards light?
Answer : The movement of leaves of the sensitive plant, Mimosa pudica or “touch me not”,
occurs in response to touch or contact stimuli. This movement is independent of growth. The
movement of shoot towards light is known as phototropism. This type of movement is
directional and is growth dependent.

Question 3: Give an example of a plant hormone that promotes growth.

Answer : Auxin is an example of growth-promoting plant hormone.

Question 4: How do auxins promote the growth of a tendril around a support? Answer :
Auxin is synthesized at the shoot tip. It helps the cell grow longer. When a tendril comes in
contact with a support, auxin stimulates faster growth of the cells on the opposite side, so that
the tendril forms a coil around the support. This makes the tendrils appear as a watch spring.

Question 5: Design an experiment to demonstrate hydrotropism.

Answer : Take two small beakers and label them as A and B. Fill beaker A with water. Now
make a cylindrical-shaped roll from a filter paper and keep it as a bridge between beaker A and
beaker B, as shown in the figure. Attach few germinating seeds in the middle of the filter paper
bridge. Now, cover the entire set-up with a transparent plastic container so that the moisture is
retained.

Observation:
The roots of the germinating seeds will grow towards beaker A.

This experiment demonstrates the phenomenon of hydrotropism.

HORMONES IN ANIMALS
The hormones in animals are produced by the endocrine glands, and they too play an
important role in control and coordination.
Hormones are chemical substances that control and coordinate activities of living organisms
and also their growth. The term hormone was introduced by Bayliss and Starling. Animal
hormones do not bring about directional growth depending on environmental cues, but
promote controlled growth in various areas to maintain the body design. Thevarious
endocrine glands in humans are hypothalamus, pineal gland, pituitary gland, thyroid gland,
parathyroid glands, thymus, pancreas, adrenal glands, ovary (in female) and testis (in males).
FEATURES AND FUNCTIONS OF HORMONES:
1. They are secreted by the endocrine glands and are called ‘chemical messengers’. 2.
They are poured directly into blood stream as endocrine glands have no ducts of their
own (ductless glands).
3. They usually have their effect at sites different from the sites where they are
made. They act on specific areas called targetorgans.
4. Hormones coordinate body activities and growth
5. They are released in minute quantities

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.
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.

The pituitary gland:

• It is a pea-shaped gland located at the base of the brain.
• It is considered to be master gland as it secretes many hormones to regulate the
organs as well as the other glands.
• Different hormones secreted by this gland include Growth hormone, TSH, FSH,
LH, ACTH, MSH, Vasopressin and Oxytocin.

The hypothalamus:
• It is a neuro-endocrine part of the brain.
• It links the nervous system and the endocrine system through the pituitary gland. •
Different hormones secreted by this gland include TRH, GnRH, GHRH, CRH, Stomatostatin,
Dopamine.

The thyroid gland:

• It is located in the neck, ventral to the larynx.
• It is the one of the largest endocrine glands.
• The principal hormones produced by this gland are triiodothyronine and thyroxine. •
Thyroxine is a hormone that regulates the metabolism of carbohydrates, proteins and fats
in the body.
Hyposecretion of thyroxine leads to cretinin in children, and myxoedema in adults.
Hypersecretion of thyroxine leads to exopthalmic goitre in adults. Goitre is caused due to
deficiency of iodine in food. Iodine is essential for the synthesis of thyroxine.

Parathyroid glands:
• These are two pairs of small, oval-shaped glands embedded on the dorsal surface of the
thyroid gland present in the neck.
• They secrete parathormone. Parathormone helps in regulation of calcium and phosphate
ions in the bones and blood.
• Hyposecretion leads to parathyroid tetany and hypersecretion causes osteoporosis.
The adrenal glands:
• These are located above the kidneys and hence are called as suprarenal glands.
• Two regions of the adrenal gland are adrenal cortex and adrenal medulla.
• Adrenal cortex secretes the hormones like cortisol, aldosterone and androgens.
• Adrenal medulla secretes the hormones like adrenaline and noradrenaline. Adrenaline is
also called the “hormone of fight or flight,” or the emergency hormone. It prepares the body
to face an emergency condition of physical stress, like danger, anger and excitement.

The pancreas:
• It is located just below the stomach within the curve of the duodenum. It is both
exocrine and endocrine in function.
• It secretes hormones such as insulin, glucagon, somatostatin and pancreatic polypeptide.
• Insulin regulates the sugar level in our blood. Insulin secreted in small amounts increases
the sugar level in our blood which in turn causes a disease called diabetes mellitus.

