A&P Term 3 Lab #3: Cardiovascular System I: Cardiac Physiology & Blood Vessel Histology Flashcards
The cardiovascular system consists of:
the heart and all the blood vessels
The heart consists of two receiving chambers, the ______.
atria (left and right atrium)
The heart consists of two pumping chambers, the ____
ventricles (left and right ventricles)
The left side of the heart pumps _______ blood and the right side pumps ________ blood
oxygenated, deoxygenated
The pulmonary circuit
all the blood vessels that take deoxygenated blood from the right ventricle of the heart to the lungs, and then return oxygenated blood to the left atrium
The systemic circuit
blood vessels that transport oxygenated blood throughout the body and returns deoxygenated blood back to the heart
All gas exchanges occur within ______
capillaries
Capillaries
microscopic blood vessels only one cell layer thick
What are capillaries walls made out of? why?
Their walls are made out of simple squamous epithelium, which permit the diffusion of gases such as O2 and CO2
O2 diffuses out of the blood and into body cells to be used in the process of _______ ________, whilst CO2 is a by-product of cellular respiration and gradually builds up within body cells before diffusing into the _______
cellular respiration, capillaries
The heart has two populations of cardiac myocytes. What are they? What is the percentage of each?
nonpacemaker cells = 99%
pacemaker cells = 1%
Nonpacemaker cells
regular/contractile myocytes
Pacemaker cells
specialized cells that have the unique property of spontaneously depolarizing and generating action potentials.
The action potentials they initiate trigger action potentials of the nonpacemaker cells.
The heart’s pacemaker cells are located in clusters throughout the heart, and together these clusters make up the ____ _____ ______
cardiac conduction system
Parts of the cardiac conduction system:
Sinoatrial (SA) node, Atrioventricular (AV) node, and the Purkinje system
Sinoatrial (SA) node (location + function)
located in the upper right atrium, where it acts as the main pacemaker of the heart. It depolarizes spontaneously around 60 times per minute (usually higher bc influence of the autonomic nervous system)
Atrioventricular (AV) node (location + function)
located in the lower right atrium, where it acts as backup pacemaker and is capable of pacing the heart at about 40 beats per minute
Conduction through the AV is ___, which is known as the __ _____ _____
slow, AV node delay
What is the function of the AV node delay?
allows the atria to depolarize and contract before the ventricles, which allows the ventricles to fill with blood.
Purkinje system
a group of pacemaker cells that transmitts impulses from the AV node to the ventricle
The myocytes of the purkinje system pace the heart slowly but conduct impulses more rapidly than the ________.
rest of the conduction system
3 components of the purkinje system
Atrioventricular (AV) bundle, Right and left bundle branches, Purkinje fibers
Atrioventricular (AV) bundle
small group of fibers in the lower interatrial septum and upper interventricular septum that transmits impulses from the AV node to the ventricles.
Right and left bundle branches
impulses are transmitted from the AV bundle down either side of the interventricular septum by the right and left bundle branches
Purkinje fibers
at the end of the interventricular septum, the right and left buncle branches fan out through the myocardium as the purkinje fibers. These fibers extend ⅓ of the way into the heart muscle before blending with the regular nonpacemaker cardiac myocytes.
Electrocardiogram abbreviations
(ECG or EKG)
what is an Electrocardiogram (ECG or EKG)?
a graph of the heart’s electrical activity as expressed in millivolts (mV) over time
Electrocardiograph
The instrument used to obtain an electrocardiogram (EKG)
A person is connected to the electrocardiograph with electrodes placed on…
the arms and legs (limb leads) and along the chest (chest leads)
An EKG is used to detect what?
if the electrical conduction pathway within the heart is normal and if any damage has been done to the heart
3 different waves appear on the EKG:
P, QRS complex, and T
P wave
atrial depolarization
at the end of the P wave, both atria have depolarized, which causes the atria to contract
QRS complex
ventricular depolarization
at the end of the QRS complex, both ventricles have depolarized, which causes the ventricles to contract
- atrial repolarization also occurs at this time but is masked by the ventricular depolarization
T wave
ventricular repolarization
at the end of the T wave, both ventricles have repolarized which causes the ventricles to relax
depolarization causes chambers to _____, and repolarization causes chambers to _____.
contract, relax
______ _________ also occurs during the _____ ______ but is masked by the ventricular depolarization
atrial repolarization, QRS complex
Abnormalities in EKGs is either ____ or ____
variation in wave height or variation in normal time intervals
variation in wave heights in EKGs and what they mean
→ If a P wave is elevated, it may indicate atrial enlargement
→ If the QRS complex is elevated, it may indicate ventricular enlargement
→ Tall and pointed T wave may indicate myocardial ischemia
normal EKG time intervals
→ P-R interval = time from beginning of P wave to start of QRS complex; 0.2 sec.
