Lecture 3 Flashcards
What can influence pain?
Experience
Define pain
Protective mechanism triggered by nociceptors
What are the 3 types of pain receptors? What does each detect?
1) Mechanical nociceptors: cutting, crushing, pinching
2) Thermal nociceptors:
temperature, especially heat
3) Polymodal nociceptors:
Various stimuli, including chemicals from injured tissues
1) What sensitizes all nociceptors?
2) What causes these to be released? What does this do?
3) What inhibits these?
1) Prostaglandins
2) Tissue damage releases prostaglandins which enhances pain by lowering activation threshold of those receptors (among other causes)
3) NSAIDs inhibit prostaglandins
What are the two ways nociceptors transmit info to the CNS? Briefly describe each
1) A-delta fibers: fast pain pathway
2) C fibers: slow pain pathway
What fibers are the fast pain pathway?
A-delta fibers
1) What are A-delta fibers?
2) How fast are they? Are they myelinated or unmyelinated?
3) What receptors use these?
1) Fast pain fibers
2) 30m/s (myelinated)
3) Mechanical and thermal pain receptors
1) What are C fibers?
2) How fast are they? Are they myelinated or unmyelinated?
3) What do they involve?
1) Slow pain pathway
2) 12m/s (unmyelinated)
3) Bradykinin
1) What is bradykinin?
2) What does it do?
1) A normally inactive substance activated in the ECF by tissue damage
2) Causes pain, contributes to inflammatory response
What are the two best known neurotransmitters for pain?
1) Substance P
2) Glutamate
1) Is substance P unique?
2) What does it do?
1) Yes; unique to pain fibers
2) Activates ascending pathways to transmit pain signals for processing
What two things does glutamate bind to? Why?
1) Binds with AMPA receptors: to ultimately transmit pain signals
2) Binds with NMDA receptors: to sensitize injured area
Can chronic pain occur without tissue damage?
Yes
1) What causes chronic pain?
2) How does this happen?
1) Abnormal signaling of pain pathways
2) Neuronal response to pain becomes exaggerated and can lead to sensitive neurons even after tissue has healed
Define referred pain
Sensation of pain in a part of the body that is remote from the damaged tissue
Where is referred pain often seen? Why?
With visceral pain; bc chest and abdominal organs often have no sensory receptors except pain receptors
1) Define analgesic system; what 3 things does it descend from?
2) What does it do?
1) The descending pathway from periaqueductal gray matter, medulla, and reticular formation
2) Release enkphalin
What is enkphalin and what does it do?
An endogenous opioid that binds with opiate receptors, inhibiting substance P
What is periaqueductal gray matter?
Gray matter surrounding the cerebral aqueduct
Why is a conscious response to pain necessary?
So an organism can remove a noxious stimulus or remove itself from the environment to avoid further tissue damage
Give an example of subconscious pain response
Sitting for prolonged periods can cause tissue damage from lack of blood flow where the skin is compressed by the weight of the body (shifting weight)
What are the two divisions of the ANS? Describe each and where their fibers emerge
1) Sympathetic
-Responding to stress; fight or flight
-Fibers emerge from thoracic and lumbar regions of the spine
2) Parasympathetic
-Relaxed activities; rest and digest
-Fibers emerge from cranial and sacral regions
True or false: parasympathetic and sympathetic typically innervate same effector organs
True
What does the ANS consist of?
A two-neuron efferent pathway
1) Where is the first ANS neuron cell body? What does its axon do?
2) What does the second ANS neuron do?
1) In CNS; preganglionic fiber synapses with cell body of the second neuron
2) Innervates the effector organ
What is another name for presynaptic and postsynaptic neurons?
1st and 2nd neurons
1) What regions are the parasympathetic presynaptic (preganglionic) neurons and ganglia in?
2) What regions are the sympathetic presynaptic (preganglionic) neurons and ganglia in?
1) Parasympathetic: Brainstem and sacrum
2) Sympathetic: Thoracic and lumbar
What do the preganglionic/ presynaptic endings of sympathetic fibers release? What about parasympathetic?
Preganglionic of both sympathetic and parasympathetic release Ach
What do the postganglionic/ postsynaptic endings of sympathetic fibers release? What about parasympathetic?
1) Parasympathetic: ACh
2) Sympathetic: NE
What two things mediate most effector organ responses?
Acetylcholine (ACh) and norepinephrine (NE)
What two types of structures release ACh? (nerves that supply what?)
