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Histology > Muscle > Flashcards

Flashcards in Muscle Deck (59):
1

How is force produced

The movement of actin fibres over myosin fibres, with the aid of a number of accessory proteins

2

4 types of contractile cells

Muscle cells, myoepithelial cells, myofibroblasts, and pericytes

3

Types of muscle cells

Skeletal, cardiac or smooth muscle cells

4

Myoepithelial cells

Found with secretory units of some exocrine glands. They have flattened cells and a contractile protien arrangement similar to smooth muscle

5

Myofibroblasts

Characteristics of both fibroblasts and smooth muscle cells. Enlarge in injury and secrete collagen to provide scaffold for repair and then contract the wound

6

Pericytes

Found around capillaries and venules. Can can act as stem cells but also have contractile properties

7

How are myotubules formed

Within the mesenchyme of the mesoderm, cells will align and eventually lose their separating cell membranes

8

Names given to skeletal muscle

Skeletal, voluntary and striated

9

Muscle tissue is formed from

Muscle cells and associated connective tissue

10

Muscles are formed from

Muscle fibres, blood vessels, nerves, lymphatics, connective tissue and specialised sense organs

11

Characteristics of skeletal muscle fibres

- Striated
- Multinucleated
- Unbranched
- Nuceli are at the periphery of the fibre, just under te cell membrane

12

What is the cell membrane in muscle fibres called

The sarcolemma

13

A bundle of muscle fibres

Fascicle

14

Connective tissue around the muscle as a whole

Epimysium

15

Connective tissue around the fascicle

Perimysuim

16

Connective tissue around a single muscle fibre

Endomysium

17

What is a sarcomere

The smallest contractile unit of a muscle cell

18

What forms a myofibril

Hundreds or thousands of sarcomeres placed end to end

19

Where do sarcomeres extend from/to

From one Z line to the next

20

What is a motor unit

The motor neurone and all of the muscle fibres it innervated

21

Fewer number of muscle fibres in a motor unit =

Finer movement of control

22

Synapse at the end of the motor neurone

Motor end plate

23

Muscle fibres in a motor unit are all

Of the same class

24

What type of junction to almost all muscle fibres have

Neuromuscular junction

25

Neuromuscular junction

- Nearly all mucle fibres have one
- Motor axons terminate at a motor end plate
- Action potential cause the release of acetylcholine
- Initiates an action potential in sarcolemma

26

Tubules within the muscle cell

T-tubules

27

T-tubules

-Extend from sarcolemma into the cell
- Ramify and surrounding each myofibril at the A-I junction of each sarcomere

28

Specialised smooth ER

Sarcoplasmic reticulum

29

Sarcoplasmic reticulum

- Very high concentrations of Ca2+
- LIes on either sides of the T-tubules

30

T-tubule and sarcoplasmic reticulum =

Triad

31

What does an action potential at the neuromuscular jucntion cause

The release of acetylecholine which causes an action potential in the muscle cell

32

An action potential in the muscle cell travels along what

The sarcoplasmic reticulum and invades the T-tubules

33

What does the action potential in the sarcoplasmic reticulum cause

The release of Ca2+

34

The release of Ca2+ causes

The myosin fibrils to ratchet across the actin fibrils, shortening the sarcomere

35

Three types of skeletal muscle fibres

Type I, type IIa, type IIb

36

Type I muscle fibres

- Slow contracting fibres
- Depend on oxidative metabolism
- Have abundant mitochondira and myoglobin
- Resistant to fatigue and produce less force

37

Type IIA muscle fibres

- Intermediate between the other two types
- Relatively uncommon
- Fast twitch but fatigue resistant

38

Type IIB muscle fibres

- Relatively fast contracting fibres
- Depend on anaerobic metabolism
- Fewer mitochondia and myoblogin than type I
- Fatigue relatively easy and produce greater force

39

The myotendinous junctions

Where the collagen of the tendons attaches to the end of the muscle fibres

40

How is the muscle attached to collagen

Through complex interdigitations

41

Why are tendons slow to hear

They have a poor blood supply

42

Specialised sense organs within muscles

Muscle spindles

43

What do muscle spindles provide

Information of the amount of stretch and tension in the muscle

44

Special fibres within the muscle spindle

Intrafusal fibres

45

Normal contracile fibres

Extrafusual muscle fibres

46

Cardiac muscle

- Forms major part of walls of heart chambers and origins of great vessels
- Has striations
- Shorter than skeletal muscle fibres
- Branch to form a complex network

47

Nuclei in cardiac muscle

Have a single nucleus located at the centre of the fibre

48

Dark irregular lines in cardiac muscle

Intercalated discs

49

Function of intercalated discs

Site of end-to-end attachment, maintain mechanical integrity and allow the transmission of electrical impulses

50

Dyad in cardiac muscle

T-tubule and only one branch of sarcoplasmic reticulum

51

Skeletal muscle regenerative capacity

- Has a population of myoblasts called satellite cells at the outer surface of sarcolemma
- Following damage they become activated to proliferate and form new muscle fibres

52

What competes with the regeneration of tissue

Scar tissue

53

Cardiac muscle regenerative capacity

- Small population of stem cells but they play little roles in effective repair
- After muscle is killed, new muscle is not regenerated

54

Smooth muscle

- No visible striations
- Not under conscious control
- Predominantly found in organs

55

Smooth muscle cells

Elongated, spinde-shaped cells with a single cigar shaped nucleus

56

Actin and myosin in smooth muscle

- Not as well organised as skeletal or cardiac muscle
- Converge on dense bodies in cytoplasm
- Converge on focal densities at periphery of the cell

57

Where is smooth muscle found

The gut, respiratory tract, blood vessels, uterus and iris of the eye

58

Contraction of smooth muscle

- Typically recieves signals for both contraction and relaxation
- Smooth muscle either contracts continuously or rhythmically in absence of stimuli
- Appropriate stimuli can modulate contraction either positively or negatively

59

Where does stimuli for smooth muscle originate

Nerve fibres of autonomic nervous system or a hormone