COURCES/CLASS-X/SCIENCE/CHAPTER-7

CHAPTER – 7

Control and Coordination

1. In living organism, it is observed that living organism responds according to situation, surroundings, requirements etc. It is clear that there is a system which directs, control and coordinate movements and responses etc. In other words, living organisms must use systems providing control and coordination. Therefore, it is necessary to discuss about such systems which conducts all control and coordination in living organisms specially in human. The control and coordination in human beings are conducted through nervous system and hormonal system which is called endocrine system.
   

   2.1    Animal Nervous System: In animals, control and coordination are provided by nervous and muscular tissues. All information from the environment is detected by the specialized tips of some nerve cells. These receptors are usually located in sense organs of animals – (i) Ear (ii) Nose (iii) Tongue (iv) Skin (v) Eyes.
   

       The information acquired at the end of the dendritic tip of a nerve cell, sets off a chemical reaction that creates an electrical impulse. This impulse travels 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 the way nervous impulses travel in the body. Nervous tissue is made up of an organized network of nerve cells or nervous and is specialized for conducting information via electrical impulse from one part of the body to another.
   

   3.1    Reflex Action: Reflex action is an involuntary and nearly instantaneous movement in response to a stimulus. A reflex is made possible by neural pathways called reflex arcs which can act on an impulse before that impulse reaches the brain.
   

       Reflex arcs have evolved in animals because the thinking process of the brain is not fast enough. In fact many animals have very quite likely that reflex arcs have evolved as efficient ways of functioning in the absence of true though process. However, even after complex neutron networks have come into existence, reflex arcs continue to be more efficient for quick responses.
   

   4.1    Human Brain: Human brain is the main coordinating centre of the body. The brain and spinal cord constitute the central nervous system. They receive information from all parts of the body and integrate it.
   

       The brain can be divided into three basic units – (i) Forebrain (ii) Midbrain (iii) Hindbrain.
   

   (i) Forebrain: Forebrain is the largest brain division. It includes the ‘cerebrum’ which accounts for about two-thirds of the mass of the brain and covers most other brain structure. It is the most advanced part of the rain It consists of two subdivisions that is called ‘telencephalon’ & ‘diencephalon’.
   

   Function: It controls body temperature, reproductive functions, eating, sleeping, thinking, perceiving, display of emotions and evaluating sensory information etc. It has two major parts called the diencephalon and the telencephalon.
   

       (ii) Midbrain: It is also called ‘mesencephalon’ the Midbrain is the topmost part of the brainstem, the connection central between the brain and the spinal cord. It connects to both the Forebrain & Hindbrain. It forms the brainstem. It also connects to the spinal cord directly. As a result, it is known as physical connecter of between the brain and the rest of body. There are 3 main parts of the midbrain – (i) Colliculi (ii) Tegmentum & (iii) Cerebral penduncles.
   

   Function: It controls some reflex actions and is part of the circuit involved in the control of eye movements, hearing, motor control, sleep & wake cycle, arousal & temperature regulation and other voluntary movements.
   

       (iii) Hindbrain: It is also called ‘Rhombencephalon’, region of the developing vertebrate brain that is composed of the medulla oblongata, the pons and the cerebellum. The hindbrain includes the upper part of the spinal cord, the brain stem and a wrinkled ball of tissue which is called ‘cerebellum‘.
   

   Function: The hindbrain controls the body’s vital functions such as respiration and heart rate. The cerebellum coordinates movement and is involved in learned note movements. Whenever, any movement like playing guitar, or hitting a cricket ball takes place, cerebellum is activated. It coordinates rhythm, motor activity, sleep and wakefulness etc.
   

   5.1    Protection of brain tissue: A delicate organ like the brain, which is so important for a variety of activities, needs to be carefully protected. For this, the body is designed so that the brain sits inside a bony box. Inside the box, the brain is contained in a fluid-filled balloon which provides further shock absorption.
   

   5.2    Action of Nervous Tissue: when the action or movement is to be performed, muscle tissue will do the final job. When a nerve impulse reaches the muscle, the muscle fibre must move. The simplest notion of movement at the cellular level is that 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.
   

   Questions (Page – 119)
   

Q-1: What is the difference between a reflex action and walking?

Ans: Reflex action are the involuntary actions that occur in response to stimuli. They occur without involvement of conscious areas of brain. All the reflex actions are unconscious actions. Reflex action occurs in brain and spinal cord of central nervous systems.

On the other hand, voluntary actions are those which occur under the control of cerebellum of the brain. Walking is controlled by brain as is used when required. Its’ a controlled action.

Q-2: What happens at the synapse between two neurons?

Ans: In the synapse between two neurons electric signals are converted into chemicals that can easily cross over the gap and pass on the chemical messenger to next neuron where it is converted back to electrical signal.

