L1 - WBS Muscles and Movement

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Questions and Answers

What neurotransmitter is released at the neuromuscular junction?

GABA

Dopamine

Acetylcholine (correct)

Serotonin

What type of muscle fibers produce fast contractions but fatigue rapidly?

Rapid-twitch fibers

Intermediate-twitch fibers

Slow-twitch fibers

Fast-twitch fibers (correct)

What type of muscles produce lactate and phosphate during vigorous use?

Aerobic muscles

Isotonic muscles

Anaerobic muscles (correct)

Isometric muscles

What is the function of antagonistic muscles?

Moving limbs in opposite directions Signup and view all the answers

What is the role of motor neurons in supplying skeletal muscles?

Extending directly from the CNS to the skeletal muscle Signup and view all the answers

What is the final common pathway for influencing skeletal muscle?

Motor neurons Signup and view all the answers

What type of fibers do not fatigue because they are aerobic?

Slow-twitch fibers Signup and view all the answers

What neurotransmitter binds to nicotinic receptors on the motor end plate?

Acetylcholine Signup and view all the answers

What gives the sensation of muscle fatigue after vigorous use?

Lactate and phosphate Signup and view all the answers

What is the overall effect of other CNS regions on influencing skeletal muscle?

Relative balance of EPSP and IPSP reaching the motor neurons Signup and view all the answers

What is the function of a muscle spindle?

Sends a message to the spinal cord causing muscle contraction when stretched Signup and view all the answers

What is the role of Golgi tendon organ?

Inhibits muscle contraction when it is too intense Signup and view all the answers

What determines the force of contraction of a muscle?

Firing frequencies of individual motor neurons and the number of motor neurons in the pool Signup and view all the answers

What is the role of motor neurons in generating larger forces in muscle contraction?

Recruiting an increasing number of motor units Signup and view all the answers

What is the function of a proprioceptor?

Detects the position or movement of a part of the body Signup and view all the answers

What is the primary function of muscle proprioceptors?

Detect the stretch and tension of a muscle Signup and view all the answers

What is the role of a stretch reflex?

After a muscle is stretched, the spinal cord sends a signal to contract the muscle Signup and view all the answers

What is the function of a motor unit?

Consists of a motor neuron together with all the muscle fibers it innervates Signup and view all the answers

What determines the order of motor neuron recruitment?

Size principle in which smaller motor neurons come online before larger ones Signup and view all the answers

What is the role of reciprocal inhibition?

Allows for relaxation of antagonist muscle while the agonist is contracting Signup and view all the answers

Study Notes

Neuromuscular Junction and Neurotransmitters

Acetylcholine is the neurotransmitter released at the neuromuscular junction.
Acetylcholine binds to nicotinic receptors on the motor end plate, initiating muscle contraction.

Muscle Fiber Types

Fast-twitch fibers produce rapid contractions but fatigue quickly due to reliance on anaerobic metabolism.
Slow-twitch fibers do not fatigue easily as they are primarily aerobic, utilizing oxygen for energy.

Muscle Metabolism

During vigorous use, muscles produce lactate and inorganic phosphate as byproducts of glycolysis.
Muscle fatigue is primarily caused by the accumulation of lactate and phosphate, leading to decreased muscle performance.

Muscle Function and Control

Antagonistic muscles work in opposition to each other to facilitate movement and maintain balance.
Motor neurons supply skeletal muscles by transmitting signals that lead to muscle contraction.
The final common pathway for influencing skeletal muscle involves motor neurons integrating signals from the central nervous system (CNS).

Proprioception and Reflexes

Proprioceptors like muscle spindles and Golgi tendon organs help monitor muscle stretch and tension.
Muscle spindles provide feedback on muscle length, contributing to the stretch reflex mechanism.
Golgi tendon organs sense changes in muscle tension, preventing excessive force during contractions.

Muscle Contraction Dynamics

The force of contraction is determined by the number of motor units activated, the type of muscle fibers recruited, and their firing frequency.
Motor neurons generate larger forces by recruiting additional motor units based on the required intensity of contraction.
The order of motor neuron recruitment typically follows the size principle, where smaller motor neurons are recruited first.

Reflex Mechanisms

A stretch reflex involves the automatic response to stretching of a muscle, aiding in maintaining posture and balance.
Reciprocal inhibition allows for coordinated movement by inhibiting antagonist muscles during contraction of the prime mover, enhancing efficiency.

CNS Influence on Muscles

Other regions of the CNS modulate muscle activity, allowing for fine motor control, coordination, and adaptation to various physical demands.

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Description

Test your knowledge of muscles and their movements with this quiz. Explore the structure and function of muscles, motor neurons, and the release of acetylcholine. Gain a deeper understanding of how animal movement relies on muscle contractions and the innervation of muscle fibers.