Neuromuscular Physiology

Question 1

sarcolemma

Answer 1

myofibre plasma membrane

Question 2

sarcoplasm

Answer 2

myofibre cytoplasm

Question 3

myocyte

Answer 3

muscle cell with one nucleus

Question 4

myofibre

Answer 4

multinucleated muscle cell

Question 5

T/F each myofibre spans the length of the muscle

Answer 5

T

Question 6

each myofibre has at least ___ neuromuscular junction

Answer 6

one

Question 7

myofibres contain ___________, which are bundles of _____________, made up of the contractile proteins _______ and _______-

Answer 7

myofibrils; myofilaments; actin and myosin

Question 8

what connects myosin to the Z disc

Answer 8

titin filament

Question 9

what is the region between two Z lines

Answer 9

sarcomere

Question 10

where are T tubules located

Answer 10

wrap around each myofibril at the Z disc

Question 11

where is the sarcoplasmic reticulum

Answer 11

between the T tubule and the surface of the myofibril

Question 12

describe the structure of myosin filaments

Answer 12

each myosin protein is a homodimer with 2 head groups; many myosin homodimers come together to form a thick filament with many head groups

Question 13

what are thin filaments composed of (3)

Answer 13

actin, tropomyosin; troponin

Question 14

____ actin consists of chains of ____ globular actin

Answer 14

F; G

Question 15

what hides the binding sites for myosin on actin

Answer 15

tropomyosin

Question 16

what has a high affinity for Ca

Answer 16

troponin

Question 17

what happens to thin filament in the presence of ca

Answer 17

ca binds troponin -> troponin rotates, moving tropomyosin and exposing the active site on actin -> actin binds myosin

Question 18

what is the NT for a neuromuscular junction? what is its receptor

Answer 18

Ach; nicotinic AchR

Question 19

what does Ach binding trigger

Answer 19

influx of Na and local depolarization at the MEP

Question 20

where does MEP depolarization spread

Answer 20

into T-tubules; stimulates Calcium-triggered calcium release

Question 21

what happens once the AP reaches the t-tubules

Answer 21

voltage gated Ca channels detect depolarization -> tug on RYR in SR membrane

as an end result, get influx of Ca from both ECF (via Ca channels in the t-tubule) and from the SR (via RYR)

Question 22

describe the ratchet theory of contraction

Answer 22

myosin head group ATPase cleaves ATP-ADP -> head tilts -> power stroke -> new ATP binds -> actin released -> ATP cleaved into ADP -> etc.

Question 23

why is creatine important

Answer 23

stored in muscle; converted to phosphocreatine by CK; metabolized to provide phosphate bonds when the muscle needs energy

Question 24

describe sources of ATP in muscles over time

Answer 24

1. phosphocreatine (rapid early contractions for ~30s)
2. glycolytic (~1 min)
3. anaerobic

Question 25

white or fast twitch

Answer 25

short contraction times; larger size and more extensive SR; anaerobic metabolism

Question 26

red or slow twitch

Answer 26

long contraction times; smaller size and less extensive SR; aerobic metabolism

Question 27

what is responsible for calcium removal after muscle contraction

Answer 27

PMCA, SERCA

Question 28

visceral sm

Answer 28

single unit; connected via gap junctions; controlled by local stimuli; spontaneous slow waves that trigger AP

Question 29

multiunit sm

Answer 29

controlled by nervous stimulation (Ach or NE); APs or decremental depolarizations cause contracion

Question 30

example of visceral sm

Answer 30

enteric NS signalling for peristalsis

Question 31

example of multiunit sm

Answer 31

piloerector muscle, ciliary muscle