Muscle Tension and Mechanics

(1) During exercise, different mechanisms of ____________ production are used based on the duration of exercise.

ATP

Isometric contraction occurs at the ____________ of a muscle contraction as well as during prolonged activities

Beginning

isometric contraction examples

Begins when a weightlifter pulls on a barbell and ends the moment the barbell leaves the floor A man holds open a door for his date During this contraction, tension is building in the series-elastic elements

This "oxygen debt" is repaid by ____________ .

Heavy breathing

The act of a muscle maintaining tension while it lengthens is called isotonic ____________ contraction.

Eccentric

This pattern of stimuli causes a sustained fluttering contraction called ____________ .

Incomplete tetanus

When all nerve fibers are stimulated, an increase in stimulus strength will produce no ____________ in muscle tension.

Increase

The force generated during this time is called ____________ tension.

Internal

(3) For short term energy needs, glucose can be released from storages of ____________ chains.

Glycogen

Which of the following is/are true regarding muscular strength and conditioning?

1. Blood capillary density will increase slow-twitch fibers in response to training for a marathon. 2. Long-term resistance will increase the number of myofibrils in a particular muscle exercised.

(2) At this point, muscles are contracting at the cellular level, but their tension is ____________ by elastic components.

Absorbed

(3) Voluntarily exerting more effort, additional ____________ are recruited, which results in the production of greater forces, prior to joint movement.

Motor Units

Each glucose molecule metabolized by ____________ produces two ATP molecules, allowing for muscle activity to continue for no more than a couple of minutes.

Anaerobic fermentation

ATP and creatine phosphate are collectively known as the ____________ , which provides nearly all the energy required for short bursts of intense activity.

Phosphagen system

Despite this pattern, the whole muscle contracts very smoothly because ____________ function asynchronously, allowing some to relax while others contract.

Motor units

Case Study: A woman in her mid-30s began to experience drooping eyelids followed by difficulty in swallowing. As the condition progressed, she began to feel an overall weakness. Tests indicated that she had an abnormally low number of acetylcholine receptors on her skeletal muscle cells. The diagnosis for this patient is likely an autoimmune disease called ____________ .

Myasthenia gravis

(2) For immediate energy, the ____________ in muscle fiber can supply oxygen for limited cellular respiration.

Myoglobin

To meet the body's demands, this oxygen is needed to rebuild the muscles' stores of ____________ .

Myoglobin

When stimuli reach or exceed ____________ , they excite more motor units.

Threshold

Case Study: A woman in her mid-30s began to experience drooping eyelids followed by difficulty in swallowing. As the condition progressed, she began to feel an overall weakness. Tests indicated that she had an abnormally low number of acetylcholine receptors on her skeletal muscle cells. In severe cases, the ____________ may be removed to reduce the release of hormones that stimulate antibody-producing cells.

Thymus

When the tension overcomes the resistance of the load, the muscle can begin to ____________ .

Shorten

flexion examples

Triceps brachii contracting with less force than the elbow flexors Brachialis concentric Biceps femoris concentric Vastus lateralis eccentric

Caused by a single stimulus, a quick cycle of contraction and relaxation is called a ____________ .

Twitch

(3) Joint ____________ is maintained by the isometric contraction of antagonistic muscles at a single joint.

Stability

isometric muscle contraction

develops tension without changing length

If a muscle fiber is overly contracted, the ____________ filaments butt against the Z discs.

Thick

Conversely, if the muscle fiber is overly stretched, there is not enough overlap between the thick and ____________ myofilaments.

Thin

isotonic muscle contraction

muscle changes in length with no change in tension

isotonic eccentric contraction

muscle lengthens while maintaining tension

isotonic concentric contraction

muscle shortens as it maintains tension

phosphagen system

supplies energy very quickly and is the primary source of energy for very high-intensity exercise

Glycogen-Lactic Acid System

the pathway from glycogen to lactic acid

Based on the size, shape, and ratio of muscle fibers to motor neurons (motor units), rank the following muscles in order of strongest to weakest, starting with #1 being the strongest.

1. Quadriceps femoris 2. Gastrocnemius 3. Brachialis 4. Orbicularis oculi 5. Lateral rectus

Isotonic eccentric contraction examples

A mother lowers her infant into the crib ; A weight lifter puts a barbell back on the floor

Which of the following describes twitch summation

A second stimulus arrives at the muscle before complete relaxation of the first contraction, causing the second contraction to have greater tension than the first one.

