Reflex control of total cardiac output and total peripheral resistance is controlled by?
(1) sympathetic stimulation of the heart, arterioles, and veins; and
(2) parasympathetic stimulation of the heart only.
Arterial stiffening
Occurs with aging, even in the absence of HTN.
Where is the major cardiovascular center in the CNS?
is in the brainstem in the medulla.
secondary areas: hypothalamus, the cerebral cortex, the thalamus, and complex networks of exciting or inhibiting interneurons (connecting neurons) throughout the brain.
sequence of events that occur after the baroreceptor reflex is stimulated
Neural impulses travel from the carotid artery over to the glossopharyngeal nerve (ninth cranial nerve) and through the vagus nerve from the aorta to the cardiovascular control centers in the medulla.
> ? para activity and ? sympathetic = bv's dilate and
pulmonary edema
increased left ventricular filling pressures can "back up" into the pulmonary circulation, where they force plasma out through vessel walls, causing fluid to accumulate in lung tissues.
- reason why pressure changes important
Where are the receptors for neurotransmitters located in the heart?
The b1-receptors - heart > the conduction system (AV and SA nodes, Purkinje fibers) and the atrial and ventricular myocardium
b2-receptors; on coronary arterioles and cause coronary vasodilation when stimulated by epinephrine
What, if any, is the effect of epinephrine on b2-receptors of the heart?
Dilate coronary arterioles thereby increasing coronary blood flow.
Occlusion of the circumflex artery during a myocardial infarction would interrupt blood supply to the:
The circumflex artery supplies blood to the left atrium and the lateral wall of the left ventricle.
The circumflex artery often branches to the posterior surfaces of the left atrium and left ventricle.
left anterior descending artery
(LAD), also called the anterior interventricular artery, delivers blood to portions of the left and right ventricles and much of the interventricular septum.
During the cardiac cycle, the aortic and pulmonic valves close after the ventricles contract because the:
blood fills the cusps and causes their free edges to meet in the middle of the vessel, closing the valve and preventing any backflow.
The mitral and tricuspid valves close after the ventricles are filled with blood because the:
increased pressure in the ventricles pushes the valves to close.
During ventricular relaxation the two atrioventricular valves open and blood flows from the higher-pressure atria to the relaxed ventricles. With increasing ventricular pressure these valves
Which cardiac chamber has the thinnest wall and why?
The two atria have the thinnest walls because they are low-pressure chambers that serve as storage units and conduits for blood that is emptied into the ventricles.
semilunar valves
1. Pulmonary
2. Aortic
- When ventricles relax, blood fills the cusps and causes their free edges to meet in the middle of the vessel, closing the valve and preventing any backflow.
atrioventricular valves
1. Tricuspid valve: right atrium/ventricle
2. Bicuspid valve/mitral: left
During ventricular relaxation the two atrioventricular valves open and blood flows from the higher-pressure atria to the relaxed ventricles. With increasing ventricular pressure the
Pulmonary Veins
4 pulmonary veins: 2 from the right lung and 2 from the left lung, carry oxygenated blood from the lungs to the left side of the heart.
The great vessels
1. Superior and inferior venae cavae
>superior vena cava drains the head and arms, and the inferior vena cava drains the lower body.
2. Pulmonary artery (trunk)
>Right and left pulmonary arteries
3. Pulmonary veins (4)
Phases of cardiac cycle
1. Atrial systole: Left atrial contraction, "atrial kick," provides a significant increase of blood to the left ventricle.
2. Ventricular systole
3. Ventricular ejection (semilunar valves open)
4. Ventricular relaxation (closure of aortic valve)
5. Ventri
A wave
Atrial pressure curves are composed of the a wave, which is generated by atrial contraction.
V wave
The v wave is an early diastolic peak caused by filling of the atrium from the peripheral veins.
C wave
The c wave occurs after the a wave in early systole and may represent bulging of the mitral valve into the left atrium during early systole.
systole/diastole
Systole: depolarization, contraction
Diastole: relaxation (the time bw action potentials)
Left Circumflex artery
supplies blood to the left atrium and the lateral wall of the left ventricle. The circumflex artery often branches to the posterior surfaces of the left atrium and left ventricle.
left anterior descending artery (LAD)
also called the anterior interventricular artery, delivers blood to portions of the left and right ventricles and much of the interventricular septum.
