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Control and Coordination

Q. What does control and coordination mean in an organism?

Ans. Control is the ability to regulate and restrain something.

Coordination is when different systems in an organism work together to

produce an appropriate response to stimuli.

Q. What is stimulus(plural:- stimuli)?

Ans. A stimulus is a detectable change in an organism's environment that

causes a physical or behavioral response. Stimuli can be internal or external

of the body of the organism.

Q. What is Neuron?

Ans. Neuron also known as nerve cell is the functional and structural unit of

the Nervous System. They transmit electrical and chemical signals throughout

the body and have three main parts: Cell body, Dendrites and Axon.

Cell body:- Also known as the soma, this is the core of the neuron and

contains the nucleus. The cell body maintains the cell and keeps the neuron

functioning efficiently.

Dendrites:- These are fibrous roots that branch out from the cell body like

antennae. Dendrites receive and process signals from other neurons or from

the environment, such as neurotransmitters.

Axon:- This is a long, narrow connecting line that snakes away from the cell

body and looks like a long tail. Axons branch into many smaller branches that

reach towards other neurons and send electrical impulses to them. These

impulses transmit information throughout the body.

Working process:-

The information, acquired at the end of the dendritic tip of a nerve cell, sets off

a chemical reaction that creates an electrical impulse. This impulse travels

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from the dendrite to the cell body, and then along the axon to its end. At the

end of the axon, the electrical impulse sets off the release of some chemicals.

These chemicals cross the gap, or synapse, and start a similar electrical

impulse in a dendrite of the next neuron. This is a general scheme of how

nervous impulses travel in the body. A similar synapse finally allows delivery

of such impulses from neurons to other cells, such as muscles cells or gland

Q. What are the receptors?

Ans. Receptors are specialised tips of the nerve cells that detect information

around our external environment by means of a stimulus and create an

impulse into the nervous system, which results in the nervous system to take

actions.

These receptors are situated in the sense organs such as eyes, nose,

tongue, ears and skin.

Q. How many types of neurons are there?

Ans. There are three types of neurons in the human nervous system:-

Sensory neurons, Motor neurons and Interneurons.

Sensory neurons:- Also called receptor neurons, these nerve cells receive

stimuli from the environment, such as touch, and send signals to the rest of

the nervous system.

Location of the receptors

Name of Receptor

Stimulus

Eyes

Photoreceptor

Light

Ears

Phono receptor

Sound

Nose

Olfactory receptors

Smell

Tongue

Gustatory receptors

Taste

Skin

Tango receptor

Thermo receptor

Touch

Heat/cold

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Motor neurons:- Also called effector neurons, these neurons connect to

muscles, glands, and organs throughout the body to carry out commands from

the central nervous system.

Interneurons:- These neurons are present in the brain and spinal cord, and

connect the different parts of the nervous system.

Q. What does synapse mean?

Ans. The tiny space between the nerve endings and dendrites of nearby

neurons are called synapse.

Q. What is Neuromuscular junction?

Ans. A neuromuscular junction (NMJ) is a specialized synapse that connects

a motor neuron to a muscle fiber, allowing the neuron to transmit signals to

the muscle and cause it to contract or relax.

Q. How is control and coordination done in human beings?

Ans. In human beings control and coordination is done by the two systems:-

1. Nervous System

2. Endocrine System

Q. What is the Nervous System?

Ans. The nervous system includes the brain, spinal cord, and a complex

network of nerves . This system sends messages back and forth between the

brain and the body. The brain is what controls all the body's functions.

The nervous system has two main parts: the Central Nervous System

(CNS) and the Peripheral Nervous System (PNS):

Central Nervous System (CNS):- Made up of the brain and spinal cord, the

CNS controls how we think, learn, move, and feel. The brain controls these

functions, and the spinal cord carries messages between the brain and the

nerves throughout the body.

Peripheral Nervous System (PNS):- Made up of nerves that branch off from

the spinal cord and extend to all parts of the body, the PNS feeds information

into the brain from most of the senses, carries signals that allow muscles to

move, and delivers signals that the brain uses to control vital, unconscious

processes like breathing and heartbeat. The PNS includes the cranial nerves,

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spinal nerves and their roots and branches, peripheral nerves, and

neuromuscular junctions.

Q. What does action mean in an organism?

Ans. The movement of muscles is called action in an organism. There are

three types of action:-

Voluntary action, Involuntary action and Reflex action.

Voluntary action:- The action which is done with the will and undercontrolled of

the organism is called Voluntary action. For example :- walking, talking, etc.

