Lesson: Control and Coordination

Question 1

Which of the following is a plant hormone?

(a) Insulin

(b) Thyroxin

(d) Cytokinin

Solution:

(d)

Question 2

The gap between two neurons is called a

(a) Dendrite

(b) Synapse

(d) Impulse

Solution:

(b)

Question 3

The brain is responsible for

(a) Thinking

(b) Regulating the heartbeat

(d) All of the above

Solution:

(d)

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?

Solution:

Functions of receptor in our body:

· They sense external stimuli such as heat or pain and pass on the information to the brain. The brain, in turn, instructs related organ to take necessary action.

· They also trigger an impulse in the sensory neuron which sends message to the spinal cord.

When receptors do not function properly, the brain does not get signals regarding external stimuli. This may lead to accident or bodily damage. For example, if we accidentally touch any hot object, then our hands might get burnt as non-functional receptors cannot perceive external stimuli of heat and pain.

Question 5

Draw the structure of a neuron and explain its function.

Solution:

Neurons are also known as nerve cells. They are the structural and functional units of our nervous system. A neuron is the largest cell in a body that carries messages across large distances in a body. The messages are in the form of electrical signals called electrical impulses or nerve impulses.

The structure of a neuron is shown below:

The components of a neuron are:

· Dendrites: Dendrites are tree-like extensions which receive information from a body part or other neurons and transmit electric signals to a cell body.

· Cell body: Cell body (also known as soma) is the place where all the dendrites are joined. It produces all necessary proteins for other parts of a neuron.

· Nucleus: Nucleus is the most important organelle which contains genes that consist of DNA.

· Axon hillock: Axon hillock is part of a cell body that receives signals from all dendrites and creates the electric impulse which travels down the axon.

· Axon: Axon is a long tube which carries electric signals away from a cell body towards the terminal button and transmits them to other neurons.

· Myelin sheath: Myelin sheath is made up of proteins and fats and is responsible for protection and insulation of neurons.

· Synaptic terminals: Synaptic terminals are terminal buttons that are located at the end of a neuron and are responsible for sending signals on to other neurons

· Synapse: Synapse is a small gap at the end of a neuron that allows information to pass from one neuron to the next muscle or gland.

Question 6

How does phototropism occur in plants?

Solution:

Growth movement in plants in response to light stimulus is called phototropism. In plants, shoots bend towards a source of light and roots bend away from the light source. Therefore, shoots show positive phototropism whereas roots show negative phototropism.

Question 7

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

Solution:

The nerves from all over the body meet in a bundle inside the spinal cord. In case of spinal cord injury, there will be total shutdown of signal transmission from rest of the body to the brain. Therefore, messages from the brain too will not be conducted to any organ.

Question 8

How does chemical coordination occur in plants?

Solution:

Chemical coordination occurs in plants through plant hormones. Different plant hormones help to coordinate growth, development and responses to the environment.

Examples:

· Auxin promotes cell growth.

· Gibberellin promotes stem growth.

· Cytokinins promote cell division.

· Abscisic acid inhibits growth, wilting and shedding of leaves etc.

· Ethylene helps fruits ripen by making them softer and sweeter.

Question 9

What is the need for a system of control and coordination in an organism?

Solution:

There are various organs in an organism. For survival of an organism, these organs must work together in a proper manner. In human beings, the nervous system and the endocrine system work together for control and coordination. Hormones are responsible for overall growth and development of an organism, and the central nervous system is responsible for daily decision that includes voluntary and involuntary actions.

Question 10

How are involuntary actions and reflex actions different from each other?

Solution:

Involuntary actions: These actions are part of routine activities. They happen in involuntary organs. They are directly under the control of brain.

Reflex actions: These actions are in response to a sudden danger or action and happen in voluntary organs. They are not under the control of brain.

Question 11

Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Solution:

Nervous System Mechanism:

· It is fast

· It is facilitated by neuro transmitters

· The information is transmitted in the form of electric impulses

Hormone System Mechanism:

· It is slow

· It facilitates hormonal control

· The information is transmitted in the form of chemical messengers

Question 12

What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Solution:

The movement in a sensitive plant is facilitated by chemical control and the movement in our legs is facilitated by nervous control.

