Autonomic Nervous System Flashcards
What is the autonomic nervous system also called?
Visceral nervous system
What system makes up the basic anatomy of the ANS?
Two-neuron system
Describe the structure of the two-neuron system
– Pre-ganglionic fibers originate from the CNS
– Post-ganglionic fibers originate from autonomic ganglia
Where are the fibre origins of the sympathetic nervous system?
Pre-ganglionic
Thoracolumbar
Post-ganglionic
Paravertebral Chain Prevertebral Ganglia
Where are the fibre origins of the parasympathetic nervous system?
Pre-ganglionic
Craniosacral
Post-ganglionic
In or Near Target Organ
What structures do the parasympathetic system control?
Eye (III) Lacrimal gland (VII) Salivary glands (VII) Heart (X) Lung (X)
Upper GI tract (Nervi erigentes -> pelvic ganglia)
Bladder (Nervi erigentes -> pelvic ganglia)
Genitalia (Nervi erigentes -> pelvic ganglia)
What structures do the sympathetic system control?
Structures in head and neck (Eye, blood vessels, salivary glands, etc)
Heart Lungs Adrenal medulla Liver (prevertebral medulla) GI tract (prevertebral medulla) Bladder Genitalia Blood vessels (paravertebral sympathetic chain (bilateral) -> segmental outflow) Sweat glands etc (paravertebral sympathetic chain (bilateral) -> segmental outflow)
What provides sympathetic supply to organs in the head?
Internal carotid (sympathetic) plexus
Describe the anatomy of the sympathetic trunks
Each sympathetic trunk extends as far as the atlas and they fuse with each other in the ganglion impar opposite the coccyx There are superior, middle and inferior cervical ganglia, the latter often fuses with the T1 ganglion to form the Stellate Ganglion that lies on the neck of the 1st rib
What are the three sympathetic prevertebral ganglia?
Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
What does the celiac ganglion supply?
Adrenal gland Liver spleen stomach small intestine proximal colon kidney
What does the superior mesenteric ganglion supply?
Distal colon
What does the inferior mesenteric ganglion supply?
Distal colon
Rectum
Urinary bladder
Genitalia
Describe the autonomic motor reflex
Impulse travels from sensory afferent neuron to spinal cord where it joins the interneuron. Signal then passes from sensory afferent neuron to interneuron to preganglionic fibre.
Signal then goes to autonomic ganglion then postganglionic where signal takes effect on the target tissues
What myelinated the postganglionic fibre of the autonomic nervous system?
Trick question, post ganglionic fibre in non-myelinated and preganglionic fibre is lightly myelinated
What phrase related to the parasympathetic nervous system do you associate with a tiger on a tree in Mrs Simpsons class?
Rest and digest
What phrase is often used to describe the action of the sympathetic nervous system?
Fight or flight
What effect does What does the superior mesenteric ganglion supply?
Decreased rate of contraction
What muscle of the eye has parasympathetic innervation and what does it do?
Pupillary constrictor muscle, causes miosis
What muscle of the eye has only sympathetic innervation and what does it do?
Pupillary dilator muscle, causes mydriasis
What effect would a sympathetic agonist have on the eye?
Mydriasis (dilation)
What effect would a parasympathetic agonist have on the eye?
Mydriasis (dilation)
What is the function of the ANS when bladder is filling?
Sympathetic control predominates
• Relaxation of detrusor muscle
• Contraction of internal sphincter muscle
What is the function of the ANS when bladder is full?
Parasympathetic control predominates
• Contraction of detrusor muscle
• Relaxation of internal sphincter muscle
What is the basic physiology of sympathetic and parasympathetic innervation?
- may oppose or compliment
- may (rarely) have same effect (e.g. saliva)
- Some tissues only innervated by one
What is the basic physiology of autonomic reflex arcs?
Autonomic reflex arcs exist for visceral control
• Path of afferent fibers can explain referred pain
What is are the generalised effects of the ANS?
- Parasympathetic – “rest and digest”
* Sympathetic – “fight or flight”
What are varicosities?
Typically, long postganglionic sympathetic fibers lead from the sympathetic chain to the target organ where they are terminated with bulbous enlargements called varicosities. This modified axon endings release a neurotransmitter (in the case of sympathetic nervous system norepinephrine) into its surroundings
Discuss the sympathetic innervation of the adrenal gland
Preganglionic sympathetic fibers synapse on chromaffin cells
Chromaffin cells release adrenaline (~80%) and noradrenaline (~20%) into systemic circulation
-> widespread tissue response
What do all pre-ganglionic neurons in the parasympathetic sympathetic system release?
ACh, acetylcholine for nicotinic receptors
What do all postganglionic parasympathetic neurons
release?
ACh, acetylcholine for muscarinic receptors
What do postganglionic sympathetic neurons release?
- Most release noradrenaline
* Some release ACh (i.e. sweat glands)
