Cardiovascular Physiology

Question 1

CO

Answer 1

(Cardiac Output), L/min [CO = HR x SV]
Volume of blood pumped from each ventricle per minute

Avg at rest: 5L/min

Question 2

SA Node

Answer 2

(Sinoatrial), 1st step in Impulse Conduction System

• Primary Pacemaker
• Intrinsic Rate: 60-100bpm
• Sends AP to AV Node via Bachman’s and Internodal Bundles
  (0. 4sec)
• P wave on EKG

*Cardiac Cycle electrical event: slow channel with AV Node

Question 3

Impulse Conduction System

Answer 3

SA Node*
AV Node*
Bundle of His
Bundle Branches
Purkinje Fibers*

*All muscle cells have potential to conduct an impulse

Question 4

AV Node

Answer 4

(Atrioventricular), 2nd step in Impulse Conduction System
-Secondary Pacemaker
-Intrinsic Rate: 40-60bpm
-Sends AP to Bundle of His (0.11sec - slower for
ventricular filling)
-Delay following P wave on EKG

*Cardiac Cycle electrical event: Slow channel with SA Node

Question 5

Bundle of His

Answer 5

3rd step in Impulse Conduction System

-Sends AP to Bundle Branches via interventricular septum

Question 6

HR

Answer 6

(Heart Rate), bpm
Number of cardiac cycles/beats per minute

Avg at rest: 72bpm

• Stronger myocardium & sympathetic drive
  
  • -> lower resting HR

Question 7

SV

Answer 7

(Stroke Volume), mL/beat [EDV - ESV = SV]
Volume of blood ejected by each ventricle per cycle/beat

Avg at rest: 70mL/beat

3 Physiologic Controls:
Preload
Contractility
Afterload

Question 8

EF

Answer 8

(Ejection Fraction), % [EF = (SV / EDV) x 100]
Percentage of blood ejected by each ventricle per cycle/beat
-indicator of pump efficiency
-% decline: ^HR and VO2 = heart works harder to deliver same amt of O2

Avg at rest: 55-65%
Critical point: <20%

Question 9

CI

Answer 9

(Cardiac Index) [CO / Body SA]
Indicator of pump function in clinical units

Avg at rest: 2.8 - 4.2

Question 10

Cardiac Innervation

Answer 10

Modulation of HR and contractility

1. Sensors
2. Afferent pathways (Vagus & Glossopharyngeal N)
3. Integration center (Medulla/pons)
4. Efferent pathways (Symp vs Parasymp)
5. Receptors (Myocardium)

Question 11

Cardiac Innervation:

Efferent Pathways

Answer 11

Sympathetic Parasympathetic
-Cardiac N -Vagus N
-Ventricular myocardium -Atrial myocardium
-Adrenergic (Epi/Norepi) -Cholin / Musc (AcH)
-AMPING: -DAMPENING
Inc HR / AV conduxn / Dec HR / AV conduxn /
Force contraxn Force contraxn

Question 12

Sensors of Cardiac Innervation

Answer 12

1. Baroreceptors - pressure
2. Chemoreceptors - Dec O2 / Inc CO2 or H+
3. Stretch receptors - venous return

Question 13

Baroreceptors

Answer 13

Pressure sensors in aortic arch + carotid sinus

Question 14

Chemoreceptors

Answer 14

Sensors in aortic arch and carotid body that detect decrease in [O2] and increase in [CO2 and H+]

Question 15

Stretch Receptors

Answer 15

Sensors that detect venous return in junction of great veins and atria

Question 16

Bundle Branches

Answer 16

4th step of Impulse Conduction System
=Send AP down interventricular septum to Purkinje Fibers in
subendocardium

Question 17

Purkinje Fibers

Answer 17

5th step of Impulse Conduction System

• Tertiary Pacemaker
• FAST cell to cell AP transmission
• Intrinsic Rate: 20-40bmp
• Synchronous contraction + wringing action

*Cardiac Cycle electrical event: Fast channel

Question 18

Adrenergic Receptors

Answer 18

Cardiac N
Myocardial receptors of the Sympathetic Pathway
-mediated by epi/norepinephrine

Examples: Beta-1 & 2, Alpha-1

Question 19

Cholinergic Receptors

Answer 19

(Muscarinic) - Vagal N
Myocardial receptors of the Parasympathetic Pathway
-mediated by ACH