Lesson: Control and Coordination

Question 1

Which of the following statements is correct about receptors?

(a) Gustatory receptors detect taste while olfactory receptors detect smell

(b) Both gustatory and olfactory receptors detect smell

(d) Olfactory receptors detect taste and gustatory receptors smell

Solution:

Question 2

Electrical impulse travels in a neuron from:

(a) Dendrite → axon → axonal end → cell body

(b) Cell body →dendrite →axon → axonal end

(d) Axonal end →axon → cell body → dendrite

Solution:

Question 3

In a synapse, chemical signal is transmitted from:

(a) Dendritic end of one neuron to axonal end of another neuron

(b) Axon to cell body of the same neuron

(d) Axonal end of one neuron to dendritic end of another neuron

Solution:

Question 4

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

(a) Cell body

(b) Axonal end

(d) Axon

Solution:

Question 5

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

(a) Receptors → Muscles → Sensory neuron → Motor neuron → Spinal cord

(b) Receptors → Motor neuron → Spinal cord → Sensory neuron → Muscle

(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle

Solution:

Question 6

Which of the following statements are true?

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

(ii) Sensory neurons carry signals from spinal cord to muscles.

(iii) Motor neurons carry signals from receptors to spinal cord.

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

(a) (i) and (ii)

(b) (i) and (iii)

(d) (i), (ii) and (iii)

Solution:

Question 7

Which of the following statements are true about the brain?

(i) The main thinking part of brain is hind brain.

(ii) Centres of hearing, smell, memory, sight etc. are located in fore brain.

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

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

(a) (i) and (ii)

(b) (i), (ii) and (iii)

(d) (iii) and (iv)

Solution:

Question 8

Posture and balance of the body is controlled by:

(a) Cerebrum

(b) Cerebellum

(d) Pons

Solution:

Question 9

Spinal cord originates from:

(a) Cerebrum

(b) Medulla

(d) Cerebellum

Solution:

Question 10

The movement of shoot towards light is:

(a) Geotropism

(b) Hydrotropism

(d) Phototropism

Solution:

Question 11

The main function of abscisic acid in plants is to:

(a) Increase the length of cells

(b) Promote cell division

(d) Promote growth of stem

Solution:

Question 12

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

(a) Auxin

(b) Gibberellins

(d) Abscisic acid

Solution:

Question 13

Iodine is necessary for the synthesis of which hormone?

(a) Adrenaline

(b) Thyroxin

(d) Insulin

Solution:

Question 14

Choose the incorrect statement about insulin.

(a) It is produced from pancreas

(b) It regulates growth and development of the body

(d) Insufficient secretion of insulin will cause diabetes

Solution:

Question 15

Select the miss-matched pair:

(a) Adrenaline: Pituitary gland

(b) Testosterone: Testes

(d) Thyroxin: Thyroid gland

Solution:

Question 16

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

(a) protein composition of cells

(b) temperature of cells

(d) position of nucleus in the cells

Solution:

Question 17

The growth of tendril in pea plants is due to_____________.

(a) Effect of light

(b) Effect of gravity

(d) Rapid cell divisions in tendrillar cells in contact with the support

Solution:

Question 18

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

(a) Hydrotropism

(b) Chemotropism

(d) Phototropism

Solution:

Question 19

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

(a) Phototropism

(b) Geotropism

(d) Hydrotropism

Solution:

Question 20

What triggers the fall of mature leaves and fruits from plants?

(a) Auxin

(b) Gibberellin

(d) Cytokinin

Solution:

Question 21

Which of the following statements about transmission of nerve impulse is incorrect?

(a) Nerve impulse travels from dendritic end towards axonal end.

(b) At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron.

(c) The chemicals released from the axonal end of one neuron cross the synapse and generate a similar electrical impulse in a dendrite of another neuron.

(d) A neuron transmits electrical impulses not only to another neuron but also to muscle and gland cells.

Solution:

Question 22

Involuntary actions in the body are controlled by ____________.

(a) Medulla in fore brain

(b) Medulla in mid brain

(d) Medulla in spinal cord

Solution:

Question 23

Which of the following is not an involuntary action?

