Check Your Understanding Questions - Skeletal Muscle

Question 1

Muscle tissue is excitable.
What does this mean?

Answer 1

Muscle Tissue reacts to stimulus and can generate an action potential casueing it to contract and shorten

Question 2

How do the elastic properties of muscle contribute to force generation?

Answer 2

allow the muscle to recoil and stretch, storing potential energy

Question 3

A muscle fibre loses its sarcoplasmic reticulum. Explain the effects this would have on muscle function.

Answer 3

The SR is responsible for storing, uptaking and releasing Ca2+, so without it, calcium will not be released, and the the tropomyosin head will not shift, thus myosin wont attach to actin and the sacromere will not shorten

Question 4

Give one explanation as to why muscle fibres are multinucleated.

Answer 4

One explanation for why muscle fibers are multinucleated is that during development, multiple individual muscle precursor cells (myoblasts) fuse together to form a single, large muscle fiber. This fusion process allows for efficient coordination and control of protein synthesis and metabolic activities across the entire length of the muscle fiber, contributing to its overall function and performance.

Question 5

Satellite cells lose their ability to self-renew. How might this affect muscle adaptation long term?

Answer 5

body would have to continuosly produce new satelite cells which would decrease its ability to effeciently regenerate muscle.

Question 6

What myofilaments are found in the A band of the sarcomere?

Answer 6

Both Myosin and Actin can be found

Question 7

Explain the positioning of myosin, tropomyosin and Ca2+ when the muscle is at rest.

Answer 7

Ca2+ is stored in the SR, Tropomyosin is in its blocking position on the actin filament

Question 8

What happens to the length of the sarcomere when the muscle is fully contracted? What about the length of the myofilaments?

Answer 8

the length of the sacromere shortens as it contracts, the myosin and the actin stay the same size

Question 9

What is the function of costameres in skeletal muscle? Where are they found?

Answer 9

Costameres join the sacrolemma to the z disks and keep their structural integrity.
Help transmit force

Question 10

Is it true that a muscle fibre can be simultaneously innervated by a1 and a2 motor neuron?

Answer 10

no just one but a neuron can innervate more than one muscle fiber

Question 11

Is it true that when a motor unit is stimulated, only half of the myofibres in that MU will contract?

Answer 11

No there in an All or None Response so they will all contract

Question 12

What is the junction called where the motor neuron meets the myofibre?

Answer 12

Neuromuscular junction

Question 13

Explain the role of Ca2+, Ach, AChE and Na+ in the propagation of an action potential from the motor neuron to the myofibre.

Question 14

Explain Botox’s mechanism of action.

Question 15

What structures comprise the triad?

Answer 15

The triad in muscle physiology refers to a specialized structure formed by the association of two terminal cisternae of the sarcoplasmic reticulum (SR) and a transverse tubule (T-tubule).

Question 16

The up phase of a bicep curl is called a(n) __________________ contraction. The down phase of a bicep curl is called a(n) _______________________ contraction?

Answer 16

concentric
eccentric

Question 17

What will happen to the length of the muscle fibre when muscle tension = the load applied to it?

Answer 17

Isometric contraction, no change in muscle length

Question 18

How does the load-velocity relationship differ between concentric and eccentric contractions?

Answer 18

The load-velocity relationship differs between concentric and eccentric contractions in that concentric contractions exhibit a decrease in velocity with an increase in load, while eccentric contractions demonstrate an increase in velocity with an increase in load.

Question 19

Describe the difference between a twitch, unfused tetanus
and fused tetanus. Which can generate the most force?
What must take place in order for a fused tetanus to occur?

Answer 19

A twitch is a single, brief contraction and relaxation cycle of a muscle fiber in response to a single action potential. Unfused tetanus occurs when muscle fibers are stimulated at a high frequency, resulting in repeated contractions that partially relax between stimuli. Fused tetanus is achieved when muscle fibers are stimulated at a very high frequency, causing sustained contraction without relaxation between stimuli. Fused tetanus generates the most force. In order for fused tetanus to occur, the frequency of stimulation must be high enough to allow for complete fusion of individual twitches into a smooth, sustained contraction.

Question 20

What are the neural influences on force generation?