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What is the difference between a reflex action and walking?
A reflex action is a rapid, involuntary response to a stimulus. It does not involve any thinking. For example, we pull back our hand immediately on touching a hot object. Walking, on the other hand, is a voluntary action. It is under our conscious control. The response to a reflex action is generated at the spinal cord whereas walking is under the control of the motor area of the brain.
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What happens at the synapse between two neurons?
● When a nerve impulse reaches the end of an axon, the axon releases chemicals called neurotransmitters (e.g., acetylcholine). ● Neurotransmitters travel across the junction between the axon and the dendrites of the next neuron. This junction is called a synapse. ● Neurotransmitters bind to the membrane of these dendrites. ● This binding allows the nerve impulse to travel through the receiving neuron till it reaches the target cells (e.g., muscle cells)
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Which part of the brain maintains posture and equilibrium of the body?
Cerebellum, a part of hindbrain is responsible for maintaining posture and equilibrium of the body.
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How do we detect the smell of an agarbatti (incense stick)?
Forebrain is the thinking part of the brain. It has separate areas that are specialized for hearing, smelling, sight, taste, touch, etc. When the smell of an incense stick reaches us, olfactory receptors present in the nose detect it. The forebrain interprets it by putting it together with the information received from other receptors and with the information already stored in the brain as memory.
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What is the role of the brain in reflex action?
Reflex action can be defined as the immediate, involuntary response to a stimulus (sudden change in the environment) by human beings. The sensory nerves that detect the stimulus are connected to the motor nerves that move the muscles. Such a connection of detecting the signal from the receptors (input) and responding to it quickly (output) through effectors is called a reflex arc. The reflex arc is the pathway for signaling between receptors and effectors in a reflex action. The signaling is through the actions of the sensory and motor neuron which connect to each other in the spinal cord.Reflex arc Reflex arcs are formed in the spinal cord but the information (input) reaches the brain. The brain is only aware of the signal and the response that has taken place. Brain stores this information in the memory. This is helpful in conditioning of certain reflexes. However, the brain has no role to play in the creation of the response.
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What are plant hormones?
Plant hormones or phytohormones are naturally-occurring organic substances that regulate growth and metabolism in plant cells. These are synthesized in one part of the plant body (in minute quantities) and are translocated to other parts when required. The five major types of plant hormones are auxins, gibberellins, cytokinin, abscisic acid, and ethylene.
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How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
The movement of leaves of the sensitive plant, Mimosa pudica or “touch me not”, occurs in response to touch or contact stimuli. This is a type of nastic movement. Such movements occur due to the difference in turgor pressures in cells of the leaf. This movement is independent of growth. These movements are non-directional. The movement of shoot towards light is known as phototropism. These kind of tropic movements occur due to growth in a specific direction. Thus, this type of movement is directional and is growth dependent. Example of phototropism is movement of sunflower in direction of sunlight.
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Give an example of a plant hormone that promotes growth.
Auxin is an example of growth-promoting plant hormone.
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How do auxins promote the growth of a tendril around a support?
Auxin is synthesized at the shoot tip. It helps the cells of the shoot tips to grow longer. When one side of a tendril encounters a support, auxin stimulates faster growth of the cells on the opposite side, leading to uneven growth on either side of the tendril. This causes the tendril to form a coil around the support. This makes the tendrils appear as a watch spring round the support.
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Design an experiment to demonstrate hydrotropism.

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How does chemical coordination take place in animals?
Chemical coordination takes place in animals with the help of hormones. Hormone is a chemical messenger that regulates various physiological processes in living organisms. It is secreted by specific glands. The hormones act on target organs which may be far away from the gland. Therefore, these hormones are secreted by the glands in the blood and are transported to the target organ where they act. The regulation of physiological processes, and control and coordination by hormones comes under the endocrine system. The nervous system along with the endocrine system in our body controls and coordinates the physiological processes.
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Why is the use of iodised salt advisable?
Consumption of iodine in diet helps to synthesize thyroxine in the body. Deficiency of thyroxine results in the enlargement of the thyroid gland. This can lead to simple goitre.
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How does our body respond when adrenaline is secreted into the blood?
Adrenaline and noradrenaline are also called epinephrine and norepinephrine respectively. Adrenaline is responsible for stimulation of sympathetic nervous system. It prepares the body for any emergency. Getting scared, sweating, shivering, etc. are a result of adrenaline secretion. All these responses enable better transport of oxygen to muscle tissues for respiration so as to release more energy for either flight or fight. Thus, adrenaline enables the body to deal with any stress or emergency. Therefore, it is also called as emergency hormone.
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Why are some patients of diabetes treated by giving injections of insulin?
