exam 4- cardiovascular 1

Question 1

what is the job of the cardiovascular system?

Answer 1

to provide nutrients for metabolic activity- provide oxygen, electrolytes, and nutrients to tissues
- transport delivers nutrients & carries away all the produced waste products from the tissues

Question 2

in the cardiovascular system, transport by bodily fluids is called ___ to and from major systems of the body

Answer 2

bulk transport

Question 3

list the 4 components of the cardiovascular system:

Answer 3

1- heart (the pump): propels blood around the body

2- arterial system: distributes blood to body organs and acts as a pressure reservoir

3- capillary system: the site of transfer (exchange) of substances b/w blood & tissue (system of many small blood vessels)

4- venous system: the route of return of blood from body to heart, also serves as a volume reservoir

Question 4

cardiac muscle is considered ___ ___ muscle

Answer 4

modified skeletal

• striated (has actin & myosin), functions similar to skeletal muscle with some major modifications

Question 5

the heart is entirely made of ___

Answer 5

muscle

Question 6

describe nerves in the heart

Answer 6

nerves leading to heart but no nerves running through the heart

Question 7

instead of cardiac muscle being arranged linearly like skeletal muscle…

Answer 7

it is arranged in spiral, basket-weave arrangement (this makes cardiac muscle most complexly organized muscle in body)

Question 8

are there afferent pain receptors in the heart?

Answer 8

no afferent pain receptors running from the heart –> if heart is diseased or malfunctioning, there is no direct signal letting you know (precursors of heart attack are known as referred pain)

Question 9

describe the path of blood to the heart

Answer 9

blood returns to heart thru 2 major veins: superior vena cava (drains head & thoracic cavity) and inferior vena cava (drains abdomen & lower appendages), they bring deoxygenated blood back to heart, enter heart through right atrium –> tricupsid valve (one-way atrioventricular (AV) valve, separates right atrium from right ventricle- has 3 flaps) –> right ventricle –> pushes blood out thru pulmonary artery –> blood goes directly to lungs where CO2 is given off and oxygen is picked up (blood gets oxygenated in capillaries of lungs) –> oxygenated blood returns to heart thru pulmonary vein (only vein in body that carries oxygenated blood) –> pulmonary vein returns blood to left atrium –> bicupsid/mitral valve (left AV valve) –> left ventricle –> pumps blood out of aorta –> aorta divides into major arteries, sends blood to major metabolic tissues of the body

Question 10

name the 2 separate circulatory loops in cardiovascular system and their purpose

Answer 10

pulmonary circulation (to lung and back)
systemic circulation (to major organs systems and back)

• these 2 loops prevent the mixing of oxygenated & deoxygenated blood

Question 11

pulmonary artery is the only artery in the body that carries ___ blood

Answer 11

deoxygenated

Question 12

pulmonary vein is the only vein in the body that carries ___ blood

Answer 12

oxygenated

Question 13

as a consequence of the 2 separate circulatory loops, there’s some downstream effects

Answer 13

the heart is a functional syncytium, meaning there are 2 separate components, but it contracts at once as if it were one large muscle cell (b/c individual muscle cells communicate with each other and contract in coordinated manner, then relaxes all at once in unified manner)

• unified state of contraction of the heart is called systole, state of relaxation called diastole
• when heart contracts, generates pressure on fluid in the 4 chambers (pressure generated called systolic pressure), when relaxes, the pressure drops (lowest pressure called diastolic pressure)
• measured systolic/diastolic

Question 14

describe the different in pressure generated in the 4 diff chambers of the heart

Answer 14

1- right & left atrium (thin-walled, only have to pump blood through their AV valves into ventricles) : low pressures, 2-8 (right) and 2-10 (left) range of pressures

2- right ventricle (only pumps blood to lungs and back, pulmonary circulatory loop), right ventricle wall is relatively thin, generates relatively low pressure: systolic pressure is 15-30 (that is all that’s needed to pump blood to pulmonary circulation b/c short distance and lore resistance path)

3- left ventricle (has to pump blood through systemic circulation- long distance and high resistance path, pumps blood against gravity from heart to head): left ventricular wall is much thicker, contracts and generates much higher force, 100-140 mmHg

Question 15

pressure in heart is measured in this unit

Answer 15

mm Hg

Question 16

cardiac muscle is so thick that ie needs its own blood supply…

Answer 16

coronary arteries form extensive complex that feed blood to cardiac muscle

• cardiac muscle has high density of mitochondria, so generates ATP efficiently through oxidative phosphorylation- but need constant supply of oxygen to keep it going (O2 supplied by coronary arteries)

Question 17

what issue accompanies the fact that coronary arteries supply oxygen to the heart