Right coronary artery branches
1. Conus
2. Right marginal branch
3. Posterior descending branch
Hearts conduction system
Sinoatrial node
Intranodal pathways
Atrioventricular node
Bundle of His (AV bundle)
Right and left bundle branches
Purkinje fibers
- the ANS influences the rate of impulse generation (firing), depolarization, and repolarization of the myocardium and the s
Atrioventricular node
(AV): If the SA node is damaged, the AV node will become the heart's pacemaker at a rate of about 40 to 60 spontaneous depolarizations per minute
Sinoatrial node
(SA): The electrical impulse normally begins in the SA node because its cells depolarize more rapidly than other automatic cells.
Catecholamines
(Epinephrine and Norepinephrine)
1- speed heart rate,
2 - shorten the conduction time through the AV node
3 - increase the rhythmicity of the AV pacemaker fibers.
Propagation of cardiac action potentials
> Phase 0 - depolarization of a cardiac muscle cell. This phase lasts 1 to 2 milliseconds (ms) and represents rapid sodium entry into the cell.
> Phase 1 is early repolarization, in which calcium slowly enters the cell.
> Phase 2: Repolarization cont. "pl
P wave
atrial depolarization
PR interval
Time from the onset of atrial activation to the onset of ventricular activation.
Impulse: Time to travel from the sinus node through the atrium, AV node, and His-Purkinje system to activate ventricular myocardial cells
- normally ranges from 0.12 to 0.20
QRS complex
Sum of all ventricular depolarizations
ST interval
ventricular myocardium depolarized
QT interval
electrical systole" of the ventricles
Varies inversely with the heart rate
innervation: Sympathetic Nerves
When the sympathetic nervous system is activated, epinephrine-mediated b2-receptor stimulation combines with the production of vasodilatory metabolites from actively metabolizing myocytes to override the effect of norepinephrine (on ?-2).
** Thus sympathe
efferent sympathetic fibers
originate in the thoracic spinal cord and branch into the superior middle and inferior cardiac nerves - join at the cardiac plexus (root of aorta in front of trachea).
- overall effect of catecholamines stim is influx of Ca++ during the ap plateau.
Efferent parasympathetic fibers
originate in medulla oblongata and travel via the vagus nerves to join the sympathetic nerves in the cardiac plexus.
- acetylcholine ? HR, slows conduction thru AV, and can block cardiac ap's coming from atria.
innervation: Parasympathetic nerves
The resting heart rate in healthy individuals is primarily under the control of parasympathetic stimulation.
> While the individual is at rest, parasympathetic effects from the vagus nerves override sympathetic effects in the sinoatrial (SA) node.
?1 + epinephrine
#NAME?
?1 adrenergic receptor
- found mostly in the heart, specifically the conduction system (AV and SA nodes, Purkinje fibers) and the atrial and ventricular myocardium
?2 + epinephrine
#NAME?
?2 receptor
are found mostly on coronary arterioles and cause coronary vasodilation when stimulated by epinephrine.
?1 + norepinephrine
#NAME?
?2 + norepinephrine
inhibits release of more norepinephrine, promoting vasodilation.
- alpha2 receptors are located mostly on sympathetic ganglia and nerve terminals.
-another safety mech to prevent overactivity of the sympathetic
myocardial cells
- Nearly identical to skeletal muscle cells
- Intercalated disks
- Actin, myosin, and the troponin-tropomyosin complex (Troponin T, I, and C)
- Myocardial metabolism (constant ATP prod)
- Myocardial oxygen consumption (cardiac work)
End-Diastolic Volume EDV
volume of blood in the right and/or left ventricle at end load or filling in (diastole).
- An increase in EDV (preload) on the heart and increases the amount of blood ejected from the ventricle during systole (SV).
- more stretching
- monitor by measuring
Diastole
is the period of time when the heart refills with blood after systole (contraction).
- ventricular or atrial
End-systolic Volume
is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling
- depends on strength of contraction and the resistance to ventricular emptying.
- will be seen at the end of the T wave.
Afterload
the resistance to ejection of blood from the left ventricle.
- Low aortic pressures is a decreased afterload = increases rate of contraction.