(a) Vomiting

(b) Salivation

(d) Chewing

Solution:

Question 24

When a person is suffering from severe cold, he or she cannot ___________.

(a) Differentiate the taste of an apple from that of an ice cream

(b) Differentiate the smell of a perfume from that of an agarbatti

(d) Differentiate a hot object from a cold object

Solution:

Question 25

What is the correct direction of flow of electrical impulses?

Solution:

Question 26

Which statement is not true about thyroxin?

(a) Iron is essential for the synthesis of thyroxin.

(b) It regulates carbohydrates, protein and fat metabolism in the body.

(d) Thyroxin is also called thyroid hormone.

Solution:

(a)

Question 27

Dwarfism results due to _______________________.

(a) Excess secretion of thyroxin

(b) Less secretion of growth hormone

(d) Excess secretion of growth hormone

Solution:

(b)

Question 28

Dramatic changes of body features associated with puberty are mainly because of secretion of ________________________.

(a) Oestrogen from testes and testosterone from ovary.

(b) Estrogen from adrenal gland and testosterone from pituitary gland.

(d) Testosterone from thyroid gland and estrogen from pituitary gland.

Solution:

(c)

Question 29

A doctor advised a person to take an injection of insulin, because _____________.

(a) His blood pressure was low

(b) His heart was beating slowly

(d) His sugar level in blood was high

Solution:

(d)

Question 30

What is the name of the hormone which increases fertility in males?

(a) Oestrogen

(b) Testosterone

(d) Growth hormone

Solution:

(b)

Question 31

Which of the following endocrine glands is unpaired?

(a) Adrenal

(b) Testes

(d) Ovary

Solution:

(c)

Question 32

Junction between two neurons is called

(a) Cell junction

(b) Neuro muscular junction

(d) Synapse

Solution:

(d)

Question 33

In humans, the life processes are controlled and regulated by:

(a) Reproductive and endocrine systems

(b) Respiratory and nervous systems

(d) Nervous and endocrine systems

Solution:

(d)

Question 34

Label the parts (a), (b), (c) and (d) and show the direction of flow of electrical signals in the figure given below:

Solution:

(a) Sensory neuron

(b) Spinal cord (CNS)

(d) Effector = Muscle in arm

Question 35

Name the plant hormones responsible for the following:

(a) Elongation of cells

(b) Growth of stem

(d) Falling of senescent leaves

Solution:

(a) Auxin

(b) Gibberellin

(d) Abscisic acid

Question 36

Label the endocrine glands in the given figure.

Solution:

(a) Pineal gland

(b) Pituitary gland

(d) Thymus

Question 37

In the given figure, (a), (b) and (c), which appears more accurate and why?

Solution:

Figure (a) is more appropriate.

In a plant, shoots are negatively geotropic. Hence, they grow upwards opposite to the direction of gravity. On the other hand, roots grow in the direction of gravity and thus, they are positively geotropic.

Question 38

Label the parts of a neuron in the given figure.

Solution:

(a) Dendrite

(b) Cell body

(d) Nerve ending

Question 39

Match the terms of Column (A) with those of Column (B).

Column (A)	Column (B)
(a) Olfactory receptors	(i) Tongue
(b) Thermo receptors (temperature receptors)	(ii) Eye
(c) Gustatory receptors	(iii) Nose
(d) Photoreceptors	(iv) Skin

Solution:

(a) $—$ (iii)

(b) $—$ (iv)

(d) $—$ (ii)

Question 40

What is a tropic movement? Explain with an example.

Solution:

The movement of a plant in the direction of external stimuli is called tropic movement. Such movements can be either towards the stimulus, or away from it. The movement of a plant is said to be positive if it is directed towards the stimulus and negative if is directed away from the stimulus.

Example: Bending of shoots towards light and bending of roots away from light are examples of positive and negative phototropism, respectively.

Question 41

What will happen if intake of iodine in our diet is low?

Solution:

Following things might occur if iodine intake in our diet is low:

(a) The release of thyroxin from thyroid gland will be less.

(b) Iodine deficiency will affect the carbohydrate, protein and fat metabolism and thus slow down the growth of the body.

