Skeletal Muscle

Question 1

Z disk

Answer 1

Delineate the sarcomere

Question 2

I bands

Answer 2

Think filaments anchored to Z lines, do NOT include overlap

Question 3

A band

Answer 3

(Anisotropic-directionally dependent) Thick filament. DOES include overlapping portion

Question 4

H band

Answer 4

Only thick filament area

Question 5

M lines

Answer 5

Middle of h band. Denmark reversal of myosin head

Question 6

Contraction changes in sarcomere

Answer 6

H-zone becomes super small, and I band is much shorter

Question 7

Titin

Answer 7

Connects Z line to M line of sarcomere. Acts as molecular spring

Question 8

Dystrophin

Answer 8

Forms a rod connecting the actin filaments to the transmembrane. Provides scaffolding. Disruptions of this structure lead to muscular pathologies

Question 9

T-tubules

Answer 9

Adjacent to terminal cisternae of sarcoplasmic reticulum. Form triads. Arrangement allows rapid spread of impulses

Question 10

Membrane potential of skeletal muscle

Answer 10

~-90mV

Question 11

What are skeletal muscles innervates by?

Answer 11

Alpha motor neuron

Question 12

Neurotransmitter that causes action potential in sarcolemma

Answer 12

Acetylcholine

Question 13

Triad

Answer 13

T tubule lumen, 2 cisternae

Question 14

Receptor opened in the terminal cisternae of SR

Answer 14

RyR (ryanodine receptor)

Question 15

What leaves the SR, thus initiating the contraction process?

Answer 15

Ca++

Question 16

SERCA

Answer 16

SR or ER Ca2+ ATPase.

Starts pumping Ca 2+ into the SR immediately.

Question 17

Binding site for Ca2+

Answer 17

Troponin C

Question 18

What covers the binding site for myosin?

Answer 18

Troponin I

Question 19

What is bound to the “cocked” form of the myosin head?

Answer 19

ADP and Pi

Question 20

What causes myosin to disconnect from the actin?

Answer 20

ATP

Question 21

How are the velocity of muscle shortening and initial load related?

Answer 21

Inversely

Question 22

Relationship between sarcomere length and power of contraction

Answer 22

Length must be optimal or shortening cannot happen

Question 23

Isometric contraction

Answer 23

No external shortening. Load exceeds the ability to create tension

Question 24

Isotonic contraction

Answer 24

External shortening, the load is less that the ability to create tension

Question 25

Eccentric contraction

Answer 25

Contraction with external lengthening, while contracting, the muscle lengthens

Question 26

Increase frequency of muscle stimulation

Answer 26

Summation of contractions results in greater contractile force. The Ca from previous stimulation doesn’t completely go away.

Question 27

Complete tentany

Answer 27

The muscle has reached full contractile capacity

Question 28

Passive tension

Answer 28

Muscle is stretched from an unstretched length or passive tension increases as a function of a muscle length

Question 29

Active tension

Answer 29

Muscle contracted at sarcomere length that allows peak tension

Question 30

Total tension

Answer 30

Total tension generated by muscle contraction at any given muscle or sarcomere length is the sum of passive and active tensions

Question 31

Motor unit definition

Answer 31

Single alpha motor neuron and all muscle fibers it innervates

Question 32

Slow twitch fibers

Answer 32

Type I muscle fibers. Oxidative. Small diameter. Fine control

Question 33

Fast twitch Type IIA

Answer 33

Oxidative-glycolytic. Moderate muscle fiber diameter.

Question 34

Fast Twitch Type IIB

Answer 34

Glycolytic. Large muscle fiber diameter. Coarse control

Question 35

Improving the oxidative properties of fast twitch fibers does what?

Answer 35

Improves how long the fiber can fire