853346
Description
Pain
- Important defence
mechanism against
tissue damage
- As a protective mechanism pain does have some shortcomings:
- Irradiation can cause extensive
tissue damage but is not illicit pain
at the time of stimulation
- The pain of sunburn does not serve as a warning
function but occurs after thevent
- Pain associated with cancers does
generally not occur until the cancer is very
extensive
- Irradiation can cause extensive
tissue damage but is not illicit pain
at the time of stimulation
- As a protective mechanism pain does have some shortcomings:
- The location and intensity of
the pain stimulus will affect the
quality and severity of the
perceived pain
- Known as the Specificity Theory, Rene Descartes,
generally correct when applied to certain types of injury
and the acute pain associated with them.
- Does not allow for
psychologic
contributions, such as
prior experience of
pain, and emotions.
- Does not allow for
psychologic
contributions, such as
prior experience of
pain, and emotions.
- Known as the Specificity Theory, Rene Descartes,
generally correct when applied to certain types of injury
and the acute pain associated with them.
- Pain signals are transmitted in
myelinated A Delta and unmyelinated C
fibres
- These are ascending tracts and
carry sensory information from
the periphery to the different
areas of the brain, such as the
cerebral cortext, cerebellum and
brain stem
- The ascending sensory pathways can be divided into:
- Dorsal column medial lemniscal pathway
- Mediate tactile and
kinaesthetic information which
is highly discriminatory and
can be precisely localised
- A Delta fibres are
thought to cause
sharp pricking
sensations
- Faster conducting
- Faster conducting
- Known as epicritic
- A Delta fibres are
thought to cause
sharp pricking
sensations
- Mediate tactile and
kinaesthetic information which
is highly discriminatory and
can be precisely localised
- Spinothalamic tract
- Transmits important
information concerning
pain and temperature
but poor localisation
and poor discrimination
of the stimulus
- C Fibres are
thought to
transmit duller
burning or aching
sensation
- Slower conducting
- Slower conducting
- Known as protopathic
- C Fibres are
thought to
transmit duller
burning or aching
sensation
- Transmits important
information concerning
pain and temperature
but poor localisation
and poor discrimination
of the stimulus
- Dorsal column medial lemniscal pathway
- The ascending sensory pathways can be divided into:
- These are ascending tracts and
carry sensory information from
the periphery to the different
areas of the brain, such as the
cerebral cortext, cerebellum and
brain stem
- The thalamic nuclei influence the
conscious appreciation of pain
- Substance P is a
neurotransmitter or
neuromodulator identified
in various parts of the NS
including the substantia
gelatinosa of the dorsal
horn
- Noxious stimulation causes the
release of substance P from dorsal
root afferents
- Noxious stimulation causes the
release of substance P from dorsal
root afferents
- Other peptides seem to posess
anelgesic properties; these endogenous
substances act similar to morphine,
known as enkephalins and endorphins
- Discovered by Hughes et al., 1975
- Enkephalins and endorphin
existance goes some way to
explaining the phenomena of
Placebo Response, where an
individual percieves pain relief even
though no anelgesic agent is
administerd
- The expectation of pain relief is sufficent to
release psychogenically the endogenous
opiates
- The expectation of pain relief is sufficent to
release psychogenically the endogenous
opiates
- Enkephalins and endorphin
existance goes some way to
explaining the phenomena of
Placebo Response, where an
individual percieves pain relief even
though no anelgesic agent is
administerd
- These endogenous opiates have been shown to inhibit
prostaglandin formation, prostaglandins are considered
chemical stimuli for pain
- Have been shown to inhibit
the actions of a number of
transmitters including
substance P
- Have been shown to inhibit
the actions of a number of
transmitters including
substance P
- Discovered by Hughes et al., 1975
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