cardiovascular system Flashcards
Name the type of receptors for norepinephrine on cardiac muscle?
beta-adrenergic
Name the type of receptors for acetylcholine on cardiac muscle?
muscarinic
Which blood vessels supply blood to the myocardium?
The coronary arteries
factors that limit the increase in SV (and thus cardiac output):
- very rapid heart rate which decreases diastolic filling time
- inability of the peripheral factors favoring venous
return (skeletal muscle pump, respiratory pump, venous
vasoconstriction, arteriolar vasodilation) to increase
ventricular filling further during the very short time
available
An individuals VO2 max can be altered by?
habitual level of physical activity
Increase in SV due to training is caused by:
effects on the heart (hypertrophy + increase in chamber size)
peripheral effects (increased blood vol + number of blood vessels = increased muscle blood flow + venous return)
How does aging influence heart performance during exercise?
decrease in max heart rate (+ cardiac output) due to increased stiffness of heart which decreases its ability to rapidly fill during diastole
How is the left ventricle affected by hypertension?
It has to pump blood against an increased arterial pressure = develops adaptive increase in muscle mass called left ventricular hypertrophy
Primary hypertension
hypertension of uncertain cause
secondary hypertension
when there is an identified cause
potential genetic causes of primary hypertension?
genes coding for enzymes involved in the renin-angiotensin-aldosterone system and some involved in the regulation of endothelial cell function and arteriolar smooth muscle contraction
What is the most significant factor causing primary hypertension?
increased total peripheral resistance caused by reduced arteriolar radius
Environmental risk factors of primary hypertension?
Obesity, insulin resistance, chronic high salt intake, elevations in plasma Na+ levels, smoking, excessive alcohol consumption, chronic stress
Causes of secondary hypertension? + treatments
damage to kidneys or their blood supply = renal hypertension (increased renin = increased angiotensin II + aldosterone = insufficient urine secretion + Na+ retention = increased extracellular fluid vol) (treatments: diuretics or low-sodium diet)
What is heart failure?
collection of signs + symptoms that occur when the heart does not pump an adequate cardiac output
Some causes of heart failure:
chronically increased arterial pressure (hypertension), structural damage to the myocardium due to decreased coronary blood flow
2 categories of heart failure:
those with diastolic dysfunction, those with systolic dysfunction
What occurs in diastolic dysfunction?
the wall of the ventricle has
reduced compliance.
This abnormal stiffness = reduced ability to fill adequately at normal diastolic filling pressures = reduced end-diastolic volume = reduced stroke volume
ventricular compliance decreased but ventricular contractility is normal
What causes the decreased ventricular compliance in diastolic dysfunction in heart failure?
systemic hypertension (hypertrophy = ventricle stiffens)
What occurs in systolic dysfunction?
Results from myocardial damage
Decrease in cardiac contractility (a lower stroke volume at any given
end-diastolic volume) = decrease in ejection fraction + a downward shift of the ventricular-function curve.
Affected ventricle does not hypertrophy, but end-diastolic volume increases.
What happens when there is reduced cardiac output of heart failure?
triggers arterial baroreceptor reflexes
baroreceptors discharge less rapidly than normal = brain interprets this decreased discharge as a larger-than-usual decrease in pressure
What are the results of the baroreceptor reflexes triggered in heart failure?
- heart rate increased via increased sympathetic activation of heart + decreased parasympathetic
- total peripheral resistance increased via increased sympathetic activation of systemic arterioles + via increased plasma conc of angiotensin II + ADH (vasoconstrictors)
initially beneficial in restoring cardiac output + arterial pressure
Effects of chronically maintained baroreceptor reflexes during period of heart failure?
- fluid retention = expansion of extracellular fluid vol = increases venous pressure, venous return, and E-DV vol = restores SV toward normal
because reflex causes kidneys to reduce their excretion of sodium + water
What issues start to arise as fluid retention progresses in the baroreceptor reflex?
- ventricle with systolic dysfunction becomes distended with blood + its force of contraction decreases = worsening heart failure state
- as it increases venous pressure = edema (accumulation of interstitial fluid) = swelling of feet and legs
- increase in total peripheral resistance = makes failing heart work harder
What are the effects and causes of (heart) failure of the left ventricle which leads to pulmonary edema (accumulation of fluid in interstitial space or in air spaces)?
(another issue of reflex)
impairs pulmonary gas exchange
cause: left ventricle fails to pump blood to the same extent as the right ventricle = vol of blood in all the pulmonary vessels increases.
engorgement of pulmonary capillaries increases capillary pressure above its normally very low value = filtration occurs faster than the lymphatics can remove
the fluid
Which side of the heart is the aurical located on?
the ventral side
What collects all the blood from the heart muscle itself?
The coronary sinus
What are the 3 openings of the right atrium?
inferior / superior vena cava + coronary sinus
Order of blood flow from lungs?
Pulmonary veins > left atrium > bicuspid valve > left ventricle
Order of blood flow from right atrium?
tricuspid valve > right ventricle > pulmonary valve > pulmonary trunk > lungs
Is it worse to have an infarction to the left or right side of the heart?
Left side infarction has worst outcome than right since muscle in middle is more left-belonging
When does excess blood flow into the coronary arteries?
Not all blood will make it past the aortic arch: some blood goes back (but valves are blocking opening) so the blood pools in the cusp of the valves and flows into coronary arteries
Which part of embryotic development does the heart arise from?
Intermediate mesoderm
How are nutrients and metabolic end products transported?
move between capillary blood and interstitial fluid via diffusion
Systemic circulation:
blood pumped from left ventricle through all organs and tissues of the body and then to the right atrium
Pulmonary circulation:
blood pumped from right ventricle through the lungs and then into the left atrium
Which vessels carry blood away from the heart?
arteries
Which vessels carry blood from organs and tissue back to the heart?
veins
Microcirculation:
arterioles > capillaries > venules
Determinants of resistance:
viscosity, length + radius of tube
What is the heart enclosed by?
pericardium (sac) + epicardium (fibrous layer)
What is the Inner surface of chambers + inner wall of blood vessels called?
endothelium
What separates the ventricles?
interventricular septum
AV valves:
right (tricuspid valve) + left (bicuspid valve/mitral valve)
To prevent AV valves opening backwards:
they are fastened to papillary muscles by chordae tendinae
Semilunar valves:
Pulmonary valve (right ventricle into pulmonary trunk) + aortic valve (left ventricle into aorta)
Which cells form part of cardiac muscle? + what do they do
Cardiac muscle cells: A.P, Ca2+ enters cytosol, force-generating cross-bridges
Specialized non-contractile cells: initiate cardiac A.P + regulate their spread through the heart
Cardiac innervation:
sympathetic (postganglionic fibers innervate entire heart + release norepinephrine) + parasympathetic nerve fibers (contained in the vagus nerves) (terminate on special cells in the atria + release primarily acetylcholine)
What characteristic allows A.P conduction from cell to cell in the heart?
Myocardial cells are joined by gap junctions
Where does initial depolarization (trigger for contraction) arise?
in the SA node (located in the right atrium near superior vena cava)
What is the travel route for the A.P?
SA node > throughout atria > into ventricles
Which factor of the excitation determines the heart rate?
Discharge rate of the SA node
What links atrial depolarization and ventricular depolarization?
AV node (base of right atrium)
What happens when the AV node has been excited?
A.P propagates down the interventricular septum (this pathway has a conducting-system of fibers called the AV bundle/bundle of His)
What characteristic allows the ventricles to contract almost simulatneously?
Rapid conduction along purkinje fibers