Pain and Analgesia Flashcards
What is the physiological definition of pain?
Fast and first pain; to alert one to relieve from the stimulus
-algia =
Pain
-algesia =
sensitivity to pain
nocere =
to injure
Nociceptors =
These are pain receptors; specifically sensitive to chemicals that cause or alert pain
Osmoreceptor=
Receptor sensitive to water
What is the function of the skin?
To protect, to feel- the skin is responsible for sensation.
What can we call sensations that we can feel on our skin?
Somatic sensations
What do we call sensations we feel inside our bodies?
Visceral sensations
What receptor does Acetlycholine fit into?
Muscarinic receptor
Describe reflexes?
Reflexes start when a stimulus hits into an receptor, and the sensory neuron (afferent) goes to the spinal integration center, and the motor neuron (efferent) to the effector to start the reflex to move away from the sense of pain
Afferent =
Travelling to somewhere (arriving)
Efferent =
Traveling outwards or away from something
The only way that the brain will know when you have had a reflex action is when…
The afferent neuron arrives into the spinal integration; and the sensory neuron also goes to the CNS, as well as activating the motor neuron to do something.
What does the sensory pathway consist of?
Three neurons and two synpases
What are the three neurons?
PERIPHERAL- to-SPINAL to- THALAMUS (then to-Brain)
Describe the sensory pathway?
The peripheral neuron arrives into the spinal cord, activating the spinal cord neuron (which contains the pain pathway crossover, to send appropriate message to the appropriate side of the brain) which then travels to the thalamus which then goes to CNS to interpret the pain.
Where is the pain pathway?
The spinothalamic tract (from the spine to the thalamus)
Why is pain a sign?
Because we can see the behaviour that goes along with the pain, and it can be measured on the pain scale (objective)
Pain is also a symptom because =
It is a subjective interpretation from the particular person
What is the physiological function of pain?
The process of the pain moving along the sensory pathway
What is the affective component of pain?
The motivational aspect of pain
What is the sensory component of pain?
The discriminative aspect of pain
What are the four components of physiology of pain?
- Transduction
- Transmission
- Perception
- Modulation
What is transduction?
- conversion of stimulus into action potential (chemicals + receptors) (Changing one energy to another.
What is transmission?
- pain transmission (sensory pathway, impulse conduction) (Sending impulse up to the brain)
What is perception?
interpretation (sensation, appreciation, conscious experience). (NOW WE KNOW THAT WE HAVE GOT PAIN).
What is modulation?
modification- how are we going to stop the pain
(suppression, inhibition of impulse)
Describe pain at the tissue level:
The free nerve endings start a reaction in the nociceptors. The Chemicals stimulate nociceptors = local depolarisation = transduction (change chemical energy to electrical energy)
Name two of the pain mediators that are released by damaged cells
- Histamines and prostaglandins
What do prostaglandins do?
They stimulate the nociceptors and we feel pain. (This is transduction; chemical into electrical)
How do the damaged cell release prostaglandins
Phospholipids (cell membrane) – release arachidonic acid – metabolised by COX (cyclooxygenase) into prostaglandins and later into leukotrienes
PG =
Prostaglandins
If we give a medication that stops the COX enzyme what happens?
It blocks the COX enzyme, stopping the creation of prostaglandins = no pain.
A lot of NSAID do what?
Block the COX enzymes, blocking pain. [COX inhibitors]
If the cause of the pain is inflammatory, what kind of medication would you give?
An anti-infammatory drug.
Paracetamol does what?
Anti-pyrogenic and analgesic.
Describe the nociceptive neuron C fibre:
90% of pain fibers, polymodal receptors (more general), unmyelinated, small, slow (0.5–2µm, 0.5-1m/sec), poorly localised, dull ache, visceral pain, paleospinothalamic tract
Describe the nociceptive neuron A-delta:
10%, mechanoreceptors, myelinated, sharp pain, high threshold, large, fast (2-5µm, 4-30m/sec), well localized, part of reflex, neospinothalamic tract
What does pain innervation mean?
the distribution or supply of nerves to a part
What is substance P and where is it released:
It is a neurotransmitter released at synapse from 1st neuron to the 2nd neuron in the sensory pathway
What is the pain innervation of the parasympathetic system?
Parasympathetic – oesophagus, trachea, rectum, urethra, vagina, prostate
What is the pain innervation of the sympathetic system?
Sympathetic – lungs, stomach, intestines, bladder, uterus
What does decussation mean?
‘Crossing Over’
If you hurt your left side, and have had a CVA in the right side of your brain, will you be able to localise and feel that pain?
No
Modulation =
Altering or reducing pain perception
This is done by endogenous endorphins; using our body’s natural pain relief
What is the gate theory?
Massaging the area through modulation actually changes the pathway and stimulates the C-fibres, which are slow neurons which help dull the ache
How does modulation work?
It releases endorphines that go to the fist neuron that has received the pain chemicals; and tells the neuron to stop producing substance P.
Mu-1 receptors are specifically for what?
Pain
What kind of substance is morphine?
An opioid; our body has natural opioids that help to modulate our pain.
What is neurogenic pain?
or neuropathic pain – damage to nerve (severe, long lasting, difficult to treat)
What is nociceptive pain?
somatic, deep or superficial (trauma, short, easy to treat) or visceral (severe, longer, more treatment)
What is psychogenic pain?
real pain, no cause, difficult to treat
What is the pain threshold?
the point at which the sensation of pain is initiated by tissue damage does not vary much between people, physiological
What is pain tolerance?
the point at which pain becomes unbearable – varies widely among individuals and also in a single individual under different circumstances, psychological
ethnicity, genetics, gender, culture
Referred pain =
pain felt in a part of the body other than its actual source.
What is normal sensory threshold for sensory stimulus?
-30mV
What is the normal pain threshold?
Above normal sensory level
Physiologically we all have the:
Same pain threshold- we all need the same amount of pain to FEEL IT. We just PERCEIVE and TOLERATE it differently.
There is no adaptation in what receptors?
Nociceptors [they continue to physiologically feel the same pain as they always have]
If you give too much morphine what should you give and why?
Naloxone because it is an antagonist (blocks opioid receptors)
What is an adujvent?
a substance which enhances the body’s immune response to an antigen.
What are examples of analgesia (prevents pain receptors from receiving signals)
- anti-prostaglandins
- anti-histamines
- COX-inhibitors
- local anaesthetic
- hot or cold agents
What are examples of Non-narcotic analgesics ?
NSAID eg diclofenac, ibuprofen
Aspirin
Paracetamol
What are examples of Narcotic analgesics?
Agonists - morphine, pethidine, tramadol, codeine, oxycodone, methadone
Partial agonists – buprenorphine (slow, not so good)
Antagonist – naloxone (blocks opioid receptors)
What is an antagonist?
substance which interferes with or inhibits the physiological action of another.
What is a nerve block?
Injects local anaesthetic into nerve to stop impulse registering pain
What are the narcotic effects on the peripheral system?
decreased gut motility, spasms of sphincters, suppresses spinal reflexes, bronchoconstriction, itchin
What are the narcotic effects on the central system?
analgesia, suppress cough reflex and respiratory centre, sedation, sleep, euphoria, dysphoria, nausea + vomiting, prolonged labour, hypotension, tolerance + dependence
What is the difference between opiate and opioid?
Opiate – from plant eg morphine
Opioid – synthetic eg pethidine
Name two types of drugs that alters patients interpretation:
narcotics and antidepressants
Name two types of drugs that decreases patients perception:
anxiolytics and hypnosis