- high pressures increases after load = slows contraction
Frank-Starling Law of the Heart
Myocardial stretch determines force of myocardial contraction.
- More stretch = increased force of contraction
- reason right and left ventricles maintain equal outputs despite stroke (beat) output variation
- the volume of blood in the heart at the end o
SA node
controls the heart beat. natural pacemaker
- located in the upper wall of the right atrium, and is composed of muscle tissue that sends electrical impulses to the rest
Blood Flow
De-Oxygenated blood > R atrium > Tricuspid valve > right ventricle > semilunar valve > pulmonary artery > lungs (CO2/O2 exchange) > pulmonary veins > left atrium > bicuspid valve > left ventricle > aortic valve
What is atrial kick
Left atrial contraction, "atrial kick," provides a significant increase of blood to the left ventricle.
Occlusion of the left anterior descending artery during a myocardial infarction would interrupt blood supply to the?
the left and right ventricles and much of the interventricular septum.
The cardiac electrical impulse normally begins spontaneously in
the sinoatrial (SA) node because
its cells depolarize more rapidly than other automatic cells of heart.
What is responsible for shortening the conduction time of ap through AV node?
Catecholamines
Two factors of preload
1. amount of venous return to ventricle
2. the blood left in the ventricle after systole (end systolic volume)
cardiac output
the volume of blood pumped thru systemic or pulmonary circuit per minute. Liters per min.
- HR x SV
- increased preload will decrease CO
SV
- amount of blood pumped by the heart per cardiac cycle.
- measured in ml/beat.
A decreased SV may indicate impaired cardiac contractility or valve dysfunction and may result in heart failure.
An increased SV may be caused by an increase in circulating vo
4 factors that influence CO directly
preload
afterload
contractility
heart rate
baroreceptor reflex response to decreased bp
accelerates hr and causes vessels to constrict. this raises bp.
-critical to maintaining adequate tissue perfusion.
baroreceptor reflex response to high bp
- the pressureceptors increase their rate of discharge when stretched by bp elevations.
-Neural impulses are transmitted over the glossopharyngeal nerve from the carotid artery and through the vagus nerve from aorta to control centers in medulla.
- These
Bainbridge reflex
causes changes in the heart rate after intravenous infusions of blood or other fluid.
- if initial hr slow, infusion will accelerate it. vise versa
Laplace's Law
- wall tension is related directly to the product of intraventricular pressure and internal radius
- and inversely to the wall thickness.
cross bridge theory
- head of myosin has site for actin and a sep enzymatic site for ATP hydrolysis. Splitting of ATP occurs and is transferred to myosin.
- high energy myosin binds to actin via cross bridge and undergoes a position change, exerting traction on the rest of t
Poiseuille's formula
Vessel length, diameter, and blood viscosity.
- A vessel having twice the length of another (each having the same radius) will have twice the resistance to flow.
- if the viscosity of the blood increases 2-fold, the resistance to flow will increase 2-fold
What is the major determinant of the resistance blood encounters as it flows through the systemic circulation?
The thick smooth muscle layer of the arterioles
The muscular arteries
are the medium-size and small arteries farther from the heart and contain fewer elastic fibers and more muscle fibers than the elastic arteries because being farther from the heart, they have less need of the properties of stretch and recoil. The function
The elastic arteries
have a very thick tunica media that contains more elastic fibers than smooth muscle fibers. Elastic arteries include the aorta and its major branches and the pulmonary trunk.
chemoreceptors
- are receptor (proteins) which are specific to the particular chemical which involved in cell signaling.
- are found close to the carotid and aortic baroreceptors in small structures called carotid bodies and aortic bodies.
- are sensitive to any change
atrial natriuretic peptide ANP
a peptide secreted from cells (monocytes) in the right atrium when right atrial bp increases.
- under pathologic conditions, the left ventricle may secrete ANP.
- causes increased urine sodium excretion, leading to decreased blood volume and blood pressur
MAP
- changes in the relationship b/w CO and systemic vascular resistance (SVR)
- reflects the arterial pressure in the vessels perfusing the organs.
Low MAP
indicates decreased blood flow through the organs.
high MAP
indicates an increased cardiac workload.
Laminar blood flow
(streamline flow) occurs when a fluid flows in parallel layers, with no disruption between the layers.
