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Foundations of health and disease > From neuromuscular junction to myocyte > Flashcards

From neuromuscular junction to myocyte Flashcards

1
Q

What are neuromuscular junctions?

A

Specialized intercellular connections between a neuron and a muscle cell (myocyte).

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2
Q

What happens when neuromuscular junctions are stimulated?

A

Stimulation causes the myocyte to contract, known as excitation-contraction coupling (ECC).

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3
Q

How many types of muscle can be distinguished?

A

Three types of muscle can be distinguished: skeletal muscle, cardiac muscle, and smooth muscle.

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4
Q

Which diseases or drug actions can disrupt neuromuscular junctions?

A

Neuromuscular junctions can be disrupted in a number of diseases and as a result of drug action.

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5
Q

Where does acetylcholine (ACh) function as a neurotransmitter?

A

ACh functions as the neurotransmitter at skeletal neuromuscular junctions, the synapse of the vagus nerve, cardiac muscle fibers, synapses in the ganglia of the visceral motor system, and a range of sites in the central nervous system.

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6
Q

Where is ACh synthesized and packaged?

A

ACh is synthesized in the cytosol and packaged into synaptic vesicles.

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7
Q

What happens when synaptic vesicles fuse with the presynaptic membrane?

A

ACh is released into the synaptic cleft.

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8
Q

Where does ACh bind after being released into the synaptic cleft?

A

ACh binds to receptors in the postsynaptic membrane.

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9
Q

What are the two types of acetylcholine (ACh) receptors?

A

The two types of ACh receptors are muscarinic receptors (mACh receptors) and nicotinic receptors (nACh receptors).

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10
Q

Where are muscarinic receptors primarily found?

A

Muscarinic receptors are primarily found in the brain and are G-protein coupled receptors.

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11
Q

Where are nicotinic receptors located?

A

Nicotinic receptors are found at the neuromuscular junction (NMJ) and function as ligand-gated ion channels.

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12
Q

What type of ion channels are nicotinic receptors?

A

Nicotinic receptors are non-selective cation channels, allowing both Na+ and K+ ions to pass through.

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13
Q

What is the role of acetylcholinesterase?

A

Acetylcholinesterase is responsible for breaking down acetylcholine (ACh).

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14
Q

How is acetylcholine released into the synaptic cleft?

A

Acetylcholine is created and stored in synaptic vesicles. Upon stimulation, the vesicles fuse with the presynaptic membrane, leading to ACh release into the synaptic cleft.

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15
Q

What happens when acetylcholine binds to its receptor?

A

Acetylcholine binds to the receptor and activates its function. The receptor can be either an agonist or antagonist, depending on the specific response.

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16
Q

What are functional antagonists used for in acetylcholine pharmacology?

A

Functional antagonists are used to increase muscle relaxation.

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17
Q

What are functional agonists used for in acetylcholine pharmacology?

A

Functional agonists are used to treat diseases like myasthenia gravis.

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18
Q

What are examples of acetylcholine pharmacology agents that cause depolarization at the neuromuscular junction?

A

Examples of depolarizing agents include succinylcholine.

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19
Q

What are examples of acetylcholine pharmacology agents that cause non-depolarization at the neuromuscular junction?

A

Examples of non-depolarizing agents include curare.

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20
Q

What are examples of acetylcholinesterase inhibitors used in pharmacology?

A

Examples of acetylcholinesterase inhibitors include neostigmine and physostigmine.

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21
Q

What are examples of agents that disrupt vesicle release or stimulate release of acetylcholine?

A

Examples include conotoxin and botulinum as disruptors, and 4-aminopyridine as a stimulator of release.

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22
Q

What are examples of choline uptake inhibitors and storage disruptors?

A

Examples of choline uptake inhibitors include hemicholinium-3, and examples of storage disruptors include vesamicol.

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23
Q

What is a fasciculus?

A

A fasciculus refers to a bundle of muscle fibers surrounded by the perimysium.

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24
Q

What is fascia?

A

Fascia is a connective tissue that surrounds and separates muscles and other structures.

25
Q

What is epimysium?

A

Epimysium is the connective tissue layer that surrounds the entire muscle.

26
Q

What is perimysium?

A

Perimysium is the connective tissue layer that surrounds a fasciculus within a muscle.

27
Q

What is a muscle fiber?

A

A muscle fiber, also known as a myofiber, is a single muscle cell capable of contraction.

28
Q

What is endomysium?

A

Endomysium is the connective tissue layer that surrounds individual muscle fibers within a fasciculus.

29
Q

What is a sarcomere?

