Muscular System

Define threshold stimulus

A muscle fiber remains unresponsive until a certain amount of stimulus is applied. This minimal strength required is called the threshold stimulus.

subserous fascia.

Subserous fascia is the portion that forms the connective tissue layer of the serous membranes covering organs in various body cavities and lining those cavities.

antagonist

is a muscle that acts against the prime mover. For instance, if the prime mover raises the arm, the antagonist lowers it. The combination of both the prime mover and antagonist working at the same time will cause the part to remain rigid. This aids in maintaining posture, balance, and locomotion.

synergist

is a muscle that aids the prime mover in its action to move a part

subcutaneous fascia

Subcutaneous fascia is the portion that lies just beneath the skin forming the subcutaneous layer.

A neurotransmitter ____________.

diffuses across a synaptic cleft from a neuron to muscle cell

List three outcomes of muscle actions

1. Movement 2. Muscle actions provide muscle tone. 3. Propel body fluids and food 4. Generate heartbeat 5. Distribute heat

Describe the neural control of skeletal muscle contraction

A neurotransmitter is a chemical stored in the synaptic vesicles, which, when stimulated by a nerve impulse, is released into the gap at the motor end plate and stimulates the fiber to contract.

Describe the difference between a tendon and an aponeurosis

A tendon is a projection of connective tissue beyond the ends of the muscle that attaches to bone. An aponeurosis is a broad fibrous sheet of connective tissue that connects muscles to adjacent muscles.

deep fascia

Deep fascia is the portion of the network of the fasciae that surrounds and penetrates the muscles.

Explain how a skeletal muscle can be stimulated to produce a sustained contraction

If a muscle is exposed to a series of stimuli increasing in frequency, a point is reached where the muscle is unable to complete its relaxation period before the next stimulus arrives. This stacking of twitches causes a sustained contraction.

Describe how connective tissue is part of the structure of a skeletal muscle

Muscle fibers are grouped together in fascicles that are surrounded by a layer of connective tissue called the endomysium. The fascicles are bundled together and surrounded by another layer of connective tissue called the perimysium, which also fills the spaces between the fascicles. Several layers of fibrous connective tissue called the epimysium, which surrounds the entire muscle, then cover the perimysium.

Describe how oxygen is supplied to skeletal muscles.

Oxygen is carried from the lungs by hemoglobin in the blood. When the hemoglobin reaches the muscle, the oxygen is transferred to the myoglobin in the muscle fiber. Myoglobin is similar to hemoglobin in its oxygen capacity, and reduces the muscle's need for continuous blood supply during contraction.

concentric contractions

Shortening occurs If a person lifts an object, the muscles remain taut, their attached ends pull closer together, and the object is moved. The muscle contracts with force greater than resistance and shortens.

Distinguish between a muscle's origin and its insertion

The origin of a muscle is the end of the muscle attached to an immovable part. The insertion is the end of a muscle attached to a moveable part. When a muscle contracts, the insertion is pulled toward the origin.

slow-contracting muscles

They have many mitochondria to carry on aerobic respiration. As a result, they can generate the necessary ATP needed for contraction. They contract for long periods of time prior to muscle fatigue becoming a factor.

Fast-contracting muscles

contain less myoglobin and have a poorer blood supply

prime mover

is the muscle that is primarily responsible for a certain movement

eccentric contractions

lengthening occurs The muscle contracts with less force than resistance and lengthens. Laying a book down on a table is an example.

sustained contraction

many action potentials are triggered in a motor neuron, resulting in a contraction of increasing strength.

Which of the following describes addition of muscle fibers to take part in a contraction?

recruitment

twitch contraction

the contractile response of a single muscle fiber to a muscle impulse.