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Solutions for Science, Class 10, CBSE
Which of the following is a plant hormone?
Cytokinin
Reason— Cytokinin is growth promoting phyto-hormone.
The gap between two neurons is called a
synapse
Reason— Synapse is the point of contact between the terminal branches of axon with the dendrites of another neuron separated by a fine gap.
The brain is responsible for
all of the above
Reason— The brain is responsible for thinking, regulating the heart beat and balancing the body.
What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
The specialised tips of some nerve cells that detect the changes in our environment by receiving the stimulus are called receptors. These receptors are usually located in our sense organs, such as inner ear, nose, tongue, skin etc. For example, gustatory receptors (tongue) will detect taste while olfactory receptors (nose) will detect smell.
If receptors are not working properly, the external stimulus won't be able to stimulate receptors and no nerve impulse will be generated. The result will be that the body would not respond to changes in the surroundings.
Draw the structure of a neuron and explain its function.
The structure of a neuron is shown in the diagram below:
Function of neuron
Neurons are the structural and functional unit of the nervous system specialized to transmit information in the form of electrical impulses to different parts of the body. A neuron consists of a dendrite, cell body, and axon. Dendrites gather information about external changes, initiating a chemical reaction that generates an electrical impulse. This impulse travels from the dendrite to the cell body and then along the axon. At the axon's end, the electrical impulse triggers the release of chemicals that cross the synapse, initiating a similar electrical impulse in the dendrite of the next neuron. This process allows neurons to transmit nervous impulses throughout the body.
How does phototropism occur in plants?
When growing plants detect light, a hormone called auxin, synthesised at the shoot tip, helps the cells to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of auxin stimulates the cells to grow longer on the side of the shoot which is away from light. Thus, the plant appears to bend towards light showing phototropism.
Which signals will get disrupted in case of a spinal cord injury?
In case of a spinal cord injury, the signal coming from receptors as well as signal transmission to effector muscles will be disrupted. Transmission of information to brain will also be disrupted.
How does chemical coordination occur in plants?
The chemical coordination occur in plants with the help of plant hormones. The hormones are the chemical compound that would diffuse all around the original cell. Other cells around have the means to detect this compound using special molecules on their surfaces. Therefore, they are be able to recognise information, and even transmit it.
What is the need for a system of control and coordination in an organism?
A system of control and coordination is fundamental to the functioning of organisms, ensuring their ability to adapt to the environment, maintain internal stability, and carry out essential life processes. It helps in integrating the functions of different cells and organs. For example, the nervous and endocrine systems in animals coordinate the activities of various organs and tissues to maintain overall function. It ensures the optimal functioning and survival of the organism in its environment.
How are involuntary actions and reflex actions different from each other?
| Involuntary actions | Reflex actions |
|---|---|
| Involuntary actions refer to any actions or processes that occur without conscious control or awareness. | Reflex actions are rapid, spontaneous and involuntary actions that occur in response to a stimulus. |
| Involuntary actions are controlled by medulla oblongata. | Reflex actions are controlled by spinal cord. |
| For example, contractions of our digestive tract muscles, the heart beat. | For example, removing hand suddenly after touching a hot object. |
Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Nervous and hormonal mechanisms are two primary systems that animals use for control and coordination of physiological processes. Both these systems often work together, with the nervous system triggering the release of hormones in certain situations. Both systems allow animals to adapt and respond to changes in their internal and external environments.
The differences between nervous and hormonal mechanisms are summarised below:
| Nervous mechanism | Hormonal mechanism |
|---|---|
| Brain, Spinal cord and Neurons are involved. | Endocrine glands are involved. |
| The signal is transmitted electro-chemically through the nerve fibres and chemically across synapses. | The signal is transmitted chemically through blood. |
| The nervous response is short-lived. | Hormonal response is long-lived. |
| It is immediate/rapid. | It is usually slow. |
What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
| Movement of sensitive plants | Movement in our legs |
|---|---|
| In sensitive plant, the movement takes place as they use electrical-chemical means to convey the information from cell to cell, but there is no specialised tissue in plants for the conduction of information. | In humans, movement of leg occurs according to the control of nervous system. Specialised cells i.e neurons are responsible for transmission of impulse. |
| The plant cells change shape by changing the amount of water in them, resulting in swelling or shrinking, and therefore in changing shapes. | Specialised proteins found in animal muscle cells regulates the movement of leg. |
| Plant movement is always due to a physical stimulus. | It can occur due to reflex action or cognitive thinking may also be involved. |
What is the difference between a reflex action and walking?
