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A&P 1 - Muscles > A & P of Skeletal Muscles > Flashcards

A & P of Skeletal Muscles Flashcards

1
Q

Skeletal muscles cells are usually called what?

A

Fibers

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2
Q

Skeletal muscle cells are usually what size and shape?

A

small and long - up to several inches

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3
Q

How many nuclei can one large fiber have?

A

100+

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4
Q

Where are all nuclei located in a fiber?

A

on the outer edge of the cell, just under the cell membrane

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5
Q
  • Muscle cell membrane
A

Sarcolemma

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6
Q
  • Hundreds or thousands make up most of the volume of skeletal muscle fiber
  • Packed together lengthwise
  • Composed of thousands of even tinier protein filaments
  • Mitochondria between produce energy
A

Myofibril

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7
Q

o On the myofibrils, storage organelle for calcium ions

A

Sarcoplasmic reticulum

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8
Q

o System of tubules that extend inward from the sarcolemma (muscle cell membrane)

A
  • Transverse tubules or T-tubules
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9
Q

o Large light-colored bands made up of the thin actin filaments
o Extends from one end of myosin filaments in one sarcomere across the Z line to the beginning of the myosin fibers in the next sarcomere

A

I Bands

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10
Q

o In the center of the I band
o Attachment site for actin filaments
o Disc on each end of the sarcomere

A

Z Line or Z Disc

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11
Q

o Between the I bands
o Where myosin and actin overlap

A

A Bands

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12
Q

o In the middle of the A band
o Made of all myosin, no overlapping actin
o Doesn’t always cover the entire width of the myosin

A

H Bands

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13
Q
  • Series of protein filaments from the myofibril that make up the contractile units of muscle cells
A

Sarcomere

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14
Q

Many sarcomeres laid end to end make up one what?

A

Myofibril

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15
Q

o Sarcomeres share ______ so there is one common _______ between adjacent sarcomeres

A

Z disc

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16
Q

o Thin protein filaments that connect to the Z lines and extend toward the center of the sarcomere, but don’t meet

A

Actin

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17
Q

o Thick protein filaments that float in the middle of the sarcomere, between parallel actin fibers
o Don’t connect to Z lines

A

Myosin

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18
Q

 Twisted tail on the end of the myosin molecule that is attached to two globular heads
 Interact with actin to shorten the sarcomere during muscle contraction

A

Cross bridges

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19
Q

o Sites where the ends of motor nerve fibers connect to muscle fibers

A
  • Neuromuscular Junction
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20
Q

 Exists between the end of the nerve fiber and the sarcolemma

A

o Synaptic space

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21
Q

 Tiny sacs within the end of a nerve fiber in a neuromuscular junction

A

o Synaptic vesicles

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22
Q

 Chemical neurotransmitter
 Released when a nerve impulse comes down the motor nerve fiber
 Quickly diffuses across the synaptic space and binds to receptors on the sarcolemma
 Effect on receptor is very short

A

o Acetylcholine

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23
Q

 One nerve fiber and all the muscle fibers it innervates

A

motor unit

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24
Q

 Muscles for very small, delicate movements (eye muscles) have how many muscle fibers per motor unit?

A

only a few

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25
Q

 Large, powerful muscles (leg muscles) have how many muscle fibers per motor unit?

A

hundreds or more

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26
Q

What kind of tissue layers -
o Skeletal muscle fibers must be securely fastened together and to the structures (usually bones) that they move
o Contain the blood vessels and nerve fibers that supply the muscle fibers

A
  • Connective Tissue Layers
27
Q

 Surrounds each individual skeletal fiber
 Composed of fine, reticular fibers

A

o Endomysium

28
Q

 Groups of skeletal muscle fibers

A

o Fascicles

29
Q

 Composed of reticular fibers and thick collagen fibers

A

o Perimysium

30
Q

 Fibrous connective tissue layer composed largely of tough collagen fibers
 Outer covering of the entire muscle

A

o Epimysium

31
Q

What are the seven steps of muscle contraction?

A
  1. Nerve impulse travels down a motor nerve fiber
  2. Reaches the end of the bulb at the neuromuscular junction
  3. Acetylcholine is released into the synaptic space
  4. Acetylcholine molecules bind to receptors on the surface of the sarcolemma of the muscle cell fiber
  5. Starts an impulse that travels along the sarcolemma and through the T tubules to the interior of the cell
  6. When the impulse reaches the sarcoplasmic reticulum, it causes the release of stored calcium ions (Ca2+) into the sarcoplasm (cytoplasm)
  7. Ca2+ diffuses into the myofibrils and turns on the contraction process, powered by ATP
32
Q

How does muscle relaxation happen?

