Exam 4 Flashcards
Heart
four-chambered organ that provides the drive for blood flow
11 oz. for average male
9 oz. for average female
Myocardium
heart muscle, myocardial fibers interconnect in latticework fashion to allow the heart to function as a unit
Stroke Volume
amount of blood being eject every time the heart beats
70 mL at rest
Cardiac Output
Stroke Volume x Heart Rate
5L = 70mL x 72
can change based off training or presence of disease
right side of the heart
receives blood returning from body
pumps blood to lungs for aeration through pulmonary circulation
deoxygenated
left side of the heart
receives oxygenated blood from lungs
pumps blood into thick-walled muscular aorta for distribution via systemic circulation
upper portion of heart
atrium
lower portion of heart
ventricles
atrioventricular valves (tricuspid)
provides one-way blood flow from the right atrium to right ventricle
atrioventricular valves (bicuspid/mitral)
provides one-way blood flow from left atrium to left ventricle
semilunar valves
located in arterial wall just outside heart; prevents blood from flowing back into the heart between contractions
13 steps of blood flow through the heart
- body
- inferior/superior vena cava
- right atrium
- tricuspid valve
- right ventricle
- pulmonary arteries
- lungs
- pulmonary veins
- left atrium
- mitral/bicuspid valve
- left ventricle
- aortic valve
- out to body
myocardial contraction
atrial chambers serve as “primer pumps” to receive and store blood during ventricular contraction
simultaneous contraction of both atria forces remaining blood into ventricles
almost immediately after atrial contraction, ventricles contract and propel blood into arterial system
systole
contraction phase
blood is pumped out of chamber
diastole
relaxation phase
blood fills chamber
Autorhythmaticity
ability of cardiac muscle tissue to initiate impulse for contraction at regular intervals
Sinoatrial node
pacemaker of cardiac contraction made up of specialized nervous tissue; initiates atrial contraction/systole
Atrioventricular node
delays impulse by 1/10 of second, allowing atria to contract before ventricles
Purkinje fibers
rapidly spreads impulse to contract ventricles in a synchronized manner
EKG (P wave)
atria contraction/depolarization
following P wave, pause due to AV node
EKG (QRS complex)
ventricular contraction/depolarization (atrial relaxation/repolarization occurs during this time but is obscured by ventricular activity)
EKG (T wave)
ventricular relaxation/repolarization
parasympathetic system
hyperpolarizes SA Node
sympathetic system
increases heart rate and stroke volume
arterial system
high-pressure tubing that propels oxygen-rich blood to tissues
layers of connective tissue and smooth muscle
no gaseous exchange occurs between arterial blood and surrounding tissues
metarterioles
arterioles branch and form smaller less muscular vessels
end in microscopically small blood vessels called capillaries that contain 6% of total blood volume
precapillary sphincter
consists of a ring of smooth muscle encircling the capillary at its origin and controls its diameter
constriction and relaxation provide a means for blood flow regulation within a specific tissue to meet metabolic requirements
Two factors trigger precapillary sphincter relaxation to open more capillaries
Driving force of increased local BP plus intrinsic neural control
Local metabolites produced in exercise
Ejection fraction (EF)
ratio of available blood to pumped blood
EF = SV/EDV (end-diastolic volume)*100
endurance training
can increase EDV, increasing SV & decreasing HR
can also increase plasma volume, which may increase ventricle filling and force of contraction by Frank-Starling
SV may increase because of increased ventricular contractility, ESV may decrease
moderately trained or untrained people
SV increases with exercise intensity up to 40% to 50% of peak oxygen consumption
Frank-Starling Mechanism
increased venous return stretches or “preloads” the ventricle, causing reactionary increase in contractile force of ventricle. This results in lower ESV
blood pressure in aorta increasing/high
If blood pressure in aorta increases, SV decreases
If blood pressure in an artery is high, EF into that artery can decrease. To overcome high blood pressure and increase EF, heart would have to work harder; if blood pressure is too high (hypertension), heart may not be able to supply sufficient oxygen, causing ischemia
Blood pressure
Cardiac output × Total peripheral resistance (TPR)
blood pressure mediation
Force of blood against arterial walls during cardiac cycle
Peripheral vessels do not permit blood to“run off” into arterial system as rapidly as it ejects from heart
Aorta “stores” some ejected blood, which creates pressure within the entire arterial system
Arterial blood pressure reflects the combined effects of arterial blood flow per minute and resistance to flow in peripheral vasculature
hypertension central mediation
via sympathetic hyperactivity
more Epi/Norep, more Angiotensin II
hypertension peripheral mediation
via damage to the endothelial wall
structural alterations - collagen vs. elastin
peptide release - reduced NO, too much Endothelin (ET-1)