These actions are controlled by the brain of the organism.

Involuntary action:- The action which is done without the will and not

undercontrolled of the organism is called Involuntary action. For example :-

Heart beat, Digestion, flowing of blood, etc. These actions are also controlled

by the brain of the organism.

Reflex action :- The sudden action which we do without thinking is called the

reflex action but unlike the involuntary action it is controlled by the spinal cord.

For example :- Watering of mouth, withdrawal of hand when we unintentionally

touch a hot object.

Q. How does voluntary action take place?

Ans. Let's think of an example of a voluntary action:- A person hits a mosquito

which bites the person.

Pathway of the impulse during the above action:-

The pain is detected by the pain receptor and creates it into an electrical

signal(impulse) which passes through the sensory neuron to the spinal cord

and then through the interneuron reaches the brain . Brain thinks of the

situation and decides what to do, let say the brain decides to hit the mosquito

then it sends the impulse through the interneuron to the spinal cord and then

the spinal cord sends the signal through the motor neuron to the

neuromuscular junction and then the muscle(effector) of the hand. The muscle

acts accordingly and thus the person hits the mosquito.

Pathways of impulse in a voluntary action :-

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Q. What is the reflex arc?

Ans. The pathway of the impulse during a reflex action is called reflex arc.

Q. How does the Nervous Tissue cause Action?

Ans. Nervous tissue causes action by transmitting nerve impulses through the

neuromuscular junction to muscles, which then contract and relax. The

muscles contain special proteins that change shape and arrangement in

response to the electrical impulses. This new protein arrangement shortens

the muscle cells, causing them to move and contract.

Q. Describe Human brain, its parts and its functions.

Ans. Brain is the main coordinating centre of the humans.It's located inside

the skull, which protects it from the front, sides, and top, and is made up of

billions of nerve cells. The brain is divided into three main parts: Fore-brain,

Mid-brain and Hind-brain.

Fore-brain:-

The fore-brain is the main thinking part of the brain. It has regions which

receive sensory impulses from various receptors. Separate areas of the

fore-brain are specialised for hearing, smell, sight and so on. There are

separate areas of association where this sensory information is interpreted by

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putting it together with information from other receptors as well as with

information that is already stored in the brain. Based on Figure 7.2 Reflex arc

118 Science all this, a decision is made about how to respond and the

information is passed on to the motor areas which control the movement of

voluntary muscles. The forebrain of the human brain includes the following

parts:

1. Cerebrum:- The cerebrum is the largest part of the brain, making up about

80% of its volume. It's located at the front of the brain and is responsible for

storing memories, thinking, and receiving signals from receptors.

2. Thalamus:- A walnut-sized structure that relays sensory signals to the

cerebral cortex and regulates sleep

3. Hypothalamus:- Regulates a variety of body functions, including body

temperature, and produces hormones that regulate pituitary hormones

4. Limbic system:- Located on either side of the thalamus, this system controls

motivation and emotional behaviors, and permanent emotional memories

Mid-brain:-

The midbrain plays an important role in movement, especially eye

movements, and auditory and visual processing.

Hind-brain:-

Hind-brain is made up of three main parts: the pons, cerebellum, and medulla.

1. Pons: Interconnects different regions of the brain and takes part in

respiration.

2. Cerebellum: The second largest part of the brain, it helps maintain

balance and posture, and controls rapid muscle activities like running

and typing.

3. Medulla oblongata: Controls involuntary actions like heartbeat and blood

pressure, as well as swallowing, sneezing, vomiting, and coughing It

also contains a center that controls respiration, cardiovascular reflex,

and gastric secretions.

Q. How are our Brain and Spinal Cord protected?

Ans. Brain:- Bran is located inside the skull, which protects it from the front,

sides, and top and in addition to this the brain is contained in a fluid-filled

balloon which provides further shock absorption.

Spinal Cord:- Spinal cord is protected by vertebral column or backbone.

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Q. What is the difference between a reflex action and walking?

Ans.

Reflex Action

Walking

It is an involuntary action.

It is a voluntary action.

It is controlled by the spinal cord.

It is controlled by the brain.

It is a sudden action to a stimulus.

It is not a sudden action.

Q. What happens at the synapse between two neurons?

Ans. At the end of the axon, the electrical impulse sets off the release of

some chemicals. These chemicals cross the gap, or synapse, and start a

similar electrical impulse in a dendrite of the next neuron.

