REVIEW SLIDES

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Chapter 12 Muscle

Describe a “twitch”

Describe a “twitch” A twitch is the rapid contraction and relaxation of a muscle fiber

Describe “summation”

Describe “summation” In summation, the effects of many stimuli are added together to produce a muscle contraction

Describe ’recruitment’

Describe ’recruitment’ Recruitment is when many muscle fibers work together to produce a stronger contraction

Describe ‘tetanus”

Describe ‘tetanus” A tetanus is when the summation of fiber twitches occurs rapidly enough that the muscle produces a smooth, sustained contraction

Calcium acts to stimulate muscle contraction by removing _______________ from actin so that actin can bind to myosin.

Calcium acts to stimulate muscle contraction by removing ____troponin___ from actin so that actin can bind to myosin.

The neurotransmitter secreted from somatic motor neurons is called _________________.

The neurotransmitter secreted from somatic motor neurons is called _acetylcholine___.

Acetylcholine stimulates contraction of skeletal muscle by binding to which acetylcholine receptor?

Acetylcholine stimulates contraction of skeletal muscle by binding to which acetylcholine receptor? nicotinic

The oxygen storage molecule found in muscle is called ______________.

The oxygen storage molecule found in muscle is called ____myoglobin_.

Chicken legs and wings are Composed of dark meat Chicken legs and wings are Composed of dark meat. What molecule is responsible for the darker color of this meat (as opposed to white meat)?

Chicken legs and wings are Composed of dark meat Chicken legs and wings are Composed of dark meat. What molecule is responsible for the darker color of this meat (as opposed to white meat)? Myoglobin, a pigment which stores oxygen so that the endurance muscles have plenty of oxygen over time.

____________________ contraction: A muscle fiber shortens when force is greater than load. _____________________ contraction: A muscle may actually lengthen, despite contraction, if the load is too great. Allows you to lower a weight gently after a full concentric contraction

__concentric__ contraction: A muscle fiber shortens when force is greater than load. __eccentric__ contraction: A muscle may actually lengthen, despite contraction, if the load is too great. Allows you to lower a weight gently after a full concentric contraction See page 376

Describe concentric and eccentric contractions

Describe concentric and eccentric contractions In a concentric contraction, a muscle fiber shortens when force is greater than load. In an eccentric contraction, a muscle may actually lengthen, despite contraction, if the load is too great.

Cardiovascular physiology What is meant by the term “excitation-contraction coupling”?

What is meant by the term “excitation-contraction coupling”? The membrane is excited (depolarized), and this causes muscle contraction. One event leads to the next.

Describe excitation-contraction coupling in a cardiac myocyte

Describe excitation-contraction coupling in a cardiac myocyte A heart cell is stimulated by Na+ influx (from a gap junction) This causes Ca2+ channels to open in the cell membrane (T-tubule) Influx of Ca2+ causes Ca2+ channels in the SR membrane to open. (Ca2+ stimulated Ca2+ release) Ca2+ enters cytoplasm, removes troponin from actin Contraction occurs heart muscle

The sliding filament theory of muscle contraction states that when the muscle shortens, the filaments

The sliding filament theory of muscle contraction states that when the muscle shortens, the filaments slide past one another.

Fig. 12.16 EXPLAIN THIS PICTURE Transverse tubule Sarcoplasmic Copyright © McGraw-Hill Education. Permission required for reproduction or display. Fig. 12.16 EXPLAIN THIS PICTURE Axon terminal Sarcolemma Ca2+ 3 Transverse tubule Transverse tubule 4 Sarcoplasmic reticulum Sarcoplasmic reticulum 1 Nicotinic acetylcholine receptor 3 Transverse tubule voltage-gated calcium channel 2 Skeletal muscle voltage-gated sodium channel 4 Sarcoplasmic reticulum calcium release channel

EXPLAIN THIS PICTURE FIGURE 12.16, p. 372 Skeletal muscle Acetylcholine stimulates influx of Na+ into muscle, which stimulates entry of calcium. The Ca2+ channels are DIRECTLY LINKED to SR Ca2+ channels, which release Ca2+ into cytoplasm, So that Ca2+ can remove troponin from actin Axon terminal Skeletal muscle Sarcolemma Ca2+ 3 Transverse tubule Transverse tubule 4 Sarcoplasmic reticulum Sarcoplasmic reticulum 1 Nicotinic acetylcholine receptor 3 Transverse tubule voltage-gated calcium channel 2 Skeletal muscle voltage-gated sodium channel 4 Sarcoplasmic reticulum calcium release channel

Explain the significance of this graph 2.0 µm 2.25 µm 1.0 1.65 µm Fig. 12.21 Relative tension 0.5 1.25 µm 3.65 µm 60 80 100 120 140 160 Percentage rest length 1.65 µm 2.25 µm 3.65 µm

Explain the significance of this graph As skeletal muscle is stretched, its contraction strength is lowered. 2.0 µm 2.25 µm 1.0 1.65 µm Fig. 12.21 Relative tension 0.5 1.25 µm 3.65 µm 60 80 100 120 140 160 Percentage rest length 1.65 µm 2.25 µm 3.65 µm

In skeletal muscle versus heart muscle, what is the difference between the locations of the calcium channels?

