Skeletal Muscle

Question 1

T-tubule

Answer 1

deep invaginations of sarcolemma; extend into sacroplasm

Question 2

sacromere

Answer 2

the functional contractile unit in a skeletal muscle fiber

Question 3

The sarcomere is defined by the area between

Answer 3

2 adjacent Z discs

Question 4

myofibrils

Answer 4

composed of short bundles of myofilaments

Question 5

Myofilaments are of 2 types

Answer 5

actin and myosin

Question 6

Individual actin molecules

Answer 6

G-actin (globular actin monomers)

Question 7

Strands of actin molecules

Answer 7

F-actin; filamentous actin polymers

Question 8

two primary regulatory proteins are also part of the thin filaments

Answer 8

tropomyosin, troponin-C

Question 9

Myosin heads form crossbridges…

Answer 9

with actin thin filaments during contraction

Question 10

sliding filament theory

Answer 10

thin filaments slide across thick filaments toward the center of the sacromere (shortening of the H zone and I zone, A band does not change, Z-lines move closer together)

Question 11

explain the molecular basis of muscle contraction (in relation to ADP Pi, ATP)

Answer 11

myosin heads contain bound ADP and Pi (weak affinity for actin), when 1 of the myosin heads stops on the actin subunit- Pi is released which binds myosin to actin +triggers force stroke that moves the actin filament, ADP dissociates, ATP forms and binds to the anti-nucleotide binding site, myosin head deteched from actin; ATP is hydrolyzed

Question 12

explain the molecular basis of muscle contraction (in relation to ca2+ and tropinin)

Answer 12

ca levels rise, ca binds to troponin, troponin-C moves tropomyosin away from actin’s myosin binding site and myosin and actin bind strongly and creates powerstroke, actin filaments move

Question 13

what is DHPR?

Answer 13

An L-type Ca channel that detects voltage

Question 14

In skeletal muscle, when DHPR is activated, what does it do?

Answer 14

It opens RyR

Question 15

What is RyR

Answer 15

RyR is a calcium channel in the sarcoplasmic reticulum

Question 16

is cardiac muscle neurogenic or myogenic?

Answer 16

myogenic: the cells within the heart muscle itself are dictating where/when/how the cardiac muscle contracts

Question 17

pacemaker cells

Answer 17

modified muscle cells whose job is to set the pace

Question 18

In cardiac muscle, is the L-type calcium channel real or is it voltage gated

Answer 18

it is a real calcium channel

Question 19

In cardiac muscle, what activates RyR?

Answer 19

calcium from the L-type calcium channel (calcium induced calcium release)

Question 20

In cardiac muscle what do the SERCA and PMCA pumps do

Answer 20

pumps Ca out against its gradient (relax muscle)