The Autonomic Nervous System Flashcards
Regulates the function of smooth muscle and cardiac muscle and also controls some aspects of metabolism
-involuntary
Autonomic Nervous System (ANS)
The ANS is centrally regulated by nuclei in the
Medulla, Pons, Hypothalamus, and Spinal cord
Some examples of tissues that are modulated by the ANS include
Cardiovascular, renal, GI, and Endocrine
Afferent tracts that affect the ANS are classified as
- ) Visceral afferents
- ) Somatic Afferents
- ) Central chemo afferents
- ) Cognitive components of CNS
Information regarding anger, arousal, stress, etc
Cognitive components of the CNS
Designed for coping with acute challenges such as elevations in heart rate and blood pressure
Sympathetic nervous system (SNS)
Very active during resting conditions and chronically regulates metabolism and cardiovascular function
Parasympathetic nervous system (PSNS)
Upregulated to help counteract elevated SNS activity
-more localized in its action than the SNS
PSNS
The sympathetic chain is a series of ganglia located on either side of the vertebral column. What type of neurons are preganglionic SNS neurons?
Cholinergic fibers (i.e. ACh is their primary neurotransmitter)
Dendrites and cell bodies of the post-ganglionic SNS fibers express ACh receptors, and these post-ganglionic cholinergic nreceptors can also bind
Nicotine
Dendrites and Cell bodies of Post ganglionic SNS fibers have receptors that are thus identified as
Cholinergic-nicotinic (N2) receptors
When choinergic-nicotinic receptors are bound to ACh or nicotine, they are activated and allow
Inward Na+ or Ca2+ current
Branching of the axons of pre- and post-ganglionic fibers explains, in part, the diffuse action of the
SNS
Post-ganglionic SNS fibers are considered to be
Noradrenergic (use norepinephrine as primary neurotransmitter)
Cell plasma membranes of effector tissues that are innervated by the SNS fibers express
Adrenergic receptors
Adrenergic receptors (adrenoceptors) are grossly classified as type α and β. These receptor families are subclassified as type
α1, α2, β1, β2, and β3
The specific complement of receptor isoforms determines specificity of the response to
Adrenergic stimulation
Adrenoreceptors belong to the family of
G-protein coupled receptors
Can mobilize phospholipase C, and in turn ligand-gated Ca2+ channels can be activated
α1 adrenoreceptors
Binding of adrenergics to α1 receptors in smooth muscle results in what 5 things?
- ) activation of Gi proteins
- ) Decrease in cGMP and cAMP production
- ) Opening of membrane Ca2+ channels
- ) Increase in sarcoplasmic [Ca2+]
- ) Vasoconstriction
Often associated with inhibitory effects on GI smooth
muscle contractility, inhibition of some glandular secretions, and inhibition of neurotransmitter
secretion
Activation of α2 adrenoreceptors
Located on the prejunctional membrane of some post-ganglionic SNS fibers (e.g., cardiovascular)
α2 receptors
When activated by adrenergics, these α2 receptors are involved in
Down regulating neurotransmitter release (negative feedback)
Closely associated with stimulating Gs protein/cAMP signaling
β1 and β2 adrenoreceptors
Predominant in the heart
β1 receptors
Also expressed within the heart and couple to both stimulatory (Gs) and inhibitory (Gi) signaling motifs
-also found in many smooth muscle beds
β2 receptors
In the heart, the activation of β1 and β2 receptors results in increased
Heart rate (chronotropy) and cardiac contractility (inotropy)
Also couple to Gi protein-mediated pathways which induce negative inotropy
Cardiac β2 receptors
Associated with the relaxation of smooth muscle, hepatic glycogen metabolism, and glycogenolysis in skeletal muscle
β2 receptors
In the kidney, activation of β1 receptors stimulates
Renin secretion from JG cells
Synthesized in the axon termini of SNS post ganglionic neurons
Norepinephrine
What are the steps of norepinephrine synthesis?
Tyrosine —> L-dopa —>Dopamine —> Norepinephrine
Dopamine is converted to norepinephrine by
Dopamine β-hydroxylase
Norepinephrine can be converted to epinephrine by
Phenolethaolamine N-methyltransferase
A catcholamine that acts through two receptor isoforms
Dopamine
Expressed within the vascular smooth muscle beds of the cerebral, renal, coronary and mesenteric circulations
Type 1 dopamine receptor (DA1)