Explanation: Insulin, Thyroxin, and Oestrogen are animal hormones. Cytokinin is a plant hormone that promotes cell division.
Q2
The gap between two neurons is called a:
(a) Dendrite (b) Synapse
(c) Axon (d) Impulse
Answer: (b) Synapse
Explanation: The tiny gap between the axon ending of one neuron and the dendrite of the next neuron is called a synapse. Chemical signals (neurotransmitters) cross this gap to transmit impulses.
[Image of synapse between two neurons]
Q3
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: – Forebrain is for thinking.
– Medulla (Hindbrain) controls heart beat.
– Cerebellum (Hindbrain) controls balance and posture.
[Image of human brain diagram parts and functions]
Q4
What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
Function: Receptors are specialized cells in our sense organs that detect stimuli (changes in the environment) like heat, light, sound, taste, or smell and convert them into electrical impulses for the brain.
If receptors fail: We will not be able to detect changes in our surroundings.
Example: If gustatory receptors (taste) are damaged, we cannot taste food. If pain receptors in the hand don’t work, we might burn our hand on a hot object without realizing it, causing severe injury.
Q5
Draw the structure of a neuron and explain its function.
Structure: A neuron consists of:
1. Cell body (Cyton): Contains nucleus.
2. Dendrites: Branch-like structures that receive signals.
3. Axon: Long tail that transmits signals.
4. Nerve Ending: Transmits signal to the next neuron via synapse.
[Image of neuron structure diagram]
Function: It detects information from the environment and transmits it to the brain/spinal cord in the form of electrical impulses for processing and response.
Q6
How does phototropism occur in plants?
Phototropism is the movement of a plant part towards light.
Mechanism: 1. When light falls on one side of a shoot, the growth hormone Auxin diffuses towards the shady side.
2. High concentration of Auxin stimulates cells on the shady side to grow longer than the cells on the light side.
3. This unequal growth causes the stem to bend towards the light.
Q7
Which signals will get disrupted in case of a spinal cord injury?
1. Reflex Actions: Spinal cord is the center for all reflex arcs. Injury will disrupt immediate responses (like pulling hand from heat).
2. Sensory Signals: Impulses from body parts to the brain will be blocked.
3. Motor Signals: Instructions from the brain to muscles (for walking/moving) will be disrupted, leading to paralysis.
Q8
How does chemical coordination occur in plants?
Unlike animals, plants do not have a nervous system. They coordinate via Phytohormones (Chemical signals).
1. Hormones like Auxins, Gibberellins, and Cytokinins are synthesized at shoot/root tips.
2. They diffuse to specific target cells.
3. They regulate growth, cell division, and response to stimuli (light, gravity) by changing cell size or turgor.
Q9
What is the need for a system of control and coordination in an organism?
1. Survival: To detect and respond to changes (danger, food) in the environment efficiently.
2. Harmony: Different organs work together. (e.g., When running, muscles need more oxygen, so lungs breathe faster and heart beats faster. This synchronization is done by the nervous system).
3. Growth: To ensure controlled and directional growth (in plants and animals).
Q10
How are involuntary actions and reflex actions different from each other?
Reflex Action
Involuntary Action
Sudden, automatic response to a specific stimulus (e.g., touching hot plate).