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DPT 728 Clinical Exercise Physiology > Anatomy and Physiology of Cardiovascular System > Flashcards

Anatomy and Physiology of Cardiovascular System Flashcards

1
Q

Function of Cardiovascular System

A
  • transports blood oxygen to tissues and blood oxygen to lungs
  • distributes nutrients to cells
  • removes metabolic wastes for reuse or elimination
  • transports hormones and enzymes
  • regulates pH to control acidosis and alkalosis
  • maintains fluid volumes
  • maintains body temperature
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2
Q

Cardiovascular Macroanatomy: The Heart

A
  • aka coronary or myocardium
  • positioned obliquely in mediastinum
  • roughly fist size
  • weighs between 250-350 g
  • 4 chambers, 4 valves, 4 layer wall
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3
Q

Coronary Microanatomy: Nervous Tissue

A
  • non-contractile
  • important in initiating contraction
  • contributes to syncytium necessary for coordinated contraction of heart
  • represents 1% of total cardiac tissue
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4
Q

Coronary Microanatomy: Contractile Tissue

A
  • 3 types of muscle within body differ in structure, location, function, and means of activation
  • cardiac muscle serves to generate pressure within CV system
  • similarities to skeletal muscle: striated, sarcomeres, Z lines, sliding filament action
  • differences from skeletal muscle: fibers-short, thick, few nuclei, t-tubules-wider and fewer, SR-less well developed, mitochondria-many more (25% cell volume), fuel sources-even better suited to use pyruvate and lactate (byproducts of intense exercise)
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5
Q

Anatomy: Atria

A
  • superior chambers

- L and R separated from ventricles by coronary sulcus

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6
Q

Anatomy: Ventricles

A
  • inferior chambers
  • thicker walls than atria
  • RV pumps thru pulmonary circuit
  • LV 2-3x thicker than RV, pumps thru systemic circuit
  • LV separated from RV by interventricular sulcus
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7
Q

Anatomy: Valves

A
  • maintain unidirectional blood flow
  • AV valves separate atria from ventricles
  • R AV is tricuspid
  • L AV is mitral or bicuspid
  • AV valves attach to chordae tendinae and papillary muscles
  • semilunar valves separate the ventricles from aorta and pulmonary trunk
  • each has 3 cusps
  • cusps prevent backflow from arteries to ventricles
  • pulmonic valve lies between RV and pulmonary artery
  • aortic valve lies between LV and aorta
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8
Q

Anatomy: Cardiac Wall

A
  • parietal pericardium: outer wall, has both fibrous (tough) and serous (smooth) sections
  • epicardium: aka visceral pericardium; pericardial cavity lies between visceral and parietal pericardium, pericardial fluid lies in this space
  • myocardium: cardiac muscle, thickest layer, contains fibrous skeleton
  • endocardium: lines myocardium, thin layer of epithelial tissue, joins with blood vessels in/out of heart
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9
Q

Myocardial Blood Supply

A
  • only endocardium nourished directly
  • myocardium is too thick for diffusion
  • L and R coronary arteries are primary supply
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10
Q

Main Coronary Arteries

A
  • branch from aorta
  • LCA aka left main or widows maker
  • circumflex (CxA): supplies laterodorsal walls of LA and LV
  • left anterior descending (LAD): supplies anterior walls of both ventricles
  • RCA supplies right side of heart, numerous branches that supply anterior, posterior, and lateral RV, and RA
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11
Q

Cardiac Conductive Tissue

A
  • muscle can depolarize and contract without neural stimulation: known as automaticity
  • has rhythmicity
  • cardiac cells interconnect end to end
  • intercalated discs allow impulse to travel cell to cell: this also contributes to the functional syncytium of the heart
  • myocardium acts functionally as one unit: depolarization of one cell spreads over entire myocardium
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12
Q

SA Node

A
  • posterior RA
  • source of electrical impulse
  • intrinsic pacemaker in healthy heart
  • depolarizes spontaneously
  • 60-80 times/minute
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13
Q

AV Node

A
  • lies in inferior part of interatrial septum
  • receives impulse from SA node via internodal gaps
  • impulse delayed .13 seconds
  • this delay helps atria to contract in coordinated manner
  • intrinsic pacemaker fires 40-60 bpm
  • acts as a backup for SA node in case it stops working
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14
Q

AV Bundle (Bundle of His)

A
  • lie in walls of ventricles
  • includes right and left bundle branches
  • transports electrical impulse to the ventricles
  • its intrinsic pacemaker fires 20-40 bpm
  • 3rd line to keep heart beating, backup to the back up
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15
Q

Purkinje Fibers

A
  • lie in walls of ventricles
  • further transports electrical impulse into the ventricles
  • its intrinsic pacemaker fires 20-40 bpm
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16
Q

