Lecture 18 Muscle Physiology Flashcards Preview

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Flashcards in Lecture 18 Muscle Physiology Deck (16)
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1

Types of muscle

skeletal- striated, voluntary
cardiac- striated, involuntary
smooth- nonstriated, involuntary

2

Levels of structure

muscle
fascicle- bundle of muscle fibers
muscle fiber (=cell)
myofibril- bundle of protein filaments w/in the muscle fiber
myofilaments - thick(myosin) & thin (actin)

3

Muscle bone joint systems

muscle actions (flexion & extension)
agonist
antagonist

4

Sarcomere

functional unit of muscle contraction
A band, I band, Z disk, H zone, M line

5

Thick filaments

mysoin bundles
myosin head - forms crossbridges with thin filament
actin binding site
ATP binding site

6

Thin filaments

actin chains (F-actin)
myosin binding sites
regulatory proteins: tropomyosin & troponin
twice as many as thick

7

Sarcolemma

plasma membrane of muscle fiber
forms muscle action potentials

8

T tubules

invaginations of sarcolemma
carry APs deep into the muscle fiber
contain extracellular fluid

9

sarcoplasmic reticulum (SR)

intracellular membrane system, stores Ca2+ terminal cisterns

10

terminal cisterns

enlarged ends of SR, in close contact with T tubules

11

Sliding filament mechanism

thin filaments slide across thick filaments toward the center of the sarcomere
thick and thin filaments do not change in length, only in extent of overlap

12

During the contraction of the sarcomere

A band remains constant
I band and H zone shorten
Z disks move closer together

13

Contraction-Relaxation cycle

Ca+ is released from SR and binds to troponin then;
1. Myosin head binds to actin - forms crossbridge
2. power stroke - myosin head rotates, Pi and ADP are released
3. ATP binds to myosin - releases crossbridge (releases actin)
4.ATP hydrolysis - energizes myosin head; ADP and Pi are still attached to myosin

14

relaxed muscle

myosin heads energized (stage 4) but A-M binding sites blocked

15

Rigor state

myosin heads stuck to actin; ATP is required for crossbridges to detach

16

Functions of ATP

detaches myosin head
cocks myosin heads