Chp 7 Excitation of Skeletal Muscle: Neuromuscular transmission

Question 1

The 3 types of skeletal muscle fibres are:

Answer 1

1. Red / Slow. (Type I fibres, ‘slow twitch fibres’)
2. Red / Fast. (Type IIa fibres, ‘fast oxidative fibres’)
3. White / Fast. (Type IIb fibres, ‘fast glycolytic fibres’)

Question 2

What are Skeletal muscle fibers innervated by?

Answer 2

Skeletal muscle fibers are innervated by large, myelinated nerve fibers that originate from large motoneurons in the anterior horns of the spinal cord

Question 3

each nerve fiber, after entering the muscle belly, nor- mally branches and stimulates from _____ to several hundred ____ ____ _____. Each nerve ending makes a junction, called the _____ _____, with the muscle fiber near its midpoint

Answer 3

1. three

2. skeletal muscle fibers.

3. neuromuscular junction

Question 4

motor end plate is covered by one or more ____ ____that insulate it from the surrounding fluids.

Fig 7.1

Answer 4

Schwann cells

Question 5

What can be found in the axon terminal that supply adenosine triphosphate (ATP), the energy source that is used for synthesis of what kind of transmitter?

Answer 5

1. many mitochondria
2. synthesis of an excitatory transmitter (acetylcholine)

Question 6

What is Acetylcholie responsible for in a muscle ?

Where is it synthesized?

Answer 6

1. The acetylcholine excites the muscle fiber membrane.
2. Acetylcholine is synthesized in the cytoplasm of the terminal, but it is absorbed rapidly into many small synaptic vesicles, about 300,000 of which are normally in the terminals of a single end plate.

Question 7

In the synaptic space are large quantities of enzyme ______, which destroys ____a few milliseconds after it has been released from the synaptic vesicles.

Answer 7

1. enzyme acetylcholinesterase

2. acetylcholine

Question 8

When a nerve impulse reaches the neuromuscular junction, what is being released form the terminals into the symatic space?

Answer 8

125 vesicles of acetylcholine

Question 9

When an action potential spreads over the terminal, ____ _____ ______ _____ open and allow calcium ions to diffuse from the synaptic space to the interior of the nerve terminal.

Answer 9

1. voltage-gated calcium channels

Question 10

Once the Calcium Ions diffuse from the synaptic space to the interior of Nerver terminal, The calcium ions, in turn, are believed to activate _____ _____ dependent protein kinase, which, in turn, phosphorylates ______ _____ that anchor the acetylcholine vesicles to the cytoskeleton of the presynaptic terminal.

Answer 10

1. Ca2 +-calmodulin dependent protein kinase
2. synapsin proteins (regulate neurotransmitter release at synapses)

Definition:

Phosphoretaes-introduce a phosphate group into (a molecule or compound).

Question 11

The fetal acetylcholine receptor complex is composed of five subunit proteins;

Name them:

Answer 11

1. (2) alpha proteins
2. (1) beta,
3. (1) delta
4. (1) gamma

Question 12

The acetylcholine-gated channel has a diameter of ____ ____ which is large enough to allow the important positive ions such as _____, ______,______ to move easily through the opening.

Answer 12

1. 0.65 nanometer
2. sodium (Na+),potassium (K+), and calcium (Ca++)