Wk 4 pt2 Flashcards
(25 cards)
what is the distole and systole phase
heart fills passively due to pressure gradient from great veins
heart actively contracts and blood flows into arteries
What is end diastolic volume (EDV)
volume of blood in ventricle at the end of diastole– max vol. of blood in the ventricle
what is end systolic volume (ESV)
the volume of blood remaining at the end of systole in ventricle
what is stroke volume and ejection fraction in ref to sympathetic activation
SV is amount of blood ejected from ventricle during systole
= EDV-ESV
EF is percentrage of blood pumped out ventricle =SV/EDV
sympathetic activation increases cardiac contractility and SV increases so EF increases
what are the five mechanical events in the cardiac cycle
- late ventricular diastole
- isovolumetric contraction
- ventricular ejection
- isovolumetric relaxation
- ventricular filling
what happens in late ventricular diastole
SA node depolarises and wave of depolarisation sweeps over atria- contraction
what happens in isovolumetric contraction
ventricular pressure rises, atrioventricular valve closes
aortic valve opens when ventricular pressure exceeds aortic pressure
what happens in ventricular ejection
ventricular pressure falls and aortic valve closes due to ejection
What happens during isovolumetric relaxation
begins when aortic valve closes and all valves are closed
ventricular pressure falls- aortic pressure falling less rapidly than ventricular pressure
what happens in ventricular filling
passive flow of blood goes into left atrium
what is the course of venous return
increase venous return
increase end-diastolic ventricular volume
increase force of ventricular contraction
increase SV
Inc CO
what are the factors influencing venous return
skeletal muscle pump;
respiratory pump;
venous compliance;
blood volume; increased blood volume increases venous return and vise versa
what does skeletal muscle pump
skeletal muscle pump; muscle contration squeezes veins and pushes blood back to the heart and prevent backflow
what does the respiratory pump do
respiratory pump; thoracic pressure decreases and blood is pulled to the heart during inhalation
what does venous compliance do
venous compliance; veins expand/contract based on blood volume and sympathetic tone. lower compliance increase venous return and vise versa
what is the relationship of flow and resistance
pressure= flow x resistance
what is poiseuille’s law
resistance to blood flow depends on 3 factors
R= 8nL/πr^4
r= radius of vessel
n= viscosity of blood
L= length of bessel
local factors causing ateriolar dilation
increase muscle metabolic activity
increase consump. O2 and production of CO2 and other metabolites
decrease local O2 conc and inc CO2 and meabolite in interstitial fluid
relaxation of smooth muscle for vasodialation of arteriorles
increase local blood flow
inc rate of supply of O2 and removal of CO2
O2 and Co2 levels return to normal
what are the extrinsic factors in the autonomic nervous system
has 2 divisions- sympathetic and parasympathetic
heart is controlled by both
blood vessels are controlled by sympathetic
few parasympathetic vasodilator nerves in salivary glands, erectile tissue
extrinsic factors of vasoactive hormones adrenaline and noradrenaline
adenaline (Ad) and noradrenaline (Nad) released from adrenal medulla
released from sympathetic stimulation
acts on a and b adrenergic receptors
- Nad on a due to peripheral vasoconstriction
- Ad on B receptors due to vasodilation mostly skeletal muscle
extrinsic factors of vasoactive hormones vasopressin
an antidiuretic hormone produced in hypothalamus and stored in pituitary gland.
response to low blood volume
can vasoconstrict too
extrinsic factors of vasoactive hormones angiotensin ii
produced from plasma protein angiotensinogen to low blood volume/pressure
- is a vasoconstrictor
extrinsic factors of vasoactive hormones histamine
vasodilator and inc capillary permeability
- causes flare and wheal in local allergic reactions
MAP formula
MAP = CO X TPR
tpr= total peripheral resistance
