Muscle Physiology - Thomason

Question 1

Major proteins in Thin filaments?

Answer 1

Actin, Troponin, Tropomyosin

Question 2

Which thin filament protein has 3 components? What are they?

Answer 2

Troponin; C, T, & I

Question 3

Which troponin subunit binds to tropomyosin?

Answer 3

T subunit

Question 4

Which troponin subunit binds to calcium?

Answer 4

C subunit. Think C for Cockkkk…i mean calcium

Question 5

Troponin subunit I. Whats its purpose?

Answer 5

keeps troponin complex in a position so that without calcium, tropomyosin will cover myosin binding site on actin

Question 6

Describe structure and purpose of actin?

Answer 6

Fibrous helical chains that has a high affinity binding site for the myosin head (of thick filament)

Question 7

Tropomyosin is a fibrous protein that extends along ____ (thick or thin) filament to cover _____ binding sites on ____?

Answer 7

thin filament, myosin, actin

Question 8

Thick filament component?

Answer 8

Myosin…good good

Question 9

Where is the cell bodies of skeletal muscle motorneurons found?

Answer 9

Ventral horn of spinal cord

Question 10

Relationship b/t muscle fibers and motor neurons?

Answer 10

Each muscle fiber receives innervation from only one motorneuron

Question 11

Clicker question. Motor neuron acts as the final common pathway for motor unit activation b/c ___?

Answer 11

It integrates excitatory and inhibitory inputs

Question 12

T/F. Muscle fibers within a motor unit produce an all or none contraction?

Answer 12

True

Question 13

Specific type of receptor found on motor end plate of skeletal muscle? Activated via what neurotransmitter?

Answer 13

Nicotinic M receptor, activated via Ach

Question 14

Nicotonic M receptors in motor end plate of skeletal muscle are what type of channel? Importance of this?

Answer 14

Monovalent cation channels, activatation of these channels will generate a GRADED depolarization. A sufficient # of receptors must be activated in order to bring the surrounding membrane above threshold for an action potential, activating the voltage gated Na+ channel that reside in the surrounding membrane

Question 15

Release of Ach into NMJ requires what cation?

Answer 15

Ca2+ mediated Ach release. Action potential comes down axon, triggers influx of calcium, which will cause Ach vesicles to fuse, releasing Ach into NMJ

Question 16

Depolarization of T-tubule membrane to the release of Ca2+ from sarcoplasmic reticulum. Walk me through it.

Answer 16

• Depolarization of T-tuble membrane causes a conformational change in dihydropyridine receptor
• This change activates ryanodine receptor (a Ca2+ channel) in the SR, releasing Ca2+ out of the SR

Question 17

Once cell membrane repolarizes, walk me through Ca2+ path

Answer 17

Following repolarization of cell membrane, the dihydropyridine receptor returns to its resting confirmation, and the ryanadine receptor closes. Then Ca2+ is pumped back into SR via Ca2+ channel (active transport)

Question 18

If someone’s ryanodine receptors remained open (as a result of a poison), what muscle feature would occur?

Answer 18

Muscle cramps, if chronic exposure, person will die. bc diaphragm will stop working. diaphragm it be a muscle. crazy. i know right. we should do this more often. send us your email. name that movie

Question 19

Ans to “name that movie”

Answer 19

Role models.

Question 20

hypothyroidism and its effects on calcium?

Answer 20

Slows calcium uptake by SR, causing slow muscle relaxation

Question 21

Clicker question. Myosin cross bridge cycling occurs when ____ binds to ____ and causes _____ to move?

Answer 21

Troponin C binds to Ca2+ and causes tropomyosin to move

Question 22

The power stroke occurs when (ADP or ATP) is solely bound to myosin head?

Answer 22

ADP

Question 23

At optimum length, the passive tension of a muscle is what?

Answer 23

nearly zero. Main purpose of passive tension is to ensure that muscle operates at an optimal length

Question 24

Comparing 2 motor units, if one reaches peak isometric twitch tension faster, you know this is a ?

Answer 24

fast motor unit. speed at which a motor unit reaches peak isometric twitch tension is indicative of the type of motor unit it is (fast or slow)

Question 25

Name the 2 ways to produce more force by a muscle (graded contraction)?

Answer 25

1. Recruit more motor units
2. Increase the frequency of motor unit contraction

Question 26

If slow motor units aren’t producing enough force, what will occur? Relate this to frequency

Answer 26

If slow motor units aren’t producing enough force, fast motor units will be recruited. However, the slow motor units are contracting at a greater frequency (essentially theyre maxed out. thats why fast motor units had to come help out)

Don’t forget the 2 ways to increase force of contraction

1. Increase the frequency of motor unit contraction (which the slow motor unit did)
2. Recruit more motor units (which is why the fast ones showed up)

Question 27

Twitch vs tetany. Which occurs first

Answer 27

Twitch = 1st contraction that occurs.

Tetany = contraction at which muscle is producing maximal force. cant work anymore.

Question 28

Fast motor units have (more or less fibers)? The diameter of these fibers is (smaller or larger)?

Answer 28

Fast motor units = more fibers at larger diameters

Question 29

Slow twitch vs fast twitch. Which has more mitochondria?

Answer 29

Slow twitch

Question 30

Slow twitch vs fast twitch. Which has more blood vessels?

Answer 30

Slow twitch, need to deliver O2 to mitochondria (via dablood)

Question 31

Slow twitch vs fast twitch. Which has greater myosin ATPase activity?

Answer 31

Fast twitch. Myosin heads split ATP more quickly, thus faster contraction

Question 32

Oxidative Phosphorylation. Slow or fast twitch?

Answer 32

Slow twitch

Question 33

Glycogen as source of energy. Slow or fast twitch?

Answer 33

Fast twitch.

Question 34

Order of muscle use (slow oxidative vs fast oxidative/glycogenolytic vs fast glycogenolytic)

Answer 34

1st - slow oxidative

2nd - fast oxidative/glycogenolytic

3rd - fast glycogenolytic