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The Pathway of a Nerve Impulse
Introductory Note: Knowledge of the human nervous
system and familarisation with the key terms associated
with it is an essential part of training in many therapies
- such as Massage, Aromatherapy, Accupuncture, Shiatsu,
and many others.
This page summarises basic information about the functioning of
nerves.
In a general case, the pathway of a nerve impluse
may be summarised as in the following diagram:
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Figure (1): The Pathway of a Nerve Impulse
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- This indicates that the first event in this sequence is
some "Stimulus". ("Stimuli"
is the plural form, referring to more than one
stimulus.)
In this context, a stimulus is something that
human sensory receptors are able to detect.
Examples may include: Sounds; Physical contact; Tastes; Visual
stimuli, etc..
- The next stage in the pathway is the "Sensory Receptors"
sensing the stimulus.
These receptors are located all over the body but some types of receptors are
in specific areas of the body (e.g. taste receptors in the mouth).
- Sensory neuron(s) then transmit information from the
sensory receptor(s) to the Central Nervous System (i.e.
the brain and spinal cord, sometimes referred to in the
abbreviated form: C.N.S.). This is happens because peripheral
nerves all connect to the spinal cord via the network of
nerves within the nervous system.
- The information so received by the C.N.S. is further transmitted
by relay neurone(s) with the C.N.S.
This is shown in more detail in Figure (2), below.
The information may or may not be processed in the brain.
Some stimuli lead to "reflex responses" that
can be described in terms of the "Simple Reflex Arc",
whereas other stimuli (such as all visual stimuli) always
involve processing by the brain. More information about the "Simple Reflex Arc" is
included in Figure (2), below.
Following either "Simple Reflex Arc" response,
or processing by the brain, neural "instructions"
may be sent via a motor neurone to an effector
(that is usually a muscle or gland). In this way,
the effector is instructed to take action. This
action may be physical movement of a muscle (and
so possibly also a limb), or some chemical action
by a gland. Whatever the consequent action, this
has occurred due to the function of the nervous
system, in response to the initial stimulus (or
stimuli).
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A "Simple Reflex Arc"
The following diagram illustrates the sequence of events described
above in more detail, specifically for the case of the "simple
reflex arc". Theefore this diagram shows a vertebra of the
spine, but does not also include the brain.
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Figure (2): "Simple Reflex Arc"
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See also information
about Neurons
and about Diseases
and Disorders of the Nervous System.
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