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Human Anatomy & Physiology > Muscular System > Flashcards

Muscular System Flashcards

1
Q

What are the three types of muscles?

A

Skeletal (attached to bone); Smooth (found lining many inter tubes); Cardiac (heart muscle)

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2
Q

Fascicle

A

Discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath (perimysium)

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3
Q

Muscle fiber

A

Elongaged multinucleate cell; has a banded (striated) appearance; surrounded by endomysium

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4
Q

Myofibril

A

complex organelle composed of bundles of myofilaments, composed of sarcomeres arranged end to end

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5
Q

Sarcomere

A

The contractile unit, composed of myofilaments made up of contractile proteins (actin and myson)

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6
Q

What are the two types of myofilaments? What do they do?

A

Thick and thin. Thick filaments contain bundled mysin molecules; thin filaments contain actin molecules. The sliding of the thin filaments past the thick filaments produces muscle shortening.

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7
Q

What is the optimal sarcomere operating length?

A

80-120 percent of resting sarcomere length.

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8
Q

Please describe the 4 steps of muscle contraction?

A
  1. Myosin cross bridge attaches to the actin myofilament. 2. Working stroke-the myosin head pivots and bends as it pulls on the actin filament, sliding it toward the M line (ADP and P released). 3. As new ATP attaches to the myson head, the cross bridge detaches. 4. As ATP is split into ADP and P, cocking of the myosin head occurs.
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9
Q

What is the neuromuscular junction?

A

The point at which the motor neuron sends its signal to the muscle fiber is called the neuromuscular junction. A signal must be continuously sent to the muscle fiber or it will stop contracting.

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10
Q

What is an Action Potential?

A

An action potential is an electrical ‘wave’ that moves along the cell surface, causing an effect when it reaches the end.. Action potentials are also called nerve or muscle impulses.

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11
Q

Where is there more sodium and potassium in the cell?

A

More sodium (NA+) outside the cell. More potassium (K*) inside the cell.

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12
Q

What is the charge of a membrane under resting conditions?

A

The inside of the membrane is negatively charged compared to the outside.

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13
Q

When can ions cross cell membranes?

A

_____ can only cross cell membranes when specific protein channels are present and open.

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14
Q

What causes Depolarization?

A

Sodium entering the cell.

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15
Q

What causes Repolarization?

A

Potassium leaving the cell.

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16
Q

What does the neuromuscular junction consist of?

A

axon terminal – which releases the neurotransmitter acetylcholine (ACh)
motor end plate – where ACh starts an electrical change that spreads to sarcoplasmic reticulum causing release of Ca2+ to the cytoplasm.

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17
Q

What happens in the motor end plate?

A

ACh starts an electrical charge that spreads to SR causing release of CA++ to the cytoplasm.

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18
Q

What are the first two events needed for muscle contraction to occur?

A

1) Action potential generated is propagated along the sarcolemma and down the T tubules. 2. Action potential triggers Ca++ release from terminal cisternae of SR.

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19
Q

What are the 3rd and 4th events needed for muscle contraction to occur?

A
  1. Calcium ions bind to troponin; troponin changes shape, removing the blocking action of tropomyoson; actin active sites exposed. 4. Contraction; myson cross bridges alternatively attach to actin and detach, pulling the actin filaments toward the center of the sarcomere; release of energy by ATP hydrolysis powers the cycling process.
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20
Q

What powers the cycling process during contraction with myosin and actin?

A

Release of energy by ATP hydrolysis!

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21
Q

What are the final two steps of muscle contraction?

A

Removal of Ca++ by active transport into the SR after the action potential ends. 6. Tropomyosin blockage restored blocking actin active site; contraction ends and muscle fiber relaxes.

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22
Q

When the nerve impulse arrives at the axon terminal of motor neuron, what does it trigger?

A

The release of acetylcholine (ACh)

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23
Q

What happens after ACh is released in a muscle contraction?

A

ACh diffuses across synaptic cleft, binds to its receptors in the motor end plate, and triggers a muscle action potential.

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24
Q

What triggers a muscle action potential?

A

ACh diffusing across synaptic cleft, binding to its receptors in the motor end plate.

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25
Q

What role does Acetylcholinesterase play?

A

Acetylcholinesterase in the synaptic cleft destroys ACh so another muscle potential does not arise until more ACh is released from the motor neuron.

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26
Q

What does the action potential travelling along the T tubule do?

A

Opens Ca++ release channels in the SR membrane, which allows calcium ions to flood into the sarcoplasm.

27
Q

____ binds to _____ on the thin filament, exposing the binding sites for _____.

A

Calcium _____ __ troponin __ ___ ____ _______, exposing the ______ sites for myosin.

28
Q

Contraction happens when ______.

A

Power strokes use ATP and myosin heads bind to actin, swivel, and release. Thin filaments are pulled toward the center of the sarcomere.

29
Q

What restores the low level of calcium ions in sarcoplasm after contraction?

A

Ca++ active transport pumps use ATP to restore lower level of ____ ions in sarcoplasm. And the SR closes.

30
Q

What has to happen before the muscle releases?

A

Troponin-tropomyosin must slide back into position and block the myosin binding sites on actin.

31
Q

What is a twitch?

A

A single contraction of a muscle.

32
Q

What is tetanus?

A

A sustained contraction required to move or maintain tension.

33
Q

Treppe

A

An increase in peak tension following repeated stimuli given shortly after the completion of the relaxation phase of each twitch.