Question 42

What happens at the synapse between two neurons?

Solution:

Electrical signal on reaching the axonal end of one neuron causes the axon bulb to release a chemical substance. This diffuses across the synapse and stimulates the dendritic end of the next neuron. These dendrites then generate another electrical signal to their cell body to be carried along the axon.

Question 43

Answer the following:

(a) Which hormone is responsible for changes noticed in females at puberty?

(b) Dwarfism results due to deficiency of which hormone?

(d) Iodine is necessary for the synthesis of which hormone?

Solution:

(a) Oestrogen

(b) Growth hormone

(d) Thyroxin

Question 44

Answer the following:

(a) Name the endocrine gland associated with brain?

(b) Which gland secretes digestive enzymes as well as hormones?

(d) Which endocrine gland is present in males but not in females?

Solution:

(a) Pituitary

(b) Pancreas

(d) Testes

Question 45

Draw the structure of a neuron and explain its function.

Solution:

Neurons are also known as nerve cells. They are basic building blocks of our nervous system. They are responsible for transmitting and receiving signals from different parts of our body.

The structure of a neuron is shown below:

The components of a neuron are:

· Dendrites: Dendrites are tree-like extensions which receive information from a body part or other neurons and transmit electric signals to the cell body.

· Cell body: Cell body (also known as soma) is the place where all dendrites are joined. It produces all necessary proteins for other parts of a neuron.

· Nucleus: Nucleus is the most important organelle which contains genes that consist of DNA.

· Axon hillock: The axon hillock is part of a cell body that receives signals from all dendrites and creates electric impulse which travels down the axon.

· Axon: Axon is a long tube which carries electric signals away from a cell body towards the terminal button and transmits them to other neurons.

· Myelin sheath: Myelin sheath is made up of proteins and fats and is responsible for protection and insulation of neurons.

· Synaptic terminals: Synaptic terminals are the terminal buttons that are located at the end of a neuron and are responsible for sending signals on to other neurons

· Synapse: Synapse is a small gap at the end of a neuron that allows information to pass from one neuron to the next muscle or gland.

Question 46

What are the major parts of a brain? Mention the functions of different parts.

Solution:

Brain has three major parts namely:

· Fore-brain

· Mid-brain

· Hind-brain

Major Parts	Parts	Functions
Fore-brain	Cerebrum	· Controls voluntary actions and is the site for sensory perceptions.
	Cerebral hemispheres	· Controls intelligence and voluntary actions
	Olfactory lobes	· Centre of smell
	Diencephalon	· Has centres of hunger, thirst, etc.
	Motor areas	· Instruct muscles to do various types of jobs
Mid brain	Tectum	· Controls reflex movements of neck, head and trunk in response to visual and auditory stimuli
Mid brain	Cerebral peduncle	· Controls reflex movement of eye muscles, changes in pupil size and shape of the eye lens
Hind-brain	Pons	· Regulates respiration · Relays information between the cerebellum and the cerebrum maintaining posture and balance of the body.
	Cerebellum	· Coordinates motor functions and maintains posture and balance.
	Medulla	· Controls involuntary functions such as heart rate, breathing, etc. · Acts as a controlling centre for reflexes such as swallowing, coughing vomiting, etc.

Question 47

What constitutes the central and peripheral nervous systems? How are the components of central nervous system protected?

Solution:

The central nervous system is composed of brain and spinal cord.

The peripheral nervous system is composed of cranial nerves, spinal nerves and autonomous nervous system.

Brain is the main coordinating centre in a body. It is housed in the 7cranium. The spinal cord is a long cylindrical structure. It is enclosed in a bony cage called vertebral column. Additionally, the brain and the spinal cord are surrounded by a system of three layers called meninges. The space between these membranes is filled with a cerebrospinal fluid, which provides a cushion effect and protects the organs against mechanical shocks.

Question 48

Mention one function for each of these hormones:

(a) Thyroxin

(b) Insulin

(d) Growth hormone

(e) Testosterone.

Solution:

(a) Thyroxin regulates carbohydrate, fat and protein metabolism.

(b) Insulin regulates blood sugar level.

