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The nervous sytem and reflexes

  1. Jan 18, 2005 #1
    the nervous system

    Dear sir,

    i would like to thank you for your answers , and i know that i ask too many questions, but what can i do, whenever you answer my questions another question come out. So excuse me for that. And again i thank for your patient and your brilliant answers.

    i have another questions today about the nerveous system:

    1.actually i want to know what's the different between the reflex action and the involuntary action or (the involuntary action is kind of the reflex action)
    i really don't know the different and am really confused.

    2.what is the different between an enzyme and a hormone?
    if possible could you just point out the differences between them in point
    Last edited: Jan 18, 2005
  2. jcsd
  3. Jan 18, 2005 #2


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    An enzyme is a protein (on some occasion it is an RNA molecule) that helps to catalyze chemical reaction by inducing or accelerating the reation. An enzyme is a catalyst.

    Hormones can be protein or cholesterol based and it is secreted. Hormones act as messengers in the body. Hormones will activate genes by interacting with their targets.
  4. Jan 18, 2005 #3
    1. a voluntary reflex action is somatic , such as those done by skeletal muscle
    an involuntary reflex is autonomous , such as the cardiac and smooth muscle

    *You should research some things about the somatic and autonomic divisions of the peripheral nervous system (PNS). I think you could find some useful information here.

    2. An enzyme is a catalyst that is substrate (e.g. lactose) specific. Enzymes aid in many biochemical processes throughout the body.

    A hormone is a "messenger" that is sent out from a specific organ (there are many) in the endocrine system. Each hormone has a target cell, a cell in which it directly effects the function.

    The main difference is that enzymes catalyze processes in the body and hormones affect the functioning of various organs in the body.

    *You may also want to research neurotransmitters if you're interested.

    EDIT: Sorry about the overlap, I was typing my response while ian smith posted. I'm certainly not trying to step on any toes.
    Last edited: Jan 18, 2005
  5. Jan 19, 2005 #4
    The reflex action

    i know that the reflex action divided into two types 1.voluntary reflex action and 2.involuntary reflex action.

    but my question was :
    (What is the different between the involuntary action and the reflex action)
    that is what i want to know, or maybe i understood it wrong? :confused:

    so please i want a clear explanation, if it possible

    thank you
  6. Jan 19, 2005 #5


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    In the future, when you need additional clarification on a previously asked question, it is best to post that in the ongoing thread rather than create a new thread. It helps keep the continuity of answers.

    That said...

    Are these questions based on material you are learning for a class? If so, you should go back and reread the section in your textbook on this. A reflex is involuntary. There is no such thing as a voluntary reflex. Reflexes are intended to be quick responses.

    There can also be other involuntary responses that are NOT reflexes. A reflex is a response that does not require processing in the brain to occur, but instead uses a shorter pathway of neurons passing through the spinal cord and back out to the appropriate muscle to respond very quickly, such as to a harmful stimulus (i.e., pulling your hand away from a hot stove). Other involuntary responses are not reflexes, but are part of your autonomic nervous system. One example would be breathing, which requires signals coming from the brainstem.

    I suggest you take a step back and refresh your memory on the different components of the nervous system first. Make sure you understand terms such as autonomic, sympathetic, parasympathetic, sensory neuron, motor neuron, interneuron, and efferent vs afferent. Provide us with what you think the definitions of each of those terms is. Once we're sure you understand those correctly (or help clarify anything you've misunderstood), we can take it from there to explain reflexes better.
  7. Jan 19, 2005 #6
    A study was done on 6 month old humans to see if a certain reflex was present at such an early age. The infants, who could crawl, were let go to crawl over a plate of glass that had a drop off visible under it. The drop off stimulated a reflex in the infants to stop and not cross (or not drop!) into the seemingly open space.

    This autonomic urge to stop was a reflex based on visual stimulus. The stimulus triggered a response which may have been stored genetically (genetic memory??) as a reflex that is specific to the visual stimulus of a drop off in front of the infant.

    Involuntary action is, as someone has stated above, usually associated with stimuli such as lack of oxygen, lack of food, the presence of food in the throat or mouth or stomache, the presence of blood in the heart, oxygen in the lungs and so on and so forth. These types of stimuli are what generate autonomic actions known as breathing, heart valves opening and closing, tear ducts washing the eyes and so on and so forth.

    The commonality and what may be confusing you about these two types of response in an organism is that they are both in response to specific stimulus. The difference may seem superficial but, to begin with it is that the stimuli coming from external sources evoke a reflex whereas the stimuli coming from internal to the organism evoke an autonomic response. Reflexs may also respond from a slightly more evolved part of the brain (cerebral cortex) whereas autonomic responses originate in a more primitive area of the brain (cerebellum).

    As recommended earlier studying neurotransmitters may also be of interest with regard to this topic.

    Last edited: Jan 19, 2005
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