Q-3: Which part of the brain maintains posture and equilibrium of the body?

Ans: Cerebellum which is a part of Hind brain which is responsible for controls the motor functioning. Hence, it is the part engaged in the maintenance of posture and equilibrium of the body.

Q-4: How do we detect the smell of an agarbatti (incense stick)?

Ans: Smell of an agarbatti is detected by Nose, olfactory receptors present in the nose sends electrical signal to the fore brain. Fore-brain interprets this signal as the incense stick to be detected as smell.

Q-5: What is the role of the brain in reflex action?

Ans: Reflex actions are formed instantaneously in response to the stimulus that has no time to think. For instance, the sensory nerves that detect the heat are connected to the nerves that move the muscles of the hand. Such a connection of detecting the signal from the nerves (input) and responding to it quickly (output) is known as reflex arc.

Reflex actions are generated in spinal cord and the information also reaches to brain. This helps the brain to record this event and remember it for future use.  Brain helps the person to get awareness of the stimulus and prevent himself from that situation again.

6.1    Coordination in plants: Animals have a nervous system for controlling and coordinating the activities of the body. But plants have neither a nervous system nor muscles. Like animals, some plants also show instant response. When a part of ‘touch me not’ plat is touched the plant instantly responds and shrinks. There is no nervous tissue, no any muscle tissue. It is also observed that the response happens at a point different from the point of touch. It means information that a touch has occurred must be communicated. It reveals that there might be a coordinating systems which instantly coordinates and hence such response is received. It is interesting to know about it.

The plants also use electrical-chemical means to convey this information from cell to cell but unlike in animals, there is no specialized tissue in pants for the conduction of information. But unlike animals, there is no specialized tissue in plants for the conduction of information. In animals some cells must change shape in order for movement to happen. Instead of the specialized proteins found in animal muscle cells, plant cells change shape by changing the amount of water in them resulting in swelling or shrinking and therefore in changing shapes.

6.2    Movement due to Growth:
It is often found that some plants like ‘pea’ plant climb up other plants or fences by means of tendrils. These tendrils are sensitive to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus cling to it. Plants respond to stimuli slowly by growing in a particular direction. Since, this grown is directional, it appears as if the plant is moving.

Plants move in response to stimulus. However, in plants, generally two types of movements take place – (a) Tropic movement & (b) Nastic movements.

6.3    Tropic movements: The growth movements which takes place in the direction of the stimulus are known as Tropic movements. In this movement, the response acts on the protoplasm from one side. A tropic movement may be towards or away from the stimulus. Tropic movements are further divided into various types – (i) Phototropism (ii) Chemotropism (iii) Hydrotropism (iv) Geotropism (v) Thigmotropism.

    (i) Phototropism (Response to light): In this type of movement, plant grows in the direction of light. The plant has a chemical which is known as ‘auxin’. Auxin reacts in response to light and this causes the cells of the plant to elongate. Growth in the direction of light is called positive phototropism whereas away from light is called negative phototropism.

Example: (a) Stems grows towards the direction of light hence, it it called positive phototropic. (b) Roots grow opposite to light hence; roots are called negative.

(ii) Chemotropism (Response to chemical): The movement of a part of the plant towards a chemical is called chemotropism. During the process of fertilization the movement of pollen tube towards ovule due to secretion of a sugary chemical in the ovary is an example of chemotropism

(iii) Hydrotropism (Response to water): The movement of a part of the plant towards water is called hydrotropism, e.g., movement of roots, as roots grow in the direction of higher humidity level.

(iv) Geotropism (Response to gravity): The movement of a part of the plant towards gravity is called geotropism. Growth of roots of plants in downward direction is an example of geotropism.

(v) Thigmotropism: In this type of growth movement, the growth movement is regulated by temperature is known as thigmotropism.

Example: The peduncles of Anemone nemerosa grows in response to the heat imparted by the sun. The grapevine needs support to which the tendril winds. If the tendril does not respond to the support, the grapevine will not grow.

6.4    Nastic movements: In this type of growth movements, movements are non-directional responses to the stimuli. These movements are independent of the direction of the stimuli. These movements can be due to changes in turgor or growth.

Example: The response of the touch-me-not plant to touch. However, this is not a growth.

Questions (Page – 122)

Q-1: What are plant hormones?

Ans: Plant hormones are the organic substances produces at certain sites of the plant and are translocated to other parts based on the requirement. Plant hormones help to coordinate growth, development and responses to the environment.

Example: Auxin’s Gibberlin’s, cytokines, abscisic acid and ethylene.

Q-2: How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Ans: The difference is tabulated below:

Q-3. Give an example of a plant hormone that promotes growth.

Ans: Hormons which promote growth in plants are – Auxins and Gibberlins.

