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A&P lecture exam 2 review
Terms in this set (45)
layers of the heart and their special features
•Pericardium (coverings of the heart):
-Heart is enclosed by the pericardium: a double-walled sac coverings-protection against friction and anchor.
-Fibrous pericardium: superficial layer, loose-fitting, collagenous structure that stabilizes the heart's position
-Serous pericardium: deeper, a 2 layered serous membrane
-Parietal layer lines internal surface of fibrous pericardium
-Visceral layer is the external covering of the heart. It is a.k.a. the epicardium
-Pericardial cavity is the space between the parietal and visceral layers. It is filled with serous fluid that provides a friction-free environment
-Pericarditis: infection of the pericardium
characteristics of the 4 cavities of the heart and their functions
•4 chambered organ with 2 superior atria and 2 inferior ventricles
•Interatrial septum divides the 2 atria
Small and thinly muscle
Atrial muscle contraction is only used to propel a small amount of blood to the ventricle below. (Most blood traveling from the atria to the ventricle does so by gravity)
•Interventricular septum divides the 2 ventricles
•Right Atrium: receives blood from 3 sources
Superior vena cava (deoxygenated blood returning from the arms, head, and upper torso)
Inferior vena cava (deoxygenated blood returning from the legs, abdomen, and pelvis)
Coronary sinus (deoxygenated blood returning from the coronary circulation)
•Passes blood to the right ventricle thru the tricuspid orifice which is associated with the tricuspid valve
Receives oxygenated blood from the 4 pulmonary veins
Passes blood to the left ventricle via the mitral orifice which is associated with the mitral (or bicuspid) valve
Shallow depression in both sides of the interatrial septum is known as the fossa ovalis
It is a remnant of the foramen ovale, a hole in the fetal heart that allowed blood to pass from the pulmonary circuit to the systemic circuit (since the lungs are neither fully developed nor being oxygenated)
Large, muscular chambers.
Thick musculature is necessary because they are the actual "pumps."
Right ventricle discharges blood into the pulmonary trunk, the first vessel of the pulmonary circuit.
The pulmonary semilunar valve separates the right ventricle and the pulmonary trunk.
Left ventricle discharges blood into the aorta, the first vessel of the systemic circuit.
The aortic semilunar valve separates the left ventricle and the aortic trunk.
Left ventricle is larger (more muscular) than the right.
-More muscle is necessary because the left ventricle pumps blood against greater pressure (note- the right and left ventricle pump the same volume of blood per beat)
Flow of blood in systemic and pulmonary circuit
•Heart consists of 2 pumps connected in series. Each pump sends blood to a different circuit.
•Pulmonary circuit- between the heart and the lungs.
•Systemic circuit- between the heart and the body tissues.
•Right side of the heart receives deoxygenated blood from the systemic circuit and pumps it thru the pulmonary circuit.
•Left side of the heart receives oxygenated blood from the pulmonary circuit and pumps it thru the systemic circuit.
Valves of the heart and their pathologies
•Are necessary to ensure 1-way flow.
•Are found between the atria and ventricles (the 2 atrioventricular valves) and between each ventricle and its great artery (the 2 semilunar valves).
•Consist of 2-3 flaps of connective tissue covered by endothelium.
abnormal heart sound due to a malfunctioning valve
a heart rate that is persistently lower than 60bpm (50) is termed
the decrease in blood vessel diameter caused by smooth muscles contraction
the hydraulic force that blood exerts upon the vessel walls
narrowing of the opening of a valve
abnormal blood supply
inadequate blood supply
the increase in blood vessel diameter caused by smooth muscle relaxation
the volume of blood ejected by each ventricle in one minute
heart at rest
temporary and reversible ischemia which produced a sense of pain
Myocardial infraction or heart attack
prolonged ischemia (perhaps due to a coronary blockage) which leads to myocardial cell death, (Angina pectoris and myocardial infarction are not synonymous terms).