Isotonic Contraction examples

A sprinter leaves the starting block A mother lowers an infant into his crib

Isotonic concentric contraction examples

A sprinter leaves the starting block ; A weight lifter pulls a barbell up to his waist ; A man pulls open a door for his date

Case Study: A woman in her mid-30s began to experience drooping eyelids followed by difficulty in swallowing. As the condition progressed, she began to feel an overall weakness. Tests indicated that she had an abnormally low number of acetylcholine receptors on her skeletal muscle cells. In which case, the patient's immune system is making antibodies that bind to ____________ , decreasing their function.

Acetylcholine receptors

Case Study: A woman in her mid-30s began to experience drooping eyelids followed by difficulty in swallowing. As the condition progressed, she began to feel an overall weakness. Tests indicated that she had an abnormally low number of acetylcholine receptors on her skeletal muscle cells. Inhibitors of ____________ are commonly used to treat the effects of this disease.

Acetylcholinesterase

When a muscle is primarily at rest, the majority of the muscle fiber's ATP production is via ____________ .

Aerobic respiration

(5) Aerobic respiration will be supported as long as ____________ function continues.

Cardiopulmonary

In a laboratory setting, an even higher stimulus frequency can cause the muscle to exhibit a state of continual contraction, called ____________ .

Complete tetanus

(4) Progressively increasing force production allows the force to exceed that of the bar's inertia. Extensors of the ankle, knee, and hip begin to contract ____________ .

Concentrically

Subthreshold stimuli produce no muscle ____________ .

Contraction

When the external tension moves a load, this is called the ____________ phase.

Contraction

In the early stages of exercise, ATP is produced by the action of ____________ .

Creatine kinase

The high energy molecule that donates a phosphate to ADP is ____________ .

Creatine phosphate

Therefore, if the thick and thin filaments do not overlap, very few ____________ are formed.

Cross-bridges

The difference between the resting rate of oxygen consumption and the elevated rate following an exercise is called ____________ .

EPOC

Complete tetanus of a muscle happens regularly in the human body.

False

(1) When ready, he initiates neural recruitment of his ankle, knee, and hip extensors by increasing the ____________ of action potentials to the lower-limb extensors.

Frequency

With low-frequency stimulation, the muscle relaxes fully between contractions, resulting in ____________ twitches per stimulus.

Identical

(1) During an ____________ contraction, a muscle contracts without a change in length.

Isometric

(2) No immediate movement of the bar is demonstrated despite the production of muscle force, which demonstrates ____________ contraction.

Isometric

During ____________ contraction, the muscle develops tension without changing in length.

Isometric

When the muscle shortens and the load begins to move, the phase is considered the ____________ phase of contraction.

Isotonic

In addition, the oxygen inhaled is to oxidize and dispose of ____________ .

Lactic acid

The short delay between the stimulus and the onset of the twitch is called the ____________ period.

Latent

During isotonic contraction, a ____________ can be moved.

Load

During an isotonic eccentric contraction, a muscle is allowed to ____________ without going limp.

Lengthen

(4) Long-term exercise requires aerobic ____________ , which makes the maximum amount of ATP possible.

Respiration

aerobic respiration

Respiration that requires oxygen

Case Study: A woman in her mid-30s began to experience drooping eyelids followed by difficulty in swallowing. As the condition progressed, she began to feel an overall weakness. Tests indicated that she had an abnormally low number of acetylcholine receptors on her skeletal muscle cells. Temporary removal of the harmful antibodies from the blood may be accomplished by a technique called ____________ .

Plasmapheresis

extension examples

Quadriceps contracting with greater force than the knee flexors Iliopsoas eccentric Erector spinae concentric Gluteus maximus concentric Rectus abdominus eccentric Latissimus dorsi contracting with greater force than the pectoralis major and anterior deltoid

As the frequency gets progressively higher, the muscle does not have time to ____________ in between twitches. Each twitch rides "piggyback" on the previous one and generates ____________ tension.

Relax ; Higher

In a resting muscle fiber, a ____________ is normally 2.0 to 2.5 micrometers long.

Sarcomere

The body typically consumes an extra 11 L of oxygen after a ____________ .

Strenuous exercise

The more motor units excited, the ______________ the contraction.

Stronger

When multiple motor units are excited, it is termed motor unit ____________ .

Summation

This is the time required for excitation, excitation-contraction coupling, and ____________ of the elastic components of the muscle.

Tensing

During isotonic contraction, the muscle shortens, even though the level of ____________ is maintained.

Tension

Once elastic components are taut, the muscle produces external ____________ .

Tension

This is the optimum length for producing maximum ____________ when the muscle contracts.

Tension