Viscerosomatic & Chapman Take 2 Flashcards
Myotatic reflex
tonic contraction of muscle in response to stretching force, due to stimulation of muscle receptors
agonist is contracted while antagonist muscle is relaxed
What is a reflex?
relationship between an input stimulus to the body & output action to muscle or secretory organ
What is important about spinal cord gray matter?
processing area of cord
What is located in the lower layers of spinal cord gray matter?
interneurons
motorneuron cell bodies
Where do afferent fibers into spinal cord terminate?
end in layers 1 & 5
What input do interneurons receive?
70-80% of interneurons receive input from both visceral & somatic afferents
may account for visceral pain being so diffuse & poorly localized
What is responsible for localized pain pattern we see?
interaction of interneurons w/ somatic efferents
What is significant about the overlap of visceral & somatic afferent fibers?
basis for activation of somatic muscle activity seen w/ visceral disturbances
visceral afferents activate sympathetic outflows & skeletal muscle motor neurons
How do descending influences impact reflexes?
affect long-lasting excitability of outflows by maintaining reflex (sensitization of interneurons acts as amplifier of input so more output expected)
What is the basis for decompensation of homeostasis?
visceral disturbances reflexively cause activation in somatic musculature & produces dysfunction (facilitated segment)
somatic disturbances can reflexively alter visceral function
What is the somatic component of disease?
MSK palpatory findings may correlate w/ visceral disturbances
normalizing MS component may normalize autonomic outflows (leading to restoration of homeostasis)
What is habituation?
process of decreasing response of a neural pathway w/ a continuous stimulation
What is sensitization?
when a stimulus is repeated, response may grow for longer
a stable response level is reached that can continue @ increased level as long as stimulus is continued
How do habituation & sensitization contribute to homeostasis?
habituation & sensitization processes exist together to help maintain a homeostasis between over-reaction & under-reaction to a stimulus
What is the concept of facilitation?
maintenance of a pool of neurons in a state of subthreshold excitation
less afferent stimulation is needed to trigger discharge of impulses
Nociception theory
a stimulus activates nociceptive pathways that travel to spinal cord & branch to many sites
results in release of peptides @ motorneuron level in peripheral tissues
peptides lead to inflammatory cascade & initiate release of “chemical soup” that spreads in tissues
What is the main result of chemical soup in peripheral tissues?
lowers nociceptor threshold which INCREASES input to spinal cord
Where are nociceptors NOT found?
in brain or hyaline cartilage
What is the result of inflammation in tissues?
disrupts balance between habituation & sensitization
larger than normal motor outputs to autonomics & somatic systems
Steps for increasing sensitivity of neurons
short term excitability (sensitization) long term sensitization (lasting for hours) fixation (lasts for days-weeks) permanent excitability (w/ death of inhibitory interneurons)
Who was the main person behind the facilitated segment concept?
Denslow showed reflex changes (long lasting, low threshold areas to afferent inputs)
correlated excitable areas w/ injury & disease
Facilitated segment concept
includes skeletal muscle & sympathetic nervous system
What is allostasis?
the long term neural effect of segmental facilitation
What is the process that leads to allostasis?
stimulus (insult) is applied to tissues develop chemical soup of inflammation causes primary afferent sensitization results in hyperalgesia secondary hyperalgesia develops