Question 20

Chronotropic

Answer 20

HR

Question 21

Dromotropic

Answer 21

AV Conduction Speed

Question 22

Inotropic

Answer 22

Atrial Contraction

Question 23

Cardiac Cycle

Answer 23

(Heart Beat)

sequence of simultaneous electrical (depol / repol) and mechanical (systole / diastole) events

Question 24

Electrical Events of Cardiac Cycle

Answer 24

Depolarization = Inc permeability of pacing cells –> AP
Excitation

Repolarization = Restoration / Recovery / Refractory
periods of cell

Question 25

Mechanical Events of Cardiac Cycle

Answer 25

Systole Diastole

Question 26

Characteristics Common to All Muscle Cells

Answer 26

``` (CRAE) Conductivity Rhythmicity Automaticity Excitability ```

Question 27

Depolarization

Answer 27

Electrical event of Cardiac Cycle: -Increased membrane permeability of pacing cells (Na, K, Ca) -->AP Excitation Slow Channels: SA/AV Nodes Fast Channels: Purkinje Fibers + myocytes

Question 28

Repolarization

Answer 28

Electrical event of Cardiac Cycle: - Cell restored to negative via Na/K Pump - -> Recovery *Refractory periods (ERP / RRP)

Question 29

Cardiac Electrical Cycle Fast Response

Answer 29

Fast channels: Purkinje + myocytes Phase 0: Rapid Depol (Na+ IN) Phase 1: Partial Repol (Cl- IN) Phase 2: Plateau (No net change) *Not in SA/AV Nodes Phase 3: Rapid Repol (Na/K Pump restores) Phase 4: Rest (K+ OUT)

Question 30

Cardiac Mechanical Cycle

Answer 30

Vent Late Diastole (+ Atrial Sys) = Fast vent filling Vent Early Diastole (+ Atrial Dia) = Isovolumetric Contraxn Vent Late Diastole = Vent Ejection Vent Early Diastole = Isovolumetric Relaxation Vent Mid Diastole = Slow vent filling

Question 31

EDV

Answer 31

(End Diastolic Volume) Volume of blood when ventricles completely filled Norm: 120-130mL [EDV - ESV = SV]

Question 32

Isovolumetric Contraction

Answer 32

Contraction with no blood movement bc Vent Pressure > Atrial Pressure and AV valves close while SL valves do not open immediately *Ventricular Early Systole

Question 33

ESV

Answer 33

(End Systolic Volume) Volume of blood left in ventricles post ejection Normal: 50-60mL [EDV - ESV = SV]

Question 34

Isovolumetric Relaxation

Answer 34

Relaxation with no blood movement bc vent pressures < atrial pressures so SL valves close, and AV valves remain closed until vent pressure < atrial pressure *Ventricular Early Diastole

Question 35

Preload

Answer 35

Physiological control of SV =Degree of stretch prior to contraxn -dependent on venous return (increase = INC SV) Drugs that decrease preload: - Diuretics - Venous dilators - Sympathomimetics

Question 36

Contractility

Answer 36

Phys control of SV =Force of contraction based on interactions at crossbridges of myofilaments (Inc = INC SV) -dependent on Ca avail & increased SNS input Drugs that affect contractility: - Adrenergics (INC) - Beta blockers and Ca Blockers (DEC)

Question 37

Afterload

Answer 37

Phys control of SV =amt of aortic/pulmonary pressure the ventricles must overcome to open SL valves and eject blood (Inc Arterial Pressure = Inc afterload = DEC SV) -dependent on pressure, radius and wall thickness Drugs that increase afterload: - Vasodilators - ACE Inhibitors - ACE Receptor blockers - Sympatholytics

Question 38

Hemodynamics

Answer 38

Relationship b/w blood flow and pump (pressure source) [R SV = L SV] and [CO = VR] 3 Variables: 1. CO 2. Perfusion Pressure 3. Peripheral Vascular Resistance

Question 39

Hemodynamic Disorders

Answer 39

1. Thrombosis 2. Embolism 3. MI 4. Edema 5. Shock

Question 40

Shock

Answer 40

microcirculation failure and inadequate perfusion of blood to vital organs --> Peripheral vasodilation: Hypotension = bad O2 delivery, cap beds close and shunt blood to major organs, others shut down Types: 1. Cardiogenic 2. Hypovolemic 3. Neurogenic 4. Septic

Question 41

Albumin

Answer 41

Plasma protein that acts as oncotic pressure that pulls fluid into cells