1) Nerves that supply muscle and exocrine glands
2) Terminals of all motor neurons supplying skeletal muscle
What do the nerves that release norepinephrine (NE) affect?
Nerves supply smooth muscle, cardiac muscle, exocrine glands, CNS pathways for memory, mood, emotion, behavior, perception,sleep
1) What are fibers that release ACh called?
2) What does this include?
1) Cholinergic fibers
2) All autonomic preganglionic fibers and parasympathetic postganglionic fibers
1) What are fibers that release NE called?
2) What does this include?
1) Adrenergic fibers (NE aka noradrenaline)
2) Most sympathetic postganglionic fibers
What are the two exceptions to the general rules about what fibers release ACh and which release NE?
1) Sympathetic postganglionic fibers of sweat glands release ACh
2) Some autonomic fibers do not release either NE or Ach
Give two examples of dual innervation
1) When autonomic efferent output regulates visceral activities (E.g. circulation, digestion)
2) Most organs have sympathetic and parasympathetic fibers
True or false: Most organs have sympathetic and parasympathetic fibers
True
What two things does dual innervation do?
1) Allows for “opposite” effects in a particular organ
2) Enhances CNS control
Which fibers are the accelerators of the CNS? Which are the brakes?
1) Sympathetic: accelerators
2) Parasympathetic: brakes
1) When the heart is sympathetically stimulated, what happens?
2) What about when it’s parasympathetically stimulated?
1) S: Increases heart rate and increases force of contractions (entire heart)
2) P: Decreases heart rate and decreases force of contraction (atria only)
1) When most blood vessels are sympathetically stimulated, what happens?
2) What about when they’re parasympathetically stimulated?
1) S: Constricts(to increase BP)
2) P: Dilates vessels supplying the penis and clitoris only
1) When the lungs are sympathetically stimulated, what happens?
2) What about when they’re parasympathetically stimulated?
1) S: Dilates the bronchioles (airways)and inhibits mucous secretion (α)
2) P: Constricts the bronchioles and Stimulates mucus secretion
What 3 things does sympathetic stimulation do to the digestive system?
1) Decreases motility
2) Contracts sphincters (to prevent forward movement of contents)
3) Inhibits digestive secretions
What 3 things does parasympathetic stimulation do to the digestive system?
1) Increases motility
2) Relaxes sphincters (to permit forward movement of contents)
3) Stimulates digestive secretions
1) When the urinary bladder is sympathetically stimulated, what happens?
2) What about when it’s parasympathetically stimulated?
1) S: Relaxes
2) P: Contracts (emptying)
1) When the eyes are sympathetically stimulated, what happens?
2) What about when they’re parasympathetically stimulated?
1) S: Dilates the pupil (contracts radial muscle) for far vision
2) P: Constricts the pupil (contracts circular muscle) for near vision
1) When the liver is sympathetically stimulated, what happens to its glycogen stores?
2) What about when it’s parasympathetically stimulated?
1) S: Glycogenolysis (glucose is released)
2) P: Nothing
1) When the adipose cells are sympathetically stimulated, what happens?
2) What about when it’s parasympathetically stimulated?
1) S: Lipolysis (fatty acids are released
2) P: Nothing
1) When the pancreas is sympathetically stimulated, what happens to its exocrine secretions?
2) What about when it’s parasympathetically stimulated?
1) S: Inhibits pancreatic exocrine secretion
2) P: Stimulates pancreatic exocrine secretion (important for digestion)
1) When the sweat glands are sympathetically stimulated, what happens?
2) What about when they’re parasympathetically stimulated?
1) S: Stimulates secretion by sweat glands
2) P: Nothing
1) When the salivary glands are sympathetically stimulated, what happens?
2) What about when they’re parasympathetically stimulated?
1) S: Stimulates a small volume of thick saliva rich in mucus
2) P: Stimulates a large volume of watery saliva rich in enzymes
1) When the adrenal medulla is sympathetically stimulated, what happens?
2) What about when it’s parasympathetically stimulated?
1) S: Stimulates epinephrine and norepinephrine secretion (cholinergic)
2) P: Nothing
1) When the pancreas is sympathetically stimulated, what happens to its endocrine functions?
2) What about when it’s parasympathetically stimulated?
1) S: Inhibits insulin secretion; stimulates glucagon secretion
2) P: Stimulates insulin and glucagon secretion
1) When the genitals are sympathetically stimulated, what happens?
2) What about when they’re parasympathetically stimulated?
1) S: Controls orgasmic contractions (both sexes)
2) P: Controls erection (penis in males and clitoris in females)