Page 98 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

A. Adrenergic transmission
Activates Adrenal
Inhibits medulla

Epinephrine (E)
L-tyrosine I
Varicosities Bloodstream
1 Transmission

L-dopa β 2 -adrenoceptor
Inactivated 2
(MAO)
4 cAMP
Dopamine Adrenergic
Action potential
Ca 2+ PKA
7 NE NE 6d
α 2 -adrenoceptor 3 α 2 -adreno-
ceptor Plate 3.5
Heart, glands,
smooth muscle 6c
5
6b
Inactivated: Re-
absorption
by MAO
by COMT Norepinephrine
(NE) Epinephrine
Capillary
6a
Diffusion into blood
(raises NE in blood)
α- β-
adrenoceptors adrenoceptors
α 1 α 2 β 1 β 2

!
tein kinase A (PKA), which phosphorylates probability of voltage-gated Ca 2+ channels in
different proteins, depending on the target cell the heart. In the kidney, the basal renin secre-
type (! p. 274). tion is increased via ! 1-adrenoceptors.
NE and E work via " 1-adrenoceptors (! B3) Activation of " 2-adrenoceptors by epineph-
to open L-type Ca 2+ channels in cardiac cell rine (! B4) increases cAMP levels, thereby
2+
membranes. This increases the [Ca ] i and lowering the [Ca ] i (by a still unclear mecha-
2+
therefore produces positive chronotropic, dro- nism). This dilates the bronchioles and blood
!
motropic, and inotropic effects. Activated G s vessels of skeletal muscles and relaxes the
protein can also directly increase the open- muscles of the uterus, deferent duct, and 85
!
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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