Flashcards in Bergdahl - Chapter 15 and 16 Deck (81):
what is the weight of the heart ?
300 g for male
250 g for female
what is the main purpose of the heart ?
provides the drive for blood flow
what is the volume the heart pumps for each beat ?
70 mL/ beat
what is the heart muscle called ? how does it look ?
its fibers interconnect in latticework fashion to allow the heart to function as a unit (intercalated disc)
what is the main purpose of the right side of the heart
receive blood returning from throughout the body
what is the main purpose of the left side of the heart
receive oxygenated blood from the lungs
what are the two atrioventricular vales ?
- tricuspid : from right atrium to right ventricle
- bicuspid (mitral): from left atrium to left ventricle
what are the semilunar valves ?
located in arterial wall just outside the heart, prevent blood from flowing back into the heart between contractions
what is the role of atrial chambers ?
they work as primer pumps to receive and store blood during ventricular contraction
describe the gas exchange between arteries and surrounding tissues
THERE IS NONE
because of the thickness of the arteries
what do the walls of arterioles contain ? what do they do?
smooth muscle cells that constrict or relax to regulate blood flow to the periphery
what creates pressure within the entire arterial system ?
the storage of a portion of the blood in the aorta.
what is the formula for BP ?
BP= CO x TPR
basically the effect of arterial blood flow / minute and the resistance to that flow
what is systolic blood pressure ? what does it indicate ?
estimate of the work of the heart and force that blood exerts against the arterial walls during ventricular systole
what is diastolic blood pressure ? what does it indicate ?
the relaxation phase of the cardiac cycle, indicates peripheral resistance or the ease that blood flows from the arterioles into the capillaries
what are the values for normotensive ?
what are the values for prehypertension ?
SBP 120-139 mmHg OR DBP 80-89 mmHg
what are the values for stage 1 and 2 hypertension ?
SBP > 140 mmHg OR DBP >90 mmHg
SBP > 160 mmHg OR DBP > 100 mmHg
how is cardiac output related to MAP and TPR ? what are the implications of this
CO = MAP
resistance decreases dramatically during strenous physical activity. MAP increases (SBP increases considerably), and CO therefore increases
what is mean arterial pressure ? how much is it ? how do you calculate it ?
average force exerted by blood against the arterial walls during a cardiac cycle
90 mmHg at rest
MAP = DBP + 1/3 (SBP-DBP)
capillaries hold what percentage of blood volume ?
what is the role of the precapillary sphincter ? (and what is it?)
it's a ring of smooth muscle that encircles the vessel and controls capillary diameter
controls blood flow to meet metabolic requirements
what are the two factors that trigger the relaxation of precapillary sphincters ?
1) driving force of increased local blood pressure and intrinsic neural control (P1-P2)
2) local metabolites produced in exercise (R)
what is the formula for regulation of blood flow ?
flow = (P1-P2) / R
what is the difference between venous and mixed-venous blood ?
mixed (a- v) avec barre
mixed comes from all of the veins in the body that go into RA and that enters right atrium
what ensures that blood only flow in one direction towards the heart in venous return ?
valves within the vains
minor changes where will readily compress the veins ?
small muscular contractions or minor pressure changes in the thoracic cavity will readily compress the veins
what would happen without venous valves ?
blood would stagnate in veins of the extremities and people would faint because of reduced venous return and cerebral blood flow
what are varicose veins ? where are they usually found ?
conditions in which the valves within vein fail to maintain one-way blood flow and blood gathers in them so they become distended and painful
usually in surface veins of lower extremities
what are exercise recommendations for varicose veins ?
no static, straining-type exercises that accompany resistance training
regular exercise does not prevent varicose veins but can minimize complications because repeated muscle action can propel blood toward the heart
why is straining exercise so bad for people with heart and vascular disease ?
the muscle and ventilatory pumps provide little venous return. this compresses the peripheral arterial vessels supplying the active muscles. there is an acute cardiovascular strain due to the increase in SNS, CO, and MAP
what populations is hypertension more prevalent in
- older people
what exercise will make them have the highest BP ?
leg press with heavy load.
lying down will increase EDV so more blood will return to heart
what happens to the cardiovascular system during rhythmic steady rate muscular activity (jogging, swimming) ? (TPR, BP)
vasodilation in active muscles
reduces TPR to enhance blood flow
as activity continues, SBP will decrease due to continued vasodilation and reduction of resistance to blood flow
DBP remains unchanged
what happens to SBP, DBP, TPR in graded exercise tests?
