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A&P Lecture > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

Skeletal muscle

A

Location: skeletal
Function: move bones
Appearance:multi-nucleated and striated
Control: voluntary

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2
Q

Cardiac muscle

A

Location: heart
Function: pump blood
Appearance: one nucleus, striated, and intercalated discs
Control: involuntary / autorhythmic hormones, neurotransmitters

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3
Q

Visceral (smooth muscle)

A

Location: various organs, ex. GI tract
Function: various functions, ex. Peristalsis
Appearance: one nucleus and no striations
Control: involuntary / autorythmicity

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4
Q

General properties of muscle tissue

• Electrical excitability

A

• ability to respond to certain stimuli by producing electrical signals called action potentials (impulses)

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5
Q

2 main types of action potential stimuli

A

Autorhythmic electrical signals: arises in the muscular tissue itself, as in the heart’s pacemaker
Chemical stimuli: neurotransmitters released by neurons, hormones distributed by the blood, or even local changes in pH

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6
Q

2 main types of action potential stimuli

A

Autorhythmic electrical signals: arises in the muscular tissue itself, as in the heart’s pacemaker
Chemical stimuli: neurotransmitters released by neurons, hormones distributed by the blood, or even local changes in pH

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7
Q

General properties of muscle tissue

• Contractility

A

• Ability of muscular tissue to contract forcefully when stimulated by an action potential

  • when a skeletal muscle contracts, it generates tension (Force of contraction) while pulling on its attachment points
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8
Q

General properties of muscle tissue

• Extensibility

A

• the ability of muscular tissue to stretch, within limits, without being damaged

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9
Q

General properties of muscle tissue

• Elasticity

A

• the ability of muscular tissue to return to its original length and shape after contraction or extension

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10
Q

Functions of muscular tissue

• Producing body movements

A

• movement of the whole body as well as localized movements

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11
Q

Functions of muscular tissue

• Stabilizing body positions

A

• skeletal muscle contractions stabilize joints and help maintain body positions, such as standing or sitting

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12
Q

Functions of muscular tissue

• Storing and mobilizing substances within the body

A

• storage is accomplished by sustained contractions of ringlike bands of smooth muscle called sphincters, which prevent outflow of the contents of a hollow organ

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13
Q

Functions of muscular tissue

• Generating heat

A

• As muscular tissue contracts, it produces heat, a process known as thermogenesis. Involuntary contractions of skeletal muscles, known as shivering, can increase the rate of heat production

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14
Q

Various connective tissue components

• Epimysium

A

• the outer layer, encircling the entire muscle. It consists of dense irregular connective tissue

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15
Q

Various connective tissue components

• Perimysium

A

• also a layer of dense irregular connective tissue, but it surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles called fascicles

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16
Q

Various connective tissue components

• Endomysium

A

• penetrates the interior of each fascicle and separates individual muscle fibers from one another. The endomysium is mostly reticular fibers

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17
Q

Various connective tissue components

• Fascia

A

• is a sheet or band of fibrous connective tissue that is deep to the skin and surrounds muscles and other organs of the body

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18
Q

Various connective tissue components

• Aponeurosis

A

• If, the connective tissue layers extend beyond the muscle to form a rope-like structure it is called a tendon, if they form a flat sheet

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19
Q

The microscopic anatomy of the muscle and the types of muscle filaments

• Sarcolemma

A

• the plasma membrane of a muscle cell

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20
Q

The microscopic anatomy of the muscle and the types of muscle filaments

• sacroplasm

A

• the muscle cell cytoplasm and contains a large amount of glycogen for energy production and myoglobin for oxygen storage

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21
Q

The microscopic anatomy of the muscle and the types of muscle filaments

• Transverse tubules (T tubules)

A

• are tiny invaginations of the sarcolemma that quickly spread the muscle action potential to all parts of the muscle fiber

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22
Q

The microscopic anatomy of the muscle and the types of muscle filaments

• Myofibrils

A

• small thread like structures within the sarcolemma that act as the contractile organelles of skeletal muscle

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23
Q

The microscopic anatomy of the muscle and the types of muscle filaments

• The sarcoplasmic reticulum

A

• encircles each myofibril. It is similar to smooth endoplasmic reticulum in non-muscle

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24
Q

The microscopic anatomy of the muscle and the types of muscle filaments

• Terminal cisterns

A

• Dilated sacs of the sarcoplasmic reticulum that butt against the T tubule from both sides

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25
Q

The microscopic anatomy of the muscle and the types of muscle filaments

• Triad

A

• A transverse tubule and the two terminal cisterns on either side of it
- In a relaxed muscle fiber, the sarcoplasmic reticulum stores calcium ions (Ca2+). Release of Ca2+ from the terminal cisterns of the sarcoplasmic reticulum triggers muscle contraction

