Viagra NO emission toxic -> nitric acid, react w ozone. Nitrous = N²O laughing gas, greenhouse.
local_signaling Epidermal growth factor by submandibular gland, parotid gland, Salivary EGF. Para: beside, near.
long-distance_signaling Exocrine: into ducts: tear salivary, mammary.
ion_channels Facilitated diffusion diff: ligand and ions.
G-protein Epinephrine as signal.
phosphorylation_cascade Phosphatases off.
nuclear Transcription factor mentioned in 11&E
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11&E Build Signaling Pathway - skip 2 iP3; 3 needs 3 (transcript factor); 4 needs 6 (protein kinase); 5 needs 3.

0. leukocytes. Helper T cells stimulate B cells (bone marrow) make antibodies (Immunoglobulins), and help killer T cells develop.
   Cytotoxic (killer) T (bone marrow, mature in thymus) cells recognize surface markers on own cells for destruction: virus-infected or tumor.
1. Paracrine: growth factor: protein, repair damaged tissue, scar tissue formation, clotting.
2. Dopamine sympathetic nervous system, increased heart rate/blood pressure; cannot cross the blood-brain barrier: synthetic precursor L-DOPA for Parkinson's disease. Pleasure cocaine, amphetamines.
3. Serotonin sleep, appetite.
4. Progesterone made by corpus luteum in ovary and placenta, induces development of endometrium of uterus and mammary glands.
5. G-protein GTP-binding regulatory protein, is a kinase;
6. Kinase: from Greek knein, to move: an enzyme -> transfer phosphate group (from ATP to tyrosine)
7. Ligand-gated ion channels: neurotransmitters (acetylcholine) Action potential: voltage-gated channel rathern than ligand-gated?
8. Active transport animation.
9. Viagra inhibits hydrolysis of cGMP to GMP, prolonging the vasodilation effect of Nitric oxide (NO), prescribed for chest pains.