Cardiac Contraction

Question 1

skeletal muscle contraction and membrane

Answer 1

long striated cells with multiple nuclei. contraction initiated by nervous system. membrane contains receptors that stimulate contraction. acetylcholine is neurotransmitter

Question 2

smooth muscle contraction and membrane

Answer 2

long spindle shaped cells.contraction initiated by nervous system, hormones, stretch of muscle. membrane has receptors that can either stimulate or inhibit contraction

Question 3

cardiac muscle contraction

Answer 3

branching striated cells. contraction initiated by specialized cardiac cells (pacemaker)

Question 4

myofibrils

Answer 4

muscle fibers composed of these. Each one is made up of thick and thin threads called myofilaments

Question 5

myosin filaments

Answer 5

thick protein. approx. 1500 per myofibril

Question 6

actin filament

Answer 6

thin protein. 3000 per myofibril

Question 7

sarcolemma

Answer 7

plasma membrane enclosing muscle fiber. has special cytoplasm called sarcoplasm. within sarcolemma lie numerous mitochondria with large number of myofibrils running parallel

Question 8

intercalated disc

Answer 8

hold fibers together and aid of conduction from one fiber to another. unique to cardiac cells

Question 9

sarcoplasmic reticulum

Answer 9

surrounds each myofibril. network of tubes and sacs that hold mad calcium dog.

Question 10

t tubles

Answer 10

cross sarcoplasmic reticulum at right angles and communicate to outside. easy movement of action potential from exterior to interior of the cell

Question 11

sarcomere

Answer 11

fundamental unit of muscle contraction. extends from z to z line. does work son!

Question 12

I band

Answer 12

thin actin strands alone (letter I is skinny)

Question 13

Z line

Answer 13

anchor actin filaments composed of filamentous protein (z is last letter of alphabet and last part of sarcomere)

Question 14

A band

Answer 14

composed of overlapping thick myosin and thin actin myofilaments (length of myosin myofilament)

Question 15

H ZONE

Answer 15

only myosin strands

Question 16

m line

Answer 16

mid line connects adjacent myosin

Question 17

titin

Answer 17

framework for sarcomere. large protein (3,000,000 daltons). one end anchored to z disk and other is attached to myosin. (springy and changes length as muscle contracts and relaxes)

Question 18

anatomy of actin

Answer 18

strands about 1 um long. composed of 2 F- actin molecules wrapped around each other. basic unit F actin is G actin.

Question 19

g actin

Answer 19

42,000 daltons. each one has a molecule of ADP attached. site of attachment for myosin cross bridges

Question 20

tropomyosin

Answer 20

70,000 daltons, 40 nanometers long. covers active binding sites during resting phase of action potential

Question 21

troponin complex

Answer 21

holds tropomyosin in place on the actin. consists of troponin I, T, and C

Question 22

troponin I

Answer 22

strong affinity for actin

Question 23

Troponin T

Answer 23

strong affinity for tropomyosin

Question 24

Troponin C

Answer 24

strong affinity for calcium

Question 25

anatomy of myosin

Answer 25

each myosin fiber is a bundle of 200 myosin molecules. each molecule is 480,000 daltons . made of six polypeptide chains 2 heavy (200,000 daltons each) and 4 light (20,000 daltons each)

Question 26

heavy chains of myosin

Answer 26

wrapped in double helix and form the tail. one end of each heavy chain is folded to create 2 heads. (each head acts as ATPase enzyme)

Question 27

light chains

Answer 27

2 light chains attach to each head to help control action during contraction

Question 28

contraction of sarcomere

Answer 28

calcium enters cell and reacts with troponin. tropomyosin undergoes conformational shift in tropomyosin
and exposes binding sites. once actin exposed cross bridges are formed. works like oars on a boat

Question 29

myosin attached to actin at start of cycle

Answer 29

myosin head lacks a bound nucleotide and is attached to actin in a rigor state (rigid) very short lived. terminated by binding of ATP

Question 30

Myosin releases actin

Answer 30

ATP binding to cleft on back of cause conformational change in actin binding sites. reduces head’s affinity for actin and allows it to move away from actin

Question 31

hyrolysis of ATP on myosin head

Answer 31

causes cleft to close like a clam shell around ATP. triggers large shape change that causes head to move along actin about 5nm. ADP and inorganic phospahte remain on head

Question 32

myosin rebinding to actin

Answer 32

weak binding of myosin to new site releases inorganic phosphate produced by hydrolysis. head is now able to tightly bind to actin

Question 33

phosphate released- power stroke

Answer 33

the release of phosphate triggers the power stroke in which the head regains original conformation. during the course of power stroke the head loses ADP and starts cycle over (rigid again)

Question 34

muscle relaxation

Answer 34

calcium transported to SR. tropomysoin blocks actin binding sites. Z lines move further apart

Question 35

tension only

Answer 35

isometric. if muscle ends held in place max tension muscle can develop will be represented

Question 36

muscle ends free

Answer 36

isotonic (fixed tension) ability to shorten but no tension. shows max velocity of contraction

Question 37

heart develops tension to..

Answer 37

overcome given afterload then begins to shorten. both tension and velocity of shortening will be less than max

Question 38

increased contractility results in

Answer 38

developing more tension for a given resting tension (changes final muscle length not resting)

Question 39

beta 1 interaction

Answer 39

NE and Epi stimulates increased calcium influx during phase 2. increased influx loads calcium channel releases even more calcium on the next depolarizations. calcium removal rate also increases. the duration of the AP is decreased

Question 40

law of Laplace

Answer 40

T=P(R)
T=total wall tension P= intraventricular pressure R= ventricular radius
easier to produce pressure at end of ejection than at beginning. dilation plays huge role on pressure generation