Chapter 5D - Cardiovascular System Flashcards
Describe the pump
The left heart pumps blood into the systemic circulation at the maximum pressure called “systolic pressure” varies from 100-140mmHg in healthy people.
Describe the primary function of the cardiovascular system
To supply the body with oxygenated blood containing the nutrients needed for metabolism, and to carry away the waste products
Describe the pipes
The arteries, arterioles, and capillaries that deliver blood to the body’s cells under pressure (diastolic pressure) varies from 60-90 mmHg
Venules and veins being blood back to the heart at very low pressure
Describe the fluid
The blood
Describe the right heart
The pulmonary heart
Receives the venous return of deoxygenated blood from the vena cava (preload) and pumps it to the lungs
Pump at lower BP than left heart
<30 mmHg systolic
+_ 10-20mmHg diastolic
Describe left heart
Systemic heart
Receives venous return of oxygenated red blood from the lungs and pumps it to the rest of the body.
There is much more resistance in all of the body’s arteries. (Afterload) so it has to work harder
Has greater coronary blood flow
Greater than or equal to 120mmHg systolic
Greater than or equal to 70mmHg diastolic
Gets 75% of all clots in MIs
If right heart is damaged?
Not able to deal with all of the venous return (preload) and that will cause this return to “back up” into the veins - overtime result in dependent edema.
If left heart damaged?
It will not be able to deal with all of the venous return from the lungs
Will cause a “back up” resulting in pulmonary edema
Explain “the amount of blood in the body occupies 1/5 of the available space “
The blood vessels are always fairly tightly constricted. If the “pipes” do not stay tightly constricted. You will go into shock, and/or faint.
If you have 5 quarts of blood, then if all vessels dilated at once it will take 25 quarts to fill them
How much blood does a person have?
A person has 1 quart of blood for every 30 pounds of body weight.
5-6 quarts for people weighing 150-180lbs
How much blood loss produces shock?
Loss of 15% of blood volume produces moderate shock
30% produces severe shock
Cardiac output
CO = SV x HR
Is the cardiac minute volume, the amount of blood pumped by the heart (left ventricle) in one minute. It is the same as the Stroke volume times the heart rate.
Define stroke volume
The amount of blood ejected by the left ventricle with each heart beat
Heart rate
Number of heartbeats per minute
Define ejection fraction
The percentage of blood in the ventricles that is linked out per beat
Usually 60%, but in CHF 20%
Define peripheral vascular resistance PVR
Pumping pressure of the arteries and arterioles - is is another way of saying Diastolic pressure. It is largely determined by the diameter of the blood vessels and their muscle tone.
Also called after load because it is the pressure the ventricles must beat against
Define diastolic pressure
The lower number in a blood pressure ( PVR)
Systolic pressure
Upper number of BP = the pumping pressure of the heart
Pulse pressure
Difference between the systolic and diastolic pressures (about 40-50mmHg)
Define Starling’s Law of the Heart
Says that within limits, the force of the heart’s contractions is primarily determined by diastolic filling - better the filling, the greater the stretch, the stronger will be the contraction
Based upon preload, the amount of venous return.
Define tachycardia
An abnormally rapid pulse rate = greater than or equal to 100 in adults
- usually indicates insufficient perfusion, so the heart speeds up to compensate.
Define bradycardia
An abnormally rapid pulse = less than or equal to 60 in adults
- may indicate several things, downer drug abuse, poisonings
Define automaticity
The characteristic of the heart to generates its own beat. The brain does not tell it when to beat, it does that on its own.
Brain can speed it up using sympathetic nervous system or slow it down using the parasympathetic nervous system via vagus nerve.
Blood pressure is a function of what.
Depends on the pumping contractility of the ventricles (reflected by the systolic pressure),
the stroke volume (which in part is a function of preload = the amount of blood returning to the heart [starlings law of the heart], ejection fraction and total body fluid volume),
the heart rate, PVR (how well the arterioles pump, reflected by the diastolic pressure)
RBC - basic function
Important in transporting O2 to cells
Contain hemoglobin to carry O2
WBC - basic function
Important in fighting infection
Platelets - basic function
Important in initiating the blood-clotting cascade
Plasma - basic function
The liquid portion of blood - acts as a transport medium for blood cells and nutrients, oxygen, ect.
Early systole - position of cardiac valves
As soon as ventricular contraction starts,
AV valves close
Semilunar valves are still closed. Pressure builds
Late systole - position of cardiac valves
At the point when the pressure inside the ventricles exceed the pressure in the aorta,
semi lunar valves open.
