Pharmacological ACTIONS ON SMOOTH MUSCLES
ACETYLCHOLINE ATROPINE ADRENALINE α BLOCKER β BLOCKER
a) Gastrointestinal All visceral smooth muscles that a) Gastrointestinal tract: a) Gastrointestinal tract: a) Bronchial muscles:
tract: receive parasympathetic motor Smooth muscle is relaxed- but Intestinal motility is • Propranolol increases
• Tone and peristalsis in innervations are relaxed by atropine weak and transient action. increased (due to partial bronchial resistance by
the GIT is increased. (M3 blockade). inhibition of relaxant blocking β 2 receptors.
• Sphincters are relaxed. b) Urinary Bladder: sympathetic influences) • In asthmatics, however,
• Abdominal cramps a) Gastrointestinal tract: Detrusor is relaxed (β) and and diarrhea may occur. the condition is consistently
and evacuation of Tone and amplitude of contractions trigone is constricted (α): both worsened and a severe
bowel. of stomach and intestine are actions tend to hinder micturition. b) Genitourinary tract: attack may be precipitated.
reduced; the passage of chyme is Tone of smooth muscle in • Selective β1-blockers such
b) Urinary bladder: slowed-constipation may occur, c) Uterus: bladder trigone, sphincter as atenolol, metoprolol etc
• Both detrusor spasm may be relieved. • Adr can both contract and relax and prostate is reduced by are less likely to cause
muscle and the uterine muscle, respectively blockade of α1 receptors -- bronchospasm.
sphincter have M3 b) Ureter and urinary bladder: through α and β receptors. urine flow in patients with
receptors. Atropine has relaxant action on • Nonpregnant uterus - contracts benign hypertrophy of b) Uterus :
• Peristalsis in ureter is ureter and urinary bladder; urinary • Last month of pregnancy-relaxes prostate (BHP) is Normal uterine activity
increased. retention can occur in older males improved. is not significantly affected.
• The detrusor muscle with prostatic hypertrophy. d) Bronchi:
contracts. (However, the same can be • Adr is a potent bronchodilators
• Bladder trigone and beneficial for increasing bladder (β2). This action is more marked
sphincter relaxes. capacity and controlling detrusor when the bronchi are constricted.
• Promotes voiding of hyperreflexia in neurogenic • Adr can directly stimulate
urine (urination). bladder/enuresis.) respiratory centre (RC) but this
action is seldom manifest at
c) Bronchial muscles: c) Bronchi: clinically used doses.
• Contracts bronchial Atropine causes bronchodilatation • It reduces bronchial secretions.
smooth muscle and and reduces airway resistance, • And relieves bronchial
resulting in especially in COPD and asthma congestion by pulmonary
broncospasm. patients. vasoconstriction(α).
d) Biliary tract and Uterus: e) Splenic capsule:
Relaxation of biliary tract is less Contracts (α) and more RBCs are
marked and effect on uterus is released into circulation. This
minimal. action is not evident in man.
ACETYLCHOLINE ATROPINE ADRENALINE α BLOCKER β BLOCKER
a) Gastrointestinal All visceral smooth muscles that a) Gastrointestinal tract: a) Gastrointestinal tract: a) Bronchial muscles:
tract: receive parasympathetic motor Smooth muscle is relaxed- but Intestinal motility is • Propranolol increases
• Tone and peristalsis in innervations are relaxed by atropine weak and transient action. increased (due to partial bronchial resistance by
the GIT is increased. (M3 blockade). inhibition of relaxant blocking β 2 receptors.
• Sphincters are relaxed. b) Urinary Bladder: sympathetic influences) • In asthmatics, however,
• Abdominal cramps a) Gastrointestinal tract: Detrusor is relaxed (β) and and diarrhea may occur. the condition is consistently
and evacuation of Tone and amplitude of contractions trigone is constricted (α): both worsened and a severe
bowel. of stomach and intestine are actions tend to hinder micturition. b) Genitourinary tract: attack may be precipitated.
reduced; the passage of chyme is Tone of smooth muscle in • Selective β1-blockers such
b) Urinary bladder: slowed-constipation may occur, c) Uterus: bladder trigone, sphincter as atenolol, metoprolol etc
• Both detrusor spasm may be relieved. • Adr can both contract and relax and prostate is reduced by are less likely to cause
muscle and the uterine muscle, respectively blockade of α1 receptors -- bronchospasm.
sphincter have M3 b) Ureter and urinary bladder: through α and β receptors. urine flow in patients with
receptors. Atropine has relaxant action on • Nonpregnant uterus - contracts benign hypertrophy of b) Uterus :
• Peristalsis in ureter is ureter and urinary bladder; urinary • Last month of pregnancy-relaxes prostate (BHP) is Normal uterine activity
increased. retention can occur in older males improved. is not significantly affected.
• The detrusor muscle with prostatic hypertrophy. d) Bronchi:
contracts. (However, the same can be • Adr is a potent bronchodilators
• Bladder trigone and beneficial for increasing bladder (β2). This action is more marked
sphincter relaxes. capacity and controlling detrusor when the bronchi are constricted.
• Promotes voiding of hyperreflexia in neurogenic • Adr can directly stimulate
urine (urination). bladder/enuresis.) respiratory centre (RC) but this
action is seldom manifest at
c) Bronchial muscles: c) Bronchi: clinically used doses.
• Contracts bronchial Atropine causes bronchodilatation • It reduces bronchial secretions.
smooth muscle and and reduces airway resistance, • And relieves bronchial
resulting in especially in COPD and asthma congestion by pulmonary
broncospasm. patients. vasoconstriction(α).
d) Biliary tract and Uterus: e) Splenic capsule:
Relaxation of biliary tract is less Contracts (α) and more RBCs are
marked and effect on uterus is released into circulation. This
minimal. action is not evident in man.
