Question

In signaling through the β-adrenergic receptor the same hormone can have different effects on difference cells. Explain what happens to each of the following and what last signaling step is common to all (2 pts each):

A. Heart

B. Skeletal Muscle

C. Smooth muscle

Please no cursive handwritting, I cant read cursive.

Answer 1

ANSWER

• β-Adrenergic receptors are a class of G protein-coupled receptors that act on catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline)
• it mediates critical sympathetic responses in the central nervous system, pulmonary, cardiovascular, and metabolic system.
• β-adrenergic receptors have different effects on FOLLOWING different cells.
• A) HEART;-

- Signaling through the β-adrenergic receptor are a beneficial mechanism that protects the heart from the detrimental effects of chronic β-receptor stimulation, including arrhythmias, energy dysbalance, hypertrophy, and apoptosis

-Signaling by cardiac β-receptors undergoes a classical common pathway by the activation of adenylyl cyclases via GS follows increased cAMP levels.

-The primary target for cAMP is protein kinase A, which phosphorylates several proteins that are essential for cardiac function: L-type calcium channels.

-This affects cardiomyocyte contractile behavior by increasing Ca²⁺ influx increasing Ca²⁺reuptake into the sarcoplasmic reticulum and modulating myofilament Ca²⁺ sensitivity

-Another target of cAMP are cAMP-gated HCN pacemaker channels.

B. Skeletal Muscle

• Stimulation of β-Adrenergic receptors on muscle cells induces glucose uptake. ie, β-Adrenergic receptors induce glucose uptake via the glucose transporter protein GLUT4, which is known to be regulated by insulin.
• β-Adrenergic receptors signalling leads to inhibition of myosin II-dependent contractility in skeletal muscle cells.

C. Smooth muscle

• The β-Adrenergic receptors is a G(s)-protein-coupled receptor and β-Adrenergic receptors activation increase smooth muscle cAMP.
• A substantial role for a cAMP-dependent mechanism(s) is generally a key trigger for eliciting β-Adrenergic receptors-mediated relaxation of smooth muscle.