Students can download Class 10 Science Chapter 7 Control and Coordination Important Questions, KSEEB SSLC Class 10 Science Important Questions and Answers helps you to revise the complete Karnataka State Board Syllabus and score more marks in your examinations.
Karnataka SSLC Class 10 Science Important Questions Chapter 7 Control and Coordination
What is meant by control and coordination system in organisms?
All organisms respond to stimuli by sensing the changes in their environment. There must be coordination between the various organs of the body to respond suitably to those changes.
Further, there must be a system to control the organs that sense and respond to the changes. The system that performs the control and coordination of the activities of the body is called control and co-ordination system.
What is meant by coordination?
The working together of various organs of the body of an organism in an appropriate manner to produce proper reaction to a stimulus is called coordination.
What is the need for a system of control and coordination in an organism?
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. All the movements that occur in response to stimuli may involve several organs whose activities are to be carefully coordinated and controlled.
This is not only essential for our survival but also for efficient functioning. In the absence of this system of control and coordination, our body will not be able to function properly. For example, when we accidentally touch a hot utensil, we immediately withdraw our hand. In the absence of nerve transmission, we may get burns.
Mention the two ways in which coordination between the organs is brought about in higher order animals.
Co-ordination between the organs in higher order animals is brought about in two ways namely by the nervous system and the endocrine system.
What is the structural and functional unit of our nervous system called?
The basic unit of our nervous system is a set of specialized cells called neurons.
Explain briefly how we perceive a sensation.
A sense organ in our body receives the stimuli from the environment. Each stimulus is passed to the brain through the sensory nerves. The stimulus is interpreted by the relevant part of the brain. When this happens, we perceive the stimulus.
Why are sense organs called ‘receptors ’ in the control and coordination system of an organism?
All our sense organs such as eye, ear, nose, tongue and skin receive stimuli from the environment and pass it on to the central nervous system through the sensory nerves. This is why sense organs are called ‘receptors’ in the control and coordination system.
What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Receptors are present in all parts of our body for example in skin, eye, nose, tongue etc. They detect the signals and send them through sensory nerves to the brain in the form of electrical signals. If these receptors are damaged, then they will not detect the input and the body will not be able to respond to the situation. This may harm our body in a danger situation.
What is a neuron?
The structural and functional unit of our nervous system is called a neuron. It is another name for a nerve cell.
Draw the structure of a neuron and explain its function.
- Dendrite – The part where information is acquired.
- Axon – The part through which information travels as an electric impulse
- Nerve ending – The part where impulse is converted into chemical signal for onward transmission
Neurons conduct information via electrical impulses from one part of the body to another.
Identify the parts of a neuron
- Where information is acquired,
- Through which information travels as an electrical impulse, and
- Where this impulse is converted into a chemical signal for onward transmission.
- In a neuron, the information is acquired by the dendrites.
- In a neuron, the information travels as electrical signals through axon.
- In a neuron, the impulse is converted into chemical signals for onward transmission at the synapse.
What is an impulse? Explain with an example.
The flow of message through the nerve is called an impulse. When our finger is pricked, we feel the sensation of pressure and pain. Our brain senses the prick and generates a response and we withdraw our hand. This flow of message through the nerve is called impulse.
Why do we lose taste of our food when we have a bad cold?
When we chew food, the aroma of the food travels to our nasal cavity. The nose carries the odour- related signals to the area of the brain (olfactory lobe) that processes this information. The information from both the nose and the tongue get combined to give us a sense of flavour of our food.
However, during a cold, mucus blocks this passage to the nasal cavity and in the absence of information regarding the smell, our brain cannot give us the correct taste of food.
Describe the structure of a nerve cell (neuron).
A nerve cell is called a neuron. It is the structural and functional unit of the nervous system. A neuron consists of three major parts namely the cell body, dendrites and axon. The cell body is a typical eukaryotic cell with a clear nucleus. Each neuron has several tiny and branched protoplasmic processes emerging out of the cell body. These structures resembling roots are called dendrites.
Dendrites receive impulses in the form of electrical signals and transmit them to the axon. An axon looks like a long stem growing out of the cell body. Axons carry electrical messages away from the nerve cell body. The axon branches at the end, forming nerve endings. These are the points where the neuron communicates with other cells. .
How does communication occur between two neurons?
Explain the transmission of a nerve impulse in the body.
The information is acquired at the end of the dendritic tip of a nerve cell. This sets off a chemical reaction that creates an electrical impulse. This impulse travels 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.