a malfunction where one or more valve flaps bulge backward into the atria
a heart rate that is persistently greater than 100bpm
is a condition in which a clot dislodges and circulates through the bloodstream
condition of rapid and out-of-phase contractions (the depolarization and contraction is not coordinated)
any damage to the AV node. Can vary in severity. Damage to the AV node can result in a reduced ability or an inability of the electrical signals to pass from the atria to the ventricles
an abnormal pacemaker. A region of the heart becomes hyperexcitable and generates impulses faster than the SA node (take over the pacemaker role). Can lead to premature ventricular contractions - the most dangerous.
normal pattern of impulse conduction through the heart
•Cardiac muscle cells--
1.)Contractile (99%) - generate the force involved in pumping
2.)Autorhythmic (1%) - spontaneously depolarize to set the rate of cardiac contraction
•Groups of autorhythmic cells are found at the:
oSinoatrial node- located near the opening of the superior vena cava
oAtrioventricular node- located in the inferior interatrial septum near the tricuspid orifice
oAtrioventricular bundle- found in the superior interventricular septum. A.k.a. the bundle of His.
oRight and left bundle branches- travel thru the interventricular septum to the apex of the heart
oPurkinje fibers- cells that elaborate throughout the ventricles
oThe above list also gives the path of the electrical conduction system within the heart
effect of the sympathetic and parasympathetic nervous system (Vagus) on the heart
•The autonomic nervous system provides a large influence on the activity of the heart
•The medulla oblongata contains cardiac centers that can alter and influence the heart's activity
•The cardioacceleratory center contains sympathetic neurons that project to the SA node, AV node, and the bulk of the myocardium
•These sympathetic neurons release norepinephrine onto the cardiac cells: increase in heart rate and in the heart's contractile strength
•The cardioinhibitory center contain parasympathetic neurons that project to the SA node and the AV node via cranial nerve 10 (the vagus nerve)
•These neurons release acetylcholine onto the cardiac cells. This results in decreased heart rate but no change in the heart's contractile strength
•At rest, both parasympathetic and sympathetic neurons are releasing neurotransmitters onto the heart, but the parasympathetic dominates
•Hormones such as epinephrine (released by the adrenal medulla), thyroxine (released by the thyroid gland), glucagon and others affect heart rate
Cycles of the heart
•Includes all the events associated with the blood flow thru the heart during one complete heartbeat.
•For any one chamber in the heart, the cardiac cycle can be divided into 2 phases:
oSystole = contraction
oDiastole = relaxation
As we work through the systole and diastole of the cardiac cycles, there is one abiding principle that we must keep in mind:
Blood will only flow from point A to point B if the pressure at point A is greater than at point B.
•The cardiac cycle can be broken down into 4 phases:
Ventricular filling (first step of cardiac cycle)
a)Blood pressure within the left atrium is lower than within the pulmonary vasculature, so blood is entering the left atrium.
b)Blood continues to flow rapidly down the pressure gradient into the left ventricle.
•The av valves must be OPEN at this moment. Why?
c.)No muscle contraction is involved yet. At this point both the left atrium and the left ventricle are in diastole.
d.)About 80% of the ultimate ventricular volume will enter in this passive manner.
e.)Next, ventricular pressure begins to rise (as blood flows in), the filling rate decreases. While the ventricle is still relaxing, SA node will depolarize. The resulting atrial depolarization will cause atrial systole. The contraction of the atria completes the filling of the ventricles (final 20%).
i.The final ventricular volume (achieved just prior to the beginning of ventricular systole) is known as the end diastolic volume (EDV) and is typically about 130ml.
f.)For the rest of the cycle, the atrium will be in diastole.
g.)During this entire phase, the AV valve is open while the semilunar valve is shut.
Isovolumetric Contraction (second step of cardiac cycle)
•The atria repolarize and remain in diastole for the rest of the cardiac cycle
•Meanwhile, the ventricles depolarize and begin to contract; the pressure within it rises quickly.
•Blood surges upward and the AV valves are forced shut - this causes the first of the 2 heart sounds that can be auscultated with a stethoscope (phonetically it's given as LUB).
•It doesn't take much pressure to build-up before the AV valves are closed.
•However, it takes a lot more pressure to open the semilunar valves.
