Deck 9: Skeletal Muscle Relaxants

Question 1

What are the physiological events that precede skeletal muscle contraction

Answer 1

Skeletal muscle contraction is the contraction of the skeletal muscle fibers when impulses reach the muscles. It takes place by sliding filament theory mechanism.
The physiological events that takes place before skeletal muscle contraction or that leads to skeletal muscle contraction are:
1) Nerve impulse is initiated in the central nervous system i.e. the spinal cord. Motor neurons from here reaches the neuromuscular junction.
2) At the neuromuscular junction, the nerve endings of the neuron contain acetylcholine neurotransmitters which are secreted into the synapse between neuron and the muscle.
3) This acetylcholine neurotransmitter then reaches the nicotine-muscular receptors (Nm receptors) on the muscle fibers.
4) When the neurotransmitter activates the muscle fibers by binding to it, sodium-potassium channel is stimulated resulting in moving of sodium into the muscle cell and moving out of potassium from the muscle cells.
5) This causes depolarization of the muscle cell.
6) As this depolarization spreads on the muscle fiber surface, calcium ions are released from it leading to contraction of the muscle.
Stimulation of muscle fiber is initiated in the spinal cord from which nerve impulse reach the neuromuscular junction through motor neurons. Neurotransmitter release here activates muscle fiber to cause its contraction.

Question 2

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Which of the drugs is correctly paired with its effect

A) succinylcholine: life-threatening cardiac arrest in children
B) tizanidine: hypertension and increased salivation
C) cyclobenzaprine/metaxolol: antagonized by alcohol and sedatives
D) vecuronium: increased blood pressure and heart rate
E) botulinumtoxin: increased respiration

Answer 2

The drug Vecuronium has been reported to have little or no effect on the heart or blood pressure. The drug Cyclobenzaprine is included under the category of centrally acting skeletal muscle relaxants. The patient gives the information about his drinking habits that might lead to drug interaction.
The fact is that drugs that depress central nervous system (CNS) like alcohol potentiate the action and adverse effects of all skeletal muscle relaxants. The drug Tizanidine is centrally acting muscle relaxants and has the potential to decrease blood pressure because of its action on the sympathetic alpha-2 receptors.
Hence the incorrect options are b, c, d and e.
The drug succinylcholine is associated with rapid muscle breakdown resulting in life-threatening rhythms of heart, cardiac arrest and death in children. Therefore the drug should be used only in an emergency condition.
Hence the correct option is .

Question 3

As a health care worker in a busy health maintenance organization (HMO), you work with dozens of patients each day. You've noticed that each of the following three patients who were treated today has been prescribed a drug that could cause problems. For each patient, identify and explain the potential drug problem.
a. Patient A came to the HMO this morning complaining of muscle pain following a back injury. He was prescribed the muscle relaxant cyclobenzaprine. Patient A is always joking with the nurses about how much he drinks. It's clear that he takes several drinks of whiskey every day.
b. Patient B came into the HMO last week with strep throat, for which he was prescribed streptomycin. Today, he's complaining of neck and shoulder pain, which he attributes to driving his car for a total of 20 hours over the past 2 days. Patient B was prescribed metaxalone for the muscle pain.
c. Patient C takes lidocaine for a heart arrhythmia. Yesterday, she injured herself doing calisthenics and spent a sleepless night in pain. Today, she visited the doctor and was prescribed methocarbamol to relax her sore muscles.

Answer 3

a. The drug Cyclobenzaprine is included under the category of centrally acting skeletal muscle relaxants. The patient gives the information about his drinking habits that might lead to drug interaction. The fact is that drugs that depress central nervous system (CNS) like alcohol potentiate the action and adverse effects of all skeletal muscle relaxants.
b. The drug Metaxalone is included under the category of centrally acting skeletal muscle relaxants. It is also given that the patient had been prescribed streptomycin for the throat infection. The streptomycin is known to directly inhibit the neuromuscular function causing skeletal muscle relaxation.
c. The drug Methocarbamol is included under the category of centrally acting skeletal muscle relaxants. He is also being given lidocaine for the treatment of heart arrhythmia. The two drugs being administered have CNS depressant effect that might affect the ability of a patient to perform tasks.

Question 4

Describe the major toxicity associated with neuromuscular blockers and the antidote used.

