What do muscle fibers respond to?

The muscle responds to stronger stimuli by producing the same force. In skeletal muscles a motor neuron can innervate many muscle fibers. This is called a motor unit. There are numerous motor units throughout skeletal muscles.

How does a muscle fiber stop contracting?

Muscle contraction usually stops when signaling from the motor neuron ends, which repolarizes the sarcolemma and T-tubules, and closes the voltage-gated calcium channels in the SR. Ca++ ions are then pumped back into the SR, which causes the tropomyosin to reshield (or re-cover) the binding sites on the actin strands.

What are contractile muscle fibers?

A sarcomere is the basic contractile unit of muscle fiber. Each sarcomere is composed of two main protein filaments—actin and myosin—which are the active structures responsible for muscular contraction. The most popular model that describes muscular contraction is called the sliding filament theory.

What is muscle fiber stimulation?

Stimulation of the muscle fibre, causes a wave of depolarisation to pass down the t-tubule, and the SR to release calcium ions into the sarcoplasm. Calcium is pumped back up into the SR to lower calcium ion concentration in the sarcoplasm, to relax the muscle (turn off contraction).

Can muscle fibers types change in response to targeted exercise?

Yes, there are different types of muscle fibers in the body, which are classified based on how they produce energy. Yes, the different muscle fibers can be trained using specific exercises designed to focus on how they create energy or generate force.

What causes a muscle contraction to stop on a molecular level what allows the muscle to relax explain in terms of the two molecules discussed in Question 5?

What is the ability to receive and respond to stimuli?

Irritability describes the ability to respond to a stimulus.

What are the contracting proteins within a muscle fiber?

2.1) Tropomyosins are contractile proteins which, together with the other proteins actin and myosin, function to regulate contraction in both muscle and non-muscle cells and are ubiquitous in animal cells.

Which of the following events does not occur during muscle contraction?

Decrease in length of actin myofilaments.

What are contractile fibers?

What are Contractile Fibers? Certain myosin isoforms (i.e. myosin II) form bipolar assemblies via the extended coiled-coil domains in the heavy chains (see also “thick filaments”). Actin “thin filaments” with opposite polarity associate with thick filaments to create contractile bundles that can be found in both muscle and nonmuscle cells.

Does skeletal muscle hypertrophy result in more contractile tissue?

Skeletal muscle hypertrophy results in an increased amount of contractile tissue. In rodents, commonly studied leg muscles such as soleus, extensor digitorum longus (EDL),*and thigh muscles contain fibers that extend continuously from one tendon to the other, with a single zone of neuromuscular junctions in their middle.

What structural changes occur as a result of muscle fiber hypertrophy?

Structural Changes that Occur as a Result of Muscle Fiber Hypertrophy Increase in actin filaments Increase in myosin filaments Increase in myofibrils Increase in sarcoplasm Increase in muscle fiber connective tissue Source: Wilmore, J.H. and D. L. Costill. Physiology of Sport and Exercise (2nd Edition).Champaign, IL: Human Kinetics, 1999.

How many actin filaments are in a contractile fiber?

Schematic depicting the basic structure of a contractile fiber, which consists of myosin containing contractile “thick” filaments, and actin “thin” filaments. Contractile bundles vary in thickness and have been shown to contain anywhere between 10 to 300 individual actin filaments [4].