Control And Coordination

Shoots of a plant always grow upwards i.e. they grow away from the earth whereas the roots of a plant grow downwards in the earth i.e. they grow towards the earth.

The shoots will move towards the direction of sunlight and roots will move away from the sunlight.

Adrenaline is the hormone secreted by adrenal glands.

Following are its functions:

•It acts on heart and due to this heart starts beating faster. Due to this fast beating more blood is supplied to muscles and ultimately they get more oxygen.

•The blood supply is diverted from digestive system and skin due to contraction of muscles around these small arteries.

•Breathing rate is also increased due to contraction of diaphragm and ribs.

All these functions then contribute to fight a person with difficult situations and to deal with them.

(a) Growth hormone is synthesized in Pituitary glands in case of man.

(b) Growth hormone is synthesized in plants at the tip of the shoot.

(a) Abscisic acid is the hormone in the plants that stop the growth during extremely dry season.

(b) Cytokinins are present in greater concentration in fruits and seeds.

Brain receives the information from different neurons which are connected in spinal cord and then after thinking process brains sends signals to muscles for further movement.

Hormones secreted by plants are known as phytohormones.

ABA- Abscisic acid

Function- Abscisic acid is the hormone which restricts the growth of the plant. Due to this hormone wilting of leaves occurs.

Iodised salt provides iodine. Iodine is very much essential for the synthesis of thyroxine hormone. This thyroxine hormone is necessary for regulation of the metabolism carbohydrates, proteins and fats and thus balances the growth. If there is lack of iodine in our body enough thyroxine is not synthesised and the person suffers from goitre.

Therefore, it is always advised to take iodised salt.

Chemotropism in the plants led to the growth of pollen tubes towards the ovules and thus helps in fertilisation of plants and helps in reproduction process.

Auxin is the plant growth hormone that is synthesized at the shoot tip.

Yes, it is true that shoot of a plant bends towards the light during its growth and it is due to the presence of this auxin growth hormone. In the presence of sunlight, the auxin present in the stem starts breaking down due to which the concentration of auxin in the stem which is away from sunlight is more while those part of stem which is towards sunlight has low level of auxin. The cells with high level of auxin grow and the part having low level of auxin does not grow and therefore, stem of growing plant bend toward sunlight.

Following picture depicts the phenomenon:

This art is known as reflex action. Following is the diagram that traces the events of reflex action:

(i) Riding bicycle- Cerebellum which is a part of hindbrain controls riding of cycle.

(ii) Centre associated with hunger- Hypothalamus part of forebrain is the center associated with hunger.

(iii) Swallowing- Medulla oblongata of hindbrain is associated with the swallowing process.

(iv) Visual analysis- Forebrain is associated with the visual- analysis.

Hormones are the chemical messengers which are directly secreted into blood by ductless glands also known as endocrine gland and act on different distant organs.

Thyroxine is the hormone secreted by the thyroid gland. This hormone regulates the metabolism of carbohydrates, fats and proteins. By regulating the metabolism it provides best balanced growth to the body.

Nastic movements- These are nondirectional movements which takes place in living parts of plant due to the stimulus like temperature, amount of water etc.

For example- Whenever there is excess amount of water stomata gets opened. This is a nondirectional movement which takes place due to presence of excess water.

Curvature movements- These are directional movements which take place due to stimulus like light, some chemicals etc.

For example- Shoot of a plant moves toward the direction of light. Here the movement is directional due to presence of light in a particular direction.

Transmission of impulse from one neuron to the other takes place at the synapse between two neurons.

Brain and spinal cord are the two main organs of central nervous system.

Spinal cord plays a major role in sending command to muscles to act without involving thinking process.

The phenomenon involved is reflex action.

Hormone secreted by pituitary gland- Growth hormone

Function of growth hormone- This growth regulates the growth and development of body.

Walking is a voluntary action which does not require any stimulus to proceed and involves thinking process whereas reflex action is the action which takes place in response to certain stimulus like touch to the burning object, and it does not involve thinking process. This action takes place in very small time and does not involve thinking. No time period is associated with walking, it completely depends on the person’s choice.

Phototropism- It is the change in movement of plant that takes place due to the presence of light.

Following activity can be performed in order to observe

Phototropism:

•Take a small plant grown in a conical flask filled with water.

•Place it into a cardboard box which is open from one side.

•Now, place it near a window in such a way that the open side of the cardboard is towards the window from where light will come.

•Allow it to be there for 3-4 days.

•Now observe for the change in the plant.

•Change in the movement of shoot and root will be observed. The shoot will move towards the sunlight and root will move away from it.

(a)

(b)

(a) Medulla oblongata- It controls involuntary action like blood pressure, salivation, vomiting etc.

