Answer The Following Question.
1. What is the difference between a reflex action and walking?
Ans : Difference between reflex action and walking:
Nature of Action:
Reflex Action: It is an involuntary, automatic response to a stimulus, controlled by the spinal cord without involving the brain.
Walking: It is a voluntary, coordinated movement that involves the brain, muscles, and motor neurons.
Conscious Control:
Reflex Action: Occurs without conscious control or awareness.
Walking: Requires conscious control and coordination of different body parts.
Speed of Response:
Reflex Action: Happens almost instantly, typically in milliseconds.
Walking: Involves a slower, more controlled process.
Example:
Reflex Action: Touching a hot object and immediately pulling your hand away.
Walking: Moving from one place to another using your legs.
Neural Pathway:
Reflex Action: Involves a simple neural pathway (reflex arc) through the spinal cord.
Walking: Involves complex neural pathways involving the brain and motor pathways.
2. What happens at the synapse between two neurons?
Ans: Gap between neurons: The synapse is the small gap between the axon terminal of one neuron and the dendrite of the next.
Chemical transmission: When an impulse reaches the axon terminal, neurotransmitters are released.
One-way impulse: Neurotransmitters carry the signal across the synapse to the next neuron, ensuring one-way transmission.
Signal conversion: The electrical signal is converted to a chemical signal
3. Which part of the brain maintains posture and equilibrium of the body?
Ans : Cerebellum, a part of hindbrain is responsible for maintaining posture and equilibrium of the body.
4. How do we detect the smell of an agarbatti (incense stick)?
Ans: To detect the smell of an agarbatti (incense stick):
Receptors in the nose: The olfactory receptors in the nasal cavity detect the smell molecules.
Signal transmission: The receptors send signals to the olfactory bulb in the brain.
Processing in the forebrain: The forebrain processes and interprets the smell, linking it with past experiences and information stored in the brain.
Perception: We perceive the smell based on this interpretation.
5. What is the role of brain in reflex action?
Ans: The role of the brain in reflex action:
Reflex action: Reflex actions are quick and automatic responses to stimuli that do not require conscious thinking, such as withdrawing a hand from a hot object.
Reflex arc: Sensory nerves detect the stimulus and send signals to the spinal cord, where the reflex arc forms. The spinal cord processes the signal and sends an immediate response to the motor nerves, which act on the muscles.
Brain’s role: While the brain is aware of the stimulus and the resulting action, it is not involved in initiating the response. The brain only becomes aware of the reflex after it has occurred
6. What are plant hormones?
Ans: Plant hormones (phytohormones) are naturally-occurring organic substances that regulate various functions in plants. They are synthesized in small amounts in one part of the plant and then transported to other parts where needed. The five major types of plant hormones are:
Auxins: Promote growth and cell elongation.
Gibberellins: Stimulate stem elongation, seed germination, and flowering.
Cytokinins: Promote cell division and growth.
Abscisic acid: Inhibits growth and promotes seed dormancy.
Ethylene: Regulates fruit ripening and plant stress responses.
7. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Ans : Difference between movement of leaves of sensitive plants and movement of shoot towards light :
8. Give an example of a plant hormone that promote growth.
Ans : Auxin promotes growth of cells.
9. How do auxins promote the growth of a tendril around a support?
Ans: Auxins are plant hormones that regulate growth.
When a tendril comes in contact with a support, auxins move away from the contact point.
The side of the tendril with less auxin grows faster than the side in contact with the support.
This differential growth causes the tendril to curl around the support.
This process is called thigmotropism, which is the plant’s response to touch.
10. Design an experiment to demonstrate hydrotropism.
Ans : Take a tin box with hole at bottom. Fill it with moist saw dust. Sow some gram seeds in it. Keep the tin box in tilted position. When seeds start germinating, water the saw dust only in lower side of the tin box. You will observe that the radicle move towards the wet saw dust. This shows that root is positively hydrotropic.
11. How does chemical coordination take place in animals?
Ans: Chemical coordination in animals:
Chemical coordination is achieved through hormones.
Hormones are secreted by endocrine glands.
These hormones are released into the bloodstream.
The hormones travel through the blood to the target tissues or organs.
Once they reach the target, they trigger specific responses or actions in the body.
12. Why is the use of iodised salt advisable?
Ans: Use of iodised salt:
Iodine is essential for the thyroid gland to produce the hormone thyroxin.
A deficiency of iodine can lead to Goitre (swelling of the thyroid gland).
Iodised salt contains the required amount of iodine.
Consuming iodised salt helps prevent iodine deficiency and related health issues.
13. How does our body respond when adrenaline is secreted into the blood?
Ans:Body’s response to adrenaline secretion:
When adrenaline is secreted into the blood, it reaches various target organs.
It triggers a “fight or flight” response to help the body deal with stressful situations, such as running away from danger.
Heart rate increases to supply more oxygen to muscles.
Small arteries around the digestive system and skin contract, diverting blood flow towards the muscles.
These responses enhance the body’s ability to act quickly and effectively in critical situations.
14. Why are some patients of diabetes treated by giving injections of insulin?
Ans: Diabetes occurs due to insufficient or no secretion of the hormone insulin by the pancreas.