•After the AV valves are closed, the heart continues to contract as it tries to generate enough pressure to open the semilunar valves but until ventricular pressure exceeds aortic pressure, the aortic semilunar valves remains shut.
•During this time, the ventricular pressure is rising (because the ventricles are contracting) but the ventricular volume is not changing.
•Thus, this period is known as isovolumetric contraction.
•Isovolumetric contraction refers to the short period during ventricular systole when the ventricles are completely closed chambers.
Ventricular Ejection (third step of cardiac cycle)
•Ejection of blood begins when ventricular pressure exceeds arterial pressure - about 120mmHg in the LV and 25mmHg in the RV. Blood spurts out of each ventricle rapidly at first and then more slowly.
•The ventricles do NOT expel all their blood.
•The amount ejected (~70ml) is known as the stroke volume (SV).
•The blood remaining in the ventricles is known as the end systolic volume (ESV). ESV is typically about 60mL.
Isovolumetric Relaxation (fourth step of cardiac cycle)
•The ventricles now repolarize and begin to relax (enter diastole).
•Pretty quickly, the pressure in the aorta and pulmonary trunk exceeds ventricular pressure and the semilunar valves shit (this causes the 2nd heart sound - the DUP). Normal heart sounds are caused by closure of the heart valves.
•However, it takes a lot longer for ventricular pressure to drop below atrial pressure. Before this happens, the ventricles are relaxing and pressure is dropping, but the volume is not changing - Thus, this phase is known as isovolumetric relaxation.
•When ventricular pressure does drop below atrial pressure, the AV valves open and ventricular filling begins anew with another round of ventricular filling.
Cardiac Output and the factors that influence it
•Cardiac output is the amount of blood pumped by each ventricle in one minute.
•Cardiac output can be exposed mathematically as the product of heart rate and stroke volume: CO(mL/min) = HR(beats/min) X SV(mL/beat).
•Factors Affecting Heart Rate:
Recall that the cardiac centers in the medulla oblongata exert influence on the rate of SA node depolarization, heart rate. Let's examine some factors that could cause a change in heart rate:
o Increased heart rate can be caused by:
•Increased output of the cardioacceleratory center. In other words, greater activity of sympathetic nerves running to the heart and a greater release of norepinephrine on the heart.
•Decreased output of the cardioinhibitory center. In other words, less vagus nerve activity and a decrease in the release of acetylcholine on the heart.
•Increased release of the hormone epinephrine by the adrenal glands
•Caffeine •Hyperthyroidism- i.e., an overactive thyroid gland. This would lead to an increased amount of the hormone thyroxine in the blood.
Relation between Cardiac Output and Heart rate or Stroke volume
•Stroke Volume is governed by 3 factors:
•Preload is the amount of tension in the ventricular myocardium just prior to contraction
1.)The greater the heart muscle is stretched, the more forceful its contraction (more optimum cross-bridge formation between actin and myosin and a stronger contraction, thus ejecting a larger volume).
oThe strength of the heart's contraction independently of its degree of stretch
oAn increase in contractility will result in an increase in stroke volume and a decrease in end systolic volume
oThe pressure that must be overcome for the ventricles to eject blood is known as afterload. Afterload refers to the blood pressure just outside the semilunar valves (in the aorta and pulmonary trunk).
oRecall that in order for ventricular ejection to occur, the semilunar valve must be opened. In order for the semilunar valve to open, ventricular pressure must exceed arterial pressure. This arterial pressure is equivalent to afterload.
oAnything that increases arterial blood pressure will increase afterload. This makes the heart expend more energy on opening the semilunar valve and less on ejecting blood. Thus, an increase in afterload will cause stroke volume to decrease and end systolic volume to increase.
Starling Law of Heart
The more stretched the heart fibers are at the beginning of the contraction, the stronger is their contraction.
-The result is that as end diastolic volume increases, stroke volume increases.
The Frank-Starling law sums up the effect of preload by stating, "Whatever returns to the heart will get pumped out of the heart."
In other words, as venous return (the volume of blood returning to the heart per minute) increases, EDV increases, and SV increases.
-Carry blood away from the heart
-As they move away from the heart, they branch repeatedly, forming smaller and smaller arteries and eventually the smallest arteries - the arterioles.