Q. Which part of the brain maintains posture and equilibrium of the body?

Ans. It is cerebellum which is the part of the hind-brain that maintains posture

and equilibrium of the body.

Q. How do we detect the smell of an agarbatti (incense stick)?

Ans. Smell of an agarbatti or any other smell is detected by nose which has

olfactory receptors which convert it into an electrical signal and send it to the

brain and the brain interprets it.

Q. What is the role of the brain in reflex action?

Ans. Reflex action is controlled by the spinal cord and not by the brain but

after the action, information is sent to the brain and the brain remembers its

consequences.

Q. How does control and coordination take place in plants?

Ans. Plants don’t have the nervous system so the control and coordination in

plants is done by the only chemical signals called hormones.

Q. How does movement occur in plants?

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Ans. Plants do not have muscles which cause movement in animals so the

plants move their part by the loss or gain of water by which shrink or swell the

cell respectively. There are two types of movements in plants:-

1. Independent of growth.

2. Dependent on growth also known as tropic movement.

Q. What does happen when we touch the leaf of a ‘touch me not plant’ or

‘mimosa plant’?

Ans. When we touch the leaf of a touch me not plant, it releases some

hormones which force the water move out of leaves and they shrink and fold

its leaves. This movement is an example of the independence of growth.

Q. What are tropic movements in plants and how many types are they?

Ans. The movements in a plant which cause the growth in the plant or its

parts is called the tropic movement.

There are six types of tropic movements in plants:-

1. Phototrophic:- Because of the sun.(movement in sunflower)

2. Geotropic:- Because of the gravity.(movement of roots and shoots)

3. Hydrotropic:- Because of the water.(movement of roots)

4. Chemotropic:- Because of the chemicals.(movement of pollen grains

towards ovules)

5. Thigmotropism:- Because of the touch.(movement of tendrils)

6. Thermotropism:- Because of the heat.(curling of leaves)

All the tropics movements are of two types:- Positive and Negative.

Positive Tropic movements means the movement towards the stimulus.

Negative Tropic movements means the movement away from the stimulus.

For example roots moves towards the earth but the shoots moves away from

the earth, so the movement of the roots are Positive Tropic movements and

the movements of shoots are Negative Tropic movements

Q. How do tendrils of a plant move around the support?

Ans. Some plants like the pea plant climb up other plants or fences by means

of tendrils. These tendrils are sensitive to touch. When they come in

contact with any support, the part of the tendril in contact with the object

does not grow as rapidly as the part of the tendril away from the object.

This causes the tendril to circle around the object and thus cling to it.

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Q. How does the sunflower bend towards the sun?

Ans. When the sunflower detects the sunlight, a hormone, named ‘auxin :- a

growth hormone’ is released in the shady side of the plant which makes the

part grow longer than the sunny part which makes the plant bends towards

the sun.

Q. What are plant hormones?

Ans. The chemical compounds which are used for the control and

coordination in a plant are called plant hormones. Example of plants

hormones are:-

1. Auxin :- A growth hormone found in apical meristematic tissue.

2. Gibberellin :- A growth hormone found in seeds and young leaves.

3. Cytokinin :- A growth hormone found in fruits and seeds.

4. Abscisic acid :- A hormone which prevents growth.

Q. How is the movement of leaves of the sensitive plant different from the

movement of a shoot towards light?

Ans. The movement of leaves of the sensitive plant is independent of growth

and called nastic movement but the movement of a shoot towards light is

dependent on growth and called tropic movement.

Q. Give an example of a plant hormone that promotes growth.

Ans. Auxin is an example of a plant hormone that promotes growth.

Q. How do auxins promote the growth of a tendril around a support?

Ans. The tendrils are sensitive to touch. When they come in

contact with any support, the part of the tendril in contact with the object

does not grow as rapidly as the part of the tendril away from the object.

This causes the tendril to circle around the object and thus cling to it.

Q. Design an experiment to demonstrate hydrotropism.

Ans. Hydrotropism is the tropic movement in which the stimulus is water so

the movement is toward the water or away from the water.

The experiment to demonstrate hydrotropism is as follows:

1. Plant a seedling in a vessel containing soil.

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2. Adjacent to the seedling place a porous pot containing water.

3. Leave the set-up for a few days.

4. We will observe that the roots of seedlings bend towards the source of

water and do not grow straight.

So, we can confirm from the experiment that the roots of plants show positive

hydrotropism as the roots of plant bend towards the porous pot of water.

Q. What are the limitations of electrical impulses?

Ans. There are two limitations to the use of electrical impulses.