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26
Q

Filaments

A

• within the myofibrils are smaller protein structures

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27
Q

Thin filaments

A

• composed of actin
- directly involved in the contractile process
-2 thin filaments for every 1 thick filament in the regions of filament overlap

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28
Q

Thick filaments

A

• composed of myosin
- directly involved in the contractile process
-2 thin filaments for every 1 thick filament in the regions of filament overlap

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29
Q

Sacromeres

A

• The filaments inside myofibrils do not extend the entire length of the muscle fiber, instead they are arranged in compartments
- basic functional units of a myofibril

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30
Q

Components of sarcomere

• Z discs

A

• narrow, plate-shaped regions of dense material that separate one sarcomere from the next

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31
Q

Components of sarcomere

• A band

A

• dark, middle part of sarcomere that extends entire length of thick filaments and includes those parts of thin filaments that overlap thick filaments

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32
Q

Components of sarcomere

• I band

A

• lighter, less dense area of sarcomere that contains remainder of thin filaments but no thick filaments. A Z disc passes through center of each I band

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33
Q

Components of sarcomere

• H zone

A

• narrow region in center of each A band that contains thick filaments but no thin filaments

34
Q

Components of sarcomere

• M line

A

• region in center of H zone that contains proteins that hold thick filaments together at center of sarcomere

35
Q

Components of sarcomere

• zone overlap

A

• thick and thin filaments lie side by side

36
Q

Components of sarcomere diagram

A

Look on doc!

37
Q

Type of muscle protein and specific proteins within

• Contractile proteins

A

• generate force during contraction
- myosin
- actin

38
Q

Type of muscle protein and specific proteins within

• regulatory proteins

A

• help switch the contraction process on and off
- tropomyosin
- troponin

39
Q

Type of muscle protein and specific proteins within

• structural proteins

A

• keep the thick and thin filaments in the proper alignment, give the myofibril elasticity and extensibility, and link the myofibrils to the sarcolemma and extracellular matrix
- titin: helps a sarcomere return to its resting length after a muscle has contracted or been stretched
- a-Actinin: binds actin molecules of thin filaments and to titin molecules
- myomesin: structural protein that forms M line of sarcomere
- nebulin: helps maintain alignment of the thin filaments in the sarcomere
- dystrophin: reinforces the sarcolemma and helps transmit the tension generated by the sarcomeres to the tendons

40
Q

mechanism by which muscles contract and the various ions involved

• sliding filament mechanism

A

•Muscle contraction occurs because myosin heads attach to and “walk” along the thin filaments at both ends of a sarcomere, progressively pulling the thin filaments toward the M line
•Myosin pulls on actin, causing the thin filament to slide inward
•Consequently, Z discs move toward each other and the sarcomere shortens
•Thanks to the structural proteins, there is a transmission of force throughout the entire muscle, resulting in whole muscle contraction
•Note the changes in the I band and H zone as the muscle contracts

41
Q

mechanism by which muscles contract and the various ions involved

• contraction cycle

A

•ATP hydrolysis- the myosin head hydrolyzes ATP and becomes energized and oriented to bind to actin
•Attachment- the myosin head binds to actin forming a cross-bridge
•Power Stroke- the myosin head pivots, pulling the thin filament past the thick filament toward the center of the sarcomere, and the ADP is released from the myosin head
•Detachment- as the myosin binds ATP, the cross-bridge detached from the actin

42
Q

Excitation contraction coupling

A

•During relaxation, the level of Ca2+ in the sarcoplasm is low, only 0.1μ M, because calcium ions are pumped into the sarcoplasmic reticulum by Ca2+ -ATPase pumps.

•A muscle action potential propagating along a transverse tubule causes voltage-gated Ca2+ channels to undergo a conformational change that opens Ca2+ release channels in the sarcoplasmic reticulum, calcium ions flow into the sarcoplasm, and contraction begins

•This concept connects the events of a muscle action potential with the sliding filament mechanism

43
Q

Components and functions of neuromuscular junction

•somatic motor neurons

A

• neurons that stimulate skeletal muscle fibers to contract
- A muscle fiber contracts in response to one or more action potentials propagating along its sarcolemma and through its system of T tubules

44
Q

Components and functions of neuromuscular junction

• neuromuscular junction

A

• muscle action potential arise
• synapse between a somatic motor neuron and a skeletal muscle fiber

45
Q

Components and functions of neuromuscular junction

• Synapse

A

• region where communication occurs between two neurons, or between a neuron and a target cell—in this case, between a somatic motor neuron and a muscle fiber

46
Q

Components and function of neuromuscular junction

• synaptic cleft

A

• small gap in synapses, separating two cells

47
Q

Components and function of neuromuscular junction

• neurotransmitters

A

• in a synapse, the first cell communicates with the second by releasing a chemical messenger