Regulating Cardiac Electrophysiology

A
  • sympathetic neural input: stimulatory, originates in cardioacceleratory region of medulla oblongata; via efferent neurons of T1-T5
  • parasympathetic neural input: inhibitory, cardioinhibitory region of medulla, via vagus nerve, rest and digest
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17
Q

AP in Autorhythmic Cardiac Cells

A
  • autorhythmic cells of SA node cannot maintain resting membrane potential (-60 mV)
  • cells gradually become less polar secondary to decreased permeability to potassium efflux, increased permeability to calcium influx, and no change in permeability to sodium influx
  • this drift of RMP known as pacemaker potential
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18
Q

AP in Contractile Cardiac Cells

A
  • RMP is -80 to -90 mV
  • stimulus to membrane –> AP
  • sodium channels open: alls rapid depolarization
  • sodium channels close secondary to concentration equilibrium
  • slow calcium and sodium channels open: allow slow influx, AP extended and repolarization delayed
  • decreased permeability to potassium delayed: extends plateau
  • slow calcium and sodium channels close
  • potassium channels open: potassium effluxes out of cell, electrical charge becomes more negative, repolarization occurs
  • must repolarize before 2nd depolarization
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19
Q

ECG

A
  • measures summation of AP
  • P wave=sum of atrial AP
  • QRS is aggregation of ventricular AP
  • T wave is ventricular repolarization
  • atrial repolarization obscured by QRS complex
  • careful assessment can tell us about: heart rate and rhythm, chamber enlargement, conduction derangements, evidence of acute or previous MI, myocardial ischemia, drug and metabolic effects
20
Q

Cardiac Mechanical Function

A
  • cardiac cycle refers to alternating periods of relaxation and contraction of heart
  • contraction = systole
  • relaxation = diastole
  • there are known relationships among events of cardiac cycle: electrical, pressure, volume, contractile
  • systole, diastole, blood pressure, preload, afterload, CO, SV, ejection fraction
21
Q

Cardiac Mechanical Function

A
  • blood pressure: force exerted on wall of blood vessel
  • blood flow: actual volume of blood flow thru vessel, organ, or entire system per unit of time
  • resistance: opposition to blood flow that the blood encounters
  • review BP values
22
Q

Preload

A
  • amount of tension on myocardium before contraction
  • determined by: extensibility of cardiac muscle, venous return
  • up to a point, a larger end-diastolic tension tends to produce a larger stroke volume
23
Q

Afterload

A
  • amount of tension after contraction
  • resistance the ventricles must work again
  • determined by: aortic valve compliance, systemic arterial pressure
  • ex: increased by increased systemic arterial pressure, aortic valve stenosis
24
Q

Stroke Volume

A
  • volume of blood pumped by ventricles each contraction
  • differences between EDV and ESV
  • greater diastolic filling –> increased V
25
Q

Cardiac Output

A
  • volume of blood pumped by ventricles each minute
  • CO = HR x SV
  • typically resting CO is 5 to 5.5 L/min
  • 4-8 fold increase during exercise
26
Q

Control of Cardiac Output

A
  • controlled by venous return which is in turn controlled by total peripheral flow
  • within physiological limits, heart pumps all blood that comes into it: thus SV tends to increase as volume of blood returned to heart increases (Frank-Starling law)
  • increased flow stimulates increase in HR
  • decreased CO caused by: sedentary lifestyle, myocardial infarction, heart valve disease, cardiac tamponade, metabolic derangements
27
Q

Ejection Fraction

A
  • percentage of blood filling the ventricle ejected with each beat
  • EF = [SV/EDV] x 100
  • normally runs 65% +/-8%
  • can be calculated at rest and at work
28
Q

Cardiac Metabolism

A

-myocardial oxygen utilization and aerobic metabolism

29
Q

Myocardial Oxygen Utilization

A
  • determined by combination of oxygen (a-vO2 diff-difference in oxygen in arterial vs. venous blood)
  • oxygen extraction of coronary circulation is nearly optimal at rest: 60-70%, thus during exercise, increased oxygen demands met entirely by increased blood flow
  • angina develops when oxygen demand out paces oxygen delivery
  • estimated as rate-pressure product (RPP) or double product
  • may be approximated clinically by the following equation
  • RPP is an accurate reflection of: myocardial oxygen consumption under a wide range of conditions, including dynamic and static exercise; not meant to compare differences in SV between individuals
30
Q

Aerobic Metabolism

A
  • cardiac function relies on aerobic energy
  • myocardium has 3x oxidative capacity of skeletal muscle
  • glucose, FFA, lactate are the preferred energy sources
  • increased glycogen-sparing with training
31
Q

