Sympathetic And Parasympathetic Nervous Systems Flashcards
Effects of the sympathetic nervous system
Fight or flight Increased heart output Increased blood flow Increased respiration Reduced digestion More glucose in blood More saliva Inhibition of urination pupil dilation Sweating Orgasm
Noradregenic neurotransmission mechanism
- Tyrosine synthesized to noradrenaline (via dopamine)
- All products of noradrenaline synthesis such as dopamine are called monoamines and they geat broken down by the enzyme monamine oxidase. Noradrenalie escapes this by being stored in in vesicles called VMAT (can be inhibited by reserpine)
- Released into synapse, causing negative feedback by binding to presynaptic alpha2 receptors and preventing further release. Reuptake via uptake 1 channels.
- Interaction with adrenergic receptors (in smooth muscle alpha In cardiac muscle beta)
- Inactivation of signal by breakdown of NA by enzymes monoamine oxidase and COMT. Also reuptake by uptake 1 channel (neuron) and uptake 2 channel (non neuron cell)

What alpha 1, Alpha 2, beta 1 and beta 2 receptors innervate
A1: smooth muscle p, bladder, intestines p, pupil, liver, ejaculation
A2: widespread. INHIBITS transmitter release
B1: cardiac muscles
B2: smooth muscle Vasodilation Broncodilation, glycogen mobilizations
Parasympathetic pathway of transmission
Acetylcholine to nicotinic then acetylcholine to muscarinic

Sympathetic pathways of transmission
Acetylcholine to nicotinic then noradrenaline to alpha and beta adrenergic receptors (blood vessel) Acetylcholine to nicotinic then noradrenaline to muscarinic (sweat glands) Acetylcholine to nicotinic then through blood as adrenaline then acts on alpha and beta adrenergic receptors (

Muscarinic receptors structure and second messengers.
G protein. 5 subtypes 2 of which are important:
M2 (cardiac) lowers cAMP
M3 (smooth muscle/ glands) increased IP3 and DAG causing contraction

Adrenergic receptors (2 alpha and 2 beta subtypes) what second messengers are invloved and effect
Alpha and beta subtypes
Alpha 1: stimulates IP3/ Ca and DAG - increases calcium levels
Alpha 2: inhibits adenylate cyclase lowers cAMP - decreases release of noradrenaline
Beta: increase cAMP
B1 cardiac
B2 vascular airways
B3 adipose p, bladder
Nicotinic receptors
Non selective action channels, causes depolarization of membrane

Non cholinergic , non adrenergic neurotransmission examples of things they release causing vasodilation/ vasoconstriction.
Some fibers release other neurotransmitters or cofactors. Called NANC
Vasodilation: Nitric oxide, intestinal polypeptides along with Ach
Vasoconstriction: Neuropeptide Y and ATP released along with noradrenaline.
Parasympathetic effects on heart
Decrease heart rate, cardiac output, blood pressure
Reduced conduction velocity in AV node
Parasympathetic effects in blood vessels
Causes vasodilation (e.g. causing penis erection)
Mediated by vagus and sacral nerves BUT small role of PNS on this. Because very few vascular beds are parasympathetically innervated.
Parasympathetic effects on other smooth muscle
Non vascular smooth muscle is contracted (bronchioles, GI tract contracts except sphincters that relax)
Parasympathetic effects on secretion and nerves affected
Bronchosecretion (vagus)
Gastrointestinal secretions (vagus)
Salivary secretions (glossopharyngeal)
Lacrimal glands (fascial nerve)
Parasympathetic effects on the eye and associated nerve
Accommodation for near vision by contraction of ciliary muscle Pupil constriction by contraction of sphincter papillae muscle.
Mediated by oculomotor nerve
Botulinum toxin. What it does and what it can be used to treat.
Binds to and degrades receptor responsible for exocytosis of ACh amongst other neurotransmitters
Is used as a drug to treat overactive bladder
Enteric nervous system
Made up of myenteric and submucosal plexuses which control most functions of the gut. Parasympathetic and sympathetic effects on gi tract occur via modulation of enteric NS
2 types of cholinergic receptors
muscarinic (Glands) and nicotinic (ganglionic transmission)
Cholinergic neurotransmission: how it works from neuron to synapse and what enzymes are involved

Sympathetic effect on: the heart, arteries and veins and respiratory system

Sympathetic effects on: the gut, metabolism, salivary glands and bladder

Sympathetic effect on: sexual function, the eye and the skin

Reuptake of noradrenaline in synapse. 3 different ways it is recycled.
- Uptake 1 receptors
- Uptake 2 receptor (uptake in tissue and metabolism by COMT)
- MAO breaksdown adrenaline by converting it to noradrenaline aldehyde then aldehyde dehydrogenase to DOMA.

What adrenergic receptors (alpha 1 and 2, beta 1 and 2) the following sympathomimetic drugs influence.


Effect of phentolamine (alpha adrenergic blocker)
Non selective alpha blocker. Both reuptake receptor and effector receptor are inhibited.

Effect of prazosin (alpha drenergic blocker)
Alpha 1 selective blocker. So alpha 2 reuptake is not affected only effector alpha 1 receptor.

Main effect of beta 1 and 2 adrenergic blockers and specific effect of:
Labetalol
Atenolol
Salbutamol
Beta 1 blockers: sympathetic cardiac function reduced
Beta 2 blockers: respiratory and birth sympathetics reduced
Labetalol: non selective beta 1 and alpha 1 blocker.
Atenolol: selective b1 blocker
Salbutamol: slective b2 agonist (used for bronchodilation in asthma)