Pain Flashcards
What is the definition of pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such tissue damage
What is acute pain
- normal pain
- Afferents A delta and C fibres involved
- serves as a protective function
First pain - stabbing A delta fibres
Second pain - dull, aching C fibres
Where is pain first detected
In the free nerve endings in the skin, dentin ect
What are A delta fibres associated with
Noxious mechanical/heat
What are C fibres usually associated with
Polymodal (involving more than one sense)
Describe the somatic nociception pathway
Neuron 1 - peripheral sensory receptor, synapses upon entering the spinal cord
Neuron 2 - bypasses the brainstem goes to thalamus where it synapses with neuron 3
Neuron 3 - goes to the cortex produces response
What is important about the spinothalamic tract pathway
Enables one to move away from pain stimuli fast
Important for survival
What is the spinal lemniscus
In the medulla the two tracts merge within the spinotectal pathway and the combined tract is known as the spinal lemniscus
What is the corticospinal tract
Carries information from the motor cortex to the spinal cord
What are the large fibrous bundles that ended the midbrain when the neuron leaves the motor cortex called
Cerebral peduncles
What is the difference between the corticotubular tract and the corticospinal tract
The corticospinal tract synapses with the lower motor neurons innervating the muscles in the limbs and the trunk
The corticotubular tract synapses at the cranial nerves to control muscular movements of the head, neck and face
Describe the lateral corticospinal tract
The lateral corticospinal tract contains over 90% of the fibres present in the corticospinal tract and runs the length of the spinal cord
What is the primary responsibility of the lateral corticospinal tract
Control the voluntary movement of the contra lateral limbs
Describe the anterior corticospinal tract
Small bundle of decending fibres that connect the cerebral cortex to the spinal cord
What is the difference in the lateral and anterior corticospinal tract
Anterior - fibres enter the medulla on the same side of the body they entered in
Lateral - fibres enter the medulla on the opposite side of the body
Where are free nerve endings found in the teeth
Free nerve endings are found in the dentine
Free nerve endings send axons via the trigeminal nerve through the anterior (ventral) trigeminothalmic pathway
What are the receptors of pain pathways
Nociceptors (free nerve endings)
What axon classes are involved in pain pathways
A delta and C fibres
What CNS pathways are involved in pain
- spinothalamic
- anterior (ventral)
- trigeminothalmic
What areas of the forebrain is involved in pain pathways
Primary sensory cortex
Subcortical areas
What details would you have to gather about a patients pain
- location
- quality
- intensity
- frequency/duration
- provoking/relieving agents
In dentistry you should locate which branch of the trigeminal nerve the pain is on
Name and describe the three branches of the trigeminal nerve
Opthalmic - The ophthalmic nerve branches from the trigeminal nerve in the skull and begins in the lateral wall of the cavernous sinus, a cavity between the bones in the front and middle of the skull SENSORY
Maxillary - The maxillary division of the trigeminal nerve is a sensory nerve. It leaves the skull via the foramen rotundum and enters the upper part of the pterygopalatine fossa SENSORY
Mandibular - When the mandibular nerve emerges from the foramen ovale, it is located between the tensor veli palatini muscle medially, and the lateral pterygoid muscle laterally. The otic ganglion is located on its medial surface. SENSORY AND MOTOR
What is referred pain
Pain tends to differ from internal organ to superficial area on the skin
What factors can affect pain perception
- genetic
- molecular
- cellular
- anatomical
- physiological
- social
What is the SC9A gene
Encodes x subunit of voltage gated Na+ channel nav 1.7
What is nav 1.7
Nav1.7 is a voltage-gated sodium channel and plays a critical role in the generation and conduction of action potentials
Strongly expressed in nociceptive afferents (receptor endings)
Describe why some individuals can’t feel pain
If there is a SCN9A mutation there is a loss of the NAv 1.7 function
Rubbing the area of pain applies what theory
The gate control theory
Describe the gate control theory in a situation where an individual has hit their knee
Rubbing the knee is a touch signal which starts at the same location as the pain
This stimulates mechanoreceptors
When the 1st neuron of the mechanoreceptor is in the dorsal grey horn it will branch, this small branch will synapse with another neuron that sits in between neuron 1 and 2 of the pain pathway
This is called the inhibitory inter neuron, activation of this will essentially stop the pain signal
What is the internal capsule
Allows communication between areas of the cerebral cortex and areas of the brainstem
What are the reactions to tissue damage
- wheal can form
- dermatographia
What does the CGRP cause in tissue damage
The dilation of blood vessels
Cause the red reaction=flare
What causes the wheal to form in tissue damage
Release of bradykinin
