Autonomic System Flashcards
What two divisions are there in the autonomic nervous system?
- sympathetic
- parasympathetic
What does the sympathetic division do?
Produces the responses seen in fright, fight or flight
What does the parasympathetic do?
Produces the changes in the resting, recovering or restorative state
What effects are seen in the sympathetic response?
- pupils dilate
- heart rate and force increases
- vasodilation
- decreased gut motility and secretion
- saliva secretion reduced
What effects does the parasympathetic division have?
-pupils constrict
-gut motility and constriction increases
-saliva secretion increases
(-vessels not connected)
-decreased heart rate
What controls most visceral organs?
Both the parasympathetic and the sympathetic
What is craniosacral?
Brainstem and sacral spinal cord
What is thoracolumbar?
Thoracic and lumbar segments 1-3
How are ANS effectors regulated?
Neurons of the CNS regulate the effectors of the ANS through autonomic ganglia neurons
Which division of the ANS regulates cardiac output in the short term?
Sympathetic
What is the major structural difference between the parasympathetic and the sympathetic?
- the parasympathetic preganglionic fibres are long (from the CNS) whereas the sympathetic are shorter
- the parasympathetic postganglionic fibres are short (to the target) whereas sympathetic are short
What is the neurotransmitter at all autonomic ganglia?
Acetylcholine
What transmitter do parasympathetic postganglionic fibres release?
Acetylcholine
What transmitter do most sympathetic postganglionic fibres release?
Noradrenaline
What exceptions are there for sympathetic postganglionic fibre transmitters?
Acetylcholine: sweat glands, skeletal muscle blood vessels
NO: erectile tissue
Postulated: substance P, serotonin, ATP plus others
What do acetylcholine receptors also respond to?
Administered doses of nicotine and muscarine
What receptors does the heart have for the sympathetic system?
Has beta-1 receptors to respond to noradrenaline to increase rate and force of contraction
What does the parasympathetic system act on on the heart?
Acetylcholine acts on pacemaker (sino atrial node) and slows the inherent rhythm
(vagal tone)
What chronotropic changes does the ANS have on the heart?
sympathetic = weak, positive parasympathetic = strong, negative
What inotropic changes does the ANS have on the heart?
sympathetic = strong, positive parasympathetic = weak, negative
What does the sympathetic division do to blood vessels?
alpha receptors on most organs mediate constriction
Do blood vessels have a parasympathetic supply?
No, other than erectile tissue
What does the sympathetic do to the lungs?
Beta-2 receptors mediate dilation of the airways
What does the parasympathetic do to the lungs?
bronchioles constrict
What does salbutamol do to the lungs?
Selectively dilates bronchioles by activating beta-2 receptors
Why does salbutamol not affect the heart?
Heart has mainly beta-1 receptors
What effect does sympathetic have on the adrenal medulla?
Preganglionic fibre from CNS release acetylcholine which stimulates the release of adrenaline and noradrenaline into the blood to back up the sympathetic response
What effect does the parasympathetic have on the adrenal medulla?
None
What is hexamethonium?
An autonomic ganglion-blocking agent
What does hexamethonium do?
- removes sympathetic tone
- abolishes parasympathetic response
- parlous state