(d) Growth hormone regulates growth and development.

(e) Testosterone controls changes of body features associated with puberty in males.

Question 49

Name various plant hormones. Also give their physiological effects on plant growth and development.

Solution:

Plant Hormone	Physiological Effects
Auxin	· Promotes cell elongation and thus promotes growth of a plant · Plays an important role in formation of root and seedless fruit
Gibberellins	· Helps in growth of stem and flower · Helps in seed germination
Cytokinin	· Promotes cell division and thus promotes growth · Stimulates leaf expansion
Abscissic acid	· Inhibits growth and is responsible for shedding of older parts.

Question 50

What are reflex actions? Give two examples. Explain a reflex arc.

Solution:

Reflex Action:

Reflex action is a special case of involuntary movement in voluntary organs. It is a rapid automatic response to a stimulus which is not under voluntary control of the brain.

Example:

1. When we touch a hot object, we immediately move our hand away from it.

2. When we step on something sharp, we immediately move our foot away from it.

All of this happens in a flash and our organ is saved from imminent injury.

Reflex Arc:

The path through which nerve signals travel is called the reflex arc. The following flow chart and image shows the flow of signal in a reflex arc.

Receptor $�$ Sensory Neuron $�$ Relay neuron $�$ Motor neuron $�$ Effector (muscle)

The receptor is a 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 and moves the receptor away from danger.

Question 51

“Nervous and hormonal systems together perform the function of control and coordination in human beings.” Justify the statement.

Solution:

Nervous system controls and coordinates all functions in our body. However, nerves cannot reach every part of our body. So it carries out its functions in close coordination with the hormonal system to control all the parts of the body.

Nervous control is faster, whereas hormonal control is slower. Hormonal control is mainly based on feedback mechanism and based on a situation.

It tells the body to either pick up pace or slow down.

Nervous control is more of a direct control. So, both of them complement each other. Together, the nervous and hormonal systems perform the function of control and coordination in human beings.

Question 52

How does chemical coordination take place in animals?

Solution:

In animals, chemical coordination takes place through hormones. These hormones are chemical messengers. They are directly released in the bloodstream. The blood carries them to specific tissues or organs called target tissues/organs where they trigger a biochemical or physiological activity.

The hormones are of different types and perform different functions.

Question 53

Why is the flow of signals in a synapse from axonal end of one neuron to dendritic end of another neuron but not the reverse?

Solution:

The flow of signals through neurons takes place in the form of specialized chemicals. These chemicals, called neurotransmitters, can enter a neuron only through dedicated receptors located at the dendritic end but not at the axonal end. Hence, the flow of signals in a synapse happens from axonal end of one neuron to dendritic end of another neuron but not in reverse direction.

Lesson: Control and Coordination

Question 1

What is the difference between a reflex action and walking?

Solution:

A reflex action is an unconscious involuntary action. It is a rapid and automatic response to an external stimulus. On the other hand, walking is a voluntary action. It is under our control.

Question 2

What happens at the synapse between two neurons?

Solution:

A synapse is the gap between two neurons. At the synapse, electrical signals are converted into chemicals. These chemicals can easily cross the gap and pass on to the next neuron. Here it is again converted into electrical signals. The impulses or signals are transmitted in one direction only.

Question 3

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

Solution:

Cerebellum which is a part of hind brain is responsible for maintaining posture and equilibrium of a body.

Question 4

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

Solution:

When the smell of an incense stick reaches our nose, the olfactory receptors present in our nose detect it. These receptors send information to the fore-brain in the form of electrical signals. The fore-brain interprets this information, from stored memory, as the smell of an incense stick.

Question 5

What is the role of brain in reflex action?

Solution:

A brain has no direct involvement in reflex action. Reflex actions are very quick. They do not require thinking. They are mainly controlled by the spinal cord.

Question 6

What are plant hormones?

Solution:

Plant hormones:

(a) Are known as phytohormones.

(b) Are chemical substances that are secreted within a plant

There are five major types of plant hormones; auxin, gibberellins, cytokinins, abscisic acid and ethylene etc.

Question 7

How is the movement of leaves of a sensitive plant different from the movement of a shoot towards light?