1. They will reach only those cells that are connected by nervous tissue,

not each and every cell in the animal body.

2. Once an electrical impulse is generated in a cell and transmitted, the

cell will take some time to reset its mechanisms before it can generate

and transmit a new impulse. In other words, cells cannot continually

create and transmit electrical impulses.

Q. How do animals overcome the limitations of electrical impulses?

Ans. Animals do not have only the nervous system for the control and

coordination but they also have the endocrine system which are effectfull

where the nervous system is effectless. Thus animals overcome the

limitations of electrical impulses by the use of chemical compounds known as

hormones.

Q. What are animal hormones?

Ans. The chemical compounds which are secreted by the endocrine glands

are known as animal hormones.

Q. Name the human hormones, from where are they secreted and what are

their functions?

Ans.

Hormones

Glands

Functions

Deficiency

Diseases

Melatonin

Pineal gland

Help to sleep

Sleep disorder,

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stress, anxiety,

depression

Growth hormone

releasing

hormone (GHRH)

Hypothalamus

Regulates growth

hormone release

in the pituitary

gland

Dwarfish

Growth hormone

Pituitary

gland(Master

Gland)

It regulates

growth and

development of

the body.

Dwarfish, Giant

Thyroxine

hormone

Thyroid gland

Thyroxine

regulates

carbohydrate,

protein and fat

metabolism in the

body so as to

provide the best

balance for

growth.

Goitre

Parathyroid

hormone (PTH)

Parathyroid gland

Regulates blood

calcium levels

Bones related

diseases

Insulin

Pancreas

Regulates blood

sugar levels

Diabetes

Adrenaline

Adrenal glands

Prepare the body

for the scary

situation.

High blood

pressure, high

sweating, Severe

headache

Thymosin

Thymus

Regulates the

production of

lymphocytes to

protect the body

from allergies

and infections.

Tumur

Testosterone

Testis

Changes

Male

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associated with

puberty

Hypogonadism

Oestrogen

Ovary

Changes

associated with

puberty

Female

Hypogonadism

Q. Why is the Pituitary gland called the master gland?

Ans. The pituitary gland is called the "master" gland because it controls the

functions of many of the other endocrine glands. The pituitary gland is no

larger than a pea, and is located at the base of the brain.

Q. How does chemical coordination take place in animals?

Ans. Chemical coordination takes place in animals by hormones. Hormones

are secreted by the endocrine glands which make the endocrine system and

help in control and coordination. It is directly secreted into the blood and

through the blood it reaches the targeted organ.

Q. Why is the use of iodised salt advisable?

Ans. Iodine is essential for making thyroxine hormone which is essential for

regulating carbohydrate, protein and fat metabolism in the body so as to

provide the best balance for growth. Its deficiency causes swelling in the

thyroid gland which is called goiter so the use of iodised salt is advisable.

Q. How does our body respond when adrenaline is secreted into the blood?

Ans. Adrenaline is secreted directly into the blood and carried to different

parts of the body. The target organs or the specific tissues on which it

acts include the heart. As a result, the heart beats faster, resulting in

supply of more oxygen to our muscles. The blood to the digestive system

and skin is reduced due to contraction of muscles around small arteries

in these organs. This diverts the blood to our skeletal muscles. The

breathing rate also increases because of the contractions of the

diaphragm and the rib muscles. All these responses together enable the

animal body to be ready to deal with any scary situation.

Q. Why are some patients of diabetes treated by giving injections of insulin?

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Ans. The person whose pancreas does not secret required amount of insulin

hormones which regulates the sugar level in the blood then the person suffers

from diabetes. So the patient with diabetes is treated by giving injections of

insulin to regulate the sugar level in the blood.

Exercise

Q. Which of the following is a plant hormone?

Ans. (d) Cytokinin.

Q. The gap between two neurons is called a

Ans. (b) synapse.

Q. The brain is responsible for

Ans. (d) all of the above.

Q. What is the function of receptors in our body? Think of situations where

receptors do not work properly. What problems are likely to arise?

Ans. The function of receptors in our body is to detect any stimulus and

convert it into an electrical signal to send it to the brain.

Let's say our thermoreceptor do not work properly then, when our any

body’s part unintentionally comes in the contact of fire, then the body’s part or

the whole body may burn and cause the death of the person.

Q. Draw the structure of a neuron and explain its function.

Ans. Neuron also known as nerve cell is the functional and structural unit of

the Nervous System. They transmit electrical and chemical signals throughout

the body and have three main parts: Cell body, Dendrites and Axon.

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