Discussion Board: Unit 2 by

Sympathetic Nervous System

alesayrodriguez — 2022-02-21 20:29:59 UTC

The sympathetic(adrenergic) nervous system is one division of the ANS. It is also known as the Thoracolumbar system. The thoracolumbar system is known for "Fight, Fright, Flight" because it is what regulates our organs and glands when we are in a situation filled with stress whether it be physical or mental causing our "fight or flight" response.

Sympathetic Neurotransmitters

alesayrodriguez — 2022-02-21 20:59:02 UTC

There are four important neurotransmitters in the sympathetic system which are Acetylcholine(ACH), Norepinephrine(NE), Epinephrine(EPI), & Dopamine(DA).
Acetylcholine is a cholinergic neurotransmitter that is released at the ganglia from presynaptic nerve endings. It is present at the ganglia in both the sympathetic and parasympathetic systems.
Norepinephrine is an adrenergic neurotransmitter that is released at the postganglionic nerve endings, also some is released by the adrenal medulla & neurons.
Epinephrine is an adrenergic neurotransmitter that is released by the adrenal medulla.
Dopamine is a neurotransmitter that is important to both the sympathetic and central nervous system.

Receptors of the sympathetic nervous system

alesayrodriguez — 2022-02-22 05:40:32 UTC

The receptors of the sympathetic system are broken into two categories.

Ganglionic receptors:

present on ganglia
nicotinic receptors
activated by acetylcholine

Target receptors:

present on the target organs
activated by norepinephrine or epinephrine

There are four types of target receptors

Alpha-1 receptors:

stimulatory receptors
present on blood vessels, eyes, urinary bladder, kidney, most arteries and veins
activated by either postganglionic neurons or norepinephrine and epinephrine
when activated causes contraction of smooth muscles, which then leads to vasoconstriction, can also cause dilation of pupils

Alpha-2 receptors:

inhibitory receptors
present on nerve terminals
stimulated by norepinephrine and epinephrine
negative feedback system
when activated they decrease contraction of smooth muscles which then leads to vasodilation and decreases/regulates the release of norepinephrine

Beta-1 receptors:

stimulatory receptors
stimulated by norepinephrine and epinephrine, stronger effect from epinephrine
present in the heart
when activated they cause increase in heart rate(+chronotropic), the force of contractions (+inotropic), increase in conduction(+dromotropic)

Beta-2 receptors:

present in smooth muscle, lungs, uterus, skeletal muscle arteries, coronary arteries
stimulated by epinephrine
when activated causes smooth muscle relaxation, bronchodilation, uterine relaxation, relaxation of coronary arteries and skeletal muscles blood vessels-vasodilation

Parasympathetic Nervous System

alesayrodriguez — 2022-02-22 05:51:51 UTC

The parasympathetic(cholinergic) nervous system is another division of the ANS. It is also known as the craniosacral system. It is linked with "rest and digest". This system maintains conserving functions when the body is at rest. It only stimulates one specific body part/system whereas the sympathetic system has a full body response. The chief neurotransmitter of the parasympathetic system is acetylcholine. Acetylcholine is found at the ganglia and the postganglionic nerve endings. The postganglionic neurons are what release the acetylcholine.

Receptors of the parasympathetic system

alesayrodriguez — 2022-02-22 06:17:56 UTC

There are three main types of cholinergic receptors.
Muscarinic:

present on cardiac, smooth muscle, and glands
stimulated by acetylcholine
when activated these receptors decrease heart rate, cause bronchoconstriction, increase digestion, increase urination, increase GI secretion, or cause myosis

Nicotinic 1 (Nn):

present at the ganglia of parasympathetic nerves and sympathetic nerves
stimulated by acetylcholine

Nicotinic 2 (Nm):

present at the neuromuscular junction of skeletal muscle
causes muscular contraction

Sympathetic stimulation effects

alesayrodriguez — 2022-02-22 06:30:52 UTC

When the sympathetic system is stimulated

adrenal medulla releases epinephrine
vasoconstriction of the arteries occurs (excluding coronary arteries and arteries to skeletal muscle)
increase in heart rate, AV conduction
increases contractility
on the respiratory passages, bronchodilation occurs to allow more oxygen to get in
norepinephrine is released from postganglionic neurons
decreased GI motility, secretions
decrease in urination
dilation of the pupil (mydriasis)