A
  1. Almost as soon as the sarcoplasmic reticulum releases its Ca2+ into the sarcoplasm, it beings pumping it back in again. This pulls the Ca2+ out of the myofibrils and the contraction shuts down.
  2. The elasticity of the muscle fiber then restores it to its original length, relaxing the fiber. Pumping the Ca2+ back into the sarcoplasmic reticulum requires energy which is also supported by ATP molecules.
33
Q

Muscle contraction and relaxation both require what?

A

ATP

34
Q

What is the ion released during muscle contraction?

A

Ca2+

35
Q

The amount of calcium in the muscle fiber is determined by what?

A

The level of calcium in the bloodstream

36
Q

Hypocalcemia or hypercalcemia is what? And either can cause what?

A

Too high or too low of calcium

abnormalities in skeletal muscle function can result

37
Q

actin and myosin filaments overlap only a little when muscle fiber is what?

A

in a relaxed state

38
Q

When fiber is stimulated to contract, the globular heads attach to the _______ and ratchet back and forth and pull the ______ on both sides toward the _____________

A

tails of myosin
actin
center of the myosin

39
Q

The sliding of the filaments over each other does what to the sarcomere

A

shortens it

40
Q

The combined shortening of all end to end sarcomeres in a muscle fiber

A

 Muscle contraction

41
Q

What principle states that an individual muscle fiber (not a whole muscle) either contracts completely when it receives a nerve impulse or it does not contract at all

A

All or Nothing Principle

42
Q

What is it called when the body controls how many muscle fibers it stimulates for a particular movement
* Small, fine movements require only a few muscle fibers to contract
* Larger, more powerful movements require the contraction of many muscle fibers

A

whole muscle movement

43
Q

 Single muscle fiber contraction

A

Twitch contraction

44
Q

What are the three phases of a twitch contraction?

A

o Latent phase
o Contracting phase
o Relaxation phase

45
Q

How long does the cycle of a twitch contraction take?

A

0.1 seconds

46
Q

Which phase of a twitch contraction is the brief hesitation between the nerve stimulus and the beginning of the actual contraction?

A

o Latent phase

47
Q

 Careful timing of the nerve impulses to the various motor units of the muscle
 Happens when all the muscle fiber activity is averaged out

A

Smooth muscle contraction

48
Q

Visible muscle twitches during smooth muscle contraction means what?

A

contractions are out of sync

49
Q

What powers the sliding of actin and myosin?

A

ATP

50
Q

 Compound in muscle fiber that acts as a “Battery charger” to convert ADP back to ATP

A

o Creatine phosphate (CP)

51
Q

 Ultimate source of energy used to produce ATP and CP as well as keep the whole system operating

A

o Catabolism (breakdown) of nutrient molecules

52
Q

What are the two main components involved in the chemistry contraction?

A

glucose and oxygen

53
Q

 Stored in the fibers in the form of glycogen

A

Glucose

54
Q

 Stored attached to large protein molecules called myoglobin

A

Oxygen

55
Q

o Red like hemoglobin
o Can store and release large quantities of oxygen

A

Myoglobin

56
Q

 Oxygen supply is adequate to keep up with the energy needs of the fiber
 Maximum amount of energy is extracted from each glucose molecule

A

o Aerobic metabolism

57
Q

 Muscle fibers switch to this when oxygen need exceeds the available supply

A

o Anaerobic metabolism

58
Q

 Result of aerobic metabolism
 Formation as a byproduct of incomplete glucose breakdown

A

Lactic acid

59
Q

After burst of energy is over, some lactic acid diffuses into the bloodstream and goes to the ________, where it is converted back to _______ by a process that requires ________

A

Liver
Glucose
Oxygen

60
Q

An animal may continue to breath heavy for a while as the body repays the ___________

A

An oxygen debt to the liver, to convert lactic acid back to glucose

61
Q

o Considerable amount of the energy produced in muscles is in the form of ______

A

heat

62
Q

What is one major heat generating mechanisms for the body?

A

Muscle activity

63
Q

o If heat production exceeds body needs, excess is eliminated by what?

A

Panting or sweating

64
Q

o Increased heat production by ________ can fight hypothermia

A

shivering

A&P 1 - Muscles (5 decks)

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