There are multiple types of receptors for epinephrine. The heart has beta 1 (1)

Question

There are multiple types of receptors for epinephrine. The heart has beta 1 (1) receptors, and the lungs have beta 2 (2) receptors. When epinephrine binds to receptors in the heart, it increases heart rate; when epinephrine binds to receptors in the lungs, it causes relaxation.

35) In patients with hyperthyroidism (thyrotoxicosis), thyroid hormone levels are higher than normal. Thyroid hormone excess upregulates expression and function of 1 receptors in different tissues including heart (among other effects). What effect would upregulation of 1 receptors have? (2 points)

a) constrict bronchioles

b) dilate bronchioles

c) decrease heart rate

d) increase heart rate

Explanation / Answer

d) increases heart rate

Due to upregulation of B1 receptors the number and activity of the receptors is increased thus more epinephrine molecules bind to the receptor thus increasing heart rate.

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