Control and Coordination - Q&A
1. Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin.
Answer: (d) Cytokinin.
Explanation: Insulin, Thyroxin, and Oestrogen are animal hormones. Cytokinins are plant hormones that promote cell division, especially in areas of rapid growth like fruits and seeds.
2. The gap between two neurons is called a
(a) dendrite.
(b) synapse.
(c) axon.
(d) impulse.
Answer: (b) synapse.
Explanation: A synapse is the small gap between the axon ending of one neuron and the dendrite of the next neuron. Signals cross this gap using chemicals called neurotransmitters.
3. The brain is responsible for
(a) thinking.
(b) regulating the heart beat.
(c) balancing the body.
(d) all of the above.
Answer: (d) all of the above.
Explanation: The brain controls various functions: the forebrain is for thinking, the medulla (hindbrain) regulates involuntary actions like heartbeat, and the cerebellum (hindbrain) maintains body balance.
4. What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Answer:
Function: Receptors are specialized cells in sense organs (eyes, ears, nose, tongue, skin) that detect stimuli (changes in the environment) like light, sound, smell, taste, heat, etc., and send signals to the brain/spinal cord.
If receptors don't work properly:
1. Safety Hazard: If pain receptors in the skin don't work, we might touch a hot object and burn ourselves without realizing it.
2. Loss of Senses: If gustatory (taste) receptors fail, we won't be able to taste food. If olfactory (smell) receptors fail, we won't detect smells like gas leaks.
5. Draw the structure of a neuron and explain its function.
Answer:
Structure: A neuron consists of a cell body (containing the nucleus), dendrites (branch-like structures receiving signals), and an axon (a long tail transmitting signals).
Function:
1. Reception: Dendrites receive information (chemical signals) from other neurons or receptors.
2. Conduction: The information travels as an electrical impulse along the axon.
3. Transmission: At the end of the axon, the impulse releases chemicals (neurotransmitters) into the synapse to pass the signal to the next neuron.
6. How does phototropism occur in plants?
Answer: Phototropism is the bending of a plant towards light.
Mechanism:
1. When sunlight falls on one side of the shoot, a growth hormone called auxin is synthesized at the shoot tip.
2. Auxin diffuses towards the shady side of the shoot.
3. This higher concentration of auxin stimulates the cells on the shady side to grow longer than the cells on the sunny side.
4. As a result, the shoot bends towards the light.
7. Which signals will get disrupted in case of a spinal cord injury?
Answer:
1. Reflex Actions: The spinal cord acts as the centre for reflex arcs. Injury disrupts these quick, involuntary responses (e.g., pulling hand away from heat).
2. Sensory Signals: Signals from the body (skin, muscles) won't reach the brain.
3. Motor Signals: Instructions from the brain won't reach the body parts, leading to paralysis.
8. How does chemical coordination occur in plants?
Answer: Plants do not have a nervous system, so they rely entirely on chemical coordination using phytohormones (plant hormones).
1. Hormones like auxins, gibberellins, cytokinins, and abscisic acid are produced in specific parts of the plant.
2. They diffuse to the site of action.
3. They regulate growth, development, and responses to the environment (e.g., bending towards light, dropping leaves).
9. What is the need for a system of control and coordination in an organism?
Answer:
1. Survival: To respond appropriately to changes in the environment (stimuli) for protection (e.g., running from danger).
2. Synchronization: Multicellular organisms have complex body systems. Coordination ensures all organs work together efficiently (e.g., heart beats faster when we run).
3. Growth & Development: To regulate growth phases correctly.
10. How are involuntary actions and reflex actions different from each other?
Answer:
| Feature | Involuntary Action | Reflex Action |
|---|---|---|
| Control | Controlled by the Medulla (Hindbrain). | Controlled mainly by the Spinal Cord. |
| Speed | Relatively slower. | Extremely fast and sudden. |
| Stimulus | Does not necessarily require an external stimulus (e.g., heartbeat). | Always a response to a sudden external stimulus (e.g., touching hot plate). |
| Examples | Heart beating, breathing, digestion. | Pulling hand from fire, knee-jerk. |
11. Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Answer:
| Feature | Nervous Mechanism | Hormonal Mechanism |
|---|---|---|
| Signal Type | Electrical impulses (and chemical neurotransmitters). | Chemical messengers (Hormones). |
| Transmission | Through nerve fibres (neurons). | Through blood stream. |
| Speed | Very fast. | Slow. |
| Duration | Short-lived effect. | Long-lasting effect. |
| Target | Specific cells/organs connected by nerves. | Target organs can be far away; widespread effect. |
12. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Answer:
| Feature | Movement in Sensitive Plant (Mimosa) | Movement in Our Legs |
|---|---|---|
| Mechanism | Change in water concentration (turgor pressure) in cells (swelling/shrinking). | Contraction and relaxation of specialized muscle proteins. |
| Control | Chemical control (Electrical-chemical signals). No nervous system. | Nervous control (Brain/Spinal cord sends signals to muscles). |
| Speed | Slow compared to animal muscle movement. | Fast and voluntary. |
| Growth | This specific movement is not growth-related (Nastic movement). | Not growth-related (Locomotion). |