Skeletal Muscle

Question 1

Muscle Fibers

Answer 1

Skeletal muscle cells packaged within connective tissue layers, attached to bones by tendons.

Question 2

Epimysium

Answer 2

Connective tissue layers surround the entire muscle.

Question 3

Fascicle

Answer 3

A bundle of muscle fibers

Question 4

Perimysium

Answer 4

CT surrounding groups of muscle fibers known as fascicles.

Question 5

Endomysium

Answer 5

CT surrounding individual muscle fibers

Question 6

Myofibril

Answer 6

Contains individual contractile protein filaments actin and myosin.

Question 7

Actin

Answer 7

Thin filaments

Question 8

Myosin

Answer 8

Thick filaments.

Question 9

Motor Unit

Answer 9

Smallest functional contractile entity within a muscle.

Question 10

A motor unit consists of this single neuron and all the muscle fibers it innervates.

Answer 10

Alpha somatic motor neuron.

Question 11

Each fiber is innervated by a motor neuron at the….Release of the neurotransmitter,….at the….initiates a sequence of events leading to the production of an …on the muscle fiber that is propagated along its surface.

Answer 11

Neuromuscular junction.
Acetylcholine.
Neuro. jct.
Action potential.

Question 12

The process of using an electrical stimulation to produce contraction in a muscle is referred to as…

Answer 12

Excitation-contraction coupling.

Question 13

Describe how Excitation begins in the neural system.

Answer 13

Excitation begins with the stimulation of the dendrites and cell bodies of alpha somatic motor neurons in the spinal cord from excitatory stimuli originating in the motor cortex.
Action potentials generated on the motor neuron axon are conducted to the axon terminal.
The arrival of the action potential at the axon terminal triggers the release of acetylcholine into the synaptic cleft at the neuromuscular junction.

Question 14

Describe how Acetylcholine affects muscle fibers.

Answer 14

Acetylcholine binds to NICOTINIC RECEPTORS on the muscle cell membrane opening LIGAND-REGULATED Na+/K+ GATED CHANNELS resulting in a depolarization of the muscle membrane.

Question 15

What does depolarization of a muscle fiber do?

Answer 15

This depolarization travels deep into the junctional folds where VOLTAGE-REGULATED Na+ GATED CHANNELS are located. The opening of the Na+ channels by the depolarization results in an action potential that is conducted along the membrane of the muscle fiber.

Question 16

When an action potential is started, how does it effect the muscle?

Answer 16

The action potential moves along the surface of the membrane is transported deep into the muscle fiber through TRANSVERSE TUBULES (T-tubules). The action potential activates a voltage sensor in the t-tubule membrane which open Ca++ release channels in the sarcoplasmic reticulum (skeletal SER).

Question 17

What vital function does Ca++ do in the muscle?

Answer 17

Ca++ diffuses out of the sarcoplasmic reticulum into the sarcoplasm and initiates muscle contraction.

Question 18

Why is excitation-contraction coupling also called mechanical coupling?

Answer 18

The skeletal muscle voltage sensor is connected directly to the Sarcoplasmic Reticulum Ca++ Release Channels in.