Muscular System Flashcards
What are the important functions of the muscular system?
Mobility, posture, and movement
The muscular system is essential for voluntary and involuntary movements.
What types of muscles are involved in voluntary movements?
Skeletal muscles
Skeletal muscles are attached to bones and facilitate body movements.
What type of muscle is under autonomic control and is involuntary?
Cardiac muscle and smooth muscle
These muscles function without conscious control.
What response occurs when thermoreceptors detect a drop in temperature?
The shivering reflex
This reflex involves smooth muscle contractions to generate heat.
What is the role of valves in the peripheral veins?
Prevent backflow of blood
They ensure unidirectional blood flow toward the heart.
What effect does muscle contraction have on blood flow?
Increases blood flow toward the heart
Muscle contraction compresses veins, enhancing blood return.
What is the shape and nucleus count of a skeletal muscle myocyte?
Cylinder-shaped and has many nuclei
This structure contributes to the muscle’s striated appearance.
Where is smooth muscle tissue found?
Walls of hollow organs and vessels
Smooth muscle aids in the movement of substances such as food and blood.
What is the shape and nucleus count of smooth muscle cells?
Spindle-shaped and uninucleate
Smooth muscle fibers are non-striated.
What is the structure of cardiac muscle cells?
Branched, striated, usually uninucleate
Cardiac muscle cells may have two nuclei and are interconnected by intercalated discs.
What role do T-tubules play in muscle contraction?
Help depolarize the cell and carry impulses to the sarcoplasmic reticulum
T-tubules are invaginations of the sarcolemma with high concentrations of ion channels.
What is the function of the sarcoplasmic reticulum (SR)?
Stores and releases calcium ions
The SR is specialized smooth endoplasmic reticulum surrounding myofibrils.
What is a sarcomere?
Basic within muscle tissue specialized for contraction
Sarcomeres consist of actin and myosin filaments.
What happens to the filaments during muscle contraction?
They slide over each other without changing length
Myosin heads pull on thin filaments causing sarcomeres to shorten.
What are the three main types of skeletal muscle fibers?
- Slow-twitch oxidative (SO type I)
- Fast-twitch oxidative-glycolytic (FOG type IIa)
- Fast-twitch glycolytic (FG type IIb)
The proportions of these fibers vary depending on muscle function.
Which type of muscle fibers are associated with maintaining posture?
Slow-twitch fibers
These fibers are more prevalent in muscles that require endurance.
Fill in the blank: The contractile apparatus describes a unit within muscle tissue that is specialized for _______.
[contraction]
What are the characteristics of Slow Twitch, Type I fibers?
Smaller diameter, high capillary density, high myoglobin, high aerobic capacity, low anaerobic capacity, high concentration of mitochondria, high resistance to fatigue, slow contractile velocity, low force production, used for prolonged, low-intensity aerobic activities.
Slow Twitch fibers are ideal for endurance activities.
What are the characteristics of Fast Twitch, Type IIa fibers?
Intermediate diameter, moderate capillary density, moderate myoglobin, both aerobic and anaerobic capabilities, moderate concentration of mitochondria, moderate resistance to fatigue, rapid contractile velocity, moderate force production, used for moderate intensity activities such as running.
Type IIa fibers are versatile and can adapt to different types of training.
What are the characteristics of Fast Twitch, Type IIb fibers?
Larger diameter, low capillary density, low myoglobin, low aerobic capacity, high anaerobic capacity, low concentration of mitochondria, low resistance to fatigue, rapid contractile velocity, high force production, used for short bursts of activity such as sprinting or heavy lifting.
Type IIb fibers are primarily used in explosive movements.
What initiates cardiac muscle contraction?
Myogenic activity generated by pacemaker cells of the sinoatrial (SA) node.
This action potential travels through the heart’s conduction system, including the AV node and Purkinje fibers.
What is oxygen debt?
The amount of oxygen required to restore metabolic conditions to resting levels after physical activity.
It is associated with the buildup of lactic acid and depletion of ATP and oxygen during intense exercise.
What causes muscle fatigue?
Buildup of lactic acid, depletion of ATP, and depletion of oxygen.
Lactic acid is a byproduct of anaerobic respiration.
What is the neuromuscular junction?
The synapse between a motor neuron and a skeletal muscle cell.
It is critical for initiating muscle contraction.