Gonads:
Two types of gonads present in human beings are female gonads and male gonads.
Female gonads
• A pair of ovaries forms the gonads in female.
• Ovaries are the female sex organs that lie one on either side of the abdominal cavity.
Ovaries produce two hormones, namely, oestrogen and progesterone.
• Oestrogen controls the changes that occur during puberty, like feminine voice, soft skin and
development in mammary glands.
• Progesterone controls the uterine changes in the menstrual cycle, and helps in the
maintenance of pregnancy.

Male gonads
• A pair of testes forms the gonads in males.
• A pair of testes is the male sex organ located in the scrotum, which is outside the
abdomen.
• Testes produce the hormone testosterone.
• Testosterone controls the changes, which occur during puberty, like deeper voice,
development of penis, facial and body hair.

The pineal gland:

• It is located near the centre of the brain, dorsal to the diencephalon. • It produces the
hormone melatonin.
• Melatonin affects reproductive development, modulation of wake and sleep patterns, and
seasonal functions.

The thymus gland:

• It is located in front of the heart, in the upper part of the sternum.
• It produces the hormone thymosine.
• It helps in the maturation of T-lymphocytes.
INTEXT QUESTIONS

Question 1: How does chemical coordination take place in animals?

Answer : Chemical coordination takes place in animals with the help of hormones.Hormone is
the chemical messenger that regulates the physiological processes in living organisms. It is
secreted by glands. The regulation of physiological processes, and control and coordination by
hormones comes under the endocrine system. The nervous system along with the endocrine
system in our body controls and coordinates the physiological processes.

Question 2: Why is the use of iodised salt advisable?

Answer : Iodine stimulates the thyroid gland to produce thyroxin hormone. It regulates
carbohydrate, fat, and protein metabolism in our body. Deficiency of this hormone results in
the enlargement of the thyroid gland. This can lead to goitre, a disease characterized by
swollen neck. Therefore, iodised salt is advised for normal functioning of the thyroid gland.

Question 3: How does our body respond when adrenaline is secreted into the blood? Answer
: Adrenalin is a hormone secreted by the adrenal glands in case of any danger or emergency or
any kinds of stress. It is secreted directly into the blood and is transported to different parts of
the body.

When secreted in large amounts, it speeds up the heartbeat and hence supplies more oxygen
to the muscles. The breathing rate also increases due to contractions of diaphragm and rib
muscles. It also increases the blood pressure. All these responses enable the body to deal with
any stress or emergency.

Question 4: Why are some patients of diabetes treated by giving injections of insulin?
Answer : Diabetes is a disease in which the level of sugar in the blood is too high. Insulin, a
hormone secreted by the pancreas, helps in regulating the blood sugar levels. This is the
reason why diabetic patients are treated by giving injections of insulin.

EXERCISE QUESTIONS

Question 1: Which of the following is a plant hormone?

(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Answer : (d) Cytokinin is a plant hormone.

Question 2: The gap between two neurons is called a

(a) dendrite.
(b) synapse.
(c) axon.
(d) impulse.
Answer : (b) The gap between two neurons is called a synapse.
Question 3: The brain is responsible for
(a) thinking.
(b) regulating the heart beat.
(c) balancing the body.
(d) all of the above.
Answer : (d) The brain is responsible for thinking, regulating the heart beat and balancing
the body.
Question 4: 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 :
1.Receptors are sensory structures (organs/tissues or cells) present all over the body.
2.The receptors are either grouped in case of eye or ear, or scattered in case of skin.

Functions of receptors:
(i) They sense the external stimuli such as heat or pain.
(ii) They also trigger an impulse in the sensory neuron which sends message to the spinal cord.

1.When the receptors are damaged, the external stimuli transferring signals to the brain are
not felt.

2.For example, in the case of damaged receptors, if we accidentally touch any hot object, then
our hands might get burnt as damaged receptors cannot perceive the external stimuli of heat
and pain.

Question 5: Draw the structure of a neuron and explain its function. Answer :

1.Neurons are the functional units of the nervous system. The three main parts of a neuron
are axon, dendrite, and cell body.
 Functions of the three parts of a neuron:
Axon: It conducts messages away from the cell body.

Dendrite: It receives information from axon of another cell and conducts the messages
towards the cell body.

Cell body: It contains nucleus, mitochondria, and other organelles. It is mainly concerned with
the maintenance and growth.

