Please answer
Q.A student reaching for a book on a bookshelf pricks his finger on the sharp point of a nail. He pulls his hand away very quickly. 
a.State the type of response which has occurred.
b.What is the effector in this response?
c.Name the type of nerve cell which links the central nervous system to the effector
d.How are involuntary actions and reflex actions different from each other?

Dear student.
Please find the solution below.

a. The automatic action or response provoked by a stimulus is known as a reflex action. The reflex actions, however, show sudden responses and do not involve any thinking.

b. Effector here is the muscle of the arm.

c. Motor nerve links CNS to the effector. Sensory neurons carry information from the sensory organs to brain or spinal cord while as motor neurons carry messages from the brain or spinal cord to the muscle or glands.

Involuntary actions cannot be consciously controlled. For example, we cannot consciously control the movement of food in the alimentary canal. These actions are however directly under the control of the brain. On the other hand, the reflex actions such as closing of eyes immediately when bright light is focused show sudden response and do not involve any thinking. This means that unlike involuntary actions, the reflex actions are not under the control of brain.


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a. Reflex reaction
d. Involuntary action are those carried out all the time, and out of our control.
Reflex reaction only happens on exposure to an external stimuli.
The rest I don't know because I haven't learnt this lesson. So I tried to answer what all I knew.
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