[041] ESR: Catecholamines

Question 1

Answer 1

Question 2

Answer 2

Question 3

Compare between the importance of Catecholamine uptake and metabolism in terminating it’s actions

Answer 3

N.B.: Uptake is more important than metabolism in terminating the actions of catecholamines

Question 4

Adrenaline and noradrenaline concentrations are controlled by……

Answer 4

post-ganglionic endocytosis

Question 5

Polarity of Catecholamines ?

Answer 5

Catecholamines are hydrophilic and thus they interact with plasma membrane receptors

Question 6

Answer 6

Question 7

Effect of continuous exposure to stimulating ligand on G Protein Coupled Receptor ?

Answer 7

Desensitization = failure of signaling pathway to respond to stimulus despite continued presence of receptors at cell surface

Question 8

Answer 8

Question 9

….. adrenoceptors when activated, generally produce excitatory responses of smooth muscle

Answer 9

Alpha adrenoceptors

Question 10

….. when activated, generally produce inhibitory responses of smooth muscle in which they are located

Answer 10

Beta receptors

Question 11

Which Alpha Adrenoreceptors are pre/post synaptic ?

Answer 11

• alpha-1 receptors are mainly postsynaptic (on target organ cells)

• alpha-2 receptors are found mainly presynaptically (before the target cells) on sympathetic postganglionic nerve terminals

Question 12

The major antihypertensive action of selective alpha-2 agonists such as clonidine, probably occurs as a result of …..

Answer 12

agonism of alpha-2 receptors in the CNS

Question 13

Clonidine mechanism of action ?

Answer 13

• Clonidine treats high blood pressure by stimulating presynaptic alpha-2, decreasing presynaptic calcium levels, thus inhibiting the release of norepinephrine in the brainstem vasomotor center, decreasing sympathetic tone and peripheral vascular resistance, lowering blood pressure

Question 14

Difference between Beta 1/2 and 3 Adrenoreceptors ?

Answer 14

• Beta-1produce cardiac positive chronotropic and inotropic responses and lipolysis

• Beta-2 receptors, when activated, produce bronchodilation, vasodilation, and uterine relaxation

• Beta-3 receptors produce lipolysis in adipose tissue

Question 15

Selective Beta-2 agonists are useful in the treatment of……

Answer 15

asthma

Question 16

Effect of Adrenaline on mean BP ?

Answer 16

• Adrenaline only increases systolic BP and reduces diastolic BP (hence no change in mean BP)

Question 17

….(hormone) decreases gut motility and can act as a bronchodilator

Answer 17

Adrenaline

Question 18

Effects of Epinephrine on gut motility ?

Answer 18

Adrenaline decreases gut motility and can act as a bronchodilator

Question 19

Effect of Noradrenaline on BP ?

Answer 19

• Noradrenaline increases both systolic and diastolic BP (so increasing mean BP)

Question 20

Effects of noradrenaline on bronchial tone ?

Answer 20

• Effects of noradrenaline on gut motility are less marked and no effect on bronchial tone

Question 21

Both the direct (receptor-mediated) and indirect effects (changes in hormone secretion, heart rate,..) of catecholamines (mainly adrenaline) on carbohydrate metabolism lead to a……

Answer 21

prompt and sustained rise in plasma glucose (initially glycogenolysis, then gluconeogenesis)

Question 22

How does catecholamine enhance glycogen breakdown ?

Answer 22

• On binding Beta adrenoceptors on the plasma membrane of hepatocytes, catecholamines stimulate adenylyl cyclase to phosphorylate, phosphorylase kinase (activate) and glycogen synthetase (inhibit); enhancing glycogen breakdown

Question 23

How can catecholamine inhibit insulin secretion ?

Answer 23

• Inhibition of insulin secretion is mediated by Alpha-2 adrenoceptors on the Beta cells of the pancreas, therefore reducing insulin mediated glucose disposal (IMGD) in skeletal muscle

Question 24

Answer 24

Question 25

need to replace adrenaline After adrenalectomy or destruction of
medulla ?

Answer 25

After adrenalectomy / destruction of medulla, no need to replace adrenaline corticosteroid replacement is sufficient

Question 26

Hypersecretion of adrenaline results in :

Answer 26

• hypertension and hyperglycaemia

• (+ insulin resistance)

Question 27

The usual causeo of Adrenomedullary Hyperfunction ?

Answer 27

• Usually due to pheochromacytoma

Question 28

Define Multiple Endocrine Neoplasia (MEN)2

Answer 28

an inherited disorder of endocrine glands of same embryonic origin (possible thyroid, parathyroid and adrenal) associated with cancerous and non-cancerous tumors

Question 29

How to diagnose Adrenomedullary Hyperfunction ?

Answer 29

Question 30

Treating Pheochromocytoma ?

Answer 30