The Arteries

A
  • exhibit high elasticity
  • important in maintaining BP
  • atherosclerosis: decreased elasticity, decreased peripheral responsiveness to changes in BP
  • arteries with smooth muscle around vessel: located more distally, greater role in vasoconstriction
32
Q

The Capillaries

A
  • 10-100 capillaries per bed
  • all types ~7-10 micrometers in diameter
  • continuous: walls typically of single layer endothelial cells and narrow lumen which allows RBC through single file
  • allow for exchange
33
Q

The Veins

A
  • capacitance vessels because of their distensibility which enables them to pool large volumes of blood and become reservoirs of blood
  • low pressure component
  • little s. muscles around vessels
  • have one way valves: venous blockage weakens valves, varicose veins and hemorrhoids
34
Q

Blood Movement in Veins

A

-venous return greatly influenced by activity of skeletal muscle: skeletal muscle pump, diaphragm pump

35
Q

The Lymphmatics

A
  • system arranged in numerous nodes
  • drain ECF from: lungs, GI tracts, other body parts
  • most lymph returned to circulation via subclavian veins
36
Q

Blood Flow Through Specialized Areas: Lymphatic Circulation

A
  • functions primarily to remove fluid from ECF: 2-4 L/d enters lymphatic system
  • also serves to: carry proteins into circulation, transfer large enzymes into circulation, transport antibodies
  • movement occurs secondary to compression of skeletal muscle, one-way valves, contraction of lymph vessles
37
Q

Blood Flow Through BBB

A
  • limits/slows entrance of compounds to brain
  • capillary beds decrease permeability following birth
  • only water, oxygen, and carbon dioxide pass unimpeded
  • speed of entry inversely related to lipid solubility and molecule size
  • areas of brain outside BBB aka circumventricular organs; mostly hormone secreting organs such as pineal gland or posterior pitutiary
38
Q

Blood Flow: Distribution in Vessels at Rest

A
  • splanchnic 24% supplies digestive system
  • renal 19%
  • cerebral 13%
  • coronary muscle 4%
  • skeletal muscle 21%
  • skin 9%
  • other 10%
39
Q

Blood Flow: Distribution in Organs at Rest vs. Exercise

A
  • distribution of CO may change to meet physiologic demand
  • shifts from non-working to vascular beds
  • decrease blood to splanchnic and increase blood to skeletal muscle when exercising
40
Q

Blood Flow

A
  • inextricably linked with pressure and resistance
  • any blood vessel has the following characteristics:
  • pressure
  • flow
  • velocity of blood
  • cross sectional area
41
Q

Blood Pressure

A
  • BP = CO x peripheral resistance
  • CO = HR x SV
  • peripheral resistance: length of vessel, viscosity of blood, radius of vessel (greatest variability-arteriole vasoconstriction/vasodilation)
  • gravity and BP: +/-.77 mmHg with each cm increase or decrease in heart
42
Q

Ohm’s Law and Circulation

A
  • R = V/I
  • R=resistance, V=potential difference in volts, I=current in amperes
  • can restate for circulatory system R = P/F
  • P=potential difference or pressure and F=flow
  • resistance is partitioned between working and non-working vascular beds
  • we can rearrange algebraically P = F x R where P=pressure, F=flow and R=resistance
  • we see that the greater the resistance, the lesser the flow
  • endurance exercise: increase volume stress in cardiovascular system in periphery when regularly exercise aerobically
  • resistance training results in pressor resistance response
43
Q

Regulating Blood Flow

A
  • local chemical mediators causing vasodilation: decrease [oxygen] increase [carbon dioxide] especially important in brain, decrease pH, increase temperature
  • systemic chemical mediators: catecholamines (N, NE)
  • has both humoral and neural control
44
Q

Humoral Control of Blood Flow

A
  • regulation by substances secreted or absorbed in body fluids
  • hormones, ions, etc
  • may exert local or systemic effects
  • local chemical mediators causing vasodilation: decrease [oxygen] increase [carbon dioxide] especially important in brain, decrease pH, increase temperature
  • systemic chemical mediators: catecholamines…
  • activation of a1 adrenergic receptors: vasoconstriction of most blood vessels
  • activation of beta1 adrenergic receptors: increase HR and strength of contraction; beta blockers limit this action (blunted response to exercise leading to HR not rising as normally would)
  • activation of beta2 adrenergic receptors: vasodilation of skeletal muscle (high in beta2 receptors
  • angiotensin: powerful vasoconstrictor; regulates mineral corticoids (sodium and potassium balance), altered with CHF
45
Q

Neural Control of Blood Flow

A
  • nerve mechanisms do not actively dilate instead reduce constriction
  • aka passive dilation
  • exception is skeletal muscle which is active dilation

DPT 728 Clinical Exercise Physiology (13 decks)

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