Autonomic Nervous System and Neuroplasticity Flashcards
Which brain structures receive afferent info in the somatic and autonomic nervous systems?
thalamus: somatic (VPL, VPM)
hypothalamus: autonomic
What are the major sources of the descending pathways from the CNS to target tissues for the somatic and autonomic nervous systems?
cerebral cortex: somatic
hypothalamus: autonomic
How do efferent nerves synapse onto a visceral effector?
preganglionic neuron > autonomic ganglion > postganglionic neuron > visceral effector
Where are sympathetic and parasympathetic neurons located in the spinal cord?
sympathetic: T1-2 (lateral horn, thoracolumbar division)
parasympathetic: brainstem and S2-4 (craniososacral division)
What is the ratio of preganglionic to postganglionic fibers in the sympathetic division?
1:10 to 1:196
widespread effect
What is the ratio of preganglionic to postganglionic fibers in the parasympathetic division?
1:3 not as widespread
What is the overall function of the ANS?
regulate and control visceral activities that maintain a stable internal environment in response to changing internal conditions and external stresses
What is the role of the sympathetic system?
catabolic: prepares for fight or flight, breaking down molecules
What is the role of the parasympathetic system?
anabolic: conserves energy, rest and digest, maintenance and restoration of molecules
What is the sympathetic response in presence of a threat?
fight or flight
- dilated pupils
- rapid heart rate
- flushed skin
Which CNs are in the parasympathetic system?
III, VII, IX X
Where does the sympathetic system run through?
sympathetic chain
What are the characteristics of visceral afferent neurons?
- homeostasis and reflexes
- insensitive to mechanical and thermal stimuli
- poorly localized
- hunger, heartburn, nausea
- go through sympathetic chain to dorsal horn
What is the explanation for referred pain when related to visceral sensation?
- distensions and spasms of muscular walls of viscera or decreased blood flow to viscera can cause severe pain
- visceral and somatic afferents converge on common spinal cord neurons which causes referred pain
What are the common sights of referred pain?
pain from heart to the left chest and medial aspect of left arm
What is the sympathetic control on the heart?
increases heart rate and force of contraction
Where does sympathetic innervation of the heart come from?
upper thoracic segments
What is the autonomic system’s impact on the heart?
decrease HR and force of contraction
Where do the parasympathetic fibers that innervate the heart come from?
vagus nerve, CN X
What center does autonomic innervation come from to reach the heart?
descending cardioacceleratory tract: sympathetic
cardiac inhibitory center: parasympathetic
What is primary orthostatic hypotension?
blood pressure drops when person stands up
What is the cause of primary orthostatic hypotension?
degeneration of pre or postganglionic sympathetic fibers or thoracic cord
What is the sympathetic innervation of the bladder?
T11-L2 stimulation causes relaxation of detrusor muscle contraction of internal urethral sphincter which prevents bladder from emptying
What is the parasympathetic innervation of the bladder?
sacral spinal cord activation causes contraction of detrusor muscle and relaxation of internal urethral sphincter which causes the bladder to empty
What is bladder dysfunction caused by?
interruption of innveration causes neurogenic bladder
What is reflex neurogenic bladder?
bilateral spinal cord lesion above T12 resulting in UMN syndrome, spasticity, and sudden and reflexive emptying
What is non-reflex neurogenic bladder?
bilateral lesion of sacral spinal cord resulting in LMN paralysis, flaccidity, and bladder leakage
What is acute autonomic paralysis?
complete lesion of cervical spinal cord interrupts all suprasegmental control of sympathetic and parasympathetic divisions
What does acute autonomic paralysis cause?
spinal shock
- paralysis of bowel and bladder
- anhidrosis
- loss of piloerection and sexual function
- potentially severe hypotension
What is autonomic dysreflexia?
potentially life threatening condition associated with spinal cord lesions above T6
high BP, goose bumps, severe headaches, and sweating
What causes autonomic dysreflexia?
noxious stimuli below level of injury triggering sympathetic drive increase in blood pressure
disruption of descending parasympathetic fibers unable to modulate
How is autonomic dysreflexia treated?
immediately sitting person with AD upright
What is neural plasticity?
capacity for the brain to shaped by experience
What are the components of neural plasticity?
- synaptic plasticity (strength of synapse)
- synaptogensis (# of synapse)
- structural changes in the Brian that do not involve direct measurement of individual neurons (density of grey matter)
- functional reorganization (response to injury or practice)
What is synaptic plasticity?
- changes in strength of neural connections (synapses)
type and density
BDNF factor
What is synaptogenisis and synaptic pruning?
- increase and decrease in # of synapses
- dendritic arboization, spine density, synapse size and number, axonal arborization
What are some techniques to measure structural and functional changes to the brain?
- EEG
- PET
- MRI
- fMRI
- TMS
- MEPs
measures extracranially
What is EEG?
measurement of electrical activity of the brain
What is PET?
imaging to see when sections of the brain use glucose during a particular tasks to take note of functional areas and their size
What is fMRI?
measures changes in brain activity through MRI based on blood flow changes without the injection of a radioactive isotope
What is TMS?
strong and focused magnetic pulse used to record strength of connection between brain and muscle by stimulating brain and getting response of muscle
can be used to stimulate or inhibit
What are two conditions that can impair the development of ocular dominance columns?
congenital cataracts and strabismus
What is a classic plasticity example?
development of ocular dominant columns: develop to establish normal binocular vision and depth perception
What is the critical period for the development of ocular dominance columns?
time during which wiring of the visual cortex neurons remain malleable and thus vulnerable to effects of visual deprivation
What has animal experimentation told us about the critical period for development of ocular dominance columns?
sutured eye during critical period causes development of ocular dominance columns to never happen
What is language acquisition critical period?
- if child exposed to second language before 3, can become native speaker
- at time of puberty they will have more limited vocab and fluency
What is normal (adaptive) map plasticity?
- resolution of cordial maps is dependent on innervation densities (homunculus)
- maps differ in proportions but topographical sequence remains the same
What is an example of map plasticity among musicians?
long term intensive practice in keyboard players results in increases in gray matter and expansions of motor and sensory representations
What does map plasticity look like in response to injury?
animal experimentation: when digit is removed, cortical areas redistribute their association
What is a form of maladaptive plasticity?
fibromyalgia: condition that causes pain all over the body, sensitizes individual to pain responses
What is phantom limb pain?
a maladaptive plasticity following amputation where individuals feel vivid and painful sensations from missing limb due to cortical representations remaining in post central gyrus after amputation
What happens in phantom limb sensation/pain?
stimulation of shoulder or face may cause sensation of missing fingers due to reorganization
What is mirror box therapy?
people asked to imagine missing limb moving using a mirror and intact limb
What does cortical reorganization depend on in damage to the nervous system?
age, extent and location of injurym implementation in rehab
What is constraint induced movement therapy?
- constraint placed on unaffected arm after stroke, individual must use affected arm to get through ADLs
What are the 10 principles of experience dependent neural plasticity?
- use it or lose it
- use it and improve it
- specificity of training matters
- repetition matters
- intensity matters
- timing matters
- salience matters
- age matters
- transference
- interference