48
Q

Components and function of neuromuscular junction

• axon terminal

A

• At the NMJ, the end of the motor neuron

49
Q

Components and function of neuromuscular junction

• synaptic end bulbs

A

• end of motor neuron divides into cluster, neural part of the NMJ

50
Q

Components and function of neuromuscular junction

• synaptic vesicles

A

•Suspended in the cytosol within each synaptic end bulb are hundreds of membrane enclosed sacs

51
Q

Components and function of neuromuscular junction

• acetylcholine (Ach)

A

• neurotransmitter released at the NMJ

52
Q

Components and function of neuromuscular junction

• motor end plate

A

• region of the sarcolemma opposite of the synaptic end bulbs
- muscular part of the NMJ

53
Q

Components and function of neuromuscular junction

• acetylcholine receptors

A

• Within each motor end plate are 30 million to 40 million acetylcholine receptors
• integral transmembrane proteins (ligand-gated ion channels) to which ACh specifically binds

54
Q

Components and function of neuromuscular junction

• junctional folds

A

• deep grooves in motor end plate that provide large surface area for Ach
• abundant Ach receptors

55
Q

Components and function of neuromuscular junction

• NMJ

A

• includes all of the synaptic end bulbs on one side of the synaptic cleft, the synaptic cleft itself, plus the motor end plate of the muscle fiber on the other side

56
Q

Events at the NMJ produce a muscle action potential

• release of acetylcholine

A

• Voltage-gated calcium channels in a neuron’s synaptic end bulb open, resulting in an influx of calcium. This causes exocytosis of the neurotransmitter, acetylcholine (Ach) into the synaptic cleft

57
Q

Events at the NMJ produce a muscle action potential

• activation of Ach receptors

A

• ACh binds to ligand-gated Na+ channels on the motor endplate, which causes an influx of Na+ into the muscle

58
Q

Events at the NMJ produce a muscle action potential

• production of muscle action potential

A

• This depolarizes the muscle and results in Ca 2+ release from the sarcoplasmic reticulum

59
Q

Events at the NMJ produce a muscle action potential

• termination of Ach activity

A

• ACh gets broken down by acetylcholinesterase (AChE)

60
Q

Muscle metabolism

• creatine phosphate (cp)

A

• only in muscle fibers
•The enzyme creatine kinase (CK) catalyzes the transfer of one of the phosphate groups from ATP to creatine, forming creatine phosphate and ADP
•When contraction begins and the ADP level starts to rise, CK catalyzes the transfer of a phosphate group from creatine phosphate back to ADP to quickly generates new ATP
•Since the formation of ATP from creatine phosphate occurs very rapidly, creatine phosphate is the first source of energy when muscle contraction begins
• 15 seconds

61
Q

Muscle metabolism

• anaerobic glycolysis

A

•requires no oxygen
•When muscle activity continues and the supply of creatine phosphate within the muscle fiber is depleted, glucose is catabolized to generate ATP.
•Glucose passes easily from the blood into contracting muscle fibers via facilitated diffusion, and it is also produced by the breakdown of glycogen within muscle fibers.
•Then, a series of reactions known as glycolysis quickly breaks down each glucose molecule into two molecules of pyruvic acid and two molecules of ATP.
•Each molecule of glucose catabolized via anaerobic glycolysis yields 2 molecules of lactic acid and 2 molecules of ATP
• 2 minutes

62
Q

Muscle metabolism

• cellular respiration

A

•needs oxygen
•pyruvic acid can enter the mitochondria and undergo a series of oxygen-requiring reactions to generate large amounts of ATP
•Muscular tissue has two sources of oxygen:
-oxygen that diffuses into muscle fibers from the blood
-oxygen released by myoglobin within muscle fibers.
•Both myoglobin and hemoglobin are oxygen binding proteins.
‐They bind oxygen when it is plentiful and release oxygen when it is scarce.
•Aerobic respiration supplies enough ATP for muscles during periods of rest or light to moderate exercise provided sufficient oxygen and nutrients are available.
•pyruvic acid obtained from the glycolysis of glucose,
•fatty acids from the breakdown of triglycerides,
•amino acids from the breakdown of proteins.
•In activities that last from several minutes to an hour or more, aerobic respiration provides nearly all of the needed ATP (30-32 molecules of ATP)
• several minutes to hours

63
Q

Muscle fatigue

A

• inability to maintain force of contraction after prolonged activity
•The onset of fatigue is due to:
-Inadequate release of Ca2+ from SR
-Depletion of CP, oxygen, and nutrients
-Build up of lactic acid and ADP
-Insufficient release of ACh at NMJ