Answer 17

puts heart in danger of heart attack- occurs when one of the arteries becomes blocked –> blood flow cut off and muscle cells begin to die –> patch of dead cardiac muscle fibers, disrupts ability of heart muscles to communicate and disrupts ability of heart to contract and relax as a unit –> enter fibrilation

Question 18

cardiac muscle has to contract rhythmically and continuously for a lifetime; metabolically, it is most similar to this fiber in skeletal muscle, ___

Answer 18

fast phase oxidative

Question 19

how to treat a heart attack based off if its caught early vs. late:

Answer 19

if caught early: do balloon catheterization –> expands artery and insert a stent, gives structural support and prevents artery from collapsing, restores bloodflow

if caught late when the artery is entirely blocked: do bypass (vein from leg attached to artery, restores blood flow to cardiac muscle)

Question 20

describe the effects of having a heart attack in the right vs. left ventricle

Answer 20

if have heart attack in right ventricle and 30% of cardiac muscle in RV is damaged –> can survive easily b/c right ventricle only has to pump blood to lungs and back, short distance, so even with only 70% of muscle working, can still generate enough pressure to pump blood to lungs

if have 30% damage to left ventricle –> very bad and probably fatal (a lot less tolerance b/c LV has to pump blood through long distance and high resistance path, needs all the muscle to work to accomplish this)

Question 21

what is a developing approach to treat the heart?

Answer 21

use pluripotent stem cells to grow a patch of cardiac myocytes in vitro –> transplant patch to damaged area and have healthy cardiac cells fuse with damaged cells, replacing the tissue

Question 22

describe heart worms in animals

Answer 22

heart worms happen/grow in the right ventricle b/c they are endoparasites, these parasites have evolved in an anaerobic (low oxygen) environment (and RV has deoxygenated blood)

Question 23

describe properties of the heart that classify it as modified skeletal muscle

Answer 23

striated, has sarcomeres, horizontal & vertical patterns, has lots of mitochondria

• has SR (more well-developed than smooth muscle, but not as well-developed as skeletal)
• muscle membrane of sarcolemma has voltage-gated calcium channels (diff than skeletal)
• fibers not anchored at either end, so doesn’t contract linearly, but spiral-y –> allows for greater sarcomere shortening & relaxation

Question 24

what property of cardiac muscle allows adjacent cardiac muscle cells to communicate?

Answer 24

cardiac muscle has intercalated discs- points of connection & communication b/w 2 adjacent cardiac muscle cells

• characterized partly by gap junctions, transmembrane proteins allowing direct ionic current from one cell to another
• also characterized from desmosomes- connect membranes of each cell, so that when one cell contracts, force contracts in other cell

Question 25

cardiac muscle is similar in molecular organization to skeletal muscle

Answer 25

sarcomere organization very similar (sarcomeres laid end to end in myofibrils- extensive T-tubule system)

• double helix F-actin polymer, capped off at leading end by tropomodulin, anchored at z-line by alpha-actinin
  . support by scaffold of nebulin (like skeletal muscle)
  . has troponin-tropomodulin complex masking binding sites for myosin (troponin has TnC- activated by calcium, like skeletal)
• myosin is the same- light meromyosin tail forms core; heavy meromyosin head: myosin ATPase, essential and regulatory light chains, also has C protein that acts like a M-line, runs down middle of sarcomere to keep myosin in proper orientation
  . myosin anchored to z-line by spring-like titin

Question 26

what is the pacemaker of the heart

Answer 26

SA node

Question 27

although the heart beats all together as a unit, the cell types of the heart beat at their own intrinsic rate and they are not always the same…

Answer 27

• SA node (junction b/w vena cava and right atrium) : group of modified muscle cells, can’t contract but can generate APs - discharge at 70 beats/min (measured in pulses/min b/c can’t really contract)
• atrial muscle cells: 40 beats/min
• ventricles: 25 beats/min

but all together, intact heart beats at 70 beats/min, the pace is set by the fastest-beating cells of the SA node (pacemaker of heart), causes other cardiac muscle cells to depolarize prematurely and contract at the faster rate

Question 28

the heart is ___, AP that starts contraction originates in muscle itself

Answer 28

myogenic

Question 29

how does the SA node depolarize?

Answer 29

• SA node generates spontaneous depolarization & spontaneous AP (identical to myogenic nature of smooth muscle membrane) - goes from -60 mV (resting) to threshold
• no steady muscle contraction –> funny sodium channels, slowly leaking sodium in to depolarization & closer to threshold
• when get closer to threshold, recruits T-type (transient) calcium channels - further depolarizes membrane
• when reach threshold, activates L-type calcium channels –> responsible for wave of depolarization of AP
• calcium current is a little slower than the typical-voltage gated, goes to about +20 mV –> at peak, L-type calcium channels close and typical voltage-gated potassium channels open and repolarize membrane
• called a “slow-response AP”
• the pacemaker potential (SA node potential)- pacemaker potential starts in SA node and spreads to membranes of other cells, causing them to depolarize pre-maturely, causes whole heart to contract simultaneously

Question 30

in the other cardiac myocytes (other than SA node), what is the resting potential and why?