Auxins are responsible for the cell elongation in shoot and also regulates growth.

Gibberlins are responsible for stem elongation and germination.

Q-4: How do auxins promote the growth of a tendril around a support?

Ans: Auxins are the plant hormones produces at the tip of a shoot and root. Auxins are present at the tip of tendrils. When tendrils are attached around any support their growth is slowed down as auxins are sensitive to touch. This make them move to the other side of the tip to get support this makes the other side grow faster than the side of tendril in contact with the support and the tendril bends towards the support.

Q-5: Design an experiment to demonstrate hydrotropism.

Ans: To demonstrate hydrotropism in plants, following may be done.

Procedure : A seedling is required to be planted in a vessel containing soil.

1. Adjacent to the seedling, a porous pot containing water to be placed
   
2. Now the set up made should be left for few days.
   

Observation : On examining the roots it is observed that the roots bend towards the source of water and do not grow straight.

Conclusion: It confirms that plant shows hydrotropism as the roots bend towards the porous pot of water. As hydrotropism is a plant growth response in which the direction of growth is determined by a stimulus of gradient in water concentration.

7.1    Hormones in animals: Animals are more complex than plants. As animals have many specialized organs to perform specialized functions for their control and coordination. This coordination in animals happens due to – (a) The nervous coordination (Nervous System) and (b) The Chemical coordination (Endocrine System). Both these systems act in a coordinated manner in animals, so as to regulate the various body activities.

7.2    Endocrine System: This system comprises of different endocrine glands and hormones. These endocrine glands in animals help in the chemical coordination. They secrete chemicals called hormones. They are special messengers that control many body functions, including hunger, body temperature, mood, growth and development, metabolism, reproductive processes etc.  The endocrine glands are ductless and hence are also called as ductless glands.

Hormones: Hormones are chemicals which are secreted by the endocrine glands directly into the bloodstream. Through the blood, these hormones in animals reach their target organs to stimulate or inhibit specific physiological processes. The site of production of the hormones is different and the site of action is different. Even though, there are different hormones in the bloodstream, each will act only on the specific target organ. There are around 20 major hormones in animals that are released by the endocrine glands into the blood, playing a major role in many of the physiological processes happening in the body. The hormone levels in the body can be influenced by several factors – Stress, Infection, Minerals in the blood etc. influence the hormone levels in animals.

7.3  There are many different kinds of Endocrine glands which are discussed below:

(a) Hypothalamus: This gland forms an important link between the nervous system and the endocrine system, via the pituitary gland.  Some of the important functions are:
(1) Helps in maintaining the body temperature, controls sleep, hunger, thirst, emotions and moods.
(2) It also controls the release of 8 major hormones by the pituitary gland.
(3) Controls the sexual behaviour and reproduction.

(c) Thyroid gland: It is the largest endocrine gland that is shaped like a butterfly. It produces the thyroxine hormone, which controls the metabolic rate in the body. Apart from that, it also plays a role in the bone growth, development of the brain and nervous system in children. Iodine is important for the synthesis of thyroxine.

(d) Parathyroid gland: This gland releases parathormone which helps in regulating the calcium and phosphorus levels in the bone.

(e) Pineal gland: This produces melatonin hormone that regulates the sleep patterns.

(f) Adrenal gland: These glands are located on top of the kidneys and produce hormones such as adrenaline, cortisol, and aldosterone etc. These hormones control stress, help control blood sugar, burn protein and fat and also regulate blood pressure.

(g) Pancreas: They secrete two important hormones – insulin and glucagon. Both work together to maintain the glucose levels in the blood.

(h) Testes: These glands are present in males and produce testosterone hormone.

(g) Ovaries: The ovary is a ductless reproductive gland in which the female reproductive cells are produced. Females have a pair of ovaries, held by a membrane beside the uterus on each side of the lower abdomen. Ovaries produce and release two groups of sex hormones—progesterone and estrogen. There are actually three major estrogens, known as estradiol, estrone, and estriol. These substances work together to promote the healthy development of female sex characteristics during puberty and to ensure fertility

Questions (Page – 125)

Q-1: How does chemical coordination take place in animals?

Ans: Chemical coordination takes place in animals with the help of chemical messengers called Hormones. Hormones are the chemical fluids that are secreted by specific glands of the endocrine gland. Hormones regulate the growth, development and homeostasis of the animals.

Q-2: Why is the use of iodised salt advisable?

Ans: Usage of Iodised salt is advisable to avoid the deficiency of Iodine. If the intake of iodine is low, the release of thyroxine from the thyroid gland will be decreased. This affects fat, carbohydrate and protein metabolism.

Thus a person may have goitre problem in case if the intake of iodine is lowered.