During diabetes mellitus the level of sugar in the blood (glucose) is too high. Insulin, a hormone secreted by the pancreas, helps in regulating blood sugar levels by converting excess glucose to glycogen in the liver. In such patients the amount of insulin secreted by the pancreas is insufficient to convert glucose to glycogen. This is the reason why diabetic patients are treated by giving injections of insulin.
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Which of the following is a plant hormone? (a) Insulin (b) Thyroxin (c) Oestrogen (d) Cytokinin
(d) Cytokinin is a plant hormone.
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The gap between two neurons is called a (a) dendrite. (b) synapse. (c) axon. (d) impulse
(b) The gap between two neurons is called a synapse.
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The brain is responsible for (a) thinking. (b) regulating the heartbeat. (c) balancing the body. (d) all of the above.
(b)The brain is responsible for thinking, regulating the heart beat and balancing the body.
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What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Receptor cells are sensory cells. They are usually located in our sense organs, such as the inner ear, the nose, the tongue, the eyes and the skin. Functions of receptors: (i) They sense the external stimuli such as heat or pain. (ii) They also trigger an impulse in the sensory neuron which sends message to the spinal cord. When the receptors are damaged, the external stimuli transferring signals to the brain are not felt. This could lead to damage to tissues and organs in the body. For example, in the case of damaged receptors, if one is being called out, the person may not be able to perceive the sound.
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Draw the structure of a neuron and explain its function.

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How does phototropism occur in plants?
Phototropism is the movement of plant parts in response to light. Shoots are positively phototropic whereas roots are negatively phototropic. Plants exhibit phototropism due to the action of auxins like indole-acetic acid (IAA). When one side of the shoot is exposed to sunlight molecules of IAA move to the opposite (shaded) side. IAA initiates cell division and elongation on the shaded side and not on the side of the shoot exposed to the light. This causes unequal growth on both sides of the shoot with the shaded portion growing more than the side exposed to the sun. This causes the shoot to bend towards the light.
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Which signals will get disrupted in case of a spinal cord injury?
In case of any injury to the spinal cord, all nervous signaling will be affected. This will affect the transmission of impulses from receptors to the brain as well as response from the brain to the effectors, especially the motor neurons.
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How does chemical coordination occur in plants?
Plants respond to stimulus by showing movements. The growth, development, and response to the environment in plants is controlled and coordinated by a special class of chemical substances known as plant hormones or phytohormones. Plant hormones are produced in one part of the plant body and are translocated to other parts. For example, a hormone produced in roots is translocated to other parts when required. The five major types of phytohormones are auxins, gibberellins, cytokinin, abscisic acid, and ethylene. These phytohormones are either growth promoters (such as auxins, gibberellins, cytokinin, and ethylene) or growth inhibitors such as abscisic acid.
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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 for different integrated body systems is known as coordination. All the movements that occur in response to stimuli need to be carefully coordinated and controlled. Control over responses to stimuli helps in more efficient response mechanisms. Co-ordination of various responses is essential for the organism to function efficiently considering all the stimuli and their effect. Therefore, various responses and physiological processes must be coordinated. In animals, the control and coordination movements are provided by nervous and muscular systems. In plants the control and co-ordination are done by the action of phytohormones.
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How are involuntary actions and reflex actions different from each other?
Involuntary actions cannot be consciously controlled. For example, we cannot consciously control the movement of food in the alimentary canal. These actions are however directly under the control of the brain. On the other hand, the reflex actions pulling back of hand on touching a hot object show sudden response and do not involve any thinking. This means that unlike involuntary actions, the reflex actions are not under the control of brain. Reflex actions can be conditioned whereas involuntary actions like heartbeat and peristalsis cannot be conditioned. It is possible to say that all reflex actions are involuntary, but all involuntary actions are not reflex actions.
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Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Nervous system mechanism & Hormonal system mechanism 1. The information is conveyed in the form of electric impulse 1. The information is conveyed in the form of chemical messengers 2. The axons and dendrites transmit the information through a coordinated effort. 2. The information is transmitted or transported through blood. 3. The flow of information is rapid and the response is quick. 3. The information travels slowly and the response is slow. 4. Its effects are short lived. 4. It has prolonged effects. 5. Does not cause growth 5. It can cause growth
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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 that takes place in a sensitive plant such as Mimosa pudica occurs in response to touch (stimulus). 1. Movement in our legs is an example of voluntary actions. 2. For this movement, the information is transmitted from cell to cell by electrochemical signals as plants do not have any specialized tissue for conduction of impulses. 2. The signal or messages for these actions are passed to the brain and hence are consciously controlled. 3. For this movement to occur, the plant cells change shape by changing the amount of water in them. 3. In animal muscle cells, some proteins are found which allow the movement to occur.
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