In multicellular organisms, compared to electrical communication chemical communication is more steady and persistent Analyse this statement
Although electrical communication is faster, it is not as efficient as chemical communication. Nerve impulses in electrical communication can reach only those cells that are connected by the nervous tissues. The chemicals however travel throughout the body through blood and reach every single cell.
However their action is target-specific. The effect of electrical signals is short-lived while the effect of chemical signals usually lasts longer. Nerve cells cannot continuously generate and transmit nerve impulses as they need to reset their mechanisms before they can generate and transmit a new impulse.
Therefore, communication is not persistent. In chemical communication, the information is spread throughout the body by blood and the effect generally lasts longer. Unlike electrical communication, chemical communication is target-specific. Therefore, chemical communication is more steady and persistent.
What is meant by reflex action ? Give examples.
An automatic or involuntary activity brought about by relatively simple nervous circuits normally without the involvement of the brain is called reflex action. It is an automatic response to an external stimulus.
For example, a stimulus like pinprick causes sudden withdrawal of the finger. The withdrawing action comes before the brain senses the stimuli. Sudden withdrawal of the hand on accidental touch of a hot object is another example of reflex action.
What is a reflex arc? Mention the parts of a reflex arc.
The path taken by an impulse in a reflex action is called reflex arc. A reflex arc consists of five distinct parts:
- A receptor to receive the stimulus.
- A sensory neuron that conducts impulses from the receptor to the spinal cord or the hind-brain.
- An association neuron, which transmits the impulse from the sensory neuron to a motor neuron.
- A motor neuron through which the impulses pass on to an effector organ.
- An effector where the action takes place in response to the stimulus.
Draw a neat diagram of the reflex arc when we accidentally touch a hot object
Why do we find the evolution of reflex arcs in animals?
Reflex arcs have evolved in animals because the thinking process of the brain is not fast enough. In fact many animals have very little or none of the complex neuron network needed for thinking.
So it is quite likely that the reflex arcs have evolved as efficient ways of functioning in the absence of true thought processes (performed by brain). However, even after complex neuron networks have come into existence, reflex arcs continue to be more efficient for quick and emergency responses.
Which is the centre for reflex actions?
The spinal cord is the centre for all reflex actions.
What is the difference between a reflex action and walkins?
A reflex action is an involuntary action, which is a rapid and automatic response to a stimulus. It is not under our control. Walking is a voluntary action that requires our thinking and the act is completely in our control. Reflex actions are controlled by the spinal cord whereas walking is controlled by the brain.
Which are the three general components of nervous system?
The nervous system consists of receptors, effectors and conductors.
Differentiate between receptors, effectors and conductors.
The component of the nervous system that receives the stimulus is called receptor. The organs, which show a visible response, are called effectors. The tissues that carry messages between the receptors and effectors are called conductors.
Which are the receptors, effectors and conductors in higher animals?
In higher animals, the receptors are the sense organs; muscles and glands are the
effectors; and nerves are the conductors.
Trace the sequence of events that occur when a bright light is focussed on your eyes.
When a bright light is focussed on the eye, the receptor cell receives the message and passes it on to sensory neuron, which takes the message to the brain. The brain processes the information and gives a command to the organ concerned (eye). The motor neuron carries the command to the muscles of the eye and the eye muscle contracts.
Receptor → Sensory neuron → Brain → Motof neuron → Eye → Eye muscle contracts.
What happens at the synapse between two neurons?
The nerve impulses are carried out by a small gap called synapse between the nerve ending of one neuron and dendrite of another by means of a neurotransmitter. The nerve impulse travelling through the first neuron reaches the axon endings. It releases a small amount of a chemical substance into the synapse.
This chemical substance crosses the gap and starts a similar electrical impulse in the dendrite of the next neuron. From dendrite, the nerve impulse is carried to the cell body and then to the end. It can then be transferred to the third neuron in a similar way. This process continues till the electrical impulse reaches the brain or spinal cord.
Which are the three basic divisions (components) of the human nervous system?
The three basic components of the human nervous system are Central nervous system, Peripheral nervous system and Autonomic nervous system.
Which are the components of the central nervous system?
The two main components of the central nervous system are the brain and the spinal cord.
What is peripheral nervous system? What is it made of?
The part of the nervous system lying outside the central nervous system (brain and spinal cord) is called peripheral nervous system. Peripheral nervous system helps in facilitating communication between the central nervous system and other parts of the body.
The peripheral nervous system consists of nerves (31 pairs) that emanate from the spinal cord and nerves (12 pairs) that emanate from the brain. These nerves are called spinal nerves and cranial nerves respectively.
All these nerves and their branches together will constitute the peripheral nervous system. The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system.