Without enough insulin, blood sugar levels remain high.
Insulin helps to convert excess sugar in the blood into glycogen, which is stored in the liver and muscles.
To control blood sugar levels, patients with diabetes are given insulin injections to supply the hormone and maintain proper glucose metabolism.
15. Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinins
Ans : (d) Cytokinin.
16. The gap between two neurons is called a
(a) Dendrite
(b) synapse
(c) axon
(d) impulse
Ans : (b) Synapse.
17. The brain is responsible for
(a) thinking
(b) regulating the heartbeat.
(c) balancing the body
(d) all of above.
Ans : (d) All the above.
18. What is the function of receptors in our body? Think of situation where receptors do
not work properly. What problems are likely to arise?
Ans: Function of receptors:
Receptors detect stimuli from the environment through sense organs.
They convert stimuli into nerve impulses sent to the brain.
If receptors malfunction:
Visual receptors: Blindness or poor vision.
Auditory receptors: Hearing loss.
Taste/smell receptors: Loss of taste or smell.
Pain receptors: Undetected injuries.
This results in the inability to perceive or respond to surroundings properly.
19. Draw the structure of a neuron and explain its function.
Ans: Explanation of Function:
Dendrites: Receive electrical impulses from other neurons or sensory receptors.
Cell Body (Soma): Processes incoming information.
Axon: Transmits the electrical impulse from the cell body to the axon terminal.
Axon Terminals: Release neurotransmitters, chemicals that pass the impulse to the next neuron through a synapse.
Synapse: The gap between two neurons where neurotransmitters carry the signal to the next neuron.
This entire process allows for rapid communication within the nervous system.
20. How phototropism does occur in plants?
Ans: Phototropism in Plants:
Definition: Phototropism is the movement of plant parts, usually the shoot, towards light.
Mechanism:
When light comes from one direction, auxins (a type of plant hormone) accumulate on the shaded side of the shoot.
The accumulation of auxins causes cells on the shaded side to grow faster than those on the light-exposed side.
Result: This unequal growth causes the shoot to bend towards the light source, allowing the plant to maximize light exposure for photosynthesis.
21. Which signals will get disrupted in case of a spinal cord injury?
Ans :
(i) Reflex action
(ii) Impulses from various body parts will not conducted to brain.
(iii) Message from brain will not be conducted to various organs.
22. How does chemical coordination occurs in plants?
Ans: Chemical Coordination in Plants:
Absence of Nervous System: Unlike animals, plants do not have a nervous system for control and coordination.
Hormones: Plants respond to environmental stimuli through growth, development, and movement, which are regulated by hormones.
Hormone Action: These hormones are produced in one part of the plant and transported to other parts as needed. For example, hormones produced in the roots are carried to other parts of the plant.
Types of Phytohormones:
Auxins
Gibberellins
Cytokinins
Abscisic Acid
Ethylene
Function:
Some hormones promote growth (auxins, gibberellins, cytokinins, ethylene).
Others inhibit growth (abscisic acid).
23. What is the need for a system of control and coordination in an organism?
Ans: Need for a System of Control and Coordination in Organisms:
Response to Changes: Coordination helps in maintaining body functions in response to internal and external changes.
Organism’s Functioning: Proper coordination ensures that all movements and responses to stimuli are controlled and managed effectively.
In Animals: The nervous and muscular systems are responsible for control and coordination. The nervous system sends messages to and from the brain, while the spinal cord plays a key role in relaying these messages.
Importance: Without this system, the body cannot function properly. For instance, if we touch something hot, the nervous system helps us withdraw our hand immediately to avoid harm.
Example: In the absence of coordination, we would not respond to stimuli, such as touching a hot object, leading to potential injury.
24.How are involuntary actions and reflex actions different from each other?
Ans : Difference between involuntary and reflex actions is as follows:
Differences between Involuntary Actions and Reflex Actions:
Control:
Involuntary Actions: These are automatic actions controlled by the brain and are not consciously controlled. For example, breathing, digestion, and heartbeat.
Reflex Actions: These are rapid, automatic responses to stimuli controlled by the spinal cord, and not involving the brain. For example, withdrawing your hand from a hot object.
Duration of Response:
Involuntary Actions: These actions continue for longer periods, such as the heartbeat or digestion.
Reflex Actions: These are quick and immediate responses to a stimulus, often lasting only a short time.
Complexity:
Involuntary Actions: They are often more complex and involve multiple organs and systems. For instance, digestion involves the stomach, intestines, enzymes, and more.
Reflex Actions: These are simple and involve a direct response pathway, usually consisting of sensory neurons, a spinal cord or brainstem, and motor neurons.
Example:
Involuntary Actions: Breathing, heartbeat, and blinking.
Reflex Actions: Knee-jerk reaction, touching something hot and withdrawing the hand.
25. Compare and contrast nervous system and hormonal control and coordination in
animals.
Ans : Difference between nervous control and hormonal control:
26. What is the difference between the manner in which movement’s takes place in a
sensitive plant and movement in our legs?
Ans : Difference between movement in a sensitive plant and movement in our legs: