Neuromuscular Blocking Agents

Question 1

NMBA prevent what?

Answer 1

Acetylcholine from activating nicotinic M receptors on skeletal muscle.

Question 2

NMBA AKA?

Answer 2

Nicotinic Cholinergic transmission

Question 3

NMBA block what receptors? and what two types of categories are there?

Answer 3

Acetylcholine from activating nicotinic M receptors on skeletal muscle.
Depolarizing and
Non-depolarizing

Question 4

What is excitation contraction coupling?

Answer 4

The process in which action potential in a motor neuron leads to contraction of a muscle.

When a muscle is relaxed, there is an uneven distribution
of electrical charge across the inner and outer surfaces of
the cell membrane (polarized membrane)

Positive charges cover the outer surface of the
membrane, negative charges cover the inner surface

Question 5

What is the Polarization or the resting motor end-plate and muscle membrane?

What phases are included.

Answer 5

The uneven distribution of charge, this means
that the muscle is polarized

Positive charges move from outside to inside causing depolarization of the motor end-plate in response to binding acetylcholine to nicotinic M receptors (more positive inside then out)

Depolarization of the end plate triggers action potential (depolarization) to move down the entire muscle membrane.

Immediately after depolarization occurs, the membrane
returns back to its original resting state by pumping out
positively charged ions from inside the cell
Repolarization follows the unbinding of acetylcholine to Nicotinic M receptors.

Question 6

Steps of muscle contractions

6 Steps

Answer 6

1. An action potential arrives at the terminal of a motor neuron, causing the release of Ach into the junction
2. Ach then binds reversibly to nicotinic m receptors on
   the motor end plate
3. The binding of Ach causes the end plate to depolarize
4. This initiates a muscle action potential (depolarization
   wave that spreads over the entire muscle membrane)

5. This causes a release of calcium ions from the
sarcoplasmic reticulum (SR)

6. Calcium permits the interaction of actin & myosin, and
   when this happens a muscle contraction occurs

Ach then quickly dissociates from the receptors on the
motor end plate and repolarization occurs

Calcium is taken back into the SR, and this causes
relaxation because the actin and myosin cannot work in
the absence of calcium ions

Question 7

Nondepolarizing (competitive) NMBAs

Answer 7

Non depolarizing (competitive) neuromuscular blockers:

Competitive neuromuscular blocking agents are drugs
that compete with Ach for binding to nicotinic m
receptors. These drugs do not depolarize the motor end plate. When these drugs bind to the nicotinic m receptors, they do not cause receptor activation – they block the effects of Ach. This blocking effect causes muscle relaxation throughout the body. Muscle relaxation persists until the amount of drug in the junction is insufficient to prevent receptor occupation by Ach

Binding of non depolarizing neuromuscular blocking
agents to nicotinic m receptors prevents Ach from
binding. This means that with no Ach binding there is no
contraction of the muscles

Question 8

NMBAs Pharmacological effects

Answer 8

Muscle relaxation is the primary effect and this is known
as flaccid paralysis
Muscles of the eyes and face are the first to relax, then
the limbs, abdomen, and glottis. The last muscles
affected are the respiratory muscles (intercostals and
diaphragm)

Question 9

Hypotension - side effect

Answer 9

Hypotension – some neuromuscular blockers can cause
hypotension due to the blockade of nicotinic m receptors,
and also from histamine release (some vasodilation may
occur)

Question 10

What is the effect on consciousness?

Answer 10

These drugs do not cross the blood brain barrier,
therefore they have no effect of consciousness.
It is very important to sedate before giving any paralytic
to our patients

Question 11

Depolarizing muscular agents

Answer 11

Succinylcholine is an ultrashort acting drug and is the
only depolarizing NMB

Succinylcholine binds to nicotinic m receptors on the
motor end plate and causes it to depolarize

This depolarization causes transient muscle contractions
(fasciculations) to occur

Question 12

Depolarizing muscular agents - adverse effects

Answer 12

1

Question 13

Succinylcholine Dose Card

Answer 13

1

Question 14

Rocuronium Dose Card

Answer 14

1

Question 15

Vecuronium Dose Card

Answer 15

1

Question 16

Pancuronium Bromide Dose Card

Answer 16

1