What is autonomic nervous system? What does it consist of?
The part of our nervous system that controls the involuntary functions of the body is called autonomic nervous system.
The autonomic nervous system consists of two sets of nerves, the sympathetic and parasympathetic nervous systems. Each consists of nerves that control the activity of the heart, blood vessels, and other organs containing smooth muscles.
Name some involuntary activities that take place in our body. Which part of our nervous system controls and coordinates these activities?
Some of the involuntary activities of our body include salivation, heartbeat, respiration, blood circulation, digestion of food, secretions of various glands, sweating etc. These activities are not under the control of our will.
The involuntary activities of our body are controlled and co-ordinated by the autonomic nervous system and medulla of the hind-brain.
How are involuntary actions and reflex actions different from each other?
Involuntary actions do not require conscious, thinking and are not under the control of our will. These actions are governed by the autonomic nervous system. Involuntary actions are the response to internal stimuli.
On the other hand, reflex action is a rapid and spontaneous action in response to any stimulus. Reflex actions are also involuntary actions which are governed by the spinal cord. Reflex actions are the response to external stimuli.
Draw a neat diagram of vertical section Of the human brain and label the parts.
Draw the diagram showing longitudinal section of the hitman brain. Label the following parts:
- Thinking centre,
- The part that regulates body balance.
- Fore-brain – Main thinking part of the brain; the part that has separate areas specialised for hearing, smell, sight, etc.
- Cerebrum – The part responsible for thinking, hearing, emotion, consciousness and voluntary movements
- Pons – The part involved in sleep
- Medulla – The part that controls involuntary actions such as blood pressure, salivation, vomiting, breathing and circulation
- Cerebellum – The part that maintains body balance; responsible for precision of voluntary actions
- Hypothalamus – The part responsible for regulating basic biological needs such as hunger, thirst, temperature control
Describe briefly the structure of the human brain.
The human brain is a highly specialized organ. It is the highest coordinating centre of the body, present in a bony cage called cranium. Three membranes called meninges cover the brain.
The cerebro-spinal fluid present between the membranes provides protection to the brain against mechanical shocks. The brain is divided into three main regions namely fore-brain, mid-brain and hind-brain.
The fore-brain consists of two major parts called cerebrum and diencephalon. Cerebrum consists of two regions namely the outer cortex and the inner medulla. Cortex is composed of cytons that form the grey matter while the medulla is composed of nerve fibres that form the white matter.
The cortex is deeply folded into ridges called convolutions. The parts of the brain below the cerebrum are together called diencephalon. It is divided into upper thalamus and lower thalamus.
The mid-brain is a small region of the brain made up of nerve fibres connecting the cerebrum and the cerebellum.
The hind-brain consists of three parts namely pons, cerebellum and medulla oblongata. Pons is the connecting medium between cerebrum, cerebellum and medulla oblongata.
The region that lies behind and below the cerebrum is called cerebellum. The posterior-most part of the brain, which continues as spinal cord, is called medulla oblongata.
List the functions of the fore-brain.
The following are some of the functions of the fore-brain:
- The olfactory lobes of the fore-brain receive impulses from the smell receptors in the nose and interpret them.
- The cerebrum of the fore-brain has sensory areas, motor areas and association areas. Sensory areas of the cerebrum receive impulses from the sensory receptors. The motor areas will send instruction to the various effectors of the body. The association areas store information and experiences. This will help in thinking, memory, learning and emotional response.
State the functions of the following: Cranium, cerebrum, cerebellum, mid-brain, pons and
1. Cranium: Cranium is a bony case that surrounds the brain. It protects the brain from mechanical shocks.
2. Cerebrum: Cerebrum is the seat of consciousness, intelligence, imagination, reasoning, emotions and memory. The specific areas of the cerebrum perform different but specific functions. There are separate centres for vision, hearing, smell, taste, touch, speech and so on. These centres receive inputs from the sense organs and interpret them. Cerebrum also controls the voluntary movements of the body.
3. Cerebellum: Cerebellum is responsible for the maintenance of equilibrium and posture of the body. It co-ordinates and controls the movement of muscles in actions like walking and running. It is associated with voluntary muscular movements and maintenance of balance and posture of the body.
4. Mid-brain: The mid-brain serves as a relay station through which impulses are carried from the hind-brain to the fore-brain. It is especially concerned with receiving impulses from eyes and ears.
5. Pons: Pons is the conducting medium between cerebrum, cerebellum and medulla oblongata. It carries impulses from one part of the cerebellum to the other.
