Topic 84 - Catecholamines

Question 1

Words to include general

Answer 1

• Adrenal medulla
• Granules
  
  • Chromogranin
  • ATP
  • EC space
  • Exocytosis
• Alpha receptors
• Beta receptors
• Sympathetic-adrenal system
• Physical output
• Epinephrine / adrenaline
  
  • Muscular activity
  • Cold
  • Blood pressure (↓)
• Norepinephrine / noradrenaline
  
  • Hypoxia
  • Pain
  • Anxiety

Question 2

Words to include in synthesis of catecholamines

Answer 2

• Precursors
• Granules
• Antiport protein
• Hydrogen concentration gradient
  
  • ATPase pump
• DBH (Dopamine-Beta-Hydroxylase)
  
  • Granular norepinephrine
• Cytoplasm
• PNMT (Phenylethanolamine-ortho-methyltransferase)
• Chromogranin
• Peptides
  
  • Somatostatin
  • Enkephalin
  • NPY (neuropeptide Y)
• Adrenal gland
• Sympathetic terminals
• Sympathetic effects
• Peptidergic co-transmission
• Phenylalanine
  
  • Phe-hydroxylase
• Tyrosine
  
  • Thy-hydroxylase
• DOPA
  
  • Decarboxylase
• Dopamine
  
  • Dopamine-beta hydroxylase DBH
• Norepinephrine
  
  • Phenylethanolamine-ortho-methyltransferase PNMT
• Epinephrine
• DBH
  
  • Granules
• PNMT
  
  • Cytoplasm
• Amine precursor
• H⁺ ATPase

Question 3

Words to include in inactivation of hormones

Answer 3

• Degradation
  
  • MAO (monoamine oxidase)
    
    • Mitochondria
  • COMT (Cathecholamine-O-methyltranspherase)
    
    • Cytoplasm
  • Plasma metabolites
• Inactivation - reuptake
• Presynaptic alpha-receptors
  
  • Alpha-2 receptor
  • Reuptake
• Postsynaptic alpha-receptors
  
  • Alpha-1 receptor
  • Electrical effect
  • Metabolic effect

Question 4

Words to include in receptors

Answer 4

• IC signaling
  
  • Catecholamine receptors
  • G protein dependent cAMP system
• General effects
  
  • Alpha receptor effects
    
    • Alpha-1
      
      • Smooth muscle contraction
      • Glycogenolysis
      • Sympathetic synaptic transduction
      • PLC
    • Alpha-2
      
      • CNS
      • AC
  • Beta receptor effects
    
    • Beta-1
      
      • Heart
      • Adipose cells
      • AC
    • Beta-2
      
      • Smooth muscle relaxation
      • Metabolism (↑)
      • AC
• Circulation effects
  
  • Sympathetic nervous system
  • sympathetic activation
  • Vasoconstriction
  • BP (Binding Protein)
• Intermediary metabolism effects
  
  • Oxygen consumptrion (BMR) (↑)
    
    • Hepatic glygogenolysis
    • Respiration requency
    • Calorigenic effect
  • Cardiac output (↑)
  • Respiration (↑)
  • Carbohydrate metabolism
    
    • Blood glucose
  • Lipid metabolism
    
    • Free fatty acid (↑)

Question 5

Words to incude in alarm reaction

Answer 5

• “Fight or flight” reflex
• Adrenal medulla
• Cannon’s reaction / “alarm reaction#

Question 6

Words to include in regulation of adrenal cortex

Answer 6

• Sympathetic nervous system
  
  • Indirectly
  • Directily
• Hypoglycemia
  
  • Direct stimulus
• Alarm reaction
• Receptor regulation
  
  • Complex

Question 7

What are cathecholamines?

Answer 7

• Hormones of the adrenal medulla
  
  • ​Epinephrine / adrenaline
  • Norepinephrine / noradrenaline

​

• Synthesized hormone molecules are stored in granules
  
  • Contain chromogranin and ATP

​

• Act on alpha and beta receptors

Question 8

General about epinephrine / adrenaline

Answer 8

• Hormone of fighting
• Produced by effects of:
  
  • Muscle activity
  • Cold
  • Decreased blood pressure

Question 9

General about norepinephrine / noradrenaline

Answer 9

• Hormone of aggressive behavior
• Produced by effects of:
  
  • Hypoxia
  • Pain
  • Emotional anxiety

Question 10

Synthesis of catecholamines

Steps

Answer 10

1. Precursors enter the granules by an antiport protein
   
   • The antiport protein utilizes a hydrogen concentration gradient maintained by ATPase pump
2. DBH (Dopamine-Beta-Hydroxylase) is present in the granules
   
