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Practice each question, then open the answer or worked solution.
Which of the following is a plant hormone?
Answer is d) cytokinin.
Cytokinin is a plant hormone whereas Insulin, Thyroxin, Oestrogen are the hormones produced by animals.
The gap between two neurons is called a
(a) Dendrite.
(b) Synapse.
(c) Axon.
(d) Impulse.
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 is an electrical signal that travels along axon.
The brain is responsible for
(a) Thinking.
(b) Regulating the heartbeat.
(c) Balancing the body.
(d) all of the above.
Answer is (d) all the above
Brain is responsible for thinking, brain regulates the heartbeat, and it balance 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?
Receptors are present throughout our body – mainly in sense organs. Receptors collect the information about changes that happen around us and send the signal/information to the brain which responds to the change detected. When receptors do not work properly, the environmental stimuli are not able to create nerve impulses and body does not respond.
Draw the structure of a neuron and explain its function.
Neurons are nerve cells which are functional units of the nervous system. Three main parts of neurons are Dendrites, Axons and cell body.
Dendrite: Detects information and sends it to cell body
Cell Body: Maintains growth of the cell
Axon: Conducts messages away from cell body and signal to next neuron.
How does phototropism occur in plants?
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. Because of presence of more auxin, a leaf in the darker side grows faster causing it to bend towards the source of light.
Which signals will get disrupted in case of a spinal cord injury?
In case of a spinal cord injury, signals coming from the nerves, as well as the signals coming to the receptors, will be disrupted. Both these signals meet in a bundle in the spinal cord. Hence, both these signals get disrupted.
How does chemical coordination occur in plants?
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 phytohormones 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.
What is the need for a system of control and coordination in an organism?
There are various organs in an organism. These organs must be carefully controlled and coordinated for the survival of an organism. 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 other daily decisions that include voluntary and involuntary actions are controlled by the central nervous system (CNS).
Coordination is needed for all human activities we perform. Our nervous system receives information from surroundings which is processed and a response is elicited. The endocrine system (hormonal system) helps in integrating various metabolic activities like reproduction, development, and 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, the stem grows towards sunlight, and the tendrils in climbing plants are supported by the hormonal system of the plant body.
Thus, we need a control and coordination system in an organism.
How are involuntary actions and reflex actions different from each other?
| Reflex actions | Involuntary actions |
| 1. Rapid automatic responses to a stimulus without the conscious involvement of the brain | 1. Occurs without the consciousness of an organism |
| 2. Controlled by spinal cord | 2. Controlled by mid brain or medulla oblongata |
| 3. Very quick and instantaneous | 3. Relatively slower |
| 4. May involve any muscle or a gland | 4. Involves only smooth muscles |
| 5. Can be conditioned | 5. Cannot be influenced by external conditioning |
| Examples: Blinking of eyes, salivation | Examples: Beating of heart, blood circulation |