Study Set Content:
TERMINUS.ADRENERGIC RECEPTORS (ADRENOCEPTORS):
• Alpha (0)-0,0
• Beta (B)-B: B,B
are coupled via G proteins in the Gq family to phospholipase C.
Alpha 1 receptor
This enzyme hydrolyzes (blank)
leading to the formation of (blank) and (blank). IP, promotes the release of sequestered (blank) from intracellular stores, which increases the cytoplasmic concentration of free(blank) and the activation of various calcium-dependent protein kinases
polyphosphoinositides, inositol 1,4,5 trisphosphates (IP,), diacylglycerol (DAG), Ca 2+
Activation of these receptors may also increase____ across the cell's plasma membrane
influx of calcium
inhibit adenylyl cyclase activity and cause intracellular cyclic adenosine monophosphate (CAMP) levels to decrease.
Alpha 2 receptors
Alpha 2 -receptor-mediated inhibition of adenylyl cyclase activity is transduced by the inhibitory regulatory protein, (blank). It is likely that not only a, but also the B-y subunits of Gi contribute to inhibition of adenylyl cyclase.
Gi
Activation of all three receptor subtypes: ____results in stimulation of adenylyl cyclase and increased conversion of adenosine triphosphate (ATP) to CAMP
(B1, B2, and B.)
In the heart B-receptor-activated CAMP synthesis (blank) the reflux of calcium across the cell membrane and its sequestration inside the cell.
increases
Activation of the cyclase enzyme is mediated by the
stimulatory coupling protein Gs.
is the major second messenger of B-receptor activation.
Cyclic AMP
Beta-receptor activation also promotes the
relaxation of smooth muscle
Beta adrenoreceptors may activate ____ in the heart via Gs-mediated enhancement independently by changes in CAMP concentration
voltage-sensitive calcium channels
is a low affinity receptor compared with B, and B2 receptors but is more resistant to desensitization.
B, adrenoreceptor
The D1 receptor is typically associated with the
stimulation of adenylyl cyclase
have been found to inhibit adenylyl. Cyclase activity, open potassium channels and decrease calcium influx.
D2 receptors
Responses mediated by adrenoceptors are not
fixed and static.
The number and function of adrenoceptors on the cell surface and their responses may be regulated by (blank) themselves, other hormones and drugs, age, and a number of disease states.
catecholamines
One of the best-studied examples of receptor regulation is the ____ that may occur after exposure to catecholamines and other sympathomimetic drugs.
desensitization of adrenoceptors
After a cell or tissue has been exposed for a period of time to an
agonist, that tissue often becomes____ to further stimulation by that agent.
less responsive
Other terms such as ____ have also been used to denote desensitization.
tolerance, refractoriness, and tachyphylaxis