In skeletal muscle versus heart muscle, what is the difference between the locations of the calcium channels? Calcium channels in skeletal muscle are DIRECTLY LINKED to SR Ca2+ channels, so there is an electromechanical release mechanism. There is also a calcium-induced calcium release mechanism. In cardiac myocytes, the receptors are not directly linked and therefore they ONLY have calcium-induced calcium release (see. P. 373) Skeletal muscle Cardiac muscle

CH 12 A person’s __________ is an expression of their maximal capacity for aerobic exercise.

CH 12 A person’s _VO2 max is an expression of their maximal capacity for aerobic exercise. It is called the maximal oxygen uptake, or aerobic capacity It can be increased by training.

The percentage of the maximal oxygen uptake at which a significant rise in blood lactate levels occurs is called the ____________ _______________.

The percentage of the maximal oxygen uptake at which a significant rise in blood lactate levels occurs is called the lactate threshold. (or anaerobic threshold) Or average healthy people, a significant amount of blood lactate appears when the person is exercising at about 50-70% of their VO2 max.

During light exercise, most of the energy being used for skeletal muscle contraction comes from

During light exercise, most of the energy being used for skeletal muscle contraction comes from fatty acids.

As a person increases the intensity of their exercise from light to moderate, the body goes from utilizing mainly fatty acids to using a combination of ____________ and ___________.

As a person increases the intensity of their exercise from light to moderate, the body goes from utilizing mainly fatty acids to using a combination of fatty acids and glucose_.

_________________ from stored glycogen supplies most (66%) of energy during heavy exercise.

_glucose_ from stored glycogen supplies most (66%) of energy during heavy exercise.

Glycogen is made up of long chains of ___________ that when polymerized do not significantly alter the osmolality of the cell.

Glycogen is made up of long chains of glucose that when polymerized do not significantly alter the osmolality of the cell.

_________________ is the amount of oxygen you owe your body to re-fuel the lost oxygen stores, such as those in hemoglobin and myoglobin, and the reversal of lactate  pyruvate.

Oxygen debt is the amount of oxygen you owe your body to re-fuel the lost oxygen stores, such as those in hemoglobin and myoglobin, and the reversal of lactate  pyruvate.

_____________________ is a molecule that releases phosphate to ADP to make ATP.

_Creatine phosphate is a molecule that releases phosphate to ADP to make ATP.

The formation of creatine phosphate is catalyzed by an enzyme called

The formation of creatine phosphate is catalyzed by an enzyme called creatine kinase. (Or creatine phosphokinase).

When a person is doing high-intensity exercise, phosphocreatine helps because it

When a person is doing high-intensity exercise, phosphocreatine helps because it transfers a phosphate to ADP to make some quick ATP Long term effects suggest possible liver damage by taking creatine supplements

Elevated levels of creatine kinase in the blood can indicate

Elevated levels of creatine kinase in the blood can indicate myocardial infarction.

Endurance muscle fibers are called ____________ twitch.

Endurance muscle fibers are called _slow_ twitch. Or slow oxidative fibers

Slow twitch muscle fibers have a rich supply of

Slow twitch muscle fibers have a rich supply of myoglobin

Fast-twitch type II fibers have fewer capillaries and mitochondria than slow-twitch fibers and not as much myoglobin; hence these fibers are also called

Fast-twitch type II fibers have fewer capillaries and mitochondria than slow-twitch fibers and not as much myoglobin; hence these fibers are also called white fibers

Fast-twitch fibers use primarily the ______________ pathway as an energy source.

Fast-twitch fibers use primarily the glycolytic (or anaerobic) pathway as an energy source.

Muscle fatigue is the reversible, exercise-induced reduction in the ability of a muscle to generate force. Muscle fatigue appears to be due to an accumulation of extracellular _______ ion.

Muscle fatigue is the reversible, exercise-induced reduction in the ability of a muscle to generate force. Muscle fatigue appears to be due to an accumulation of extracellular _K+_ ion. Among other things (see p. 382)

All fiber types adapt to endurance training by an increase in _______________ and____________.

All fiber types adapt to endurance training by an increase in mitochondria and aerobic respiratory enzymes.

Skeletal muscles contain stretch receptors called _____________ ___________

Skeletal muscles contain stretch receptors called muscle spindles.

_________________ also called ______________ disease, results from the degeneration of upper and lower motoneurons that control skeletal muscle. This can lead to progressive muscle weakness, atrophy, and spastic paralysis, and death.

ALS (amyotrophic lateral sclerosis) also called Lou Gehrig’s disease, results from the degeneration of upper and lower motoneurons that control skeletal muscle. This can lead to progressive muscle weakness, atrophy, and spastic paralysis, and death.