6. Hypothalamus: This is the major integrating centre for the autonomic nervous system. It influences heart rate, blood pressure, gastrointestinal secretions, body temperature, and motility.
7. Medulla oblongata: This part of the brain has centres that control the involuntary activities of the body such as breathing, heartbeat, movement of digestive tract, enzyme secretions, blood pressure and other activities. It has reflex centres for stimuli.
Mention the structures that protect the brain and spinal cord.
The brain is protected by a bony case called cranium. The spinal cord is protected by a bony case called vertebral column. The cerebro-spinal fluid that circulates between the brain and the spinal cord also provides protection from injury.
How is the spinal cord protected in our body?
The spinal cord is protected by a bony case called vertebral column.
Which signals will set disrupted in case of a spinal cord injury?
In case of a spinal cord injury, the signals coming from the receptor organs through the sensory nerves and the signals coming to the receptors from the brain will be disrupted. As both these signals meet in a bundle in the spinal cord, any injury to the spinal cord will disrupt both these signals.
Which part of the brain maintains posture and equilibrium of the body?
The part of the brain that maintains posture and equilibrium of the body is called cerebellum.
How do we detect the smell of an aearbatti (incense stick)?
We have olfactory receptors located in our nose. These receptors detect the smell of agarbatti. This information in the form of nerve impulse is transmitted to olfactory lobes of fore-brain. When the message is interpreted there, we experience the smell of the agarbatti.
What is the role of the brain in reflex action?
The purpose of reflex action is to provide a quick response in situations where the organism does not have enough time to think. Reflex arcs are formed in the spinal cord, although the information inputs also reach the brain little later. Though the message to react is sent by the spinal cord, the activity of various organs to carry out the response is co-ordinated by brain.
Name the part of the brain, which controls
- Voluntary actions,
- Involuntary actions.
- Voluntary actions are controlled by cerebellum.
- Involuntary actions are controlled by medulla.
How do nervous tissues cause action in muscles?
Nervous tissues collect information, send it around the body, process information, make decisions based on information, and convey decisions to muscles for action. This means, muscle tissue will do the final job through movements.
The muscle cells will move by changing their shape so that they shorten. Muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses. When this happens, new arrangements of these proteins give the muscle cells a shorter form.
Give examples to show that plants respond to stimuli In the form of movement
Lotus flower blossoms only when the sun rises and folds itself on sunset. Jasmine blossoms at sunset and folds on sunrise. The roots from the branches of big banyan frees grow towards earth to form prop roots.
The leaves of a touch-me-not plant fold and droop when touched. The tendrils of pepper plants have a spiral movement around a tree during their growth. All these show that plants respond to stimuli in the form of movement.
Name the two types of movements shown by plants. Give an example for each.
The two types of movements shown by plants are
- Growth dependent movements and
- Growth independent movements.
For example, the folding up and drooping of the leaves of a touch-me-not plant is a movement that is independent of growth. The directional movement of a seedling is an example for a growth dependent movement. If the seedling stops growing, we don’t see its movement.
The movements in plants are not as visible as in the case of animals. Give reason.
Plants are generally anchored in a fixed place and they dcs not have a nervous system. They respond to external stimuli generally by revealing growth. Growth is a slow but gradual process. Therefore, the movements in plants are not easily perceivable.
How do you show the response of a plant to light?
Fill a conical flask with water. Cover the neck of the flask with a wire mesh. Keep two or three freshly germinated bean seeds on the wire mesh. Take a cardboard box which is open from one side.
Keep the flask in the box in such a manner that the open side of the box faces the light coming from a nearby window. After two or three days, you will notice that the shoots bend towards the light and roots away from the light.
Now turn the flask so that the shoots are away from the light and the roots are towards the light. Leave it undisturbed in this condition for a few days. Now also we see the shoots bending towards the light and roots bending away from the light. This establishes the response of plants to light.
What is tropism?
The growth or the turning movement of all or part of an organism, usually a plant, in a particular direction (either away or towards) in response to an external stimulus is called tropism.
What is phototropism? Give an example.
The orientation of a plant or any other organism in response to light, either towards the source of light (positive phototropism) or away from it (negative phototropism) is called phototropism.
Plant growing in the direction of light is an example for phototropism. The shoots bend towards light. This is positive phototropism. The roots bend away from light. This is negative phototropism.
A young green plant receives sunlight from one direction only. What will happen to its shoot and roots?
The shoot of the plant bends towards the light, whereas roots bend away from the light.
How does phototropism occur in plants?
