Special Topics in Oral Biology - Exam 2

Pain is the body's

alarm system

Pain is classified by

-time (acute, subacute, chronic)

-etiology (malignant or non-malignant)

-mechanism (nociceptive or neuropathic)

-quality (fast (A-delta) or slow (C))

fast pain (A-delta) is

sharp, stabbing

Slow pain (C) is

aching, throbbing

pain can be broken up into

nociceptive or non-nociceptive

nociceptive can be broken into

somatic (surface, A-delta fast pain)

Visceral (deep tissue/organ, C slow pain)

non-nociceptive pain is

neuropathic

pain is generally a

protective, beneficial mechanism

pain is invoked by ____; alerts the individual to remove themselves from situation causing stimuli and damage

tissue damage

there are two types of pain with distinct sensations and distinct pain transmission pathways

Fast pain (via A-delta nerve fibers)

Slow pain (via C nerve fibers)

Describe fast pain

- rapid onset, within 0.1 second of stimulus

- intense; describes as sharp, stabbing, electric

- very well localized

- usually not felt in most deep tissues or viscera

describe slow pain

- beings 1 second or more after stimulus; builds

-burning, aching, throbbing or nauseous pain

- poorly localized, often diffuse pain

- usually associated with deep tissues and viscera

- tissue destruction and unbearable suffering

A-alpha fibers send impulses at a speed of

120 (100) m/sec

A-delta fibers send impulses at a speed of

10 m/sec

C fibers send impulses at a speed of

1 m/sec

slow pain can _______

wake you up

fast pain is conducted through the ___________ tract of the anterolateral spinothalamic pathway

neospinothalamic

Fast pain is primarily a mechanical stimulus that is transmitted through fast _____ fibers

A-delta

In fast pain, synapse in the dorsal horn of spinal cord with fibers that crossover and ascend up the anterolateral spinothalamic pathway in the neospinothalamic tract innervate the reticular formation and _____; some projections continue to the ____

thalamus, somatosensory cortex

fast pain Is _____ and graded in intensity ____ the slow pain

localized, better

Slow pain is conducted through the _____ tract of the anterolateral spinothalamic pathway

paleospinothalamic

slow pain is primarily through slow

C nerve fibers

Slow pain synapses in the dorsal horn of spinal cord with interneurons where they synapse and crossover to travel up the anterolateral spinothalamic pathway in the paleospinothalamic tract to the reticular formation (the ____ and ______ center); only 10-20% go to the thalamus

wakefulness, arousal

slow pain has very ___ localization and ____ (no projections to the somatosensory cortex)

poor, grading

there are two types of main types of pain receptors (nociceptors), they are

- A-delta nerve fiber-associated pain receptors

- C nerve fiber-associated pain receptors

A-delta nerve fiber-associated pain receptors are _____

unimodal

what does unimodal mean

activated by noxious mechanical stimuli

C nerve fiber-associated pain receptors are ____

polymodal

what does polymodal mean

activated by various noxious stimuli

C nerve fiber-associated pain receptors can be activated by

mechanical, thermal, or chemical pain

pain receptor activation activates its ______ neuron

associated

pain receptors ___ __ adapt

do not

pain transmission pathways can become sensitized

true

what is hyperalgesia

increased perception of painful stimuli

what is allodynia

pain sensation from normally non painful stimuli

sensory receptor activation is

depolarization

sensory afferent nerve activation

first order neuron

activation of ascending neuron

second order neuron

nerve to contralateral somatosensory cortex and synapse

third order neuron

dentinal tubules are innervated by

A-delta nerve fibers

what is the pathway of dentinal sensitivity and pain

dentinal tubule, unimodal nociceptor, A-delta fibers, neospinothalamic tract of ALST pathway, CL reticular formation and thalamus, CL somatosensory cortex

describe dentinal sensitivity and pain

-mediated by A-delta neurons

-fast pain (sharp, stabbing, acute)

-very well localized (projects neurons to somatosensory cortex)

what is the pathway of pulpal sensitivity and pain

pulp, polymodal nociceptor, C fibers, paleospinothalamic tract of ALST pathway, CL reticular formation and thalamus

describe pulpal sensitivity and pain

- mediated by C neurons

- slow pain (dull, aching, throbbing)

