[012] The neuromuscular junction

Question 1

This a microscopic picture of a neuromascular junction ,, define the regions

Answer 1

Question 2

Action potential carried by voltage-gated sodium channels reaches the nerve ending causing depolarization and opening of………… in active zones regions

Answer 2

voltage-gated Ca++ channels

Question 3

Acetylcholine binds to its…… receptors on the motor endplate

Answer 3

nicotinic

Question 4

Explain the end-plate potential (EPP)

Answer 4

When Inward Na+ conductance is greater than outward K +conductance so muscle membrane depolarizes.

Question 5

Following muscle contraction , Acetylcholine is degraded rapidly by……(enzyme) present in high density in the synaptic cleft into…. (Products)

Answer 5

acetylcholinesterase ,,,, choline and acetate.

Question 6

Some of the released Ach is ….. before reaching any receptor

Answer 6

hydrolyzed

Question 7

Through uptake of ….. , the vesicles are refilled & reused to discharge Ach

Answer 7

choline

Question 8

….. is a receptor that penetrate all the way through the muscle fiber from one side of the fiber to the other

Answer 8

dihydropyridine

Question 9

Activated dihydropyridine receptors activate the sarcoplasmic reticulum through ….. receptors

Answer 9

ryanodine

Question 10

Factors affecting force generation in the skeletal muscle ?

Answer 10

1. Type of muscle fibers

• 2. Frequency of muscle electrical stimulation

• 3. Strength of the muscle stimulation

• 4. Length-tension relationship (preload)

• 5. Force-velocity relationship (afterload)

Question 11

Fast twitch muscle fibers are ….(respiartion) and aid in …. Movements

Answer 11

Mainly anerobic ,,,powerful bursts of movements

Question 12

Fast twitch muscle fibers are ….(respiartion) and aid in …. Movements

Answer 12

Anerobic ,,, strong push

Question 13

During aerobic exercises such as running or swimming,….. fibers are the first to contract

Answer 13

slow-twitch

Question 14

When the……. fibers become tired,….. fibers begin to take over

Answer 14

slow-twitch ,,, fast-twitch

Question 15

Muscles rely on two physiological principles to bring a productive motion ?

Answer 15

• Recruitment

• Summation

Question 16

Recruitment is…….. when the stimulation…. is increased, resulting in the increase in tension in the whole muscle

Answer 16

increasing the number of motor units responding to a single stimulus
‘’’
amplitude (strength)

Question 17

Summation is the …… that results when a muscle fiber is unable to relax between twitches due to increased……

Answer 17

Increase in tension ,,,,, stimulation frequency

Question 18

…….is a response of repeated stimulation, where cytosolic calcium remains highly elevated with continuous repeated activation of the contractile mechanism

Answer 18

tetanus

Question 19

Two types of tetanus ?

Answer 19

• Partially fused or incomplete tetanus

• Complete tetanus

Question 20

Partially fused or incomplete tetanus ?

Answer 20

when there are periods of INCOMPLETE relaxation between the summated stimuli

Question 21

• Complete tetanus ?

Answer 21

when there is no relaxation between stimuli

Question 22

Increasing the stimulus strength (amplitude) will increase the…… in the muscle

Answer 22

number of activated muscle fibers

Aka: recruitment

Question 23

passive tension ?

Answer 23

exerted by the unstimulated muscle

Question 24

total tension ?

Answer 24

the tension that a muscle develops when stimulated to contract isometrically

Question 25

Active tension ?

Answer 25

= total tension - passive tension

Question 26

…..of the muscle optimizes the overlap between actin and myosin cross bridges

Answer 26

Stretching

Question 27

The length of the muscle at which the active tension is maximal is called its….

Answer 27

“resting length”

Question 28

Increasing the length of the muscle beyond its resting length will…… the overlap of actin and myosin

Answer 28

decrease

Question 29

…….the length of the muscle below its resting length will reduce the distance at which the actin can move over the myosin decreasing the developed active tension

Answer 29

Decreasing

Question 30

……..Is a competitor inhibitor to acetylcholine on the Ach receptors

Answer 30

Atracurium

Question 31

…. Is another competitor inhibitor to acetylcholine of plant origins

Answer 31

Curare

Question 32

insecticides effect on motor end plate ?

Answer 32

block acetylcholine receptors

Question 33

….. and …… are examples of anticholinesterase are used to reduce degradation of acetylcholine

Answer 33

neostigmine, edrophonium

Question 34

Complications of Myasthenia gravis are improved with …..(drugs)

Answer 34

anticholinesterase

Question 35

……..is a neurotoxin that binds competitively and in a relative irreversible manner to the nicotinic acetylcholine receptors

Answer 35

Alpha-bungarotoxin

Question 36

…….. is a neurotoxin that can cause paralysis, respiratory failure and death

Answer 36

Alpha-bungarotoxin

Question 37

Venom of Australian Eastern brown snake ?

Answer 37

Pseudonaja textilis

Question 38

The venom of ……. snake selectively blocks the release of acetylcholine

Answer 38

Australian Eastern brown snake

Question 39

…… is a depolarizing neuromuscular blocker used to cause short relaxation ,,,, as during anesthesia ;; to allow intubation and in electroconvulsive therapy

Answer 39

Suxamethonium chloride (succinylcholine)

Question 40

…..is an ACH antagonists that is not subject to degradation by acetylcholinesterase

Answer 40

succinylcholine

Question 41

Mention Side effects of succinylcholine :

Answer 41

-increase plasma potassium and intraocular pressure

• muscle twitches

-followed by paralysis and respiratory arrest