Cardiovascular Flashcards
Purpose of the Heart
Provides the drive for blood flow
Physical Characteristics of the Heart
- 4 chambers
- 11 oz for average male, 9 oz for female
- 2 sides separated by interventricular septum
Volume of Blood Circulation
- ~70 mL/beat at rest
- ~1900 gallons/day at rest
- 52 million gallons over a 75-y life span
Myocardium
- Heart muscle
- Myocardial fibers interconnect in latticework fashion to allow the heart to function as a unit
Right Side of the Heart
- Receives blood returning from body
- Pumps blood to lungs for aeration through pulmonary circulation
Left Side of the Heart
- Receives oxygenated blood from lungs
- Pumps blood into thick-walled muscular aorta for distribution via systemic circulation
The Heart’s Valves
- Atrioventricular Valves (Tricuspid & Bicuspid/Mitral)
- Semilunar Valves
Tricuspid Valve
Provides one-way blood flow from the right atrium to the right ventricle
Bicuspid/Mitral Valve
Provides one-way blood flow from left atrium to left ventricle
Semilunar Valves
- Located in arterial wall just outside heart
- Prevents blood from flowing back into the heart between contractions
Myocardium & the Left Ventricle
- Wall thickness varies directly with stress placed on the chamber walls
- Left ventricle is the largest and most powerful of chambers
- With vigorous exercise, the left ventricle increases in size
Intercalated Disks and Impulse Travel
- Impulses travel quickly in cardiac muscle and allows it to act as one large muscle fiber
- All fibers contract together
Effect of the Parasympathetic NS
Acts through the vagus nerve to decrease heart rate and force of contraction
Effect of the Sympathetic NS
Stimulated by stress to increase heart rate and force of contraction
Effect of Epinephrine and Norepinephrine
- Released due to sympathetic stimulation
- Increases heart rate
Bradycardia
Resting heart rate <60 bpm
Tachycardia
Resting heart rate >100 bpm
P Wave
Atrial depolarization
QRS Complex
- Ventricular depolarization
- Atrial repolarization also occurs here, but is obscured by QRS waves
T Wave
Ventricular repolarization
Diastole
- Relaxation phase when blood fills the heart chambers
- T wave to QRS complex
Systole
- Contraction phase when the heart pumps blood out of the chambers
- QRS complex to T wave
Stroke Volume
- Volume of blood pumped per contraction
- SV = EDV - ESV
End-Diastolic Volume (EDV)
Volume of blood in ventricle before contraction
End-Systolic Volume (ESV)
Volume of blood in ventricle after contraction
Cardiac Output (Q)
- Total volume of blood pumped by the ventricle per minute
- Q = HR x SV
Ejection Fraction (EF)
- Proportion of blood pumped out of the left ventricle each beat
- EF = SV/EDV
- Averages 60% at rest
Blood Vessels
- Arteries
- Arterioles
- Capillaries
- Venules
- Veins
Arteries
Largest, most muscular vessels, carries blood away from heart
Arterioles
Smaller than arteries
Capillaries
Where exchange between blood and tissues occurs, very small
Venules
Smaller than veins
Veins
Carries blood back to heart
Muscle Pump
Muscular contractions create the pressure gradient to return blood to the heart in the veins
Blood Distribution
- Matched to overall metabolic demands
- Determined by the balance between mean arterial pressure (MAP) and total peripheral resistance (TPR)
Autoregulation
Arterioles within organs or tissues dilate or constrict
Extrinsic Neural Control
Sympathetic nerves within walls of vessels are stimulated
Blood Pressure
- BP = Q x TPR
- Blood vessel constriction increases blood pressure
- Blood vessel dilation reduces blood pressure
Mean Arterial Pressure
- Average pressure exerted by the blood as it travels through arteries
- MAP = DBP + [0.333(SBP-DBP)]
Blood Composition
- 55% plasma
- 45% formed elements
Plasma
- 90% water
- 7% plasma proteins
- 3% other materials
Formed Elements
- 99% red blood cells
- 1% white blood cells and platelets
Hematocrit
Ratio of formed elements to the total blood volume
White Blood Cells
Protect body from disease organisms
Blood Platelets
Cell fragments that help blood coagulation
Red Blood Cells
Carry oxygen to tissue with the help of hemoglobin
Blood Viscosity
- Thickness of the blood
- The more viscous, the more resistant to flow
- Higher hematocrits result in higher blood viscosity
Cardiovascular Response to Acute Exercise
- HR, SV, and Q increase
- Blood flow and BP change
- All result in allowing the body to meet the increased demands placed on it efficiently
Resting HR
- Averages 60-80 bpm
- Can range from 28-100 bpm
- Tends to decrease with age and with increased cardiovascular fitness
- Is affected by environmental conditions such as altitude and temperature
Maximum HR
- The highest HR value one can achieve in an all-out effort to the point of exhaustion
- Remains constant day to day and changes slightly from year to year
Max HR Estimation
HRmax = 220 - age in years
Steady State HR
- HR plateau reached during constant rate of submaximal work
- Optimal HR for meeting circulatory demands at that rate of work
- As steady-state HR decreases, efficiency improves
Stroke Volume and Exercise
- Determines cardiorespiratory endurance capacity at max rates of work
- May increase with increasing rates of work up to intensities of 40-60% of max
- May continue to increase up through maximal exercise intensity
- Depends on position of body during exercise
Frank Starling Mechanism
More blood in the ventricle causes it to stretch more and contract with more force
Stroke Volume Increases During Exercise
- Increased ventricular contractility without end-diastolic volume increases
- Decreased TPR due to increased vasodilation of blood vessels to active muscles
Cardiovascular Drift
- Gradual decrease in stroke volume and systemic and pulmonary arterial pressures and an increase in HR
- Occurs with steady-state prolonged exercise or exercise in a hot environment
Blood Pressure and Endurance Exercise
- Systolic BP increases in direct proportion to increased exercise intensity
- Diastolic BP change little if any during endurance exercise, regardless of intensity
Blood Pressure and Resistance Exercise
Exaggerates BP responses to as high as 480/350 mmHg
Arm and Leg Difference in BP
-
Arterial-Venous Oxygen Difference
- Amount of oxygen extracted from the blood as it travels through the body
- Calculated as the difference b/t the oxygen content of arterial blood and venous blood
- Increases with increasing rates of exercise as more oxygen is taken from blood
Fick Equation
- Represents the relationship of VO2 to the arterial-venous oxygen difference (a-vO2 diff) and cardiac output (Q)
- VO2 = Q x a-vO2 diff