Question 6: How does phototropism occur in plants?

Answer :
1.The growth movement in plants in response to light stimulus is known as phototropism.
2.The shoots show positive phototropism and the roots show negative phototropism. 3.This
means that the shoots bend towards the source of light whereas the roots bend away from
the light source.
Some examples of phototropism are as follows:
(a) The flower head of sunflower is positively phototropic and hence it moves from east to
west along with the sun.
(b) The ovary stalk of groundnut is positively phototropic before fertilization and becomes
negatively phototropic after fertilization, so that the fruit is formed underground.
Question 7: Which signals will get disrupted in case of a spinal cord injury?
Answer :
1.The reflex arc connections between the input and output nerves meet in a bundle in the
spinal cord.
2.In fact, nerves from all over the body meet in a bundle in the spinal cord on their way to the
brain.
3. In case of any injury to the spinal cord, the signals coming from the nerves as well as the
signals coming to the receptors will be disrupted.

Question 8: How does chemical coordination occur in plants?

Answer :
1.In animals, control and coordination occur with the help of nervous system.
2. However, plants do not have a nervous system.

3.Plants respond to stimuli by showing movements.

4.The growth, development, and responses to the environment in plants is controlled and
coordinated by a special class of chemical substances known as hormones. 5.These hormones
are produced in one part of the plant body and are translocated to other needy parts.

6.For example, a hormone produced in roots is translocated to other parts when required.
7.The five major types of phytohormone are auxins, gibberellins, cytokinins, abscisic acid, and
ethylene.

8.These phytohormones are either growth promoters (such as auxins, gibberellins, cytokinins,
and ethylene) or growth inhibitors such as abscisic acid.

Question 9: What is the need for a system of control and coordination in an organism?
Answer :

1.The maintenance of the body functions in response to changes in the body by working
together of various integrated body systems is known as coordination.

2.All the movements that occur in response to stimuli are carefully coordinated and
controlled.

3.In animals, the control and coordination movements are provided by nervous and muscular
systems.

4.The nervous system sends messages to and away from the brain.

5.The spinal cord plays an important role in the relay of messages.

6. In the absence of this system of control and coordination, our body will not be able to
function properly.

7.For example, when we accidentally touch a hot utensil, we immediately withdraw our hand.

8.In the absence of nerve transmission, we will not withdraw our hand and may get burnt.

Question 10: How are involuntary actions and reflex actions different from each other?
Answer :

1.Involuntary actions cannot be consciously controlled.

2.For example, we cannot consciously control the movement of food in the alimentary canal.

3. These actions are however directly under the control of the brain.

4.On the other hand, the reflex actions such as closing of eyes immediately when bright light is
focused show sudden response and do not involve any thinking.

5.This means that unlike involuntary actions, the reflex actions are not under the control of
brain.

Question 11: Compare and contrast nervous and hormonal mechanisms for control and
coordination in animals.
Answer :
Nervous system mechanism Hormonal system mechanism

1. The information is conveyed in the form 1. The information is conveyed in the form
 of electric impulse. of chemical messengers.

2. The axons and dendrites transmit the 2. The information is transmitted or

information through a coordinated effort. transported through blood.

3. The flow of information is rapid and the 3. The information travels slowly and the
response is quick. response is slow.

4. Its effects are short lived. 4. It has prolonged effects.

Question 12: What is the difference between the manner in which movement takes place
in a sensitive plant and the movement in our legs?
Answer :
Movement in sensitive plants Movement in our legs

1. The movementthat takes place in a 1. Movement in our legs is an example of

sensitive plant such as Mimosa pudica voluntary actions.
occurs in response to touch (stimulus).

2. For this movement, the information is 2. The signal or messages for these actions
transmitted from cell to cell by electro are passed to the brain and hence are
chemical signals as plants do not have consciously controlled.
any specialised tissue for conduction of
impulses.

3. For this movement to occur, the plant 3. In animal muscle cells, some proteins are
cells change shape by changing the found which allow the movement to
amount of water in them. occur.

ASSIGNMENT QUESTIONS SET – 1

CHAPTER – 7
CONTROL AND COORDNATION
1. What is a neuron?

