Pain 3 Flashcards Preview

Excitatory - Injury to the muscle leads to increased muscle spasm in the area of injury - because of an increase in metabolites = increase pain pain results in an increased activity which in return will lead to an accumulation of metabolites and consequently further increase pain. the muscles in the surrounding structures would decrease motion to prevent injury

- nociceptive afferent information is travelling via the spinal cord to both higher nervous centres for pain perception and to alpha motor neurons on segmental level causing an increase in muscle activation - nociceptive information travels to gamma motoneurons, affecting increased muscle spindle output and thereby resulting in hyperexcitability of the alpha motoneuron

Inhibitory - Increase activity in antagonist mm. to inhibit movement of injured muscle = reduce pain the pain will decrease activity in muscles acting as an agonist and increase activity in muscles acting as an antagonist, thereby being adaptive to the function of each m

nociceptive information transferred either via inhibitory or excitatory interneurons to the alpha motoneuron p

- change in mechanical behaviour - redistribution of mm. load (1) aims to protect from further pain or injury, (2) involves redistributions of activity within and between muscles (3) leads to changes in mechanical behaviour (4) involves changes at multiple levels of the motor system, which may be complementary, additive or competitive, (5) with short-term benefits, but potential long-term consequence

-Cells in substancia gelatinosa act as a gate for pain. It control impulses via A-delta and C fibres coming into the brain by closing the gate, which in turn blocks the signals and decreases pain. According to this theory, nociceptive impulses are transmitted to the spinal cord through large A- delta and small C- fibre types These fibres create synapses with neurons in the SG The cells in this structure function as a gate, regulating transmission of impulses to CNS Stimulation of larger nerve fibres (A-alpha, A-beta) causes the cells in substantia gelatinosa to "close the gate„ for transport of painful information centrally. AclosedgateleadstodecreasesstimulationofT-cells(the 2nd afferent neuron), which decreases transmission of impulses, and diminishes pain perception

PAG, the rostral ventromedial medulla (RVM), and the pontine tegmentum

Amygdala which projects to prefrontal cortex

escape and avoidance of noxious stimuli.

OFF cells are thought to be involved in descending inhibition, whereas ON cells are thought to be involved in descending facilitation of nociceptive information

1. Suboptimal movement/motor control as a precursor to injury and pain

2. Impaired movement/motor control as a consequence of interference by actual or threatened injury and/or pain

3. Modification of movement/motor control for protection of the painful/injured/threatened region

4. Modified movement/motor control explained by a conditioned association with pain

 changes motor function, such as subtle redistribution of activity within or between muscles, to complete avoidance of movement, activity, or participation

Association of pain with movement

change behaviour to the new unconditioned stimulus of protective behaviour 

neuropathic pain is a direct consequence of a lesion or disease affecting the peripheral somatosensory system.

Central neuropathic pain is a direct consequence of a lesion or disease affecting the central somatosensory system

A disorder of a single nerve or nerve trunk.