Answer 30

resting potential is -90 mV b/c in cardiac muscle membranes, the permeability of K+ is 100 times greater than permeability of sodium (not 30 x greater)

• at rest, for every 1 sodium that diffuses in, 99 sodium diffuse out –> brings membrane potential to actual equilibrium potential of K+ (-90 mV)

Question 31

AP is generated on the other cardiac myocytes (as opposed to SA node) differently

Answer 31

4 phases:
- phase 4: equivalent to rest (at beginning & end), not stable resting potential b/c inward funny sodium and outward K voltage-gated channels (K diffusion masks funny sodium b/c K+ much faster (permeability is 100x greater), keeps resting near -90 mV

• phase 0: activation of traditional voltage-gated sodium channels (activated from AP from SA node), this is what causes steep and rapid wave of depolarization (from -90 to +20), open quickly and close quickly –> Na channels deactivate
• as potential approaches 0, recruits L-type calcium channels (inward calcium helps with steep wave of depolarization)
  . once L-type opens, they close very slowly (stay open long time) –> no rapid repolarization, longer period where membrane of muscle cells stay depolarized
  . 2 opposing forces working during phase 1: inward depolarizing calcium, but also around +20, begin to open outward repolarizing K+ channels (max overshoot lasts ~300 ms)
• during plateau phase (phase 2), 2 opposing forces balance each other, get max plateau of overshoot –> after 300 ms and end of phase 2, calcium channels close and K+ causes repolarization
• phase 3: only K+ open and repolarize back to -90 mV

Question 32

explain the rectifying K+ current

Answer 32

inward rectifying K+ current (rectifying means “compensating for”- compensates for inward sodium current

• at +20 mV, specific K+ channel opens and causes an early repolarization, brings potential back down to 0, (transient K+ channels), open quickly and then close … at same time, L-type calcium open- large increasing inward movement of calcium, keeps membrane depolarized (these 2 balance out)
• begin to open delayed rectifying K+ channels, 2 types: Ks (slow) and Kr (rapid) - these tend to repolarize the membrane … at same time, inward rectifying K+ channels (K1) allow some K+ to flow “backwards” across the membrane, contributing to depolarization - this inward current compensating for outward current, this is like a typical voltage-gated K+ channel, but it does something weird:
  . initially, K+ moves out, but this drags with it- magnesium & polyamines which blocks/stops any more K+ from moving out (so this current allows for backflow of K+, but only a little)

Question 33

during depolarization in cardiac myocytes other than SA node, at the end of phase 2, ____ channels close and ___ channels open full blast (…)

Answer 33

L-type calcium close
K channels (K1 channels reverse again and allow outward movement of K+)

Question 34

during depolarization in cardiac myocytes other than SA node, in phase 3, ___ channel open and allow…

Answer 34

3 types of K+ channels open, allow outward rapid movement of K+ (delayed rectifying- Kr and Ks) and K1 (now again allowing outward K+ diffusion)

Question 35

during depolarization in cardiac myocytes other than SA node, in phase 4, at rest, the ___ channel dominates

Answer 35

outward K1 channel

Question 36

when the K1 channel is open and moves K+ out and drags magnesium & polyamines with it, what else can do this?

Answer 36

intracellular spermine, spermidine & putresceine can also cause rectification like magnesium

Question 37

how long does complete cycle of contraction and relaxation last in cardiac myocytes?

absolute refractory period

Answer 37

AP has steep wave of depolarization, then plateau and repolarization (whole thing takes about 300 ms)
- cardiac muscle cell membrane has absolute refractory period of 300 ms ( ventricular contraction & relaxation is also 300 ms) –> so strict 1:1 relationship of AP and complete cycle of contraction and relaxation (cannot stimulate muscle to contract again until AP is over)

• no temporal/wave summation in cardiac muscles (also no tetany)

Question 38

mechanism of contraction in cardiac muscle is a hybrid of ___ and ___ muscle

explain

Answer 38

smooth & skeletal

AP travels along cardiac muscle membrane- activates voltage-gated calcium channels (activation of sarcolemma calcium channels –> calcium-induced-calcium release, calcium sparks add together and produce calcium signal –> calcium binds troponin and disinhibits actin filament, and activates myosin ATPase –> contraction

• relaxation occurs when calcium cleared from cytoplasm (SERCA pumps calcium back into SR … at same time, calcium-sodium exchange protein that moves calcium out and sodium in –> sodium gradient established by sodium pump, large gradient on outside –> sodium then comes in which pushes calcium out