64
Q

Oxygen consumption

A

•Why do you continue to breathe heavily for a period of time after stopping exercise?
-To “pay back” your oxygen debt! (recovery oxygen uptake)
•The extra oxygen goes toward:
-Replenishing CP stores
-Converting lactate into pyruvate
-Reloading O2 onto myoglobin

65
Q

Twitch contraction

A

• the brief contraction of all muscle fibers in a motor unit in response to a single action potential

66
Q

Force of contraction

• latent period

A

• brief delay occurs between application of the stimulus (time zero on the graph) and the beginning of contraction (~2msec)

67
Q

Force of contraction

• contraction period

A

• during this time, Ca2+ binds to troponin, myosin‐binding sites on actin are exposed, and cross bridges form. Peak tension develops in the muscle fiber. (10-100 msec)

68
Q

Force of contraction

• contraction period

A

• during this time, Ca2+ binds to troponin, myosin‐binding sites on actin are exposed, and cross bridges form. Peak tension develops in the muscle fiber. (10-100 msec)

69
Q

Force of contraction

• relaxation period

A

• Ca2+ is actively transported back into the sarcoplasmic
reticulum, myosin binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases. (10-100 msec)

70
Q

Force of contraction

• refractory period

A

• when a muscle fiber receives enough stimulation to contract, it temporarily loses its excitability and cannot respond for a time.
-If two stimuli are applied, one immediately after the other, the muscle will respond to the first stimulus but not to the second

71
Q

Frequency of stimulation

• Wave summation

A

• occurs when a second action potential triggers muscle contraction before the first contraction has finished
-Results in a stronger contraction

72
Q

Frequency of stimulation

• Unfused tetanus

A

• when a skeletal muscle fiber is stimulated at a rate of 20 to 30 times per second, it can only partially relax between stimuli. The result is a sustained but wavering contraction

73
Q

Frequency of stimulation

• Fused tetanus

A

• when a skeletal muscle fiber is stimulated at a higher rate of 80 to 100 times per second, it does not relax at all. The result is a sustained contraction in which individual twitches cannot be detected.

74
Q

Isotonic

A

• the tension developed in the muscle remains almost constant while the muscle changes its length.
-used for body movements and for moving objects.
-concentric: the tension generated is great enough to overcome the resistance of the object to be moved, the muscle shortens and pulls on another structure, such as a tendon, to produce movement and to reduce the angle at a joint.
-eccentric- when the length of a muscle increases during a contraction

75
Q

Isometric

A

• muscle contracts but does not change length

76
Q

Skeletal muscle fibers

• Slow oxidative fibers (SO)

A

Location: most commonly attached by tendons to bones
• appear dark bc contains large amount of myoglobin and many blood capillaries; have many large mitochondria so fibers generate ATP mainly by aerobic respiration; slow bc the ATPase in the myosin heads hydrolyzes ATP relatively slow and the contraction cycle proceeds at a slower pace than in fast fiber; resistant to fatigue and are capable of prolonged, sustained contractions for many hours; maintains posture and for aerobic, endurance-type activities

77
Q

Skeletal muscle fibers

• Fast oxidative-glycolytic fibers (FOG)

A

• the largest fibers; contain large amount of myoglobin and many blood capillaries so will be dark; can generate considerable ATP by aerobic respiration so moderately high resistance to fatigue; also generate ATP by anaerobic glycolysis; fast bc myosin head hydrolyzes ATP three to five timers faster than the myosin ATPase in SO fiber; for walking

78
Q

Skeletal muscle fibers

• Fast glycolytic fibers (FG)

A

• low myoglobin content, few blood capillaries, few mitochondria, and appear white in color; contain large amounts of glycogen and generate ATP mainly by glycolysis; due to their ability to hydrolyze ATP rapidly, FG fibers contract strongly and quickly; for intense anaerobic movements of short duration (weight lifting or throwing a ball, but they fatigue quickly/strength training programs that engage a person in activities requiring great strength for short times increase the size, strength, and glycogen content of fast glycolytic fibers)
•contracts only when stimulated by acetylcholine released by a nerve impulse in a motor neuron.

79
Q

Cardiac muscle fibers

A

Location: heart
•intercalated disc contain desmosomes and gap junctions that allow muscle action potentials to spread from one muscle fiber to another
•contracts when stimulated by its own autorhythmic muscle fibers
•depends largely on aerobic respiration to generate ATP, and thus requires a constant supply of oxygen

80
Q

Smooth muscle fibers

A

Location: Walls of hollow viscera, airways, blood vessels, iris and ciliary body of eye, arrector muscles of the hair

•It is thick in the middle, tapered on the ends, and is not striated
•It can be arranged as either single-unit or multi-unit fibers
•contractions start more slowly and last longer than skeletal and cardiac muscle contractions
•can shorten and stretch to a greater extent than skeletal and cardiac muscle
•shorten in response to stretch!

A&P Lecture (3 decks)

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