Q-3: How does our body respond when adrenaline is secreted into the blood?

Ans: Adrenaline hormone is secreted in large amounts when a person is frightened, or mentally disturbed. When it reaches the heart, it beats faster to supply more oxygen to our muscles. The breathing rate also increases because of the contractions of diaphragm and the rib muscles. It also raises the blood pressure and allows more glucose to enter into the blood. All these responses together enable body to deal with the emergency situations.

Q-4: Why are some patients of diabetes treated by giving injections of insulin?

Ans: Diabetes is a condition where insulin hormone is produced less or stopped by pancreatic cells of a person. Insulin regulates blood glucose by converting extra glucose to glycogen. When insulin is not produced adequately person blood glucose level which leads to adverse effects. In order to maintain the insulin and blood glucose level diabetes patients are treated with injections of insulin.
                                                                    Exercise (Page – 126)

Q-1: Which of the following is a plant hormone?

(a) Insulin (b) Thyroxin (c) Oestrogen (d) Cytokinin

Ans: The correct answer is – (d) Cytokinin .  Cytokinin is a plant harmone where as Insulin, Thyroxin, Oestrogen are the hormones produced by animals.

Q-2: The gap between two neurons is called a

(a) dendrite (b) synapse (c) axon (d) impulse

Ans: The correct answer is (b) Synapse. Dendrite is a short branched extension of a nerve cell, along which impulses received from other cells at synapses are transmitted to the cell body.

An axon or nerve fiber is a long, slender projection of a nerve cell or neuron in vertebrates that typically conducts electrical impulses known as action potentials away from the nerve cell body. The function of the axon is to transmit information to different neurons, muscles, and glands. Impulse an electrical signal that travels along axon.

Q-3: The brain is responsible for

(a) thinking (b) regulating the heart beat (c) balancing the body (d) all of the above.

Ans: The correct answer is (d) all the above.

Brain is responsible for thinking, brain regulates the heartbeat, it balances the body.

Q-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?

Ans: Receptors are present throughout the human body mainly in sense organs. Receptors collect the information about changes that happen around and send the signal to information to brain which render effector mechanism against the change. When receptors do not work properly, the environmental stimuli are not able to create nerve impulses and body does not respond.

Q-5. Draw the structure of a neuron and explain its function.

Ans: Neurons are nerve cells which are functional units of the nervous system. The Three main parts of neurons are – (a) Dendrites, (b) Axons and (c) cell body.

(a) Dendrite: Detects information and sends it to cell body

(b) Axon: Conducts messages away from cell body and signal to next neuron.

(c) Cell Body: Maintains growth of the cell

Q-6. How does phototropism occur in plants?

Ans: Directional movement and growth of plant in response to light is called as phototropism. Phototropism occurs due to increased auxin on the dark side and decreased auxin on the illuminated side. Owing to the presence of more auxin, leaf in the darker side grows faster causing it to bend towards the source of light.

Q-7: Which signals will get disrupted in case of a spinal cord injury?

Ans: In case of a spinal cord injury Reflex action – Impulses from various body parts will not be conducted to brain. Message from brain will not be conducted to various organs of the body. It causes various problems.

Q-8. How does chemical coordination occur in plants?

Ans: Plant growth, development and responses to the environment is controlled and coordinated by a special class of chemical substances known as hormones. Hormones are produced in one part of the plant and are transported to all the needy parts of the plant. The five major types of phytohormone are auxins, gibberellins, cytokinins, abscisic acid, and ethylene. These phytohormones are either growth promoters (such as auxins, gibberellins, cytokinins, and ethylene) or growth inhibitors such as abscisic acid.

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

Ans: There are various organs in an organism. These organs are requird to be carefully controlled and coordinated for the survival of an organisms. In the body of an organism various fluids are secreted from the glands of the endocrine system. These hormones are responsible for the overall growth and development of an organism. All others daily decision that includes voluntary and involuntary action are controlled by central nervous system(CNS).

Coordination is needed for all human activities to be performed. Nervous system receives information from surroundings which is processed and response is elicited. The endocrine system (hormonal system) helps in integrating various metabolic activities like reproduction, development, all reflex actions (cope up with various give up situations).

The hormonal system in plants helps in process of photosynthesis; they need carbon dioxide, water and sunlight. The stomatal opening in leaves opens up to allow in carbon dioxide gas, the roots bend towards water and the stem grows towards sunlight, the tendrils in climbing pants are supported by the hormonal system of the plant body.

Thus, need of control and coordination system in an organisms is required and it is very essential.

Q-10. How are involuntary actions and reflex actions different from each other?

Ans: The difference between involuntary actions and reflex actions are tabulated below:

Q-11: Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Ans: The comparison is as follows:

Q- 12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Ans: The difference is as follows:

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