- normal is laminar. under conditions of high flow, particularly in the ascending aorta, laminar flow can be disrupted and become turbulent.
Turbulent flow
- flow is obstructed and the vessel turns or blood flows over rough surfaces.
- whorls or eddy currents produce nose, ex. murmur heard on auscultation.
- increases resistance, and the energy required to drive blood flow because it increases the loss of en
maintenance of bp
- is dependent upon intrinsic, reflex, hormonal, renal, and microvascular control systems.
SVR
The measurement of resistance or impediment of the systemic vascular bed to blood flow.
- An increased SVR can be caused by vasoconstrictors, hypovolemia, or late septic shock.
- A decreased SVR can be caused by early septic shock, vasodilators, morphine,
SNS and BP
The baroreceptors send nerve impulse messages from the carotid artery through the Vagus nerve, which connects to the lower part of the brain stem. Depending on the pressure inside the carotid, the Vagus nerve alerts the brain stem to what is going on, and
adrenal medulla
(a bundle of nerve-type tissues) found on the tips of the kidneys release a chemical called adrenaline into the bloodstream.
-works with the brain stem to regulate bp.
Renin
- enzyme produced in the juxtaglomerular cells of the kidney.
Factors promoting release of renin:
1. A decrease in the pressure at the renal artery
2. an activation of the sympathetic nerve fibers to the kidney
3. a decrease in the amount of sodium passin
angiotensin I
- renin is converted to Angiotensin I
- angio I is converted to angiotensin II in the lung and other organs.
angiotensin II
Angiotensin II is a potent vasoconstrictor and will also stimulate release of aldosterone from the adrenal gland.
Aldosterone
increases sodium absorption at the kidney, thus allowing for fluid retention and increasing plasma volume
antidiuretic hormone (ADH)
- aka vasopressin
- a potent vasoconstrictor (increases pvr)
- plasma volume regulator
- release by the posterior pituitary
- ** reabsorption of water by the kidney
MOA of ADH
ADH will regulate plasma volume by resorption of water at the distal tubule of the nephron.
pericardium
is composed of a surface layer of mesothelium over a thin layer of connective tissue.
Central venous pressure
used to approximate the Right Ventricular End Diastolic Pressure (RVEDP). The RVEDP assesses right ventricular function and general fluid status.
- Low CVP values typically reflect hypovolemia or decreased venous return.
- High CVP values reflect overhydr
alpha receptors
- Epinephrine (E) and norepinephrine (NE) stimulate about equally well, and both are much more effective than isoproterenol (I). E >= NE >> I.
- Selectively stimulated by Phenylephrine.
blockers of alpha
- Selectively blocked by Phentolamine and Phenoxybenzamine.
alpha 1
- Predominant form
- Found primarily in the smooth muscles of arterioles, eye, gut, skin, veins, etc., as well as in some other cell types (like salivary glands).
- Usually causes contraction of smooth muscle cells.
alpha 2
- Found at pre-synaptic terminals of adrenergic nerves.
- Functions as an autoreceptor. If stimulated, it decreases the subsequent release of transmitter.
Beta
Isoproterenol stimulates best, epinephrine and norepinephrine
* I > E >= NE.
- Blocked by propranalol.
Beta 1
- Found in heart muscle and in the kidney.
- Causes increased heart rate and contractility.
- Promotes release of renin from the kidney.
Beta 2
- Found in smooth muscle that relaxes upon stimulation, and in metabolic tissues.
- Causes: Decrease in gastrointestinal motility.
Bronchodilation.
- Vasodilation in skeletal and cardiac muscle.
- Glycogenolysis in the liver.
EPI > NE. EPI can also stim
Beta 3
Found in adipose tissue (fat cells).
Stimulates lipolysis, increasing fatty acids in the blood
- EPI = NE
ANP
Atrial Natriuretic peptide - hormone, vasodilator, secreted by heart muscle cells in right atria as response to high bp.
- helps to reduce water, sodium, K+, (and fat) loads on circ system >> ? BP and volume
factors that control renin
1. drop in BP - detected by the juxtaglomerular cells as a ? in blood flow to kidney.
2. a ? NaCl delivered to kidney
3. ?-adrenergic stimuli = increase renin release and ?-adrenergic inhibitors = decrease
4. angioII - decrease renin release
5. low K+ con