Neuromuscular Physiopathology I - Muscle Structure and Function Review

This set of flashcards covers key topics from neuromuscular physiopathology regarding muscle structure and function, including muscle contraction mechanisms, types of muscle fibers, and physiological properties.

What are the key phases of the contraction cycle in skeletal muscles?

The contraction cycle consists of the arrival of calcium ions, exposure of active sites on actin, cross-bridge formation, power stroke, cross-bridge detachment, and reactivation of myosin.

What is the basic functional unit of a myofibril?

The sarcomere is the basic functional unit of a myofibril.

Which proteins make up the thin myofilament?

The thin myofilament is composed of actin, tropomyosin, and troponin.

What triggers muscle contraction at the molecular level?

The binding of calcium ions to troponin triggers muscle contraction.

What is the primary difference between isotonic and isometric contractions?

Isotonic contractions involve muscle shortening and movement, while isometric contractions involve muscle tension without change in length.

What are the three types of muscle fibers?

Fast fibers, intermediate fibers, and slow fibers.

What is the role of myosin in muscle contraction?

Myosin acts as a motor protein that interacts with actin, causing muscle contraction through the power stroke.

What is the sliding filament theory?

The sliding filament theory describes how muscle contraction occurs by actin filaments sliding over myosin, leading to shortening of the sarcomeres.

What happens to the I bands and H zones during muscle contraction?

During contraction, I bands and H zones get smaller as the sarcomeres shorten.

How is ATP involved in muscle contraction?

ATP provides the energy for the power stroke and is necessary for myosin head reactivation.

What physiological effect do calcium levels have on muscle excitability?

Calcium levels increase muscle excitability and trigger contraction.

What is muscle tone?

Muscle tone is the continuous, partial contraction of muscles maintaining firmness.

What are the primary components of a motor unit?

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

How does the size principle apply to muscle contraction?

The size principle states that smaller motor neurons are recruited before larger ones as strength increases.

What are the four basic properties of muscles?

Excitability, contractility, extensibility, and elasticity.

Which types of muscles are under voluntary control?

Skeletal muscles are under voluntary control.

What is the function of the sarcoplasmic reticulum in muscle cells?

The sarcoplasmic reticulum stores and releases calcium ions during muscle contraction.

What are the characteristics of fast muscle fibers?

Fast fibers are large diameter, fatigue easily, contract quickly, and use anaerobic metabolism.

Describe a twitch contraction.

A twitch contraction is a quick, jerky response to a single stimulus, consisting of a latent phase, contraction phase, and relaxation phase.

What does treppe refer to in muscle physiology?

Treppe is the gradual increase in muscle contraction strength with repeated stimulation.

Define tetanus in muscle activity.

Tetanus is a prolonged, sustained contraction of the muscle with no relaxation.

What is the role of acetylcholine in muscle contraction?

Acetylcholine is released at the neuromuscular junction and binds to receptors on the muscle fiber to initiate an action potential.

What happens during the power stroke in muscle contraction?

The power stroke occurs when the myosin heads pivot towards the M line, pulling actin filaments together.

How does the length-tension relationship affect muscle contraction?

The length-tension relationship indicates that optimal muscle strength occurs when there is maximum overlap of thick and thin filaments.

What are the products of anaerobic glycolysis?

Anaerobic glycolysis produces ATP and lactic acid.

How does aerobic respiration differ in energy production compared to anaerobic processes?

Aerobic respiration yields a higher amount of ATP using oxygen compared to the lower yield from anaerobic processes.

Describe the effect of muscle fatigue.

Muscle fatigue leads to a decrease in the ability to generate force due to prolonged activity.

What is the function of tropomyosin in muscle contraction?

Tropomyosin covers the binding sites on actin when the muscle is relaxed, preventing interaction with myosin.

What factors can affect the strength of muscle contraction?

Strength of contraction can be affected by the rate of motor neuron firing, the load on the muscle, and the recruitment of motor units.

What is the purpose of the endomysium, perimysium, and epimysium?

These connective tissues support and organize muscle fibers within a muscle.

Name the two theories for muscle contraction mechanisms.

The sliding filament theory and the winding filament theory.

What causes the 'staircase phenomenon' seen in muscle contractions?

The staircase phenomenon results from a series of twitch contractions that progressively increase in strength due to increased calcium availability and muscle readiness.