Exteroception and Nociception Flashcards
List the Special Senses
- visual (photons)
- auditory (pressure)
- chemical (olfaction, taste)
Visual System Signal Type
2nd messenger
Auditory System Signal Type
direct
Olfaction System Signal Type
2nd messenger
Taste System Signal Type
2nd messenger
Touch System Signal Type
direcy
Definition of Signal Transduction
-stimulus dependent to voltage dependent signaling
Proprioception
-sense of position of one’s own body
Steps of Transduction on Visual System
- light stimulation of rods leads to activation of G protein, transducin
- activated G protein activates cGMP phosphodiesterase (PDE)
- PDE hydrolyzes cGMP, reducing concentration
- this leads to closure of Na channels
Addition of light has what effect on proteins on photoreceptor disks?
- light causes photo receptor proteins to shift from cis to trans
- this leads to hyperpolarization
What types of nerve fibers are served by Aa?
- Ia= muscle spindle afferent
- Ib= tendon organ afferent
- touch, proprioception
What types of nerve fibers are Ab?
-II- mechanoreceptors of skin, secondary muscle spindle afferents
What types of nerve fibers are Ad?
- III= sharp pain, cold temp
- mechanical pain
- extreme heat pain
- first pain
What types of nerve fibers are C?
IV= warm temp, burning pain, itch, crude touch, capsaicin
- polymodal pain
- extreme cold pain
- second pain
- a low dose of LA can block second pain and leave first pain intact
Meissner’s Corpuscles
- small receptive field
- fast adaptation (detect vibration)
Pacinian Corpuscles
- large receptive field
- fast adaptation (detect vibration)
Merkel’s Disks
- small receptive field
- slow adaptation (detect steady touch)
Ruffini’s Ending
- large receptive field
- slow adaptation (detect steady touch)
3 Types of Pain
- nociceptive (external)
- inflammatory
- neuropathic
Spinoreticular Tract
- to hypothalamus, amygladal
- responsible for behavioral response to input
Spinomesencephalic Tract
- to midbrain
- important for descending modulation of pain
Anterolateral System: Sensations
- temp
- pain
Anterolateral System: Primary Sensory Neuron
- DRG
- Ad
- C
Anterolateral System: 1st Synapse
-dorsal spinal cord
Anterolateral System: Decussation
-spinal cord
Anterolateral System: Input vs Ascending Info
-contralateral side
Dorsal Column Medial Lemniscus (DCML) System: Sensations
- proprioception
- find touch
Dorsal Column Medial Lemniscus (DCML) System: Primary Sensory Neuron
- DRG
- Ab
Dorsal Column Medial Lemniscus (DCML) System: 1st Synapse
- nucleus gracilis (medulla)
- nucleus cuneatus (medulla)
Dorsal Column Medial Lemniscus (DCML) System: Decussation
-medulla
Dorsal Column Medial Lemniscus (DCML) System: Input vs. Ascending Info
-ipsilateral then contralateral
Thermoneutral Point
- 30-37 deg C
- sense neither hot nor cold
Cool Receptors
- dec. temp -> inc. firing rate
- mostly Ad
- 10x as many cool receptors as warm receptors
Warm Receptors
- inc. temp -> inc. firing rate
- mostly C receptors
Nociceptive
-detection of acute painful stimuli
Molecular Pain Receptor Types
- ASIC
- P2X
- VR1
ASIC Molecular Receptor
- acid sensing ion channel
- pH becomes acidic in inury
P2X Molecular Receptor
- purinergic receptor
- detects ATP released from cell damage
VR1 Molecular Receptor
- vanilloid receptor 1
- detects capsacin
- polymodal- responds to chemicals and temp
3 Components of Triple Response
- red center- due to BK
- wheal- due to BK
- pink flair- due to substance P
Bradykinin (BK)
- precursor is kininogen
- cell damage allows cleavage of kininogen to BK
- potent vasodilator (red center)
- inc capillary permeability (edematous wheal)
Substance P
- peptide
- in vesicles
- released upon stimulation (requires repetitive, intense stimulation to be released)
- sensitizer (inc. sensitivity to pain)
Hyperalgesia
-inc. sensitivity to pain
Allodynia
- normal stimulus becomes painful
- ex. sunburn
How does aspirin resolve a headache?
It prevents synthesis of bradykinins.
Order of Pressure Block
- first Ab
- then Ad
- then C
Local Anesthetic Block
- first C
- then Ad
- then Ab
- target voltage gated Na channels
Order of Activated Electrical Stimulation
- first Ab
- then Ad
- then C w/ repetitive stimulation
Concept of Referred Pain
- pain is perceived as localized to area of predominant input
- cutaneous areas dominate
Inhibitory Neurons
- inhibit pain synapse in substantia gelatinosa
- enkephalinergic
- why we rub pain
Peri Aquaductal Grey
- has descending influences on pain pathway
- descends to nucleus raphe magnus (medulla)
- located in midbrain
- nucleus raphe descends to dorsal horn (DLF pathway)
- this causes release of serotonin and activation of enkephalic interneuron
- SSRIs inc. 5Ht and reduce pain
Stress Induced Analgesia
- painless experience due to high stress
- due to PAG
- stress/emotions activate PAG (limbic system involved)
- naloxone partially blocks this
Cannabinoids
- 2 major presynaptic receptors: CB1, CB2
- reduce inflammation and dec. pain
Na Channels Involved in Neuropathic Pain
- TTX-S (sensitive)
- TTX-R (resistant)
- mutations in these cause dec. pain sensation
GABA
- major inhibitory neurotransmitter
- gabaergic neurons help determine what happens at a synapse
- GABA dec. with damage
BDNF
- neurotropin
- ATP -> activation of immune cells -> BDNF
- BDNF active on GABA responsive neurons and changes ECl, causing GABA to become excitatory
- BDNF also inhibits KCC2, which causes GABA to become excitatory
Modality Segregation
-when neurons die, amount/type of neurotropins changes -> nerve wiring changes
Targets for Drugs in Pain Pathway
- VCR1, ASIC, P2X
- substance P
- Na Channel
- enkephalin
- 5HT
- GABA
- Ca Channels
- glutimate
- AMPAr.
- NMDAr.
- NK1r