TPR is reduced to enhance blood flow
SBP: rapid rise and then increase linearly with exercise intensity. can go up to 200 mmHg or higher, probably due to large CO in some athletes
DBP: remains stable or decreases slightly at the higher exercise levels
how does blood pressure in upper body exercise compare to blood pressure in lower body
exercise with the arms produces higher SBP and DBP than leg exercise performed at a given VO2 max
this is because the smaller arm muscle mass and vasculature offer greater resistance to blood flow than the larger leg mass and blood supply
therefore individuals with cardiovascular problems should exercise large muscle groups in contrast to exercise that engages a limited muscle mass.
how does blood pressure look in recovery ?
temporarily falls below pre-exercise levels due to a peripheral vasodilation
hypotensive response that can last up to 12 hours
what is the blood supply of the heart ?
the coronary circulation
what are the vessels in the coronary circulation ?
right and left coronary arteries (most go into left artery- LA- LV- RV)
for return: blood goes through anterior cardiac veins and leaves through coronary sinus and RV
what is the normal blood flow to myocardium at rest ?
200-250 mL/ min
at rest, how much of the oxygen does the myocardium extract from the blood in the coronary vessels ?
what is the sole mechanism to increase myocardial oxygen supply ?
a proportionate increase in coronary blood flow in exercise
why would coronary blood flow increase in exercise ? (2 reasons)
1) elevated myocardial metabolism dilates the coronary vessels
2) increased aortic pressure during exercise which forces a greater volume of blood into the coronary circulation
does the myocardium depend on oxygen supply ? can it function without ?
it needs an adequate oxygen supply since it has limited anerobic capacity.
how does tissue hypoxia stimulate myocardial blood flow ?
is a potent stimulus and can produce chest pains, or angina
how can we effectively evaluate the adequacy of myocardial blood flow ?
where is the greatest mitochondrial concentration of all tissues found ?
what provides energy for myocardial functioning ?
glucose, fatty acids, lactate
at rest, where does most of the energy come from to the myocardium ?
following a meal, where does the myocardium get most of its energy ?
during intense exercise, where does the myocardium get most of its energy ?
what is the inherent rhythmicity of cardiac muscle ?
what is the time delay between SA and AV node ? what for ?
this allows atria to contract and propel blood into the ventricles below
what is the transmission path of the cardiac impulse like ?
SA- Atria- AV- Purkinje- Ventricles
what does the ECG represent ?
a composite record of the heart's electrical events during a cardiac cycle
how does the heart function as two separate pumps ?
one pump receives blood from the body and pumps it into the lungs
the other pump receives oxygenated blood and pumps it throughout the systemic circulation
what is the intrinsic regulation of the heart rate ?
the SA node
what is the extrinsic regulation of the heart rate ?
input from the brain- SNS and PNS
what exactly does extrinsic control do in terms of changing HR ?
nerves directly supply the myocardium and chemical messengers. accelerate the heart in anticipation before exercise begins, and rapidly adjust to the intensity of physical effort
where is the cardiovascular control center found ? where does the input come from ? what does the output do ?
in the ventrolateral medulla
brain and peripheral NS constantly bombards it
in response, the center regulates heart output and blood's preferential distribution to all the body's tissues
can the inherent rhythm of the myocardium be overriden ? by what ?
by extrinsic neural influences that come from SNS and PNS
how are SNS and PNS fibers distributed in heart
SNS and PNS in atria of heart
SNS in ventricles
what happens if you stimulate cardioaccelerator nerves ?
release of catecholamines (NE, E)
what does sympathetic stimulation do to blood vessels ?
vasoconstriction, except in coronary arteries
what is the chronotropic effect of catecholamines ?
accelerate SA node depolarization, meaning the heart beats faster (tachychardia)
what is the inotropic effect of catecholamines ?
increase myocardial contractility
what molecule do parasympathetic axons release ?
what does ach do to the heart ?
it retards the rate of sinus discharge and slows the HR (bradychardia)
stimulation of what nerves result in bradychardia ?
the 2 vagus nerves that originate in the medulla's cardioinhibitory center
is PNS excitatory or inhibitory ?
what effect does vagal stimulation have on myocardial contractility ?
at the start of and during low/moderate intensity effort, HR increases through what mechanism ?
inhibition of parasympathetic fibers.
in strenuous exercise, HR increases through what mechanism ?
additional PS inhibition and direct activation of sympathetic fibers
what continually modulates medullary activity ?
impulses originating in the brain's higher somatomotor central command center
what provides the greatest control over the heart rate during exercise ?
when is central command operating >
during exercise but also in the anticipatory period
what does neural input from central command coordinate ?
the rapid adjustment of the heart and blood vessels to maximize tissue perfusion and to maintain central BP
cardiovascular center receives peripheral input from where?
what do peripheral receptors do to monitor the heart ?
modify PS or SNS outflow to bring about appropriate cardiovascular and respiratory responses to various states of physical activity
what are the three mechanisms that peripherally continuously assess the nature and intensity of exercise and the mass of muscle activated ?
1) reflex neural input from mechanical deformation of type III afferents within active muscles
2) chemical stimulation of type IV afferents within active muscles (more rapid feedback)
3) feed-forward outflow from motor areas of central command