37 Questions
What type of contraction is isotonic contraction?
The length of the muscle changes
What factor determines muscle tension in a single muscle fiber?
Frequency of action potential
What muscle provides slow contraction for continual, long-term support against gravity?
Soleus
Which factor results in lesser tension developed in a single muscle fiber?
Greater rate of fatigue
What must ocular movements be in order to maintain fixation of the eyes on specific objects?
Extremely rapid
What muscle contract moderately rapidly to provide sufficient velocity of limb movement for running and jumping?
Gastrocnemius
What are factors determining muscle tension in a single muscle fiber?
Rate of fatigue and frequency of action potential
In which type of contraction does the duration adapt to the functions of respective muscles?
Isotonic contraction.
What is a motor unit composed of?
A motor neuron and a group of skeletal muscle fibers
Which type of muscles generally have more nerve fibers for fewer muscle fibers in a motor unit?
Small muscles that react rapidly and require fine control
Which muscle fiber type can deliver greater amounts of powerful forces for a few seconds to a minute or so?
Fast-twitch fibers
Which muscle fiber type provides endurance and delivers prolonged strength of contraction over many minutes to hours?
Slow-twitch fibers
What are fast-twitch muscle fibers mainly composed of?
Fast-twitch fibers
Which feature characterizes slow-twitch muscle fibers?
Prolonged strength of contraction over hours
Why do small muscles that require fine control have more nerve fibers for fewer muscle fibers?
To allow for precise and coordinated movements
What is a characteristic of slow fibers compared to fast fibers?
Smaller nerve fibers innervate them
What gives slow muscles a reddish appearance?
Myoglobin
Which fiber type has greatly increased numbers of mitochondria?
Slow fibers
What is the primary function of myoglobin in slow fibers?
Store oxygen until needed
Which fiber type has a large amount of glycolytic enzymes for rapid energy release?
Fast fibers
What contributes to the reddish appearance of slow muscles?
Myoglobin
Which fiber type is characterized by having a less extensive blood supply compared to slow fibers?
Fast fibers
What is the primary function of myoglobin in slow muscles?
Store oxygen until needed
What does summation in muscle contraction refer to?
Adding together individual twitch contractions to increase the intensity of muscle contraction
Which of the following is NOT a way in which summation can occur in muscles?
By decreasing the overlap between actin and myosin filaments
What is the term used to describe the process of successive contractions fusing together into a smooth and continuous muscle contraction?
Tetanization
Which factor contributes to tetanus in muscle contractions?
High calcium ion concentration in the sarcoplasm
What happens during tetanic contraction?
Release of calcium from sarcoplasmic reticulum is faster than the previous action potential is pumped back
What is one cause of muscle fatigue?
Rapid build-up of lactic acid
In multiple fiber summation, what happens as the strength of the stimulus increases?
Smaller motor units are stimulated more
What is the main difference between fast-twitch fibers and slow-twitch fibers?
Fast-twitch fibers are large in diameter, slow-twitch fibers are small in diameter
Which property of skeletal muscles is associated with the 'all or none law'?
Excitability
What does the 'all or none law' state about muscle contraction?
All muscle fibers within a motor unit contract maximally in response to a stimulus
Which type of stimulus is required to elicit an action potential in skeletal muscles?
Threshold stimulus
What happens during depolarization of an action potential in skeletal muscles?
Na+ influx occurs
Which type of contraction involves muscle length remaining constant but tension changing?
Isometric contraction
What defines tetanus in the context of muscle contraction?
'All or none law' being obeyed during contraction
Test your knowledge on different types of muscle contractions and their functions, such as isotonic contractions and maintenance of posture. Explore the adaptations of muscle contractions to specific functions like ocular movements and lifting loads.
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