-Typically carry oxygenated blood (exceptions - the pulmonary arteries and umbilical arteries).
-Carry blood toward the heart.
-As they move toward the heart, they converge and join, forming larger and larger vessels.
-Smallest veins are the venules, which receive blood from capillaries.
-Typically carry deoxygenated blood (exceptions - the pulmonary veins and umbilical veins).
-Smallest and most numerous
-Sites of exchange between blood and tissue fluid
-Exchange is facilitated by their thinness and vast number (more than a billion - SURFACE AREA
-"connect" arteries and veins.
Layers of the blood vessels and how they differ in arteries, veins and capillaries
•Tunica Adventitia: outermost layer. Made primarily of loose connective tissue. Anchors the blood vessel to the surrounding tissue.
•Tunica Media: consists primarily of smooth muscle and is responsible forvasoconstriction and vasodilation. Usually the thickest layer in arteries.
•Tunica Intima: Endothelium overlying sparse connective tissue. Acts as a selectively permeable barrier to blood solutes. Secretes vasoconstrictors and vasodilators. Provides a smooth surface and repels blood cells and platelets. Note that capillaries contain only a tunica intima.
factors that contribute in returning of blood flow to heart
•Skeletal Muscle Pump: the contraction/relaxation cycles of skeletal muscles squeeze the veins forcing the contained blood towards the heart.
•Respiratory Pump: as we inhale, our thoracic cavity expands while our abdominal cavity compresses. This causes thoracic cavity pressure and thus pressure within veins of the thoracic cavity to drop. Meanwhile, pressure in the abdominal veins increases. This combination results in increased blood flow towards that heart.
•Venous Valves: 1-way valves (similar to the semilunars of the heart) made of flaps of endothelium are found in medium veins (mostly in the legs and the arms) where they help prevent backflow.
What are the blood pressure and pulse pressure? How is hypertension related to atherosclerosis?
•Arteriosclerosis - any of a group of chronic diseases in which thickening, hardening, and loss of elasticity of the arterial walls result in impaired blood circulation
•Atherosclerosis - a form of arteriosclerosis characterized by the deposition of plaques containing cholesterol and lipids on the innermost layer of the walls of large and medium-sized arteries
•Blood flow - the volume of blood flowing through a vessel, an organ, or the entire circulation in a given period (e.g., ml/min).
Under resting conditions, blood flow thru the entire vascular system is equal to cardiac output and is relatively constant
If blood flow does not keep pace with tissue metabolism, then tissue necrosis (death) can occur
Blood flow to individual organs varies greatly
•Blood pressure is the hydraulic force that blood exerts upon the vessel walls (expressed in millimeters of mercury- mmHg)
It is determined primarily by cardiac output, total peripheral resistance and blood volume
All vessles have an associated pressure; however, the term "blood pressure" typically refers to arterial pressure
Similar to what we saw .. the heart; it is differences in blood pressure (i.e., pressure gradients) that drive (not done)
-Mathematically, the difference between the systolic and diastolic BP's is known as the pulse pressure: PP = SBP - DBP.
-If SBP is 125 and CBP is 75, then pulse pressure =50.
any condition in which blood vessels are inadequately filled and blood cannot circulate normally.
oMost common type
oResults from large-scale fluid loss- acute hemorrhage, severe vomiting, severe diarrhea, or extensive burns.
oCommon Signs include:
Fast pulse rate- in an attempt to increase cardiac output and blood flow
Weak, thready pulse- with decrease blood volume, venous return, and thus, stroke volume decrease
Cold clammy skin- in response to peripheral vasoconstriction as the body attempts to divert blood to essential areas.
blood volume is normal, but extreme vasodilation prevents proper circulation
vasodilation due to massive systemic allergic rxn and massive histamine release
vasodilation due to failure to maintain vasomotor tone
*vasodilation due to bacterial infection.
•Many bacteria release toxins that are extremely potent vasodilators
•Skin is warm rather than clammy because of the extreme peripheral vasodilation.
circulatory failure due to failure to the heart's pumping ability
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