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Flashcards in Autonomic nervous system Deck (36):

What is the purpose of the autonomic nervous system?

Maintaining homeostasis and survival 


Which tissue types does the CNS innervate?

Everything except the CNS tissue and skeletal muscle


What are the three divisions of the ANS?

Sympathetic NS

Parasympathetic NS

Enteric NS


Describe the general pattern of innervation of the sympathetic and parasympathetic NS?

Most organs are innervated by both sympathetic and parasympathetic nerves, but each system usually innervates different tissues.


Which spinal cord segments are the sympathetic and parasympathetic nerves derived from?

Sympathetic: thoraco-lumbar

Parasympathetic: cranio-sacral

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Where in the spinal cord do autonomic pathways NOT originate from?

Cervical or lumbar enlargements


Why don't autonomic pathways originate from cervical or lumbar enlargements?

Upper and lower limb nerves originate from here


Describe the location of sympathetic and parasympathetic ganglia?

Sympathetic ganglia are more distant from organs

Parasympathetic ganglia are closer to or within organs

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What are the two divisions of sympathetic ganglia?

Prevertebral ganglia

Paravertebral ganglia

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Describe the general organisation of sympathetic and parasympathetic nerves (in terms of strucutre, ganglia, etc.)?

Sympathetic: short preganglionic, long postganglionic fibres

Parasympathetic: long preganglionic, short postganglionic fibres

Preganglioinc fibres are lightly myelinated or unmyelinated, whereas all postganglionic fibres are unmyelinated 

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Which NTs are used by sympathetic and parasympathetic nerves?

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What are non-classical transmitters?

Give some examples?

NTs that are not Ach or NA

aka 'non-adrenergic, non-cholinergic'

eg. NO, ATP, NPY


What is co-transmission?

More than one NT can be released at one time


How does the ANS differ from the CNS in terms of the primary transmitters?

ANS: Ach and NA

CNS: glutamate and GABA


Describe the junctions of ANS nerves and their target organs?

No easily visible junction

More than one transmitter release site per axon

Extra-junctional receptors present 


Where are sympathetic preganglionic neurons found?

Interomediolateral cell column of spinal cord

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Where are sympathetic postganglionic neurons located?

Two locations and functional classes: 



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What is the function of sympathetic ganglia?

Essential for integration and coordination of sympathetic control between organs/tissues


What are the functions of paravertebral and prevertebral sympatheitc ganglia?

Paravertebral: primary source of vasoconstrictor neurons

Prevertebral: primary source of neurons innervating non-vascular smooth muscle 


Describe the concept of convergence and divergence of sympathetic postganglionic neurons?

Convergence: particularly prevertebral ganglion neurons integrate signals from multiple inputs

Divergence: up to 200 ganglion neurons can be activated by one preganglionic neuron

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Why is divergence in postganglionic neurons important?

Allows coordination of effects in many tissues at once


What is the major function of the sympathetic nervous system?

'Fight or flight' functions

Also activation of adrenal gland > release A and NA, broad activation of adrenoceptors 

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List the three nuclei in the cranial component of preganglionic parasympathetic neurons?

Edinger-Westphal nucleus

Salivatory nuclei

Dorsal motor nucleus of vagus and nucleus ambiguus

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Where are the sacral preganglionic parasympathetic neurons located?

Sacral spinal cord 

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Describe the special features of autonomic supply to the pelvic organs?

Project in pelvic splanchnic nerves to pelvic ganglia (pelvic plexus)

Extensions of this plexus lie close to or within pelvic organs 

Many of the PS ganglion neurons have unusually long axons 

Also contain many sympathetic neurons: mixed ganglia 

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What is the function of the parasympathetic nervous system?

'Rest and digest' functions 


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Do the sympathetic and parasympathetic nervous systems always act antagonistically? 


There are very few cases when the two systems are genuinely antagonistic at the cellular level 

More commonly, actions are on different tissues to cause different types of actions 

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Give examples of situations when the sympathetic and parasympathetic nervous systems are not acting genuinely antagonistically?

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What is the best way to distinguish between the sympathetic and parasympathetic nerves?

Anatomically: location of preganglionic neurons

Sympathetic: thoracic, lumbar spinal cord

Parasympathetic: cranial nuclei, sacral spinal cord


Describe a typical autonomic reflex?

Visceral afferent neurons provide input to local interneurons and projection neurons

Most autonomic reflexes are supraspinal, and involve brain input

Output to periphery via autonomic ganglion 


Describe the nucleus of the solitary tract?

Caudal part located in medulla

Major integrative centre for autonomic function

Second order sensory neurons


Describe the inputs and outputs of the nucelus of the solitary tract?

Input: visceral afferents

Output: 1. feedback to local reflexes that control organ function; or 2. provide info to higher centres to drive more complex responses

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Why is the hypothalamus important in the ANS?

Most importnant brain region for coordination of autonomic output


What are the inputs to the hypothalamus?

Sensory pathways

Intrinsic sensory stuctures

Circularting hormones


What is the major role of the hypothalamus in the ANS?

Compares situation to biological set points, and adjusts behaviour and autonomic function if necessary


What does the hypothalamus integrate with to determine its output?

Higher cortical and limbic systems

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