Reflex action is an automatic or quick or immediate involuntary action in the body brought about by a stimulus. This occurs in an urgent or dangerous situation. Spinal cord is involved in reflex actions. Walking is a voluntary action in which thinking and decision making is involved. It is primarily coordinated by cerebrum.
What happens at the synapse between two neurons?
At the synapse, which is a tiny gap between two neurons, the sending neuron releases chemicals called neurotransmitters. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron.
Which part of the brain maintains posture and equilibrium of the body?
Cerebellum is the part of brain that maintains posture and equilibrium of the body.
How do we detect the smell of an agarbatti (incense stick)?
Olfactory receptors present in the nose receive the stimulus and transmit it through neurons in the form of electric impulse to brain. This is how we detect the smell of an agarbatti (incense stick).
What is the role of the brain in reflex action?
The brain has no role in reflex action as it is an involuntary action that requires no thinking. The spinal cord controls and manages reflex actions and the brain is not involved in the reflex arc.
What are plant hormones?
The chemical compounds that are used by plants for control, coordination and regulation of different functions are known as plant hormone. Different plant hormones help to coordinate growth, development and responses to the environment.
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 occurs due to electrical-chemical impulse that helps to convey information from cell to cell in plants. This is a rapid movement that happens by changing the amount of water in plant cells resulting in swelling or shrinking. It is not a growth movement instead it is a defensive mechanism of the plant. This phenomenon is called thigmonasty.
In contrast, the movement of a shoot towards light is a slower growth oriented movement in plants. This phenomenon is called phototropism. Plant hormone auxin plays a key role in phototropism. When light strikes one side of the shoot, the auxin moves to the shaded side, causing cells on that side to elongate. This differential growth results in the bending of the shoot towards the light source.
Give an example of a plant hormone that promotes growth.
Auxin and Cytokinins are plant hormones that promote growth.
How do auxins promote the growth of a tendril around a support?
The portion of tendril which is in contact to support has diffused amount of auxin while the open portion has less auxin. Therefore, 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.
Design an experiment to demonstrate hydrotropism.
Growth movement of the roots of the plant towards water is called hydrotropism.
Below experiment demonstrates hydrotropism:
Procedure
Observation
Conclusion
This experiment confirms that roots of a plant show positive hydrotropism as they bend towards the source of water (porous pot).
How does chemical coordination take place in animals?
Chemical coordination take place in animals by hormones. Hormone is secreted directly into the blood and carried to different parts of the body. The target organs or the specific tissues on which it acts responds accordingly.
Why is the use of iodised salt advisable?
It important for us to have iodised salt in our diet because iodine is necessary for the thyroid gland to make thyroxine hormone. The deficiency of iodine leads to under-function of thyroid gland and deficiency of thyroxine hormone which further results in hypothyroidism and goitre (enlargement of thyroid gland). Iodine deficiency in early stage of development may lead to stunted physical and mental growth.
How does our body respond when adrenaline is secreted into the blood?
When adrenaline is secreted into the blood, the heart beats faster, resulting in supply of more oxygen to our muscles. The blood to the digestive system and skin is reduced due to contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles.
Why are some patients of diabetes treated by giving injections of insulin?
Insulin, a hormone produced by the pancreas, is essential for regulating blood sugar levels. In cases where the pancreas doesn't produce enough insulin, blood sugar levels can rise, leading to diabetes. Elevated blood sugar can cause damage to organs and blood vessels. To address this, patients with diabetes may receive insulin injections to compensate for the insufficient production of insulin. These injections help control blood sugar levels, preventing complications and enabling effective diabetes management.