13. Muscle Flashcards Preview

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Flashcards in 13. Muscle Deck (36):
1

Define myasthenia.

Weakness of the muscle.

2

Define myocardium.

Muscular component of the heart.

3

Define myopathy.

Any disease of the muscle.

4

Define myoclonus.

A sudden spasm of the muscle.

5

What is the sarcolemma?

The outer membrane of a muscle cell.

6

What is sarcoplasm?

The cytoplasm of a muscle cell.

7

What is sarcoplasm in reticulum?

The smooth endoplasmic reticulum of a muscle cell.

8

What are the three types of muscle?

Skeletal muscle, cardiac muscle and smooth muscle.

9

What is the widest and longest male type?

Skeletal.

10

What type of muscle has long parallel cylinders, multiple peripheral nuclei and striations?

Skeletal.

11

What type of muscle is under voluntary control?

Skeletal.

12

What type of muscle has short branched cylinders, single central nucleus and striations?

Cardiac.

13

What type of muscle has spindle-shaped, tapering ends, single central nucleus and no striations?

Smooth.

14

How are skeletal muscles developed?

Mesodermally derived. Multi potent myogenic stem cells give rise to my oblasts. There is near-synchronous fusion of myoblasts to form a primary myotube with a chain of multiple central nuclei. The nuclei are gradually displaced to the cell periphery by actin and myosin filaments.

15

What are the three type and colours of skeletal muscle?

Red (smallest and narrowest), white (larger and wider) and intermediate (in colour and size).

16

Compare red and white skeletal muscle fibres in terms of the following: vascularisation, myoglobin, mitochondria, contraction, fatigue, enzyme, inner action and typical location.

Red are richly vascularised, rich in myoglobin, have numerous mitochondria. Their contraction is slow, repetitive and weak but they fatigue slowly. They have lots of oxidative enzymes but have few ATPase. They have few neuromuscular junctions. They're typically found in the limb muscle of animal, postural muscles of back and the breast muscle of migrating birds.
White are poorly vascularised, poor in myoglobin and have few mitochondria. Their contraction is faster and stronger but they fatigue rapidly. They have few oxidative enzymes but a lot of ATPase. They have more neuromuscular junctions. They are typically found at extracellular muscles, muscles controlling finger and the breast muscle of domestic hen.

17

What are skeletal muscle fibres surrounded by?

Endomysium.

18

What are skeletal muscle fascicles surrounded by?

Perimysium.

19

What is skeletal muscle surrounded by?

Epimysium.

20

Which muscle bands are within each other?

MHAZI - M line is within the H band which is within the A band. The Z line is within the I band.

21

List the following in order of increasing size: myofibrils, fascicles, skeletal muscles, myofilaments and muscle fibres.

Myofilaments, myofibrils, muscle fibres, fascicles, skeletal muscle.

22

Which molecules form the thin filaments of skeletal and cardiac muscle?

Actin, tropomyosin and troponin.

23

How can troponin assays be used as a diagnostic tool?

For cardiac ischaemia. Ischaemic cardiac muscle releases troponin within an hour but only stays around for up to 20 hours. This means small changes in troponin blood levels are indicative of cardiac muscle damage.

24

What is the importance of calcium in muscle contraction?

Calcium binds to TnC if troponin and causes a conformational change that moves tropomyosin away from actin's binding sites. This allows myosin heads to bind actin which starts contraction.

25

What is the sequence of events in muscle contraction after calcium's action?

Myosin cross bridges attaches to the actin myofilament.
ADP and PI are released in a working strike, where the myosin head pivots and bends as it pulls on the acting filament and slides it toward the M line.
As new ATP attaches to the myosin head, new cross bridges detach.
ATP splits into ADP and Pi and cocks the myosin head.

26

What is the neuromuscular junction?

Small terminal swellings of the axon containing vesicles of acetylcholine.

27

What is the process of events that lead to contraction of skeletal muscle?

A nerve impulse goes along motor neurone and arrives at the neuromuscular junction.
The impulse prompts release of acetylcholine into there synaptic cleft and causes local depolarisation of sarcolemma.
Voltage gated Na+ channels open and Na+ enters the cell.
General depolarisation spreads over the sarcolemma and into T tubules.
Voltage sensor proteins of T tubule membrane change their conformation.
Gated Ca2+ release channels of adjacent cisternae activated by the step before.

28

What can be seen in a LS of cardiac muscle?

Striations, centrally positioned nuclei, inculcated discs and branching.

29

What can be seen on a TS of cardiac muscle?

Central nuclei, endomysium with a rich supply of capillaries and some lobular profiles showing incipient branching of fibres.

30

What is the function of Punkinje fibres?

To carry the impulses generated by the sinoatrial node to the ventricles.

31

What are three key features of Punkinje fibres?

Abundant glycogen, sparse myofilaments and extensive Gla junction sites.

32

What are some features of smooth muscle presentation?

They are non striated, have no sarcoma res and have no T tubules.

33

What stimuli does smooth muscle contract in response to?

Nerve signals, hormones, drugs, or local concentrations of blood gases.

34

In what disorders can smooth muscle be of clinical significance?

High blood pressure, dysmenorrhea, asthma, atherosclerosis, abnormal gut mobility.

35

Describe the nature of repair possible for the three types of mature muscle.

Skeletal - can't divide but tissue can regenerate by mitotic activity or satellite cells so hyperplasia follows muscle injury. Satellite cells can also cause skeletal muscle hypertrophy.
Cardiac - incapable of regeneration. Following damage, fibroblasts invade, divide and lay down scar tissue.
Smooth - retain their mitotic activity and form new smooth muscle cells. This is evident in pregnant uterus because the wall has hypertrophy and hyperplasia of individual cells.

36

Define myalgia.

Muscle pain.