reregulation of cardiac output

Question 1

what is cardiac output regulated by

Answer 1

• preload
• afterload
• HR
• contractility

Question 2

what is the definition of coupling factors

Answer 2

involve the functional coupling of the heart and blood vessels

Question 3

what are the two coupling factors and define them

Answer 3

• preload- the initial stretching of a single myocyte prior to contraction
• after load- is the pressure that the chambers of the heart are working against

Question 4

during afterload, what pressures is the heart working agaisnt

Answer 4

• ventricles must generate enough pressure to open the aortic and pulmonary valves due to the aortic pressure in the left ventricle and oulmonary artery pressure in the right ventrcile

Question 5

whats the definition for cardiac factors and what are they modulated by

Answer 5

• cardiac factors are intrinsic to the heart and are modulated by neural and hormonal stimulation

Question 6

what are the two cardiac factors

Answer 6

• heart rate- number of action potentials or cardiac cycles per unit time
• contractility- the intrisic ability of the heart to contract, independent of preload and afterload

Question 7

what is intropy and what is it determined by

Answer 7

synonymous with contractility and is determined bu calcium levels in cardiomyocyte cytoplasm

Question 8

what does the pressure volume loop depict

Answer 8

changes in ventricular pressure and volume during one cardiac cyle

Question 9

the PV loop can demonstarate how changes in _____,_____, and ______ can affect the cardiac cyle

Answer 9

preload, afterload, and contractility

Question 10

what is preload

Answer 10

stretching force that sets the muscle length just prior to the onset of contraction

Question 11

what determines preload

Answer 11

the passive stretch of the left ventricle at the end of filling

Question 12

what volume is is preload determine by

Answer 12

EDV determined by venous return

Question 13

what factors affect prelaod

Answer 13

• Vascular resistance ( arteriolar, vappilary, venous resistance)
• venous capcitance ( volume of blood in the venous circulation
• ventricular filling time

Question 14

how can preload be determined clinacally

Answer 14

by measuring
- right ventricylar preload
- right atrial pressure
- central venous pressure

Question 15

what relationship does each ventricular contraction work to maintain

Answer 15

Venous retturn= CO

Question 16

what is the frank starling relationshop

Answer 16

• based on the length tention relationship of a single cardiac cell
• the volume of the blood ejected by the ventricle depends on the volume of blood present in the ventricle at teh end of diastole

Question 17

what happens to EDV and SV when venous return increases

Answer 17

they increases

Question 18

until when does the linear relationship between EDV and SV volume remain linear

Answer 18

until high levels of EDV are reached

Question 19

what factors affect afterload

Answer 19

1) the volume of blood in the arterial circulation
2) the pressure in the aorta at the onset of ejection
3) the complaince of the aorta
4) the size of the aortic valve

Question 20

what happens when the afterload ( aortic pressure) is increased(2)

Answer 20

1. The pressure against which theventricle contracts is much greater
2. The larger pressure increases the resistance to the ejection of blood so:
   * more blood remains in the left
   ventricle
   * higher end-systolic volume (ESV)

Question 21

what happens when an increased afterload persists

Answer 21

the heart compensates under these condition
by increasing the EDV to maintain a normal
stroke volume.

Question 22

what do changes to contractility involve

Answer 22

involve contractile proteins and alter cardiac performance

Question 23

what do changes in contractility directly correlate to

Answer 23

correlate to intracellular ca concentration during excitation and contraction coupling

Question 24

how can contractility be increased and decreased

Answer 24

• sympathetic stimulation
  > epineph/norepineph
• postive ionotropic drugs
  > digitalis ( Na/K ATPase blocker)
• negative inotropic drugs

Question 25

what are the negative inotropic drugs

Answer 25

• toxins
• general anesthetics
• Ach
  -B-adrenergic blocking drugs (propanalol)

Question 26

what happens when contractility is enhanced

Answer 26

• The heart is able to increase the force and pressure generated during systole, leading to the ejection of a larger blood volume from the ventricles
• There is a shift in the active tension curve to the left

Question 27

what do postive and negative ionotropic drugs do to contractility

Answer 27

• postive ionotropic drugs increase contratility
• negative ionotropic drugs reduce contractility

Question 28

what changes in the frank starling relationship when contractility changes ( and what stays the same)

Answer 28

• changes in contractility lead to alterations in SV and CO when EDV/ atrail pressure are unchanged

Question 29

what happens to CO when HR increases with a given SV and what is this similar to

Answer 29

CO is also increased similar to the effect of increased contractility

Question 30

memorize this table

Answer 30

Question 31

is hypertention symptomatic

Answer 31

no usually asymptomatic until is damaging effects such as stroke, myocardial infarction, renal dysfunction, visual problems

Question 32

when is hypertension diagnosed

Answer 32

when the BP readings are taken at least two to three times at two or more separate appointments
before diagnosing a patient
- bc BP varies throughout the day

Question 33

what percentage of people have essential hypertension and what is the cause

Answer 33

90-95% and the cause is unknown

Question 34

what percetnage of patients does secondary hypertension and what is the cause

Answer 34

5-10%, it is secondary to renal disease, endocrine disorders etc

Question 35

what is the cause of the increase in arterial blood pressure in hyper tensive pts:

Answer 35

• caused by an increase in systemis vascular resistance or total peripheral resistance due to changes in vascular tone of the systemis resistance levels
• caused by an increase in CO due to changes in HR and SV

Question 36

what are the normal, elevated, High BP stage 1,stage2 and hypertensice crisis values?

Answer 36

Question 37