ncert qsns Flashcards
What is the difference between a reflex action and walking?
Reflex action: It is a spontaneous and involuntary response to a stimulus.
It is the response of the spinal cord.
Its intensity cannot be changed.
It increases the survival and protective values of the organism.
Walking: It is acquired through learning and is a voluntary response.
It is controlled by the hindbrain.
its intensity can be changed.
It is concerned with locomotion.
What happens at the synapse between two neurons
Synapse is the small gap between two neurons. At the end of axon, the electrical impulse sets athe release of some chemicals, which crosses the synapse and starts a similar electrical impulse in dentrite of the next neuron. Synapse actually acts like a one way valve because the chemical substance is present only at one side of gap.
Mention the part of the brain, which maintains posture and equilibrium of the body.
Cerebellum is a part of the hindbrain that maintains the posture and equilibrium of the body.
What is the role of brain in reflex action?
Brain has no role in reflex action. It is a extremely quick action, which does not involve any thinking by the brain. In this type of action, the stimulus is received by the spinal cord that sends a response. e.g. coughing.
What are plant hormones?
Plant hormones are organic substances which are naturally produced in higher plants, which control the growth and other physiological functions at a site further away from the place of secretion. These are required in very small amounts.
Give an example of a plant hormone that promotes growth.
Auxin is a plant hormone, which promotes growth in plants.
How do auxins promote the growth of a tentril around a support?
Auxins promote cell elongation and are present at shoot tip. When the tendril comes in contact with a support, auxin stimulates faster growth of the cells of opposite side. Thus the tendril coils around the support
How does chemical coordination take place in animals?
Chemical coordination is performed by hormones, which are chemical messengers secreted by endocrine gland.
These hormones coordinate the activities of organisms and also their growth.
The timing and the amount of secretion released is regulated by the feedback mechanism.
Why is it advised to use iodised salt in diet?
Iodised salt is advised because it contains iodine. Iodine is essential for the synthesis of the thyroxine hormone by the thyroid gland. Deficiency of thyroxine can lead to suffering from goitre.
How does our body respond when adrenaline is secreted into the blood?
Adrenaline hormone is secreted by the adrenal gland into the blood and carried to different parts of the body.
In case of an emergency, danger or stress, it is released in large quantities. As a result, It causes increase in heart rate, blood pressure, resulting in supply of more oxygen to the muscles.
The blood supply to the digestive system and skin is reduced due to contraction of muscles around small arteries in these organs. The breathing rate also increases due to the contraction of diaphragm and rib muscles. All these together help the animal to deal with the emergency situation.
Why are some people with diabetes treated by giving injections of insulin?
Some diabetes patients are given injections of insulin to fulfil the requirements of insulin in their body.
Insulin is a hormone produced by the beta cells of the pancreas and helps in regulating blood sugar levels in our body. Sometimes, at times of high blood sugar levels in our body, the pancreas produce less insulin . Due to lack of insulin, it leads to many harmful effects in our body.
What is the function of receptors in our body?
The function of receptors in our body is very important as they collect information about changes in the environment around us. Receptors then pass the same information in the formation of nerve impulses to the CNS. Where the information is processed and the ultimate response is given.
Draw the structure of the neuron and explain its function.
Function of neuron- The neuron receives information from the receptors as electrical impulse, at dentric end. The impulse then travels from the dentrites to the cell body and further along axon to its end. At the end of the axon, the electrical impulse leads to the release of some chemicals.
These chemicals cross the synapse and reaches the next neuron. This is how a nerve impulse travel through the body. Thus, neurons are important in receiving information from the surrounding and in sending it to the effector.
How does photrotopism occur in plants?
The directional movement of a plant in response to light is called phototropism. Usually, the shoot responds by bending towards light and root responds by bending away from light.
This happens as follows:
When sunlight falls straight on the plant, the auxin hormone synthesised at the tip of the stem spreads uniformly down the stem and due to equal concentration of auxin, the stem grows straight.
When sunlight fall on only one side of the plant, the auxin diffuses towards the shady side of the shoot. The concentration of auxin stimulates the cells to grow longer, thus the stem appears to be bend towards the light.
Which signals will get disrupted in case of a spinal cord injury?
In case of a spinal cord injury, signals for reflex action and involuntary action will get disrupted.
