Muscle Contraction Flashcards Preview

Skin MS: Week 4 > Muscle Contraction > Flashcards

Flashcards in Muscle Contraction Deck (35):
1

What kind of receptor does skeletal muscle have?

Nicotinic

2

Motor nerves release ____

acetylcholine

3

The acetylcholine-nicotinic receptor interaction results

in the nicotinic receptor opening as a sodium channel

4

Skeletal muscle depolarization causes activation of __________

L calcium channels (dihydropyridine receptors)

5

Calcium entry into muscle releases calcium from intracellular storage sites (sarcoplasmic reticulum) via ___________

calcium-induced calcium release (ryanodine receptors - physically coupled, don't actually need Ca to go into cell)

6

Elevated intracellular calcium concentrations result in _______

calcium binding to troponin C

7

calcium binding to troponin C
----> ____________

releases inhibition of actin-myosin interactions

8

______ heads then contact ________ to create muscle shortening and force generation, provided ________ is present

Myosin - actin
Requires ATP

9

acetylcholinesterase

breaks down acetylcholine into choline and acetate to stop signal

10

______ indicate borders of sarcomere

Z lines indicate borders of sarcomere

11

Muscle __ band remains same size but ____ bands decrease in width

A band
I band

12

Power stroke occurs as a result of _______

Release of Phosphate after cleaving ATP --> ADP + Pi which cocked the myosin head

13

When is ADP released during muscle contraction?

During/because of power stroke

14

_______ allows myosin head to be released from actin

Binding of ATP

15

Amyotrophic lateral sclerosis

degeneration of motor neurons

16

Lambert-Eaton syndrome

antibodies against Ca channels in motor neurons resulting in inability to release Ach

17

Botulism toxin

prevents Ach release by cleaving synaptic associated proteins (SNAPs)

18

Myasthenia gravis

autoantibodies against nicotinic receptors in skeletal muscle

19

Malignant hyperthermia

caused by mutation of ryanodine receptor allowing excessive release of Ca - usually triggered by anesthetics

20

Duchenne's muscular dystrophy

mutation in dystrophin, skeletal muscle support protein

21

Pesticides and nerve gases

Pesticides and nerve gases are anticholinergics (acetylcholinesterase inhibitors) → overstimulation of nicotinic receptors

22

Amount of force generated by muscle directly proportional ______

to number of actin-myosin crossbridges per cross-sectional area

Work best when considerable overlap between actin and myosin
Stretched muscle → actin/myosin no longer interacting → no strength
As shorten muscle → actin and myosin interacting, force increases linearly
Maximal point - maximal # cross bridges (no more in center)
If go past that - disordered by no more cross bridges

23

Force-velocity relationship

Muscles contract most rapidly when there is no load on the muscle

24

Isotonic contraction

Load on muscle is constant

25

Isometric contration

Load is larger than muscle's ability to move it (shorten tendon, but can't move bony attachment)

26

Type I muscle Fiber

Slow twitch
Slower myosin ATPase enzyme
High proportions in distance runners or in postural muscles (soleus)
Contain lots of myoglobin → “Red Fibers”
Need myoglobin because they require a lot of oxygen to maintain contractions

27

Type II muscle fiber

High proportions in extraocular muscles of eye
Faster myosin ATPase
White fibers (less myoglobin)
Anaerobic metabolism

28

Concentric contractions

Muscle contracts resulting in shortening
Typical biceps curl in weightlifting

29

Eccentric contractions

Muscle lengthens while attempting to shorten
Much more damage to muscle with this type of contraction
Running downhill (trying to contract while stretching)

30

Muscle conduction to contraction

AP depolarization opens presynaptic VG Ca channels inducing NT release --> Postsynaptic ligand binding leads to muscle cell depolarization in motor end plate --> depolarization travels along muscle cell and down Ttubule --> Depolarization at Voltage-sensitive DHP receptor, mechanically coupled to ryanodine receptor on SR, induced conformational change causing Ca release from SR --> release Ca binds to troponin C causing conformational change that moves tropomyosin out of myosin-binding groove on actin filaments --> myosin releases bound ADP and Pi - displacement of myosin on actin filament (power stroke) --> binding of new ATP molecule causes detachment of myosin head from actin filament, hydrolysis of ATP to ADP + Pi cocks head

31

Contraction of muscles results in what of bands

H and I bands shorten between Z lines (HIZ shrinkage)
A band is Always same length

32

Darker regions contain ______
Lighter regions contain ______

dark - myosin
lighter - actin

33

Motor neurons release _____

acetylcholin

34

Cardiac muscle has ___ channels, more reliant on

L channels, ca-induced-ca-release (not physically coupled)

35

Smooth muscle contraction controlled by

Ca interacting w/ calcium dependent myosin light chain kinase