(b) Cerebellum- This is a part of hindbrain which is responsible for the voluntary actions that we do very precisely. For example- when we walk in a straight line.

This part also controls posture and balance of the body.

Hormones secreted by plants are known as phytohormones.

For example-

•Auxin- This is the growth hormone secreted by the tip of the shoot of the plant and promotes the growth of the plant.

•Abscisic acid- This hormone restricts the growth of the plant. It is responsible for the wilting of leaves.

•Gibberellins- It promotes the growth of the stem of the plant.

•Cytokinin- This hormone promotes the cell division process. It is present in those areas where cell division takes place at a higher rate.

(a) Feedback mechanism- This mechanism is for the regulation of the hormone secretion as we require hormones to be secreted in précised quantities. So, what happens is whenever we require the hormone to be secreted in our body there is an activator which activates the particular gland and hormone is secreted. Whenever we don’t require there is an inhibitor which inhibits the release of hormone according to requirement of body. This process is called feedback mechanism.

For example- When blood sugar levels start rising pancreas cells start secreting insulin and as the levels are normal they do not secrete insulin.

(b) Geotropism- This refers to the directional movement that takes place in plants due to gravitational pull. As we know that stems of a plant always move toward upwards i.e. away from earth and opposite to gravitational pull and roots moves downwards inside the earth according to the gravitational pull. This upward movement of stem and downward movement of root is due to geotropism.

(c) Thigmotropism- This refers to the directional movement that takes place due to touch as some plants are mechanosensitive. For example- Tendrils are very much sensitive to touch. As they come in contact with any kind of support in that particular part growth rate is retarded while in parts away from it there is higher growth due to rapid cell division in that part.

Due to this reason, only the tendrils get circled around the object. So, this directional movement that the plant exhibit due to touch is termed as thigmotropism.

(i) The significance of the reflex arcs is their efficiency that they exhibit during quick responses. Reflex arc work as a very efficient method whenever we lack the true thinking processes.

(ii) The significance of reflex action is the protection that we get due to reflex action against any stimulus. Reflex actions are quick responses that we give against any stimulus which can cause harm to us. If we don’t have such quick responses we may get armed badly.

For example- If someone touches a flame and does not exhibit any quick response due to reflex action then that particular person will definitely get burnt as thinking processes and then giving a response are not so fast processes and provide enough time for harm.

(iii) Adrenaline hormone is the stress hormone. Due to the release of this hormone our heart starts beating faster due to which more blood is supplied to the muscles, Supply of blood is diverted from digestive system, skin to the muscles, breathing rate is also increased. Due to all this our body gets prepared to deal with that stressful situation and help us to decide whether we are going to fight the situation with the complete energy or will flight from there utilizing the energy produced due to release of stress hormone.

Basically, we can say that this hormone helps us to deal to difficult stressed situations.

(i) Spinal cord is protected with the help of the vertebral column.

(ii) Brain is protected due to presence of a bony cavity which we call as skull in which brain is placed. This bony cavity is filled with a fluid which absorbs the shock and thus prevents the damage that may be caused to brain.

Firstly the stimulus is received with the help of dendrites, after that they are transmitted to cyton, and then they travel through the axon and at the end reaches to the terminal branches from where they are transmitted to dendrites of cyton of another neuron as depicted in the option (c).

Iodine is essential for the synthesis of thyroxine. Therefore statement (a) is not true about thyroxine.

Growth hormone is responsible for the growth of the organism. Whenever the hormone is secreted in fewer amounts it leads to retarded growth and ultimately to dwarfism.

Changes in puberty are associated with the secretion of oestrogen and testosterone. Oestrogen is secreted from ovary in females and testosterone is secreted in males from testes.

Therefore, correct statement is (c).

Iodine is required for the synthesis of thyroxine hormone. All other hormones are not required iodine for their synthesis.

Insulin is the hormone which is secreted by pancreas and regulates the sugar level of blood and its deficiency lead to diabetes. It has nothing to do with the growth and development.

Therefore, (b) is incorrect statement about insulin.

Adrenaline hormone is secreted from adrenal gland. Therefore (a) is mismatched pair.

Shape of guard cells changes due to change in the amount of water in cells. Whenever there is excess of water cell becomes turgid and guard cells get opened for transpiration to take place. Also, when water is not in excess amount guard cells remains closed.

Therefore, shape of guard cells is determined by amount of water in cells.

Whenever any part of the pea tendril comes in contact with the support they start growing slowly whereas part away from it grows rapidly.

Therefore option (c) is correct.

Growth of pollen tubes is a directional movement which takes place due to the chemical secretion of the ovule. Therefore, growth of pollen tubes towards ovules is due to chemotropism.