The directional movement of a plant in response to light is called phototropism. The shoot of a plant responds by bending towards light while the roots bend away from light. This happens as follows:
1. When sunlight falls straight on the plant, the auxin hormone synthesised at the tip of the stem spreads uniformly down the stem and due to equal concentration of auxin, stem grows straight.
2. When sunlight falls on only one side of the plant, the auxin diffuses towards the shady side of shoot. The concentration of auxin stimulates the cells to grow longer. Therefore, the stem appears to bend towards the source of light.
What is geotropism? Give an example.
The growth of the parts of a plant in response to the force of gravity is known as geotropism. For example, roots grow downwards in the direction of gravity (positive geotropism) and stem grows upwards against gravity (negative geotropism).
A potted plant is made to lie horizontally on the ground. Name the part of the plant that shows
- Positive geotropism and
- Negative geotropism.
- The root shows positive geotropism as it grows in the direction of gravity.
- The stem shows negative geotropism as it grows against the direction of gravity.
What is hydrotropism? Give an example.
The growth or movement of an organism or its body part towards or away from water or moisture is called hydrotropism.
For example, a plant root would bend in soil because it senses that water is available nearby. This is positive hydrotropism.
Design an experiment to demonstrate hydrotropism.
Take a tray filled with soil. Plant a seedling in the tray at one end. Add water to the soil at the other end with the help of a pipe. Observe the roots over a few days. The root of the plant is seen to move towards the wet soil. This shows that the roots are positively hydrotropic.
What is chemotropism? Give an example.
The growth or movement of a plant or plant part in response to an external chemical stimulus is called chemotropism.
The growth of a pollen tube down the style during fertilization in response to the presence of sugars in the style is an example for chemotropism.
How is the movement of leaves of a sensitive plant different from the movement of a shoot
The main differences between the movement of leaves of a sensitive plant and movement of a shoot towards light are as follows:
|Movement of Leaves of a Sensitive Plant
|Movement of Shoot towards Light
|1. It is a movement which does not depend on the direction of stimulus applied.
|It is a movement which depends on the direction of stimulus applied.
|2. The stimulus is touch.
|The stimulus is light.
|3. It is caused by the sudden loss of water from the swellings at the base of leaves.
|It is caused by the unequal growth on the two sides of the shoot.
|4. It is not a growth movement. It is a fast movement.
|It is a growth movement. It is a slow movement.
Plants neither have a nervous system nor muscles. How do they control and coordinate their bodily activities?
Plants neither have a nervous system nor muscles for control and coordination. Plants achieve control and coordination with the help of chemical substances called plant hormones or phytohormones.
How does chemical coordination occur in plants?
Chemical coordination in plants occurs with the help of fluids secreted in plants known as phytohormones or plant hormones. These hormones regulate the growth of the plants. For example, auxin is responsible for the growth of the plants and cytokinin helps in cell division in the fast growing part of the plant.
What are plant hormones?
Hormones (chemicals) secreted in the body of plants that help in the coordination of the bodily activities such as growth, development and response to stimuli and environment are called plant hormones. They are also called phytohormones.
Give two examples of plant hormones that promote growth.
Auxins and Gibberellins are plant hormones that promote growth in plants.
Nanie a plant hormone that promotes cell division.
A plant hormone that promotes cell division is cytokinin.
How do auxins promote the growth of tendril around a support?
The movement of tendril around a support is caused by the plant hormone called auxin. When a tendril comes 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 is caused by the action of auxin hormone.
Less auxin occurs on the side of contact as compared to the free side. As a result, auxin promotes growth on the free side and therefore the tendrils coil around the support.
Give examples of plant hormones which act as growth inhibitors.
Growth-inhibiting plant hormones include abscisic acid and ethylene.
What is abscisic acid? What is its role in a plant body?
Abscisic acid is a plant hormone that is responsible for inhibition of growth, besides other effects such as wilting of leaves.
One of the major roles of abscisic acid is to suspend cell growth and division when it is time for the plant to go into a dormant state, such as in autumn. It not only stops growth in various areas of the plant, but in some cases it causes the formation of a hard outer covering on the bud, which protects it from harsh winter conditions.
Name the stress hormone in plants that functions during drought. Why is it called a stress hormone?
The stress hormone in plants that functions during drought is abscisic acid. Abscisic acid is called stress hormone as it induces various responses in plants against stress conditions. It increases the tolerance of plants towards various stresses. It induces the closure of the stomata during water stress. It promotes seed dormancy and ensures seed germination during favourable conditions.
Distinguish between auxins and abscisic acid.
|1. This is a growth-promoting plant hormone.
|This is a growth-inhibiting plant hormone.
|2. Auxin is a plant hormone produced in the stem tip that promotes cell elongation.
|These hormones are involved in the abscission of leaves, flowers, and fruits and the dormancy of buds and seeds.
|3. These are a group of compounds.
|This is a single compound.