2. Name any two types of tropism.

3. What is a phytohormone? Name any two phytohormones.

4. Mention the receptors for light and sound in animals.

5. How does control and coordination takes place in plants?

6. Mention the names of various phytohormones.

7. Discuss phototropism.

8. Differentiate between tropic and nastic movements.

9. Draw the diagram of a neuron.

10. Draw a neat diagram of the nervous system in an insect.

11. Describe the central nervous system in human beings.

12. Write the functions of any one part of the hind – brain.

13. What is the autonomic nervous system?

14. Define reflex action with suitable examples.

15. Name the hormones secreted by thyroid, parathyroid and pancreas.Reaction

of stimuli is a characteristic property of living organisms. Explain

16. It usually takes lot of time to observe the effect of a stimulus on

plants. Explain 17. Why is control and coordination system necessary

in organisms?

18. What is homeostasis?

19. Give examples of some of the movements shown by plants.

20. What are growth regulators?

21. What are the stages of growth in plants?

22. Name the different phytohormones.

23. What are auxins?

24. Give four major functions of auxins.

25. What are gibberellins and where are they

synthesised?

26. What is the most important commercial application of

gibberellins?

27. What are exocrine and endocrine glands?

28. What are hormones?

29. What are the characteristics of hormones?

30. Name the various endocrine glands.

31. What is TSH? Where is it produced?

32. Which gland has both exocrine and

endocrine parts?

33. Name the different regions of the brain

and their parts.

34. What is cerebrum? What are its

functions?

35. What is the importance of hypothalamus?

36. What are the functions of mid brain?

37. What is cerebellum? Where is it present? What are

its functions?

38. What is the importance of medulla oblongata?

39. What are the functions of spinal cord?

40. What is a reflex?

41. What are the two main types of reflexes? Give one

example for each.

42. What is a synapse?

43. What are nerve fibres?

44. What are nodes of Ranvier?

45. What are the three types of nerves?

46. What are receptors?

47. What are effectors?

48. What is meningitis?
49. What are the three divisions of the human

nervous system?
50. What is the central nervous system composed

of?

51. How are organs of the central nervous system protected?

52. Difference between dormancy and breaking of dormancy

53. Write Four major types of plant hormones and their functions

54. How does tropism helps in movement?

55. Why does the stem of a plant bend to one direction?

56. Explain the bending of plant root away from light by the action of

auxin hormones

57. Give an example of chemotropism? With the help of diagram

58. Roots can grow against the law of gravity. When does

this happen?

59. Definition and Function of thigmotropism

60. Why do followers open their petals in morning and close

them in evening

61. Name the Scientific terms for Bending of shoot towards

sunlight

62. Name the Scientific terms for Growing of root towards the

earth

63. Name the Scientific terms for Growth of a pollen tube

towards ovule

64. Name the Scientific terms for Bending of root towards water

65. Name the Scientific terms for Winding of tendril

around a support

66. What is Receptor and write its role

67. Explain the Function of Human nervous system

68. Explain the function of electrical impulses

69. Draw the diagram of neuron and explain its function

70. How are messages transferred from one neuron to another?

71. Name the Gap between two neurons

72. Explain the types of peripheral nervous systemIn a reflex action, we are
unaware that anything is going to happen to us. Explain

73. Explain the Diagram of reflex arc with its details

74. How effectors cause action

75. What is Self governing nervous system and write its function

76. What is the Functions of central nervous system?

77. Brain is the highest coordinating centre in the body. Explain.

78. Explain the Function of different part of brain.

79. How is all the voluntary action of body coordinated by cerebrum?

80. What is Animal hormones and write its functions

81. Hormones are kind of chemical messengers. Explain

82. Name all glands in our body having both exocrine and endocrine functions?

83. What is hormonal system? Position of endocrine glands in

human body.

84. Explain the Functions of all glands in our body

85. What are the two main centers for the coordination of two systems?
86. What all can happens if the pituitary glands do not function properly
87. How hormones help in coordinated growth?
88. Write the Sense organs of our body
89. Is walking different from reflex action
90. What do you understand by CNS? Explain
91. Draw Flow chart to show the classification of nervous system into various parts

92. What is synapse? What happens at the synapse between two

neurons? How are the messages carried?
93. Who detects smell and taste in our body?
94. Why does the food taste different when you nose is blocked?
95. Explain Insulin and diabetes.
96. Draw and mark Location of all glands in the human body
97. Write the Function of thyroxin hormone
98. Name one hormone found in male
99. Write the Function of hypothalamus, pituitary gland and cerebrum
100. Explain the Main thinking part of brain
101. Explain the Parts covered under hind brain
102. Name the part which control blood pressure, salivation and
vomiting control

103. What do you understand by the term reflex arc

104. Write the Function of gustatory receptor

105. Write a note on reflex action,