Solution:

The movement of leaves of a sensitive plant is touch sensitive and does not depend on the direction of the stimulus and is growth independent. On the other hand, movement of a shoot depends on the direction of light and is known as phototropism. This movement is directional and growth dependent.

Question 8

Give an example of a plant hormone that promotes growth.

Solution:

Auxins promote stem elongation, growth and movement.

Question 9

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

Solution:

Auxin increases in concentration in part of the tendril that is away from support. This results in increased cell division in that part. Lesser auxin occurs on the side of contact as compared to the free side. As a result, auxin promotes growth on the free side and the tendrils coil around the support.

Question 10

Design an experiment to demonstrate hydrotropism.

Solution:

Experiment to demonstrate hydrotropism

Take two small beakers and label them as A and B.

(a) Take a beaker A with water.

(b) 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.

(d) Now, cover the entire set-up with a transparent plastic container so that moisture is retained.

Observation:

The roots of germinating seeds will grow towards beaker A.

This experiment demonstrates the phenomenon of hydrotropism.

Question 11

How does chemical coordination take place in animals?

Solution:

Chemical coordination in animals takes place through hormones. These hormones are chemical messengers. They are secreted by glands and directly released in the bloodstream. The blood carries them to specific tissues or organs called target tissues/organs. In the target, they trigger a biochemical or physiological activity. The hormones are of different types and perform different functions.

Question 12

Why is the use of iodised salt advisable?

Solution:

Iodine is an important constituent of the hormone thyroxine that regulates carbohydrate, fat and protein metabolism in our body.

If there is a deficiency of this hormone, it may result in enlargement of the thyroid gland. This can lead to goitre, a disease characterized by swollen neck. Therefore we should use iodised salt to avoid deficiency of thyroxine hormone.

Question 13

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

Solution:

Adrenal gland secretes adrenaline hormone when someone is in an emergency situation. It is secreted directly into the blood and is transported to different parts of a body. It increases the rate of heartbeat and breathing rate, so that more oxygen could be supplied to the muscles. It also increases blood pressure. This enables a person to fight an emergency situation.

Question 14

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

Solution:

Insulin is a hormone. It plays an important role in sugar metabolism. It converts extra sugar present in the blood into glycogen. Diabetes is caused due to poor or no secretion of insulin by pancreas. Thus, patients suffering from diabetes are given insulin injection to control their blood sugar level.

Questions

Q1	What does the thinking tissue in our body consist of?

Q2	Which endocrine gland is unpaired?

Q3	Which neurons relay the signals between sensory neuron and motor neuron?

Q4	What regulates the timing and amount of release of hormones?

Q5	What is the most important use of auxin?

Q6	Name the endocrine gland which secretes hormone and requires iodine for its synthesis.

Q7	What does the diagram given below represent?

Q8	What are hormones?

Q9	What is motor and sensory neuron?

Q10	Why must we include iodized salt in our diet?

Q11	What are phytohormones? Name any two phytohormones.

Q12	What happens when there is high glucose level in the blood?

Q13	Name the hormones responsible for lowering and increasing glucose level in blood.

Q14	What is the function of the nervous system? What is the structural and functional unit of the nervous system in multicellular organisms?

Q15	Explain reflex action and reflex arc.

Q16	Differentiate between endocrine and exocrine glands. Give examples of 3 glands that are both endocrine as well as exocrine in nature.

Q17	What are the various ways in which plants exhibit movement?

Q18	Explain the location, hormones secreted and role of the endocrine glands in human beings.

Q19	What are the limitations of electrical (nerve) impulses? How are these limitations overcome by chemical coordination? Explain the mechanism of transmission of chemical impulses.

Q20	Name the functional unit of the nervous system. What are its various types, parts and what is their respective function?

Questions

Q1	What does the thinking tissue in our body consist of?

A1	The thinking tissue in our body consists of dense networks of intricately arranged neurons.

Q2	Which endocrine gland is unpaired?

A2	Pituitary gland is an unpaired endocrine gland.

Q3	Which neurons relay the signals between sensory neuron and motor neuron?

A3	Relay neurons are the neurons which relay signals between sensory neuron and motor neuron.

