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When dust falls in our eyes, the eyelids...

When dust falls in our eyes, the eyelids close immediately not waiting for our willingness, on touching a hot pan, the hand is withdrawn rapidly. Do you know how this happens?

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On touching a hot pan, the hand is withdrawn rapidly, This is called reflex action.
The spinal cord remains as a connecting functional nervous structure in between the brain and effector organs. But sometimes when a very quick response is needed, the spinal cord can effect motor initiation as the brain and brings about an effect. This rapid action by spinal cord is called reflex action. It is a fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus. The nervous elements involved in carrying out the reflex action constitute a reflex arc or in other words the pathway followed by a nerve impulse to produce· a reflex action is called a reflex arc.
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Take a small stone. Hold it in your hand. We know that the force gravity due to the earth acts on each and every object. When we were holding the stone in our hand, the stone was experiencing this force, but it was balanced by a force that we were applying onn it in the opposite direction. As a result, the stone remained at rest. Once we release the stone from our hands the only force that acts onit is the gravitational force of the earth and the stone falls down under its influence. Whenever an object moves under the influence of the force of gravity alone, it is said to be falling freely. Thus the released stone is in a free fall. In free fall, the initial velocity of the object is zero and goes on increasing due toi acceleration due to gravity of the earth. During free fall, the frictional force due to air opposes the motion of the object anda buoyant force also acts on the object. Thus, true free fall is posible only in vacuum. For a freely falling object, the velocity on reachign the earth and the time taken for it can be calculated by using Newton's eqwuations of motion. For free fall the initial velocity u=0 and the acceleration a=g . Thus, we can write the equations as v="gt",s=1/2"gt"^(2),v^(2)=2gs For calculating the motion of an object thrown upwards, acceleration is negative, i.e. in a direction opposite ot the velocity and is taken to be -g. The magnitude of g is the same but the velocity of the object decreases due to -ve acceleration. The moon and the artificial satellites are moving only under the influence of the gravitational field of the earth. Thus they are in free fall. Which force acts on the stone when held in the hand?

Take a small stone. Hold it in your hand. We know that the force gravity due to the earth acts on each and every object. When we were holding the stone in our hand, the stone was experiencing this force, but it was balanced by a force that we were applying on it in the opposite direction. As a result, the stone remained at rest. Once we release the stone from our hands the only force that acts on it is the gravitational force of the earth and the stone falls down under its influence. Whenever an object moves under the influence of the force of gravity alone, it is said to be falling freely. Thus the released stone is in a free fall. In free fall, the initial velocity of the object is zero and goes on increasing due to acceleration due to gravity of the earth. During free fall, the frictional force due to air opposes the motion of the object and a buoyant force also acts on the object. Thus, true free fall is possible only in vacuum. For a freely falling object, the velocity on reaching the earth and the time taken for it can be calculated by using Newton's equations of motion. For free fall the initial velocity u=0 and the acceleration a=g . Thus, we can write the equations as v="gt",s=1/2"gt"^(2),v^(2)=2gs For calculating the motion of an object thrown upwards, acceleration is negative, i.e. in a direction opposite to the velocity and is taken to be -g. The magnitude of g is the same but the velocity of the object decreases due to -ve acceleration. The moon and the artificial satellites are moving only under the influence of the gravitational field of the earth. Thus they are in free fall. Which force acts on the stone in free fall after you release it?

Take a small stone. Hold it in your hand. We know that the force gravity due to the earth acts on each and every object. When we were holding the stone in our hand, the stone was experiencing this force, but it was balanced by a force that we were applying onn it in the opposite direction. As a result, the stone remained at rest. Once we release the stone from our hands the only force that acts onit is the gravitational force of the earth and the stone falls down under its influence. Whenever an object moves under the influence of the force of gravity alone, it is said to be falling freely. Thus the released stone is in a free fall. In free fall, the initial velocity of the object is zero and goes on increasing due to acceleration due to gravity of the earth. During free fall, the frictional force due to air opposes the motion of the object anda buoyant force also acts on the object. Thus, true free fall is posible only in vacuum. For a freely falling object, the velocity on reachign the earth and the time taken for it can be calculated by using Newton's eqwuations of motion. For free fall the initial velocity u=0 and the acceleration a=g . Thus, we can write the equations as v="gt",s=1/2"gt"^(2),v^(2)=2gs For calculating the motion of an object thrown upwards, acceleration is negative, i.e. in a direction opposite ot the velocity and is taken to be -g. The magnitude of g is the same but the velocity of the object decreases due to -ve acceleration. The moon and the artificial satellites are moving only under the influence of the gravitational field of the earth. Thus they are in free fall. What is free fall?

