Lecture 14: Drug effects on smooth muscle

Question 1

where is smooth muscle located?

Answer 1

• walls of hollow organs, including blood vessels (except for capillaries)

Question 2

what is the function of smooth muscle containing organs?

Answer 2

• to act as the body’s conduits for the body’s conduits for the transport of gases, liquids and solids

Question 3

morphology of smooth muscle containing organs?

Answer 3

• cells not striated (thus ‘smooth), worm-shaped

Question 4

name the organs that contain smooth muscle

Answer 4

• blood vessels
• gastrointestinal tract
• bladder (detrusor), ureters, urethra
• uterus (myometrium)
• respiratory system
• Vas deferens and corpus cavernosum
• Fallopian tube
• Iris and ciliary body

Question 5

role of smooth muscle in blood vessels

Answer 5

• 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

Question 6

role of smooth muscle in GI tract

Answer 6

sm controls mixing and propulsion of GI contents

Question 7

role of smooth muscle in bladder (detrusor), ureters, urethra

Answer 7

sm controls urine storage and micturition

Question 8

role of smooth muscle in uterus (myometrium)

Answer 8

sm responsible for labour

Question 9

role of smooth muscle in respiratory system

Answer 9

sm controls diameter of airways (and responsible for coughing)

Question 10

role of smooth muscle in Vas deferens and corpus cavernosum

Answer 10

sm controls erection and ejaculation

Question 11

role of smooth muscle in fallopian tube

Answer 11

sm mediates movement of eggs from ovaries to uterus

Question 12

role of smooth muscle in iris and ciliary body

Answer 12

sm controls pupil diameter and focusing of the lens

Question 13

what kind of drugs are used to affect smooth muscle function in the cardiovascular system to treat CVD?

Answer 13

• vasodilators
• they relax arteries and veins
  e. g. used in hypertension

Question 14

what kind of drugs are used to affect smooth muscle function in treating problems with the GI system?

Answer 14

• spasmolytics: anti-muscarinics (for e.g. IBS) (tends to block muscarinic receptors)
• relaxes muscular spasms of the different parts of the GI tract

Question 15

what kind of drugs are used to affect smooth muscle function in treating problems with the Genitourinary system?

Answer 15

• anti-muscarinics and β₃ agonists to treat LUTS (lower urinary tract syndrome)
• PDE (phosphodiester) inhibitors for erectile dysfunction and LUTS

Question 16

what kind of drugs are used to affect smooth muscle function in treating problems with the myometrium (muscle of uterus)?

Answer 16

• labour inducers: oxytocin, prostaglandin analogues

- tocolytics (delay labour): atosiban (oxytocin antagonist), beta₂ agonists

Question 17

what kind of drugs are used to affect smooth muscle function in treating problems with the respiratory system (e.g. asthma)?

Answer 17

• bronchodilators

- beta₂ agonists (e.g. salbutamol, terbutaline), theophylline

Question 18

what are the two main ways to categorize drugs which affect SM function?

Answer 18

by their mechanisms

1. drugs which block or simulate receptors
2. drugs acting on smooth muscle cell signal transduction

Question 19

name the drugs which block or stimulate receptors

Answer 19

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

Question 20

name the drugs acting on smooth muscle cell signal transduction

Answer 20

Ca²⁺ channel blockers - vasodilators, tocolytics, spasmolytics
K⁺ channel openers - vasodilators
PDE inhibitors - vasodilators
organic nitrates - vasodilators

Question 21

what are vasodilators?

Answer 21

• 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

Question 22

what are spasmolytics?

Answer 22

• a pharmaceutical drug or other agent that suppresses muscle spasms

Question 23

what are bronchodilators?

Answer 23

• type of medication that make breathing easier by relaxing the muscles in the lungs and widening the airways

Question 24

what are tocolytics?

Answer 24

• medications used to suppress premature labor

- designed to inhibit contractions of myometrial smooth muscle cells

Question 25

describe the structure of smooth muscle cells

Answer 25

• ## no z lines, actin anchored in protein aggregates (called DENSE BODIES) which are scattered throughout cytoplasm