Q4	What regulates the timing and amount of release of hormones?

A4	Timing and amount of release of hormones is regulated by feedback mechanism.

Q5	What is the most important use of auxin?

A5	Cell elongation and plant growth is the most important use of auxin.

Q6	Name the endocrine gland which secretes hormone and requires iodine for its synthesis.

A6	Thyroid gland is the endocrine gland which secretes hormone and requires iodine for its synthesis.

Q7	What does the diagram given below represent?

A7	The diagram represents reflex arc.

Q8	What are hormones?

A8	Hormones are chemical messengers that are derivatives of amino acids, proteins or steroids and they transport information from one set of cells (endocrine cells) to their target receptors (target cells).

Q9	What is motor and sensory neuron?

A9	Motor neuron is a nerve cell which receives information from brain, transmits it to effector organ and stimulates it to respond, whereas, sensory neuron is a nerve cell which receives the stimuli from receptor and passes the message to the brain.

Q10	Why must we include iodized salt in our diet?

A10	Iodized salt contains iodine which is required for the production of thyroxin hormone. Deficiency of thyroxin may lead to development of goitre, which is swelling in neck region due to enlargement of the thyroid gland. In order to avoid this, we must include iodized salt in our diet.

Q11	What are phytohormones? Name any two phytohormones.

A11	Phytohormones are plant hormones. They are chemical substances that are formed naturally in plants and are capable of translocation and regulating one or more physiological reactions when present in right proportion. Auxins and gibberellins are two such examples.

Q12	What happens when there is high glucose level in the blood?

A12	Due to high glucose level in blood, the pancreatic cells are induced to produce more insulin which converts glucose to glycogen.

Q13	Name the hormones responsible for lowering and increasing glucose level in blood.

A13	Insulin is a hormone which is responsible for lowering and glucagon is responsible for increasing glucose level in blood.

Q14	What is the function of the nervous system? What is the structural and functional unit of the nervous system in multicellular organisms?

Q15	Explain reflex action and reflex arc.

A15

Reflex actions are special cases of stereotyped movements in voluntary organs in the sense that they occur without the person willing them to do so. When a voluntary organ is in the vicinity of sudden danger, it instantly pulls away from the danger to save itself. For example, when your finger is pricked with a pin, you immediately withdraw your hand.

All of this happens in a flash of a moment and your hand is saved from the injury which could have happened. Even the eye blink reflex is one such example of reflex action.

Reflex Arc:

The path, through which nerves transmit signals; involved in a reflex action; from receptors to effector organ, ultimately causing the desired response is called the reflex arc.

The following flow chart shows the flow of signal in a reflex arc.

Receptor → Sensory Neuron → Relay neuron → Motor neuron → Effector (muscle)

The receptor is the organ which comes in the hazard region.

The sensory neurons collect signals from the receptor and forwards them to the relay neuron which is present in the spinal cord.

The spinal cord transmits signals to the effector via the motor neuron.

The effector comes in action and shifts 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 go up to the brain.

This is important because sending signals to the brain would take more time. Although every action is eventually controlled by the brain, the reflex action is mainly controlled at the level of spinal cord.

Q16	Differentiate between endocrine and exocrine glands. Give examples of 3 glands that are both endocrine as well as exocrine in nature.

A16

	Endocrine glands	Exocrine glands
1.	Secrete hormones	Secretes enzymes
2.	Secretion released in blood	Secretion released in ducts of glands
3.	Ducts are absent	Ducts are present
4.	Located away from the spot of action	Located near the spot of action

Some glands which act both as endocrine as well as exocrine are:

Gland	Endocrine function	Exocrine function
Pancreas	Produces insulin and glucagon hormone	Produces digestive enzyme (pancreatic amylase)
Ovaries	Produces hormone oestrogen	Produces female gametes (reproduction cells)
Testes	Produces hormone testosterone	Produces male gametes (reproductive cells)

Q17	What are the various ways in which plants exhibit movement?

A17

Movements in plants can be divided into two main types, viz. tropic movement and nastic movement.

(a) Tropic Movement:

The plant movements which are in a specific direction relative to the stimulus are called tropic movements or directional movements. Tropic movements occur as a consequence of growth of a plant part in a particular direction.