Take a small stone. Hold it in your hand. We know that the force gravity due to the earth acts on each and every object. When we were holding the stone in our hand, the stone was experiencing this force, but it was balanced by a force that we were applying on it in the opposite direction. As a result, the stone remained at rest. Once we release the stone from our hands the only force that acts on it is the gravitational force of the earth and the stone falls down under its influence. Whenever an object moves under the influence of the force of gravity alone, it is said to be falling freely. Thus the released stone is in a free fall. In free fall, the initial velocity of the object is zero and goes on increasing due to acceleration due to gravity of the earth. During free fall, the frictional force due to air opposes the motion of the object and buoyant force also acts on the object. Thus, true free fall is possible only in vacuum. For a freely falling object, the velocity on reaching the earth and the time taken for it can be calculated by using Newton's equations of motion. For free fall the initial velocity u=0 and the acceleration a=g . Thus, we can write the equations as v="gt",s=1/2"gt"^(2),v^(2)=2gs For calculating the motion of an object thrown upwards, acceleration is negative, i.e. in a direction opposite to the velocity and is taken to be -g. The magnitude of g is the same but the velocity of the object decreases due to -ve acceleration. The moon and the artificial satellites are moving only under the influence of the gravitational field of the earth. Thus they are in free fall. What is the initial velocity and what is the effect of gravitational acceleration on the object in free fall?

Take a small stone. Hold it in your hand. We know that the force gravity due to the earth acts on each and every object. When we were holding the stone in our hand, the stone was experiencing this force, but it was balanced by a force that we were applying onn it in the opposite direction. As a result, the stone remained at rest. Once we release the stone from our hands the only force that acts onit is the gravitational force of the earth and the stone falls down under its influence. Whenever an object moves under the influence of the force of gravity alone, it is said to be falling freely. Thus the released stone is in a free fall. In free fall, the initial velocity of the object is zero and goes on increasing due to acceleration due to gravity of the earth. During free fall, the frictional force due to air opposes the motion of the object anda buoyant force also acts on the object. Thus, true free fall is posible only in vacuum. For a freely falling object, the velocity on reachign the earth and the time taken for it can be calculated by using Newton's eqwuations of motion. For free fall the initial velocity u=0 and the acceleration a=g . Thus, we can write the equations as v="gt",s=1/2"gt"^(2),v^(2)=2gs For calculating the motion of an object thrown upwards, acceleration is negative, i.e. in a direction opposite ot the velocity and is taken to be -g. The magnitude of g is the same but the velocity of the object decreases due to -ve acceleration. The moon and the artificial satellites are moving only under the influence of the gravitational field of the earth. Thus they are in free fall. Write kinematic equations used in free fall?

When we touch a cactus unknowingly,we get pricked by the throns.We withdraw our hands immediately.Which type of neuron gets activated first.

Answer briefly : (a) How do you perceive the colour of an object ? (b) Which part of our body helps us in maintaining the body balance ? (c) How does the eye regulate the amount of light that falls on the retina.

PREMIERS PUBLISHERS-NEURAL CONTROL AND CO-ORDINATION -Other Important Question & Answers (II. Answer the following:)
  1. (i) Describe the structure of spinal cord. (ii) What are heart sound...

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  2. In what way the grey and white matter of the brain and the spinal cord...

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  3. When dust falls in our eyes, the eyelids close immediately not waiting...

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  4. What are the functional components of a reflex arc? Explain.

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  5. Explain the type of reflexes.

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  6. What is peripheral nervous system?

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  7. Write about cranial nerves which are arising from the brain coming und...

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  8. How many spinal nerves emerged from the spinal cord and how are they n...

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  9. What is somatic neural system? Write its functions.

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  10. What is ANS ? Explain the components of ANS.

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  11. Name the neural systems coming under autonomic system.

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  12. Differentiate between sympathetic and parasympathetic Neural system.

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  13. Name the senses occur in our brain.

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  14. Classify receptors based on their location.

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  15. What are the muscles involved in placing the eyeball held its position...

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  16. What are the functions of the extrinsic muscle of the eye?

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  17. What are the functions of the eye lids?

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  18. What are the glands present related with the eyes? What is it function...

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  19. Explain the structure of human eye.

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  20. Explain the mechanism of vision.

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