Q1: What is the difference between a reflex action and walking?
Ans:
Q2: What happens at the synapse between two neurons?
Ans: A very small gap that occurs between the last portion of the axon of one neuron and the dendron of the other neuron is known as a synapse. It acts as a one-way valve to transmit impulses in one direction only.
This uni-directional transfer of impulses occurs as the chemicals are produced on only one side of the neuron i.e., the axon’s side. From the axon, the impulses travel across the synapse to the dendron of the other neuron.
DendriteQ3: Which part of the brain maintains the posture and equilibrium of the body?
Ans: Cerebellum, a part of the hindbrain is responsible for maintaining posture and equilibrium of the body.
Q4: How do we detect the smell of an agarbatti (incense stick)?
Ans: The thinking part of our brain is the forebrain. It has separate areas that are specialized for hearing, smelling, sight, taste, touch, etc. The fore-brain also has regions that collect information or impulses from various receptors.
When the smell of an incense stick reaches us, our forebrain detects it. Then, the forebrain interprets it by putting it together with the information received from other receptors and also with the information already stored in the brain.
Q5: What is the role of the brain in reflex action?
Ans:
Q1: What are plant hormones?
Ans: Plant hormones are the fluid that are secreted within the plant also known as phytohormones. Plant hormones regulate the growth and development of the plant. Examples of plant hormones are auxin, gibberellins etc.
Q2: How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Ans:
Movement of leaves of sensitive plant | Movement of shoot towards light |
(i) Growth independent movement. (ii) Movement is non-directional i.e., it is neither towards nor away from the stimulus. (iii) Such movements are referred to d as nastic movements. (iv) Such movements are reversible. | (I) Growth-dependent movement. (ii) Movement is towards the source of stimulus (light). So it is a directional movement. (in) Such movements are referred d as tropic movements. (iv) Such movements are irreversible. |
Q3: Give an example of a plant hormone that promotes growth.
Ans: Auxin is an example of a growth-promoting plant hormone. Auxins are responsible for cell elongation in the shoot and accelerates growth.
Q4: How do auxins promote the growth of a tendril around a support?
Ans: Auxin is synthesized at the shoot tip. It helps the cell grow longer. When a tendril comes in contact with a support, auxin stimulates faster growth of the cells on the opposite side, so that the tendril forms a coil around the support. This makes the tendrils appear as a watch spring.
Q5: Design an experiment to demonstrate hydrotropism.
Ans: To demonstrate hydrotropism in plants.
Procedure:
Observation:
On examining the roots it is observed that the roots bend towards the source of water and do not grow straight.
Result:
It confirms that the 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 a gradient in water concentration.
Experiment of Hydrotropism
Q1: How does chemical coordination take place in animals?
Ans:
Q2: Why is the use of iodized salt advisable?
Ans: Iodine stimulates the thyroid gland to produce thyroxin hormone. It regulates carbohydrate, fat, and protein metabolism in our body. Deficiency of this hormone results in the enlargement of the thyroid gland. This can lead to goitre, a disease characterized by swollen neck. Therefore, iodized salt is advised for the normal functioning of the thyroid gland.
Q3: How does our body respond when adrenaline is secreted into the blood?
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Q4: Why are some patient of diabetes treated by giving injections of insulin?
Ans: Diabetes is caused due to less or no secretion of the hormone insulin by the pancreas. In such a person, blood sugar level is high. Insulin converts extra sugar present in the blood into glycogen. Thus, patients suffering from diabetes are given insulin injections on to control their blood sugar levels.
Q2. The gap between two neurons is called a
(a) dendrite.
(b) synapse.
(c) axon.
(d) impulse.
Ans: (b) Synapse
The gap between two neurons is called a 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 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.
Q3. The brain is responsible for
(a) thinking.
(b) regulating the heartbeat.
(c) balancing the body.
(d) all of the above.
Ans: (d) all of the above
The brain is responsible for thinking, regulating the heartbeat and balancing the body.
Q4. 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 sensory structures (organs/tissues or cells) present all over the body. The receptors are either grouped in the case of the eye or ear or scattered in the case of the skin.
Functions of receptors:
When the receptors are damaged, the external stimuli transferring signals to the brain are not felt. For example, in the case of damaged receptors, if we accidentally touch any hot object, then our hands might get burnt as damaged receptors cannot perceive the external stimuli of heat and pain.
Q5. Draw the structure of a neuron and explain its function.
Ans:
Structure of Neuron
Functions of the three parts of a neuron:
Q6. How does phototropism occur in plants?
Ans: The growth movement in plants in response to light stimulus is known as phototropism. The shoots show positive phototropism and the roots show negative phototropism. This means that the shoots bend towards the source of light whereas the roots bend away from the light source.
Some examples of phototropism are as follows:
Q7. Which signals will get disrupted in case of a spinal cord injury?
Ans: The reflex arc connections between the input and output nerves meet in a bundle in the spinal cord. Nerves from all over the body meet in a bundle in the spinal cord on their way to the brain. In case of any injury to the spinal cord, the signals coming from the nerves as well as the signals coming to the receptors will be disrupted.
Q8. How does chemical coordination occur in plants?
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Q9. What is the need for a system of control and coordination in an organism?
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Q10. How are involuntary actions and reflex actions different from each other?
Ans: 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 such as the closing of eyes immediately when bright light is focused show sudden responses and do not involve any thinking. This means that, unlike involuntary actions, reflex actions are not under the control of the brain.
Q11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
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Q12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Ans:
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1. What is the role of hormones in control and coordination in living organisms? |
2. How do plants respond to stimuli in their environment? |
3. What is the difference between the nervous system and the endocrine system in terms of control and coordination? |
4. Can you explain the significance of reflex actions in control and coordination? |
5. What are the main components of the human nervous system involved in control and coordination? |
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