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
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
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
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)
5
Q
Anatomy: Atria
A
- superior chambers
- L and R separated from ventricles by coronary sulcus
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
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
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
9
Q
Myocardial Blood Supply
A
- only endocardium nourished directly
- myocardium is too thick for diffusion
- L and R coronary arteries are primary supply
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
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
12
Q
SA Node
A
- posterior RA
- source of electrical impulse
- intrinsic pacemaker in healthy heart
- depolarizes spontaneously
- 60-80 times/minute
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
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
15
Q
Purkinje Fibers
A
- lie in walls of ventricles
- further transports electrical impulse into the ventricles
- its intrinsic pacemaker fires 20-40 bpm
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
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
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
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
