Skeletal Muscle Physiology

Question 1

The physiology of skeletal muscle was not fully understood until the early 20th century. Some of the earliest experiments on muscle physiology were performed between 1661 and 1665 by ____________, who demonstrated that an isolated frog muscle could be made to contract when the sciatic nerve was irritated with a metal object

Answer 1

Jan Swammerdam

Question 2

the confluence of nerve roots from the lower back

Answer 2

sciatic nerve

Question 3

(1737–1798) demonstrated that frog muscle responded to electrical currents

Answer 3

Luigi Galvani

Question 4

basic unit of a muscle is the

Answer 4

muscle cell, or fiber

Question 5

Whole muscles are made up of bundles of these muscle cell, or fiber

Answer 5

true

Question 6

A single muscle fiber has a very regular structure, defined by

fundamental units of muscle contraction. They are made of actin and myosin filaments and are the most abundant organelles in muscle cells.

Answer 6

myofibrils

Question 7

Each myofibril consists of an arrangement of the contractile proteins

Answer 7

actin and myosin

Question 8

actin and myosin, which are able to slide past each other in the presence of ____________

Answer 8

Ca2+ and ATP

Question 9

__________ is similar to nerve tissue in that it responds to a stimulus in an all-or-none fashion

Answer 9

Skeletal muscle

Question 10

Skeletal muscle is similar to nerve tissue in that it responds to a stimulus in an all-or-none fashion, response is called a ________

Answer 10

twitch

Question 11

Depending on the intensity and frequency of stimulation, ________ numbers of fibers are activated

Answer 11

greater

Question 12

Muscles with large cross-sectional areas are able to generate __________ forces than those with small cross-sectional areas.

Answer 12

larger

Question 13

The muscle fibers and their associated motor nerves are called a

Answer 13

motor unit

Question 14

Greater numbers of ___________ associated with a muscle give finer control over that muscle

Answer 14

motor nerves

Question 15

Motor nerves release the neurotransmitter ____________ from their synaptic bulbs onto the junction of the muscle

Answer 15

acetylcholine

Question 16

This junction between a nerve and a muscle is called the

Answer 16

motor end plate

Question 17

what happens when the acetylcholine is released at the motor end plate

Answer 17

The release of acetylcholine at the motor end plate depolarizes the muscle tissue and in turn leads to the release of intracellular calcium from the sarcoplasmic reticulum, a variant of smooth endoplasmic reticulum

Question 18

where does intracellular calcium come from

Answer 18

from the sarcoplasmic reticulum, a variant of smooth endoplasmic reticulum

Question 19

This release of intracellular calcium sets in motion the biochemical events that allow __________ to move past each other and hydrolyze ATP for energy

Answer 19

actin and myosin

Question 20

Electromyography Biceps and triceps differences in uses

Answer 20

Biceps are more often used in lifting than triceps, but both muscles are always used together in lifting items. With an elbow bent upwards, the biceps must contract while the triceps relax. The opposite happens as it straighten

Question 21

occurs when the muscle length is shortened during a contraction

happening to create muscle tension and overcome the load placed on the muscle. As the load increases, the contraction also increases to create more muscle tension

Answer 21

concentric contraction

Question 22

The opposite of a concentric contraction, where the muscle lengthens as the resistance becomes greater than the force the muscle is producing

An external force applied to the muscle is greater than the force the muscle produces

Answer 22

Eccentric contraction

Question 23

A contraction performed without joint motion, where the muscle length remains constant

Answer 23

Isometric contraction

Question 24

The force of contraction is greater than the force of resistance
The muscle shortens and moves toward its origin
The muscle tension rises to meet the resistance
Examples include standing from a squat or a biceps curl

Answer 24

concentric contraction

Question 24

muscle fatigue verbal encouragement brief rest

Answer 24

As time progresses, more of the muscle is strained, leading to an expected decline in strength and an increase in fatigue As seen in the charts, the results yielded an equal grip force for both verbal encouragement and brief rest, which suggests the same level of efficacy of both methods on limiting muscle fatigue.

Question 25

The force of contraction is less than the force of resistance The muscle lengthens under tension The muscle works to decelerate a joint at the end of a movement Examples include lowering into a squat or lowering into a push-up

Answer 25

Eccentric contractions

Question 26

Visual feedback

Answer 26

pseudo-fatigue would have been observed when the volunteer’s visual feedback was taken away. Similar experiments on proprioceptive drift were noted where blindfolded individuals were asked to do certain hand positions after being given visual cues beforehand and changes were noted the removal of visual feedback is linked to increased force error in contrast to test subjects with visual feedback (Bajewa et al, 2009). Visual feedback plays a crucial role in this experiment as the brain is reliant on multiple sensory inputs for proprioception, especially in hand-localizing focused tasks