Chapter 6: Control and Coordination Exercise & In-Text Questions & Answers
1What is the difference between a reflex action and walking?
Answer & Reference: Reflex action is an involuntary, sudden response to a stimulus (e.g., pulling hand from flame) and does not involve conscious thinking. It is controlled by the spinal cord. Walking is a voluntary action controlled by the brain. (Page 102–103)
2What happens at the synapse between two neurons?
Answer & Reference:
At the synapse, the electrical impulse triggers the release of chemicals (neurotransmitters) which cross the gap and start a similar electrical impulse in the next neuron. (Page 101, Fig. 6.1)
3Which part of the brain maintains posture and equilibrium of the body?
Answer & Reference:
The cerebellum (part of the hind-brain) maintains posture and balance. (Page 104)
4How do we detect the smell of an agarbatti (incense stick)?
Answer & Reference:
Smell is detected by olfactory receptors in the nose. These generate electrical impulses that are sent to the fore-brain for interpretation. (Page 101, 103)
5What is the role of the brain in reflex action?
Answer & Reference:
The brain is not involved
6What are plant hormones?
Answer & Reference:
Plant hormones (or phytohormones) are chemical compounds synthesised in one part of the plant and diffuse to another part to regulate growth, development, and responses to environment. Examples: auxins, gibberellins, cytokinins, abscisic acid. (Page 108)
7How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Answer & Reference:
- Sensitive plant: Movement is **non-growth**, rapid, due to change in water pressure in cells (Fig. 6.4).
- Shoot towards light: Movement is **growth-related (phototropism)**, slow, due to uneven distribution of auxin. (Page 106–108)
8Give an example of a plant hormone that promotes growth.
Answer & Reference: Auxin or Gibberellin promotes growth. (Page 108)
9How do auxins promote the growth of a tendril around a support?
Answer & Reference:
When a tendril touches a support, auxin moves away from the contact point. Cells on the opposite side grow faster, causing the tendril to coil around the support. (Page 106, 108)
10Design an experiment to demonstrate hydrotropism.
Answer & Reference:
Take a seedling in a container with moist soil on one side and dry soil on the other. After a few days, the root will bend towards the moist soil, showing hydrotropism (growth in response to water). (Page 107)
11How does chemical coordination take place in animals?
Answer & Reference:
Chemical coordination occurs through hormones secreted by endocrine glands into the blood. These hormones travel to target organs and regulate activities like growth, metabolism, and stress response. (Page 109)
12Why is the use of iodised salt advisable?
Answer & Reference:
Iodine is needed for the thyroid gland to produce thyroxin, which regulates metabolism. Deficiency causes goitre (swollen neck). (Page 110)
13How does our body respond when adrenaline is secreted into the blood?
Answer & Reference:
Adrenaline increases heart rate, breathing rate, and blood flow to muscles. It reduces blood flow to skin and digestive system, preparing the body for “fight or flight”. (Page 109)
14Why are some patients of diabetes treated by giving injections of insulin?
Answer & Reference:
Insulin (from pancreas) regulates blood sugar. In diabetes, insulin is not produced in sufficient amounts, so injections are given to control blood sugar levels. (Page 110)
15Which of the following is a plant hormone? (a) Insulin (b) Thyroxin (c) Oestrogen (d) Cytokinin
17The brain is responsible for (a) thinking (b) regulating the heart beat (c) balancing the body (d) all of the above
Answer & Reference:
(d) all of the above. Fore-brain: thinking; medulla: heartbeat; cerebellum: balance. (Page 103–104, Exercises)
18What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Answer & Reference:
Receptors detect environmental changes (e.g., light, sound, touch) and generate nerve impulses. If damaged (e.g., in leprosy), the person cannot sense pain or heat, leading to injury. (Page 101)
19Draw the structure of a neuron and explain its function.
Answer & Reference:
A neuron has:
- Dendrites: Receive signals.
- Cell body: Contains nucleus.
- Axon: Transmits impulse.
- Synapse: Junction to next neuron/muscle.
Function: Transmit information as electrical impulses. (Page 101, Fig. 6.1)
Fig. 6.1: Simplified neuron structure
20How does phototropism occur in plants?
Answer & Reference:
Auxin accumulates on the shaded side of the shoot, causing cells there to grow longer, making the shoot bend towards light. (Page 108)
21Which signals will get disrupted in case of a spinal cord injury?
Answer & Reference:
Reflex actions and signals between brain and body parts below the injury will be disrupted. Voluntary and involuntary signals may be affected. (Page 102–103)
22How does chemical coordination occur in plants?
Answer & Reference:
Through plant hormones (e.g., auxin, gibberellin) that diffuse from synthesis site to action site to regulate growth and responses. (Page 108)
23What is the need for a system of control and coordination in an organism?
Answer & Reference:
To respond appropriately to environmental changes, maintain internal balance, and ensure survival. (Page 100)
24How are involuntary actions and reflex actions different from each other?
Answer & Reference:
- Involuntary actions (e.g., heartbeat, digestion) are continuous and controlled by medulla.
- Reflex actions are sudden, temporary responses to stimuli, controlled by spinal cord. (Page 104)
25Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Answer & Reference:
Nervous System
Hormonal System
Fast, electrical impulses
Slower, chemical signals (hormones)
Acts on specific muscles/glands
Acts on target organs via blood
Short-lived effect
Long-lasting effect
(Page 108–109)
26What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Answer & Reference:
- Sensitive plant: No nerves/muscles; movement by water pressure change in cells.
- Legs: Controlled by nervous system and muscle proteins. (Page 105–106)
27Complete Table 6.1: Some important hormones and their functions.
Answer & Reference:
S.No.
Hormone
Endocrine Gland
Functions
1
Growth hormone
Pituitary gland
Stimulates growth in all organs
2
Thyroxin
Thyroid gland
Regulates metabolism for body growth
3
Insulin
Pancreas
Regulates blood sugar level
4
Testosterone
Testes
Development of male sex organs
5
Oestrogen
Ovaries
Development of female sex organs, regulates menstrual cycle, etc.
6
Adrenaline
Adrenal gland
Prepares body for emergency situations (fight or flight)