Control and Coordination-Exercises
Biology - Exercise
Q1. Plant Hormones
Which of the following is a plant hormone?
- Insulin
- Thyroxin
- Oestrogen
- Cytokinin
Answer:
(d) Cytokinin
Cytokinin is a plant hormone that promotes cell division (cytokinesis) in plant roots and shoots. It helps in growth, development, and delay of leaf senescence. Insulin, Thyroxin, and Oestrogen are animal hormones.
Q2. Synapse
The gap between two neurons is called a?
- Dendrite
- Synapse
- Axon
- Impulse
Answer:
(b) Synapse
A synapse is the tiny gap or junction between two neurons where nerve impulses are transmitted.
- The axon terminal releases neurotransmitters into this gap.
- These chemicals carry the nerve impulse across the synapse to the next neuron.
Q3. Functions of the Brain
The brain is responsible for:
- Thinking
- Regulating the heartbeat
- Balancing the body
- All of the above
Answer:
(d) All of the above
- Thinking: Controlled by the cerebrum (intelligence, reasoning, memory).
- Regulating Heartbeat: Controlled by the medulla oblongata (involuntary actions).
- Balancing Body: Controlled by the cerebellum (posture, coordination).
- All of the above: Functions are performed by different brain parts.
Q4. Function of Receptors
What is the function of receptors in our body? What happens if they fail?
Function of Receptors:
Specialized cells in sense organs detect stimuli (light, sound, touch, temperature, smell) and send information to the brain or spinal cord.
Examples:
- Photoreceptors detect light.
- Thermoreceptors detect temperature.
- Chemoreceptors detect smell and taste.
- Mechanoreceptors detect touch and pressure.
Consequences of Receptor Failure:
- Blindness: damaged photoreceptors.
- Deafness: damaged sound receptors.
- Loss of sensation: touch receptors fail.
- Inability to smell or taste: chemoreceptors fail.
Proper functioning of receptors is essential for coordination, protection, and survival.
Q5. Structure of a Neuron
Draw the structure of a neuron and explain its function.
Main Parts of a Neuron:
- Dendrites: Short branches that receive impulses and transmit to the cell body.
- Cell Body (Soma): Contains nucleus, controls metabolism, processes impulses.
- Axon: Carries impulses away from cell body; may have myelin sheath for speed.
- Axon Terminals: Ends of axon transmit impulses to next neuron via synapse.
Q6. Phototropism in Plants
Answer:
Phototropism is plant growth towards light (positive phototropism) to maximize photosynthesis.
How Phototropism Occurs:
- Detection of Light: Cells in the shoot tip detect light direction.
- Role of Auxin: Auxin moves to shaded side, promoting elongation.
- Differential Growth: Shaded side cells elongate more; light-facing cells grow less.
- Bending Towards Light: Stem bends toward light due to uneven growth.
Q7. Signals Disrupted by Spinal Cord Injury
Answer:
A spinal cord injury disrupts communication between the brain and body. Both sensory, motor, and autonomic signals are affected, leading to loss of movement, sensation, and impaired body functions below the injury site.
Q8. Chemical Coordination in Plants
Answer:
Plants coordinate activities through hormones (phytohormones) that regulate growth, development, and response to stimuli.
How It Happens:
- Synthesis: Produced in shoot tips, roots, leaves, seeds, or fruits.
- Transport: Moves via phloem, xylem, or cell-to-cell diffusion.
- Action: Binds to target cells, triggering growth, division, or differentiation.
Q9. Need for Control and Coordination System
Answer:
Control and coordination systems ensure body parts work together efficiently and maintain homeostasis.
- Integration of Activities: Organs and tissues coordinate for movement and functions.
- Response to Stimuli: Organisms react appropriately to environmental changes.
- Regulation: Processes like heartbeat, breathing, digestion, and growth are precisely controlled.
- Survival & Adaptation: Helps organisms adjust to changing conditions (e.g., phototropism, shelter-seeking).
Q10. Involuntary vs Reflex Actions
Answer:
Involuntary and reflex actions are automatic responses. Involuntary actions are controlled by the brain and slower, while reflex actions are rapid, protective, and mainly controlled by the spinal cord.
| Feature | Involuntary Actions | Reflex Actions |
|---|---|---|
| Definition | Automatic actions controlled by the brain without conscious effort | Rapid, automatic responses to a stimulus, often protective |
| Control Center | Brain | Spinal cord (sometimes brain involved) |
| Speed | Generally slower | Very fast, almost instantaneous |
| Examples | Heartbeat, breathing, food movement | Knee-jerk, pulling hand from hot object |
| Purpose | Maintains vital body functions | Protects body from harm |
Q11. Nervous vs Hormonal Mechanisms
Answer:
Nervous and hormonal systems both control and coordinate activities but differ in speed, duration, and method.
| Feature | Nervous System | Hormonal System |
|---|---|---|
| Message Type | Electrical impulses | Chemical messengers (hormones) |
| Transmission Medium | Neurons | Bloodstream |
| Speed | Very fast | Slow |
| Duration | Short-lived | Long-lasting |
| Specificity | Highly specific | Less specific |
| Examples | Reflexes, muscle movement | Growth hormone, insulin |
| Control | Voluntary & involuntary | Mostly involuntary |
Q12. Movement: Sensitive Plant vs Human Legs
Answer:
Movement in sensitive plants is turgor-based, while human leg movement is muscle-driven.
| Feature | Sensitive Plant | Human Legs |
|---|---|---|
| Type of Movement | Turgor or nastic movement | Locomotion using skeletal muscles |
| Cause of Movement | Rapid turgor pressure change | Contraction/relaxation of muscles |
| Speed | Fast for plants (seconds) | Fast and powerful |
| Control | Involuntary, chemical signals | Voluntary, nervous system |
| Energy Source | Water pressure (turgor) | Chemical energy (ATP) |
| Purpose | Defense mechanism | Movement and performing tasks |
