Autonomic nervous system Flashcards
Map of ANS in body
Parasympathetic
- Brainstem
- S2-S4
Sympathetic
- T1-L2
Axons of ANS
Always synapse at ganglia [di-synaptic pathway]
- EXCEPT sympathetic supply to adrenal medulla
General parasympathetic neuronal pathway
Cranial nerve nuclei/ Grey matter spinal cord—-[myelinated preganglionic axon]—->
Cranial/ spinal nerve—-> Parasympathetic ganglion——[unmyelinated postganglionic axon]—>
Effector organ
General sympathetic neuronal pathway
Grey matter spinal cord—[myelinated preganglionic axon, spinal nerve]—–>
Sympathetic ganglion{synapse}—–[unmyelinated postganglionic axon]—–>
Effector organ.
Neurotransmission in ANS pathways
- Ganglia
- Postganglion, sympathetic neurones
- Adrenal medulla
In ganglia
- Ach is NT released
- Bind on nicotinic receptors on postganglionic neurones [fast]
Post-ganglionic sympathetic neurones:
- Noradrenaline released [XC in sweatglands, Ach used]
- Binds to adrenergic receptors [slow]
Adrenal medulla:
- Ach released
- Binds to nicotinic receptors on chromaffin cells
- Causes release of adrenaline/noradrenaline into the blood= activation of sympathetic effector organs
Alpha-1 adrenergic receptors
G-protein coupled receptor
- Responds to Noradrenaline
Found on blood vessel smooth muscle
Beta-1 adrenergic receptors
Found in the heart
G-protein coupled receptor
- Responds to Noradrenaline
Beta-2 adrenergic receptors
Found on bronchial smooth muscle cells.
G-protein coupled receptor
- Responds to Noradrenaline
Prazosin
Anti-hypertensive —-> Alpha-adrenergic antagonist
Atenolol
Anti-hypertensive—-> Beta-adrenergic antagonist
Salbutamol
Short acting, beta-2 agonist
- Treatment for asthma
Neurotransmission
- Postganglionic parasympathetic neurones
Ach is released
- Binds to muscarinic receptors on effector organs [slow]
Atropine
Muscarinic antagonist
Treatment for:
- Bradycardia
- Dilate pupils
- Reduction of glandular secretions
White rami communicans
Section of preganglionic fibre that enters the sympathetic trunk
- T1-L2
Sympathetic trunk
Interconnected paravertebral ganglia from cervical to sacral levels.
Preganglionic fibres entering sympathetic trunk
Either:
- Synapse in paravertebral ganglion
or
2. Pass through paravertebral ganglio n without synapsing —> form splanchnic nerve and synapse at prevertebral ganglion
Route of post-ganglionic fibres from sympathetic trunk
To the periphery:
- Back into spinal nerves via grey rami communicans
To the viscera
- Via medial branches/ plexus
Route of post-ganglionic fibres from pre-vertebral ganglia
Postganglionic fibres from sympathetic trunk from plexus around viscera.
Cervical sympathetic trunk
3 ganglia
- Superior
- Middle
- Inferior
Satellite- Inferior + T1 ganglia
Sympathetic supply to the upper limbs
Post-ganglionic fibres of the cervical ganglia
- Exit via grey rami communicans
- Enters spinal nerves
Cervical Sympathetic supply to the heart
Post-ganglionic fibres of cervical sympathetic ganglion
- Travels down common carotid artery to the heart
- Contributes to cardiac plexus
Cervical Sympathetic supply to the head
Postganglionic fibres of the superior cervical ganglion
- Travels up the internal —-> Internal carotid plexus
- To eye
- To lacrimal gland
- Travels up external carotid artery—-> External carotid plexus
- To submandibular and parotid glands
Pterygopalatine ganglion
Parasympathetic ganglion
- Branch of facial nerve [petrosal nerve] synapses here
- Postganglionic fibres contribute to internal carotid plexus [lacrimal gland and nose mucosa]
Horner’s syndrome
Combination of symptoms caused by disruption to sympathetic supply to the head
Any pathway between the hypothalamus to preganglionic neurones is affected
- Descending autonomic pathways [e.g MS]
Symptoms:
- Pupil constriction [miosis]
- Drooping eyelid [ptosis]
- Skin [anhydrosis]
Thoracic splanchnic nerves
Preganglionic fibres from thoracic sympathetic nerves.
Three nerves:
Greater
Lesser
Least
Pierces the diaphragm and synapses in pre-vertebral ganglia:
- Celiac
- Superior mesenteric
- Aorticorenal
Post ganglion fibres from pre-vertebral plexus around viscera.
Celiac ganglion
Pre-vertebral ganglion where thoracic splanchnic nerve synapses
- Supplies stomach + duodenum.
Superior mesenteric ganglion
Pre-vertebral ganglion.
- Thoracic splanchnic nerves synapses here.
Supplies small intestines
Aorticorenal ganglion
Pre-vertebral ganglion
- Location of synapse for thoracic splanchnic nerves
Supplies kidney innervation.
Thoracic sympathetic trunk ganglia
12 in total.
Post-ganglionic fibres:
- Grey rami communicans —> spinal nerves
- Medial branches —> heart and lungs [cardiac and pulmonary plexus]
Lumbar sympathetic trunk
- How many
- Postganglionic exit
- Preganglionic exit
4 ganglia
Postganglionic exit:
- Grey communicans to spinal nerves
Preganglionic exit:
- Lumbar splanchnic nerves—> synapse in pre-vertebral ganglia in pelvis
- Inferior mesenteric ganglion
Inferior mesenteric ganglion
Pre-vertebral ganglion
- Lumbar splanchnic nerves [preganglionic fibres] synapse here
Supplies large intestine
Sacral sympathetic trunk ganglia
- How many?
- Post-ganglionic exit
4 ganglia in total
Post-ganglionic exit:
- Grey rami communicans to spinal nerves [supplying lower lim]
- Sacral splanchnic nerves to pelvis organs.
Parasympathetic preganglionic neurones
Located in:
- Brainstem [become cranial nerves]
- Grey matter spinal cord [S2-4]—> pelvic splanchnic
Location of preganglionic neuronal cell bodies
Cranial nerve nuclei
CN 3 nucleus
Edinger-Westphal nucleus
CN 7 nucleus
Superior-salivatory nucleus
CN 9 nucleus
Inferior salivatory nucleus
Vagus nerve nucleus
Nucleus ambiguous
Dorsal motor nucleus
Ciliary ganglion
Parasympathetic ganglion
- Oculomotor nerve synapses here
- Innervates sphincter pupillae [pupil constriction]
Submandibular ganglion
Parasympathetic ganglion
- CN VII synapses here
- Innervates submandibular gland
= watery saliva
Otic ganglion
Parasympathetic ganglion
- Glossopharyngeal nerve synapses here.
- Innervate parotid gland= watery saliva
Sacral parasympathetic innervation
- Preganglionic exit
- Innervation
Preganglionic fibres exits via pelvic splanchnic nerves
Innervates pelvic organs
- Forms pelvic plexus
- Preganglionic fibres synapse directly onto target organs
Sacral parasympathetic function
- Bladder
- Rectum
- Sexual function
Bladder= urination
- Contracts bladder wall
- Inhibits sphincter
Rectum= defecation
- Inhibits sphincter
Sexual function = vasodilation of erectile tissue
Enteric nervous system plexi
Auerbach/ Myenteric plexus = smooth muscle contraction regulation
Meissner’s/ Submucosal plexus = regulation of glandular secretions
