week 5 (CV)

Question 1

explain: stages of the cardiac cycle

Answer 1

1. start
   - blood enters atria
   - atria contracts
2. atrial systole
   - atria contracts -> pushes blood to ventricles
   ⤷ AV valves open
3. atrial diastole
   - atria relaxes
   ⤷ fills with blood but not contracting
4. ventricular systole (isometric contraction)
   - AV valves close, semilunar close -> closed system
   - psi increases but blood V no change
5. ventricular systole (ventricular ejection)
   - semilunar valves open
   - blood ejects
6. ventricular diastole early
   - semilunar valves close
7. isometric relaxation
   - psi decreases
   - no blood flow to ventricle
8. ventricular diastole late
   - AV valves open
   - blood passively flows into atria

Question 2

define: cardiac cycle

Answer 2

• period between start of one heartbeat and the beginning of the next
• all stages must happen in each cycle

Question 3

define: systole vs diastole

Answer 3

• systole = contraction period
• diastole = relaxation period

Question 4

question: what is the movement of blood in areas of varying pressure?

Answer 4

• moves from area of higher to lower pressure

Question 5

question: which ventricle has more blood?

Answer 5

• exactly the same
• destinations and psi are different but quantity is same

Question 6

define: pacemaker cells

Answer 6

• specialized cells that determine the rate at which the heart beats
• innervated by SNS and PSNS
• spontaneously generate AP

Question 7

define: myogenic vs neurogenic

Answer 7

• myogenic = heart can do rhythmic contractions on its own
• neurogenic = contract only in resp to neural stim.

Question 8

name + explain: steps of a pacemaker cell AP

Answer 8

1. slow depol.
   - funny Na+ channels open
   - slowly drift to threshold
2. rapid depol.
   - reaches threshold (-40mV)
   - Ca rushes in
   - triggers AP
3. repol
   - Ca+ channels close
   - K+ channels open to let K+ out
   - returns to starting state

Question 9

define: conduction fibers

Answer 9

• internodal fibers
• conduct AP very fast

Question 10

define: contractile fibers (cardiac myocytes)

Answer 10

• interconnected through gap junctions
  ⤷ spreads AP
• has aspects of skeletal musc. and smooth musc.

Question 11

explain: steps of cardiac musc. cell contraction (steps of AP)

Answer 11

1. rapid depol
   - Na+ open
   - rush of Na+ influx
2. plateau
   - membrane potential stays near 0mV
   ⤷ bc fast Na+ channels close pumping Na out
   ⤷ bc slow Ca+ channels open allowing Ca in
3. repol
   - slow Ca+ close
   - slow K+ open, K+ rushes out
   - restores resting

Question 12

explain: electrocardiogram readings (parts of the graph)

Answer 12

• P wave = atrial depol.
• QRS complex = ventricular depol. and atrial repol.
• T wate = ventricular repol.

Question 13

define: stroke V

Answer 13

• amount of blood pumped out of each ventricle in a single heart beat

Question 14

define: EDV and ESV

Answer 14

• end diastolic volume = amount of blood in ventricle at the end of ventricular diastole
• end systolic volume = amount of blood in ventricle at end of ventricular systole

Question 15

name: factors affect heart rate and stroke V

Answer 15

HEART RATE
- autonomic innervation
- hormones

STROKE VOLUME
- EDV
- ESV

Question 16

question: how do venous return, filling time, and preload affect stroke volume?

Answer 16

• increase the factor = increase the stroke V

Question 17

define: venous return, filling time, preload

Answer 17

• venous return = amount of blood delivered to right atrium by vena cava
• filling time = duration of ventricular diastole
• preload = amount of myocardial stretching

Question 18

define: SA node

Answer 18

• small group of specialized cells in the right atrium
• creates heartbeat
• pacemaker

Question 19

question: how do SNS and PSNS affect heart rate (autonomic control)?

Answer 19

• hormones
• SNS -> cardiac nerve -> norepi -> acts on beta1 receptors in SA node -> increases heart rate
• PSNS -> vagus nerve -> ach -> acts on muscarinic receptors in SA node -> decreases heart rate

Question 20

question: how does the SNS increase heart rate?

Answer 20

• release of norepi increases Na+ and Ca+ influx
• more AP freq.

Question 21

question: how does PSNS decreases heart rate?

Answer 21

• Ach increases K+ permeability
  ⤷ cell more negative -> takes longer to reach threshold -> slower AP rate

Question 22

question: relationship between EDV and ESV and stroke V?

Answer 22

EDV increase SV increase (vv)
⤷ proportional

ESV increase SV decrease (VV)
⤷ inversely proportional

Question 23

explain: methods of capillary exchange of nutrients (4)

Answer 23

1. diffusion
   - lipid soluble substances
   - diffuse through mem.
2. mvt through intercellular clefts
   - water soluble substances
3. mvt through fenestrations
   - water soluble substances
   - fenestration type dep. on where the capillary is
4. transport via vesicles
   - larger substances

Question 24

define: CHP, BCOP, NFP

Answer 24

• CHP = capillary hydrostatic psi = psi of the fluid
  ⤷ pushes water and solutes out of capillaries
• BCOP = blood colloid osmotic psi = psi coming from solute conc. of blood
  ⤷ pulls water and solutes into capillaries
• NFP = net filtration psi = no net fluid mvt.

Question 25

explain: differences in filtration and absorption pressures

Answer 25

- blood into arteriole FILTRATION - low CHP = 35mm/Hg - BCOP = 25mm/Hg - higher solute conc. in blood than tissue ⤷ but CHP still greater than BCOP - CHP > BCOP -> fluid forced out of capillaries and into tissue NFP = 0 ABSORPTION - even lower CHP = 18mm/Hg - BCOP = 25mm/Hg - BCOP > CHP -> fluid moves into capillaries blood out through venule