A

A sarcomere is the basic functional unit of a muscle fiber, consisting of overlapping thick and thin filaments.

30
Q

What are thick filaments?

A

Thick filaments are composed of myosin proteins and are responsible for muscle contraction.

31
Q

What are thin filaments?

A

Thin filaments are composed of actin, troponin, and tropomyosin proteins and are involved in muscle contraction.

32
Q

What is the Z line?

A

The Z line, also known as the Z disc, is a protein structure that anchors the thin filaments and defines the boundaries of a sarcomere.

33
Q

What is the M line?

A

The M line is a protein structure located at the center of the sarcomere, providing support and alignment for the thick filaments.

34
Q

What are the I bands?

A

I bands are regions of the sarcomere where only thin filaments are present. They appear lighter in color.

35
Q

What is the A band?

A

The A band is the region of the sarcomere where thick and thin filaments overlap. It appears darker in color.

36
Q

What happens when acetylcholine (ACh) binds to the receptor?

A

ACh binding to the receptor leads to an influx of Na+ ions.

37
Q

What is the consequence of depolarization and stimulation of Ca2+ channels of the sarcoplasmic reticulum?

A

It leads to the opening of the Ca2+ channels in the sarcoplasmic reticulum.

38
Q

What happens when calcium (Ca2+) flows into the sarcoplasm?

A

It increases Ca2+ levels in the sarcoplasm, causing troponin/tropomyosin to move out of the groove and allowing myosin to interact with actin (Crossbridge Cycling).

39
Q

What happens when ATP is cleaved during muscle contraction?

A

ATP is cleaved, providing energy for the sarcomere to contract.

40
Q

How is calcium (Ca2+) returned to the sarcoplasmic reticulum?

A

Calcium is returned to the sarcoplasmic reticulum by Ca2+ pumps.

41
Q

What is the result of the interaction between thick and thin filaments in sarcomere contraction?

A

Sarcomere contraction occurs as a consequence of the interaction between thick (myosin) and thin (actin) filaments.

42
Q

What are the key structural elements involved in muscle contraction?

A

The key structural elements are actin and myosin, along with the cross-bridges they form.

43
Q

What is the consequence of the interaction between thick and thin filaments in sarcomere contraction?

A

Sarcomere contraction is a consequence of the interaction between thick and thin filaments.

44
Q

What are the key structural elements involved in muscle contraction?

A

The key structural elements are actin and myosin, along with the cross-bridges they form.

45
Q

What is the role of tropomyosin?

A

Tropomyosin blocks the binding sites on the actin filament.

46
Q

What happens to actin when its binding sites are exposed?

A

Actin with binding sites exposed allows myosin to interact and form cross-bridges.

47
Q

How is the groove in the thin filament exposed?

A

: The groove in the thin filament is only exposed in the presence of calcium.

48
Q

What is the role of troponin?

A

Troponin complex binds calcium and undergoes a position change, allowing actin and myosin to interact and form cross-bridges.

49
Q

What does calcium regulate in muscle contraction?

A

Calcium regulates the interaction of actin and myosin, enabling the formation of cross-bridges.

50
Q

What is a cross-bridge in muscle contraction?

A

A cross-bridge refers to the interaction between the myosin head of the thick filament and the actin binding site on the thin filament.

51
Q

What is tension in muscle contraction?

A

Tension refers to the force generated by muscle contraction.

52
Q

What is a twitch?

A

A twitch is a single contraction of a muscle fiber.

53
Q

What is tetany?

A

Tetany is an abnormal excitability of the myocyte, resulting in sustained muscle contractions.

54
Q

What happens during rigor mortis?

A

After death, muscle cells rapidly deplete ATP, causing calcium (Ca2+) to remain high in the sarcoplasm. This leads to sustained contraction of the muscles, with myosin still bound to actin.

55
Q

How does rigor mortis end?

A

Rigor mortis ends when muscle tissue starts to degrade.

56
Q

What is myasthenia gravis?

A

Myasthenia gravis is a rare long-term condition that causes weakness in the skeletal muscles. It is characterized by an antibody-driven autoimmune reaction against the acetylcholine receptors at the neuromuscular junction.

57
Q

How does myasthenia gravis typically manifest?

A

Myasthenia gravis often worsens after periods of activity and improves after periods of rest.

58
Q

What is the potential cause of myasthenia gravis?

A

Myasthenia gravis is often linked to an increased thymus size, and approximately 1 in 10 people with myasthenia gravis have an abnormal growth of the thymus called a thymoma.

Foundations of health and disease (45 decks)

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