34
Q

ISOTONIC CONTRACTION

A

Tension develops and the muscle shortens.

This muscle contraction is involved in movement.

35
Q

ISOMETRIC CONTRACTION

A

Tension develops but muscle does not shorten

36
Q

How does the muscle get the

energy it needs to contract?

A

Glycogen and Myoglobin

37
Q

What is Glycogen?

A

Glycogen is polysaccharide that is a source of potential energy found in skeletal muscles and the liver.

38
Q

What is Myoglobin?

A

Myoglobin is a protein found in red (slow) muscle that acts as an oxygen store

39
Q

What is Creatine Phosphate?

A

Creatine phosphate in an energy source found in muscle cells. Energy is rapidly transferred to make ATP in fast muscle responses but not enough to last long.

40
Q

How does the muscle metabolism work?

A

A resting muscle breaks down fatty acids via aerobic respiration to make ATP.

41
Q

What is the surplus ATP used for during muscle metabolism?

A

_____ ____ is used to build reserves of creatine phosphate (CP) and glycogen.

42
Q

What are the three different types of muscle metabolism/muscle energy source?

A

Direct phosphorylation, anaerobic mechanism; aerobic mechanism.

43
Q

What is direct phosphorylation?

A

It is a coupled reaction of creatine phosphate (CP) and ADP.

44
Q

Where is the energy source for direct phosphorylation? How much oxygen does it use? What are the products? Duration?

A

Energy: Creatine phosphate. No oxygen.
1 ATP per CP, creatine.
15 seconds.

45
Q

What is Anaerobic mechanism? What is the energy source? Oxygen use? Products?

A

glycolysis and lactic acid formation.
energy: glucose.
Oxygen: none.
Products: 2 ATP per glucose, lactic acid.
Duration of energy provision: 30-60 seconds.

46
Q

What is the aerobic mechanism?

A 
Oxidative phosphorylation. 
Energy source: glucose; pyruvic acid; free fatty acids from adipose tissue; amino acids from protein catabolism. 
Oxygen use: Required.
Products: 36 ATP per glucose, CO2, H20!!
Duration of energy: HOURS
47
Q

What sort of activity does anaerobic respiration support?

A

Short bursts of intense muscle activity.

48
Q

What happens when the body uses anaerobic respiration?

A

The muscle cells fatigue quickly. Lactic acid builds up in muscle cells… must be removed from the cell or fatigue and cramps result.

49
Q

How is anaerobic respiration supported?

A

Initially supported by ATP, CP reserves. But then it is supported by glycolysis.

50
Q

What does aerobic respiration support?

A

Long periods of “modest” muscle activity (marathons)

51
Q

Calcium ions are released from the sarcoplasmic reticulum to initiate muscle contraction and are reabsorbed upon muscle relaxation. What occurs if calcium ions are not completely reabsorbed?

A

The next muscle contraction will be greater than the previous muscle contraction.

52
Q

Lactic acid is produced during which reactions?

A

glycolysis; anaerobic respiration

53
Q

Which cells converts lactic acid back to pyruvic acid so pyruvic acid can be involved in producing ATP?

A

liver

54
Q

When the cross-bridges bind to actin, they will pivot in such a manner to cause the actin filaments to slide. This pivoting action causes the actin filaments to slide __________.

A

closer together

55
Q

How is ATP obtained?

A

Through cellular respiration.

56
Q

Fascia

A

is a term for a layer or sheet of connective tissue.

57
Q

The __________ is connective tissue that surrounds the entire muscle. The __________ is connective tissue that surrounds groups of muscle fibers. The __________ is connective tissue that surrounds individual muscle fibers.

A

epimysium; perimysium; endomysium

58
Q

what role does acetylcholine play in muscle contraction?

A

Action potential generates release of acetylcholine. When an action potential of a neuron reaches the neuromuscular junction, the neuron secretes the neurotransmitter acetylcholine (Ach), which diffuses across the synaptic cleft.

Action potential is generated on the motor end plate and throughout the T tubules. Receptors on the motor end plate, a highly folded region of the sarcolemma, initiate an action potential. The action potential travels along the sarcolemma throughout the transverse system of tubules.

59
Q

What are the four phases of a muscle contraction?

A
  1. Latent period (time required for the release of Ca++); 2. Contraction period (muscle contraction); 3. Relaxation period (when Ca++ returns to the SR by active transport; 4. Refractory period (immediately following stimulus, muscle is contracting and therefore will not respond to a second stimulus).
60
Q

What is Creatine Phosphate?

A

Creatine phosphate. Creatine phosphate, a high-energy molecule stored in muscle cells, transfers its high-energy phosphate group to ADP to form ATP. The creatine phosphate in muscle cells is able to generate enough ATP to maintain muscle contraction for about 15 seconds.

61
Q

What is cellular respiration?

A

Cellular respiration is the process by which ATP is obtained from energy-rich molecules.

62
Q

Which cellular respiration process requires oxygen?

A

Aerobic mechanism

63
Q

glycolysis

A

In glycolysis, glucose is broken down to pyruvic acid, and two ATP molecules are generated even though oxygen is not present.

64
Q

How is lactic acid converted back?

A

During anaerobic respiration, pyruvic acid is converted to lactic acid. Lactic acid (via liver enzymes) can be converted back to pyru-vic acid and, with the presence of oxygen, pyruvic acid can enter the mitochondria.

Human Anatomy & Physiology (4 decks)

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