Lecture 28- Neuromuscular Junction

Question 1

What is the definition of a motor unit?

Answer 1

The lower motor neuron and the group of muscle fibers it innervates

Question 2

What is required when using more strength (such as picking up a large weight compared to a phone)

Answer 2

Recruiting more motor units

Question 3

What distinguishes a neuromuscular synapse and a neuromuscular junction?

Answer 3

Synapse- a junction between a Neuron and the next cell

NM Junction- type of synapse specifically between motor neurons and muscle cells

Question 4

What is the first step in the neuromuscular junction?

Answer 4

Arrival of an action potential at the synaptic terminal of the motor neuron

Question 5

What is the second step in the neuromuscular junction?

Answer 5

Release of Acetylcholine into synaptic cleft

Question 6

What is the third step in the neuromuscular junction?

Answer 6

Diffusion of Acetylcholine across the synaptic cleft

Question 7

What is the fourth step in the neuromuscular junction?

Answer 7

Activation of Acetylcholine receptors on motor end plate (part of sarcolemma that has ACh receptors)

Question 8

What is the fifth step in the neuromuscular junction?

Answer 8

Production of muscle fiber action potential

Question 9

What is the final step in the neuromuscular junction?

Answer 9

Termination of Acetylcholine activity by the enzyme acetylcholinesterase (AChE)

Question 10

What is acetylcholinesterase?

Answer 10

Enzyme that prevents overstimulation of a muscle fiber

Question 11

What is Acetylcholine?

Answer 11

A neurotransmitter that functions as a chemical messenger between the motor neuron and the muscle fiber.

Question 12

What is the output region of the neuromuscular synapse?

Answer 12

Lower motor neuron (secretes acetycholine)

Question 13

What is the input region of the neuromuscular synapse?

Answer 13

The muscle fiber

Question 14

What is the role of nicotine acetylcholine receptors?

Answer 14

Transduce a chemical signal into an electrical signal with maximum efficiency and speed

Question 15

What are nicotine acetylcholine receptors?

Answer 15

Ligand-gated ion channels/muscle receptors found at the skeletal neuromuscular junction where they mediate neuromuscular transmission

Question 16

Are muscles multinucleate?

Answer 16

Yes

Question 17

What is the sarcolemma?

Answer 17

The plasma membrane of a muscle cell

Question 18

What is the role of transverse tubules?

Answer 18

Allow transmission of the action potential, with its attendant ion shifts, to all parts of the cell, which allows rapid activation of the entire cell

Question 19

Where are transverse tubules located?

Answer 19

Invaginations (dips) within the sarcolemma (plasma membrane of a muscle cell)

Question 20

What is the sarcoplasmic reticulum?

Answer 20

Specialized form of the endoplasmic reticulum of muscle cells, dedicated to calcium ion (Ca2+) handling

Necessary for muscle contraction and relaxation

Question 21

What does each muscle fiber receive innervation from?

Answer 21

ONE motor neuron

Question 22

How many motor neurons can innervate a muscle fiber?

Answer 22

Multiple

Question 23

How many motor fibers can be found in a muscle?

Answer 23

Many (100s-1000s)

Question 24

What does acetylcholinesterase do to prevent over stimulation of a muscle?

Answer 24

Cleaves Acetylcholine into a molecule of acetate and a molecule of choline

Question 25

What is excitation-contraction coupling (EC-Coupling)?

Answer 25

The link between the generation of a action potential (nerve impulse) in the sarcolemma and the start of a muscle contraction