Exercises
Q1. What is the difference between a reflex action and walking?
Answer:
A reflex action is an involuntary, automatic response to a stimulus that does not involve conscious thought, such as pulling your hand away from a hot object. It is controlled by the spinal cord (reflex arc) and happens very quickly. Walking, on the other hand, is a voluntary action that requires conscious thought and coordination by the brain. It involves a complex interaction of nerve impulses from various parts of the brain, including the cerebellum for balance and posture.
Q2. What happens at the synapse between two neurons?
Answer:
At the synapse, the electrical impulse traveling along the axon of one neuron triggers the release of chemicals called neurotransmitters. These chemicals cross the synaptic gap (the small space between the two neurons) and bind to receptors on the dendrite of the next neuron. This binding starts a new electrical impulse in the dendrite of the second neuron, allowing the signal to continue from one neuron to another.
Q3. Which part of the brain maintains posture and equilibrium of the body?
Answer:
The cerebellum, which is a part of the hind-brain, is responsible for maintaining posture and equilibrium of the body. It also coordinates voluntary muscle movements to ensure precision, such as walking in a straight line or picking up a pencil.
Q4. How do we detect the smell of an agarbatti (incense stick)?
Answer:
We detect the smell of an agarbatti through olfactory receptors located in the nose. These receptors are specialized tips of nerve cells that detect chemical stimuli (the smell). When the incense stick burns, it releases chemicals into the air. When these chemicals enter the nose, they bind to the olfactory receptors. This sets off a chemical reaction that creates an electrical impulse. The impulse travels along the nerve cells to the fore-brain, where it is interpreted as the smell of the incense stick.
Q5. What is the role of the brain in reflex action?
Answer:
In a reflex action, the reflex arc is formed in the spinal cord itself, allowing for a quick response without directly involving the brain for the initial action. However, the information about the stimulus (e.g., touching a hot object) also travels to the brain via nerves. The brain receives this input and processes it, making us consciously aware of the pain and the situation. So, while the spinal cord coordinates the immediate reflex movement, the brain's role is to receive the information for awareness and possibly to override or modify future responses.