Angiotensin II
hypertensive hormone, increases blood volume, big vasoconstrictor, increases blood pressure
exercise can help decrease the amount of angiotensin II we produce
venoconstriction
constriction of veins via sympathetic stimulation
veins contain 65% of blood volume, storage reservoirs/capacitance blood vessels
Muscle Pump
rhythmic muscle contractions propelling blood to heart through one-way valves of veins (prevents backflow and ensures that blood moves towards heart when pumped)
respiratory pump
changes in intrathoracic and intraabdominal pressure during expiration & inspiration, forcing blood in those cavities to flow toward heart
varicose veins
Valves within a vein fail to maintain one-way blood flow; blood gathers in vein so they become excessively distended and painful
Usually occurs in surface veins of lower extremities
People with varicose veins should avoid static, straining-type exercises like resistance training
Exercise does not prevent varicose veins, but regular exercise can minimize discomfort and complications
3 components of blood
plasma (55% of whole blood volume)
buffy coat (eukocytes and platelets less than 1%)
erthrocytes (45% of whole blood volume)
plasma
55% - 60% of total blood volume
may decrease in volume as much as 10% during intense physical activity
can increase as much as 10% at rest because of adaptations to training or acclimatization to hot, humid environments
platelets
important for blood clotting
contribute to heart attack, stroke, plaque build up
red blood cells
transport oxygen via hemoglobin
produced in bone marrow of long bones
4 month lifespan
nuclei removed when produce, can’t repair themselves
EPO
Erythropoietin
produced by kidneys and stimulates RBC in long bones
hypoxic environment helps to produce more EPO
blood supply of myocardium
coronary artery branches off aorta & supplies blood to heart (oxygenated)
blood pressure is highest in aorta
coronary artery branches into right & left sides
anastomosis
intercommunication between 2 arteries ensuring blood flow to area even if one artery is blocked
oxygen delivery to tissue
blood flow increases during exercise for delivery (oxygen, glucose, triglyceride) and removal (carbon dioxide)
oxygen delivery depends on…
amount of oxygen tissue takes out of blood flowing by it
fick equation
oxygen delivery = blood flow x a-vO2 diff
VO2 = oxygen consumption
Cardiac output (Q) = blood flow
VO2 = Q × a-vO2 diff
control of vasoconstriction and vasodilation
Release of norepinephrine by sympathetic nerves causes vasoconstriction of peripheral blood vessels
Release of epinephrine by sympathetic nerves can cause both vasoconstriction and vasodilation
autoregulation
changes in skeletal muscle during exercise that stimulate smooth muscle chemoreceptros in precapillary sphincters & increase vasodilation
O2 kinetic chain during exercise
Respiratory (up-take)
Central Circulation (transport)
Peripheral Extraction (use)
maximal oxygen uptake
the maximal amount of oxygen that can be consumed during dynamic exercise while breathing ambient air at sea level
(VO2max, maximal aerobic power, functional aerobic power)
rate limiting factor
physiological process when at its maximal level of function sets an upper limit (functionally) for entire oxygen kinetic chain
sets the limits of performance
central (Q)
heart rate x stroke volume: central
research has demonstrated a 20% increase in SV
physiological adaptations (SV)
Increased internal left ventricular volume and mass
Reduced cardiac and arterial stiffness
Increased diastolic filling time
Improved intrinsic cardiac contractile function
Increased plasma volume
Increased red blood cell volume
peripheral response (arteriovenous O2 difference)
amount of oxygen extracted by tissue
measurement of bodys skeletal muscle ability to extract and utilize oxygen
rest = 5ml/dl
max exercise = 16-18 ml/dl
physiological adaptations (A-VO2 diff)
Increased muscle-capillary density
Increased mitochondrial density
Increased hemoglobin
Ultimately equates to a rightward shift in oxyhemaglobin dissociation curve
detraining
occurs rapidly when a person terminates participation on regular physical activity
only 1-2 weeks of detraining reduces both metabolic & exercise capacity, many training improvements fully lost within several weeks
The relationship between blood volumes and pressure. How might an increased pressure in one of the chambers alter the blood flow dynamics?
As blood enters ventricle, pressure increases, more forceful contraction. During diastole, if pressure is increased, blood cannot enter the chamber as efficiently.
Contraction and blood volumes.
stroke volume is enhanced with exercise, end-diastolic volume is enhanced, we have more to pump so we can pump more out.
heart rate (mitochondria)
Grow the total number of mitochondria and mitochondria become larger = enhanced oxidative processes = enhanced O2 kinetic chain
How might exercise alter the blood flow and pressure relationships?
Endurance training increases EDV, increasing SV, decreasing HR
How might exercise improve hypertension?
Exercise diminishes angiotensin II helping to decrease hypertension.
