week 4-Autonomic Nervous System Flashcards
SNS-sympathetic
Neurotransmitters are epinephrine, norepinephrine and dopamine
Receptors are alpha 1 and alpha 2, beta 1 and beta 2, and dopaminergic receptors
Fight of flight
PSNS-parasympathetic
Neurotransmitter is acetylcholine (Ach)
Receptors are centrally located nicotinic and peripherally located muscarinic
Rest and digest
sns + psns =
ans
adrenergics
large group of both exogenous (synthetic) and endogenous (naturally occurring) substances.
they also stim the SNS
catecholamines
substances that can produce a sympathic response
Adrenergic Agents: Definition
Drugs that stimulate the sympathetic nervous system (SNS)
Referred to as “fight or flight response”
Also known as:
Adrenergic agonists
Sympathomimetics
Catecholamines
Mimic the effects of the SNS neurotransmitters:
norepinephrine (NE)
epinephrine (EPI)
dopamine
Direct-Acting: Designed to stimulate & act like a neurotransmitter (bind to receptor sites and creates a response)
Non catecholamine adrenergic drugs
ie. Phenylephrine, salbutamol
Adrenergic receptors (receptor sites for catecholamine norepi and epi)
are located throughout the body where adrenergic drugs bind and produce the desired effect.
Are receptors for the sympathetic neurotransmitters
Adrenergic receptors are divided into two
–alpha-adrenergic and beta adrenergic receptors
Subdivided into alpha 1 & 2 and beta 1 & 2
Alpha-adrenergic receptors:
respond to NE
Beta-adrenergic receptors:
respond to EPI***
Dopaminergic receptors:
respond to dopamine
Alpha 1 located on post synaptic effector cells
(on the muscle or organ that the nerve stimulates)
located on post synaptic effector cells
Alpha 2 located
on pre- and post-synaptic nerve terminal (sympatholytic effects)
Predominant Alpha-Adrenergic Agonist Responses
Vasoconstriction
CNS stimulation
Beta-Adrenergic Receptors are located
on postsynaptic effector cells
Beta1-adrenergic receptors —
located primarily in the heart resulting in cardiac stimulation
Beta2-adrenergic receptors —
located in smooth muscle of the bronchioles, arterioles, and visceral organs resulting in bronchial, GI and uterine smooth muscle relaxation (dilation)
Dopaminergic Receptors
An additional adrenergic receptor
Stimulated by dopamine
Causes dilation of the following blood vessels, resulting in increased blood flow Renal Mesenteric Coronary Cerebral
Indirect-acting sympathomimetic
Causes the release of catecholamine from the storage sites (vesicles) in the nerve endings
The catecholamine then binds to the receptors and causes a physiological response
ie. amphetamines
Mixed-acting sympathomimetic
Mixed-acting sympathomimetic
Directly stimulates the receptor by binding to it
and
Indirectly stimulates the receptor by causing the release of stored neurotransmitters from the vesicles in the nerve endings
ie. ephedrine
Responses to Stimulation
Location/ Receptor/ Response
Cardiovascular:
Blood vessels- alpha1 and beta2 / Constriction/dilation
Cardiac muscle/ beta1 / Increased contractility
AV Node beta1 / Increased / heart rate
SA Node beta1 / Increased / heart rate
Gastrointestinal:
Muscle/beta2 / Decreased motility
Sphincters/ alpha1 / Constriction
Genitourinary:
Bladder / alpha1 / Constrictionsphincter
Penis/ alpha1/ Ejaculation
Uterus / alpha1 and beta2 / Contraction/relaxation
Bronchial / beta2 / Dilation/relaxationmuscles
Alpha Adrenergic Drug Effects
Stimulation of alpha-adrenergic receptors on smooth muscles results in:
Vasoconstriction of blood vessels (used to increase BP)
Relaxation of GI smooth muscles
Contraction of the uterus and bladder
Male ejaculation
Decreased insulin release
Contraction of the ciliary muscles of the eye
(dilated pupils)
Adrenergic drugs
drugs stay in the synaptic cleft where they induce a response
Direct Acting – (Adrenergic drugs)
bind directly to the receptor ie epinephrine
Used for glaucoma, shock due to trauma
Do not use in toes, finger or nose due to the vasoconstriction effects