Intro To The ANS Flashcards
Detail the anatomy of the autonomic nervous system
• Autonomic Nervous System- Involuntary actions
• Connection between CNS and peripheral organs
• Two neurone systems – sympathetic and parasympathetic
o Often have opposing effects on a tissue
o Some tissues have a single nerve supply
o Rarely both branches have the same effect
• Sympathetic (fight and flight) & Parasympathetic (Rest and digest)
Give examples of pre- and post- ganglionic sympathetic neurotransmitters
The cranial nerves
- Cranial nerve III (oculomotor) - goes to the pupil of the eye
- Cranial nerve VII ( facial) - goes to submaxillary, sublingual and lacrimal glands
(secretory glands)
- Cranial nerve IX (glossopharyngeal) - goes to the parotid glands
- Cranial nerve X (vagus) - goes to the heart, kidneys, bronchi, GI tract to colon
Sacral nerves nerves
- Remainder of GI tract, bladder and genitalia
Sympathetic nerves
- Origins within thoracic and lumbar regions of the spinal cord
- Pre ganglionic fibre is short in the sympathetic nerves - meaning we have a chain of
ganglia called paravertebral chain lying close to our spine
- All the pre ganglionic fibres joined up together with the postganglionic fibre coming
out
Superior cervical paravertebral ganglia - post ganglionic fibres going to the pupil, facial glands and head circulation
Middle and inferior paravertebral ganglia - going to heart and lungs
Remaining paravertebral ganglia - going to sweat glands, pilomotor ( hair) muscles, blood vessels of skeletal muscle and skin
Prevertebral ganglia ( near aorta) - going to GI tracts
Difference between the 2 systems = para = cranial and sacral outflow, sympathetic = thoracic and lumbar outflow
Describe how the two branches of the autonomic nervous system impact on the body
- Sympathetic nervous system – FF
- Thoraco-lumbar outflow
- Short pre-ganglionic fibres
- These release acetylcholine (same chemical in every ganglia) and has nicotinic receptor
- Noradrenaline is main terminal messenger but ATP also is released
- Parasympathetic nervous system – R and D
- Saccro-cranial outflow
- Long pre-ganglionic fibres
- Acetylcholine release from these fibres which interact with nicotinic receptors
- Acetylcholine is main terminal messenger in parasympathetic nerves
- Exception is NO released or VIP
Describe ganglionic transmission
- in every ganglia it is Ach being released irrespective of if it is para or sympa
- The receptor = neuronal form of nicotinic acetylcholine receptor (N2 or Nn)
Somatic vs autonomic
1) Somatic or Motor system
• Transmitter released is Acetylcholine
• Interacts with nicotinic receptors on skeletal muscles
• Heavily myelinated – high resistance lipid coating to allow effective and fast nervous transmission
2) Autonomic Nervous System
• Autonomic NS Space in between two neurones are ganglia
• Autonomic ganglia all have Ach as main transmitter in parasympathetic and sympathetic
Parasympathetic - Longer pre-ganglionic fibre and short post-ganglionic fibre
- ganglia are in target organ
- Terminal chemical released in acetylcholine
- Lightly myelinated (slight slower conduction) and second neurone
- nerves leave CNS, release Ach in ganglia, activate nicotinic acetylcholine receptors on second neurone called post ganglionic-fibre. When these stimulated, ACH released onto organ
- Salivary gland GI tract, Heart, acid cells
Sympathetic – Shorter pre-ganglionic fibre and longer post-ganglionic fibre
• Sympathetic ganglia are in spinal cord
• Mostly: Ach interacts with nicotinic acetylcholine receptors to cause fast depolarisation and second fibre, post-ganglionic now released noradrenaline
o Arteries, heart
• Less often: postganglionic fibres release Ach to have effect
o Sweat glands
• Specialised sympathetic nerve: No second nerve, and so in effect a modified ganglion
o Lightly myelinated pre-ganglionic fibre, releasing Ach, which interacts with receptors in adrenal glands
o Adrenal gland
Ganglia
• pre-ganglia releases acetylcholine which mainly stimulates nicotinic receptors = fast activation of next neurone
- Sympathetic – take up tyrosine, metabolises and creates and stores noradrenaline and releases it
- Parasympathetic- take up choline, create acetylcholine and released acetylcholine
Parasympathetic nerves
• Top and bottom of CNS outflow
• Red box indicates outflow of parasympathetic nerves
• Outflow is either facial or sacral (GI tract, bladder and genitalia)
• Four nerves
o Cranial nerve 3 (Oculomotor) to pupil
o Cranial nerve 7 (facial) – to glands - submaxillary, sublingual and lacrimal glands
o Cranial nerve 9 (Glossopharyngeal) to parotid glands which forms saliva
o Cranial nerve 10 (Vagus) to heart, kidneys, bronchi and GI tract to colon
Sympathetic nerves
- Very different anatomy
- Middle of CNS outflow – thoracolumbar outflow
- Preganglionic fibres are short and form chain of ganglia right next to the spinal chord
- Prevertebral chain of ganglia about 25 chains down spinal cord and a few prevertebral ganglia near aorta
- This chain has a long postganglionic fibre going to the organs
- Sympathetic nerves – thoracic or lumbar section of spinal chord
- Acetylcholine in ganglia but its sympathetic ganglia
Four nerves
- Superior cervical ganglia – to pupil, facial glands, head circulation
- Middle and inferior ganglia – heart and lugs
- Remaining ganglia – sweat glands, hair muscles, blood vessels and skin
- Ganglia for GI tract
Antagonistic effects
- Vagus nerve innovates pacemaker nodes (SAN and AVN)
- Stimulate Vagus, slows heart rate
- Sympathetic nerves – innovate (SAN, AVN and ventricles)
- Stimulate sympathetic nerve – faster heart rate
Single input tissues
- Blood vessels and sweat glands – only sympathetic nerve
- Cerebral circulation – have parasympathetic nerves
• Bronchial smooth muscle and ciliary muscle of the eye – only parasympathetic
Non-adrenergic non-cholinergic (NANC) transmitters
- Most of chemical transmitters are noradrenaline and acetylcholine
- Noradrenaline usually co-released with other chemicals (ATP)
• ATP/neuropeptide Y (NPY) are released with noradrenaline – a lot of sympathetic nerve will release these
o The post-ganglionic sympathetic neurone causes vasoconstriction
• Vasoactive intestinal peptide(VIP) released by parasympathetic nerves
o In salivary glands or bronchiole smooth muscle and causes dilation
• Nitic Oxide (NO)
o Parasympathetic pelvis nerves cause erection by releasing NO, which dilates erectile tissue and small arteries to cause response
Parasympathetic vs sympathetic physiological responses
Pupil: constricts vs dilates
Saliva and tear production: stimulates vs inhibits
Bronchi: constricts vs dilates
Heart: slows vs accelerates
Stomach,pancreas and intestines; stimulates vs inhibits
Urination: stimulates vs inhibits
Genitals: promotes erection vs promotes ejaculation and vagina contractions
Symp: stimulates glucose release and stimulates epinephrine and norepinephrine release
