Anatomy - Mechanisms of Smooth Muscle Contraction

The video explains the unique mechanisms of smooth muscle contraction, contrasting it with skeletal and cardiac muscles. It details three activation methods: stretch channels, catecholamines, and antidiuretic hormone, each leading to different second messengers. These messengers trigger calcium release from the sarcoplasmic reticulum, which binds to calmodulin, activating myosin light chain kinase. This process results in phosphorylation of myosin, enabling cross-bridge formation with actin, leading to contraction.

Which type of muscle is primarily responsible for regulating the diameter of tubes in the body?

• Skeletal muscle

• Cardiac muscle

• Striated muscle

• Smooth muscle

What is the first method by which smooth muscle contraction can be induced?

• Voltage-gated sodium channels

• Chemical signals

• Electrical impulses

• Stretch channels

Which hormone is involved in the second method of smooth muscle activation?

• Insulin

• Thyroxine

• Epinephrine

• Glucagon

What is the role of cyclic AMP in smooth muscle contraction?

• It binds directly to actin

• It triggers calcium release from the sarcoplasmic reticulum

• It inhibits myosin light chain kinase

• It deactivates calmodulin

In smooth muscle, what does calcium bind to in order to activate contraction?

• Troponin

• Calmodulin

• Actin

• Myosin

What enzyme is activated by the calcium-calmodulin complex in smooth muscle?

• Myosin light chain kinase

• Adenylate cyclase

• Phospholipase C

• Protein kinase A

How is myosin activated in smooth muscle to form cross-bridges with actin?

• Via ATP hydrolysis

• By direct calcium binding

• Through phosphorylation

• By binding to troponin