Question

Use the terms below to fill in the blanks. Acetylcholine normally (increases/decreases) stomach contraction by (activating/blocking) (nicotinic/muscarinic) receptors which are also Norepinephrine normally contraction by metabotropic) receptors Atropine normally traction by renergic) receptors which are also (ionotropic/metabotropic). (increases/decreases) stomach smooth muscle (ionotropic/ (activating/blocking) (increases/decreases) stomach smooth muscle con- (cholinergic/ad- (activating/blocking) (ionotropic/ metabotropic).

Answer 1

1. Acetylcholine normally increases stomach contraction by activating muscarinic receptors which are also metabotropic.

Norepinephrine normally decreases stomach smooth muscle contaction by blocking metabotropic receptors.

Atropine normally increases stomach smooth muscle contraction by blocking cholinergic receptors which are also metabotropic.

2. Cholinesterase inhibitors lead to increased acetylcholine in synapses and therefore would give rise to stronger skeletal muscle contraction.

Effect of cholinesterase inhibitors on heart rate:

Cholinesterase inhibitors lead to decreased acetylcholinesterase resulting in slower muscle contraction. This results in abnormally slow heart rate.

Effect of cholinesterase inhibitors on smooth muscles:

Cholinesterase inhibitors lead to reduced smooth muscle contraction in stomach which leads to gastro-intestinal problems.

If cholinesterase inhibitors were given to promote contraction of skeletal muscles what would be the side-effects on heart rate and stomach? How could these side effects be problematic to the patient?

Cholinesterase inhibitors reduce the production of the enzyme cholinesterase which is responsible for breaking down of acetylcholine. These inhibitors increase skeletal muscle contraction. The side effects on heart rate and stomach, however, would be abnormally low heart rate and reduced smooth muscle contraction in stomach which cause:

• Dehydration
• Gastrointestinal: loss of appetite, nausea, loose stools.
• Rash
• Bradycardia (abnormally slow heart rate)
• Peptic ulcer disease
• seizures
• Weight loss, salivation, muscle cramps