Drug classifications

alesayrodriguez — 2022-02-22 06:51:10 UTC

Alpha-1 adrenergic agonists:

vasoconstriction of nasal passages which promotes decongestion
alpha-1 receptor is stimulated

- drugs:

ephedrine
phenylephrine (Neo-Synephrine®)

Adrenergic agonists:

stimulates all alpha and beta receptors
causes vasoconstriction and increases blood pressure due to stimulating alpha-1 receptor
stimulates beta-1 and causes cardiac stimulation
stimulates beta-2 causing bronchodilation

-drugs:

epinephrine(Adrenalin®)

Alpha-1 adrenergic blocking drugs:

binds to alpha-1 receptors and blocks
works against sympathetic system
causes relaxation of smooth muscles
causes vasodilation of blood vessels which then decreases blood pressure
increases urine flow due to the relaxation of the smooth muscle of the ureters

-drugs:

prazosin (Minipress®)
terazosin (Hytrin®)
doxazosin (Cardura®)

Beta-1 adrenergic agonists:

stimulates beta-1 receptors
low doses stimulate d-1 receptors in kidneys which then causes vasodilation and increased renal blood flow
moderate doses stimulate beta-1 receptors in the heart which then increases the force of contraction and the cardiac output
high doses stimulate alpha-1 receptors which then causes vasoconstriction

-drugs:

dobutamine(Dobutamine®)

Beta-2 adrenergic agonists:

stimulates beta-2 receptors
when stimulated it causes relaxation of the smooth muscles of the lungs and the uterus
relaxation of the smooth muscle of the lungs causes bronchodilation

-drugs:

albuterol (Proventil®, Ventolin®)
terbutaline (Brethine®)
formoterol (Foradil®)
salmeterol (Serevent®)

Beta adrenergic blocking drugs

Selective beta-1 blockers:

blocks only the beta-1 receptors
antagonizes norephinephrine and epinephrine at the beta-1 receptors
decreases force of contraction (-inotropic)
decreases cardiac output which also decreases blood pressure
decreases heart rate (-chronotropic)
decreases conduction (-dromotropic)

-drugs:

atenolol (Tenormin®)
metoprolol (Lopressor®)

Non-selective beta blockers:

blocks beta-1 and beta-2 receptors
decreases force of contraction (-inotropic)
decreases cardiac output which also decreases blood pressure
decreases heart rate (-chronotropic)
decreases conduction (-dromotropic)
can cause bronchoconstriction

-drugs:

nadolol (Corgard®)
propanolol (Inderal®)
timolol (Blocadren®)

Drug classifications

alesayrodriguez — 2022-02-22 07:32:20 UTC

Cholinergics/Parasympathomimetics

Direct acting cholinergic agonists:

directly stimulates or binds to muscarinic receptors
mimics acetylcholine

-drugs:

acetylcholine
pilocarpine(Pilocar®)
bethanechol(Urecholine®)

Indirect –acting cholinergic agonists:

inhibits the enzyme acetylcholinesterase which then destroys ACH in the synapse and causes an increase in ACH

-drugs:

neostigmine (Prostigmin®)

Sources

alesayrodriguez — 2022-02-22 07:40:09 UTC

“Beta1 Receptor.” Pathwaymedicine.org, pathwaymedicine.org/beta1-receptor.
“Muscarinic Receptor.” Pathwaymedicine.org, pathwaymedicine.org/Muscarinic-Receptor.
“Sympathetic Nervous System | Function, Definition & Symptoms.” The Human Memory, 11 Oct. 2019, human-memory.net/sympathetic-nervous-system/.
Dalessio, Alice. “Effects of Sympathetic and Parasympathetic Stimulation on Specific Organs - Medical Physiology.” Euroform Healthcare, 28 Apr. 2021, www.euroformhealthcare.biz/medical-physiology/effects-of-sympathetic-and-parasympathetic-stimulation-on-specific-organs.html.