There are four types of tropic movements: geotropic, phototropic, and hydrotropic and thigmotropic.

i) Geotropic movement:

The growth movement in a plant part induced by gravity is called geotropic movement, in which, the roots usually grow in the direction of gravity showing positive geotropism and stems usually grow away from gravity, showing negative geotropism.

ii) Phototropic movement:

The growth in a plant part induced by light is called phototropic movement. For example, the growth of plant stem towards sunlight is positive phototropic movement and it happens because of a higher rate of cell division in the part of stem away from the sunlight because of which the stem bends towards the light. On the other hand, the growth of roots away from sunlight is called negative phototropic movement which happens because of the increased rate of cell division which is attained by increased secretion of the plant hormone auxin in the part away from sunlight.

iii) Hydrotropic movement:

The growth movement induced by water as in plant roots which grow in the soil towards the nearest source of water is considered to be a positive hydrotropic movement. On the other hand, the growth of stem away from water is called negative hydrotropism.

iv) Thigmotropic movement:

The growth in a plant part induced by touch is called thigmotropic movement. Such movements are seen in tendrils of climbers which move towards a source of support in order to coil around it and thereby help the plant to climb. This growth becomes possible by differential rate of cell division in different parts of the tendril due to action of auxin.

(b). Nastic movement:

Nastic movements are plant movements that take place in response to environmental stimuli but unlike tropic movements, the direction of the response is not dependent on the direction of the stimulus. That is why these are also known as non-directional movements. These movements are independent of growth. Plant cells need to change their form for this movement to happen. The movement in plants occurs in the direction opposite to the stimulus. Here is an example of the leaves of Mimosa, which when someone touches, the leaves droop.

The drooping is unrelated to the direction from which the leaves are touched. Such movements usually happen because of altering 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.

Q18	Explain the location, hormones secreted and role of the endocrine glands in human beings.

A18

The endocrine glands in human beings such as the pineal, hypothalamus, pituitary, thyroid, parathyroid, thymus, adrenal, pancreas, testes and ovary produce chemical substances which help to control and coordinate various activities in the body. The location, hormones secreted and role of the endocrine glands in human beings are tabulated below.

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

Q19	What are the limitations of electrical (nerve) impulses? How are these limitations overcome by chemical coordination? Explain the mechanism of transmission of chemical impulses.

A19

Limitations of electrical impulses are as follows:

1. Electrical (or Nerve) impulse is generated and transmitted to only those cells that are connected to the nervous tissue. Not all cells are connected to the nervous tissue. As a result, the signal fails to reach all cells.

2. Once an electric impulse is generated in a cell and transmitted, the cell takes some time to reset its mechanism before it generates and transmits a new impulse. As a result cells cannot continuously create and transmit new impulses.

Chemical coordination overcomes these limitations in the following ways:

1. Chemical compounds can reach each and every cell as they are not dependent on specialised tissues for their conduction.

2. Chemical coordination can continuously generate and transmit new impulses as there is no delay in transmission of signal through chemical compounds.

In chemical coordination the stimulated cells release a chemical compound.

This compound diffuses all around (in plants) or is transported to various body parts through circulation (in animals).

Once this compound reaches the target cell, it is recognised on the basis of presence of special molecules on the surface (receptors).

After recognition, the necessary information is transmitted to the target cell and the response is generated.

Q20	Name the functional unit of the nervous system. What are its various types, parts and what is their respective function?

A20

The nerve cell or neuron is the functional unit of the nervous system.

Neuron is a highly specialized cell which is in charge of transmission of nerve impulses.

The neuron consists of the following parts:

(a) Cyton or cell body:

The cell body or cyton is rather star-shaped; with many hair-like structures protruding out of the margin. These hair-like structures are called dendrites, which receive the nerve impulses.

(b) Axon:

This is the tail of the neuron and it ends in several hair-like structures called axon terminals. The axon terminals pass on nerve impulses.

(c) Myelin Sheath: Around the axon, there is an insulator cover called myelin sheath which insulates the axon against nerve impulses from the surroundings.

Types of Neuron

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

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

Control and Coordination C

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