7. Muscle Flashcards Preview

Tissues > 7. Muscle > Flashcards

Flashcards in 7. Muscle Deck (37)
Loading flashcards...
1

Describe skeletal muscle

Attached to bone
Produces body movement
Found in antagonistic muscle pairs: flexors and extensors

2

What are the 2 types of muscle contraction and how do they differ?

Isotonic: tension stays the same and length changes
Isometric: tension changes and length remains the same

3

What are the 2 subtypes of isotonic contraction?

Concentric: shortening
Eccentric: lengthening

4

Skeletal muscle consists of

Bundle of myofibres

5

Describe myofibres

Large and Cylindrical
Multinucleate
Packed with myofibrils

6

Appearance of myofibrils

striated due to light and dark bands

7

What is a sarcomere?

Functional unit of muscle
Lies between 2 Z-lines

8

Describe the process of excitation-contraction coupling of skeletal muscle

An AP propagates along sarcolemma and T tubules
Reaches the Dihydropyridine receptors
Depolarisation causes a conformational change in the DHPRs
Change transmitted to Ryanodine Receptors on sarcoplasmic reticulum
RyR opens: causing Ca2+ release from intracellular stores
Causes depolarisation due to increase in intracellular Ca2+

9

T-Tubules

Membrane invaginations that contact the extracellular fluid
Found in myofibres

10

Sarcoplasmic reticulum (SR)

extensive network of Ca2+ stores surrounding each myofibril

11

What are the different components of a sarcomere?

Z-line
Actin filaments
Myosin
Titin
Nebulin
Tropomyosin
CapZ and Tropomodulin

12

What is a Z line?

Defines lateral boundaries of sarcomere

13

What is actin?

Polymeric thin filament composed of 2 twisted alpha-helices
Displays polarity

14

What is myosin?

Thick filaments
‘motor proteins’
Contain numerous ‘globular heads’ that interact with actin

15

What is titan?

Very large ‘spring-like’ filaments
Anchor myosin to the Z-line

16

What is nebula?

Large filaments associated with actin

17

What is tropomyosin?

Elongated protein bound to actin

18

What are CapZ and Tropomodulin?

Associated with +ve and –ve ends of actin, respectively

19

Describe the sliding filament theory

Calcium binds to Troponin, causing tropomyosin chain to move
Movement exposes myosin binding site on surface of actin chain
'Charged' myosin heads bind to exposed binding sites
Binding and discharge of ADP caused myosin head to pivot (Power stroke), pulling actin filament towards centre of sarcomere
ATP binds to myosin head, releasing it from the chain
ATP hydrolysis provides energy to 'recharge' the myosin head

20

What is the relationship between muscle tension and load in isotonic and isometric contraction?

Isotonic: Tension > Force exerted by load
Isometric: Tension = Force exerted by load

21

What does the tension-load relationship in isotonic contraction cause?

Muscle to contract
Fibres shorten
Energy expenditure (ATP): ‘recharging’ of myosin heads

22

What does the tension-load relationship in isometric contraction cause?

Muscle DOES NOT contract: myosin heads reattach to the same point on actin chain
Energy expenditure (ATP): ‘recharging’ of myosin heads

23

What are cardiomyocytes?

Cells in heart that contract causing movement of blood

24

What are the pacemaker cells in the heart?

Sinoatrial node
Atrioventricular node

25

Describe sinoatrial nodal cells

Small, ‘empty’, spindle shaped cells
spontaneously active

26

Describe atrioventricular node

spindle-shaped network of cells located at base of right atrium

27

Conducting fibres in the heart

Bundle of His
Purkinje fibres

28

What is the bundle of his?

fast conducting cells adjoining the AV node and Purkinje fibres

29

What are purkinje fibres?

large cells that rapidly conduct electrical impulses

30

Describe the appearance of Cardiomyocytes

striated muscle cells that are distinct but are linked by intercalated discs