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