Given statement is false because at the axonal end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the dendritic end of another neuron.

Medulla is present in the hindbrain and controls the involuntary action. Therefore, correct option is (c).

Chewing is an action which person performs according to his/her will and involves skeletal muscles. Therefore, chewing is an involuntary action.

When a person will suffer from severe cold he or she will not be able to detect the smell of agarbatti or a perfume because during severe cold the olfactory receptors of the person get affected due to which he/she can’t recognise any kind of smell. All other receptors for taste, touch and vision can’t get affected in severe cold. So, they can easily detect anything related to taste, sight and touch.

Therefore, correct option is (b).

Statements (ii) and (iii) are wrong in their sense because sensory neurons carry signals from receptors to spinal cord and motor neurons carry signals from spinal cord to the muscles. Statement (i) and (iv) are true and therefore correct option is (c).

All other statements except (ii) and (iii) are incorrect because forebrain is responsible for thinking process and cerebellum controls posture and balance of the body. Statement (ii) and (iii) are true in their sense. Therefore, correct option is (c) (ii) and (iii).

Cerebellum part of hindbrain is responsible for posture and balance. All other options have nothing to do with the posture and balance. Therefore, correct option is (b) Cerebellum.

Medulla is the part of spinal cord which forms a connection between brain and spinal cord. From medulla spinal cord starts arising. Other part like cerebrum is for thinking activity and is no way related to arising of spinal cord. Cerebellum controls body posture and is also not related to spinal cord. Pons is above the medulla. Only medulla is attached with the spinal cord and this is depicted from the following diagram:

Therefore, correct option is (b) Medulla.

Gustatory receptors are present on the tongue which is a sense organ and detects the taste.

Olfactory receptors are the receptors present in the nose which is also a sense organ and helps in detection of smell.

Therefore, correct option is (a).

Firstly the stimulus is received with the help of dendrites, after that they are transmitted to cyton, and then they travel through the axon and at the end reaches to the terminal branches from where they are transmitted to another neuron. It is also shown in following picture:

Firstly the stimulus is received with the help of dendrites, after that they are transmitted to cyton, and then they travel through the axon and at the end reaches to the terminal branches from where they are transmitted to dendrites of another neuron. It is also shown in following picture:

Therefore, option (d) is correct.

The conversion of electric signal to chemical signal takes place at axonal end because it transmits the impulse to the other neuron using chemical messengers like acetylcholine. For transmission to other neuron, chemicals are being secreted by axonal ends which by crossing the synapse enter dendrites of another neuron as electric impulse.

Therefore, correct option is (b).

First of receptors of the part where stimulus acts receive the stimulus and with the help of sensory neuron transmits signals to the spinal cord. Through spinal cord, this information is received by the brain which directs motor neuron for the further movement. Following picture also depicts the same phenomenon:

Therefore, correct option is (d).

All other glands remain present in paired form. Only pituitary gland is present in single form.

Following picture depicts the paired nature of Adrenal, Testes, ovary and unpaired nature of pituitary gland:

Therefore, correct option is (c).

Junction between two neurons from where impulse is transmitted from one neuron to the other neuron is called synapse. All other options are wrong in context to junction between two neurons.

Therefore, correct option is (d).

Given statement is true.

Explanation- Midbrain and hindbrain control involuntary actions. Actions like blood pressure, vomiting, salivation, sleep etc are controlled by the medulla part of hind brain. Reflexes associated with the vision and hearing is controlled by midbrain.

All the voluntary actions are controlled by Forebrain.

Therefore, given statement is true.

Given statement is true.

Explanation- Hindbrain consists of three parts- Pons, Medulla and Cerebellum.

Given statement is false.

Explanation- Blood pressure, salivation and vomiting are controlled by the medulla oblongata. Therefore, given statement is false.

Given statement is false.

Explanation- Cerebellum maintains posture and balance of the body. Therefore, the given statement is false.

Given statement is false.

Explanation- Insulin helps in the regulation of the blood sugar level. Therefore, the given statement is false.

Given statement is false.

Explanation- Deficiency of iodine in our diet causes goiter. Therefore, the given statement is false.

Given statement is false.

Explanation- Symptoms of goiter lead to swelling in neck. Therefore, given statement is false.

Given statement is true.

Explanation- Pituitary gland located in the brain secretes the growth hormone. No other gland secretes growth hormone. Therefore, given statement is true.

Given statement is true.

Explanation- Abscisic acid with their secretion prevents the further growth of plant and thus inhibits it. Therefore, given statements is true.

Given statement is true.

Explanation: Since here directional movement take place in pollen tubes due to presence of ovules. This is an example of chemotropism and is true.