G-Protein-Linked 2nd Messengers & Their Actions

Question 1

Alpha-1 R

Answer 1

• SNS
• Class: q
• Adren-Rs Differential Responses to Catechols: EPI vs NE
  
  • NE=EPI in regards to potency
  • BUT are less sensitive to circulating catechols b/c concentration is too low (vs Beta-Rs) SO, Alpha-1 Rs are only activ by innervations, which is by postganglionic symp neurons (vs adrenals)
• Located in:
  
  • Vascular sm msc of–skin, skeletal msc, & splanchinc/gut region
• Major fnxs:
  
  • Increase:
    
    • Vascular sm msc contraction
    • Pupillary dilator msc contraction (mydriasis=dilated)
    • Intestinal & bladder spincter msc contraction

Question 2

Alpha-2 R

Answer 2

• SNS
• Class: i
• Adreno-Rs Differential Responses to Catechols: EPI vs NE
  
  • EPI more potent (vs NE)
  • SO, Alpha-2 Rs are activ by release of NE from postganglionic symp neurons OR EPI/NE release from adrenal medulla (Controlled by both innervation & adrenal medulla, ~ Beta-1 Rs)
• Located in:
  
  • Wall of GI tract (where else?)
• Major fnxs:
  
  • Decrease:
    
    • SNS outflow
    • Insulin release
    • Lipolysis
  • Increase:
    
    • Platelet aggregation

Question 3

Beta-1 R

Answer 3

• SNS
• Class: s
• Adreo-Rs Differential Responses to Catechols: EPI vs NE
  
  • NE=EPI in potency
  • BUT Beta-1 Rs are more sensitive to EPI/NE (vs Alpha-1 Rs), SO Beta-1 Rs are excited by release of NE from post-ganglionic symp neurons & EPI/NE from adrenal medull (Controlled by both innervation & adrenal medulla, ~ Alpha-2Rs)
• Located in:
  
  • SA, AV node & Ventricular myocardium
  • Salivary glands, adipose, & kidney
• Major fnxs:
  
  • Increase:
    
    • HR
    • Contractility
    • Renin release (to increase blood volume)
    • Lipolysis
    • Increase salivation

Question 4

Beta-2 R

Answer 4

• SNS
• Class: s
• Adreo-Rs Differential Responses to Catechols: EPI vs NE
  
  • EPI more potent (vs NE)
  • Beta-2 Rs are NOT innervated, SO Beta-2 Rs are ONLY excited by EPI from adrenal medulla
  • Fight-or Flight Response–Activation via Beta-2 Rs–> overwhelm Alpha-1 Rs–> Relaxation of vascular smooth msc
• Located in:
  
  • Vascular smooth msc of–skeletal msc
  • Wall of GI tract & bladder
  • Bronchioles
• Major fnxs (Relax sm msc vs Alpha-1 Rs):
  
  • Vasodilation
  • Bronchodilation
  • Ciliary msc relaxation (=far vision)
  • Increases:
    
    • HR
    • Contractility
    • Lipolysis
    • Insulin release
    • Aqueous humor production
  • Decreases:
    
    • Uterine tone (tocolysis=inhib contractions)

Question 5

M1-R

Answer 5

• PNS
• Protein class: q
• Major fnxs: CNS, ENS

Question 6

M2-R

Answer 6

• PNS
• Protein class: i
• Major fnxs: Decrease HR & contractility of atria

Question 7

M3-R

Answer 7

• PNS
• Protein class: q
• Major fnxs:
  
  • Bronchoconstriction
  • Ciliary msc contraction (accomodation–for near vision)
  • Increases:
    
    • Exocrine gland secretion (e.g. gastric & lacrimal)
    • Gut peristalsis
    • Bladder contraction
    • Pupillary sphincter msc contraction (miosis vs dilated=mydriasis)

Question 8

D1-R

Answer 8

• Protein class: s
• Major fnxs: Relaxes renal vascular sm msc

Question 9

D2-R

Answer 9

• Protein class: i
• Major fnxs: Modulates transmitter release, esp in brain

Question 10

H1-R

Answer 10

• Protein class: q
• Major fnxs: Increases nasal & bronchial mucous production, Contraction of bronchioles, Pruritus, & Pain

Question 11

H2-R

Answer 11

• Protein class: s
• Major fnx: Increase gastric acid production

Question 12

V1-R

Answer 12

• Protein class: q
• Major fnxs: Increase vascular smooth msc contraction

Question 13

V2-R

Answer 13

• Protein class: s
• Major fnxs: Increase H2O permeability & reabsorption in collecting tubules of kidney (V2 is found in the 2 kidneys)