Physiology 3120 Lecture Notes - Autonomic Nervous System, Adrenergic Agonist, Purinergic Receptor

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Published on 26 Nov 2011
Human Physiology
Monday, November 30, 2009
Autonomic Nervous System
Isoproterenol = manufactured adrenergic agonist
Goal of drug companies is to manufacture specific agonists/antagonists to specific receptors and
receptor subtypes
Alpha-adrenergic receptors can be excitatory (vasodilation) or inhibitory (iris dilation, intestinal
Beta-adrenergic receptors can be excitatory (heart acceleration) or inhibitory (bronchodilatation)
Adrenal medulla secretes nor/epinephrine (80% epi; has a greater effect on heart because heart has beta
receptors, which respond to epinephrine much more strongly than norepi)
Anaphylactic shock
2 classic symptoms
Decrease in blood pressure (can lead to breathing)
Bronchial constriction (trouble breathing)
These effects are controlled by beta receptors, which are more responsive to epi, so give epi to
counter anaphylactic shock
Sympathetic/parasympathetic “tone”
Basal rate of neuron discharge (about 1 AP per few seconds; can reach about 20 APs/sec); much
lower “tone” than those of the somatic NS
Allows a single system to increase & decrease activity of stimulated organ
For arterioles, increased discharge causes vasoconstriction, and decreased discharge
causes vasodilation
Enteric nervous system
Arose early in evolution
Two neural plexuses that are contained within the wall of the gut
Has reflex arcs that control gastric motor & secretory activity
Complex activity; multiple behavioural states (i.e. activity is different during eating & fasting)
Can function by itself, but is “tuned up” or regulated by the ANS
Synaptic structure
Some connections resemble the NMJ, but has many varicosities (i.e. think of a snake
who’s eaten a bunch of golf balls) from which transmitters are released
Adrenergic varicosities
NE often associated with ATP; ATP acts on a purinergic receptor, and produces
fast synaptic effects together with adrenergic receptors (hyperpolarization of
smooth muscle)
NE can also be associated with peptides (many identified; same peptides that
occur in the CNS); the peptide acts on second messengers to cause slow synaptic
effects (long-lasting changes in membrane potential [LTP], alter gene expression,
open/close ion channels)
Effector and organ responses to sympathetic and parasympathetic activity
ANS is operating all the time to maintain homeostasis
Sympathetic (fight or flight) Parasympathetic (rest & digest)
Pupils Dilation (need more light) Constrict
Heart rate, BP Increase Decrease
Blood vessels Constriction in most vessels
Dilation in skeletal muscles
Very little effect, if any at all
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