is reflex action only for spinal nerves??

Question

what about screaming, blinking? the facial nerves are near the brain...how is spinal cord involved in reflex action in these activities?

Answer 1

No, absolutely not. You ask a good question, because when reflexes are discussed, the lecturer unfailingly mentions one of the spinal cord reflexes as an example. This leaves one with the impression that these are the ONLY reflexes. But you rightly point out several other examples of reflexes that DON'T involve the spinal cord.

A reflex is simply a stereotyped reaction to a particular stimulus. Nothing about this definition implies that it has to be spinal in origin.

Examples of spinal cord reflexes include the stretch, or myotactic, reflex (when muscles are rapidly stretched they contract to counter the stretch) and the flexor reflex (where pain elicits a rapid withrdrawal from the stimulus, as in when you prick yourself on the finger).

But there are many other non-spinal reflex. Some examples:
* Pupillary light reflex - pupils constrict in response to light
* Corneal reflex - touching the cornea causes you to blink
* Gag reflex - touching the back of your throat causes you to gag (this is actually part of normal swallowing)

Good thinking!

If you'd like a little more detail, go to http://medicguide.blogspot.com

Answer 2

In the brainstem, alpha motor neurons and other neurons reside within clusters of cells called nuclei, some of which contain the cell bodies of neurons belonging to the cranial nerves. Motor nuclei are found throughout the brainstem,medulla, pons, and midbrain. Alpha motor neurons also are considered part of somatic system.
They innervate many muscles of head and neck and their actions are also reflex actions