1.What are the different types of pain (and pain
fibers)?
Somatic sensory system different from other sensory systems in 2 ways:
1. Its receptors are distributed throughout the body rather than being
concentrated at small, specialized locations.
2. It responds to many different kinds of stimuli. You can think of it as a
group of at least 4 senses rather than just one (senses of: touch,
temperature, pain and body position)
Nociceptors: free, branching, unmyelinated nerve endings that signal that
body tissue is being damaged or is at risk of being damaged.
Pain= the feeling, perception of unbearable sensations
Nociception= the sensory process that provides the signals that trigger pain
Nociceptors are activated by stimuli that have the potential to cause tissue
damage
tissue damage can result from strong mechanical stimulation, extremes in
temperature, oxygen deprivation and exposure to certain chemicals.
The membranes of nociceptors contain ion channels that are activated by
these type of stimuli
Each nociceptor has its own receptive field one nociceptor will transduce
the signal of pain when a particular region in skin is stimulated
- The size of receptive fields varies throughout the body and is
often overlapping with neighboring fields
Location: present in most body tissue (skin, bone, muscle, most internal
organs, blood vessels, heart) BUT ABSENT in the brain itself, except for the
meninges
Example: stepping on something sharp=
The stretching or bending of the nociceptor membrane activates
mechanically gated ion channels that cause the cell to depolarize and
generate action potentials
+ damaged cells at the site of injury can release several substances that
cause ion channels on nociceptor membranes to open
,Types of nociceptors:
- Polymodal nociceptors: respond to mechanical, thermal and
chemical stimuli
- Mechanical nociceptors: selective responses to strong
pressure
- Thermal nociceptors: selective responses to burning heat or
extreme cold
- Chemical nociceptors: selective responses to histamine and
other chemicals
How is pain defined?
3 main types of pain:
1) Nociceptive pain: caused by stimulation or sensitization of peripheral
nociceptors. recognizable, well localized, extensive triggering of
nociceptors
2) Neuropathic pain: lesion of PNS
3) Psychogenic pain: pain that persist despite the lack of any identified
underlying physical cause
- Hyperalgesia:
Enhanced sensation of pain at normal threshold stimulation exaggerated
responses to stimuli. Occurs due to sensitization of nerves in and around the
damaged area
Sensitization= the nerves have a reduced threshold for firing as a results of
noxious stimuli
- Central sensitization leads to hyperexcitability of second-order
neurons within the dorsal horn of the spinal cord
Primary hyperalgesia: occurs within the area of damaged tissue, but
tissues surrounding a damaged area may become supersensitive as well by
the process of secondary hyperalgesia
, - Allodynia:
Here a stimulus not normally painful is perceived as painful
Dynamic (pain of object moving across your skin), tectal (touch or pressure)
and thermal (changes in temperature)
- Analgesia:
Loss of sensation of pain
Sensitization: response in which the pain pathways become more sensitive
2 types of sensitizations:
2. Peripheral sensitizations: occurs in response to the release of
inflammatory molecules such as histamine, prostaglandins these
substances sensitize nociceptors by creating an inflammatory soup that
enhances pain sensitivity by reducing the threshold of nociceptor
activation
3. Central sensitizations: here nociceptive-specific neurons
progressively increase their response to repeated non-painful stimuli,
develop spontaneous activity, and increase the area of the body that is
involved in pain.
What is the anatomy of the nociceptive system?
There are 4 major processes:
1. Transduction= the processes by which tissue-damaging stimuli
activate nerve endings
2. Transmission= the relay functions by which the message is carried
from the site of tissue injury to the brain regions underlying perception
3. Modulation= Neural process that acts specifically to reduce activity in
the transmission system
4. Perception= subjective awareness produced by sensory signals,
involves the integration of many sensory messages into a coherent and
meaningful whole
fibers)?
Somatic sensory system different from other sensory systems in 2 ways:
1. Its receptors are distributed throughout the body rather than being
concentrated at small, specialized locations.
2. It responds to many different kinds of stimuli. You can think of it as a
group of at least 4 senses rather than just one (senses of: touch,
temperature, pain and body position)
Nociceptors: free, branching, unmyelinated nerve endings that signal that
body tissue is being damaged or is at risk of being damaged.
Pain= the feeling, perception of unbearable sensations
Nociception= the sensory process that provides the signals that trigger pain
Nociceptors are activated by stimuli that have the potential to cause tissue
damage
tissue damage can result from strong mechanical stimulation, extremes in
temperature, oxygen deprivation and exposure to certain chemicals.
The membranes of nociceptors contain ion channels that are activated by
these type of stimuli
Each nociceptor has its own receptive field one nociceptor will transduce
the signal of pain when a particular region in skin is stimulated
- The size of receptive fields varies throughout the body and is
often overlapping with neighboring fields
Location: present in most body tissue (skin, bone, muscle, most internal
organs, blood vessels, heart) BUT ABSENT in the brain itself, except for the
meninges
Example: stepping on something sharp=
The stretching or bending of the nociceptor membrane activates
mechanically gated ion channels that cause the cell to depolarize and
generate action potentials
+ damaged cells at the site of injury can release several substances that
cause ion channels on nociceptor membranes to open
,Types of nociceptors:
- Polymodal nociceptors: respond to mechanical, thermal and
chemical stimuli
- Mechanical nociceptors: selective responses to strong
pressure
- Thermal nociceptors: selective responses to burning heat or
extreme cold
- Chemical nociceptors: selective responses to histamine and
other chemicals
How is pain defined?
3 main types of pain:
1) Nociceptive pain: caused by stimulation or sensitization of peripheral
nociceptors. recognizable, well localized, extensive triggering of
nociceptors
2) Neuropathic pain: lesion of PNS
3) Psychogenic pain: pain that persist despite the lack of any identified
underlying physical cause
- Hyperalgesia:
Enhanced sensation of pain at normal threshold stimulation exaggerated
responses to stimuli. Occurs due to sensitization of nerves in and around the
damaged area
Sensitization= the nerves have a reduced threshold for firing as a results of
noxious stimuli
- Central sensitization leads to hyperexcitability of second-order
neurons within the dorsal horn of the spinal cord
Primary hyperalgesia: occurs within the area of damaged tissue, but
tissues surrounding a damaged area may become supersensitive as well by
the process of secondary hyperalgesia
, - Allodynia:
Here a stimulus not normally painful is perceived as painful
Dynamic (pain of object moving across your skin), tectal (touch or pressure)
and thermal (changes in temperature)
- Analgesia:
Loss of sensation of pain
Sensitization: response in which the pain pathways become more sensitive
2 types of sensitizations:
2. Peripheral sensitizations: occurs in response to the release of
inflammatory molecules such as histamine, prostaglandins these
substances sensitize nociceptors by creating an inflammatory soup that
enhances pain sensitivity by reducing the threshold of nociceptor
activation
3. Central sensitizations: here nociceptive-specific neurons
progressively increase their response to repeated non-painful stimuli,
develop spontaneous activity, and increase the area of the body that is
involved in pain.
What is the anatomy of the nociceptive system?
There are 4 major processes:
1. Transduction= the processes by which tissue-damaging stimuli
activate nerve endings
2. Transmission= the relay functions by which the message is carried
from the site of tissue injury to the brain regions underlying perception
3. Modulation= Neural process that acts specifically to reduce activity in
the transmission system
4. Perception= subjective awareness produced by sensory signals,
involves the integration of many sensory messages into a coherent and
meaningful whole
