Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Autonomic NS
Organisation of the Body
| Question | Answer |
|---|---|
| What is the ANS | A subdivision of the peripheral nervous system motor efferents Made of sympathetic, parasympathetic and enteric nervous systems |
| Sympathetic nervous system key features | Segmental chain ganglia No axons from brain or cervical/sacral spinal cord Three midline ganglia (pre-vertebral) supplying the gut Short pre-ganglionic and long post-ganglionic nerves |
| Why is the sympathetic NS segmental | The neural crest migrates through the rostral half of each somite and forms the segmental sympathetic chain ganglia A consequence of embryology |
| Parasympathetic NS key features | Output in cranial nerves and sacral spinal cord No segmental ganglia Ganglia close to targets Long pre-ganglionic and short post-ganglionic nerves |
| Neurotransmitters of the ANS | Sympathetic and parasympathetic have the same neurotransmitter at pre-ganglionic neurons - Acetylcholine The have different post-ganglionic neurotransmitters; Sympathetic - norepinephrine Parasympathetic - Acetylcholine |
| Autonomic nerve junctions | The terminals of autonomic nerves are called varicosities A series of enlargements where neurotransmitter is released The equivalent to synapses |
| Neuromodulators | Can also be released at autonomic nerve junctions Modulate action of primary transmitters Sympathetic - NA, ATP and Neuropeptide Y Parasympathetic - ACh, ATP, Vasoactive intestinal polypeptide, NO Enteric - ATP, NO, VIP, ACh, Substance P |
| Sweat glands | Sympathetic innervation that uses ACh not NA Due to late phenotypic switch of the post ganglionic sympathetic innervation During early post-natal development CNTF produced by sweat glands causes sympathetic neurons to release ACH |
| Hyperhidrosis | Caused by excessive activation of sympathetic nerves - no voluntary control over ANS Chain can be cut or injected with botulinum toxin to prevent sympathetic stimulation -downregulated transmission to sweat glands This is reversible-anticholinergic drug |
| Roles of sympathetic nerves | Piloerection - useful to conserve heat in furred animals Peripheral vasoconstriction - controls heat release Lipolysis - innervation of white adipose tissue causes fat breakdown |
| Paravertebral chain of sympathetic ganglia | Superior cervical ganglion - head Middle cervical and stellate ganglia - heart and lungs Para-vertebral thoracic chain of ganglia - abdominal and pelvic organs |
| How are sympathetic ganglia innervated | Preganglionic emerge from white ramus - postganglionic from grey ramus Some preganglionic nerves terminate in the ganglia Some pass along the chain before terminating Some pass to pre-vertebral/midline ganglia via splanchnic nerves |
| Splanchnic nerves | Celiac ganglion supplies the foregut-innervated by greater splanchnic nerve Superior mesenteric ganglion supplies the midgut - innervated by lesser splanchnic nerve Inferior mesenteric ganglion supplies the hindgut - innervated by least splanchnic nerve |
| Parasympathetic - Cranial nerve III | Stimulation of the oculomotor parasympathetic nerves stimulates post-ganglionic fibres from the ciliary ganglion that innervate the iris constrictor muscles Causes pupil constriction |
| Pupil reflex | Parasympathetic input to the ciliary ganglion constricts the pupil decreasing light passage to the retina - increased by Opiates (pinpoint pupils) Sympathetic stimulation causes dilation of the pupil increasing light passage to the retina - Amphetamines |
| Horner's syndrome | Due to lesion of the sympathetic superior cervical ganglion e.g. due to carotid artery lesions as anatomically related Leads to pupil constriction, eyelid drooping and dry, flushed facial skin |
| Parasympathetic - Cranial nerve VII | Controls lacrimation Innervated the pterygopalatine ganglion regulating secretions of the lacrimal gland and nasal mucosa Innervated the submandibular ganglion regulating secretions from submandibular and sublingual salivary glands |
| Parasympathetic - Cranial nerve IX | The Glossopharyngeal nerve To Otic ganglion for parotoid gland - controls salivary secretions Parasympathetic stimulation of the otic ganglion leads to increased secretion of saliva from the parotid glands |
| Role of ANS in cardiovascular responses | Driven by CNS control centres Sympathetic innervation of cardiac muscle controls strength and frequency of contraction Heart rate increases, force of contraction increases and conduction increases |
| Bronchodilation | The volume of air in the lungs (due to bronchiole diameter) is controlled by the sympathetic nervous system This does not control the rate of respiration - that is spinal nerves innervating the diaphragm and intercostal muscles |
| Fight or flight - what causes it | Sympathetic stimulation of he adrenal medulla by the greater splanchnic nerve Tells the adrenal gland to release NTs into the blood - the same as released by the nervous system Adrenaline and noradrenaline |
| Fight or flight - effects | Pupils dilate Heart rate increases Peripheral vasoconstriction + muscle vasodilation Kidney increases renin Bronchodilation Increased glycogenolysis and gluconeogenesis in liver Lipolysis in adipocytes Decreased saliva Decreased GIT motility |
| Adrenal medulla tumours | Paragangliomas phenocopy the fight or flight state These produce catecholamines and secrete them into the blood People feel anxious, depressed and experience weight loss and tachycardia Can be detected by increased catecholamines in the blood |
| Why do adrenal and SNS cells produce the same NT | Chromaffin cells and SNS neurons have a common embryonic origin They both develop from the same precursor cell - produce the same NT |
| Parasympathetic - Cranial nerve X | The vagus nerve (wandering nerve) Parasympathetic supply to thorax and abdomen (not to liver) Controls gut reflexes and motility |
| Baroreflex | Sensory nerve that run along the vagus nerve control blood pressure Piezo-2 expressing neurons in petrosal and nodose ganglia sense stretch in the aortic arch and carotid sinus (run along these attached to X cranial nerve) Control BP and HR |
| Micturition reflex | Sensory nerves sense bladder stretch and send signals to CNS - sympathetic Stimulation (Beta3) of the smooth (detrusor) muscle of the bladder wall, results in retention Parasympathetic leads to contraction of sphincter muscles via pudendal nerve |
| Male genital reflexes | Afferent via spinal and autonomic nerves Parasympathetic stimulation onto helicine arteries - dilation - erection Sympathetic stimulation leads to emission of seminal fluid and closure of bladder sphincter - ejaculation Pudendal nerve controls this |
| Defecation reflex | Normally anal sphincters are closed by sympathetic tonic stimulation Detection of a full sigmoid rectum via visceral sensory afferents Parasympathetic stimulation of bowel smooth muscle and inhibition of tonic sympathetic control of sphincters |
| Enteric nervous system | Parasympathetic nerve terminals from the vagus nerve innervating ganglion cells in the myenteric plexus of the gut wall The intrinsic nerve networks in the intestinal wall |
| Two plexi of the enteric nervous system | Submucosal plexus Myenteric plexus |
| Peristalsis | Food bolus in gut causes release of serotonin This stimulates submucosal plexus Which stimulates myenteric plexus to contract |
| Evidence for Peristalsis and role of NS | Optogenetic stimulation of calretinin expressing myenteric neurons promotes peristalsis AP propagates to myenteric neural network on activation - this causes smooth muscle contraction moving food through intestines |
| How does the enteric NS develop | The enteric crest arises only from cervical levels and colonises the entire gut Mouse neural crest cells can be viewed invading the gut and colonising the hindgut |
| Hirschsprung's disease and congenital megacolon | If invading crest cells do not enter the gut wall or fail to survive This produces a defective nerve plexus Leads to megacolon E.g. mutations in GDNF or its receptor c-ret |
Created by:
12345678987654321000000
Popular Medical sets