→ S-T segment = time from end of S wave to beginning of T wave; 0.1 sec.
→ Q-T segment = time from beginning of QRS complex to end of T wave; 0.4 sec.
*Any time longer or shorter than these normal intervals may indicate an abnormality
Blood pressure
the pressure exerted by the blood on the walls of the blood vessels
3 factors that determine blood pressure
cardiac output, peripheral resistance, and blood volume
Cardiac output
the amount of blood each ventricle pumps in one minute
stroke volume
the amount pumped with each beat
Peripheral resistance
any impedance to blood flow encountered in the blood vessels
vasoconstriction increases ____ ______
peripheral resistance
what increases peripheral resistance?
vasoconstriction
what decreases peripheral resistance?
vasodilation
_____ influences peripheral resistance
obstructions (like plaques within the arteries
blood volume
the amount of blood found within the blood vessels at any given time
what influences blood volume?
kidneys and hormones
Cardiac output and peripheral resistance can be altered _____ to change blood pressure, whilst alterations to blood volume occur ____.
quickly, slowly
systole
when the heart contracts
diastole
when the heart relaxes
sphygmomanometer
measures arterial blood pressure (w a stethoscope)
what measures arterial blood pressure?
sphygmomanometer
systolic pressure
the pressure in the arteries during ventricular systole (between 100-120 mmHg0
diastolic pressure
the pressure in the arteries during ventricular diastole
sounds of korotkoff
sounds that are generated when a blood pressure cuff changes the flow of blood through the artery
these sounds are heard through either a stethoscope or a doppler that is placed distal to the blood pressure cuff
Cardiac output (CO)
the amount of blood pumped out of a ventricle in 1 minute and is expressed in milliliters of blood per minute
Cardiac output equation
CO = SV x HR
Factors affecting SV
-Preload
-Contractility
-Afterload
Preload
the amount of tension in the ventricular cardiac muscle cells prior to contraction
Frank-Starling Law
the greater the tension on the cells, the more forcefully they contract
(ex. During exercise, more blood is returned to the heart and therefore stretches the cardiac muscle cells in the chambers, which results in a more forceful ejection of blood. This is why exercise increases SV)
Contractility
the degree to which cardiac muscle cells can shorten when stimulated by a specific chemical substance.
(ex. Low calcium can result in an irregular heartbeat, decreasing SV)
Afterload
the amount of force needed from ventricular cardiac muscle to eject blood from the ventricles and past the semilunar valves.
(ex. A blockage in a blood vessel would restrict blood flow and increase afterload. As afterload increases, stroke volume decreases)
Factors affecting HR
Age: HR gradually decreases from childhood to adulthood but in the elderly, it increases again to that of a young adult
Sex: Females have a slightly higher resting heart rate than males (5 bpm difference)
State of activity: HR decreases during certain phases of the sleep cycle and increases during exercise
Endurance training: athletes may have a resting heart rate of 50bpm. Endurance training increases heart size as well as SV. This allows for a normal CO with lower HR.
Stress/anxiety: increase HR
does cardiac output remain constant?
no
what controls cardiac output?
The cardiovascular center in the medulla oblongata maintains the CO in a normal range as well as hormones.
The _____ _____ and _____ ______ work together to regulate heart activity, thereby directly ensuring that a normal CO is achieved
nervous system, hormonal regulators
3 major circuits of blood flow and what they do
The systemic circuit: carries oxygenated blood from the left side of the heart to the body and returns deoxygenated blood to the right side of the heart
The pulmonary circuit: carries deoxygenated blood from the right side of the heart to the lungs and then returns oxygenated blood to the left side of the heart
Coronary circuit: delivers oxygenated blood to the heart itself for its metabolic needs
layers of the blood vessels
tunica interna, tunica media, tunica externa (or tunica adventitia)
what is tunica externa also known as?
adventitia
adventita
another name for the tunica externa
Tunica interna and its composition
the innermost lining of the blood vessel. Composed of a type of simple squamous epithelium called endothelium. Rests on top of a thin layer of connective tissue.
Tunica media and its composition
middle layer of the blood vessel wall. Composed of smooth muscle and elastic fibers.
The smooth muscle is innervated by the sympathetic nervous system and therefore controls the diameter of the vessel/plays an important role in tissue perfusion and blood pressure.
Elastic fibers allow the vessel to expand and return to its original state.
Tunica externa (or tunica adventitia) and its composition
outermost layer of the blood wall. Consists of dense irregular collagenous connective tissue and collagen fibers. Collagen fibers reinforce the blood vessel and prevent it from rupturing when pressure is increased.
