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प्रश्न
A person walks across a room in barefeet and puts his foot on a drawing pin lying on the floor. He lets out a cry. Explain what happens in his nervous system in bringing about this response.
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उत्तर
It is an example of a reflex action. The stimulus in this example is pain which is felt by the foot on touching the drawing pin. This pain is sensed by a receptor in the foot. The receptor triggers an impulse to a sensory neuron which transmits the message to the spinal cord. Here, the impulse is passed on to a relay neuron which, in turn, passes it to a motor neuron. The motor neuron passes the impulse to a muscle in the foot. The muscle, then, contracts and pulls the foot away from the drawing pin.
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संबंधित प्रश्न
Name one gustatory receptor and one olfactory receptor present in human beings.
The diagram given below shows the internal structure of a spinal cord depicting a phenomenon. Study the diagram and answer the questions:
1) Name the phenomenon that is depicted in the diagram. Define the phenomenon.
2) Give the technical term for the point of contact between the two nerve cells.
3) Name the parts numbered 1, 2 and 3.
4) How does the arrangement of neurons in the spinal cord differ from that of the brain?
5) Mention two ways by which the spinal cord is protected in our body.
If we happen to touch a hot object unknowingly, we immediately pull back our hand. What is this type of action known as?
Fill in the following blank with suitable word :
A neuron which carries an impulse to the brain is called a ........... neuron.
Explain the difference between of the following pair of terms :
receptor and effector
A cell (or group of cells) in a sense organ which is sensitive to a particular type of stimulus is called :
(a) interceptor
(b) effector
(c) receptor
(d) acceptor
Which of the following are cerebral reflexes?
(i) a person pulls away his hand on touching a hot object
(ii) a person spits out immediately when a fly enters his mouth while talking
(iii) A person walking bare foot lifts his foot at once on stepping on to a nail
(iv) A person's pupil contracts at once in the presence of bright light
(a) (i) and (ii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (ii) and (iv)
The involuntary actions in the body are controlled by :
(a) medulla in forebrain
(b)medulla in hindbrain
(c) medulla in spinal cord
(d) medulla in midbrain
When we touch a hot plate unknowingly, then this heat is sensed by a receptor P present in our fingers. The receptor triggers and impulse in neuron Q which transmits the message to an organ R which is a part of the central nervous system. Here the impulse is passed on to a neuron S which in turn passes it to a yet another neuron T. The neuron T passes the impulse to a tissue U in our arm. The tissue U then contracts and pulls our hand away from the hot plate.
(a) What is the name of (i) receptor P (ii) neuron Q, and (iii) organ R?
(b) What is (i) neuron S, and (ii) neuron T?
(c) Name the tissue U.
(d) What name is given to the phenomenon in which hand is pulled away quickly from the hot plate?
(e) Name the effector in this whole process.
A cylindrical structure P in our body begins in continuation with medulla and extends downwards. It is enclosed in a bony cage Q and surrounded by membranes R. As many as x pairs of nerves arise from the structure P. The structure P is involved in the reflex actions of our body and conduction of nerve impulses to and from another organ S of our body with which it forms CNS.
(a) Name the structure P.
(b) Name (i) bony cage Q, and (ii) membranes R.
(c) How much is x?
(d) Name the organs S.
(e) What are the reflexes involving structure P only known as?
What is the difference between reflex action and voluntary action?
Two hungry boys (A and B) enter a restaurant and find a table decorated as follows:
Boy B starts salivating but not A. Explain the reason for this difference.
List in tabular form two differences between reflex action and walking.
Define the following:
Reflex action
State whether the following is
Cleaning
State whether the following is
Salivation when food is put in the mouth.
Mention, if the following statement is True or False
A reflex action is a spontaneous response to a stimulus.
Complete the following sentence with appropriate Word
Which of the following is not a natural reflex action?
How is the mode of action in beating of the heart different from reflex actions? Give four examples.