   • Results in granular norepinephrine
3. Released into the cytoplasm and converted to epinephrine
4. Norepinephrine and epinephrine are stored in granules until liberation
   
   • Chromagranin stores the final products:
     
     • Epinephrine
     • Norepinephrine
     • Peptides:
       
       • Somatosin
       • Enkephalin
       • NPY (Neuropeptide Y)
5. These modulators are released from adrenal gland and influence sympathetic effects
   
   • Called peptidergic co-transmission

Question 11

Inactivation of hormones

Answer 11

• Suspension of hormonal effects is made possible by:
  
  • Degradation of hormones
    
    • MAO (monoamine oxidase)
      
      • Mitochondria
    • COMT (catecholamine-O-methyltranspherase)
      
      • Cytoplasm
    • Plasma metabolites
  • Reuptake of hormones liberated by neurons

Figure: inactivation-reuptake

Question 12

What does catecholamine exerts their effects on?

Answer 12

• Alpha-1 and alpha-2 receptors
• Beta-1 and beta-2 receptors
• Circulation
• Smooth muscles
• Intermediary metabolism
• Different organs

Question 13

Receptors

Which receptors does epinephrine and norepinephrine act on?

Answer 13

• Norepinephrine stimulates mainly:
  
  • Alpha-1 receptors
  • Beta-1 receptors
• Epinephrine stimulates mainly:
  
  • Beta-2 receptors
  • Alpha-1 receptors

Question 14

Receptor

IC signaling - How does catecholamine receptors exert effect

Answer 14

Catecholamine receptors exert effect by G protein dependent cAMP system

Question 15

Receptors

General effect of catecholamines on alpha receptor

Answer 15

• Alpha-1 receptor
  
  • Smooth muscle contraction
  • Glycogenolysis
  • Sympathetic synaptic transduction
• Alpha-2 receptor
  
  • Regulation of transmitter release in the CNS

Question 16

Receptors

General effect of catecholamines on beta receptor

Answer 16

• Beta-1 receptor
  
  • Stimulation of the heart
  • Stimulation of adipose cells
• Beta-2 receptor
  
  • Smooth muscle relaxation
  • Increase of metabolism

Question 17

Receptors

Effects of catecholamines on circulation

Answer 17

• Similar to effects of sympathetic nervous system
  
  • Sympathetic activation
• Low epinephrine
  
  • Beta effect
  • Cardiac output ↑
• High epinephrine
  
  • Alpha effect
  • Vasoconstriction
  • Binding protein ↑
• High norepinephrine
  
  • Similar to high epinephrine
• Effect depends on plasma concentration of hormone, receptor types and ratio of receptor types

Question 18

Receptors

Effects of catecholamines on intermediary metabolism

Answer 18

• General metabolic effect:
  
  • Oxygen consumption (BMR) ↑
  • Cardiac output increases ↑
  • Respiration increases ↑
• Mobilize rapidly utilizable energy sources
• Increase BMR and O₂ consumption
  
  • Facilitation of hepatic glycogenolysis
  • Respiration frequency ↑
  • Performance of heart ↑
  • Calorigenic effect
• Carbohydrate metabolism
  
  • Blood glucose ↑
    
    • Initiates glycogenolysis in liver and muscle cells
    • Shifts carbohydrate stores from liver (center) to muscle (periphery)
• Lipid metabolism
  
  • Free fatty acids levels ↑
  • Beta receptor effect dominates in adipose tissue
  • Utilization of fat in adipose ↑

Question 19

Receptors

Effects of catecholamines on particular organs

Answer 19

Question 20

Alarm reaction

Answer 20

• “Fight or flight” reflex
• Adrenal medulla has an important role in the formation of the “alarm-reaction” (Cannon’s reaction) during stress
• Enables rapid utilization of high amount of energy

Question 21

Regulation of the adrenal cortex

Answer 21

• Adrenal gland controlled by sympathetic nervous system
  
  • Indirectly
  • Directly
• Hypoglycemia
  
  • Direct stimulus
• Alarm reaction
  
  • Secretion of catecholamines release of large amount of energy
• Receptor regulation
  
  • Complex
• Norepinephrine
  
  • Hormone of aggressive behavior
  • Produced by effects of:
    
    • Hypoxia
    • Pain
    • Emotional anxiety
• Epinephrine
  
  • ​Hormone of fighting​
  • Produced by the effects of:
    
    • Muscle activity
    • Cold
    • Drop of blood pressure