2.1 - Autonomic Nervous System Flashcards
ANS physiology and drugs that affect SNS
What are other names for the ANS?
Visceral, vegetative, or involuntary nervous system.
The efferent arm of the ANS is divided into which two branches?
Sympathetic and Parasympathetic
What are the names for the first and second neuron in the ANS?
Pre- and Post-ganglionic
Where do neurons in the SNS exit the CNS?
Thoracolumbar region
Where do neurons in the PSNS exit the CNS?
Cranio-sacral region
What are the cranial nerves in the PSNS?
III (Oculomotor)
VII (Facial)
IX (Glossopharyngeal)
X (Vagus)
Which branch of the ANS has diffuse effects in the body? Which has more localized effects?
Diffuse: SNS
Localized: PSNS
Where do SNS ganglia lie?
Along the spinal column (paravertebbral)
+ Few ganglia in core of body (prevertebral) e.g., celiac, and superior and inferior mesenteric
Which sacral nerves are innervates by the PSNS?
S2, 3, 4.
What do the pupils do when stimulated by SNS?
They dilate (Mydriasis)
What is mydriasis?
When the radial muscle contracts (pupil dilation)
What does SNS stimulation do to the heart?
Increases both then rate and force of contraction.
What does SNS stimulation do to the lungs?
Dilates bronchi
What does SNS stimulation do to the adrenals?
Stimulates release of adrenaline into the bloodstream.
How does SNS stimulation affect the vasoconstriction?
Constriction of BVs in:
Skin, GI system
Dilation of BVs in:
Skeletal muscles, heart
What does the SNS do to sex organs?
SNS is responsible for contraction of smooth muscle (ejaculation, vaginal contraction)
What does the SNS do to the urinary system?
Contraction of the internal urinary sphincter
+ Relaxation of detrusor muscle, to increase bladder reservoir.
What does the SNS do to the GI system?
Inhibits gastric secretions and intestinal secretions and motility
What does the SNS do to the liver and adipose tissue?
Increases glycogenolysis and lipolysis
What does SNS stimulation do to the sweat glands?
Increased diaphoresis
How does SNS stimulation affect coagulation?
It increases it
What is glycogenolysis?
Releases of glucose from hepatic glycogen stores (or locally within muscle stores)
What is lipolysis?
Release of free fatty acids stored originally in adipose tissue as triglycerides
What does PSNS stimulation do to the pupils?
Pupillary constriction (Miosis)
What is miosis?
Constriction of the ciliary muscle to accommodate near vision, pupil constriction.
Which branch of the ANS allows for accomodation?
The PSNS allows for miosis.
How does PSNS stimulation affect the heart?
It reduces the heart rate, and only reduces the force of atrial contraction (does not innervate ventricles)
How does PSNS stimulation affect the lungs?
Stimulates bronchoconstriction and increases secretions
Which branch of the ANS innervates only the atria?
The PSNS
How does the PSNS affect the GI system?
Stimulates secretion and motility of stomach and intestines.
How does the PSNS affect the sex organs?
Responsible for erection.
Point and shoot - prof
What does the PSNS do to the detrusor muscle and urinary sphincter?
Contraction of bladder, relaxation of internal urinary sphincter
How does the PSNS affect the BVs?
It does not innervate the BVs.
How does the SNS affect the kidneys?
It stimulates renin secretion
The PSNS has long or short pre- and post-ganglionic axons?
Long preganglionic and short postganglionic
The SNS has long or short pre- and post-ganglionic axons?
Short preganglionic and long postganglionic
Which area of the SNS has no postganglionic neuron?
The neuron that stimulates the adrenal medulla to release NE
Which hormone do all neurons in the PSNS release?
Ach
Most postganglionic neurons in the SNS release NE. Which ones do not?
The ones that innervate sweat glands release Ach.
(so does the one that communicates with the adrenals, but there is no postganglionic neuron there)
What hormone do the adrenal medullas secrete?
E, NE; 4:1 ratio
What is the difference between NE and E?
NE is a NT, E is a hormone.
Noradrenaline is released by postganglionic neurons, whereas adrenaline is released by the adrenal medulla.
In what sequence is adrenaline synthesized?
Tyrosine –> DOPA –> Dopamine –> Noradrenaline –> Adrenaline
Why would you administer DOPA to a pt?
They have a dopamine deficiency (Parkinson’s)
Where is noradrenaline converted into adrenaline?
Adrenal medulla
What happens to the majority of noradrenaline after it is released in vesicles and acts on target receptors?
Most of it undergoes reuptake, unless it is degraded by enzymes.
Which extra-neuronal enzyme can degrade noradrenaline?
COMT
–> Catechol-o-methyltransferase
Which enzyme degrades noradrenaline within the neuron?
MOA
–> Monoamine oxidase
What is the metabolite found in urine of NE released peripherally?
VMA
–> Vanillyl mandelic acid
What is the metabolite found in urine of NE released centrally (in the brain)?
MOPEG
–> 3-methyl-4-hydroxyohenylglycol
Which drug inhibits the synthesis between tyrosine and dopa?
Alpha methyl tyrosine
What is the role of alpha methyl tyrosine?
To inhibit the synthesis of tyrosine to dopa.
How does alpha methyl DOPA prevent the production of NE?
It competes with the enzyme that converts it, resulting in synthesis of alpha-methyl NE. This is a false neurotransmitter, it has very little adrenergic activity. Resulting in less NE release
Which drug inhibits the storage of NE?
Reserpine
What is the role of reserpine?
Blocks the storage of NE, which leads to decreased release of it and resulting in more of it being broken down by MOA.
What drug prevents NE release from neuron?
Guanethidine
What does guanethidine do?
Prevents NT release, decreases sympathetic effects.
Which drugs inhibit NE reuptake from the synapse?
Cocaine, tricyclic antidepressants
What do tricyclic antidepressants and cocaine do to the body?
Inhibit the reuptake of NE.
What drug displaces NE from the vesicle?
Amphetamines and derivatives (Methamphetamines and MDMA)
What do amphetamines and derivatives do to the body?
amphetamines enter the neuron and and bumps NE out of the vesicle. As a result, NE flows out of the vesicle, out of the cell via a pump, and into the synaptic cleft if it is not first broken down by MOA.
As a net effect, NE levels in the synapse increase.
Which drug inhibits the enzymatic breakdown of NE?
MOA inhibitors such as pargyline
What does pargyline do to the body?
It is an MOA inhibitor
Net effect on NE: more stores within vesicles and subsequently released upon stimulation.
What kind of drugs is a beta1 andrenergic agonist?
Dobutamine
What kind of drug is a beta1 adrenergic antagonist?
Metoprolol
