Muscles & M Tissue Slides Flashcards Preview

Quiz - Joints, Muscle, Myofibril > Muscles & M Tissue Slides > Flashcards

Flashcards in Muscles & M Tissue Slides Deck (34):
1

Skeletal muscle tissue is

Attached to bones
Striated
Voluntary
Powerful
Cylinder shape
Multi- nucleited

2

Cardiac muscle tissue

Only in the heart
Intercalated discs
Striated
Involuntary
1 nucleus

3

Smooth muscle tissue

Not striated
In walls of hollow ograns; stomach bladder, airways
Involuntary
Spindleshaped

4

Excitability

Receive/respond to stimuli
Electrical current

5

Extensibility

Normal to larger size

6

Contractility

Normal to 1/3 of size

7

Elasticity

Back to normal size

8

Muscle functions

Generate heat
Stabilize joints
Movement of bones/fluids
Posture/position

9

Skeletal muscle

Each muscle is served by one nerve, one artery, 1+ veins

10

Epimysium

Surrounds entire muscle; belly CT

11

Perimysium

surrounds fascicles Ct

12

Endomysium

surrounds each muscle fiber/ areolar ct

13

Anatomy of skeletal muscle fiber

Cylindrical, up to 30 cm
Multiple peripheral nuclei
Many mitchondria
Glycosomes
Myioglobin- takes O2 to cells
Myofibrils, SR, T-tubules

14

Myofibrils

Dense, 80% of cell volume

15

Sarcomere features

Thick filaments: Myosin (A Band)
Thin filaments: Actin (I band and partially to A band)
Zdisc: Anchors thin filaments
Hzone: Lighter midregion where there is no overlap
Mline: Holds adjacent thick filaments together

16

Myosin Tails

Two interwomen polypeptide chains

17

Myosin Heads

2 smaller polypeptide chains; crossbridges
Binding sites for actin filaments
Binding sites for ATP
ATPase enzymes

18

Sarcoplasmic Reticulum

Stores Calcium Ions

19

T-tubules

Continuous with the sarcolemma
Pentrates cell's interior at each A/I band junction

20

During contraction...

myosin heads bind to actin, detach, and bind again to propel thin myofilaments toward the M-line. Zlines move together.. A band doesn't move.

21

Requirements for skeletal muscle contraction

Activation: neural stimulation at neuromuscular junction
Excitation: Generation and propagation of an action potential along the sarcolemma
Trigger; rise of intracellular Ca levels

22

Events at neuromuscular junction

Axons of motor neurons go from CNS---> skeletal muscles via nerves. Each axon ending forms neuromuscular junction with a single muscle fiber

23

Neuromuscular junction

Midway along length of a muscle fiber.
Axon terminal and muscle fiber separated by synaptic cleft. Synaptic vessicles contain neurotransmitter Ach.
Sarcolemma contain Ach receptors

24

Events

Nerve impulse arrives at axon terminal.
ACh is released and binds with receptors on the motorr end plate of the sarcolemma. Electrical events lead to a generation of an action potential.

25

Depolarization

ACh opens chemically ligand gated ion channels. There's diffusion of Na in and K out. More Na is diffused so the sarcolemmma's interior becomes less negative.

26

Generation and Propagation of an action potential

End plate potential spreads to adjacent membrane areas. Voltage gated Na+ channels open. Na influx decreases membrane voltage towards a critical threshold. If the threshold is reached, an action potential is generated.

27

Repolarization

Na channels close and voltage gated K channels open. K efflux rapidly restores the resting polarity.
Ionic conditions of resting state restored by calcium potassium pump.

28

What happens at the peak of an action potential?

Na gates will close and K gates will open.

29

E-C Coupling (excitation-contraction)

Sequence of events of an action potential leading to sliding of the myofilaments

30

Latent period

lag time; time between initiation and contraction

31

Events of EC

Action potential is propagted along sarcomere to t-tubules
Voltage sensitive proteins stimulate release of Calcium ions from SR.

32

Role of calcium in contraction

Calcium binds to troponin, troponin moves tropomyiosin away from active sites on actin. Cross bridge occurs, when Nervous stimulation ceases, ca pumped back into SR and end of contraction.

33

Cross bridge detachment

ATP attaches to myosin head and the cross bridge detaches.

34

Cocking of myosin head

Energy from hydrolysis of ATP cocks myosin head into high energy state.