Question 5

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Which of the following is correct about skeletal muscle relaxants

A) intubation for emergency airway management may be accomplished quickly
B) the clinical indication for these drugs is to prolong surgical procedures
C) centrally acting skeletal muscle relaxants must inhibit nicotinic receptors
D) their use is limited by the amount of histamine released from mast cells
E) the class does not include botulinumtoxinA and B

Question 6

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Skeletal muscle relaxants may alter control of respiration because

A) the diaphragm is a skeletal muscle
B) succinylcholine stimulates the respiratory centers in the brain
C) like dantrolene, all muscle relaxants inhibit the action of norepinephrine at the neuromuscular junction
D) relaxation of the muscles in the lower extremities pulls blood away from the lungs
E) all skeletal muscle relaxants interfere with calcium ion storage in the muscle

Question 7

___ Differentiate between depolarizing blockers and nondepolarizing blockers.

Question 8

How does dantrolene differ from neuromuscular blockers

Question 9

What is a neuromuscular junction (NMJ)

Question 10

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Select the drug or condition(s) that decrease the effects of neuromuscular blockers.

A) neomycin
B) corticosteroids
C) general anesthetics like isoflurane
D) alcohol
E) myasthenia gravis and spinal cord lesions

Question 11

Assume that you work in a surgical unit where you coordinate patient medications. For each of the fol­lowing patients, identify a potential drug problem and how it might be avoided.
a. Jeri is about to have a type of orthopedic surgery that requires a muscle relaxant for best results. Jeri's medical history indicates that she has asthma but is otherwise in good health.
b. Linda is scheduled for surgery on her back. Her surgeon is planning to give her succinylcholine to relax her muscles during the procedure. As far as the surgeon is aware, Linda is in great health other than the vertebrae that require surgery. Linda has confided in you, however, that she has bulimia, which you know can lead to electrolyte imbalance.
c. Susan has knee surgery scheduled. A note on her chart indicates that she will be given succinylcho­line during the operation to relax the muscles in her leg. Her chart also indicates that she takes digi­talis for a heart problem.

Question 12

What is the mechanism of action of centrally acting skeletal muscle relaxants

Question 13

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Which of the following is correct about the nicotinic-muscle (Nm) receptor blocking drugs

A) the mechanism of action is the same as represented by dantrolene
B) all of these drugs depolarize the muscle fiber before blockade occurs
C) calcium ions are released from the storage sites
D) there are two groups in this class: either depolarizing agents or nondepolarizing agents
E) botulinumtoxinA rapidly attaches to these receptors

Question 14

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Which of the following is a way in which skeletal muscles are relaxed

A) blockage of conduction in the spinal cord
B) inhibiting nerve transmission
C) blockage of the Nm receptors
D) decreasing ACH in the neuromuscular junction
E) all of these

Question 15

___ Explain the difference between peripheral skeletal muscle relaxants and centrally acting skeletal muscle relaxants. (LO 9.1, 9.4)

Question 16

When are centrally acting skeletal muscle relaxants used

Question 17

What sites are involved in the production of skeletal muscle relaxation

Question 18

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Which of the following drugs is a preferred treatment in chronic spastic muscle disorders

A) metaxolone
B) vecuronium
C) baclofen
D) methocarbamol
E) neostigmine

Question 19

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Vercuronium and rocuronium are used to

A) relax muscle spasms from "week-end warrior" back strain
B) block acetylcholine at the nicotinic-muscle (Nm) receptor
C) stimulate the nicotinic-muscle (Nm) receptors
D) produce muscle fasciculations in surgery
E) rejuvenate facial appearance by relaxing muscles

Question 20

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Select reasons for using muscle relaxants during surgical or diagnostic procedures.

A) reduce muscle tear
B) decrease body temperature
C) potentiate vasodilators
D) increase muscle tone
E) depress respiration

Question 21

___ Use the following terms in a short paragraph: fasciculation, hyperthermia, vagolytic, and vasodilator.

Question 22

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Which of the following is NOT a potential adverse effect of peripherally acting skeletal muscle relaxants

A) difficulty swallowing (dysphagia)
B) skeletal muscle weakness
C) decreased respiration
D) bronchospasm
E) muscle fasciculations

Question 23

What are the two types of neuromuscular blockers How do they differ in their mechanism of action

Question 24

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Succinylcholine is associated with which of the following actions

A) stimulation of the actin and myosin muscle fibrils directly
B) liver damage because the drug is metabolized only by the liver
C) peripheral neuromuscular receptor blockade after stimulating the Nm receptors
D) longer duration of action than vecuronium
E) stimulation of presynaptic ACH release

Question 25

Why are neuromuscular blockers administered IV

Question 26

Use your critical-thinking skills to answer the following questions. Select the correct answer.
Centrally acting skeletal muscle relaxants

A) include dantrolene and cisatracurium
B) inhibit or reduce activity within the spinal cord (intraneuronal), interrupting the central stimulus to muscle contraction
C) can only be given parenterally
D) cause systemic release of histamine, leading to hypotension
E) counteract the effect of botulinumtoxinB

Question 27

What adverse effects are produced by the neuromuscular blockers as a result of histamine release