What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
|Movement in sensitive plants
|Movement in our legs
|1. The movement in a sensitive plant is an involuntary action.
|Movement in our legs is a voluntary action.
|2. No special tissue is involved in the action.
|Nervous systems such as CNS and PNS are involved in the action.
|3. Directed by hormonal action.
|Directed by the nervous system.
Name the plant hormones responsible for the following:
- Elongation of cells,
- Growth of stem,
- Promotion of cell division,
- Falling of senescent leaves.
- Abscisic acid.
How does chemical coordination take place in animals?
In animals, hormones secreted by endocrine glands achieve chemical coordination. These hormones function as chemical messengers. They are released by endocrine glands directly into the blood without any involvement of special ducts from where they reach the target tissue or organ to act. These organs and tissues then respond and enable the body to deal with different situations.
What are glands? Mention its types.
A cell, a tissue or an organ, which secretes useful chemicals required for various functions of the body; is called a gland.
The glands in our body are broadly classified into two types. They are
- Exocrine glands and
- Endocrine glands.
What are exocrine glands? Give two examples for exocrine glands in the human body.
Glands whose discharge is carried through ducts to their target organs are called exocrine glands. E.g. Salivary glands, sebaceous glands in the skin etc.
What are endocrine glands? List the major endocrine glands in the human body.
The glands whose secretions are carried to the target organs directly through the blood stream are called endocrine glands or ductless glands.
The major endocrine glands in the human body include pituitary gland, thyroid gland, parathyroid gland, thymus gland, adrenal gland, islets of Langerhans and gonads.
Differentiate between exocrine glands and endocrine glands.
|1. These glands discharge their secretions into ducts.
|These glands discharge their secretions directly into the blood.
|2. These are located close to the site of action.
|These glands may be present far away from the target organs.
|3. Secretions made by these glands are called enzymes.
|Secretions made by these glands are called hormones.
Define the terms: hormones, target organs.
The chemical substances secreted by endocrine glands are called hormones. The organs on which hormones act are called target organs.
Why are hormones called chemical messengers?
Hormones are chemical substances, which carry information from one part of the body to the other. Hence they are called chemical messengers.
Distinguish between hyper secretion and hypo secretion.
Excessive secretion of the hormones by an endocrine gland is called hyper secretion and inadequate secretion is called hypo secretion.
Draw a neat diagram showing the major endocrine glands in the human body.
Where is thyroid gland located? Mention the hormone secreted by this gland.
Thyroid gland is located close to the trachea in the neck. It secretes a hormone called thyroxin.
Name the hormone that is made of iodine and amino acids.
Thyroxin is the hormone that is made of iodine and amino acids.
Mention the functions of thyroxin.
Thyroxin increases the rate of metabolism. It regulates metabolism of carbohydrates, proteins and fats in the body so as to provide the best balance for growth. It increases the production of heat in the body.
What is simple goitre? How is it caused? Can it be cured? How?
Simple goitre is a disease condition characterized by swelling in the neck due to the enlargement of the thyroid gland.
Simple goitre is caused by the deficiency of iodine. Yes, goitre can be cured. Administering iodine orally with food and water can cure simple goitre.
Where do we find instances of goitre usually?
Goitre is an endemic disease. Goitre is usually found in areas where iodine is less in soil and
Why is goitre called an endemic disease?
Any disease that is confined to certain places or regions is called an endemic disease. Goitre is commonly found in hilly regions where there is very little iodine in water. Hence goitre is called an endemic disease.
What is the consequence of low intake of iodine in our diet?
Low intake of iodine in our diet may affect the functioning of thyroid gland. The production of thyroxin hormone may be reduced. This will affect the metabolism of carbohydrates, proteins and fats. This may also lead to goitre.
Why is the use of iodised salt advisable?
Iodine is necessary for the thyroid gland to make thyroxin hormone. Thyroxin regulates carbohydrates, proteins and fat metabolism in the body so as to provide the best balance for growth. If iodine is deficient in our diet, there is a possibility that we might suffer from goitre. The thyroid gland enlarges causing swelling in the neck.
Iodised common salt contains proper content of iodine and hence its use contributes to the proper functioning of the thyroid gland. Therefore, the use of iodised salt is recommended.
What is pituitary gland? What hormones does it secrete?
A pea-sized endocrine gland located at the base of the brain beneath the hypothalamus in a body cavity at the base of the skull is called pituitary gland. The pituitary gland secretes several hormones like thyroid stimulating hormone, growth hormone, ACTH etc.
