Cardiovascular System Flashcards
Layout
- pathways, capillary beds, system
- RV -> Pulmonary artery -> lungs (deoxy)
- LV -> aorta -> tissue (oxy)
- Capillary beds arranged mainly in parallel
- Portal system
Hepatic system as an example
- Each capillary bed receives arterial blood from LV
2. Flow to different capillary beds altered selectively, determined by resistance
Cross-sectional area is greatest at
Capillary level
How do arteries respond to pressure?
Dampen pressure variations by pulsatile action
Largest proportional pressure drop in
Arterioles -> max resistance to flow
MABP =
Diastolic pressure + 1/3 Pulse pressure
PP =
(systolic - diastolic) pressures
1kpa = X mmHg = Y cmH2O
7.5, 10.2
Q =
V x a ( velocity x cross-sec area)
Systemic pressure =
deltaP = MABP - Right arterial pressure
Pulmonary pressure
deltaP = MpABP - LAP
Resistance =
delta P/ Q (flow)
Poiseuile’s Law
Q = deltaP / R = deltaPxpix r* / 8nl
where n = viscosity and l = length of vessel
nrel1 =
water
nrel3 =
blood
Ht of plasma
nrel = 1.5
Factors which affect viscosity
- Ht
- Hypoxia - main factor
- Sickle cell
P wave represents
Atrial dep.
QRS complex represents
Vein dep.
T wave represents
Vein rep.
ECG timings
- P-R: 0.12-0.2 s
- QRS: 0.08s
- QT: 0.25-0.4s
Why does ST have no net flow?
Isoelectric region
Outline stages of the cardiac cycle
- At beginning ventricular contractionm mital valve closes until a.p. = v.p.
- At beg. relaxation, atrial valve closes + v.p. falls to = a.p.
- Heart sounds at beg. + end of v. contraction
- Vein changes to mirror atrium changes
Cardiac output =
S.V. x H.R.
Factors that affect cardiac output
- H.R.
- Mycocardial contractility
- Preload
- Afterload
Starling’s law
- Input to heart + output from ventricle =
2. Output of RV + LV are equal
+ve _____ effect when sympathetic stimulation increases _______
Ionotropic, cardiac
Kidney’s role in arterial b.p.
Reabsorption of NA+ to decrease preload
Where are baroreceptors located?
Peripherally located in neck -> at division of common carotid artery into external/ internal branches
In barareceptor reflex : mean a.p. - RAP =
Co x total peripheral R
Afferent :
Carotid sinus > sinus nerve > glossopharyngeal nerve
Efferent:
ANS -> SAN, myocardium, vascular smooth muscle
Renin-angiotensin system
Regulation of aldosterone increase by adrenal cortex + atria release ANP -> natriuresis (secretion of sodium in urine)
Intrinsic regulation of blood flow through tissues
Increase blood flow regulated by vasodilatery effect -> route of waste product generation
Extrinsic regulation of blood flow through tissues
- N/S hormones
- NA (p-G NT) acts on alpha receptors on vascular sm. -> vasoc.
- Alpha regulated beds have reduced blood flow when body attempts to restore b.p. by increasing total peripheral R so blood redirected to vital oragns
- Some capillary beds
- A/NA -> +ve ionotropic effect (cardiac contraction) , +ve chronotropic (tachycardia)
- Autoregulation in cerebral + renal circulations
Cerebral circulation
- Dual arterial input : posteriar com. arteries -> carotid and basilar arteries
- uR: around 20% resting O2 conc, RQ around 1.0
- Autoregulation : 60-200mmHg
- > principally regulated by local CO2 gas tensions
Coronary circulation
- O2 extraction by myocardial tissue is efficient
- Symp. stimulation to increase coronary blood flow
- Flow during systole is low : after ventricular relaxation
Cutaneous circulation
- Nutrient blood to tissues, extrinsic vascular control -> temp reg. + protection
- Orterio-venous anastamosus to increase autoneus blood flow
What is the triple response to trauma?
- Red - capillary dilation
- Wheal - Capillary becomes more permeable to proteins
- Flare -> dilation of local blood vessels to local sensory fibres branched nearby
Preload
Volume of blood in ventricles at end of diastole
Afterload
Resistance left ventricle must overcome to circulate blood