Diastole - position of cardiac valves
As the ventricles relax and the pressure falls,
Semilunar valves close
When pressure gets low enough, AV’s open.
Define atrial kick
Describes the way the atria work
They wait during ventricular diastole for the ventricles to almost completely fill
Then the atria contracts, “kicking” in just a little extra blood to help stretch the ventricles
Arteries and arterioles - characteristics
Carry blood away from the heart at fairly high pressure
Nerve controlled, and can constrict or dilate.
Thick-walled, made up of many layers of smooth muscle.
Carry oxygenated blood (exception is pulmonary artery)
Veins and venules - characteristics
Carry undersaturated blood back to the heart at fairly low pressure
Thin walled, containing several layers of smooth muscle, but due to thinness do not really pump the blood
Have one way valves to help move blood toward the heart
Capillaries - characteristics
One cell layer thick, with pores or openings where these cells meet
Allows plasma to flow out carrying oxygen and nutrients to the cells.
While capillaries cannot constrict not dilate, they are supplied with sphincter muscles (pre-capillary sphincters) that open to let blood enter a capillary bed whenever an area of cells runs out of oxygen, or become acidotic
Explain the mechanism for returning blood to the heart
- Gravity - vessels at head, neck, and shoulders
- Siphon effect - each time we inhale, the relative vacuum in the thoracic cavity helps draw in blood
- Pumped back by skeletal muscles squeezing the veins, this action is assisted with one way valves in the veins. ( most important)
Define perfusion
To pour through
Refers to the pumping of blood through capillary beds.
The pumping is provided by hydrostatic pressure.
Describe the requirements for adequate tissue perfusion (5)
- adequate blood volume
- adequate cardiac output
- adequate valves in the heart
- competent valves in the heart
- patent blood vessels
Explain how the amount of oxygen bound to hemoglobin affect skin color
Pink - adequate hemoglobin and adequate O2
Pallor - inadequate hemoglobin, adequate O2 Or, adequate hemoglobin and adequate O2 with vasoconstriction at the skin
Cyanosis - adequate hemoglobin, inadequate oxygen
Define anemia
Not having enough blood
- patient has lost blood or has too few red cells
- patient has enough blood, just with insufficient hemoglobin
- patient has red cells that are too small
Anemia - S/S
Pallor
Fatigue
Muscle weakness
Dyspnea on exertion
Edema - define
Is increased fluid trapped in the interstitial space
- it occurs when there is an increase in capillary pressure (from gravity) or from fluid backing up in the heart, lungs, or liver, resulting in the inability of venules to get rid of all the blood entering them (CHF)
- it can occur when there is an increase in capillary permeability as happens with acidosis or hypoxia (allergies cause it due to the actions of histamines)
Define venous pooling
Results in an increase in the amount of blood staying in the veins, and occurs when:
– there is a decrease in skeletal muscle activity, such as occurs with prolonged sitting – such as a long airplane flights
– there is a drug reaction that causes vasodilation – such as with nitroglycerin, or histamine
Baroreceptors - define, location, and function when stimulated
Baroreceptors or pressure receptors located in the aortic arch and carotid artery. They detect increases in pressure around them, and provide a feedback signal to the brain stem that helps regulate blood pressure. If they detect an increase in blood pressure, they signal the brain which sends a signal down the Vegas nerve to cause the heart to slow down – the decrease in heart rate will decrease cardiac output and help drop BP
Inotropic effect – define
Refers to the force of contraction
Chronotropic effect – define
Refers to the speed of the heart
Dromotropic effect - define
Refers to the conduction system of the heart
Heart rate – how changes alter stroke volume and cardiac output
- As heart rate slows down, cardiac filling time improves, usually resulting in increased stroke volume
– as rate speeds up, Cardiac filling time diminishes, decreasing stroke volume
Increased stroke volume will increase cardiac output and decreased stroke volume will decrease cardiac output
Venous return – how changes alter stroke volume and cardiac output
Due to starlings law of the heart, stroke volume and cardiac output are very dependent on venous return
– if venous return drops, so does stroke volume and cardiac output
Ventricular contractility – how changes alter stroke volume and cardiac output
If contractility is reduced due to ischemia, or infarct, or medication, the Myocardium becomes less efficient resulting in decreased stroke volume and less cardiac output
– congestive heart failure is partly due to decreased contractility and a decrease in ejection fraction
Atrial kick – how changes alter stroke volume and cardiac output
If atrial kick is lost (as in atrial fibrillation), there is a drop in ventricular filling of about 20%. This makes the heartless efficient per beat
List the five characteristics of the myocardial tissue
Automaticity rhythmicity Conductivity Contractility Irritability
Automaticity- define
The ability to initiate its own impulses. This is its own internal pacemaker.
