Morphine Mechanism of Action Quiz

Mechanism of Action (MOA)

• Morphine binds to three types of opioid receptors: μ (mu), κ (kappa), and δ (delta) in both the central nervous system (CNS) and peripheral nervous system (PNS).
• It activates G-protein coupled receptors, initiating a signaling cascade that affects neuronal activity.
• Inhibition of adenylate cyclase occurs, leading to decreased production of cAMP, which lowers neuronal excitability.
• Morphine closes calcium channels, resulting in decreased release of neurotransmitters, which diminishes pain transmission.
• It opens potassium channels, hyperpolarizing neurons and further reducing their excitability.

Effects on Body Organs

Central Nervous System (CNS)

• Provides analgesia, offering effective pain relief.
• Induces sedation, leading to decreased alertness.
• Produces feelings of euphoria, which can contribute to misuse.
• Causes respiratory depression, significantly slowing the breathing rate.

Respiratory System

• Morphine reduces respiratory rate, risking hypoventilation.
• Breathing becomes shallow, impacting gas exchange efficiency.

Gastrointestinal System

• Lowers gut motility, resulting in constipation which is a common side effect.

Cardiovascular System

• Can lead to decreased heart rate, potentially resulting in bradycardia.
• Causes decreased blood pressure, which may contribute to dizziness.

Urinary System

• Promotes urinary retention, making it difficult to urinate.

Endocrine System

• Reduces secretion of hormones such as insulin and antidiuretic hormone (ADH), affecting metabolism and fluid balance.

Additional Effects

• Histamine release can occur, causing itching, flushing of the skin, and possible hypotension.
• Chronic use can result in physical dependence and tolerance, requiring higher doses for the same analgesic effect.