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A patient and doctor discuss congenital insensitivity to pain. For people with this disorder, cognition and sensation are otherwise normal; for instance, patients can still feel discriminative touch (though not always temperature [3]), and there are generally no detectable physical abnormalities.
' pain receptor ') is a sensory neuron that responds to damaging or potentially damaging stimuli by sending "possible threat" signals [1] [2] [3] to the spinal cord and the brain. The brain creates the sensation of pain to direct attention to the body part, so the threat can be mitigated; this process is called nociception.
Salt and sour receptors are chemically gated ion channels, which depolarize the cell. Sweet, bitter, and umami receptors are called gustducins, specialized G protein coupled receptors. Both divisions of receptor cells release neurotransmitters to afferent fibers causing action potential firing. [8]
Alpha-2 receptors usually have inhibitory effects, but many are located pre-synaptically (i.e., on the surface of the cells that release norepinephrine), so the net effect of alpha-2 activation is often a decrease in the amount of norepinephrine released. [14] Alpha-1 receptors and all three types of beta receptors usually have excitatory effects.
Therefore, less pain is felt (via reduced transmission cell activity) when more activity in large-diameter fibers (touch-, pressure-, and vibration- transmitting) occurs relative to the activity in small-diameter (pain-transmitting) fibers. [citation needed] The peripheral nervous system has centers at which pain stimuli can be regulated.
Presynaptic inhibition is a phenomenon in which an inhibitory neuron provides synaptic input to the axon of another neuron (axo-axonal synapse) to make it less likely to fire an action potential. Presynaptic inhibition occurs when an inhibitory neurotransmitter, like GABA, acts on GABA receptors on the axon terminal.
Acute pain — sudden or urgent pain that results from injury, trauma or surgery — affects more than 80 million Americans annually and is the most common reason for emergency department visits ...
Agonist vs. antagonist. In pharmacology the term agonist-antagonist or mixed agonist/antagonist is used to refer to a drug which under some conditions behaves as an agonist (a substance that fully activates the receptor that it binds to) while under other conditions, behaves as an antagonist (a substance that binds to a receptor but does not activate and can block the activity of other agonists).