Name the ‘growth hormone ’ secreted by the pituitary gland. Why is it called so?
A hormone called STH secreted by pituitary is called the growth hormone. This hormone is called the ‘growth hormone’ because it influences the rate of both physical and mental growth of the body.
What is gigantism and dwarfism?
Abnormal growth causing excessive height due to over-secretion of the growth hormone by the pituitary glands is called gigantism. An abnormally short stature due to the under-secretion of the growth hormone is called dwarfism.
An adult has grown to about 7 feet. He has long legs and long arms. His jaws and nose are disproportionately grown. What disease is he suffering from? What is it due to?
The person with the symptoms mentioned above is most likely to be suffering from gigantism. This means the person is unusually tall. Excessive secretion of the growth hormone by the pituitary gland causes this condition.
What are androgens? Name the most common male sex hormone.
The sex hormones secreted by testis are called androgens. The most common male sex hormone is called testosterone.
Mention the function of testosterone.
Testosterone is a male sex hormone. It is responsible for the appearance of the secondary sexual characteristics in males. The secondary sexual characteristics such as appearance of beard, moustache and low pitch voice etc., appear at puberty in boys.
What are oestrogens? What is the function of oestrogens?
The female sex hormones produced by the ovaries are called oestrogens.
Oestrogens are responsible for the development of secondary sexual characteristics in females at puberty. These characteristics include feminine voice, soft skin, development of uterus and mammary glands etc.
What is islet of Langerhans? Mention the hormones secreted by it.
A small group of cells of the endocrine pancreas are together called islet of Langerhans. The hormones secreted by the islet of Langerhans are insulin and glucagon.
What is the function of insulin?
Insulin promotes the conversion of excess glucose in the blood into glycogen for storage in liver and muscle. This helps to maintain the sugar level in the blood.
A person aged about 30 years is excreting sugar in urine. What disease does he have? What is the disease due to?
The person is having diabetes mellitus. The disease is due to insufficient production of insulin.
Why are some patients of diabetes treated by sivins injections of insulin?
Diabetes is a disease condition caused by insufficient production of insulin hormone by the pancreas. Insufficient production of insulin results in raised sugar levels in the blood, which can have serious health consequences in the long run. To avoid complications of diabetes, patients take insulin injections and maintain blood sugar within the desirable range.
What is the treatment for diabetes mellitus?
Diabetes mellitus can be controlled by regular physical exercise, diet restrictions, drugs that stimulate the pancreas and utilization of blood glucose. In some chronic diabetic patients the administration of insulin injections becomes necessary to control the blood glucose level.
A person is subjected to blood glucose test. It is found that the glucose level in the blood had increased beyond normal limits and the person was also complaining of frequent urination,
- What disease is the person suffering from?
- What hormone should be administered to control this disease?
- The person is suffering from diabetes mellitus.
- The disease can be controlled by administering insulin.
What is adrenaline? Mention its functions.
Adrenaline is an important hormone secreted by the adrenal gland. Adrenaline is produced in excess at times of fear, anger or any other emotional stress. It helps to prepare the body to face emergency situations. Adrenaline brings about co-ordination of several events like increased heart beat, rate of respiration, dilation of pupils and so on during emergency situations.
How does our body respond when adrenaline is secreted into the blood?
Adrenal gland secretes adrenaline hormone directly into the blood especially during emergencies. When this happens, heartbeat increases and hence supplies more oxygen to the muscles. This results in increased rate of breathing, and higher blood pressure. This enables the person to fight or face the emergency situation.
Name the following:
- The endocrine gland located in the brain that secretes growth hormone.
- The organ that secretes both digestive enzymes and hormones.
- The endocrine gland located on the top of kidneys.
- The endocrine gland that secretes testosterone hormone.
- Pituitary gland.
- Adrenal gland.
State the differences between endocrine system and nervous system.
|1. This system operates through chemical signals.
|This system operates through electrical signals.
|2. The system consists of a group of glands whose secretions are directly let into the blood stream.
|This system consists of sense organs, brain, spinal cord, nerves, muscles and glands.
Compare and contrast nervous and hormonal mechanisms for control and coordination in
|1. Nervous system is involved.
|Endocrine glands are involved.
|2. Messages are transferred in the form of electrical impulses.
|Messages are transferred in the form of chemicals called hormones.
|3. The response time is very short.
|Here response time is very long.
|4. Nerve impulses are not specific in their action.
|Each hormone has specific actions on target organs.
|5. The flow of information is rapid.
|The flow of information is very slow.