- very poorly localized

- suffering and arousal

describe periodontal sensitivity and pain

- very similar to dentinal pathway

- mediated by A-delta neurons

- fast, sharp, well localized pain

what is the pathway of periodontal sensitivity and pain

periodontal ligament, unimodal nociceptor, A-delta fibers, neospinothalamic tract of ALST pathway, CL reticular formation and thalamus, CL somatosensory cortex

lidocaine is a mechanism of

action

lidocaine stabilizes the __ ___ by inhibiting ionic fluxes required for initiation and conduction of impulses, thereby effecting local anesthetic action

neuronal membrane

volatage gated sodium channels recharge the neural membrane to allow

propagation

lidocaine blocks voltage gated sodium channels and prevents

neural propagation

what is referred pain

pain that is perceived at a site that is remote from the noxious stimuli trigger-point (heterotopic pain)

the nervous system is organized into the

central and peripheral nervous system

what makes up the central nervous system

brain and spinal cord

what makes up the peripheral nervous system

afferent and efferent division

Sensory nerves are apart of the ___ division

afferent

motor nerves are apart of the __ division

efferent

information in the afferent division go from

periphery to CNS

information in the efferent division go from

CNS to periphery

what makes up the efferent division

somatic nervous system and autonomic nervous system

what makes up the autonomic nervous system

sympathetic and parasympathetic nervous system

what are the two types of membrane potentials

graded and action

gradients drive

physiological processes

what is a gradient

when a difference exists between two compartments with respect to the pressure, concentration or electrical potential of a given variable

what are the types of gradients

pressure, concentration, electrical, thermal

membrane potentials are _____ across a membrane

electrical differences

there are several types of membrane potentials including

1. resting potential

2. equilibrium potential

3. graded potential

4. action potential

5. excitatory post-synaptic potentials (EPSPs)

6. inhibitory post-synaptic potentials (IPSPs)

resting cells have membrane potentials with the interior of a resting cell being ___ relative to surrounding extracellular fluid

electronegative

extracellular fluid is considered to be electrically

neutral

the degree of electronegativity of membrane potentials is dictated by

cell type and cell size

the resting membrane potential of large motor nerves, skeletal muscle fibers and cardiac muscle is

-90 mV

the resting membrane potential of small nerves, CNS nerves and smooth muscle fibers is

-40 mV to -60 mV

the resting membrane potential of red blood cells is

-10mV to -20 mV

a membrane potential is an electrical gradient we can use to do

work

some cells can communicate with one another by rapidly changing their membrane potentials such as

nerves, muscles, and some glandular cells

nerves, muscles, and some glandular cells have ____ __ that can change membrane potential rapidly and propagate the change rapidly along the surface of the membrane (nerve impulse propagation, skeletal muscle depolarization)

excitable membranes

what determines resting membrane potentials

1. Na+ K+ ATPase exchange pump (-4mV)

2. "trapped" intracellular anions

3. ionic concentration gradients and selective permeability

what are examples of "trapped" intracellular anions

proteins and phosphates

during periods of maximum membrane permeability for K+, the membrane potential moves toward

K+'s equilibrium potential (-94 mV)

during periods of maximum membrane permeability for Na+, the membrane potential moves towards

Na+'s equilibrium potential (+61 mV)

the resting membrane potential is closer to __ equilibrium potential than the__ equilibrium potential

K+, Na+

dendrites and axons are ___ channels

ligand gated

graded potentials occur at the

dendrites and cell body

action potential occur at

axon hillock, axon, and axon terminals or synaptic bulbs

axon terminals or synaptic bulbs are ___ channels

voltage-gated Ca++

Axon hillock and axon are ___ channels

voltage gated Na+ and K+

depolarization tends to be

excitatory

depolarization goes in a __ direction

positive

repolarization goes in a __ direction

negative

hyperpolarization goes

below the resting membrane potential

hyperpolarization is very

inhibitory

different __ can produce either depolarizing or hyperpolarizing graded potentials

stimuli

amplitude of graded potentials are modulate by ___ and can be

stimulus strength, excitatory or inhibitory

graded potentials can be

summed additively or subtractively

action potentials are characterized by

a rapid and complete depolarization of the membrane

membrane repolarization rate and action potential duration are dependent on

cell type

what is the repolarization rate of neurons

1-2 msec

what is the repolarization rate of skeletal muscles

5-10 msec

what is the repolarization rate of cardiac ventricular muscle

200 msec

action potentials can only be generated in excitable membranes having regions of

voltage-gated (or sensitive) channels

a ligand binding to receptor and opening channel pores generates

graded potentials