Rhythmicity- define
The ability or tendency to set a predictable pattern.
Conductivity - define
The ability to transfer electrical impulses from one cell to another
Irritability- define
The ability to respond to an impulse or stimulus.
Explain the “all or none phenomena”
The characteristic of the heart to contract as a unit, with all muscle cells contracting together. Your biceps on the other hand can selectively contract only 30% or 50% of its muscle fibers to lift a given object
Describe the normal pathway of an electrical stimulus through the heart
- The sinoatrial node spontaneously fires
– the signal spreads throughout the atria causing them to contract (the impulse also travels through the intra-atrial fibers)
– the atrioventricular node receives impulses, pauses to aid in ventricular filling, and then fires the signal down the bundle of His
– the bundle of his carries the impulse to the bundle branches
– the bundle branches carry the impulse to the purkinje fibers
– the purkinje fibers for the ventricles from the bottom up
Intrinsic rate of depolarization of the heart
SA Node - 72 AV node - 60 Bundle of his - 54 Bundle branches - 46 Purkinje fibers - 40
Intrinsic range of depolarization of the heart
SA Node - 60-100 AV Node - 40-60 Bundle of his - 40-60 Bundle branches - none Purkinje fibers - 20-40
Explain the significance of these intrinsic rates
With the stimulation by the autonomic nervous system, the heart would be led by the SA node to beat a roughly 72 bpm.
In the event of an infarct damage in SA node, the AV node would take over as a back up pacer, but it would be at about 60 bpm
Describe why increases in heart rate affect myocardial perfusion through the coronary arteries
The openings of the coronary arteries are behind the aortic valve leaves.
Due to being partially covered during systole, and as arteries are compressed during systole, the only time the heart is resupplied with blood is during diastole.
As the heart speeds up, systole remains at almost the same duration (blood is thick and takes a certain amount of time to move).
It is diastole that shortens most when the heart speeds up. Therefore, during tachycardia, the heart works harder, But receives less blood per heartbeat.
Describe when it is important to auscultate the apical pulse
– To determine death under policy #814
– when the patient is in pulseless electrical activity
– pediatrics when pulses are difficult to obtain
Hemodynamic response – describe
Is the patients signs/symptoms in response to a particular level of perfusion.
As with PEA do not treat the monitor evaluate the patient’s hemodynamic response
Pulses paradoxes – define/describe
An anomaly of blood pressure that is tied to starlings law of the heart – in that during inhalation, momentarily there is a drop of intrathoracic pressure and that may cause a Drop in systolic blood pressure during that breath. This is found in severe obstructive pulmonary disease, severe respiratory distress or constrictive pericardial disease.
An example would be that you hear the first sound at 136 and it thumbs until it reaches, say 130, at which time the patient inhaled forcefully and you note that the sound disappears for several beats, only returning when he exhales again. If it is then steady at 120 regardless of breathing, than the fact that the period of silence was greater than 10 mmHg makes this a positive pulses paradoxes
Pulses alternans – define/describe
Alternating normal pulses followed by a much weaker one. This is found in severe left ventricular failure. This is more often heard it and then fell.
An example would be, given a regular pulse of 60 bpm, you hear the first sound at say 130 mmHg, then you hit 120, the pulse rate doubles to 120 bpm. Then what happened was that originally you were only hearing the stronger beats, not the weaker ones. If the patient is on an ECG at the same time this would be obvious. at the beginning of the monitor would show a pulse of 120, but when taking a BP you would only, initially hear a sound every second 60 bpm until the cuff pressure gets low enough
Auscultatory gap - define/describe
Something similar to pulses paradoxes except that it does not occur during inhalation. This is found in some patients with hypertension.
An example would be that you hear the first sound say at 200 mmHg and continues until 180 at which time it vanishes, only to reappear again at 130, with a diastolic at say 100 if this is not recognize, it would result in an incorrect BP being recorded as 130/100 (having miss the upper sounds) an indication that this is not likely is that the pulse pressure is too narrow in this range.
The blood pressure should be recorded as 200/100 within auscultatory gap from 180 to 130