Why is adrenaline known as emergency hormone?
Adrenaline is the hormone secreted at the time of emergency or stress and regulates heartbeat and oxygen level in the body in these conditions. Hence it is known as emergency hormone.
Fill In The Blanks
1. The brain and the spinal cord will together constitute the Central Nervous System
2. A nerve cell is called neuron
3. Goitre is caused by the deficiency of iodine
4. The chemical secretions of endocrine glands are called hormones
5. Deficiency of insulin hormone causes diabetes
6. A substance that inhibits growth in plants is abscisic acid
7. The tissue made of an organized network of neurons is nervous tissue
8. The endocrine gland that produces growth hormone is pituitary gland
Multiple Choice Questions
Which of the following is a plant hormone?
The gap between two neurons is called a
In a synapse, chemical signal is transmitted from
(A) axonal end of one neuron to dendritic end of another neuron
(B) dendritic end of one neuron to axonal end of another neuron
(C) axon to cell body of the same neuron
(D) cell body to axonal end of the same neuron
(A) axonal end of one neuron to dendritic end of another neuron
The brain is responsible for
(B) regulating heart beat.
(C) balancing the body.
(D) all of the above.
(D) all of the above.
The organ that receives a stimulus from the surroundings is called
In higher order animals, control and coordination is achieved with the help of
(B) nervous system
(C) endocrine system
(D) both (B) and (C)
(D) both (B) and (C)
The central nervous system in human beings consists of
(A) brain and nerves
(B) brain and spinal cord
(C) spinal cord and nerves
(D) brain, spinal cord and nerves
(B) brain and spinal cord
The structure that controls reflex action is
(A) medulla oblongata
(C) spinal cord
(C) spinal cord
The bony case that protects the brain is called
Which is not a reflex action?
(A) Swallowing of food
(B) Shivering in cold
(C) Salivation at the sight of food
(D) Closure of eyes to a flashlight
(A) Swallowing of food
The growth of the pollen tube towards ovules is an instance of
After travelling through the nerve cell, the nerve impulse gets converted to
(A) chemical signal
(B) electrical signal
(C) mechanical signal
(D) electronic signal
(A) chemical signal
Which of the following is not an involuntary action?
(C) Heart beat
The hormone that triggers the fall of mature leaves and fruits from plants is
(B) abscisic acid
(B) abscisic acid
The movement of a plant part in the direction of gravity is known as
Olfactory receptors detect
The hormone that determines the ‘fight or flight’ response in our body is
(B) Growth hormone
What is the correct direction of flow of electrical impulses?
The growth of stem in the upward direction is an example of
(B) negative hydrotropism
(C) positive geotropism
(D) negative geotropism
(D) negative geotropism
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
(C) amount of water in cells
In reflex action, the reflex arc is formed by
(A) Brain – spinal cord – muscles
(B) Receptor – spinal cord – effector
(C) Muscles – receptor – brain
(D) Effector – spinal cord – receptor
(B) Receptor – spinal cord – effector
22. The incorrect statement about insulin among the following is
(A) Insufficient secretion of insulin will cause diabetes.
(B) It is produced from pancreas.
(C) It regulates blood sugar level.
(D) It regulates growth and development of the body.
(D) It regulates growth and development of the body.
Which pair among the following is mismatched?
(A) Cerebrum – Memory
(B) Medulla oblongata – Temperature regulation
(C) Cerebellum – Posture and equilibrium of the body
(D) Olfactory lobes – Receive and interpret smell
(B) Medulla oblongata – Temperature regulation
Dwarfism is the result of
(A) excessive secretion of thyroxin
(B) under-secretion of growth hormone
(C) under-secretion of adrenaline
(D) excessive secretion of growth hormone
(B) under-secretion of growth hormone
Match The Following
|a. Pituitary gland
|4. Growth hormone
|d. Adrenal gland
|e. Tear gland
|f. Thyroid gland
1 – d, 2 – g, 3 – f, 4 – a, 5 – c, 6 – b.
|a. Promotion of cell division
|b. Falling of old leaves
|c. Growth of stem
|4. Abscisic acid
|d. Pollination in flowers
|e. Elongation of cells
1 – e, 2 – c, 3 – a, 4 – b.
|1. Carries involuntary quick responses
|a. Peripheral nervous system
|2. Controls voluntary and conscious thinking
|3. Maintains precision in the voluntary actions and balance of the body
|c. Reflex Arc
|4. Facilitates communication between central nervous system and other body parts
|g. Fore brain
1 – b, 2 – g, 3 – f, 4 – a.