10. ANS Flashcards
What are the three divisions of the ANS?
Sympathetic, Parasympathetic, Enteric
Which neurons are myelinated in the autonomic NS?
Preganglionic. Post are unmyelinated
What NTs are used in the autonomic NS?
Preganglionic use ACh, Postganglionic use noradrenaline or ACh
What type of receptors are present in the ANS?
Nicotinic in ganglia, muscarinic (PS) or adrenergic (S) in target tissues
How do somatic and autonomic neurons differ?
Somatic has one long neuron, autonomic has a chain of two with an autonomic ganglion
How do parasympathetic and sympathetic neuron chains differ?
PS neuron chains have long preganglionic neurons and short postganglionic neurons. Sympathetic neuron chains have short preganglionic neurons and long postganglionic neurons
Where do parasympathetic pre-ganglionic neurons originate from?
Where do sympathetic pre-ganglionic neurons originate from?
Cranial nerves (III, VII, IX, X), spinal cord (S2-S4), craniosacral outflow Lateral horn of the spinal cord (T1-L2), thoracolumbar outflow
Where do parasympathetic nerves synapse?
Where do sympathetic nerves synapse?
Some in head, some in ganglia close to target organ
Sympathetic chain, prevertebral ganglia
Why is signal conduction faster in the PS pathway?
Only has visceral distribution, while Sympathetic neurons must travel through the sympathetic chain
What effects does the ANS have on blood vessels?
Sympathetic - dilation of coronary and skeletal muscle (alpha receptors), constriction of skin and abdominal (beta receptors)
No PS innervation
How are the pancreatic islet cells affected by the ANS?
Sympathetic - increase glucagon secretion, decrease insulin secretion
PS - increase insulin and glucagon secretion
Where do visceral afferent nerves feed in to?
The nucleus tractus solitarius (NTS), which sends info to hypothalamus and brain stem ANS centres
How is the adrenal medulla innervated?
Preganglionic sympathetic neurons synapse directly onto the medulla. Essentially a modified sympathetic ganglion
What is the secretatory output of the adrenal medulla?
Noradrenaline and adrenaline (75-80%) secreted from neuroendocrine cells.
How is the fight or flight response initiated?
By adrenal secretions which act on adrenergic receptors of organs supplied by postganglionic sympathetic neurones. Also other organs with adrenergic receptors
