Lecture 14: Drug effects on smooth muscle Flashcards
where is smooth muscle located?
- walls of hollow organs, including blood vessels (except for capillaries)
what is the function of smooth muscle containing organs?
- to act as the body’s conduits for the body’s conduits for the transport of gases, liquids and solids
morphology of smooth muscle containing organs?
- cells not striated (thus ‘smooth), worm-shaped
name the organs that contain smooth muscle
- blood vessels
- gastrointestinal tract
- bladder (detrusor), ureters, urethra
- uterus (myometrium)
- respiratory system
- Vas deferens and corpus cavernosum
- Fallopian tube
- Iris and ciliary body
role of smooth muscle in blood vessels
- sm controls diameter of arteries and veins,
- doing so this regulates the vascular resistance which controls the distribution of BF to different parts of the body and it also regulates the BP
role of smooth muscle in GI tract
sm controls mixing and propulsion of GI contents
role of smooth muscle in bladder (detrusor), ureters, urethra
sm controls urine storage and micturition
role of smooth muscle in uterus (myometrium)
sm responsible for labour
role of smooth muscle in respiratory system
sm controls diameter of airways (and responsible for coughing)
role of smooth muscle in Vas deferens and corpus cavernosum
sm controls erection and ejaculation
role of smooth muscle in fallopian tube
sm mediates movement of eggs from ovaries to uterus
role of smooth muscle in iris and ciliary body
sm controls pupil diameter and focusing of the lens
what kind of drugs are used to affect smooth muscle function in the cardiovascular system to treat CVD?
- vasodilators
- they relax arteries and veins
e. g. used in hypertension
what kind of drugs are used to affect smooth muscle function in treating problems with the GI system?
- spasmolytics: anti-muscarinics (for e.g. IBS) (tends to block muscarinic receptors)
- relaxes muscular spasms of the different parts of the GI tract
what kind of drugs are used to affect smooth muscle function in treating problems with the Genitourinary system?
- anti-muscarinics and β₃ agonists to treat LUTS (lower urinary tract syndrome)
- PDE (phosphodiester) inhibitors for erectile dysfunction and LUTS
what kind of drugs are used to affect smooth muscle function in treating problems with the myometrium (muscle of uterus)?
- labour inducers: oxytocin, prostaglandin analogues
- tocolytics (delay labour): atosiban (oxytocin antagonist), beta₂ agonists
what kind of drugs are used to affect smooth muscle function in treating problems with the respiratory system (e.g. asthma)?
- bronchodilators
- beta₂ agonists (e.g. salbutamol, terbutaline), theophylline
what are the two main ways to categorize drugs which affect SM function?
by their mechanisms
- drugs which block or simulate receptors
- drugs acting on smooth muscle cell signal transduction
name the drugs which block or stimulate receptors
angiotensin 2 receptor antagonists - vasodilators
angiotensin 2 conevrting enzyme inhibitors - vasodilators
alpha₁ blockers - vasodilators
anti-muscarinics - spasmolytics, bromchodilators, LUTS
prostacyclin (PGI₂) analouges - vasodilators
beta₂ agonists - bronchodilators, tocolytics
beta₃ agonists -LUTS
endothelin antagonists - vasodilators
name the drugs acting on smooth muscle cell signal transduction
Ca²⁺ channel blockers - vasodilators, tocolytics, spasmolytics
K⁺ channel openers - vasodilators
PDE inhibitors - vasodilators
organic nitrates - vasodilators
what are vasodilators?
- medications that open (dilate) blood vessels
- affect the muscles in the walls of the arteries and veins, preventing the muscles from tightening and the walls from narrowing
- so blood flows more easily through the vessels
what are spasmolytics?
- a pharmaceutical drug or other agent that suppresses muscle spasms
what are bronchodilators?
- type of medication that make breathing easier by relaxing the muscles in the lungs and widening the airways
what are tocolytics?
- medications used to suppress premature labor
- designed to inhibit contractions of myometrial smooth muscle cells
describe the structure of smooth muscle cells
- ## no z lines, actin anchored in protein aggregates (called DENSE BODIES) which are scattered throughout cytoplasm
