where are pain receptors found
Pain receptors or nociceptors consist of free nerve endings, found
throughout the body, with the exception of the brain.
what to pain receptors do
Nociceptors respond to any type of stimulus that is strong enough to cause tissue damage:
– intense mechanical or thermal stimulation
– chemicals characteristically released from damaged and inflamed tissues,
what are noicreceptors enhanced by
he responses of nociceptors to stimuli are enhanced by
prostaglandins,
– which are also always present at sites of tissue damage and inflammation.
– Aspirin, paracetamol and other non-steroidal anti-inflammatory drugs inhibit the
synthesis
pain pathway
First order sensory neuron
Synapse in grey matter with second order neuron
Ascends in white matter to the brain
Third order neurons go to: sensory cortex parietal lob, frontal lobe, reticular formation, limbic system, hypothalamus.
neurotransmitters in the synapses for pain
substance P and glutamate
two different types of nerve fibers
fast pain and slow pain
whats fast pain
- Related to painful stimuli of the skin, mouth and anus
- Goes to specific and limited areas of the cortex
- Precise localisation of pain
- Helps with quick reaction
- DOES NOT radiate
what is fast pain transmitted by
by thick, myelinated nerve fibres called A delta fibres
whats slow pain
dull and radiating can last for a longer time, ache
- Hold the affected body part immobile so that further injury does not occur
- Originates in internal organs
- Felt more diffusely
- Causes whole range of symptoms; irritability, difficulty sleeping and a depressed mood
whats slow pain transmitted by
- Very thin unmyelinated nerve fibres called C fibres
define refereed pain
pain goes to the surface of the body may not be related to where the pain is originating. Results from interconnecting sensory nerves.
whats the gate control theory
uggests that non-painful sensory input can prevent impulses that arise at nociceptors (pain receptors) from reaching the central nervous system
eg rub elbow when just hit it.
- mechanoreceptors, stimulated by rubbing, may block impulses from nociceptors in the elbow from reaching synapses in the central nervous system.
ascending and desceding pain control mechanism
n this adaptation to pain, areas in the midbrain transmit impulses down the spinal cord which can block the afferent flow of impulses from pain receptors.
Important in the operation of such descending pain control pathways are the natural opioids (endorphins and enkephalins), serotonin and noradrenalin.
what are glial cells
Glial cells support neurons metabolically and physically and have an immune function.
Glia recognize chemical signals from neurons,
release chemical signals that modulate communication between nerves.
- Modulate action of CNS neurons
what acute phase reaction
- systemic response to infection or injury
During the acute phase reaction, there is
– sleepiness,
– poor appetite,
– increased production and early release of neutrophils from bone marrow, and
– altered rates of hepatic synthesis of most of the major plasma proteins (e.g.
albumin goes down; complement proteins and “C-reactive protein” go up.)
systemic manifestations of inflamation
- cytokines are key factors in acute phase reaction
- sever infection or injury there are secreted in high concentration by macrophages in inflammation and immune response
- some cytokines also exert affects at beyond the site of inflammation on organs and produce body wide affects such as fever
define hypergalia
heightened sense of pain
opioid affects
CNS:
- Overdoes= suffocation
Never give newborns opioaides
